The efficacy of a DNA vaccine containing inserted and replicated regions of the E7 gene for treatment of HPV-16 induced tumors

Abstract

A majority of cervical cancers are associated with HPV-16. A DNA vaccine (E7IR) was designed for prophylactic and therapeutic treatment of HPV-16+ tumors containing two repeats of the E7 gene to inactivate transformation and duplicate available epitopes. Mice were vaccinated then tumor challenged, or challenged and then immunized and monitored for tumor volume and survival. Splenocytes were utilized for in vivo CTL assays. The E7IR vaccine demonstrated decreased tumor volume and enhanced survival in prophylactic and therapeutic experiments and improved CTL mediated lysis. The E7IR vaccine shows promise in prevention of tumor formation and elimination of established tumors. KeywordsHuman Papillomavirus (HPV); DNA Vaccine; Cervical Cancer 1.IntroductionCancer of the uterine cervix is the second most common cause of cancer-related deaths in women worldwide. Approximately 510,000 new cases and 288,000 deaths are reported annually [1]. The development of cervical cancer is associated with infection with high risk types of Human Papillomaviruses (HPV). HPV is detected in 99.7% of cervical carcinomas [2], with high risks types HPV-16 and 18 accounting for nearly 70% of cervical cancer cases [3]. In contrast to many other cancers, the fact that cervical cancer is highly associated with a viral infection creates a unique opportunity for therapeutic vaccination against HPV to either prevent cervical cancer once an individual is infected or after the virus has caused cervical cancer. Integration of the viral genome into the host cell genome, a necessary step in cellular transformation, leads to the loss of some genes necessary for a productive viral life cycle and to deregulated or overexpression of the E6 and E7 oncoproteins. Because E7 has been shown to be consistently expressed in HPV-16 positive tumors, it is a logical target in HPV-16 vaccination strategies. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Preclinical studies using DNA based vaccine approaches tend to focus on enhancing presentation of HPV antigens via the MHC class I or MHC class II pathways [5]. Several different approaches have been examined including the attachment of ubiquitin to DNA constructs [6,7], targeting of tumor antigens to centrosomal compartments to enhance MHC class I presentation [8], the attachment to constructs of calreticulin to target HPV antigens to the MHC I pathway [9], optimization of codon usage for enhanced expression and presentation of HPV oncogenes [6,10,11] , utilization of modified genes to decrease the transformation capacity [12][13][14] or enhancement of intercellular s...

Chimeric Infectious Bursal Disease Virus-Like Particles as Potent Vaccines for Eradication of Established HPV-16 E7–Dependent Tumors

“…The treatment of well-established tumors is a considerable challenge, and several groups have reported therapeutic activity with CIN-cervical cancer candidate vaccines [33], [34], [35], [36]. Only a few authors have reported regressions of tumors above 0.5 cm 3 [20], [37], in addition to efficacy against two inoculations (re-challenge), as we observed in our study.…”

Therapeutic HPV DNA vaccines

“…Furthermore, mutation at E6 positions 63 or 106 has been shown to destroy several HPV-16 E6 functions, preventing the mutated E6 protein from immortalizing human epithelial cells [113,114]. Additional strategies to alleviate concerns for oncogenicity include employment of a shuffled E7 molecule, in which sequences encoding regions of the E7 protein were rearranged and certain sequences were duplicated to maintain all possible T-cell epitopes [100,115,116]. …”

Recent advances in strategies for immunotherapy of human papillomavirus‐induced lesions

“…In this approach, the native HPV16 E7 protein was split into 3 arbitrary regions designated as a, b and c; and all 3 regions, a, b and c were replicated to enhance expression This approach resulted in enhanced immunity as evidenced by the ability to prevent tumor formation and therapeutically treat existing tumors in C57BL/6 mice. 78 …”