Sequence analysis of reverse transcriptase genes of zidovudine (AZT)-resistant and -sensitive human immunodeficiency virus type 1 strains.

Sequential isolates of human immunodeficiency virus type 1 (HIV-1) were obtained from patients with AIDS on short and long term treatment with zidovudine (3'-azido-3'-deoxythymidine; AZT). The isolates were tested for resistance to zidovudine by monitoring the inhibition of syncytium formation, HIV-1-specific immunofluorescence and p24 production in C8166 cells. The reverse transcriptase (RT) genes of zidovudine-sensitive (< 1 microM) and -resistant (10 to 15 microM) strains were amplified using the polymerase chain reaction and the products were sequenced directly. The predicted amino acid sequences of the RTs of zidovudine-sensitive and -resistant isolates showed 95 to 97% identity to the corresponding sequence of HIV-1SF2 which was used as a reference. Amino acid changes at positions 41, 67, 70, 215 and 219 which are known to be associated with zidovudine resistance were present in some, but not all isolates exhibiting zidovudine resistance in vitro. This indicates that mutations in the RT of HIV-1, other than those already identified, may be involved in conferring resistance to zidovudine.