Racial differences in rate of CD4 decline in HIV-1-infected homosexual men

Objective: To determine whether racial differences exist in the rate of CD4 lymphocyte decline in HIV-1-infected homosexual men. Design: Prospective cohort study. Study population: Non-Hispanic white (n = 321) and black (n = 102) HIV-1-seropositive homosexual and bisexual men were recruited from the Baltimore/Washington, DC metropolitan areas between 1984-1985 and 1987-1990, and evaluated semiannually Main measurements: Changes in CD4 lymphocyte count and CD4 percentage over time were analysed using linear regression methods for the 271 white and 69 black participants who had at least four semiannual CD4 lymphocyte measurements. Results: Rate of decline in CD4 lymphocyte count over 6 months was much slower among black than white seroprevalent men at all levels of baseline CD4 count (baseline 201-400 x 10⁶/l: +0.24 versus -17.7 x 10⁶/l; 401-600 x 10⁶/l: -11.3 versus -23.9 x 10⁶/l; 601-800 x 10⁶/l: -15.1 versus -35.2 x 10⁶/l; > 800 x 10⁶/l: -4.3 versus -42.7 x 10⁶/l for black versus white, respectively), although this was only statistically significant for the lowest and highest strata of baseline CD4 count. These racial differences persisted after adjustment for recruitment period (1984-1985 or 1987-1990), follow-up duration, age and zidovudine therapy or Pneumocystis carinii pneumonia prophylaxis. Similar findings were observed among the 70 white and 11 black seroconverters. Black participants were also less likely than a subgroup of white participants matched on baseline CD4 lymphocyte count to be HIV-1 p24 antigen-positive. However, after acid dissociation of samples initially p24 antigen-negative, there were no significant differences in the prevalence of p24 antigenemia at enrollment or after 1 year of follow-up. Conclusions: This analysis suggests a more gradual decline in CD4 lymphocyte count among black than white Americans. The clinical significance of and reasons for this are unclear, but the lower prevalence of p24 antigenemia due to immune complexing among black Americans suggests that racial differences in the immune response to HIV may exist. Additional studies are needed to validate these findings in a larger cohort of non-whites, and to assess their relationship with other measures of cell-mediated immune function.