HIV viral load and CD4⁺ lymphocyte counts in subjects coinfected with HTLV-I and HIV-1

Reports indicate that there is a dissociation between markers of HIV disease progression and clinical stage among subjects coinfected with human T-cell lymphotropic virus type I (HTLV-I) and HIV. HTLV-I coinfection does not appear to affect HIV viral load, currently considered to be the best marker of HIV disease progression. We measured HIV RNA levels in stored serum samples from 23 subjects with coinfection and 92 subjects with HIV single infection and examined the correlation with the CD4⁺ lymphocyte count. Subjects were recruited from an ongoing HIV cohort study in Rio de Janeiro, Brazil. In both groups, CD4⁺ lymphocyte counts declined with increasing levels of HIV RNA. In a linear regression analysis adjusting for HIV RNA serum level, coinfected individuals had an estimated 78% higher CD4⁺ lymphocyte count than those with single infection. Simultaneous adjustment for β2-microglobulin level increased the difference, with coinfected individuals having 146% (p = 0.005, 95% CI: 32% to 359%) higher CD4⁺ counts. These data suggest that the higher CD4⁺ lymphocyte counts associated with coinfection do not provide immunologic benefit and may reflect HTLV-I- associated nonspecific lymphocyte proliferation. The results of this and other studies suggest that the CD4⁺ count cutoff values used in making clinical decisions in HIV infection may not be appropriate in coinfection. As with HIV single infection, HIV virus load may be the optimal surrogate marker for subjects with coinfection.