HIV-1 subtypes and response to combination antiretroviral therapy in Europe.

Background: Combination antiretroviral therapy (cART) may vary in ability to suppress viral load and increase CD4+ T-cell count in people infected with different HIV-1 subtypes, possibly due to differences in resistance development. Antiretroviral drugs have predominantly been developed in Western Europe/North America on the basis of the most prevalent subtype, B. However, non-B subtypes are increasingly spreading worldwide.

Objective: To compare virological and immunological response to cART between patients infected with B and non-B subtypes across Europe.

Design: EuroSIDA prospective, observational cohort with 11,928 HIV-1-infected patients.

Methods: Response to cART was analysed in patients with subtypes determined pre-cART, via multivariable logistic regression on the first measurements 6-12 months after starting cART. A virological response was defined as a viral load <500 copies/mi and immunological response as a CD4+ T-cell count increase of > or =100 cells/mm(3).

Results: Forty-five percent of patients were antiretroviral naive at initiation of cART. Virological suppression was achieved by 58% of 689 subtype-B-infected patients and 66% of 102 non-B-infected patients (P=0.159). After adjustment for potential confounders, there was no significant difference in odds of achieving virological suppression (non-B compared with B; odds ratio [OR]: 1.05, 95% confidence interval [CI]: 0.58-1.93, P=0.866). An immunological response was achieved by 43% of 753 B-infected patients and 48% of 114 non-B-infected patients (P=0.334). After adjustment, there was no significant difference in odds of an immunological response (OR: 1.17, 95% CI: 0.73-1.87, P=0.524).

Conclusions: There was no evidence of significant differences in virological or immunological response to cART between patients infected with HIV-1 B and non-B subtypes.