Characterization of a Mutant HIV-1 Reverse Transcriptase Resistant to (+)-(5S)-4,5,6,7-tetrahydro-5-methyl-6-(3-methyl-2-butenyl)-imidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-thione (TIBO R82150)

A virus strain resistant to R82150, a non-nucleoside reverse transcriptase (NNRT) inhibitor (tetrahydro-imidazo [4,5, 1-jk] [1,4] benzodiazepine-2(1H)-thione), was isolated following serial passage of HIV-1 RF in CEM-SS cells. The virus is cross-resistant to another non-nucleoside reverse transcriptase inhibitor, TGG-II-23A [1,4-dimethyl-1-[5,5-dimethyl-2-oxazoionyl]-naphthalen-2-one), but remains susceptible to AZT, DDI, D4T and phosphonoformate (PFA). DNA sequencing of reverse transcriptase genes from resistant virus indicated that R82150 selects for amino acid alterations Y181C and V108I. In vitro mutagenized reverse transcriptase and recombinant HIV-1 (pNL4-3) carrying either of the mutations have been generated. Genotypic and phenotypic analyses identified V108I as an unreported R82150-associated mutation. Both reverse transcriptase and viral resistance assays indicated that the resistance conferred by the V108I mutation is 7-fold less than that conferred by Y181C.