E138A in HIV-1 reverse transcriptase is more common in subtype C than B: implications for rilpivirine use in resource-limited settings.

The nonnucleoside reverse transcriptase (RT) inhibitor rilpivirine (RPV) has been co-formulated with emtricitabine and tenofovir disoproxil fumarate for initial therapy of HIV-1-infected individuals. RPV, formulated as a long-acting nanosuspension, will also be assessed for its ability to prevent HIV-1 infection in resource limited settings. In this study, we determined whether any pre-existing genetic differences occurred among different HIV-1 subtypes at residues in RT associated with decreased virologic response to RPV. We found that the E138A substitution occurs more frequently in subtype C (range: 5.9-7.5%) than B (range: 0-2.3%) sequences from both treatment-naïve and -experienced individuals (p<0.01) in 4 independent genotype databases. In one of the databases (Stanford University), E138K and E138Q were also more common in RTI-experienced subtype C sequences (1.0% and 1.1%, respectively) than in subtype B sequences (0.3% and 0.6%, respectively). E138A/K/Q in subtype C decreased RPV susceptibility 2.9-, 5.8-, and 5.4-fold, respectively. Taken together, these data suggest that E138A could impact treatment or prevention strategies that include RPV in geographic areas where subtype C infection is prevalent.