Improved Virological Outcome in Non-B Patients: A Possible Role for Baseline Coreceptor Tropism

TO THE EDITOR—We greatly appreciated the article of Scherrer et al [1] evaluating viral response to combination antiretroviral therapy (cART) in patients with subtype B (34.3% previously exposed to suboptimal therapies, P < .001) and nonsubtype B human immunodeficiency virus type 1 (HIV-1). The study brings to mind a similar article by Geretti et al [2], but we found particularly reasonable the choice of Scherrer et al to restrict the analysis to a single ethnic group (whites), thus avoiding potential biases caused by ethnicity. The authors demonstrated that virological failure was higher in patients with subtype B; in particular, subtype A and CRF02_AG infections were associated with lower virological failure rates. Because certain non-B subtypes do not seem more susceptible to some drugs, why should these patients have a better response to cART? A lower propensity to select for nucleoside reverse-transcriptase inhibitor– and protease inhibitor–related mutations has been suggested for some non-B subtypes by Soares et al [3]. It is our hypothesis that pretherapy differences might explain the improved