Figure 2.

CD4⁺ T cell depletion patterns in CCR5- (A) versus CXCR4-tropic (B) SIV infection. (A) PBMCs from a typical WT SIVmac239-infected normal progressor were examined for their correlated expression of cell surface CD4 versus CCR5 versus CD28 versus CD95 or CD4 versus CCR5 versus Ki-67 versus CD95, both before and 49 d after infection (viral load = 7.4 × 10⁶ copies/ml and absolute blood CD4 counts = 500 cells/μl at day 49 after infection). 5,000 events, gated on total CD4⁺ T cells (left and middle) or CD4⁺ (CD95^high) memory T cells (right) are shown. Overall, naive (blue) and memory (red) T cell frequencies are shown in the upper right corner of the left panels. The percent CCR5⁺ within the memory subset is shown in the middle panels, and the memory subsets defined by CCR5 versus Ki-67 are shown in the right panels. Note the striking relative depletion of CD4⁺ memory T cells, and within the memory population, the CCR5-expressing subset, with this subset going from predominantly Ki-67⁻ preinfection to predominantly Ki-67^bright+ postinfection (arrows). (B) PBMCs from a representative SIVmac155T3-infected RM were examined for their correlated expression of cell surface CD4 versus CCR5 versus CD28 versus CD95 or CD4 versus CXCR4 versus CD28 versus CD95, both before and 49 d after infection (viral load = 1.2 × 10⁵ copies/ml and absolute blood CD4 count = 440 cells/μl at day 49 after infection). 5,000 events, gated on total CD4⁺ T cells are shown with events within the naive and memory cell clusters colored blue and red, respectively. Note the profound loss of naive CD4⁺ T cells, increased frequencies of CCR5⁺ cells among CD4⁺ memory T cells, and loss of CD4⁺ T cell CXCR4 staining intensity, particularly within the memory subset.