FIG. 9.

Expression of wild-type EBNA3A enables the continuous proliferation of LCLs infected with EBV expressing recombinant EBNA3AHT in medium without 4HT. (A) EBNA3AHT-infected LCL 41-3 cells were transfected with 30 μg of the oriP plasmid expressing FLAG-EBNA3A (oriP-fE3A) or a control oriP plasmid expressing EGFP (oriP-cont) and cultured in conditioned medium with 4HT for 7 days. Then, cells were washed and resuspended at 2 × 10⁶ cells/10 ml of complete medium with (+4HT) or without (−4HT) 4HT in 25-cm² culture flasks (day 0). Every 7 days, cells were counted and all cultures were split. The total cell numbers derived from the initial cultures were calculated and plotted at each time point. Protein lysates were prepared from these cells, and Western blot analyses (B) were performed using EBV-immune human serum. The data are representative of five similar experiments.