Low-frequency drug-resistant HIV-1 and risk of virological failure to first-line NNRTI-based ART : a multicohort European case-control study using centralized ultrasensitive 454 pyrosequencing.

Objectives: It is still debated if pre-existing minority drug-resistant HIV-1 variants (MVs) affect the virological outcomes of first-line NNRTI-containing ART. Methods: This Europe-wide case-control study included ART-naive subjects infected with drug-susceptible HIV-1 as revealed by population sequencing, who achieved virological suppression on first-line ART including one NNRTI. Cases experienced virological failure and controls were subjects from the same cohort whose viraemia remained suppressed at a matched time since initiation of ART. Blinded, centralized 454 pyrosequencing with parallel bioinformatic analysis in two laboratories was used to identify MVs in the 1%-25% frequency range. ORs of virological failure according to MV detection were estimated by logistic regression. Results: Two hundred and sixty samples (76 cases and 184 controls), mostly subtype B (73.5%),were used for the analysis. Identical MVs were detected in the two laboratories. 31.6% of cases and 16.8% of controls harboured pre-existing MVs. Detection of at least one MV versus no MVs was associated with an increased risk of virological failure (OR=2.75, 95% CI=1.35-5.60, P=0.005); similar associations were observed for at least one MV versus no NRTIMVs (OR=2.27, 95% CI=0.76-6.77, P=0.140) and at least oneMV versus no NNRTIMVs (OR=2.41, 95% CI=1.12-5.18, P=0.024). A dose-effect relationship between virological failure and mutational loadwas found. Conclusions: Pre-existing MVs more than double the risk of virological failure to first-line NNRTI-based ART