Presence of RT functional domains from HIV-1 subtype C isolates correlates with decreased level of viral DNA integration. A - Integration of cDNA of NL4-3 or NL-based viruses carrying protease and RT polymerase domains from subtype C isolates in Sup-T1 cell DNA at 24 h p.i. Cells were infected as described in the legend to Figure 5B. Total DNA was harvested and relative amounts of proviral DNA were measured using two-step Alu-based nested PCR assays as described in Materials and methods. Levels of provirus are shown as percentages of the maximum levels of integration detected in cells infected with NL4-3. Error bars show the standard deviation of three independent viral preparations. B -Integration of the backbone NL4-3 and chimeric viruses in Sup-T1 cells at 24 and 48 h p.i. DNA from the infected cells was harvested and subjected to quantitative real-time PCR as described in A. Levels of proviral DNA are shown as percentage of those detected in cells infected with NL4-3 at 48 h p.i. Results are mean ± SD of three independent experiments.