impedes CD40-dependent notch signaling to restrict Th polarization during infection.

Early Th responses are necessary to provide protection against (Mtb). Mtb impedes Th polarization by restricting CD40 co-stimulatory pathway on dendritic cells (DCs). We previously demonstrated that engaging CD40 on DCs increased Th responses. However, the molecular mechanisms that contributed to Th polarization were unknown. Here, we identify the Notch ligand DLL4 as necessary for Th polarization and demonstrate that Mtb limits DLL4 on DCs to prevent optimal Th responses. Although Mtb infection induced only low levels of DLL4, engaging CD40 on DCs increased DLL4 expression. Antibody blockade of DLL4 on DCs reduced Th polarization and . In addition, we show that the Mtb Hip1 protease attenuates DLL4 expression on lung DCs by impeding CD40 signaling. Overall, our results demonstrate that Mtb impedes CD40-dependent DLL4 expression to restrict Th responses and identify the CD40-DLL4 pathways as targets for developing new Th-inducing vaccines and adjuvants for tuberculosis.