Prevention and treatment of cervical cancer by a single administration of human papillomavirus peptide vaccine with CpG oligodeoxynucleotides as an adjuvant in vivo

No licensed therapeutic human papillomavirus (HPV) vaccine is currently available, so it remains a high priority to develop a therapeutic HPV vaccine or prophylactic/therapeutic HPV vaccine for cervical cancer. In this current study, we designed an HPV vaccine including CpG oligodeoxynucleotides 1826 as an adjuvant and HPV16 E7 43-77 peptide as antigen, which contains a CD8 T cell epitope (E7 49-57), and two CD4 T cell epitopes (E7 43-77 and E7 50-62). The prophylactic and therapeutic effect on cervical cancer induced by a single administration of vaccine, were comprehensively evaluated by examining the tumor size and the percentage of tumor-free/bearing mice. The cellular immunity and modulation of immunosuppressive cells induced by the vaccine were evaluated by examining intracellular cytokine staining (ICS) of splenocytes and FCM, respectively. Antigen-specific cytotoxic T-lymphocyte (CTL) responses were investigated using in vivo cytolytic assay. The results showed that the single administration of vaccine elicited significant prophylactic as well as therapeutic effect on cervical cancer. The increased cellular immunity mediated by CD4 + IFN-gamma + T cells and CD8 + IFN-gamma + T cells, and the decreased numbers of immunosuppressive cells including regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs) were induced by the vaccine. Antigen-specific CTL response was also induced by vaccination. These findings suggested that significant anti-tumor effect of the vaccine may result from the induction of increased cellular immunity and decreased immunosuppressive cells.