Influenza-specific lung-resident memory B cells assist CD4 recall responses during challenge infections 2256984

Abstract

Abstract Introduction In repeated influenza A virus (IAV) infections, lung-resident memory B cells (BRMs) enhance early recall responses. However, in heterosubtypic infections, antibodies produced by lung BRMs do not neutralize the challenge virus’s surface glycoproteins, suggesting multifaceted functions of BRMs beyond antibody secretion. Methods Single-cell RNA sequencing of CD45+ lung cells after primary IAV/PR8 infection and subsequent IAV/X31 challenge revealed significant changes in B and T cell populations between B cell-specific STAT1 knockouts and C57BL/6 mice. B-STAT1 KOs failed to generate BRMs and exhibited a marked reduction in antibody secreting cells (ASCs), confirmed by ELISPOT assays showing decreased flu-specific IgA and IgG ASCs post-challenge. Flow cytometry analysis further showed decreased CD4+PD1hiCD11a+ and CD4+IFNγ effectors in the lung. Results Functionally, B-STAT1 KOs were more susceptible to reinfection, with reduced viral clearance compared to wildtypes. Importantly, antibody deficiency did not account for these observations, as antibody-deficient AID−/−α¼s−/− mice and B cell-specific BLIMP1 knockout mice, which still generated BRMs but produced minimal flu-specific antibodies, showed intact or enhanced CD4 T cell recall responses. To understand the mechanisms involved, we used B cell-specific MHCII inducible knockout mice and observed that deletion of MHCII in BRMs before challenge led to higher peak viral titers and fewer lung CD4+PD1hiCD11a+ effectors, along with abrogated secondary germinal centers and decreased flu-specific ASCs. Additionally, intranasal immunization with flu-specific B cell tetramers in wildtype mice showed that BRMs rapidly captured antigen in vivo, in contrast to their lymphoid counterparts. Conclusion Collectively, these findings emphasize that local interactions between BRMs and effector CD4 T cells are vital for effective antiviral responses in the lung, with BRMs supporting CD4 T cell functions, especially at low antigen doses through antigen presentation. Funding Source NIH 1R01AI153413-01 Topic Categories Mucosal and Regional Immunology (MUC)