HIF-1α hampers dendritic cell function and Th1 generation during chronic visceral leishmaniasis.

Inflammation, although responsible for controlling infection, is often associated with the pathogenesis of chronic diseases. Leishmania donovani, the causative agent of visceral leishmaniasis, induces a strong inflammatory response that leads to splenomegaly and ultimately immune suppression. Inflamed tissues are typically characterized by low levels of oxygen, a microenvironment that triggers the hypoxia-inducible transcription factor 1α (HIF-1α). Although HIF-1α plays an integral role in dendritic cell function, its involvement in the generation of protective Th1 responses against Leishmania has not yet been studied. Here we demonstrate that HIF-1α inhibits IL-12 production in dendritic cells, limiting therefore Th1 cell development. Indeed, depletion of HIF-1α in CD11c+ cells resulted in higher and sustained expression of IL-12 and complete abrogation of IL-10. Moreover, CD11c-specific HIF-1α-deficient mice showed higher frequencies of IFN-γ-producing CD4 T cells in the spleen and bone marrow and, consequently, a significantly reduced parasite burden in both organs. Taken together, our results suggest that HIF-1α expression in dendritic cells largely contributes to the establishment of persistent Leishmania infection and may therefore represent a possible therapeutic target.