FIG 3.

HIV-1 transmission requires Env receptor- and actin-dependent interactions. (A) Preincubation of CD4⁺ T cells with blocking anti-CD4 (13B8.2) or anti-CCR5 (2D7) antibody (10 μg/ml) or preincubation of HIV-1_BaL-infected MDM with anti-gp120 (2G12 or b12; 10 μg/ml) after Fc block resulted in a significant reduction in HIV-1 transfer to CD4⁺ T cells during 3 h of coculture. All MAbs were maintained during coculture. Transfer was measured by flow cytometry (FACSCalibur) of aspirated CD4⁺ T cells stained for CD3 and HIV-1 Gag, expressed as a percentage of the CD3⁺ Gag⁺ cells in relevant isotype (mouse or human) control wells. (B) Preincubation of CD4⁺ T cells with blocking anti-LFA-1 (L130 n = 5 donors) or preincubation of HIV-1_BaL-infected MDM with anti-ICAM-1 (LB-2; n = 5 donors), ICAM-2 (B-T1; 10 μg/ml), or ICAM-3 (101-1D2; 10 μg/ml; both n = 2 donors) after Fc block followed by assessment of HIV-1 transfer to CD4⁺ T cells during 3 h of coculture with HIV-1_BaL-infected MDM. All MAbs were maintained during coculture. Transfer was measured as described for panel A and expressed as a percentage of the CD3⁺ Gag⁺ cells in isotype control wells. Bars, means ± SEM. ***, P < 0.001 by ANOVA with Dunnett's posttest.