FIG. 5.

Efficiency of cell-to-cell viral transmission. (a) Chronically infected Jurkat cells (3,000 cells) expressing either the wild type or the Y712S mutant were seeded in the presence of 300,000 HeLa-CD4-LTR–β-gal cells for 1, 4, or 16 h. The number of blue cells was counted 48 h after the beginning of the contact; the results are presented as the average of three independent experiments with error bars indicating standard deviation. (b) Viruses were recovered from the same chronically infected cell lines used in panel a. The same viral production, as measured by a reverse transcriptase assay, was observed in these cells, and the same volumes of virus inoculum were thus used to measure the infectivity of cell-free viruses on HeLa-CD4-LTR–β-gal cells. Results for the wild type (WT) and Y712S mutant are presented as the average of three independent experiments with error bars indicating standard deviation. Statistical significance was established by Student’s t test; significant differences from wild type at P < 0.02 (∗) or P < 0.005 (∗∗) are indicated.