Proteomic deconvolution of the antigen-specific serum IgA repertoire reveals clonal overlap with IgG and between monomeric and dimeric IgA following mucosal norovirus vaccination 2438

Abstract Description IgA antibodies are key to mucosal immunity; however, the identity, abundance, and oligomeric states of individual IgA clonotypes comprising the polyclonal repertoire remain poorly understood. To determine the molecular nature and protective mechanism of IgA clones elicited by mucosal vaccination, we performed serum proteomics analysis (Ig-Seq) in three subjects immunized with an oral norovirus vaccine designed for gut delivery. Serum IgA titers specific to the GII.4 norovirus vaccine strain were higher than IgG titers both on day 0 pre- and day 28 post-vaccination. Ig-Seq analysis of GII.4-specific serum IgA and IgG repertoires revealed that oral vaccination increased IgG+IgA clonal overlap by 2.4-fold, with 43 ± 17% of IgA clonotypes on day 28 also detectable in IgG. Mass separation of monomeric (mIgA) and dimeric IgA (dIgA) showed that >75% of antigen-specific IgA clonotypes co-circulate in both forms, with some clonotypes 5-times more abundant as dIgA. Monoclonal dIgAs targeting surface-exposed, immunodominant GII.4 epitopes significantly enhanced neutralization potency compared to mIgA or IgG. Conversely, dIgAs targeting partially occluded epitopes showed minimal potency gains, suggesting that epitope accessibility may impact the neutralization mechanism of dIgA and that dIgA titers to highly exposed epitopes could provide robust protection at mucosal sites. Our study provides molecular insights into oligomeric serum IgA repertoires, guiding future mucosal vaccine design. Funding Sources National Institute of Allergy and Infectious Disease R01 AI148260. Topic Categories Vaccines and Immunotherapy (VAC)