FIG. 3.

Infection of macrophages is CD4 dependent. (A) Cells were pretreated with 5 μg of anti-CD4 MAb (Leu3a) per ml for 30 min at room temperature. Treated and control cultures were infected with macrophagetropic HIV-1 ADA and T-lymphotropic HIV-1 LAI and HIV-1 NDK for 2 h at 37°C. In treated cultures, anti-CD4 antibody was present also during infection. Strong-stop DNA was amplified by using HIV-1-specific primers from the LTR R/U5 region. Amplification of the α-tubulin gene was used to control the amount of DNA in each sample. Dilutions of 8E5/LAI cells were used as standards. (B) Quantification of PCR products. After hybridization with the ³²P-labeled probe, the PCR bands were quantified by using an Instant Imager (Packard). Data show results of one representative experiment of three, each performed in duplicate. Standard deviations are shown as vertical bars.