Arayapong N, Pasomsub E, Kanlayanadonkit R, et al. - Given the utility of maraviroc, a C-C chemokine receptor 5 (CCR5) antagonist, as an alternative antiretroviral drug in treatment-experienced adults and children infected by CCR5-tropic human immunodeficiency virus type 1 (HIV-1) isolates, researchers here sought to determine the rates of HIV-1 coreceptor tropism and factors associated with coreceptor tropism. They performed enrollment of 52 HIV-1–infected individuals (median age: 14.9 years) with HIV-1 viral loads > 1,000 RNA copies/mL who were treatment-experienced or treatment-naive. The median CD4 cell count of 396.0 cells/µL and the median HIV-1 viral load of 43,339 RNA copies/mL were reported. In this population, the most prevalent HIV-1 subtype was CRF01_AE (36 patients, 69.2%). They identified association of X4-tropic viruses with the CRF01_AE subtype. Hence, they recommend performing testing of HIV tropism before treatment with CCR5 inhibitors in children in areas where CRF01_AE predominates.