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Abstract

Cervical cancer is the fourth most common cancer in women worldwide. It is estimated that more than one million women are currently suffering from cervical cancer, and there are 570,000 new cases in 2018. The majority of cases (>80%) occur in less developed region. There are three HPV prophylactic vaccines in the market currently. They are designed to induce L1-specific antibodies blocking the infection of epithelial cells. The therapeutic efficacy was neither observed for Cervarix nor for Gardasil. Therefore, preventive vaccines cannot benefit individuals with already existing viral infections. As a result, a high prevalence of cervical cancer still threatens human life worldwide. Until now, there are no anti-HPV drugs available, an effective strategy should be the therapeutic vaccination to eliminate HPV-transformed cells by the activated immune system. The objective of my PhD project is to combine prophylactic and therapeutic value in one vaccine. The combined vaccine would ideally resolve productive infections and HPV-related diseases benefitting both uninfected and already infected individuals. Thioredoxin (Trx) was applied as a scaffold to develop HPV prophylactic vaccine Trx-L2 and Trx-8mer-OVX313 in our lab previously. In my project, we firstly verified that Trx was also able to induce CD8+ cytotoxic T cell responses. Then, we designed our prophylactic and therapeutic combined vaccines based on Trx-L2 and Trx-8mer-OVX313. HPV16 E749-57 was chosen as CTL epitope since it is considered a tumor specific antigen as well as an oncoprotein being expressed throughout the whole HPV life cycle. We developed the combined vaccines PADRE-Trx-L2-flank E7 (monomeric) and Trx-8mer-flank E7-OVX313 (heptameric). The E7-specific T cell responses were compared via IFN-gamma ELISpot between these two vaccines and the data indicates that heptamerization leads to a stronger T cell response. We therefore continued investigating the B cell responses induced by the heptameric antigen. From pseudovirion-based neutralization assay (PBNA), we saw that presence of CD8 T cell epitopes on the antigen does not interfere with the induction of neutralizing antibodies. In view of the in vitro promising results of Trx-8mer-flank E7-OVX313, we were encouraged to evaluate the therapeutic potential of Trx-8mer-flank E7-OVX313 in vivo. C57BL/6N mice were administrated with two doses vaccination after TC-1 cells challenge, and a potent antitumor activity was observed. These results demonstrate that antigen Trx-8mer-flank E7OVX313 is a promising and cost-efficient candidate with both prophylactic and therapeutic effectiveness.