Herpes simplex virus type 2 UL24 gene is a virulence determinant in murine and guinea pig disease models

A herpes simplex virus type 2 (HSV-2) UL24 beta-glucuronidase (UL24-beta gluc) insertion mutant was derived from HSV-2 strain 186 via standard marker transfer techniques. Cell monolayers infected with UL24-beta gluc yielded cytopathic effect with syncytium formation. UL24-beta gluc replicated to wild-type viral titers in three different cell lines. UL24-beta gluc was not virulent after intravaginal inoculation of BALB/c mice in that all inoculated animals survived doses up to 400 times the 50% lethal dose (LD50) of the parental virus. Furthermore, few UL24-beta gluc-inoculated mice developed any vaginal lesions. Intravaginal inoculation of guinea pigs with UL24-beta gluc at a dose equivalent to the LD50 of parental virus (approximate to 5 x 10(3) PFU) was not lethal (10/10 animals survived). Although genital lesions developed in some UL24-beta gluc-inoculated guinea pigs, both the overall number of lesions and the severity of disease were far less than that observed for animals infected with parental strain 186.