The Strategies Of Improving The Efficacy Of Human Papillomavirus Fusion Protein Vaccine

Ph. D. Student:Xinxin Song Supervisor:Qingzheng Zhao Department of Cell and Molecular Biology, Cancer Institute (Hospital), Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing 100021, ChinaHuman papillomavirus (HPV) accounts for approximately 5.3% of cancers worldwide, including cervical cancer, and subsets of genital and head and neck cancer. It is estimated that 50 million women carry HPV and approximately 500,000 women develop cancer yearly. Thus, there is a continuing and significant need to develop better strategies to treat HPV-induced lesions. Over the last decade, the field of cancer vaccines is in an active state of clinical investigations, consistent clinical responses have not been very well obtained so far. The tumor microenvironment represents one consistently effective barrier to clinical responses, and the low expression or absence of human leukocyte antigen (HLA) Class I and several antigen-processing machinery (APM) molecules in tumor cells also result in immune escape from host immune surveillance. In this study we explored the strategies to the improve tumor microenvironment and enhance the efficacy of HPV vaccines, and promoted the expression of HLA class I molecule of E7-positive human tongue carcinoma xenografts by HPV therapeutic vaccine.Tumor microenvironment is comprised of proliferating tumor cells, the tumor stroma, blood vessels, infiltrating inflammatory cells and a variety of associated tissue cells. Recent studies have identified myeloid derived suppressive cell (MDSC) as one of the important elements in tumor-associated immunosuppression. In our previous study, we have developed a recombinant protein vaccine mE6Δ/mE7/TBhsp70Δ, and demonstrated that this fusion vaccine is able to elicit anti-tumor immunity against TC-1 tumor cells. However, the response seems not to be sufficient to retard large TC-1 tumor growth. In this study, we found significant accumulation of MDSC in large TC-1 tumors and demonstrated HPV therapeutic vaccine restored antitumor immune responses with the correction of aberrant myeloid cell differentiation by all-trans retinoic acid (ATRA). Our study demonstrated that combining ATRA with vaccination not only decreased the number of Gr-1+CDllb+MDSCs, but suppressed the function of Gr-1+CD11b+MDSCs with the decreased expression of CD80. Furthermore, large numbers of CD11c+CD80+, CD11c+CD86+ and CD11c+MHCII+ mature dendritic cells were recruited. The combination therapy generated significantly increased number of functional E7-specific T cell with elevated interferon-γ(IFN-y) secretion and enhanced cytotoxic T-cell activity.Another most successful strategy of tumor-induced immune evasion is the recruitment, expansion, and activation of CD4+CD25+FoxP3+ regulatory T cells (Tregs). They exist naturally at low numbers, but have been documented to increase in patients or animals with malignancies and are capable of suppressing both the innate and the adaptive immune responses in the microenvironment. Analyses of regulatory cells recruited during the growth of the E7-expressing tumor, TC-1 revealed a high percentage of Tregs as well as MDSCs in spleens and tumors. In the present study, we proposed that treatment with immune-modulating doses of cyclophosphamide (CTX) and ATRA would result in a beneficial tumor microenvironment with the suppression of Tregs and MDSCs, and thus enhance the effect of a HPV protein vaccine. Our results showed that CTX preconditioning and persistent ATRA treatment along with the vaccine achieved long-term survival and induced long-term memory responses. However, the effect of the antitumor response sharply declined when the tritherapy was initiated after the optimal therapeutic time. The more intensive regimen could rescue the effect of the tritherapy accompanied by the decreased percentage of Tregs and MDSCs in spleens and tumors. Besides a favorable host environment was created by the reduced secretion of interleukin (IL)-10, IL-6 and vascular endothelial growth factor (VEGF) in the tumor niche, and decreasing the expression of phosphorylation-signal transducer and activator of transcription (STAT)3 of TC-1 tumors.HPVs have been shown to play a role in the etiology of a subset of squamous cell carcinomas of the head and neck (SCCHN). Alterations in tumor antigen processing and presentation represent a major immune escape mechanism of SCCHN tumors. We confirmed that the expression of HLA Class I molecules and several antigen-processing machinery components were down-regulated in E7-associated SCCHN, and these molecules could be restored by IFN-y treatment. We previously developed a recombinant NCRT/E7/hsp protein and demonstrated that this fusion vaccine was able to generate significant antitumor responses against TC-1 tumors in the C57BL/6 mouse model. In this study, we found that human IFN-y, was induced by immunization of Hu-PBL-SCID mice with the recombinant fusion protein vaccine. We also demonstrated that vaccination with NCRT/E7/hsp was able to effectively stimulate the generation of a cytotoxic T lymphocyte response to E7-positive SCCHN in vitro and caused significant inhibition of tumor growth in vivo by promoting the expression of HLA Class I and antiangiogenic effects.In summary, tumorigenesis, characterized by multifactor, multiphase and multigene involvement, is a very complex pathologic process and a systemic disease. These findings suggest a potential clinical benefit for the immunotherapy of HPV-associated malignancies.