Background:  Whether differences exist in the natural history of distinct HIV-1 clades is debated. Confounding the question are socioeconomic and genetic factors that differ between groups harboring different viral clades which may influence disease progression.

Methods:  We conducted a retrospective cohort study at a university HIV clinic between 1996 and 2007. We compared Canadian/Europeans (CAN; clade B), with recent immigrants/refugees from Haiti (clade B) and Sub-Saharan Africans (clade non-B) to determine whether there were differences in disease progression attributable to viral clade. The rate of CD4 decline prior to initiation of ART was determined in all ART-naïve subjects with at least 2 CD4 measures using mixed linear regression models adjusting for age, sex, time since HIV diagnosis, and baseline CD4 cell count, HIV RNA, nutritional status (e.g., albumin, hemoglobin) and calendar year. Time to first AIDS-defining illness from first clinic visit was compared between groups using adjusted Cox proportional hazards models.

Results:  We studied 295 CAN, 45 Haitians, and 121 Africans for a median of 258 days (2 to 4014 days). Africans and Haitians were more likely to be female, had lower albumin and hemoglobin, and shorter HIV duration than CAN. At baseline, median absolute CD4 cell counts were lower among Africans:  278 vs 352 and 364 cells/μL in CAN and Haitians, respectively. CD4 percentage was similar in the 3 groups (22%, 24%, and 20%). Median HIV RNA was significantly lower in Africans:  3.89 vs 4.55 and 4.10 log copies/mL in CAN and Haitians (p <0.001). The adjusted slope of CD4 decline was significantly less steep for Africans (–0.93%/year, 95%CI –1.8 to –0.1) than both CAN (–1.54%/year, 95%CI –2.3 to –0.8) and Haitians (–1.61%/year, 95%CI –2.1 to –1.1); p = 0.04. Africans also progressed more slowly to AIDS (adjusted HR 0.34, 95%CI to 0.11, 0.97 compared with CAN and Haitians). Of the 461 patients, 241 had clade assignments supporting that the CAN and Haitians were infected with clade B (97%) and Africans with non-clade B viruses (96%).

Conclusions:  Despite having similar demographic, socioeconomic, and nutritional status, Africans infected with non-B clade HIV had slower rates of disease progression than Haitians with clade B viruses. Haitians in turn exhibited similar disease progression to CAN who shared the same clade. Our findings suggest that clade may be an important predictor of HIV natural history in a developed medical setting.