Professor Franciscan University of Steubenville Steubenville, Ohio, United States
Disclosure(s):
Kyle C. McKenna, PhD: No financial relationships to disclose
Introduction/Rationale: 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.
