Replication of HIV-1 subtype C env V3–V5 region chimeras in T-lymphocyte (A3.01) cell line. A3.01 cells (1 × 106 cells/well) were infected with equal amounts (RT counts) subtype C env chimeras (171 to 1014), parental HIV-1NL4-3 and HIV-1BaL. Virus production was measured by reverse transcriptase (RT) assay in culture media harvested every 3 days and the cells fed with appropriate media. The results are presented as cpm/ml ± SD of five separate triplicate experiments. The subtype C chimeras were unable to replicate in A3.01 cell line.