Feline calicivirus (FCV) is a small non-enveloped virus containing a single-stranded, positive-sense RNA genome of approximately 7.7 kb. FCV is a highly infectious pathogen of cats and typically causes moderate, self-limiting acute oral and upper respiratory tract diseases or chronic oral diseases. In addition, in recent years, virulent, systemic FCV (vs-FCV) strains causing severe systemic diseases with a high mortality rate of up to 67% have been reported in cats. Although FCV vaccines are commercially available, their efficacy is limited due to antigenic diversity of FCV strains and short duration of immunity. In this study, we identified fexaramine as a potent inhibitor of FCV including vs-FCV strains in cell culture and demonstrated that fexaramine is a entry blocker for FCV by using various experiments including time-of-addition studies, generation of resistant viruses in cell culture and the reverse genetics system. A fexaramine resistant FCV mutant has a single amino acid change in the P2 domain of VP1 (the major capsid), and the importance of this mutation for conferring resistance was confirmed using the reverse genetics system. A comparative analysis of viral resistance was also performed using a peptidyl inhibitor (NPI52) targeting FCV 3C-like protease. Finally, the effects of combination treatment of fexaramine and NPI52 against FCV replication and emergence of resistant viruses were investigated in cell culture.

猫杯状病毒 (FCV) 是一种小型无包膜病毒，含有约 7.7 kb 的单链正链 RNA 基因组。 FCV 是猫的一种高度传染性病原体，通常会导致中度、自限性急性口腔和上呼吸道疾病或慢性口腔疾病。此外，近年来，据报道，致命的系统性FCV（vs-FCV）菌株可在猫中引起严重的全身性疾病，死亡率高达67%。尽管 FCV 疫苗已市售，但由于 FCV 毒株的抗原多样性和免疫持续时间短，其功效有限。在这项研究中，我们确定 fexaramine 是 FCV 的有效抑制剂，包括细胞培养中的 vs-FCV 菌株，并通过使用各种实验（包括添加时间研究、细胞培养中耐药病毒的产生）证明 fexaramine 是 FCV 的进入阻断剂和反向遗传学系统。 Fexaramine 抗性 FCV 突变体在 VP1（主要衣壳）的 P2 结构域中具有单个氨基酸变化，并且使用反向遗传学系统证实了该突变对于赋予抗性的重要性。还使用针对 FCV 3C 样蛋白酶的肽基抑制剂 (NPI52) 进行了病毒耐药性的比较分析。最后，在细胞培养中研究了 fexaramine 和 NPI52 联合治疗对 FCV 复制和耐药病毒出现的影响。