Genetic barrier for attachment inhibitor BMS-626529 resistance in HIV-1 B and non-B subtypes

The genetic barrier (defined as the number of genetic transitions/transversions needed to produce a resistance mutation) can differ between HIV-1 subtypes. The genetic barrier for the new attachment inhibitor BMS-626529 was evaluated in five HIV-1 subtypes. Nine substitutions associated with BMS-626529 resistance at seven amino acid positions (116, 204, 375, 426, 434, 475 and 506) were analysed in 300 nucleotide sequences of the env gene encoding the gp120 protein from antiretroviral-naive patients (60 for each subtype and recombinant: B, C, D, CRF01_AE and CRF02_AG). Differently from the B subtype, some resistance mutations were found as natural polymorphisms in the C and D subtypes and the CRF02_AG and CRF01_AE recombinants for four positions of the env gene encoding the gp120 protein (375, 426, 434 and 475). The majority (five out of seven) of amino acid positions studied (116, 426, 434, 475 and 506) were relatively conserved (>63%) between the five HIV-1 subtypes, leading to a similar genetic barrier to mutations associated with resistance to BMS-626529. However, at positions 116 and 506 a minority of C and CRF02_AG subtypes had codons leading to a higher genetic barrier. Different predominant codons were observed at two out of seven positions (204 and 375) between the subtypes, with no effect on the calculated genetic barrier. However, for position 375, a minority of CRF02_AG sequences showed a lower genetic barrier to S375M/T resistance mutations. In non-B HIV-1 subtypes, four out of seven studied positions presented mutations implicated in BMS-626529 resistance. Despite great variability of the HIV-1 envelope, there was no major impact of polymorphisms on the genetic barrier to acquisition of BMS-626529 resistance.