Different rates of disease progression of HIV type 1 infection in Tanzania based on infecting subtype

Background. Many different subtypes of human immunodeficiency virus (HIV) type 1 have been identified, particularly in sub-Saharan Africa. However, much remains unknown regarding the relative pathogenicity of these subtypes and their influence on the clinical progression of HIV infection. We examined prospectively the associations between HIV-1 subtypes A, C, and D and recombinant viruses, as well as the rates of disease progression in a cohort of seropositive women from Dar es Salaam, Tanzania. Methods. A total of 428 pregnant mothers participating in a larger controlled trial of the effect of vitamin supplements were selected for DNA sequencing of their HIV-1 subtype. Plasma viral load was measured at baseline, and CD4+ cell counts was assessed at baseline and at regular intervals throughout the follow-up period. Proportional hazards regression (hazards ratio [HR]) analysis was used to measure the association between viral subtype and the rate of disease progression. Results. Relative to patients with subtype A, patients with subtype D experienced the most rapid progression to death (HR, 2.27; 95% confidence interval [CI], 1.46-3.52) or to the World Health Organization stage 4 of illness (HR, 1.94; 95% CI, 1.20-3.14) and to a CD4+ cell count of <200 cells/mm3 (HR, 2.12; 95% CI, 1.42-3.17). After adjustment for viral load, CD4+ cell count, and other baseline covariates, the associations remained similar. Conclusions. We observed heterogeneity in the rates of disease progression of HIV-1 disease in infected persons, on the basis of the infecting subtype. Subtype D was associated with the most rapid progression of the disease, relative to the other 3 categories of viruses in our cohort. © 2006 by the Infectious Diseases Society of America. All rights reserved.