FIG. 1.

Nef enhances HIV-1 infectivity independently of the viral coreceptor tropism. P4-CCR5 cells were infected with NL4-3 variants containing an intact nef gene or a deletion in the nef unique region. Infections were performed in triplicate with three different virus stocks containing 20 ng of p24 antigen. Shown are average values of nine measurements ± standard deviations. Comparable results were obtained with the variants containing a premature stop codon in the nef gene. CPS, counts per second; WT, wild type.