Nef enhances virion infectivity independently of whether HIV-1 entry occurs via membrane microdomains. Single round infection analysis on HeLa cells transiently expressing the indicated CD4 variants. Productively infected, p24CA positive cells were quantified 36 hours post infection by flow cytometry. Data represent average values from three independent experiments with the indicated standard error of the mean. Depicted is the relative virion infectivity with values for HIV-1NL4-3 NefSF2 (wt) arbitrarily set to 100%.