Lung tissue resident memory T cells coordinate effector T cell dynamics during the protective recall response to influenza

Abstract

Abstract Influenza remains a serious public health challenge as the current vaccination strategy cannot protect against new strains that emerge every season. Tissue resident memory T cells (TRM) are a non-circulating memory subset that are generated in the lung after influenza infection or intranasal live vaccination, and these lung TRM have been shown to confer broad cross-strain protection. However, the mechanisms by which both CD4+ and CD8+ TRM mediate their protective response are not well defined. We investigated the tissue specific events during an active murine influenza response, including TRM-mediated protection and effector T cell trafficking. To specifically determine the role of TRM, we treated mice with the drug Fingolimod (FTY720), which sequesters circulating lymphocytes into secondary lymphoid organs, enriching the lung for tissue resident memory cells. We found that TRM immediately confer protection, with reduced viral titers evident as early as day 3 after infection. At later time points beginning at days 4–5 post infection, we determined that CD4+ and CD8+ TRM enhance the recruitment of influenza-specific effector T cells into the lung resident niche as well as CD4+ and CD8+ lymphocyte in situ proliferation as measured by BrdU incorporation. Furthermore, total lung RNA sequencing during active infection and FTY720 treatment reveal candidate TRM-associated chemokine pathways for tissue lymphocyte trafficking. These findings indicate that TRM uniquely influence the cellular dynamics of the lung resident niche to mediate cross-strain protection against influenza.