FIG. 6.

Virion transcomplementation is minimally dependent on Nef when donor virions are pseudotyped by VSV-G. Core-defective virions containing or lacking Nef were produced by contransfection with or without a VSV-G expression vector, resulting in particles bearing VSV and/or HIV-1 Env proteins. These particles were incubated with receptor-pseudotyped target virions prior to addition to CD4-negative target cells, allowing infection only through the VSV-G receptor. The mean infectivity values of triplicate determinations are shown as the number of infectious units per nanogram of p24, with error bars representing one standard deviation. In contrast to the results with nonpseudotyped donor virions (Fig. 5), only a relatively small enhancement by Nef was observed in this system.