Extrinsic TLR9 signaling is required for a destructive CTL response. (A) A schematic of the study design. C57BL/6 or TLR9 −/− mice received i.v. injections of AAV8 expressing hOTCco-SIINFEKL. Fourteen days after vector delivery, OT-1 CD8+ T cells were transferred to recipient mice concurrent with an administration of 40 μg of CpG ODN, which was also administered for three days following adoptive transfer. We monitored serum (B) AST and (C) ALT levels every seven days following vector delivery. Following the termination of the study, we determined the levels of (D) genome copy and (E) transgene mRNA expression levels. N = 5. Statistical analysis by ANOVA with a Bonferroni posttest to vector only control. *P < 0.05, **P < 0.001, ***P < 0.0001. Error Bars = SEM.