HIV-1 subtype C drug-resistance background among ARV-naive adults in Botswana.

Current HIV-1 antiretroviral (ARV) drug resistance knowledge is limited to HIV-1 subtype B (HIV-1B). We addressed whether unique genetic and phenotypic properties of HIV-1 subtype C (HIV-1C), southern Africa's most prevalent subtype, may foment earlier and/or distinct resistance mutations. Population-level HIV-1C genotypes were evaluated with respect to drug resistance prevalence before Botswana's public ARV treatment programme began. Viruses were genotyped from 11 representative districts of northern and southern Botswana, and consensus sequences from these 71 individuals and 51 previously reported sequences from HIV-positive blood donors were constructed. Phylogenetic analysis classified all 71 sequences but one, which exhibited pol gene mosaicism, as HIV-1C. The protease and reverse transcriptase coding region had no detectable known primary mutations associated with HIV-1B protease inhibitor (PI) drug resistance. Secondary mutations associated with PI drug resistance were found in all sequences. Several HIV-1C-specific polymorphic sites were found across the pol gene. Northern and southern Botswana viral sequences showed no significant differences from each other. Population genotyping shows that, without countrywide ARV treatment, HIV-1C-infected Batswana harbour virtually no primary mutations known to confer resistance to the three major HIV-1B ARV drug classes. Some secondary PI mutations and polymorphic sites in the protease enzyme necessitate continuous population monitoring, particularly after introduction of countrywide ARV treatment in Botswana. Although its PI resistance development rate and kinetics are not known, our data may suggest increased susceptibility and readiness of HIV-1C to develop resistance under drug pressure when the PI class of drugs is used.

Mutations and polymorphisms associated with antiretroviral drugs in HIV-1C-infected African patients.

To detect and characterize polymerase gene (pol) polymorphisms and mutation patterns in HIV-1C-infected Batswana patients treated with reverse transcriptase inhibitors, samples from AIDS patients treated with highly active antiretroviral therapy (HAART) were sequenced for the region encompassing the entire HIV-1 protease (PR) and the first 335 amino acids of reverse transcriptase (RT). Amongst the 16 patients treated with antiretroviral (ARV) drugs, eight started HAART regimens containing didanosine, stavudine and nevirapine (ddI/d4T/NVP) or efavirenz (EFV) (arm A) while the others started with zidovudine (AZT) and lamivudine (3TC) given together as combivir (CBV) with either NVP or EFV as arm B. Arm B is the first line regimen currently provided by the Botswana ARV national programme. Greater efficacy, in terms of treatment duration, was observed in patients in arm B (14 months) as compared with patients in arm A (9 months); P<0.05, n=8. Appearance of the M184V mutation in the arm B patients coincided with a rebound of viral load (VL) (4.3 +/-0.1 log10 RNA copies/ml) and a significantly improved immunological parameter (deltaCD4=207.0+/-48.1 cells/microl; P<0.05). Interestingly, patients developing the M184V mutation preferentially harboured polymorphisms Q174K and/or I178L located in close proximity to pol position 184. The M184V mutation occurred following a clear clinical benefit consisting of increased CD4 cell counts and lower plasma viral loads. Primary mutations known to be associated with NNRTI and NRTI resistance for HIV-1B were observed in 10 of the 16 treated patients.