Design Of A Novel Self-assembled Nanoparticle Vaccine With HIV-1Tat_49-57/HPV16E7_49-57fusion Peptide And GM-CSF DNA And Investigatione Of Its Anti-tumor Immunological Effect In Mice*

Background: Recently, the incidence of sexually transmitted diseases (STDs) is foundto be increasing with years, especially in developing countries. Condyloma acuminatuminfected by human papillomavirus (HPV) has shown a rising trend. More importantly, it isnow clear that HPV is the etiological agent implicated in cervical cancer and its precursorlesions (cervical intraepithelial neoplasia (CIN)), with HPV DNA being detected in99.7%ofcervical cancers. HPV-16is the most common type associated with cervical cancer, and hasbeen identified in approximately50%of all tumors. HPV-16E7, one of its oncoproteins, isessential for the induction and maintenance of cellular transformation. Thus, HPV-16E7is anideal target for developing vaccine and immunotherapeutic strategies aimed at controllingHPV infections and HPV-associated lesions. Peptide-based vaccines derived from HPV16E7,aiming at the induction of effective T cell responses against established cervical cancer, haveso far only met with limited clinical success. It is necessary to develop novel peptide-basedstrategies to substantially improve the immune response against HPV16-related cancer.Objective: We aimed to design a novel peptide-based self-assembled nanoparticleHPV16vaccine through combining the cell-penetrating peptide HIV-1Tat_49-57that was fusedwith HPV16E7_49-57CTL epitope and GM-CSF gene, and investigate how it improves theimmune response and the therapeutic outcome ex vivo and in vivo.Methods: Nanoparticles were prepared and identified by TEM, Gel retardation andDNase I protection assays. The vaccine-induced immune responses were analyzed usingCCK-8proliferation, flow cytometry, ELISPOT, ex vivo specific cytolysis of CTL-lactatedehydrogenase release and in vivo cytotoxicity assays, respectively. The in vivo tumor protective effectiveness of nanoparticle Tat-E7/pGM-CSF was investigated in theprophylactic and therapeutic mice models.Results: This type of vaccine formulation formed the20-80nm nanoparticles, andgreatly improved epitope-specific immunity both ex vivo and in vivo. Importantly, thisvaccine type was associated with decreased tumor growth and enhanced long-term survival inanimals. The underlying mechanisms were determined to include priming of enhancedfrequency of E7-specific CD8+memory T subtype cells.Conclusions: These results suggest the nanoparticle Tat-E7/pGM-CSF represents apromising novel approach to enhance the potency of peptide-based cervical cancer vaccines,and this vaccine design strategy may act as a useful reference for the research ofvirus-associated diseases and specific tumor immunotherapies.