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  • Antifungal azoles itraconazole and posaconazole exhibit potent in vitro antiviral activity against clinical isolates of parechovirus A3 (Picornaviridae) ☆ ☆☆
    Antivir. Res. (IF 4.271) Pub Date : 2017-11-15
    Eric Rhoden, W. Allan Nix, William C. Weldon, Rangaraj Selvarangan

    Parechovirus A3 (Par-A3, formerly human parechovirus 3) is an emerging viral infection of the central nervous system in children. We used an automated, homogeneous, cell based assay to identify itraconazole and posaconazole as inhibitors of Par-A3, with antiviral activity below concentrations clinically attainable in pediatric patients. Currently, there is no approved antiviral treatment for Par-A3 infection, despite numerous reports of serious Par-A3 disease in neonates and infants.

  • A new promising candidate to overcome drug resistant herpes simplex virus infections
    Antivir. Res. (IF 4.271) Pub Date : 2017-11-15
    Elisabeth Zinser, Adalbert Krawczyk, Petra Mühl-Zürbes, Ulrich Aufderhorst, Lena Stich, Mirko Zaja, Stefan Strobl, Alexander Steinkasserer, Christiane Silke Heilingloh

    Infections with Herpes simplex viruses (HSV) belong to the most common human diseases worldwide, resulting in symptoms ranging from painful, but commonly self-limiting lesions of the orofacial or genital tract to severe infections of the eye or life-threatening generalized infections. Frequent HSV-reactivations at the eye may lead to the development of herpetic stromal keratitis, which is one of the major causes of infectious blindness in developed countries. The vast majority of life-threatening generalized infections occur in immunocompromised individuals, such as transplant recipients or patients suffering from advanced human immunodeficiency virus (HIV) infection with concurrent HSV-reactivation. Over the past decades, Acyclovir (ACV) became the golden standard for the treatment of HSV infections. However, long-term antiviral treatment, as it is required mainly in immunocompromised patients, led to the emergence of resistances towards ACV and other antivirals. Therefore, there is a clear need for the development of new potent antivirals which combine good oral bioavailability and tolerability with low side effects. In the current study we present SC93305 as a novel potent antiviral substance that proved to be highly effective not only against different HSV-1 and HSV-2 strains but also towards ACV- and multi-resistant HSV-1 and HSV-2 isolates. SC93305 shows comparable antiviral activity as reported for ACV and very importantly it does not interfere with the activation of specific immune cells. Here we report that SC93305 does not affect the biological function of dendritic cells (DC), the most potent antigen presenting cells of the immune system to induce antiviral immune responses, nor T cell stimulation or the release of inflammatory cytokines. Thus, SC93305 is a new and promising candidate for the treatment of HSV-1 and HSV-2 infections and in particular also for the inhibition of drug-resistant HSV-1/2 strains.

  • Rational design of antiviral drug combinations based on equipotency using HCV subgenomic replicon as an in vitro model
    Antivir. Res. (IF 4.271) Pub Date : 2017-11-14
    Mohamed Mandour, Inge Vliegen, Jan Paeshuyse, Johan Neyts

    Combination therapy of directly acting antivirals (DAA's) for the treatment of chronic HCV infections has proven to be a highly effective strategy to cure chronic infections with this virus. Here we studied, using HCV as an example, how to best design in vitro studies that explore the combined antiviral efficiency of combinations of three or more DAA's. To that end we used a HCV NS3 protease inhibitor, a NS5A targeting compound and two non-nucleoside NS5B polymerase inhibitors (each one targeting a different drug binding site). We demonstrate, employing HCV subgenomic replicon containing Huh 9–13 hepatoma cells, that quadruple therapy with these 4 different DAA's each at 1x their EC75, results in a highly efficient inhibition of viral replication. This is further reflected in the rapid clearance of the HCV replicon from the host cell. By contrast, neither equipotent combinations that consist of either molecules alone at 4x EC75 nor triple combinations at 1.33x the EC75 resulted in clearance. In contrast to the quadruple combo, drug-resistant variants emerged under mono-treatment and in most triple combo's. These data thus demonstrate that quadruple combinations at total suboptimal concentrations [i.e. concentrations at which neither mono- nor triple therapy is sufficiently potent] result rapidly in a pronounced antiviral efficacy. Altogether, this work provides an example as to how to design studies to explore the antiviral efficacy of combinations of more than two compounds.

  • Interferon lambda (IFN-λ) efficiently blocks norovirus transmission in a mouse model
    Antivir. Res. (IF 4.271) Pub Date : 2017-11-10
    Joana Rocha-Pereira, Sophie Jacobs, Sam Noppen, Eric Verbeken, Thomas Michiels, Johan Neyts

    Human noroviruses are highly efficient in person to person transmission thus associated with explosive outbreaks of acute gastroenteritis. Outbreak control is limited to disinfection and isolation measures. Strategies to control the spread of noroviruses should be developed and models to study norovirus transmission will greatly facilitate this. Here, a mouse-to-mouse transmission model, in which mice develop acute murine norovirus (MNV)-induced diarrhea, was used to explore the role of interferon lambda (IFN-λ) in the control of a norovirus infection. Sentinel AG129 mice [deficient in IFN-α/β and IFN-γ receptors] that were co-housed with MNV-infected mice shedding high amounts of virus in their stool, developed a MNV-infection with associated diarrhea. Inoculation of such sentinel mice with an IFN-λ expression plasmid resulted in the production of circulating IFN-λ and upregulation of the expression of IFN-stimulated genes (ISGs) of the gut. Injection of the IFN-λ-expressing plasmid to sentinels prevents MNV-induced disease upon exposure to MNV-infected mice, as well as MNV replication in the small intestine, the associated signs of inflammation and the mounting of a specific IgG-based immune response. This demonstrates that IFN-λ can alone mediate protection against transmission of norovirus. The development of a simple delivery method for IFN-λ could be explored as a strategy to control norovirus outbreaks and protect vulnerable populations such as the elderly and immunocompromised.

  • HBsAg mRNA degradation induced by dihydroquinolizinone molecule depends on HBV posttranscriptional regulatory element
    Antivir. Res. (IF 4.271) Pub Date : 2017-11-10
    Tianlun Zhou, Timothy Block, Fei Liu, Andrew S. Kondratowicz, Liren Sun, Siddhartha Rawat, Jeffrey Branson, Fang Guo, Hongyan Liang, Lauren Bailey, Chris Moore, Xiaohe Wang, Andy Cuconatti, Min Gao, Amy C.H. Lee, Troy Harasym, Tim Chiu, Dimitar Gotchev, Bruce Dorsey, Rene Rijnbrand, Michael J. Sofia

    In pursuit of novel therapeutics targeting the hepatitis B virus (HBV) infection, we evaluated a dihydroquinolizinone compound (DHQ-1) that possessed nanomolar activities against the production of virion and surface protein (HBsAg) in tissue culture. This compound also showed broad HBV genotype coverage and was inactive against a panel of DNA and RNA viruses of other species. Oral administration of DHQ-1 in the AAV-HBV mouse model resulted in a strong reduction of serum HBsAg as soon as 4 days following the commencement of treatment. Reduction of HBV marks in both in vitro and in vivo experiments was related to the down regulation of viral RNA including pre-genomic RNA (pgRNA) and 2.4/2.1Kb HBsAg mRNA. Nuclear run on and subcellular fractionation experiments indicated that DHQ-1 mediated HBV RNA reduction was the result of accelerated viral RNA degradation in the nucleus, rather than the consequence of inhibition of transcription initiation. Through mutagenesis analysis of HBsAg gene, we found induction of HBsAg mRNA decay by DHQ-1 required the presence of the HBV post transcriptional regulatory element (HPRE), with a 109 nucleotides sequence within the central region of the HPRE alpha sub-element, being the most critical. Taken together, the current study shows that a small molecule can reduce the overall levels of HBV RNA especially, the HBsAg mRNA and as such viral surface proteins, which may shed light on the development of a new class of HBV therapeutics.

  • A virus-like particle of the hepatitis B virus preS antigen elicits robust neutralizing antibody and T cell responses in mice
    Antivir. Res. (IF 4.271) Pub Date : 2017-11-10
    Xiaodan Cai, Weihao Zheng, Shaokun Pan, Shengyuan Zhang, Youhua Xie, Haitao Guo, Guoxin Wang, Zigang Li, Ming Luo

    The preS antigen of hepatitis B virus (HBV) corresponds to the N-terminal polypeptide in the large (L) antigen in addition to the small (S) antigen. The virus-like particle (VLP) of the S antigen is widely used as a vaccine to protect the population from HBV infection. The presence of the S antigen and its antibodies in patient blood has been used as markers to monitor hepatitis B. However, there is very limited knowledge about the preS antigen. We generated a preS VLP that is formed by a chimeric protein between preS and hemagglutinin (HA), and the matrix protein M1 of influenza virus. The HBV preS antigen is displayed on the surface of preS VLP. Asn112 and Ser98 of preS in VLP were found to be glycosylated and O-glycosylation of Ser98 has not been reported previously. The preS VLP shows a significantly higher immunogenicity than recombinant preS, eliciting robust anti-preS neutralizing antibodies. In addition, preS VLP is also capable of stimulating preS-specific CD8+ and CD4+ T cell responses in Balb/c mice and HBV transgenic mice. Furthermore, preS VLP immunization provided protection against hydrodynamic transfection of HBV DNA in mice. The data clearly suggest that this novel preS VLP could elicit robust immune responses to the HBV antigen, and can be potentially developed into prophylactic and therapeutic vaccines.

  • APOBEC3B edits HBV DNA and inhibits HBV replication during reverse transcription
    Antivir. Res. (IF 4.271) Pub Date : 2017-11-10
    Yanmeng Chen, Jie Hu, Xuefei Cai, Yao Huang, Xing Zhou, Zeng Tu, Jieli Hu, John E. Tavis, Ni Tang, Ailong Huang, Yuan Hu

    Hepatitis B virus is a partially double-stranded DNA virus that replicates by reverse transcription, which occurs within viral core particles in the cytoplasm. The cytidine deaminase APOBEC3B is a cellular restriction factor for HBV. Recently, it was reported that APOBEC3B can edit HBV cccDNA in the nucleus, causing its degradation. However, whether and how it can edit HBV core-associated DNAs during reverse transcription is unclear. Our studies to address this question revealed the following: First, silencing endogenous APOBEC3B in an HBV infection system lead to upregulation of HBV replication. Second, APOBEC3B can inhibit replication of HBV isolates from genotypes (gt) A, B, C, and D as determined by employing transfection of plasmids expressing isolates from four different HBV genotypes. For HBV inhibition, APOBEC3B-mediated inhibition of replication primarily depends on the C-terminal active site of APOBEC3B. In addition, employing the HBV RNaseH-deficient D702A mutant and a polymerase-deficient YMHA mutant, we demonstrated that APOBEC3B can edit both the HBV minus- and plus-strand DNAs, but not the pregenomic RNA in core particles. Furthermore, we found by co-immunoprecipitation assays that APOBEC3B can interact with HBV core protein in an RNA-dependent manner. Our results provide evidence that APOBEC3B can interact with HBV core protein and edit HBV DNAs during reverse transcription. These data suggest that APOBEC3B exerts multifaceted antiviral effects against HBV.

  • Design, synthesis, and biological evaluation of novel 7-deazapurine nucleoside derivatives as potential anti-dengue virus agents
    Antivir. Res. (IF 4.271) Pub Date : 2017-11-10
    Cai Lin, Jianchen Yu, Muzammal Hussain, Yiqian Zhou, Anna Duan, Weiqi Pan, Jie Yuan, Jiancun Zhang

    Dengue fever, caused by four distinct serotypes of dengue virus (DENV-1 to -4), has become the fastest spreading human infectious disease in recent years. Despite extensive efforts, there is no specific antiviral treatment approved for dengue until now. Nucleoside inhibitors represent an actively pursued area to develop small-molecule anti-dengue virus agents. In this study, we designed and synthesized a series of 7-deazapurine nucleoside derivatives and evaluated their anti-DENV activity. Our design strategy and structure activity relationship studies revealed 6e as the most potent inhibitor (EC50 = 2.081 ± 1.102 μM) of DENV replication. 6e suppressed RNA levels and DENV E protein expression, without causing any apparent cytotoxicity in A549 and HepG2 cells (CC50 = 150.06 ± 11.42 μM, SI = 72.11 in A549 cells, and CC50 = 146.47 ± 11.05 μM and SI = 63.7 in HepG2 cells). In addition, 6e showed similar inhibition potency against four serotypes of DENV, suggesting that it restrains some evolutionarily conserved targets essential for DENV replication. We conceive that 6e may serve as a promising lead compound for anti-DENV drug development.

  • Efficacy of hepatitis B virus ribonuclease H inhibitors, a new class of replication antagonists, in FRG human liver chimeric mice
    Antivir. Res. (IF 4.271) Pub Date : 2017-11-10
    Kelly R. Long, Elena Lomonosova, Qilan Li, Nathan L. Ponzar, Juan A. Villa, Erin Touchette, Stephen Rapp, R. Matt Liley, Ryan P. Murelli, Alexandre Grigoryan, R. Mark Buller, Lisa Wilson, John Bial, John E. Sagartz, John E. Tavis

    Chronic hepatitis B virus infection cannot be cured by current therapies, so new treatments are urgently needed. We recently identified novel inhibitors of the hepatitis B virus ribonuclease H that suppress viral replication in cell culture. Here, we employed immunodeficient FRG KO mice whose livers had been engrafted with primary human hepatocytes to ask whether ribonuclease H inhibitors can suppress hepatitis B virus replication in vivo. Humanized FRG KO mice infected with hepatitis B virus were treated for two weeks with the ribonuclease H inhibitors #110, an α-hydroxytropolone, and #208, an N-hydroxypyridinedione. Hepatitis B virus viral titers and S and e antigen plasma levels were measured. Treatment with #110 and #208 caused significant reductions in plasma viremia without affecting hepatitis B virus S or e antigen levels, and viral titers rebounded following treatment cessation. This is the expected pattern for inhibitors of viral DNA synthesis. Compound #208 suppressed viral titers of both hepatitis B virus genotype A and C isolates. These data indicate that Hepatitis B virus replication can be suppressed during infection in an animal by inhibiting the viral ribonuclease H, validating the ribonuclease H as a novel target for antiviral drug development.

  • Nsp3 of coronaviruses: Structures and functions of a large multi-domain protein
    Antivir. Res. (IF 4.271) Pub Date : 2017-11-08
    Jian Lei, Yuri Kusov, Rolf Hilgenfeld

    The multi-domain non-structural protein 3 (Nsp3) is the largest protein encoded by the coronavirus (CoV) genome, with an average molecular mass of about 200 kD. Nsp3 is an essential component of the replication/transcription complex. It comprises various domains, the organization of which differs between CoV genera, due to duplication or absence of some domains. However, eight domains of Nsp3 exist in all known CoVs: the ubiquitin-like domain 1 (Ubl1), the Glu-rich acidic domain (also called “hypervariable region”), a macrodomain (also named “X domain”), the ubiquitin-like domain 2 (Ubl2), the papain-like protease 2 (PL2pro), the Nsp3 ectodomain (3Ecto, also called “zinc finger domain”), as well as the domains Y1 and CoV-Y of unknown functions. In addition, the two transmembrane regions, TM1 and TM2, exist in all CoVs. The three-dimensional structures of domains in the N-terminal two thirds of Nsp3 have been investigated by X-ray crystallography and/or nuclear magnetic resonance (NMR) spectroscopy since the outbreaks of Severe Acute Respiratory Syndrome coronavirus (SARS-CoV) in 2003 as well as Middle-East Respiratory Syndrome coronavirus (MERS-CoV) in 2012. In this review, the structures and functions of these domains of Nsp3 are discussed in depth. This article is part of the series “From SARS to MERS: Research on highly pathogenic human coronaviruses” (Hilgenfeld & Peiris, Antiviral Res. 100, 286–295 (2013)).

  • Activity of nucleic acid polymers in rodent models of HBV infection
    Antivir. Res. (IF 4.271) Pub Date : 2017-11-08
    Katrin Schöneweis, Neil Motter, Pia L. Roppert, Mengji Lu, Baoju Wang, Ingo Roehl, Dieter Glebe, Dongliang Yang, John D. Morrey, Michael Roggendorf, Andrew Vaillant

    Nucleic acid polymers (NAPs) block the release of HBsAg from infected hepatocytes. These compounds have been previously shown to have the unique ability to eliminate serum surface antigen in DHBV-infected Pekin ducks and achieve multilog reduction of HBsAg or HBsAg loss in patients with chronic HBV infection and HBV/HDV coinfection. In ducks and humans, the blockage of HBsAg release by NAPs occurs by the selective targeting of the assembly and/or secretion of subviral particles (SVPs).The clinically active NAP species REP 2055 and REP 2139 were investigated in other relevant animal models of HBV infection including woodchucks chronically infected with WHV, HBV transgenic mice and HBV infected SCID-Hu mice. The liver accumulation of REP 2139 in woodchucks following subcutaneous administration was examined and was found to be similar to that observed in mice and ducks. However, in woodchucks, NAP treatment was associated with only mild (36–79% relative to baseline) reductions in WHsAg (4/10 animals) after 3–5 weeks of treatment without changes in serum WHV DNA. In HBV infected SCID-Hu mice, REP 2055 treatment was not associated with any reduction of HBsAg, HBeAg or HBV DNA in the serum after 28 days of treatment. In HBV transgenic mice, no reductions in serum HBsAg were observed with REP 2139 with up to 12 weeks of treatment.In conclusion, the antiviral effects of NAPs in DHBV infected ducks and patients with chronic HBV infection were weak or absent in woodchuck and mouse models despite similar liver accumulation of NAPs in all these species, suggesting that the mechanisms of SVP assembly and or secretion present in rodent models differs from that in DHBV and chronic HBV infections.

  • Merimepodib, an IMPDH inhibitor, suppresses replication of Zika virus and other emerging viral pathogens
    Antivir. Res. (IF 4.271) Pub Date : 2017-11-08
    Xiao Tong, Jeanon Smith, Natalya Bukreyeva, Takaaki Koma, Tyler J. Manning, Raj Kalkeri, Ann D. Kwong, Slobodan Paessler

    Zika virus (ZIKV), a member of the Flaviviridae family, has recently been linked to abnormal pregnancies, fetal death, microcephaly, and Guillain-Barré syndrome in humans. Merimepodib (MMPD, VX-497), a potent inhibitor of inosine-5′-monophosphate dehydrogenase (IMPDH), has shown antiviral activity against HCV and a variety of DNA and RNA viruses in vitro. In this report, we expand the antiviral spectrum of MMPD, and demonstrate that MMPD inhibits ZIKV RNA replication with an EC50 of 0.6 μM. In a virus production assay, MMPD reduces the virus titer of ZIKV as well as several other important emerging viral pathogens such as Ebola, Lassa, Chikungunya, and Junin viruses. The inhibition can be reversed by addition of exogenous guanosine to culture media, consistent with the mechanism of action of MMPD as an IMPDH inhibitor. We also provide evidence that MMPD can be used in combination with other antivirals such as ribavirin and T-705 (favipiravir) to enhance suppression of virus production.

  • Infection of neuroblastoma cells by rabies virus is modulated by the virus titer
    Antivir. Res. (IF 4.271) Pub Date : 2017-11-06
    Natalia Langenfeld Fuoco, Sandriana Dos Ramos Silva, Elaine Raniero Fernandes, Fernanda Guedes Luiz, Orlando Garcia Ribeiro, Iana Suly Santos Katz

    Rabies is a lethal viral infection that can affect almost all mammals, including humans. To better understand the replication of Rabies lyssavirus, we investigated if the viral load in brains naturally infected with rabies influences viral internalization and viral growth kinetics in neuroblastoma cells, and if the viral load affects mortality in mice after intradermal infection. We noted that high initial viral loads in brains (group II) were unfavourable for increasing viral titers during serial passages in neuroblastoma cells when compared to low initial viral loads in brains (group I). In addition, group I strains showed higher viral growth and enhanced internalization efficiency in neuroblastoma cells than group II strains. However, we observed that the dominant virus subpopulation in group II promoted efficient viral infection in the central nervous system in the new host, providing a selective advantage to the virus. Our data indicate that rabies infection in animal models depends on not only the virus strain but also the amount of virus. This study may serve as a basis for understanding the biologic proprieties of Rabies lyssavirus strains with respect to the effects on viral replication and the impact on pathogenesis, improving virus yields for use in vaccine development.

  • Efficacy of pritelivir and acyclovir in the treatment of herpes simplex virus infections in a mouse model of herpes simplex encephalitis
    Antivir. Res. (IF 4.271) Pub Date : 2017-11-04
    Debra C. Quenelle, Alexander Birkmann, Thomas Goldner, Tamara Pfaff, Holger Zimmermann, Susanne Bonsmann, Deborah J. Collins, Terri L. Rice, Mark N. Prichard

    Pritelivir, a helicase-primase inhibitor, has excellent in vitro and in vivo activity against human herpes simplex virus (HSV). Mice lethally infected with HSV type 1 or 2, including acyclovir-resistant strains, were treated 72 h after infection for 7 days with pritelivir or acyclovir. Both drugs were administered orally twice daily either alone or in combination. Dosages of pritelivir from 0.3 to 30 mg/kg reduced mortality (P < 0.001) against HSV-1, E-377. With an acyclovir resistant HSV-1, 11360, pritelivir at 1 and 3 mg/kg increased survival (P < 0.005). With HSV-2, MS infected mice, all dosages higher than the 0.3 mg/kg dose of pritelivir were effective (P < 0.005). For acyclovir resistant HSV-2, strain 12247, pritelivir dosages of 1–3 mg/kg significantly improved survival (P < 0.0001). Combination therapies of pritelivir at 0.1 or 0.3 mg/kg/dose with acyclovir (10 mg/kg/dose) were protective (P < 0.0001) when compared to the vehicle treated group against HSV-2, strain MS (in line with previous data using HSV-1). An increased mean days to death (P < 0.05) was also observed and was indicative of a potential synergy. Pharmacokinetic studies were performed to determine pritelivir concentrations and a dose dependent relationship was found in both plasma and brain samples regardless of infection status or time of initiation of dosing. In summary, pritelivir was shown to be active when treatment was delayed to 72 h post viral inoculation and appeared to synergistically inhibit mortality in this model in combination with acyclovir. We conclude pritelivir has potent and resistance-breaking antiviral efficacy with potential for the treatment of potentially life-threatening HSV type 1 and 2 infections, including herpes simplex encephalitis.

  • The role of the NLRP3 inflammasome in regulation of antiviral responses to influ|ԌE|Ԍ
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-31
    Soroush T. Sarvestani, Julie L. McAuley

    The innate immune system provides the host with both a dynamic barrier to prevent infection and a means to which rapid anti-microbial responses can be mounted. The inflammasome pathway is a critical host early response mechanism that enables detection of pathogens and initiates production of inflammatory cytokines, inducing recruitment of effector cells to the site of infection. The complete mechanism of inflammasome activation requires two signals: an initial priming step upon detection of pathogen, followed by activation of intracellular pattern recognition receptors critical to the formation of the inflammasome complex. The inflammasome complex is made of intracellular multiprotein oligomers which includes a sensor protein such as the nucleotide-binding oligomerization domain (NOD) like receptor proteins (NLRP), and an adapter protein, ASC, which critically activates pro-caspase-1. The mature caspase-1 then proteolytically cleaves cytosolic pro-IL-1β and pro-IL-18, which are then secreted as inflammatory cytokines that activate the inflammatory arm of the immune response to infection. Active caspase-1 also results in pyroptosis, which is a form of cell death triggered by inflammation. The induction and activation of IL-1β and IL-18 are considered critical signatures for inflammasome activation. With focus upon influenza A virus infection, this review will address present knowledge on the mechanisms of inflammasome complex activation, particularly how the viral components modulate activation of the cytosolic NOD-like receptor protein-3 (NLRP3)-dependent inflammasome complex. We also discuss potential therapeutic strategies that target the inflammasome to ameliorate illness, as well as novel methods of vaccination that target inflammasome stimulation with the aim to increase efficacy.

  • A pharmacologically immunosuppressed mouse model for assessing influenza B virus pathogenicity and oseltamivir treatment
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-31
    Bindumadhav M. Marathe, Heba H. Mostafa, Peter Vogel, Philippe Noriel Q. Pascua, Jeremy C. Jones, Charles J. Russell, Richard J. Webby, Elena A. Govorkova

    Immunocompromised patients are highly susceptible to influenza virus infections. Although neuraminidase inhibitor (NAI) therapy has proved effective in these patients, the treatment regimens require optimization, which can be partly addressed via animal models. Here, we describe a pharmacologically immunosuppressed mouse model for studying the pathogenesis of influenza B viruses and evaluating the efficacy of antiviral treatment. We modeled clinical regimens for dexamethasone and cyclophosphamide to immunosuppress BALB/c mice that were then inoculated with B/Phuket/3073/2013 (Yamagata lineage) or B/Brisbane/60/2008 (BR/08, Victoria lineage) virus. Although both viruses caused morbidity and mortality in immunosuppressed mice, BR/08 was more virulent, consistently inducing greater morbidity and 100% lethality in mice inoculated with at least 103 TCID50/mouse. The replication of both viruses was prolonged in the lungs of immunosuppressed mice, but the extent of pulmonary inflammation in these mice was markedly less than that in immunocompetent animals. Most of the examined cytokines, including IFN-γ, IL-1β, and RANTES, were significantly decreased in the lungs of immunosuppressed mice, as compared to immunocompetent animals, until at least 10 days post-infection. Treatment with the NAI oseltamivir for 8 or 16 days increased the mean survival time and reduced virus spread in the lungs of immunosuppressed mice challenged with a lethal dose of BR/08 but did not completely provide protection or decrease the virus titers. Our data suggests that the synergy of the viral load and aberrant immune responses is a key contributor to the severity of infection, as well as the limited efficacy of oseltamivir, which in immunosuppressed mice curtails virus release without clearing infected cells.

  • A third component of the human cytomegalovirus terminase complex is involved in letermovir resistance
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-28
    Sunwen Chou

    Letermovir is a human cytomegalovirus (CMV) terminase inhibitor that was clinically effective in a Phase III prevention trial. In vitro studies have shown that viral mutations conferring letermovir resistance map primarily to the UL56 component of the terminase complex and uncommonly to UL89. After serial culture of a baseline CMV laboratory strain under letermovir, mutation was observed in a third terminase component in 2 experiments, both resulting in amino acid substitution P91S in gene UL51 and adding to a pre-existing UL56 mutation. Recombinant phenotyping indicated that P91S alone conferred 2.1-fold increased letermovir resistance (EC50) over baseline, and when combined with UL56 mutation S229F or R369M, multiplied the level of resistance conferred by those mutations by 3.5–7.7-fold. Similarly a combination of UL56 mutations S229F, L254F and L257I selected in the same experiment conferred 54-fold increased letermovir EC50 over baseline, but 290-fold when combined with UL51 P91S. The P91S mutant was not perceptibly growth impaired. Although pUL51 is essential for normal function of the terminase complex, its biological significance is not well understood. Letermovir resistance mutations mapping to 3 separate genes, and their multiplier effect on the level of resistance, suggest that the terminase components interactively contribute to the structure of a letermovir antiviral target. The diagnostic importance of the UL51 P91S mutation arises from its potential to augment the letermovir resistance of some UL56 mutations at low fitness cost.

  • Immunogenicity and efficacy of replication-competent recombinant influenza virus carrying multimeric M2 extracellular domains in a chimeric hemagglutinin conjugate
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-26
    Min-Chul Kim, Yu-Na Lee, Yu-Jin Kim, Hyo-Jick Choi, Ki-Hye Kim, Youn-Jeong Lee, Sang-Moo Kang

    Current influenza vaccines provide hemagglutinin (HA) strain-specific protection. To improve cross protection, we engineered replication-competent influenza A virus to express tandem repeats of heterologous M2 extracellular (M2e) domains in a chimeric HA. M2e epitopes conjugated to HA glycoproteins (M2e4x-HA) were found to be expressed on the surfaces of a replicable influenza virus as examined by electron microscopy. The recombinant influenza virus containing M2e4x-HA was moderately attenuated but superior to the parental virus in inducing M2e specific antibodies without compromising HA immunogenicity. Recombinant influenza virus immune mice showed better cross protection than parental virus immune mice. Immune sera from the mice with inoculation of live recombinant influenza virus expressing M2e4x-HA were effective in conferring protection against H1, H3, and H5 subtype influenza viruses. This study indicates that recombinant influenza virus expressing conserved protective epitopes in an HA chimeric form can provide a new approach for improving the efficacy of influenza vaccines.

  • A novel neutralizing human monoclonal antibody broadly abrogates hepatitis C virus infection in vitro and in vivo
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-23
    Isabelle Desombere, Ahmed Atef Mesalam, Richard A. Urbanowicz, Freya Van Houtte, Lieven Verhoye, Zhen-Yong Keck, Ali Farhoudi, Koen Vercauteren, Karin E. Weening, Thomas F. Baumert, Arvind H. Patel, Steven K.H. Foung, Jonathan Ball, Geert Leroux-Roels, Philip Meuleman

    Infections with hepatitis C virus (HCV) represent a worldwide health burden and a prophylactic vaccine is still not available. Liver transplantation (LT) is often the only option for patients with HCV-induced end-stage liver disease. However, immediately after transplantation, the liver graft becomes infected by circulating virus, resulting in accelerated progression of liver disease. Although the efficacy of HCV treatment using direct-acting antivirals has improved significantly, immune compromised LT-patients and patients with advanced liver disease remain difficult to treat. As an alternative approach, interfering with viral entry could prevent infection of the donor liver. We generated a human monoclonal antibody (mAb), designated 2A5, which targets the HCV envelope. The neutralizing activity of mAb 2A5 was assessed using multiple prototype and patient-derived HCV pseudoparticles (HCVpp), cell culture produced HCV (HCVcc), and a human-liver chimeric mouse model. Neutralization levels observed for mAb 2A5 were generally high and mostly superior to those obtained with AP33, a well-characterized HCV-neutralizing monoclonal antibody. Using humanized mice, complete protection was observed after genotype 1a and 4a HCV challenge, while only partial protection was achieved using gt1b and 6a isolates. Epitope mapping revealed that mAb 2A5 binding is conformation-dependent and identified the E2-region spanning amino acids 434 to 446 (epitope II) as the predominant contact domain. Conclusion: mAb 2A5 shows potent anti-HCV neutralizing activity both in vitro and in vivo and could hence represent a valuable candidate to prevent HCV recurrence in LT-patients. In addition, the detailed identification of the neutralizing epitope can be applied for the design of prophylactic HCV vaccines.

  • Avasimibe: A novel hepatitis C virus inhibitor that targets the assembly of infectious viral particles
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-23
    Longbo Hu, Jinqian Li, Hua Cai, Wenxia Yao, Jing Xiao, Yi-Ping Li, Xiu Qiu, Huimin Xia, Tao Peng

    Direct-acting antivirals (DAAs), which target hepatitis C virus (HCV) proteins, have exhibited impressive efficacy in the management of chronic hepatitis C. However, the concerns regarding high costs, drug resistance mutations and subsequent unexpected side effects still call for the development of host-targeting agents (HTAs) that target host factors involved in the viral life cycle and exhibit pan-genotypic antiviral activity. Given the close relationship between lipid metabolism and the HCV life cycle, we investigated the anti-HCV activity of a series of lipid-lowering drugs that have been approved by government administrations or proven safety in clinical trials. Our results showed that avasimibe, an inhibitor of acyl coenzyme A:cholesterol acyltransferase (ACAT), exhibited marked pan-genotypic inhibitory activity and superior inhibition against HCV when combined with DAAs. Moreover, avasimibe significantly impaired the assembly of infectious HCV virions. Mechanistic studies demonstrated that avasimibe induced downregulation of microsomal triglyceride transfer protein expression, resulting in reduced apolipoprotein E and apolipoprotein B secretion. Therefore, the pan-genotypic antiviral activity and clinically proven safety endow avasimibe exceptional potential as a candidate for combination therapy with DAAs. In addition, the discovery of the antiviral properties of ACAT inhibitors also suggests that inhibiting the synthesis of cholesteryl esters might be an additional target for the therapeutic intervention for chronic HCV infection.

  • Characterization of a dengue NS4B inhibitor originating from an HCV small molecule library
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-14
    Ilane Hernandez-Morales, Peggy Geluykens, Marleen Clynhens, Rudy Strijbos, Olivia Goethals, Sarah Megens, Nick Verheyen, Stefaan Last, David McGowan, Erwin Coesemans, Benoît De Boeck, Bart Stoops, Benoit Devogelaere, Frederik Pauwels, Koen Vandyck, Jan Martin Berke, Pierre Raboisson, Kenneth Simmen, Pedro Lory, Marnix Van Loock

    Dengue is the most important mosquito-transmitted viral disease and a major global health concern. Over the last decade, dengue virus (DENV) drug discovery and development has intensified, however, this has not resulted in approved DENV-specific antiviral treatments yet. DENV and hepatitis C virus (HCV) belong to the same Flaviviridae family and, in contrast to DENV, antiviral treatments for HCV have been licensed. Therefore, applying the knowledge gained on anti-HCV drugs may foster the discovery and development of dengue antiviral drugs. Here, we screened a library of compounds with established anti-HCV activity in a DENV-2 sub-genomic replicon inhibition assay and selected compounds with single-digit micromolar activity. These compounds were advanced into a hit-to-lead medicinal chemistry program resulting in lead compound JNJ-1A, which inhibited the DENV-2 sub-genomic replicon at 0.7 μM, in the absence of cytotoxicity. In addition, JNJ-1A showed equipotent antiviral activity against DENV serotypes 1, 2, and 4. In vitro resistance selection experiments with JNJ-1A induced mutation T108I in non-structural protein 4B (NS4B), pointing towards a mechanism of action linked to this protein. Collectively, we described the discovery and characterization of a novel DENV inhibitor potentially targeting NS4B.

  • Divalent copper complexes as influenza A M2 inhibitors
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-12
    Nathan A. Gordon, Kelly L. McGuire, Spencer K. Wallentine, Gregory A. Mohl, Jonathan D. Lynch, Roger G. Harrison, David D. Busath
  • Structure-based drug design for envelope protein E2 uncovers a new class of bovine viral diarrhea inhibitors that block virus entry
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-12
    María José Pascual, Fernando Merwaiss, Emilse Leal, María Eugenia Quintana, Alejandra V. Capozzo, Claudio N. Cavasotto, Mariela Bollini, Diego E. Alvarez

    Antiviral targeting of virus envelope proteins is an effective strategy for therapeutic intervention of viral infections. Here, we took a computer-guided approach with the aim of identifying new antivirals against the envelope protein E2 of bovine viral diarrhea virus (BVDV). BVDV is an enveloped virus with an RNA genome responsible for major economic losses of the cattle industry worldwide. Based on the crystal structure of the envelope protein E2, we defined a binding site at the interface of the two most distal domains from the virus membrane and pursued a hierarchical docking-based virtual screening search to identify small-molecule ligands of E2. Phenyl thiophene carboxamide derivative 12 (PTC12) emerged as a specific inhibitor of BVDV replication from in vitro antiviral activity screening of candidate molecules, displaying an IC50 of 0.30 μM against the reference NADL strain of the virus. Using reverse genetics we constructed a recombinant BVDV expressing GFP that served as a sensitive reporter for the study of the mechanism of action of antiviral compounds. Time of drug addition assays showed that PTC12 inhibited an early step of infection. The mechanism of action was further dissected to find that the compound specifically acted at the internalization step of virus entry. Interestingly, we demonstrated that similar to PTC12, the benzimidazole derivative 03 (BI03) selected in the virtual screen also inhibited internalization of BVDV. Furthermore, docking analysis of PTC12 and BI03 into the binding site revealed common interactions with amino acid residues in E2 suggesting that both compounds could share the same molecular target. In conclusion, starting from a targeted design strategy of antivirals against E2 we identified PTC12 as a potent inhibitor of BVDV entry. The compound can be valuable in the design of antiviral strategies in combination with already well-characterized polymerase inhibitors of BVDV.

  • Protective effect of an alpha 7 nicotinic acetylcholine receptor agonist against enterovirus 71 infection in neuronal cells
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-10
    FengXia Song, LinQin Zhao, RuNan Zhu, QinWei Song, Jie Deng, Run Tian, Fang Wang, Yuan Qian

    Enterovirus 71, as one of the dominant pathogens associated with severe hand, foot, and mouth disease, has been well reported to trigger severe neurological symptoms among young children over the last decade, particularly among children in the Asia-Pacific region. To date, no effective antiviral agent has been developed for the treatment of severe enterovirus 71 infection. PNU-282987, a selective alpha 7 nicotinic acetylcholine receptor (α7nAChR) agonist, has been reported to have a neuroprotective effect by participating in inflammatory regulation in previous studies. Therefore, in the present study, we aimed to assess the cell-protective effect of PNU-282987 against enterovirus 71 infection in neuronal cells, and to discuss potential mechanisms underlying this cell-protective effect in order to elucidate the potential impact of such agonists in the treatment of neurotropic viral infection. We observed that treatment with PNU-282987 improved cell viability and inhibited viral replication in enterovirus 71-infected SH-SY5Y cells. Further investigation revealed that inhibition of enterovirus 71production by PNU-282987 is likely associated with events of RNA replication, and that increased levels of INF mRNA and its downstream antiviral proteins stimulated by the JAK-STAT2 pathway may contribute to the antiviral effect of PNU-282987. Moreover, our findings suggest that both the antiviral and anti-inflammatory effects of PNU-282987 may contribute to the neural protective effect of the drug in enterovirus 71-infected cells. Taken together, the results suggest that selective α7nAChR agonists may represent viable candidates for future therapeutic treatment of severe enterovirus 71infection, and for other cases of neurotropic viral infection.

  • Identification of 2′-deoxy-2′-fluorocytidine as a potent inhibitor of Crimean-Congo hemorrhagic fever virus replication using a recombinant fluorescent reporter virus
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-09
    Stephen R. Welch, Florine E.M. Scholte, Mike Flint, Payel Chatterjee, Stuart T. Nichol, Éric Bergeron, Christina F. Spiropoulou

    Crimean-Congo hemorrhagic fever virus (CCHFV), a tick-borne orthonairovirus, causes a severe hemorrhagic disease in humans (Crimean-Congo hemorrhagic fever, CCHF). Currently, no vaccines are approved to prevent CCHF; treatment is limited to supportive care and the use of ribavirin, the therapeutic benefits of which remain unclear. CCHF is part of WHO's priority list of infectious diseases warranting further research and development. To aid in the identification of new antiviral compounds, we generated a recombinant CCHFV expressing a reporter protein, allowing us to quantify virus inhibition by measuring the reduction in fluorescence in infected cells treated with candidate compounds. The screening assay was readily adaptable to high-throughput screening (HTS) of compounds using Huh7 cells, with a signal-to-noise ratio of 50:1, and Z′-factors > 0.6 in both 96- and 384-well formats. A screen of candidate nucleoside analog compounds identified 2′-deoxy-2′-fluorocytidine (EC50 = 61 ± 18 nM) as having 200 × the potency of ribavirin (EC50 = 12.5 ± 2.6 μM), as well as 17 × the potency of T-705 (favipiravir), another compound with reported anti-CCHFV activity (EC50 = 1.03 ± 0.16 μM). Furthermore, we also determined that 2′-deoxy-2′-fluorocytidine acts synergistically with T-705 to inhibit CCHFV replication without causing cytotoxicity. The incorporation of this reporter virus into the high-throughput screening assay described here will allow more rapid identification of effective therapeutic options to combat this emerging human pathogen.

  • Modulation of proteolytic polyprotein processing by coxsackievirus mutants resistant to inhibitors targeting phosphatidylinositol-4-kinase IIIβ or oxysterol binding protein
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-09
    Heyrhyoung Lyoo, Cristina M. Dorobantu, Hilde M. van der Schaar, Frank J.M. van Kuppeveld

    Enteroviruses (e.g. poliovirus, coxsackievirus, and rhinovirus) require several host factors for genome replication. Among these host factors are phosphatidylinositol-4-kinase IIIβ (PI4KB) and oxysterol binding protein (OSBP). Enterovirus mutants resistant to inhibitors of PI4KB and OSBP were previously isolated, which demonstrated a role of single substitutions in the non-structural 3A protein in conferring resistance. Besides the 3A substitutions (i.e., 3A-I54F and 3A-H57Y) in coxsackievirus B3 (CVB3), substitution N2D in 2C was identified in each of the PI4KB-inhibitor resistant CVB3 pools, but its possible benefit has not been investigated yet. In this study, we set out to investigate the possible role of 2C-N2D in the resistance to PI4KB and OSBP inhibition. We show that 2C-N2D by itself did not confer any resistance to inhibitors of PI4KB and OSBP. However, the double mutant (i.e., 2C-N2D/3A-H57Y) showed better replication than the 3A-H57Y single mutant in the presence of inhibitors. Growing evidence suggests that alterations in lipid homeostasis affect the proteolytic processing of the poliovirus polyprotein. Therefore, we studied the effect of PI4KB or OSBP inhibition on proteolytic processing of the CVB3 polyprotein during infection as well as in a replication-independent system. We show that both PI4KB and OSBP inhibitors specifically affected the cleavage at the 3A-3B junction, and that mutation 3A-H57Y recovered impaired proteolytic processing at this junction. Although 2C-N2D enhanced replication of the 3A-H57Y single mutant, we did not detect additional effects of this substitution on polyprotein processing, which leaves the mechanism of how 2C-N2D contributes to the resistance to be revealed.

  • New class of early-stage enterovirus inhibitors with a novel mechanism of action
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-07
    Yipeng Ma, Rana Abdelnabi, Leen Delang, Mathy Froeyen, Walter Luyten, Johan Neyts, Carmen Mirabelli

    4-dimethylamino benzoic acid (compound 12, synonym: 4EDMAB) was identified as an in vitro inhibitor of Coxsackie virus B3 (CVB3) replication in CPE-based assays (EC50 of 9.1 ± 1.5 μM). Next, the activity of twenty-three analogues was assessed, their structure-activity relationship was deduced and a more potent analogue was identified (EC50 of 2.6 ± 0.5 μM). The antiviral activity of 4EDMAB was further confirmed by quantifying viral RNA yield. Time-of-drug-addition assay revealed that 4EDMAB exerts its antiviral activity at the early stages of virus replication. Six compound-resistant viruses were selected and genotyped and all the mutations appeared to be in the capsid protein VP1. Reverse engineering showed that single mutants Y75C, A88V, A98V, D133N and R219K were respectively 15-, 2-, 4-, 17- and 76-fold resistant to 4EDMAB. The compound protected both wild type (WT) CVB3 and the five resistant mutants from heat inactivation. The plaque size produced by the A88V, D133N and R219K mutants was smaller than that of WT and these mutants were also more heat-sensitive than WT in the absence of the compound. These findings suggest that these three mutations increase virion capsid flexibility and compensate for the stabilizing effect of 4EDMAB. Molecular modelling suggests that the compound binds to a small cavity in VP1, which is different from the hydrophobic pocket in the canyon where typical capsid binders (such as pleconaril) bind. Modelling studies also suggest a direct ionic interaction between the negatively charged carboxylic group of 4EDMAB and the positively charged guanidino group of arginine 219. Moreover, the in vitro combination of 4EDMAB and pleconaril resulted in synergistic antiviral effect. In conclusion, 4EDMAB is a novel early-stage inhibitor, which targets VP1 with a mechanism that is different from that of known capsid binders.

  • Targeted inhibition of Hantavirus replication and intracranial pathogenesis by a chimeric protein-delivered siRNA
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-07
    Jie Yang, Ji-Feng Sun, Ting-Ting Wang, Xiao-Hong Guo, Jun-Xia Wei, Lin-Tao Jia, An-Gang Yang

    Hantavirus (HV) infection, which underlies hantavirus hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome, remains to be a severe clinical challenge. Here, we synthesized small interfering RNAs (siRNAs) that target the encoding sequences of HV strain 76-118, and validated their inhibitory role in virus replication in HV-infected monkey kidney Vero E6 cells. A chimeric protein, 3G1-Cκ-tP, consisting of a single-chain antibody fragment (3G1) against the HV surface envelop glycoprotein, the constant region of human immunoglobulin κ chain (Cκ), and truncated protamine (amino acids 8–29, tP), was further generated. The fusion protein showed high affinity to HV antigen on the infected cell membrane, and internalized through clathrin-mediated endocytosis; it bound to siRNAs via the basic nucleic acid-rich protamine fragment, leading to their specific delivery into HV-infected cells and efficient inhibition of virus replication. An encephalitis mouse model was established via intracranial HV administration. Intraperitoneal injection of siRNAs complexed with 3G1-Cκ-tP achieved specific distribution of siRNAs in HV-infected brain cells, significantly reduced HV antigen levels, and effective protection from HV infection-derived animal death. These results provide a compelling rationale for novel therapeutic protocols designed for HV infection and related disorders.

  • Altered expression of interferon-stimulated genes is strongly associated with therapeutic outcomes in hepatitis B virus infection
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-06
    Meifang Han, Yong Li, Wenyu Wu, Yuanya Zhang, Weiming Yan, Xiaoping Luo, Qin Ning

    Our previous OSST study shows that switching to pegylated interferon (Peg-IFN)-α2a results in higher rates of response hepatitis B e antigen (HBeAg) seroconversion and hepatitis B surface antigen (HBsAg) loss at the end of treatment, compared with nucleot(s)ide analogues (NAs) monotherapy in long term NA-treated chronic hepatitis B (CHB) patients. In order to characterize the correlation between Peg-IFN-α antiviral effect and IFN-inducing signaling in CHB patients who switched to Peg-IFN from long time entecavir (ETV) treatment, we investigated the dynamic expression of interferon-stimulated genes (ISGs), including STAT1, MX, and a negative regulatory factor, suppressor of cytokine signaling 3(SOCS3), which negatively regulate IFN JAK-STAT signaling pathway by interacting with STAT1 and STAT2, in peripheral blood and paired liver samples, obtained from 54 CHB patients enrolled in a clinical trial, OSST study. In Peg-IFN group, responders showed a more significant decline in HBsAg, compared with non-responders. Following the treatment, peripheral blood and hepatic STAT1 and MX expression levels were higher in Peg-IFN responders, while SOCS3 expression was higher in non-responders. Fold induction of STAT1 at week 4 and MX at week 12 in PBMCs directly correlated with HBsAg decline at week 48 relative to the baseline. Responders showed a significantly increased activation and nuclear localization of phospho-STAT1 following Peg-IFN treatment, compared with non-responders in liver. Whereas, non-responders exhibited significantly higher hepatic expression of SOCS3 before the treatment compared with the responders and even higher expression levels after the treatment compared with the baseline, which may be involved in the mechanism of IFN resistance.

  • The susceptibility of circulating human influenza viruses to tizoxanide, the active metabolite of nitazoxanide
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-03
    Danielle Tilmanis, Carel van Baalen, Ding Yuan Oh, Jean-Francois Rossignol, Aeron C. Hurt

    Nitazoxanide is a thiazolide compound that was originally developed as an anti-parasitic agent, but has recently been repurposed for the treatment of influenza virus infections. Thought to exert its anti-influenza activity via the inhibition of hemagglutinin maturation and intracellular trafficking in infected cells, the effectiveness of nitazoxanide in treating patients with non-complicated influenza is currently being assessed in phase III clinical trials.Here, we describe the susceptibility of 210 seasonal influenza viruses to tizoxanide, the active circulating metabolite of nitazoxanide. An optimised cell culture-based focus reduction assay was used to determine the susceptibility of A(H1N1)pdm09, A(H3N2), and influenza B viruses circulating in the southern hemisphere from the period March 2014 to August 2016. Tizoxanide showed potent in vitro antiviral activity against all influenza viruses tested, including neuraminidase inhibitor-resistant viruses, allowing the establishment of a baseline level of susceptibility for each subtype. Median EC50 values (±IQR) of 0.48 μM (0.33–0.71), 0.62 μM (0.56–0.75), 0.66 μM (0.62–0.69), and 0.60 μM (0.51–0.67) were obtained for A(H1N1)pdm09, A(H3N2), B(Victoria lineage), and B(Yamagata lineage) influenza viruses respectively. There was no significant difference in the median baseline tizoxanide susceptibility for each influenza subtype tested. This is the first report on the susceptibility of circulating viruses to tizoxanide. The focus reduction assay format described is sensitive, robust, and less laborious than traditional cell based antiviral assays, making it highly suitable for the surveillance of tizoxanide susceptibility in circulating seasonal influenza viruses.

  • A cell-based high throughput screening assay for the discovery of cGAS-STING pathway agonists
    Antivir. Res. (IF 4.271) Pub Date : 2017-10-02
    Bowei Liu, Liudi Tang, Xiaohui Zhang, Julia Ma, Mohit Sehgal, Junjun Cheng, Xuexiang Zhang, Yan Zhou, Yanming Du, John Kulp, Ju-Tao Guo, Jinhong Chang

    Stimulator of interferon genes (STING) is an endoplasmic reticulum transmembrane protein that serves as a molecular hub for activation of interferon and inflammatory cytokine response by multiple cellular DNA sensors. Not surprisingly, STING has been demonstrated to play an important role in host defense against microorganisms and pharmacologic activation of STING is considered as an attractive strategy to treat viral diseases and boost antitumor immunity. In light of this we established a HepAD38-derived reporter cell line that expresses firefly luciferase in response to the activation of cyclic GMP-AMP synthase (cGAS)-STING pathway for high throughput screening (HTS) of small molecular human STING agonists. This cell-based reporter assay required only 4 h treatment with a reference STING agonist to induce a robust luciferase signal and was demonstrated to have an excellent performance in HTS format. By screening 16,000 compounds, a dispiro diketopiperzine (DSDP) compound was identified to induce proinflammatory cytokine response in a manner dependent on the expression of functional human STING, but not mouse STING. Moreover, we showed that DSDP induced an interferon-dominant cytokine response in human skin fibroblasts and peripheral blood mononuclear cells, which in turn potently suppressed the replication of yellow fever virus, dengue virus and Zika virus. We have thus established a robust cell-based assay system suitable for rapid discovery and mechanistic analyses of cGAS-STING pathway agonists. Identification of DSDP as a human STING agonist enriches the pipelines of STING-targeting drug development for treatment of viral infections and cancers.

  • Inhibition of rubella virus replication by the broad-spectrum drug nitazoxanide in cell culture and in a patient with a primary immune deficiency
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-30
    Ludmila Perelygina, Timo Hautala, Mikko Seppänen, Adebola Adebayo, Kathleen E. Sullivan, Joseph Icenogle

    Persistent rubella virus (RV) infection has been associated with various pathologies such as congenital rubella syndrome, Fuchs's uveitis, and cutaneous granulomas in patients with primary immune deficiencies (PID). Currently there are no drugs to treat RV infections. Nitazoxanide (NTZ) is an FDA-approved drug for parasitic infections, and has been recently shown to have broad-spectrum antiviral activities. Here we found that empiric 2-month therapy with oral NTZ was associated in the decline/elimination of RV antigen from lesions in a PID patient with RV positive granulomas, while peginterferon treatment had no effect. In addition, we characterized the effects of NTZ on cell culture models of persistent RV infection. NTZ significantly inhibited RV replication in a primary culture of human umbilical vein endothelial cells (HUVEC) and Vero and A549 epithelial cell lines in a dose dependent manner with an average 50% inhibitory concentration of 0.35 μg/ml (1.1 μM). RV strains representing currently circulating genotypes were inhibited to a similar extent. NTZ affected early and late stages of infection by inhibiting synthesis of cellular and RV RNA and interfering with intracellular trafficking of the RV surface glycoproteins, E1 and E2. These results suggest a potential application of NTZ for the treatment of persistent rubella infections, but more studies are required.

  • Immunoprotection induced by CpG-ODN/Poly(I:C) combined with recombinant gp90 protein in chickens against reticuloendotheliosis virus infection
    Antivir. Res. (IF 4.271) Pub Date : 2017-04-29
    Fei Yuan, Ying Chu, Lihong Qi, Hongmei Li, Shuhong Sun, Peng Zhao, Shuang Chang, Huijun Guo

    The present study is focused on investigating the immunoprotective effects of CpG-ODN/Poly(I:C) combined with the viral glycoprotein gp90 protein against reticuloendotheliosis virus (REV) infection in chickens. REV's gp90 gene was amplified from the REV-infected cells and expressed in Escherichia coli (E.coli). The expressed products, upon purification, were inoculated into 7-day-old chickens with PBS, CpG-ODN or Poly(I:C) adjuvant; Two booster inoculations were then conducted, and then each chicken was challenged. The presence of REV-antibodies in serum was determined weekly after the first vaccination. The viremia and immunosuppressive effects of REV infection were also monitored after the challenge. The neutralizing effects of the antisera were tested in vitro. The results showed that the recombinant gene containing REV gp90 gene was expressed into the recombinant protein with a size of 51 Kilo Dalton (KD), which could be recognized by a monoclonal antibody (MAb) against the gp90 protein. The viremia and immunosuppressive effects of avian influenza virus (AIV) vaccine caused by REV challenge in CpG-ODN group and in Poly(I:C) group were dramatically decreased. REV antibody with low titers was induced in gp90 group and the inoculated chickens were partly protected. Compared with those in gp90 group, the titers and the positive ratios of REV antibody in CpG+gp90 group were significantly increased, whereas the viremia and immunosuppressive effects of AIV vaccine caused by REV infection were significantly decreased. In the Poly(I:C) +gp90 group, the viremia and immunosuppressive effects caused by REV infection were also dramatically decreased, although REV antibody responses were softly increased. The diluted antisera from the vaccinated chickens in both groups could completely inhibit the replication of REV in chick fibroblast cells (CEF). Hence, it can be concluded that CpG-ODN or the Poly(I:C) adjuvant can enhance the antiviral effects of the REV subunit vaccine against REV infection, which may result from different mechanisms.

  • Recombinant hemagglutinin proteins formulated in a novel PELC/CpG adjuvant for H7N9 subunit vaccine development
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-22
    Ting-Hsuan Chen, Ying-Yu Liu, Jia-Tsrong Jan, Ming-Hsi Huang, Maureen Spearman, Michael Butler, Suh-Chin Wu

    Humans infected with H7N9 avian influenza viruses can result in severe pneumonia and acute respiratory syndrome with an approximately 40% mortality rate, and there is an urgent need to develop an effective vaccine to reduce its pandemic potential. In this study, we used a novel PELC/CpG adjuvant for recombinant H7HA (rH7HA) subunit vaccine development. After immunizing BALB/c mice intramuscularly, rH7HA proteins formulated in this adjuvant instead of an alum adjuvant elicited higher IgG, hemagglutination-inhibition, and virus neutralizing antibodies in sera; induced higher numbers of H7HA-specific IFN-γ-secreting T cells and antibody secreting cells in spleen; and provided improved protection against live virus challenges. Our results indicate that rH7HA proteins formulated in PELC/CpG adjuvant can induce potent anti-H7N9 immunity that may provide useful information for H7N9 subunit vaccine development.

  • Interplay between dengue virus and Toll-like receptors, RIG-I/MDA5 and microRNAs: Implications for pathogenesis
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-28
    Silvio Urcuqui-Inchima, Jesús Cabrera, Anne-Lise Haenni

    A growing body of evidence has demonstrated the role of components of innate immunity, including Toll-like receptors (TLRs), the retinoic acid-inducible gene I/melanoma-differentiation factor 5 (RIG-I/MDA5) and microRNAs (miRNAs) in the recognition of dengue virus (DENV) or its components by infected cells. TLR3, TLR7/8 and RIG-I/MDA5 sense genomic RNA or dsRNA, the product of an intermediate step of DENV replication, activating intracellular pathways leading to the production of antiviral effectors, including interferon and pro-inflammatory cytokines. Recognition by TLR2 and TLR4 also promotes the activation of other intracellular pathways and alters viral replication in an interferon-independent manner. It was also recently demonstrated that cellular miRNAs, a class of post-transcriptional regulatory small RNAs, can affect replication. To accomplish this, miRNAs bind either directly to viral RNA, through base-pair complementarity affecting translation, or indirectly through virus-mediated changes in host protein expression in the viral life cycle. There is also evidence that certain miRNAs can recognize or be recognized by TLRs and RIG-I/MDA5, resulting in alteration of the innate immune response. In this review, we summarize our present knowledge of DENV-host factor interactions, emphasizing the role of TLRs, RIG-I/MDA5 and miRNAs and their possible connection with pathogenesis. Our discussion is based on recent reports suggesting how these different innate immune components might be activated to induce an antiviral response, and how DENV has developed mechanisms to manipulate or evade these antiviral activities.

  • Inhibition of human cytomegalovirus replication by tricin is associated with depressed CCL2 expression
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-28
    Yumiko Akai, Hidetaka Sadanari, Masaya Takemoto, Noboru Uchide, Tohru Daikoku, Naofumi Mukaida, Tsugiya Murayama

    We previously reported that treatment with tricin (4′,5,7-trihydroxy-3′,5′-dimethoxyflavone) after human cytomegalovirus (HCMV) infection significantly suppressed both infectious virion production and HCMV replication in human embryonic lung fibroblast (HEL) cells. Moreover, we recently demonstrated that HCMV infection can increase the expression of CC-motif ligand 2 (CCL2/MCP-1) and of CCR2, a CCL2-specific receptor, effects that can in turn enhance HCMV infection and replication. Hence, we here examined whether the CCL2-CCR2 axis is involved in the anti-HCMV effects of tricin in HEL cells. Tricin exposure yielded dose-dependent decreases in the accumulation of transcripts for the HCMV immediate early gene and the DNA polymerase gene in HCMV-infected cells, along with decreased production of infectious HCMV. Concomitantly, tricin caused dose-dependent attenuation of HCMV infection-induced up-regulation of expression of CCL2 and CCR2 mRNAs and of CCL2 protein. Moreover, CCL2 reversed tricin-mediated inhibition of HCMV virion production in a dose-dependent manner. Thus, tricin appears to exert anti-HCMV activity by depressing CCL2 expression.

  • IFNA2 p.Ala120Thr impairs the inhibitory activity of Interferon-α2 against the hepatitis B virus through altering its binding to the receptor
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-25
    Chuming Chen, Xiang Zhu, Wenxiong Xu, Fangji Yang, Genglin Zhang, Lina Wu, Yongyuan Zheng, Zhiliang Gao, Chan Xie, Liang Peng

    Background Our previous study found that a rare genetic mutation IFNA2p.Ala120Thr affects the structure of IFN-α2 and contributes to increased host susceptibility to CHB. However, the way in which the single amino acid residue mutation affects IFN-α2 activity is unclear. The purpose of this research was to investigate the effects and mechanisms of IFNA2p.Ala120Thr on IFN-α2 activity. Methods Plasmid transfection of BL-21 was used to construct both wild type IFNA2 (wt) and p.Ala120Thr IFNA2 (mut) proteins. The HepG2-NTCP model was established using a lentiviral vector (LV003). Anti-HBV activity of wt and mut were tested on HepG2-NTCP infected cells with HBV, through the detection of HBsAg and HBcAg using immunohistochemistry and by detecting HBV DNA with RT PCR. IF and Co-IP were performed in order to investigate the binding of the IFNA2 protein and its receptor. The changes in IFNAR density and signal molecule phosphorylation were measured with western blotting. We used qPCR to further explore anti-HBV protein expression including APOBEC3, MxA, OAS1, and PKR. Results Cell model experiments confirmed that IFNA2p.Ala120Thr impairs anti-HBV activity of IFN-α2. Co-IP tests indicated that the binding of mut-IFNα to IFNR was weaker in the mut-treated group. IFNR density on the cells surface increased after treatment with wt-IFN-α2. Obvious differences in the STAT phosphorylation profiles were seen between the mut-treated and wt-treated groups. The expression of four main kinds of anti-HBV proteins induced by mut was higher in the HepG2-NTCP cells. Thus, IFNA2p.Ala120Thr affects anti-HBV activity of IFN-α2. Conclusion IFNA2p.Ala120Thr impairs the anti-HBV ability of IFN-a2, mainly by reducing its binding to the IFN receptor. Mut IFN-a2 has a very weak binding, barely inducing STAT phosphorylation, and induces the expression of only a low level of related anti-HBV ISG. This is quite different from the effects of wt IFN-a2, implying that modifying the key structural position of IFNa may lead to the modulation of targeted gene expression.

  • Antiviral treatment efficiently inhibits chikungunya virus infection in the joints of mice during the acute but not during the chronic phase of the infection
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-25
    Rana Abdelnabi, Dirk Jochmans, Erik Verbeken, Johan Neyts, Leen Delang

    Favipiravir (T-705) is a broad spectrum antiviral which has been approved in Japan for the treatment of severe influenza virus infections. We reported earlier that favipiravir inhibits the in vitro replication of CHIKV and protects against disease progression in CHIKV-infected immunodeficient mice. We here explored whether favipiravir is also able to inhibit CHIKV replication in the joints of mice either when treatment is initiated during the acute or during the chronic phase of the infection. To this end, C57BL/6J mice were infected with CHIKV in the left hind footpad and treatment with favipiravir (300 mg/kg/day, orally) was either given from day 0 to day 3 post-infection (p.i.) or from day 49 to day 55 p.i. In the untreated mice, viral RNA was still detectable in the joints up to 98 days p.i., yet no infectious viral particles were observed in these tissues. The 4 days treatment during the acute phase of the infection resulted in complete inhibition of systemic viral spread. As a consequence, no viral RNA was detected in the non-inoculated feet in contrast to the situation in the untreated control mice. When treatment was initiated at day 49 p.i., no significant reduction in viral RNA levels in joints were noted as compared to the untreated control. Interestingly, when attempting to amplify by RT-PCR material corresponding to virus genome from the chronic phase samples, some parts of the genome, such as the viral polymerase gene could not be amplified. Collectively, these results suggest that the viral RNA detected in the joints during the chronic phase is likely defective, which also explains the lack of effect of a viral replication inhibitor.

  • Immune efficacy of an adenoviral vector-based swine influenza vaccine against antigenically distinct H1N1 strains in mice
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-20
    Yunpu Wu, Dawei Yang, Bangfeng Xu, Wenhua Liang, Jinyu Sui, Yan Chen, Huanliang Yang, Hualan Chen, Ping Wei, Chuanling Qiao

    Avian-like H1N1 swine influenza viruses are prevalent in pigs and have occasionally crossed the species barrier and infected humans, which highlights the importance of preventing swine influenza. Human adenovirus serotype 5 (Ad5) has been tested in human influenza vaccine clinical trials and has exhibited a reliable safety profile. Here, we generated a replication-defective, recombinant adenovirus (designated as rAd5-avH1HA) expressing the hemagglutinin gene of an avian-like H1N1 virus (A/swine/Zhejiang/199/2013, ZJ/199/13). Using a BALB/c mouse model, we showed that a two-dose intramuscular administration of recombinant rAd5-avH1HA induced high levels of hemagglutination inhibition antibodies and prevented homologous H1N1 and heterologous H1N1 virus-induced weight loss, as well as viral replication in the nasal turbinates and lungs of mice. Furthermore, a prime–boost immunization strategy trial with a recombinant plasmid (designated as pCAGGS-HA) followed by rAd5-avH1HA vaccine provided effective protection against homologous and heterologous H1N1 virus infection in mice. These results indicate that rAd5-avH1HA is an efficacious genetically engineered vaccine candidate against H1N1 swine influenza. Future studies should examine its immune efficacy in pigs.

  • A novel candidate MS2 phage VLP vaccine displaying a tandem HPV L2 peptide offers similar protection in mice to Gardasil-9
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-20
    Lukai Zhai, Julianne Peabody, Yuk-Ying Susana Pang, John Schiller, Bryce Chackerian, Ebenezer Tumban

    Human papillomaviruses (HPVs) cause approximately 5% of cancer cases worldwide. Fortunately, three prophylactic vaccines have been approved to protect against HPV infections. Gardasil-9, the most recent HPV vaccine, is predicted to offer protection against the HPV types that cause ∼90% of cervical cancer, 86% of HPV-associated penile cancers, and ∼93% of HPV-associated head & neck cancers. As an alternative to Gardasil-9, we developed and tested a novel candidate vaccine targeting conserved epitopes in the HPV minor capsid protein, L2. We displayed a tandem HPV31/16L2 peptide (amino acid 17–31) or consensus peptides from HPV L2 (amino acid 69–86 or 108–122) on the surface of bacteriophage MS2 virus-like particles (VLPs). Mice immunized with the MS2 VLPs displaying the tandem peptide or immunized with a mixture of VLPs (displaying the tandem peptide and consensus peptide 69–86) elicited high titer antibodies against individual L2 epitopes. Moreover, vaccinated mice were protected from cervicovaginal infection with HPV pseudoviruses 16, 18, 31, 33, 45, and 58 at levels similar to mice immunized with Gardasil-9. These results suggest that immunization with a tandem, L2 peptide or a low valency mixture of L2 peptide-displaying VLPs can provide broad protection against multiple HPV types.

  • Recurrent herpetic keratitis despite antiviral prophylaxis: A virological and pharmacological study
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-20

    Recurrent herpes simplex keratitis (HSK) is a leading infectious cause of blindness in industrialized countries. Antiviral prophylaxis (AVP) may fail to prevent recurrence of HSK due to viral resistance, inadequate dosing, or poor patient compliance. In this prospective multicenter study, we enrolled immunocompetent patients with recurrent HSK despite AVP. Ocular samples were tested by PCR for herpes simplex virus 1 (HSV-1). HSV-1 drug resistance was assessed with a genotypic assay based on UL23 and UL30 gene sequencing. After curative full dose valacyclovir (VACV) treatment was started, peak and trough acyclovir (ACV) plasma concentrations were measured, and patient compliance to AVP was assessed with a questionnaire.The study sample was comprised of 43 patients. Six (14%) patients were positive for HSV-1 using PCR, of whom 5 (83%) harbored genotypically ACV-resistant (ACVR) virus, due to mutations in UL23 (n = 4) or UL30 (n = 1). Disease duration was statistically significantly longer in patients with viral resistance compared to other HSK patients [35.5 ± 23.4 years (range, 6.8–68.4 years) versus 11.1 ± 12.3 years (range, 0.8–56.3 year) respectively; Mann-Whitney p = 0.01)].While patients were treated with full dose VACV, trough ACV plasma concentrations were below the threshold for ACV sensitivity in 9.5% of cases, and compliance was poor in 5.3% of cases.To summarize, HSV-1 resistance to ACV seems to be a significant cause of failure of prophylaxis in patients with HSK and is associated with longer disease duration. Most PCR-positive samples contained genotypically ACVR virus and identification may aid in adapting treatment. Incomplete 24-h drug coverage may also explain some cases of failure of prophylaxis.

  • Celastrol inhibits hepatitis C virus replication by upregulating heme oxygenase-1 via the JNK MAPK/Nrf2 pathway in human hepatoma cells
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-19
    Chin-Kai Tseng, Sung-Po Hsu, Chun-Kuang Lin, Yu-Hsuan Wu, Jin-Ching Lee, Kung-Chia Young
  • Use of whole genome deep sequencing to define emerging minority variants in virus envelope genes in herpesvirus treated with novel antimicrobial K21
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-19
    Joshua G. Tweedy, Bhupesh K. Prusty, Ursula A. Gompels

    New antivirals are required to prevent rising antimicrobial resistance from replication inhibitors. The aim of this study was to analyse the range of emerging mutations in herpesvirus by whole genome deep sequencing. We tested human herpesvirus 6 treatment with novel antiviral K21, where evidence indicated distinct effects on virus envelope proteins. We treated BACmid cloned virus in order to analyse mechanisms and candidate targets for resistance. Illumina based next generation sequencing technology enabled analyses of mutations in 85 genes to depths of 10,000 per base detecting low prevalent minority variants (<1%). After four passages in tissue culture the untreated virus accumulated mutations in infected cells giving an emerging mixed population (45–73%) of non-synonymous SNPs in six genes including two envelope glycoproteins. Strikingly, treatment with K21 did not accumulate the passage mutations; instead a high frequency mutation was selected in envelope protein gQ2, part of the gH/gL complex essential for herpesvirus infection. This introduced a stop codon encoding a truncation mutation previously observed in increased virion production. There was reduced detection of the glycoprotein complex in infected cells. This supports a novel pathway for K21 targeting virion envelopes distinct from replication inhibition.

  • A pilot study to expand treatment of chronic hepatitis C in resource-limited settings
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-18
    Poonam Mathur, Emily Comstock, Edward McSweegan, Natalia Mercer, Nongthombam Suraj Kumar, Shyamasundaran Kottilil

    The past five years have seen a revolution in the treatment of chronic hepatitis C, as short duration oral regimens of direct-acting antiviral drugs (DAAs), with nearly 100% cure rates for all genotypes, have replaced longer courses of ribavirin and injected interferon. Although initially very expensive, these DAAs are now becoming available in generic equivalents in countries with large numbers of chronically infected people, such as India. However, a number of obstacles may hinder the delivery of these drugs in resource-limited settings, including lack of access to diagnostic testing and the restriction of treatment to a small number of medical specialists. New approaches are therefore needed to make DAAs available to the estimated 71 million infected people, many of whom disproportionately live in low- or middle-income countries. A recent pilot study (ASCEND) of hepatitis C management in a low-income population in Washington, D.C., demonstrated that trained nurse practitioners, primary care physicians and hepatologists were equally successful in diagnosing and treating patients, indicating that such an approach might be successful in resource-limited regions of the world. Members of the Global Virus Network have received funding to carry out a similar training project in a region of India with a high prevalence of hepatitis C. This paper reviews the challenges of delivering DAA therapy in low- and middle-income countries, describes plans for performing and evaluating the effectiveness of a training program in India, and discusses future needs for the eventual elimination of hepatitis C.

  • Pentagalloylglucose, a highly bioavailable polyphenolic compound present in Cortex moutan, efficiently blocks hepatitis C virus entry
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-18
    Patrick Behrendt, Paula Perin, Nicolas Menzel, Dominic Banda, Stephanie Pfaender, Marco P. Alves, Volker Thiel, Phillip Meulemann, Che C. Colpitts, Luis M. Schang, Florian W.R. Vondran, Anggakusuma, Michael P. Manns, Eike Steinmann, Thomas Pietschmann

    Approximately 142 million people worldwide are infected with hepatitis C virus (HCV). Although potent direct acting antivirals are available, high costs limit access to treatment. Chronic hepatitis C virus infection remains a major cause of orthotopic liver transplantation. Moreover, re-infection of the graft occurs regularly. Antivirals derived from natural sources might be an alternative and cost-effective option to complement therapy regimens for global control of hepatitis C virus infection.We tested the antiviral properties of a mixture of different Chinese herbs/roots named Zhi Bai Di Huang Wan (ZBDHW) and its individual components on HCV. One of the ZBDHW components, Penta-O-Galloyl-Glucose (PGG), was further analyzed for its mode of action in vitro, its antiviral activity in primary human hepatocytes as well as for its bioavailability and hepatotoxicity in mice.ZBDHW, its component Cortex Moutan and the compound PGG efficiently block entry of HCV of all major genotypes and also of the related flavivirus Zika virus. PGG does not disrupt HCV virion integrity and acts primarily during virus attachment. PGG shows an additive effect when combined with the well characterized HCV inhibitor Daclatasvir. Analysis of bioavailability in mice revealed plasma levels above tissue culture IC50 after a single intraperitoneal injection.In conclusion, PGG is a pangenotypic HCV entry inhibitor with high bioavailability. The low cost and wide availability of this compound make it a promising candidate for HCV combination therapies, and also emerging human pathogenic flaviviruses like ZIKV.

  • STD-NMR experiments identify a structural motif with novel second-site activity against West Nile virus NS2B-NS3 protease
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-18
    Tobias Schöne, Lena Lisbeth Grimm, Naoki Sakai, Linlin Zhang, Rolf Hilgenfeld, Thomas Peters

    West Nile virus (WNV) belongs to the genus Flavivirus of the family Flaviviridae. This mosquito-borne virus that is highly pathogenic to humans has been evolving into a global threat during the past two decades. Despite many efforts, neither antiviral drugs nor vaccines are available. The viral protease NS2B-NS3pro is essential for viral replication, and therefore it is considered a prime drug target. However, success in the development of specific NS2B-NS3pro inhibitors had been moderate so far. In the search for new structural motifs with binding affinity for NS2B-NS3pro, we have screened a fragment library, the Maybridge Ro5 library, employing saturation transfer difference (STD) NMR experiments as readout. About 30% of 429 fragments showed binding to NS2B-NS3pro. Subsequent STD-NMR competition experiments using the known active site fragment A as reporter ligand yielded 14 competitively binding fragments, and 22 fragments not competing with A. In a fluorophore-based protease assay, all of these fragments showed inhibition in the micromolar range. Interestingly, 10 of these 22 fragments showed a notable increase of STD intensities in the presence of compound A suggesting cooperative binding. The most promising non-competitive inhibitors 1 and 2 (IC50 ∼ 500 μM) share a structural motif that may guide the development of novel second-site (potentially allosteric) inhibitors of NS2B-NS3pro. To identify the matching protein binding site, chemical shift perturbation studies employing 1H,15N-TROSY-HSQC experiments with uniformly 2H,15N-labeled protease were performed in the presence of 1, and in the concomitant absence or presence of A. The data suggest that 1 interacts with Met 52* of NS2B, identifying a secondary site adjacent to the binding site of A. Therefore, our study paves the way for the synthesis of novel bidentate NS2B-NS3pro inhibitors.

  • Broad-spectrum non-nucleoside inhibitors for caliciviruses
    Antivir. Res. (IF 4.271) Pub Date : 2017-07-27
    Natalie E. Netzler, Daniel Enosi Tuipulotu, Auda A. Eltahla, Jennifer H. Lun, Salvatore Ferla, Andrea Brancale, Nadya Urakova, Michael Frese, Tanja Strive, Jason M. Mackenzie, Peter A. White

    Viruses of the Caliciviridae cause significant and sometimes lethal diseases, however despite substantial research efforts, specific antivirals are lacking. Broad-spectrum antivirals could combat multiple viral pathogens, offering a rapid solution when no therapies exist. The RNA-dependent RNA polymerase (RdRp) is an attractive antiviral target as it is essential for viral replication and lacks mammalian homologs. To focus the search for pan-Caliciviridae antivirals, the RdRp was probed with non-nucleoside inhibitors (NNIs) developed against hepatitis C virus (HCV) to reveal both allosteric ligands for structure-activity relationship enhancement, and highly-conserved RdRp pockets for antiviral targeting. The ability of HCV NNIs to inhibit calicivirus RdRp activities was assessed using in vitro enzyme and murine norovirus cell culture assays. Results revealed that three NNIs which bound the HCV RdRp Thumb I (TI) site also inhibited transcriptional activities of six RdRps spanning the Norovirus, Sapovirus and Lagovirus genera of the Caliciviridae. These NNIs included JTK-109 (RdRp inhibition range: IC50 4.3–16.6 μM), TMC-647055 (IC50 range: 18.8–45.4 μM) and Beclabuvir (IC50 range: 23.8–>100 μM). In silico studies and site-directed mutagenesis indicated the JTK-109 binding site was within the calicivirus RdRp thumb domain, in a pocket termed Site-B, which is highly-conserved within all calicivirus RdRps. Additionally, RdRp inhibition assays revealed that JTK-109 was antagonistic with the previously reported RdRp inhibitor pyridoxal-5′-phosphate-6-(2′-naphthylazo-6′-nitro-4′,8′-disulfonate) tetrasodium salt (PPNDS), that also binds to Site-B. Moreover, like JTK-109, PPNDS was also a potent inhibitor of polymerases from six viruses spanning the three Caliciviridae genera tested (IC50 range: 0.1–2.3 μM). Together, this study demonstrates the potential for de novo development of broad-spectrum antivirals that target the highly-conserved RdRp thumb pocket, Site-B. We also revealed three broad-spectrum HCV NNIs that could be used as antiviral scaffolds for further development against caliciviruses and other viruses.

  • Screening of an FDA-approved compound library identifies levosimendan as a novel anti-HIV-1 agent that inhibits viral transcription
    Antivir. Res. (IF 4.271) Pub Date : 2017-08-24
    Tsuyoshi Hayashi, Maxime Jean, Huachao Huang, Sydney Simpson, Netty G. Santoso, Jian Zhu

    Combination antiretroviral therapy (cART) has been proven to efficiently inhibit ongoing replication of human immunodeficiency virus type 1 (HIV-1), and significantly improve the health outcome in patients of acquired immune deficiency syndrome (AIDS). However, cART is unable to cure HIV-1/AIDS. Even in presence of cART there exists a residual viremia, contributed from the viral reservoirs of latently infected HIV-1 proviruses; this constitutes a major hurdle. Currently, there are multiple strategies aimed at eliminating or permanently silence these HIV-1 latent reservoirs being intensely explored. One such strategy, a recently emerged “block and lock” approach is appealing. For this approach, so-called HIV-1 latency-promoting agents (LPAs) are used to reinforce viral latency and to prevent the low-level or sporadic transcription of integrated HIV-1 proviruses. Although several LPAs have been reported, there is still a question of their suitability to be further developed as a safe and valid therapeutic agent for the clinical use. In this study, we aimed to identify new potential LPAs through the screening an FDA-approved compound library. A new and promising anti-HIV-1 inhibitor, levosimendan, was identified from these screens. Levosimendan is currently used to treat heart failure in clinics, but it demonstrates strong inhibition of TNFα-induced HIV-1 reactivation in multiple cell lines of HIV-1 latency through affecting the HIV-1 Tat-LTR transcriptional axis. Furthermore, we confirmed that in primary CD4+ T cells levosimendan inhibits both the acute HIV-1 replication and the reactivation of latent HIV-1 proviruses. As a summary, our studies successfully identify levosimendan as a novel and promising anti-HIV-1 inhibitor, which should be immediately investigated in vivo given that it is already an FDA-approved drug.

  • Rapamycin-induced autophagy restricts porcine epidemic diarrhea virus infectivity in porcine intestinal epithelial cells
    Antivir. Res. (IF 4.271) Pub Date : 2017-08-24
    Seongyeol Ko, Min Jeong Gu, Cheol Gyun Kim, Yoon Chul Kye, Younggap Lim, Ji Eun Lee, Byung-Chul Park, Hyuk Chu, Seung Hyun Han, Cheol-Heui Yun

    Porcine epidemic diarrhea virus (PEDV) invades porcine intestinal epithelial cells (IECs) and causes diarrhea and dehydration in pigs. In the present study, we showed a suppression of PEDV infection in porcine jejunum intestinal epithelial cells (IPEC-J2) by an increase in autophagy. Autophagy was activated by rapamycin at a dose that does not affect cell viability and tight junction permeability. The induction of autophagy was examined by LC3I/LC3II conversion. To confirm the autophagic-flux (entire autophagy pathway), autophagolysosomes were examined by an immunofluorescence assay. Pre-treatment with rapamycin significantly restricted not only a 1 h infection but also a longer infection (24 h) with PEDV, while this effect disappeared when autophagy was blocked. Co-localization of PEDV and autophagosomes suggests that PEDV could be a target of autophagy. Moreover, alleviation of PEDV-induced cell death in IPEC-J2 cells pretreated with rapamycin demonstrates a protective effect of rapamycin against PEDV-induced epithelial cell death. Collectively, the present study suggests an early prevention against PEDV infection in IPEC-J2 cells via autophagy that might be an effective strategy for the restriction of PEDV, and opens up the possibility of the use of rapamycin in vivo as an effective prophylactic and prevention treatment.

  • Bis(benzofuran–thiazolidinone)s and bis(benzofuran–thiazinanone)s as inhibiting agents for chikungunya virus
    Antivir. Res. (IF 4.271) Pub Date : 2017-08-19
    Jih Ru Hwu, Nitesh K. Gupta, Shwu-Chen Tsay, Wen-Chieh Huang, Irina C. Albulescu, Kristina Kovacikova, Martijn J. van Hemert
  • Evaluation of antiviral activity of piperazine against Chikungunya virus targeting hydrophobic pocket of alphavirus capsid protein
    Antivir. Res. (IF 4.271) Pub Date : 2017-08-24
    Megha Aggarwal, Ramanjit Kaur, Amrita Saha, Rajat Mudgal, Ravi Yadav, Paban Kumar Dash, Manmohan Parida, Pravindra Kumar, Shailly Tomar

    Small heterocyclic molecules such as piperazine are potential pharmacotherapeutic agents and binding of these molecules to the hydrophobic pocket of capsid protein (CP) offers a new perspective for therapeutic intervention. Here, we report the crystal structure of CP from Aura virus (AVCP) in complex with piperazine at 2.2 Å resolution. Piperazine binds to the conserved hydrophobic pocket of CP where dioxane based antivirals bind. Comparative structural studies of the piperazine-bound AVCP structure with the apo, active and dioxane-bound AVCP structures provide insights into the conformational variations in the pocket. Additionally, the molecular docking studies showed that piperazine binds into the hydrophobic pocket of Chikungunya virus CP (CVCP) with more affinity than with AVCP. Furthermore, the antiviral activity of piperazine against Chikungunya virus (CHIKV) was investigated by plaque reduction and immunofluorescence assays. The AVCP-piperazine complex may serve as a lead scaffold for structure-based design of piperazine derivatives as alphaviral inhibitors. The antiviral properties of piperazine provide its usefulness for further investigations towards the development of piperazine based anti-alphaviral drugs.

  • Identification of broadly neutralizing monoclonal antibodies against Crimean-Congo hemorrhagic fever virus
    Antivir. Res. (IF 4.271) Pub Date : 2017-08-24
    Marko Zivcec, Lisa I.W. Guerrero, César G. Albariño, Éric Bergeron, Stuart T. Nichol, Christina F. Spiropoulou

    Despite the serious public health impact of Crimean-Congo hemorrhagic fever (CCHF), the efficacy of antivirals targeting the causative agent, CCHF virus (CCHFV), remains debatable. Neutralizing monoclonal antibodies (MAbs) targeting the CCHFV glycoprotein Gc have been reported to protect mice against challenge with the prototype CCHFV strain, IbAr10200. However, due to extensive sequence diversity of CCHFV glycoproteins, it is unknown whether these MAbs neutralize other CCHFV strains. We initially used a CCHF virus-like particle (VLP) system to generate 11 VLP moieties, each possessing a glycoprotein from a genetically diverse CCHFV strain isolated in either Africa, Asia, the Middle East, or southeastern Europe. We used these VLPs in biosafety level 2 conditions to efficiently screen MAb cross-neutralization potency. Of the 16 MAbs tested, 3 (8A1, 11E7, and 30F7) demonstrated cross-neutralization activity with most CCHF VLPs, with 8A1 neutralizing all VLPs tested. Although binding studies suggest that none of the MAbs compete for the same epitope, combining 11E7, 30F7, or both 11E7 and 30F7 with 8A1 had no additive effect on increasing neutralization in this system. To confirm our findings from the VLP system, the 3 MAbs capable of strain cross-neutralization were confirmed to effectively neutralize 5 diverse CCHFV strains in vitro. Passaging CCHFV strains in the presence of sub-neutralizing concentrations of MAbs did not generate escape mutants resistant to subsequent neutralization. This study demonstrates the utility of the VLP system for screening neutralizing MAbs against multiple CCHFV strains, and provides the first evidence that a single MAb can effectively neutralize a number of diverse CCHFV strains in vitro, which may lead to development of future CCHF therapeutics.

  • Combination therapy with brincidofovir and valganciclovir against species C adenovirus infection in the immunosuppressed Syrian hamster model allows for substantial reduction of dose for both compounds
    Antivir. Res. (IF 4.271) Pub Date : 2017-08-04
    Karoly Toth, Ann E. Tollefson, Jacqueline F. Spencer, Baoling Ying, William S.M. Wold

    Adenovirus infections of immunocompetent adults are usually mild and resolve without serious sequelae. However, adenovirus infections of immunocompromised patients often develop into life-threatening multi-organ disease. Pediatric hematopoietic transplant patients are especially threatened, with high incidence of infection and high mortality rates. Presently, there is no drug specifically approved by the FDA to treat adenovirus infections; thus there is an urgent need to develop effective antivirals against the virus. Previously, we demonstrated that brincidofovir and valganciclovir were efficacious against lethal intravenous challenge with human type 5 adenovirus in the Syrian hamster model. Here, we tested the in vivo efficacy of the combination of these two drugs and showed that the combination of brincidofovir and valganciclovir is more efficacious than either drug alone, thus potentially allowing decreased patient exposure to the drugs while maintaining antiviral efficacy. As antiviral compounds often have toxic side effects, a decrease in dose or duration of therapy allowed by the combination could also improve tolerability.

  • Evaluation of antiviral effect of type I, II, and III interferons on direct-acting antiviral-resistant hepatitis C virus
    Antivir. Res. (IF 4.271) Pub Date : 2017-08-31
    Atsushi Hamana, Yuki Takahashi, Takuro Uchida, Makiya Nishikawa, Michio Imamura, Kazuaki Chayama, Yoshinobu Takakura

    Treatment of hepatitis C virus (HCV) infection has greatly improved in the last 5 years because of the identification of direct-acting antivirals (DAAs). However, concerns exist regarding the emergence of drug resistance-associated substitutions (RASs). In this study, we evaluated the in vivo antiviral effect of three classes of interferons (IFNs), namely, types I, II, and III IFNs, on DAA-resistant HCVs. IFN-α2, IFN-γ, and IFN-λ1 were selected as typical types I, II, and III IFNs, respectively. Human hepatocyte-transplanted chimeric mice were infected with NS3-D168, NS5A-L31-, and NS5A-Y93-mutated HCVs, and the antiviral effect of IFN-α2, IFN-γ, and IFN-λ1 on these HCV RASs was examined. Chimeric mice infected with NS3- and NS5A-mutated HCVs were hydrodynamically injected with IFN-expressing plasmids to evaluate the antiviral effect of IFNs. Serum concentrations of IFNs were maintained for at least 42 days. We found that serum HCV level significantly decreased and serum and hepatic HCV levels reached below detection limit in 5/5 and 3/5 chimeric mice injected with IFN-γ- and IFN-λ1-expressing plasmids, respectively. The antiviral effect of IFN-α2 on DAA-resistant HCVs was weaker than that of IFN-γ and IFN-λ1. Serum ALT levels showed a small and transient increase in mice injected with the IFN-γ-expressing plasmid but not in mice injected with the IFN-λ1-expressing plasmid. However, no apparent histological damage was observed in the liver sections of mice injected with the IFN-γ-expressing plasmid. These results indicate that IFN-γ and IFN-λ1 are an attractive therapeutic option for treating infection caused by NS3- and NS5A-mutated HCV.

  • Searching for synergy: Identifying optimal antiviral combination therapy using Hepatitis C virus (HCV) agents in a replicon system
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-04
    Justin J. Pomeroy, George L. Drusano, Jaime L. Rodriquez, Ashley N. Brown

    Direct acting antiviral agents (DAAs) are potent inhibitors of Hepatitis C virus (HCV) that have revolutionized the treatment landscape for this important viral disease. There are currently four classes of DAAs that inhibit HCV replication via distinct mechanisms of action: nonstructural protein (NS) 3/4a protease inhibitors, NS5A inhibitors, NS5B nucleoside polymerase inhibitors, and NS5B non-nucleoside polymerase inhibitors. Combination therapy with two or more DAAs has great potential to further enhance antiviral potency. The purpose of this study was to identify optimal combinations of DAAs against genotype 1 HCV replicons that maximized the inhibition of replicon replication. All possible two-drug combinations were evaluated against genotype 1a and 1b HCV replicons using a 96-well plate luciferase-based assay in triplicate. The Greco Universal Response Surface Area mathematical model was fit to the luciferase data to identify drug-drug interactions (i.e.: synergy, additivity, and antagonism) for antiviral effect against both genotypes. This information was used to rank-order combinations of DAAs based on their ability to inhibit replicon replication against genotype 1a and 1b HCV. These preclinical findings can provide information as to which antiviral regimens should move on in the development process.

  • Cell-line dependent antiviral activity of sofosbuvir against Zika virus
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-11
    Noreen Mumtaz, Leah C. Jimmerson, Lane R. Bushman, Jennifer J. Kiser, Georgina Aron, Chantal B.E.M. Reusken, Marion P.G. Koopmans, Jeroen J.A. van Kampen

    The recent epidemic of Zika virus (ZIKV) in the Americas and its association with fetal and neurological complications has shown the need to develop a treatment. Repurposing of drugs that are already FDA approved or in clinical development may shorten drug development timelines in case of emerging viral diseases like ZIKV. Initial studies have shown conflicting results when testing sofosbuvir developed for treatment of infections with another Flaviviridae virus, hepatitis C virus. We hypothesized that the conflicting results could be explained by differences in intracellular processing of the compound. We assessed the antiviral activity of sofosbuvir and mericitabine against ZIKV using Vero, A549, and Huh7 cells and measured the level of the active sofosbuvir metabolite by mass spectrometry. Mericitabine did not show activity, while sofosbuvir inhibited ZIKV with an IC50 of ∼4 μM, but only in Huh7 cells. This correlated with differences in intracellular concentration of the active triphosphate metabolite of sofosbuvir, GS-461203 or 007-TP, which was 11–342 times higher in Huh7 cells compared to Vero and A549 cells. These results show that a careful selection of cell system for repurposing trials of prodrugs is needed for evaluation of antiviral activity. Furthermore, the intracellular levels of 007-TP in tissues and cell types that support ZIKV replication in vivo should be determined to further investigate the potential of sofosbuvir as anti-ZIKV compound.

  • Human polyclonal antibodies produced in transchromosomal cattle prevent lethal Zika virus infection and testicular atrophy in mice
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-08
    Derek R. Stein, Joseph W. Golden, Bryan D. Griffin, Bryce M. Warner, Charlene Ranadheera, Leanne Scharikow, Angela Sloan, Kathy L. Frost, Darwyn Kobasa, Stephanie A. Booth, Matthew Josleyn, John Ballantyne, Eddie Sullivan, Jin-an Jiao, Hua Wu, Zhongde Wang, Jay W. Hooper, David Safronetz
  • Raltegravir blocks the infectivity of red-fluorescent-protein (mCherry)-labeled HIV-1JR-FL in the setting of post-exposure prophylaxis in NOD/SCID/Jak3−/− mice transplanted with human PBMCs
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-08
    Hiromi Ogata-Aoki, Nobuyo Higashi-Kuwata, Shin-ichiro Hattori, Hironori Hayashi, Matthew Danish, Manabu Aoki, Chiemi Shiotsu, Yumi Hashiguchi, Akinobu Hamada, Hisataka Kobayashi, Hironobu Ihn, Seiji Okada, Hiroaki Mitsuya

    Employing NOD/SCID/Jak3−/− mice transplanted with human PBMCs (hNOJ mice) and replication-competent, red-fluorescent-protein (mCherry; mC)-labeled HIV-1JR-FL (HIVmC), we examined whether early antiretroviral treatment blocked the establishment of HIV-1 infection. The use of hNOJ mice and HIVmC enabled us to visually locate infection foci and to examine the early dynamics of HIVmC infection without using a large amount of antiretroviral unlike in non-human primate models. Although when raltegravir (RAL) administration was begun 1 day after intraperitoneal (ip) inoculation of HIVmC, no plasma p24 or plasma HIV-1-RNA (pRNA) were detected in 10 of 12 hNOJ (hNOJmCRAL+) mice over 14-day observation, all 10 untreated hNOJmC (hNOJmCRAL−) mice became positive for p24 and pRNA and had significantly swollen lymph nodes in peritoneal cavity and abundant p24+/mC+/CD3+/CD4+ T cells and p24+/mC+/CD68+ monocytes/macrophages were identified in their omenta and mesenteric lymphoid tissues/lymph nodes. In 12 hNOJmCRAL+ mice, no significantly swollen lymph nodes were seen compared to hNOJmCRAL− mice; however, in the omentum of the 2 hNOJmCRAL+ mice that were positive for pRNA and in site RNA, mC+/p24+/CD3+/CD83+ cells were identified, suggesting that viral breakthrough occurred later in the observation period. The present data suggest that the use of hNOJ mouse model and HIVmC may shed light in the study of early-phase dynamics of HIV-1 infection and cellular events in post-exposure/pre-exposure prophylaxis.

  • DHEA prevents ribavirin-induced anemia via inhibition of glucose-6-phosphate dehydrogenase
    Antivir. Res. (IF 4.271) Pub Date : 2017-09-08
    Lynda Handala, Barbara Domange, Hakim Ouled-Haddou, Loïc Garçon, Eric Nguyen-Khac, Francois Helle, Sandra Bodeau, Gilles Duverlie, Etienne Brochot

    Ribavirin has been widely used for antiviral therapy. Unfortunately, ribavirin-induced anemia is often a cause of limiting or interrupting treatment. Our team has observed that dehydroepiandrosterone (DHEA) has a protective effect against in vitro and in vivo ribavirin-induced hemolysis. The aim of this study was to better understand this effect as well as the underlying mechanism(s).DHEA was able to reduce in vitro intraerythrocytic ATP depletion induced by ribavirin. Only 1% of ATP remained after incubation with ribavirin (2 mM) at 37 °C for 24 h vs. 37% if DHEA (200 μM) was added (p < 0.01). DHEA also helped erythrocytes conserve their size, with a shrinkage of only 10% vs 40% at 24 h with ribavirin alone (p < 0.01), and reduced phosphatidylserine exposure at the outer membrane, i.e. 27% vs 40% at 48 h, (p < 0.05). DHEA also inhibits ribavirin-induced hemolysis, i.e. 34% vs 46.5% at 72 h (p < 0.01).DHEA is an inhibitor of glucose-6-phosphate dehydrogenase (G6PD), a key enzyme in the hexose monophosphate shunt connected to the glycolytic pathway which is the only energy supplier of the red blood cell in the form of ATP. We have confirmed this inhibitory effect in the presence of ribavirin. All these observations suggest that ribavirin-induced hemolysis was initiated by ATP depletion, and that the inhibitory effect of DHEA on G6PD was able to rescue enough ATP to limit this hemolysis. This mechanism could be important for improving the therapeutic management of patients treated with ribavirin.

  • Comparison of three dimensional synergistic analyses of percentage versus logarithmic data in antiviral studies
    Antivir. Res. (IF 4.271) Pub Date : 2017-07-01
    Donald F. Smee, Mark N. Prichard

    Cell culture antiviral experiments were conducted in order to understand the relationship between percentage data generated by plaque reduction (PR) and logarithmic data derived by virus yield reduction (VYR) assays, using three-dimensional MacSynergy II software. The relationship between percentage and logarithmic data has not been investigated previously. Interpretation of drug-drug interactions is based on a Volume of Synergy (VS) calculation, which can be positive (synergy), negative (antagonistic), or neutral (no or minimal interaction). Interactions of two known inhibitors of vaccinia virus replication, cidofovir and 6-azauridine, used in combination by PR assay yielded a VS value of 265, indicative of strong synergy. By VYR, the VS value was only 37, or weak synergy using the same criterion, even though profound log10 reductions in virus titer occurred at multiple drug combinations. These results confirm that the differences in VS values is dependent of the measurement scale, and not that the degree of synergy differed between the assays. We propose that for logarithmic data, the calculated VS values will be lower for significant synergy and antagonism and that volumes of >10 μM2log10 PFU/ml (or other units such as μM2log10 genomic equivalents/ml or μM2log10 copies/ml) and <-10 μM2log10 PFU/ml are likely to be indicative of strong synergy and strong antagonism, respectively. Data presented here show that the interaction of cidofovir and 6-azauridine was strongly synergistic in vitro.

Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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