Human papillomavirus (HPV) is a significant cause of cervical cancer-related deaths worldwide. Because HPV is a sexually transmitted mucosal pathogen, enhancement of antigen-specific mucosal immune response likely serves good strategy for vaccination. However, mucosal vaccines generally do not induce strong enough immune responses. Previously we proved that a bacterial flagellin, Vibrio vulnificus FlaB, induce strong antigen-specific immune responses by stimulating the Toll-like receptor 5. In this study, we tested whether FlaB could serve as an effective mucosal adjuvant for a peptide-based HPV preventive cancer vaccine.

Mice were intranasally administered with a mixture of FlaB and E6/E7 protective peptides in 5-day interval for a total of two times. Five-days after the last vaccination, cellular immune responses of the vaccinated mice were analyzed. Tumor growth was also observed after a subcutaneous implantation of TC-1 cells bearing E6/E7 antigens.

Intranasal administration of the E6/E7 peptide mixture with FlaB elicited a strong antigen-specific cytotoxic T lymphocyte activity and antigen-specific interferon-γ production from splenocytes and cervical lymph node cells. Furthermore, FlaB, as a mucosal adjuvant, conferred an excellent protection against TC-1 tumor challenge with high survival rates in E6/E7 immunized animals.

These results indicate that FlaB can be a promising mucosal adjuvant for nasal HPV vaccine development.