TNFR1 plays a critical role in the control of severe HSV-1 encephalitis

Herpes simplex virus-1 (HSV-1) is a pathogen for humans that may cause severe encephalitis. Tumor necrosis factor α (TNF-α) plays a role in several viral diseases of the central nervous system (CNS). The classic proinflammatory activities of TNF-α are mediated mainly through activation of the receptor 1 for TNF-α (TNFR1). However, when HSV-1 is inoculated in the periphery, TNF-α seems to protect C57Bl/6 mice against encephalitis by a mechanism independent of TNFR1. This study aims to investigate the role of TNFR1 in HSV-1 encephalitis induced by the inoculation of the virus into the brain. Wild-type C57BL/6 (WT) and TNFR1^-/- were inoculated with 10² plaque-forming units of HSV-1 by the intracranial route. Infection with HSV-1 was lethal in TNFR1^-/- mice in early times after infection. TNFR1^-/- mice had reduced expression of the chemokines CCL3 and CCL5, and decreased leukocyte adhesion in the brain vasculature compared to WT mice 4 days post-infection (dpi). At this time point TNFR1^-/- infected mice also had higher HSV-1 viral replication and more injuries in the brain, especially in the hippocampus. In conclusion, TNFR1 seems to play a relevant role in the control of viral replication in the CNS when HSV-1 is inoculated by intracranial route.