Preparation and in vivo anti-tumor evaluation of human papillomavirus E7 adjuvanted with Montanide ISA 266 as a vaccine candidate

Introduction: Human papillomavirus (HPV) 16 E7 protein is expressed constitutively by HPV-infected tumor cells. Mutant versions of E7 are considered as safer candidates for immunotherapy of cervical cancer.  Different strategies including formulation with adjuvants are used to induce a potent immune response against antigenic proteins. Methods: In this experimental study, we used Escherichia coli as a host to recombinantly express wild-type E7 and its mutant non-oncogenic form as E7GGG. We formulated both antigens with Montanide ISA 266 adjuvant and evaluated IFN-γ and IL-4 cytokines and antibody levels and also tumor regression in tumor-harboring C57BL/6 mice. Results: It was demonstrated that formulation of E7 and E7GGG antigens with Montanide ISA 266 resulted in a Th2-biased immune response. In the therapeutic mouse model, these formulations resulted in significant tumor regression compared to the control group. Conclusion: The formulation of the wild-type E7 and mutant E7GGG with Montanide ISA 266 might not be an optimal approach to regress TC-1 induced tumor; however, such combinations might be considered as an additive approach for stimulating the immune responses.