Emergence and Persistence of CXCR4-Tropic HIV-1 in a Population of Men from the Multicenter AIDS Cohort Study.

We examined the emergence of CXCR4 (i.e., X4) tropism in 67 male human immunodeficiency virus type 1 (HIV-1) seroconverters from the Multicenter AIDS Cohort Study (MACS) who were selected to reflect the full spectrum of rates of HIV-1 disease progression. A mean of 10 serial samples per donor were evaluated by a laboratory-validated, commercially available assay to determine phenotypic coreceptor use.Atotal of52%ofmen had dual- or mixed-tropic HIV-1 detected at 1 or more of the time points tested. Use of X4 by HIV-1 was detected more frequently among men who developed AIDS (defined as a CD4⁺ T cell count of <200 cells/μL and/or an AIDS-defining illness)⩽11 years after seroconversion thanamongthosewhodid not (P = .005), as well asamong men who exhibited a total T cell count decline (i.e., a CD3⁺ inflection point), compared with those who did not (P = .03). Formen in whom both X4 virus and an inflection point were detected, emergence of X4 virus preceded the inflection point by a median of 0.83 years. The median CD4⁺ T cell count at first detection of X4 viruses before the onset of AIDS was 475 cells/μL. We conclude that HIV-1 variants that used X4 frequently emerged at high CD4⁺ T cell counts and may contribute to the decrease in T cell numbers during late HIV-1 infection. [ABSTRACT FROM AUTHOR]