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. 2004 Jan;78(2):1026–1031. doi: 10.1128/JVI.78.2.1026-1031.2004

FIG. 1.

FIG. 1.

PR− virions display a fusion defect in a cell-cell fusion-from-without assay. env-defective HIV-1 NL4-3 (NL4-3/KFS) (19, 22) and its PR− counterpart were cotransfected into 293T cells with pUC19, with vectors expressing the WT NL4-3 Env (pIIINL4env) (39) or the CT truncation mutant CTdel-144 (pNL4envCTdel-144) (39). Virus-containing supernatants were harvested 2 days posttransfection, and virions were concentrated (10 to 20×) by centrifugation (20,000 × g for 2 h). The concentrated pseudovirions were added to Jurkat cells. After a 20-h cultivation, the number of syncytia (whose diameters were more than four times those of unfused Jurkat cells) was scored. The number of syncytia was expressed as a ratio (%) of those obtained with PR− versus PR+ virions. The average number of syncytia induced by PR+ virions bearing WT and CTdel-144 Env was 171 and 116, respectively. Data are means of the results of four independent experiments. Error bars indicate standard deviations.