CXCR4-tropic (X4) HIV-1 variants are associated with faster disease progression compared with CCR5-tropic variants; however, the mechanism for this is unclear. We measured T-cell activation in 120 individuals with primary HIV-1 infection. X4-utilizing variants, determined genotypically, were present in 8.3% of the participants and were associated with higher levels of CD4 T-cell activation, even after adjusting for other prognostic factors. Increased CD4 T-cell activation may influence the more rapid immunological decline associated with X4 virus.
