Objectives: To study the effect of human T-cell lymph-tropic virus type I (HTLV-I) on markers of human immunodeficiency virus (HIV) disease progression.
Design: A retrospective, nested case-control study.
Setting: A university hospital outpatient HIV clinic in Rio de Janeiro, Brazil.
Participants: Human immunodeficiency virus-seropositive adults participating in a prospective HIV cohort study.
Main outcome measures: The HIV clinical stage, CD4+ lymphocyte counts, and other laboratory parameters in 27 individuals infected with HIV and HTLV-I (coinfection) and 99 age-matched, HIV-seropositive, HTLV-seronegative controls (single infection).
Results: Variables independently associated with coinfection included higher CD4+ lymphocyte count (odds ratio [OR], 2.3; 95% confidence limits [CL], 1.3, 4.1), higher CD4+ percentage (OR, 2.0; 95% CL, 1.3, 3.2), beta 2-microglobulin level of 254 nmol/L or more (OR, 6.8; 95% CL, 1.3, 35.4), World Health Organization stages 3 and 4 (OR, 4.4; 95% CL, 1.1, 18.0), and reporting a parenteral risk factor (OR, 7.4; 95% CL, 1.4, 38.9). When stratified by p24 antigenemia, coinfection was associated with an estimated 82% higher CD4+ lymphocyte count (P < .05).
Conclusion: Coinfection was associated with higher CD4+ lymphocyte counts, more advanced clinical disease, and higher beta 2-microglobulin levels than HIV infection alone. The higher mean CD4+ lymphocyte count does not appear to offer immunologic benefit. Caution should be exercised when using CD4+ lymphocytes as a surrogate marker in studies of HIV infection in populations where HTLV-I is prevalent. Further studies are needed to address whether current CD4+ lymphocyte values for the initiation of antiretroviral therapy and chemoprophylaxis against opportunistic infections in HIV infection are appropriate in coinfection.