Neutrophils promote mononuclear cell infiltration during viral-induced encephalitis.

Neutrophils are the first infiltrating cell population to appear within the CNS during infection with the neurotropic JHM strain of mouse hepatitis virus (JHMV). To determine whether neutrophils play a role in limiting acute JHMV infection, mice were depleted of neutrophils. Infection of neutropenic animals resulted in increased levels of virus replication and mortality compared with control mice. Furthermore, neutropenia resulted in significantly reduced mononuclear leukocyte infiltration possibly due to reduced loss of blood brain barrier integrity during acute JHMV infection. These data suggest that infiltrating neutrophils are crucial for limiting virus replication during acute JHMV infection, contribute to the loss of blood brain barrier integrity and play a role in shaping adaptive immunity within the CNS.