Ce of sCD4 (40 mg/ml, 0.8 mM) and then adsorbed by diffusion or magnetically to cultures of the indicated cell type. Measured luciferase activity is presented as mean relative light units (RLU)6standard error of the mean (s.e.m.) of three replicate samples. doi:10.1371/journal.ppat.1000360.gPLoS Pathogens | www.plospathogens.orgMetastable Activation of HIV-1 Envto enhance HIV-1 infection of CD42CC