Abstract
DBA/2 and C57B1/6 mice were infected intraperitoneally with two different strains of herpes simplex virus type 1, HSV-1 ANG and HSV-1 WAL. Unlike HSV-1 WAL, HSV-1 ANG was apathogenic by this mode of infection. Furthermore, infection with HSV-1 ANG protected mice of both inbred strains against infections with lethal doses of pathogenic HSV-1 WAL. This protection was observed when the apathogenic virus was given with the pathogenic virus or 4 to 24 h before it.