T cell restricted Notch signaling contributes to pulmonary Th1 and Th2 polarization during Cryptococcus neoformans infection

Abstract

Abstract Notch is a key signaling pathway regulating T cell development, activation and function. Notch signaling has been shown to affect the differentiation and functional responses of Th cells in several models of infectious disease and therapeutic targeting of Notch signaling has been proposed as treatments for autoimmune diseases. However, the contribution of Notch signaling to Th cell differentiation and responses during fungal infections is unknown. To elucidate the role of Notch signaling during fungal infections we infected mice expressing a dominant negative Notch inhibitor specifically within mature T cells with the fungal pathogen Cryptococcus neoformans. Inhibition of Notch resulted in impaired leukocyte recruitment, failure to control fungal burden in the lungs and failure to prevent dissemination to the CNS. Furthermore, we show that inhibition of Notch signaling impaired both protective Th1 and non-protective Th2 anti-cryptococcal immune responses. Leukocyte cultures and T cells from Notch deficient mice produced less IFN-γ, IL-5 and IL-13 than WT cells and had reduced expression of Th1 and Th2 associated transcription factors, Tbet and Gata3. Treatment with the Notch inhibitor DAPT did not impair cytokine production in WT cells indicating that Notch impacted the differentiation of these cells rather than biasing the magnitude of responses. Th17 responses were largely unaffected by Notch; although we also measured an increase in the frequency of Tregs in Notch deprived C. neoformans infected mice. Overall, these data suggest that Notch signaling controls the differentiation of Th1 and Th2 cells during C. neoformans infection and that targeting Notch may inadvertently render hosts more susceptible to fungal infections.