A quantitative study of the effects of several nucleoside analogues on established herpes encephalitis in mice.

Mice with established herpes encephalitis were used to compare the effects of chemotherapy using three different nucleoside analogues. Encephalitis was produced by intranasal inoculation of a type 1 strain of herpes simplex virus. Without chemotherapy all mice died within 5 to 7 days of inoculation. Oral acyclovir (ACV) was a successful preventative measure if commenced within 2 days of inoculation but much less effective if the onset of treatment was further delayed. From the third day, when central nervous system infection had definitely become established, ACV only reduced mortality if given intraperitoneally (i.p.) at regular 6-hourly intervals. Comparison with bromovinyldeoxyuridine (BVdU) and the new nucleoside analogue dihydroxypropoxymethylguanine (DHPG) using the same 6-hourly i.p. regimen revealed that BVdU was poorly effective, despite better activity in vitro, whereas DHPG was the most successful. Virus was rapidly eradicated from all parts of the brain by DHPG therapy, and by day 10, no infectious virus remained in the brains of treated mice, no virus antigens were observed and no trace of virus DNA could be detected in neural tissues by Southern blotting.