A DNA vaccine encoding mutated HPV58 mE6E7-Fc-GPI fusion antigen and GM-CS F and B7.1

Abstract

Background: Persistent infection with high-risk human papillomavirus (HPV) is a predominant cause of cervical cancer, and HPV58 is the third most common virus detected in the patients with cervical cancer in Asia. E6 and E7 are the viral oncogenes which are constitutively expressed in HPV-associated tumor cells and can be used as target antigens for related immunotherapy. In this study, we modified the HPV58 E6 and E7 oncogenes to eliminate their oncogenic potential and constructed a recombinant DNA vaccine that coexpresses the sig-HPV58 mE6E7-Fc-GPI fusion antigen in addition to granulocyte-macrophage colony-stimulating factor (GM-CSF) and B7.1 as molecular adjuvants (PVAX1-HPV58 mE6E7FcGB) for the treatment of HPV58 (+) cancer. Methods: PVAX1-HPV58 mE6E7FcGB recombinant DNA vaccine was constructed to express a fusion protein containing a signal peptide, a modified HPV58 mE6E7 gene, and human IgG Fc and glycosylphosphatidylinositol (GPI)-anchoring sequences using the modified DNA vaccine vector PVAX1-IRES-GM/B7.1 that coexpresses GM-CSF, and B7.1. C57BL/6 mice were challenged by HPV58 E6E7-expressing B16-HPV58 E6E7 cells, followed by immunization by PVAX1-HPV58 mE6E7FcGB vaccine on days 7, 14, 21 after tumor challenge. The cellular immune responses in immunized mice were assessed by measuring IFN-γ production in splenocytes upon stimulation by HPV58 E6E7-GST protein and the lysis of B16-HPV58 E6E7 target cells by splenocytes after restimulation with HPV58 E6E7-GST protein. The antitumor efficacy was evaluated by monitoring the growth of the tumor. Results: PVAX1-HPV58 mE6E7FcGB elicited varying levels of IFN-lsgdB58onn T-cell immune responses and lysis of target cell in mice in response to the recombinant antigen HPV58 E6E7-GST. Furthermore, the vaccine also induced antitumor responses in the HPV58 (+) B16-HPV58 E6E7 tumor challenge model as evidenced by delayed tumor development. Conclusion: The recombinant DNA vaccine PVAX1-HPV58 mE6E7FcGB efficiently generates cellular immunity and antitumor efficacy in immunized mice. These data provide a basis for the further study of this recombinant vaccine as a potential candidate vaccine.