Modulation of T activation by SIVsmm nef alleles. (A) PBMCs were transduced with replication-competent VSV G pseudotyped HIV-1 particles expressing either GFP alone (panel 1) or together with the HIV-1 NL4-3 and NA7 (panels 2 and 3), 239 wt (panel 4) or SIVsmm nef alleles (panels 5 to 12) and stained for CD69 and CD25 expression. Similar results were obtained in two independent experiments. (B) CD69 and CD25 expression levels on PBMCs infected with HIV-1 constructs coexpressing eGFP and the indicated nef alleles are shown relative to those measured on T cells transduced with the nef defective control virus (100%). Values give averages ± SD derived from three independent experiments. The asterisks denote a statistical significance (P < 0.05) between HIV-1 and SIV Nef activity.