FIG. 1.

Analysis of coreceptor expression and Env-mediated fusion of PHA-activated PBMCs isolated from CCR5^+/+ (+/+), CCR5^+/− (+/−), or CCR5^−/− (−/−) individuals (n = 25/genotype). The PBMC samples were washed twice with PBS and then sequentially stained with PE-conjugated anti-CCR5 monoclonal antibody (3A9) or its isotype-matched control; washed and then stained with FITC-conjugated anti-CD4 monoclonal antibody or its isotype-matched control; and washed and then stained with APC-labeled anti-CXCR4 monoclonal antibody or its isotype-matched control. The MFIs of CCR5 and CXCR4 expression were measured by gating on the CD4⁺ population (A and B). The coreceptor expression index represents the MFI of the coreceptor staining divided by the MFI value obtained with the isotype control. (C and D) HIV-1 Env-mediated fusion with PBMC samples stained for the analysis shown in panels A and B. PHA-activated PBMCs expressing T7-lacZ were mixed with Env-expressing cells containing T7 RNA polymerase and incubated for 2.5 h at 37°C. The ability of the PBMCs to undergo cell fusion with R5 (C) or X4 (D) Env was quantified by measuring β-galactosidase (β-gal) produced. The broken line indicates the average background value obtained with the uncleaved Env (Unc) control. The indicated P values were calculated using the Student t test. The identities of the HIV⁺ CCR5^−/− samples are indicated on the right side.