Predictive value of HIV-1 replication capacity and phenotypic susceptibility scores in antiretroviral treatment-experienced patients.

OBJECTIVES: The aim of the study was to determine the prognostic value of HIV replication capacity (RC) for subsequent antiretroviral (ARV) treatment response in ARV-experienced patients. METHODS: RC and phenotypic resistance testing were performed at baseline and week 12 on plasma samples from patients randomized to undergo a 12-week ARV drug-free period (ARDFP) or initiate immediate salvage therapy (no-ARDFP group) in the Options in Management with Antiretrovirals (OPTIMA) trial. Dichotomous and incremental phenotypic susceptibility scores (dPSSs and iPSSs, respectively) were calculated. The predictive value of RC and PSS for ARV therapy response and/or ARDFP was evaluated using multivariate regression analysis and Pearson correlations. RESULTS: In 146 no-ARDFP subjects, baseline RC (50.8%) did not change at week 12 and was not correlated with CD4 cell count or viral load changes at week 12 (P=0.33 and P=0.79, respectively) or at week 24 (P=0.96 and P=0.14, respectively). dPSS predicted virological but not CD4 cell count response to ARV therapy at weeks 12, 24 and 48 (P=0.002, P<0.001 and P=0.005, respectively). RC was significantly correlated with dPSS and iPSS at baseline, but did not increase their predictive value. In the 137 ARDFP patients, RC increased significantly (from 52.4 to 85.8%), but did not predict CD4 cell count and viral load changes during ARDFP (P=0.92 and P=0.26, respectively). RC after ARDFP did not predict subsequent CD4 cell count and viral load changes 12 weeks following ARV treatment reinitiation (P=0.90 and P=0.29, respectively). CONCLUSIONS: We found no additional predictive value of replication capacity for virological or immunological responses (above what PSS provides) in patients undergoing salvage ARV treatment.