T-tropic infection of CD4^dimCD8^bright T cells. (A) SEB- or (B) anti-CD3/CD28–stimulated CD8⁺ T cells were infected with HIV-1 IIIB (CXCR4 isolate; ▪) or 302056 (CCR5 isolate; ▦). Expression of HIV was monitored by intracellular staining of p24. Positively selected CD4⁺ T cells were also infected, and intracellular expression of p24 was determined as a positive control. □ indicates uninfected cells. Values represent the mean intracellular p24 expression on respective gated cells from at least 2 donors performed in triplicates ± SD. (C) A representative histogram of p24 intracellular staining.