Effect on humoral and cellular immunity and on apoptosis in CIN2, CIN3, and HPV16+ cervical cancer of therapeutic divalent genetic vaccination with CMV replicon system (CRS) delivering HPV16 recombinantly mutated E6 and E7 viral oncogenes targeting p53 and Rb, respectively

Abstract

3062 Background: Prophylactic vaccines have no therapeutic capacity for all the women who are already infected with HPV16 and have developed cervical intraepithelial neoplasia (CIN) or cervical cancer. Approximately 300 million women with CIN and cervical cancer will require therapy in the next decades. Thus, there is a great demand for a therapeutic HPV vaccine. Methods: We developed a cytomegalovirus (CMV) replicon system (CRS) for delivery of the HPV16 recombinantly mutated E6 and E7 genes replacing part of the CMV genome for the HPV genes, which were genetically altered to block binding sites for p53 and Rb.The replicon-vectors infected and co-transfected CIN and cervical cancer cells in animal models derived from HPV16(+) CIN, and cervical Ca cells obtained from patients. The genetic vaccine was administered subcutaneously (SC) with a needless injection system. Results: After vaccination,the viral E6 oncogene did not degrade apoptotic p53, and it blocked activation of telomerase. This induced apoptosis and DNA repair in CIN and cervical cancer cells. Furthermore, the E7 viral oncogene did not degrade the retinoblastoma oncogene (Rb) protein releasing transcription factor E2F. This vaccination led to scheduled cell cycle entry, genetic stability, and mortalization of tumor cells. Humoral and cellular immune responses were exhibited, which led to irreversible D2 apoptotic stage of PCD type I leading to a bystander killing effect of CIN, and cervical cancer cells. BrdU and MTT analysis exhibited inhibition of DNA synthesis and metabolic activity of vaccinated tumor cells compared to controls. Conclusions: This genetic divalent vaccine coding for E6 and E7 mutations designed to prevent p53 and Rb binding sites activated humoral and cellular immune responses leading to apoptosis of CIN and cervical cancer cells. It is up to translational medicine to bring this therapeutic vaccine into the clinic for patients with CIN2, CIN3, and cervical cancer patients. No significant financial relationships to disclose.