The mutation frequency of feline immunodeficiency virus enhanced by 3'-azido-3'-deoxythymidine.

We have developed a host range system to measure the mutation frequency of feline immunodeficiency virus (FIV), the feline homologue of human immunodeficiency virus type 1 (HIV-1). When wild-type FIV was grown in the presence of a known mutagen, 5-bromo-2'-deoxyuridine (BUdR), a dose-dependent increase of host range mutants was detected. Using this system, we have evaluated the effects of antiviral drugs upon the mutation frequency of FIV. Subinhibitory concentrations of 3'-azido-3'-deoxythymidine (AZT), the most common antiviral drug used in AIDS chemotherapy, increased the mutation frequency of FIV in a dose-dependent manner. Two other antivirals, 2',3'-dideoxyinosine (ddI) and 2'3'-dideoxycytidine (ddC), did not show this effect.