Fusion of CTLA-4 with HPV16 E7 and E6 Enhanced the Potency of Therapeutic HPV DNA Vaccine

Lili Gan,Rong Jia,Jihua Guo,Lili Zhou,Mingwen Fan

doi:10.1371/journal.pone.0108892

Abstract

Preventive anti-HPV vaccines are effective against HPV infection but not against existing HPV-associated diseases, including cervical cancer and other malignant diseases. Therefore, the development of therapeutic vaccines is urgently needed. To improve anti-tumor effects of therapeutic vaccine, we fused cytotoxic T-lymphocyte antigen 4 (CTLA-4) with HPV16 E7 and E6 as a fusion therapeutic DNA vaccine (pCTLA4-E7E6). pCTLA4-E7E6 induced significantly higher anti-E7E6 specific antibodies and relatively stronger specific CTL responses than the nonfusion DNA vaccine pE7E6 in C57BL/6 mice bearing with TC-1 tumors. pCTLA4-E7E6 showed relatively stronger anti-tumor effects than pE7E6 in therapeutic immunization. These results suggest that fusing CTLA-4 with E7E6 is a useful strategy to develop therapeutic HPV DNA vaccines. In addition, fusing the C-terminal of E7 with the N-terminal of E6 impaired the functions of both E7 and E6.

Highlights

Persistent infection of high-risk human papillomavirus (HRHPV) causes cervical cancer
Expression of E7E6 protein in 293 cells Wild-type E6, recombinant CTLA4-E7E6, or E7E6 fusion protein was detected in the 293 cells transfected by pCTLA4E7E6 or pE7E6 with mouse anti-HPV16 E7 antibody (Figure 2)
This result indicates that the oncogenicity of E7 and E6 in recombinant fusion proteins was disrupted in 293 cells

Summary

Introduction

Persistent infection of high-risk human papillomavirus (HRHPV) causes cervical cancer. HPV16 is the most prevalent genotype of HPV It is found in approximately 50% of all cervical cancers. GARDASIL (quadrivalent, Merck, 2006) and CEVARIX (bivalent, GlaxoSmithKline, 2009) are FDA-approved prophylactic vaccines that contain L1 capsid HPV proteins and that prevent infections with corresponding HPV types [3,4,5]. These vaccines can induce high concentrations of neutralizing antibodies, efficiently block the cell entry of high-risk HPVs, and prevent infections. They elicit no effect on existing infections and HPV-associated diseases, including cervical cancer. The development of therapeutic vaccines is urgently needed to control HPV-associated diseases [6]

Methods

Results

Conclusion