Serologic and phylogenetic characterization of HIV-1 subtypes in Uganda

To determine the HIV genetic subtypes present in HIV-1-infected asymptomatic blood donors in Uganda and to evaluate serologic detection of infection by commercial immunoassays; to evaluate samples for HIV-1 group O infections.

Sixty-four HIV-seropositive plasma samples were collected from the Nakasero Blood Bank, Kampala, Uganda. The plasma were evaluated using commercial HIV enzyme immunoassays (EIA) and a research immunoblot. HIV-1 group M and O infections were identified on the basis of discordant seroreactivity in EIA and reactivity to group M and O antigens on the immunoblot. Regions of gag p24 and env gp41 were amplified using reverse transcriptase polymerase chain reaction, and genetic subtypes were determined by phylogenetic analysis.

Serologic testing confirmed that 63 out of 64 plasma units were positive for HIV-1 group M infection and showed no evidence of HIV-1 group O infections. Genetic subtyping determined that 25 samples were subtype A, three subtype C, 22 subtype D, and nine were heterogeneous for subtypes A and D.

Despite the sequence variation observed in Uganda, commercial EIA based on HIV-1 subtype B proteins detected all the infections. In contrast, a peptide-based assay failed to detect three infections by subtype D viruses. This emphasizes the negative impact of HIV genetic variation on assays that rely on peptides to detect HIV infections. The number of infections with heterogeneous subtype (due to mixed infections or recombinant viruses) is high and reflects the growing complexity of the HIV epidemic in endemic regions where multiple subtypes are present in the population.