Infection of CD4+-T-cell line CCRF-CEM with HIV-1BRU. (A and B) Cells were exposed to infectious virus at a multiplicity of infection of 2, heat-inactivated virus, or mock-infected cell supernatant. At 1 and 24 h postexposure, cells were fixed and permeabilized for intracellular p24 staining. Only cells exposed to the infectious virus stock showed detectable levels of p24 at 1 h postinfection (A) and increased p24 expression after 24 h (B). (C) Expression of HIV-1 RNA transcripts during infection. The graph depicts results for 17 HIV-1BRU infection experiments: a time course using CCRF-CEM cells and after 24 h of infection of CEMfh, CEMss, Jurkat, and SupT1 cells. Twelve PCR products representing different regions of the HIV-1BRU genome were spotted on each slide; nucleotide positions relative to the HIV-1BRU genome were 317 to 1281 (gag), 853 to 2471 (gag), 2179 to 3097 (pol), 3015 to 4363 (pol), 4337 to 5598 (pol), 5538 to 6974 (env), 6583 to 7404 (env), 7115 to 8631 (env), 8276 to 9225 (nef), 5402 to 5666 (tat), 7951 to 8272 (rev), 4619 to 5257 (vif), and 5124 to 5446 (vpr). Plotted are hybridization intensities of each of the 12 spots in the treated cells. HI (-) refers to mock infection versus heat-inactivated BRU, and HI (+) refers to heat-inactivated HIV-1BRU versus infectious HIV-1BRU.