Mucosal IgA against SARS-CoV-2 Omicron Infection

Abstract

Mucosal IgA against SARS-CoV-2 Omicron InfectionTo the Editor: Havervall et al. (Oct.6 issue) 1 suggest that wild-type SARS-CoV-2 spike-specific mucosal IgA may provide protection against omicron (B.1.1.529)breakthrough infection.We detected salivary anti-receptor-binding domain (RBD) IgA antibodies against G614 RBD in 48 of 67 vaccinated healthy persons (72%) at 5 to 59 days after receiving a dose of messenger RNA (mRNA) vaccine -in 12 of 18 (67%) after dose 1, in 22 of 34 (65%) after dose 2, and in 14 of 15 (93%) after dose 3. We also observed these antibodies in 12 of 12 persons (100%) 8 to 43 days after they had had a breakthrough infection.Prevaccinated, noninfected persons served as controls to determine the baseline antibody level (Fig. 1A, and the Methods section and Table S1 in the Supplementary Appendix, available with the full text of this letter at NEJM.org).The level of salivary anti-RBD IgA antibodies showed a stronger correlation with the level of RBD-specific secretory immunoglobulin (sIg, detected with the use of an antisecretory component antibody) (r = 0.62, P<0.001) than with RBD-specific serum IgA antibodies (r = 0.35, P = 0.001), findings that suggest that most of the measured salivary IgA was secretory IgA (sIgA) that was produced locally in the salivary glands.Furthermore, salivary anti-RBD IgM antibodies were detected in only a low percentage of vaccinated persons (10%), which suggests that the majority of measured sIg antibodies were RBD-specific sIgA antibodies.The salivary RBD-specific IgA antibodies were maintained at a low level for more than 5 months after the second and third dose of vaccine.After breakthrough infection during the omicron BA.1 wave, salivary-specific IgA antibodies were induced and sustained at a higher level (Fig. 1B).Among 29 vaccinated persons monitored for 6 months after the second dose of vaccine, salivary anti-RBD IgA and sIg levels, but not plasma anti-RBD IgG levels or salivary anti-RBD IgG or IgM levels, were significantly lower in 9 persons with breakthrough infection than in 20 persons without such infection (P = 0.002 for salivary

Topics & Concepts