Detection of Antibody Responses against SARS-CoV-2 in Plasma and Saliva from Vaccinated and Infected Individuals—Klinger 2021

All vaccines targeting the SARS-CoV-2 spike induce antibodies (Abs), which are necessary for the host immune response. Many studies have evaluated Ab reactions in vaccinated and infected blood. SARS-CoV-2 is a respiratory virus, thus understanding mucosal Ab responses upon initial virus exposure is equally important. We compared plasma and saliva Ab responses in vaccinated and convalescent subjects. Although saliva levels were much lower, plasma and saliva total Ig levels against all SARS-CoV-2 antigens correlated strongly. Saliva had fewer IgM and IgA1 Abs than plasma, but virus-specific IgG1 responses predominated. Plasma Abs' antiviral properties were examined. Neutralization titers against the initial WA1 (D614G), B.1.1.7 (alpha), B.1.617.2 (delta), and B.1.351 (beta) strains were similar but lower. Spike-specific antibody-dependent cellular phagocytosis (ADCP) activities linked with spike-binding Ig titers. While neutralization and ADCP potencies were comparable, vaccinated groups had higher complement deposition to spike-specific Abs and higher IgG1 and IgG3 levels. This study shows that plasma and saliva Ab responses following immunization or infection correlate, despite Ig isotypic variations. Vaccination increased complement activation in plasma Abs with Fab-mediated and Fc-dependent neutralization and ADCP potencies.

Klingler, J., Lambert, G. S., Itri, V., Liu, S., Bandres, J. C., Enyindah-Asonye, G., Liu, X., Simon, V., Gleason, C. R., Kleiner, G., Chiu, H. P., Hung, C. T., Kowdle, S., Amanat, F., Lee, B., Zolla-Pazner, S., Upadhyay, C., & Hioe, C. E. (2021). Detection of Antibody Responses against SARS-CoV-2 in Plasma and Saliva from Vaccinated and Infected Individuals. medRxiv : the preprint server for health sciences, 2021.05.11.21256972. https://doi.org/10.1101/2021.05.11.21256972