The acyclic
nucleoside 9-(1,3-dihydroxy-2-propoxymethyl)guanine (
DHPG) was evaluated for its efficacy in protecting guinea pigs from primary and recrudescent
infections of herpes simplex virus type 2. Vaginally infected guinea pigs were treated twice a day with
DHPG at 25 mg/kg per dose for 3 weeks. Subcutaneous doses were started 3 h, 24 h, or 5 weeks after virus inoculation. Treatment starting at 3 or 24 h reduced the severity of the primary
infection by greater than 70% when lesions were graded for 3 weeks; lesion duration was lessened by greater than 55%. For 6 weeks
after treatment, the number of recrudescent lesions was reduced by greater than 60%, and the duration of the recrudescences declined by greater than 40%. When dosing was started at 3 h postinfection, 33% of the animals did not develop any sign of primary or recrudescent
infection throughout the 9-week test. By comparison, all the animals treated with
DHPG starting at 24 h or with saline became infected. A 3-week
DHPG regimen starting 5 weeks postinfection reduced the number of animals that developed recrudescent lesions by 70%. When treatment ended, however, recrudescent episodes in the animals increased to the level of saline-treated controls. These results suggest that (i)
DHPG is highly effective in reducing the severity of both primary and recrudescent lesions of herpes simplex virus type 2, (ii) early treatment of a primary
infection or treatment of recrudescences reduces the incidence of recrudescences, and (iii) the
drug appears to have no effect on the latent form of the virus, as the incidence of recrudescences increases when
DHPG treatment is ended.