Lung-resident memory Th2 cells regulate pulmonary cryptococcosis by inducing type-II granuloma formation.

Lung-resident memory T cells (lung TRMs) settle in the lung and respond rapidly to external antigens, and are therefore considered to have great potential for development of respiratory vaccines. Here, we demonstrate that lung-resident memory Th2 cells (lung TRM2) protect against pulmonary mycosis caused by Cryptococcus gattii. We developed novel whole-cell intranasal vaccines using a heat-inactivated C.gattii capsule-deficient strain cap59Δ, which induced ST-2⁺ Gata-3⁺ lung TRM2 specifically responding to C.gattii whole-cell antigen. Lung fungal burden and survival rate were significantly improved in immunized mice after infection challenge. The immunosuppressive agent FTY720 did not impact vaccine effectiveness, and adoptive transfer of lung TRMs into Rag-1-deficient mice decreased the lung fungal burden. In IL-4/IL-13 double-knockout (DKO) mice, immunization did not efficiently induce eosinophil recruitment and granuloma formation, and the fungal burden was not decreased after infection challenge. Co-culture of lung TRM2 with myeloid lineages induced multinucleated giant cells (MGCs) in the presence of antigen, which phagocytosed live C.gattii cells without opsonization, whereas lung TRM2 from DKO mice did not induce MGCs. These findings provide a new model in which lung TRM2 suppress C.gattii infection via granuloma induction.