A sensitive genotyping assay for detection of drug resistance mutations in reverse transcriptase of HIV-1 subtypes B and C in samples stored as dried blood spots or frozen RNA extracts.

Exposure to antiretroviral drugs in resource-constrained settings is likely to result in the emergence of drug-resistant HIV-1 variants, limiting treatment options. Genotypic drug resistance testing assists clinical management and outcomes assessment, but a sensitive and reproducible genotypic assay feasible for resource-constrained settings is needed. A sensitive, reproducible genotyping assay to detect HIV-1 drug resistance mutations in reverse transcriptase and protease was developed and validated using blood stored as dried blood spots or as frozen RNA extracts from Zambian children infected with subtype C. HIV-1 genotypes derived from samples stored as dried blood spots were compared to those derived from paired liquid plasma samples in American young adults infected with HIV-1 subtype B. The method reproducibly amplified patient-specific sequences and detected drug resistance mutations from all of the dried blood spots or excess frozen RNA extracts with detectable viremia over a broad range of viral loads (193-3 million HIV-1 RNA copies/mL) in both HIV-1 subtypes B and C infection. This method captured the genetic variation typical of HIV-1 infection, including mutations at usual sites of drug resistance, polymorphisms, and mixtures. This sensitive and reproducible genotypic assay is feasible for detection of antiretroviral resistance in resource-constrained settings.