HIV-1 subtype C reverse transcriptase sequences from drug-naive pregnant women in South Africa.

The HIV-1 reverse transcriptase genes from 37 HIV-1-positive pregnant women attending an antenatal clinical in Soweto, South Africa were sequenced and analyzed for the presence of drug resistance mutations. All women were antiretroviral drug naive, but were being screened as potential participants in clinical trials of antiretroviral drugs aimed at preventing mother-to-child transmission. Sequence analysis revealed that all belonged to HIV-1 subtype C, the predominant subtype among heterosexual populations in South Africa. Twenty-three amino acid loci associated with resistance to zidovudine, lamivudine, didanosine, stavudine, and nevirapine were examined and found not to encode mutations that would confer resistance to these drugs. Polymorphisms at these loci occurred infrequently, with three patients harboring the A98S and V179I polymorphisms. An additional three patients harbored V118I, which can function as an accessory resistance mutation, but in this context is also likely to be a polymorphism. These data show that pregnant women who are candidates for receiving antiretroviral drug therapies do not contain naturally occurring or preexisting drug resistance mutations and that such drug therapies are likely to be highly effective in this setting.