K65R MUTATION OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 REVERSE-TRANSCRIPTASE ENCODES CROSS-RESISTANCE TO 9-(2-PHOSPHONYLMETHOXYETHYL)ADENINE

Cloned variants of human immunodeficiency virus type 1 that contain th e K65R mutation in reverse transcriptase have previously been shown to display approximately 10- to 30-fold resistance against 2',3'-dideoxy cytidine, 2',3'-dideoxyinosine, and 2',3'-dideoxy-3'-thiacytidine. On the basis of tissue culture studies with both primary T cells and esta blished cell lines, we now report that the K65R mutation confers appro ximately 12- to 15-fold resistance to 9-(2-phosphonylmethoryethyl)aden ine (PMEA). Likewise, a chain termination system revealed that mutated recombinant K65R reverse transcriptase displays resistance to PMEA di phosphate, the active metabolite of PMEA, in cell-free enzyme assays. Parallel studies have shown that the M184V mutation in reverse transcr iptase, associated with high-level resistance against the (-) enantiom er of 2',3' dideoxy-3'-thiacytidine, does not confer resistance to PME A in tissue culture. Viruses and enzymes that included both the K65R a nd M184V mutations were resistant to PMEA and PMEA diphosphate, respec tively, but only to the extent conferred by the K65R mutation alone.