A variant of herpes simplex virus type 2 strain HG52 with a 1.5 kb deletion in RL between 0 to 0.02 and 0.81 to 0.83 map units is non-neurovirulent for mice.

The virulence of a deletion variant of herpes simplex virus type 2 (HSV-2) strain HG52 has been determined by intracranial inoculation of 3-week-old BALB/c mice. The variant JH2604 has a 1.5 kb deletion within each copy of the long repeat region (RL) of the genome between 0 to 0.02 and 0.81 to 0.83 map units. JH2604 is avirulent for mice compared to the parental wild-type virus, and fails to replicate in mouse brain in vivo. Correction of the deletion by marker rescue resulted in the isolation of recombinants which gave LD50 values comparable to those of individual plaque stocks of the parental HG52. Introduction of the deletion into wild-type virus resulted in recombinants which on intracranial inoculation of mice were avirulent. The results imply that sequences within the 3 kb terminal portion of RL are required for virulence of HSV-2 strain HG52.