NINJ1 blocks HSV-1 entry into macrophages to impact viral replication and immunity

Restriction factors block multiple stages of viral infection. Here we describe how Ninjurin1 (NINJ1) controls HSV-1 infection of macrophages, a key cell type that protects mice against infection. We observe that Ninj1^-/- mouse macrophages are more susceptible to HSV-1 infection than WT cells. Given the role of NINJ1 during cell death, we investigate whether its antiviral activity is linked to this function. Surprisingly, we do not observe differences in cell death at early timepoints post HSV-1 infection between genotypes. Instead, we attribute the higher infection rate of Ninj1^-/- macrophages to enhanced entry, with more viral particles entering each cell and a greater fraction of infected cells. The increased viral loads in Ninj1^-/- cells result in higher ISG and cytokine RNA expression, which we ascribe to both TLR signaling and STING-mediated recognition. Cytokine secretion, however, is severely dampened in infected Ninj1^-/- cells, pointing to greater viral replication suppressing the induction of inflammation. In conclusion, NINJ1 acts as a gatekeeper for HSV-1 entry in macrophages, impacting the inflammatory phenotype associated with HSV-1 infection.