Macrophages and microglia in HSV-1 infected mouse brain.

We have examined the macrophage and microglial cell response in mouse brains during the course of acute herpes simplex encephalitis produced by intranasal inoculation of virus. Macrophage infiltration and a microglial cell reaction were detected from 24 h after initial detection of HSV-1 antigen in brain. Macrophage infiltration was confined to focal areas of infection but the microglial cell reaction occurred in a more widespread distribution. Following disappearance of viral antigen, with resolution of the acute infection, macrophage infiltration and a focal microglial cell reaction remained for several weeks, providing a marker of sites of previous infection.