Introduction Identification of human papillomavirus (HPV) as the etiologic factor of cervical, anogenital, and a subset of head and neck cancers has stimulated the development of preventive and therapeutic HPV vaccines to control HPV-associated malignancies. Excitement has been generated by the commercialization of two preventive L1-based vaccines, which use HPV virus-like particles (VLPs) to generate capsid-specific neutralizing antibodies. However, factors such as high cost and requirement for cold chain have prevented widespread implementation where they are needed most. Areas covered Next generation preventive HPV vaccine candidates have focused on cost-effective stable alternatives and generating broader protection via targeting multivalent L1 VLPs, L2 capsid protein, and chimeric L1/L2 VLPs. Therapeutic HPV vaccine candidates have focused on enhancing T cell-mediated killing of HPV-transformed tumor cells, which constitutively express HPV-encoded proteins, E6 and E7. Several therapeutic HPV vaccines are in clinical trials. Expert opinion Although progress is being made, cost remains an issue inhibiting the use of preventive HPV vaccines in countries that carry the majority of the cervical cancer burden. In addition, progression of therapeutic HPV vaccines through clinical trials may require combination strategies employing different therapeutic modalities. As research in the development of HPV vaccines continues, we may generate effective strategies to control HPV-associated malignancies.

Purpose Radiation therapy (RT) kills cancer cells by causing DNA damage, and stimulates a systemic antitumor immune response by releasing tumor antigen and endogenous adjuvant within the tumor microenvironment. However, RT also induces the recruitment of immunosuppressive myeloid cells, which can interfere with the antitumor immune responses elicited by apoptotic tumor cells. We hypothesized that local delivery of vaccine following RT will lead to the priming of antigen-specific cytotoxic T lymphocyte (CTL) immune responses and render immunosuppressive myeloid cells susceptible to killing by the activated CTLs. Experimental Design Using several antigenic systems, we tested whether intratumoral injection of antigenic peptide/protein in irradiated tumors would be able to prime CTLs as well as load myeloid cells with antigen, rendering them susceptible to antigen-specific CTL killing. Results We show that by combining RT and targeted antigenic peptide delivery to the tumor, the adjuvant effect generated by RT itself was sufficient to elicit the priming and expansion of antigen-specific CTLs, through the type I interferon dependent pathway, leading to synergistic therapeutic antitumor effects compared to either treatment alone. In addition, using two different types of transgenic mice, we demonstrated that CTL-mediated killing of stromal cells in tumors by our approach is important for tumor control. Finally, we confirmed the efficacy of this approach in our preclinical model using two clinically tested therapeutic HPV vaccines. Conclusions These data serve as an important foundation for the future clinical translation of RT combined with a clinically tested therapeutic HPV vaccine for the control of HPV-associated cancers.

Purpose Imiquimod is a toll-like receptor 7 agonist utilized topically to manage genital warts and basal cell carcinoma. We examine the combination of topical imiquimod with intramuscular administration of CRT/E7, a therapeutic HPV vaccination that comprises a naked DNA vector expressing calreticulin fused to HPV16 E7. Experimental Design Using an orthotopic HPV16 E6/E7+ syngeneic tumor, TC-1, as a model of high-grade cervical/vaginal/vulvar intraepithelial neoplasia, we show that combining CRT/E7 vaccination with cervicovaginal deposition of imiquimod results in synergistic immune-mediated tumor clearance. Results Imiquimod induces cervicovaginal accumulation of activated E7-specific CD8+ T cells elicited by CRT/E7 vaccination. Recruitment was not dependent upon the specificity of the activated CD8+ T cells, but was significantly reduced in mice lacking the IFNγ receptor. Intravaginal imiquimod deposition induced upregulation of CXCL9 and CXCL10 mRNA expression in the genital tract. These chemokines are expressed upon IFNγ receptor activation and attract cells expressing their receptor, CXCR3. In this study, T cells attracted by imiquimod to the cervicovaginal tract expressed CXCR3 as well as the tissue resident memory T cell (Trm) marker CD49a, a mucosal homing integrin. Our results indicate that intramuscular CRT/E7 vaccination in conjunction with intravaginal imiquimod deposition recruits antigen-specific CXCR3+CD8+ T cells to the genital tract. Conclusions Our study has potential clinical relevance because imiquimod is FDA approved for condyloma accuminata and basal cell carcinoma and intramuscular vaccination with pNGVL4a-CRT/E7(detox) is currently undergoing clinical testing, suggesting potential for their synergistic action to induce strong antigen-specific Trm-mediated immune responses and antitumor effects in genital mucosa.