Codelivery of IL-7 Augments Multigenic HCV DNA Vaccine-induced Antibody as well as Broad T Cell Responses in Cynomolgus Monkeys

Background A crucial limitation of DNA vaccines is its weak immunogenicity, especially in terms of eliciting antibody responses in non-human primates or humans; therefore, it is essential to enhance immune responses to vaccination for the development of successful DNA vaccines for humans. Methods Here, we approached this issue by evaluating interleukin-7 (IL-7) as a genetic adjuvant in cynomolgus monkeys immunized with multigenic HCV DNA vaccine. Results Codelivery of human IL-7 (hIL-7)-encoding DNA appeared to increase DNA vaccine-induced antibody responses specific for HCV E2 protein, which plays a critical role in protecting from HCV infection. HCV-specific T cell responses were also significantly enhanced by codelivery of hIL-7 DNA. Interestingly, the augmentation of T cell responses by codelivery of hIL-7 DNA was shown to be due to the enhancement of both the breadth and magnitude of immune responses against dominant and subdominant epitopes. Conclusion Taken together, these findings suggest that the hIL-7-expressing plasmid serves as a promising vaccine adjuvant capable of eliciting enhanced vaccine-induced antibody and broad T cell responses.