Characteristics of herpes simplex virus resistance to disodium phosphonoacetate.

Herpes simplex virus (HSV), which was partially resistant to the inhibitory effect of disodium phosphonoacetate (PAA), could be recovered following four virus passages in the presence of 100 microgram/ml PAA. Resistant strains were isolated from both HSV type 1 and HSV type 2. Virus resistance to PAA was not complete, and in most isolations a significant proportion of the virus stock remained susceptible to the drug. Resistance was shown to be heritable and persisted through virus passage and cloning experiments. PAA inhibited the replication of virus-specific DNA in sensitive strains of HSV but not in resistant strains of HSV. In vitro experiments directly demonstrated that PAA inhibited the activity of the virus-specific DNA polymerase 10 times more effectively in PAA-susceptible HSV than in PAA-resistant HSV. The treatment of HSV-infected mice with high levels of PAA did not induce the formation of resistant virus strains.