Isolation and characterization of herpes simplex virus resistant to nucleoside analogs.

Herpes simplex virus type 1 was isolated from nine patients with herpes labialis who were not previously exposed to any antiviral agent. A significant variation in the growth of these isolates in BSC1 cells in the presence of 5-iodo-2'-deoxyuridine and acyclovir was observed. One of the isolates was highly resistant to 5-iodo-2'-deoxyuridine and acyclovir and failed to induce significant activity of thymidine kinase in cultures. Herpesvirus reisolated from the same patient 3 1/2 years later did not show significant changes in its resistance to acyclovir, suggesting that the patient has a latent infection with a drug-resistant virus.