Discordant Anti-SARS-COV-2 IgA Responses In Blood, Saliva, and Tears 2261177

Introduction To determine whether anti-SARS CoV-2 IgA responses in blood reflected the expression of anti-SARS CoV-2 IgA in mucosal tissues, anti-SARS-CoV-2 IgA antibodies in blood plasma, tears and saliva were measured by indirect ELISA before and after SARS-CoV-2 exposure or COVID-19 vaccination. Methods SARS-CoV-2 RBD of Wuhan (R&D Systems; Cat #10534CV) or Omicron (Proteogenix; PX-CoV-P080) were used to coat ELISA plates. Blood, tear or saliva specimens were added at 1:100, 1:40, and 1:5 dilutions respectively. Human anti-SARS-CoV-2 RBD (Wuhan) IgA monoclonal antibody (Proteogenix; Cat # PTXCOV-569) was used as a standard to determine the concentration of anti-SARS-CoV-2 RBD IgA antibody . Results Blood plasma was available from fourteen individuals before and after SARS-CoV-2 exposure or COVID-19 vaccination. Seroconversion for anti-SARS-CoV-2 IgG antibodies was observed in all individuals whereas only six of fourteen (43%) demonstrated anti-SARS-CoV-2 IgA antibodies. In a larger cohort of 39 participants that were anti-SARS-CoV-2 RBD IgG positive, 16 (41%), 9 (23%), and 11(28%) were positive for anti-SARS-CoV-2 RBD IgA in blood, saliva and tears respectively. Forty four percent of individuals positive for anti-SARS-CoV-2 RBD IgA in blood were also IgA positive in saliva or tears. Thirty percent of individuals negative for anti-SARS-CoV-2 RBD IgA in blood were IgA positive in saliva or tears. In a pilot study three individuals with anti-SARS-CoV-2 IgA antibodies directed against Wuhan and Omicron variants demonstrated anti-SARS-CoV-2 IgA antibodies in the tears from both eyes. Conclusion Our data indicate that anti-SARS-CoV-2 IgA responses in blood, tears, and saliva are variable in SARS-CoV-2 exposed and COVID-19 vaccinated individuals with discordant responses in blood and mucosal tissues. Equivalent antibody responses in tears of both eyes suggests equal seeding of both lacrimal glands by antibody-producing B cells. Funding Source Franciscan Institute of Science and Health Topic Categories Mucosal and Regional Immunology (MUC)