Genetic analysis of culture-negative UNAIDS subtype C samples.

To help in the vaccine development, WHO-UNAIDS launched a program for the isolation and characterization of subtype C viruses, the most prevalent HIV-1 subtype in the world. Isolates were obtained from Brazil, China, India, Israel, and South Africa, countries in which these strains are circulating. In this study we genetically characterized a set of samples displaying the culture-negative phenotype by sequencing the nucleotides of three genomic regions: the p17 region of the gag gene, the C2V3C3 fragment of the env gene, and the nef gene. The association of the culture-negative phenotype with the nef gene was studied, and we found a significant accumulation of gene alterations. Except for one B/C recombinant from India, the samples studied formed a monophylogenetic subtype C clade, although samples from Brazil formed a statistically significant, independent subcluster in two of the three genes analyzed.