Detection of antibodies to the SARS-CoV-2 spike glycoprotein in both serum and saliva enhances detection of infection

Abstract

Background: Detecting antibody responses during and after SARS-CoV-2 infection is essential in determining the seroepidemiology of the virus and the potential role of antibody in disease. Scalable, sensitive and specific serological assays are essential to this process. The detection of antibody in hospitalized patients with severe disease has proven straightforward; detecting responses in subjects with mild disease and asymptomatic infections has proven less reliable. We hypothesized that the suboptimal sensitivity of antibody assays and the compartmentalization of the antibody response may contribute to this effect. Methods: We systemically developed an ELISA assay, optimising different antigens and amplification steps, in serum and saliva from symptomatic and asymptomatic SARS-CoV-2-infected subjects. Results: Using trimeric spike glycoprotein, rather than nucleocapsid enabled detection of responses in individuals with low antibody responses. IgG1 and IgG3 predominate to both antigens, but more anti-spike IgG1 than IgG3 was detectable. All antigens were effective for detecting responses in hospitalized patients. Anti-spike, but not nucleocapsid, IgG, IgA and IgM antibody responses were readily detectable in saliva from non-hospitalized symptomatic and asymptomatic individuals. Antibody responses in saliva and serum were largely independent of each other and symptom reporting. Conclusions. Detecting antibody responses in both saliva and serum is optimal for determining virus exposure and understanding immune responses after SARS-CoV-2 infection. Funding. This work was funded by the University of Birmingham, the National Institute for Health Research (UK), the NIH National Institute for Allergy and Infectious Diseases, the Bill and Melinda Gates Foundation and the University of Southampton.

Immune responses to SARS-CoV-2 in three children of parents with symptomatic COVID-19

“…A2 and C3 had a low level but detectable neutralizing antibody activity in sera on days 12 and 37, respectively. Serological responses to SARS-CoV-2 are associated with disease severity 20,21 , although data from children who often have milder disease or are likely to be asymptomatic are limited. In our study, children had low to undetectable serum antibodies while both parents had strong serum IgG responses out to day 88.…”

Saliva in the Diagnosis of COVID-19: A Review and New Research Directions

“…The investigation for the presence of antibodies in saliva of large cohorts of individuals could better determine the prevalence of COVID-19, monitor disease progression, and help define previous exposure to SARS-CoV-2 in populations (Béné et al 2020). In fact, 2 non-peer-reviewed articles were recently published online demonstrating that the temporal kinetics of IgG, IgA, and IgM in the saliva of patients with COVID-19 were consistent with those observed in serum (Randad et al 2020) and that antibodies (IgA, IgG, and IgM) to the SARS-CoV-2 spike glycoprotein could be detected in serum and saliva (Faustini et al 2020).…”

Diagnostic Salivary Tests for SARS-CoV-2

“…Active infection can be detected by molecular-based testing for viral RNA, but this approach cannot be used for seroprevalence investigations. Antibody testing on blood samples (or saliva) is useful for determining historic exposure to the virus and may provide insight into the immunological status of the individual ( Faustini et al 2020 ). It can be performed both by lateral flow assay (LFA) directly in the field or by enzyme-linked immunosorbent assay (ELISA) and/or chemiluminiscent assay technologies in a centralized laboratory.…”

“…In one of these studies, antispike (but not nucleocapsid) IgG, IgA, and IgM antibody responses were readily detectable in saliva from nonhospitalized symptomatic and asymptomatic patients. Interestingly, antibody responses in the saliva and serum and symptoms are largely independent of one another ( Faustini et al 2020 ). In contrast to these results, another study evaluated the results of a multiplex immunoassay to detect specific antibodies in the crevicular fluid and found that SARS-CoV-2 antigen-specific IgG responses in matched serum and saliva samples were significantly correlated.…”