Non-invasive detection of IgG antibodies from common pathogenic viruses using oral flocked swabs

Highlights

• Oral flocked swabs are an easy, self-collection method for measuring viral antibodies.

• Viral IgG is stable on dried oral flocked swabs for at least 2 years.

• Oral swabs are highly sensitive for CMV, VZV, and EBV IgG.

• Oral swabs are potentially useful for surveillance and clinical microbiology.

Abstract

Salivary antibodies are useful in surveillance and vaccination studies. However, low antibody levels and degradation by endonucleases are problematic. Oral flocked swabs are a potential non-invasive alternative for detecting viral antibodies. Seroprevalence for Cytomegalovirus (CMV), Varicella-Zoster virus (VZV), Epstein–Barr virus (EBV), Measles and Mumps IgG antibodies were determined from 50 matched serum, saliva and swabs samples from healthy volunteers using commercial ELISAs. CMV IgG, VZV IgG, and EBV EBNA-1 IgG, VCA IgG, and Measles IgG swab versus serum sensitivities were 95.8%, 96.0%, 92.1%, 95.5%, 84.5%, respectively, and swabs correlated well with saliva. Sensitivity of Mumps IgG in swabs and saliva was poor at 60.5%, and 68.2%, respectively. Specificities for IgG antibodies were 100% for CMV, EBV and Mumps, but could not be determined for VZV and Measles due to exclusively seropositive volunteers. Except for Mumps IgG, swabs correlate well with serum, are easy to self-collect and are stable at room temperature.

Introduction

Immunological screening for viral antibodies (primarily IgG) in serum to assess past infection or vaccine immunity is routinely performed via commercial enzyme immunoassays (EIAs) on closed platforms. Serum is the gold standard for determining immune status but is invasive to collect. Saliva has considerable diagnostic potential: it is non-invasive, abundant, easily collected, and representative of oral and systemic health. Salivary diagnostics is rapidly emerging, especially defining biomarkers for point-of-care testing of infectious diseases (Khan et al., 2017). Salivary antibodies are primarily secretory IgA from the salivary glands, while IgG and IgM are derived from serum plasma cells and passively diffused into the oral cavity via gingival crevicular fluid (Parry et al., 1987; Brandtzaeg, 2007). Salivary IgG (sIgG) is systemically representative and strongly correlates with serum levels, but loads are ~1:800 that of serum (Saccoccio et al., 2011; Dimech and Mulders, 2016). This is problematic for typical closed testing systems that incorporate a 1:100 dilution step. Despite low levels, salivary antibodies are utilized in the U.S. Food and Drug Administration approved OraQuick ADVANCE® Rapid HIV-1/2 Antibody Test (OraSure Technologies, Inc., USA) and OraQuick® HCV Test (OraSure Technologies, Inc.) (Khan et al., 2017). However, many commercial assays are cost-prohibitive for resource-constrained settings.

Saliva collection can be difficult in children and hyposalivators, such as immunocompromised patients. Salivary endonucleases are detrimental, remaining active at -80°C, necessitating special handling, or storage in proteolytic stabilizers unsuitable for antibody preservation (Speicher et al., 2015). To overcome these limitations, procedures for viral antibody detection were optimized on an open commercial platform for dried oral flocked swabs, after room temperature storage. The efficiency of oral flocked swabs to detect viral antibodies has yet to be determined. Our method was initially optimized for Cytomegalovirus (CMV) IgG due to its importance in hematopoietic stem cell, solid organ, and haploidentical transplantations as well as prenatal patients (Ljungman et al., 2011; Dollard et al., 2014). We then assessed the procedures' potential application to detect Varicella-Zoster virus (VZV), Epstein–Barr virus (EBV), Measles and Mumps IgG.