FIG. 5.

Termination of transgene expression 60 days following immunization does not affect the maintenance of the memory response. (A) C57BL/6 mice received 10⁹ PFU Ad-tTA-SIINFEKL-Luc intramuscularly. Thigh muscles were harvested at 1, 3, 14, 28, and 58 days and were assayed for luciferase activity. The results are means ± standard errors of the means for 10 muscle samples per time point. (B and C) Mice (five per group) were immunized with 10⁹ PFU of Ad-tTA-SIINFEKL-Luc on day zero. On day 60, half of the mice were put on DOX. (B) The frequency of SIINFEKL-specific cells was assessed on the day DOX treatment began (day 60) and 2 months later (day 120). (C) The number of antigen-specific CD8⁺ T cells in the spleen was assessed 2 months after the onset of DOX treatment. Open bars, results for mice that received DOX on day 60 (DOX d+60); shaded bars, results for mice that did not receive DOX. Each bar reflects the mean ± standard error of the mean. NS, not significant.