Effect of HIV type 1 subtype on virological and immunological response to combination antiretroviral therapy: evidence for a more rapid viral suppression for subtype A than subtype B-infected Greek individuals.

Whether response to combination antiretroviral therapy (cART) differs between those infected with HIV-1 subtype A or B remains unclear. We compared virological and immunological response to cART in individuals infected with subtype A or B in an ethnically homogeneous population. Data derived from the Athens Multicenter AIDS Cohort Study (AMACS) and analysis were restricted to those of Greek origin. Time to virological response (confirmed HIV-RNA <500 copies/ml) and time to failure (>500 copies/ml at any time or no response by month 6) were analyzed using survival models and CD4 changes after cART initiation using piecewise linear mixed effects models. Of the 571 subjects included in the analysis, 412 (72.2%) were infected with subtype B and 159 (27.8%) with subtype A. After adjusting for various prognostic factors, the rate of virological response was higher for those infected with subtype A versus B (adjusted HR: 1.35; 95% CI: 1.08-1.68; p=0.009). Subtype A was also marginally associated with a lower hazard of virological failure compared to subtype B (HR=0.73; 95% CI: 0.53-1.02; p=0.062). Further adjustment for treatment adherence did not substantially changed the main results. No significant differences were observed in the rates of CD4 increases by subtype. The overall median (95% CI) CD4 increase at 2 years of cART was 193 (175, 212) cells/μl. Our study, based on one of the largest homogeneous groups of subtype A and B infections in Europe, showed that individuals infected with subtype A had an improved virological but similar immunological response to cART compared to those infected with subtype B.