Rodney Macedo

Human papillomavirus (HPV) is involved in the development of anogenital tumors and also in the development of oropharyngeal head and neck carcinomas, where HPV-16, expressing the E6 and E7 oncoproteins, is the most frequent serotype. Although vaccines encoding L1 and L2 capsid HPV proteins are efficient for the prevention of HPV infection, they are inadequate for treating established tumors. Hence, development of innovative vaccine therapies targeting E6/E7 is important for controlling HPV-induced cancers. We have engineered a nononcogenic mutated E7-specific plasmo-retroVLP vaccine (pVLP-E7), consisting of plasmid DNA, that is able to form recombinant retrovirus-based virus-like particles (VLPs) that display E7 antigen into murine leukemia virus Gag proteins pseudotyped with vesicular stomatitis virus envelope glycoprotein (VSV-G). pVLP-E7 vaccinations were studied for their ability to generate specific immune responses and for induction of protective immunity against tumor cell challenge in preventive and therapeutic models. The produced VLPs induce the maturation of human dendritic cells in vitro and mount specific E7 T cell responses. Intradermic vaccinations of mice with pVLP-E7 show their efficacy to generate antigen-specific T cell responses, to prevent and protect animals from early TC-1 tumor development compared with standard DNA or VLP immunizations. The vaccine efficacy was also evaluated for advanced tumors in mice vaccinated at various time after the injection of TC-1 cells. Data show that pVLP-E7 vaccination can cure mice with already established tumors only when combined with Toll-like receptor-7 (TLR7) and TLR9 agonists. Our findings provide evidence that pVLPs, combining the advantages of DNA and VLP vaccines, appear to be a promising strategy for the treatment of HPV-induced cancers.

ABSTRACT Purpose Papillomavirus (HPV)-16 infection has been recently associated with oropharyngeal head and neck cancers (HNCs) that express the E6 and E7 oncoproteins. The licensed vaccines are efficient for the prevention of HPV infection, but not for established tumors. Therefore innovative therapeutic vaccines targeting HPV oncogenes are required. Previously, we have developed a DNA-based vaccine strategy using plasmo-VLP carrying a non-oncogenic mutated, but immunogenic, form of E7 from HPV16 (pVLP-E7). pVLPs allow to form in vivo VLPs (viral-like particles formed by structural proteins devoid of viral genome). Thus, we showed that pVLP-E7 can elicit specific anti-E7 immune responses and cure mice from E6/E7 HPV16-positive tumors injected subscutaneously in the flank of animals. The present study aims at developing an orthotopic model of HNCs in mice as a pre-clinical model. Material and methods TC-1 tumor cells, an epithelial murine cell line that express E6 and E7 of HPV 16, were injected into the tongue or cheek (orthotopic models) or in the flank (ectopic model) of C57BL/6 mice; different routes of vaccination (intranasal, intra-cheek or intradermal) with pVLP-E7 were tested in order to induce local and systemic immune responses; tumor growth, anti-E7 immune responses, and anti-tumor effects against established tumors were compared between the different tumor models and routes of vaccination. Results The cheek model was better suited for future test of immunization than intralingual or subcutaneous tumor models, due to better survival rates and slower growth kinetics. Intradermal vaccination with pVLP-E7 was the better route of administration to achieve a systemic anti-E7 T-cell response. Interestingly, intradermal and intra-cheek vaccinations appeared to be both equally efficient to stimulate local immune responses as well as anti-tumoral responses by using the orthotopic model. Conclusions DNA vaccinations with pVLP-E7 can induce therapeutic anti-tumoral effects using an intra-cheek orthotopic model of HPV-induced HNCs.