Cellular signatures of hybrid immunity underpinning superior mucosal protection 2420

Abstract Description Understanding mucosal immunity is vital for designing vaccines against respiratory viruses like SARS-CoV-2. Immunity resulting from vaccination followed by infection may offer superior mucosal protection, yet the underlying mechanisms remain unclear. This study reveals the mucosal humoral, cellular, and molecular signatures underpinning this enhanced protection. Mice received two Spike mRNA doses and were challenged with mouse-adapted SARS-CoV-2. In these mice, bronchoalveolar lavage (BAL) single-cell RNA sequencing showed increased adaptive immune cells, enriched T and B cell activation pathways, enhanced T cell differentiation, and upregulated B cell IgA production. Flow cytometry confirmed increased SARS-CoV-2-specific IFN-γ and TNF-α producing CD4? and CD8? T cells. The group exhibited elevated mucosal RBD-specific B cell levels and significantly higher IgA responses, leading to the highest respiratory neutralizing antibody levels. In contrast, mucosal IgG levels were similar across all groups. Using K18-hACE2 mice infected with Omicron, we found that despite minimal lung pathology, these mice showed increased respiratory T and B cell responses and elevated mucosal and plasma IgA levels compared to vaccination or infection alone. This study offers insights into the cellular signaling networks providing superior mucosal protection following combined vaccination and infection, informing vaccination strategies against respiratory pathogens. Funding Sources The study was in part supported by the US National Institutes of Health grants AI147394, AG069264, AI112844, HL170961, AI154598, and AI176171 Topic Categories Vaccines and Immunotherapy (VAC)