Reanalysis of Coreceptor Tropism in HIV-1–Infected Adults Using a Phenotypic Assay with Enhanced Sensitivity

Monogram Biosciences) was used to retest coreceptor tropism samples from 4 different cohorts of HIV-1– infected patients. Nine percent to 26 % of patients with CCR5-tropic virus by the original Trofile assay had CXCR4-using virus by TF-ES. Lower CD4 cell counts were associated with CXCR4-using virus in all cohorts. In persons not receiving combination antiretroviral therapy, viral coreceptor tropism has been associated with HIV-1 disease progression [1]. More recently, as-sessment of coreceptor tropism is necessary prior to initiation of CCR5 antagonist therapy. The Trofile coreceptor tropism assay (Monogram Biosciences) phenotypically characterizes a viral envelope population as using CCR5 or CXCR4 exclusively (R5 or X4, respectively) or having dual-tropic or mixed infection