Early TNFα signaling results in pulmonary DC1 polarization and programing of murine myeloid precursor cells in the bone marrow towards DC1 polarization throughout Cryptococcus neoformans infection

TNFα is required for protective Th1/Th17 immunity to Cryptococcus neoformans (CN), an opportunistic pulmonary fungal pathogen. The effects of TNFα are linked to the stable, early classical activation of dendritic cells (DC1), preventing alternative (DC2) activation. We hypothesized that TNFα signaling facilitates epigenetic modification of key DC genes during CN infection. We tested this hypothesis using CBA/J mice infected intratracheally with CN and injected once on day 0 intraperitoneally with control or a TNFα-depleting antibody (αTNFα). αTNFα mice had no difference in pulmonary CFU at 7 days post-infection (dpi), but had significantly higher fungal burden and extrapulmonary dissemination at 14 and 28 dpi. DCs from the lungs of control mice at 7 dpi had increased association of iNOS and IL-12b promoters with the activating modification histone 3 lysine 4 trimethylation (H3K4me3), while DCs from αTNFα mice did not. Because DCs have a relatively short half-life during infection, we assessed the bone marrow (BM) myeloid precursor cells (MPCs) from infected animals with and without TNFα. Intranuclear flow cytometry for H3K4me3 showed distinct patterns of global trimethylation between infected control and αTNFα mice as early as 7 dpi. We next tested whether BM-derived DCs (BMDCs) matured ex vivo from infected animals would yield DC1 or DC2 cells. BMDCs from control animals became DC1, and resisted changes to polarization when challenged with the DC2-skewing IL-4, while BMDCs matured from TNFα-depleted mice maintained DC2 polarization when challenged with IFNγ. We conclude that TNFα epigenetically modifies key DC1 genes in MPCs, thereby sustaining lasting DC1 programing of DCs required for clearance of CN from the infected lungs.