Codependence of Nef-mediated HIV-1 receptor downregulation functions. Pairwise associations of relative downregulation activities of CD4 and CCR5, CCR5 and CXCR4, and CD4 and CXCR4 by Nef clones from EC (A), CP (B), and AP (C) cohorts are shown. Statistical analyses were performed using Spearman's correlation test. EC Nef clones EC12, EC19, and EC51 are indicated by arrows in panel A. Downregulation functions of patient-derived Nef sequences were normalized to NefSF2, and each data point reflects the mean of triplicate determinations.