Functional characterization of HIV-2 nef alleles. (A) Schematic presentation of proviral HIV-1 IRES-eGFP constructs carrying HIV-2 nef alleles. (B to E) Quantitation of Nef-mediated downmodulation of CD4 (A), CD3 (C), CD28 (D), and MHC-I (E) on PBMCs infected with HIV-1 Nef/eGFP constructs. HIV-2 nef genes were grouped by VLs and are color coded as described for Fig. 1. Each symbol indicates the n-fold downmodulation of the indicated receptor molecule by one of the 45 different NL4-3 proviral recombinants expressing an HIV-2 nef allele. (F) Functional activity of HIV-2 nef alleles in up-modulating Ii (CD74) surface expression on THP-1 cells. (G to I) Expression of CD69 (G) and CD25 (H) and levels of apoptosis (I) in PBMCs infected with HIV-1 Nef/eGFP constructs. (J) Suppression of induction of NFAT in T-cell cultures infected with viral constructs expressing HIV-2 nef alleles. Values in panels B to K represent averages from triplicate experiments, and the horizontal bars indicate average activities per group. The results obtained for the HIV-1 Nef/eGFP control constructs are indicated by lines: red, NL4-3 nef; broken blue, HIV-2 BEN nef; and gray, disrupted nef gene. LTR, long terminal repeat.