Immunotherapy of a human papillomavirus (HPV) type 16 E7-expressing tumour by administration of fusion protein comprisingMycobacterium bovisbacille Calmette–Guérin (BCG) hsp65 and HPV16 E7

Abstract

SUMMARYHuman papillomavirus type 16 (HPV16) infection has been linked to the development of cervical and anal dysplasia and cancer. One hallmark of persistent infection is the synthesis of the viral E7 protein in cervical epithelial cells. The expression of E7 in dysplastic and transformed cells and its recognition by the immune system as a foreign antigen make it an ideal target for immunotherapy. Utilizing the E7-expressing murine tumour cell line, TC-1, as a model of cervical carcinoma, an immunotherapy based on the administration of an adjuvant-free fusion protein comprising Mycobacterium bovis BCG heat shock protein (hsp)65 linked to HPV16 E7 (hspE7) has been developed. The data show that prophylactic immunization with hspE7 protects mice against challenge with TC-1 cells and that these tumour-free animals are also protected against re-challenge with TC-1 cells. In addition, therapeutic immunization with hspE7 induces regression of palpable tumours, confers protection against tumour re-challenge and is associated with long-term survival (. 253 days). In vitro analyses indicated that immunization with hspE7 leads to the induction of a Th1-like cell-mediated immune response based on the pattern of secreted cytokines and the presence of cytolytic activity following antigenic recall. In vivo studies using mice with targeted mutations in CD8 or MHC class II or depleted of CD8 or CD4 lymphocyte subsets demonstrate that tumour regression following therapeutic hspE7 immunization is CD8-dependent and CD4-independent. These studies extend previous observations on the induction of cytotoxic T lymphocytes by hsp fusion proteins and are consistent with the clinical application of hspE7 as an immunotherapy for human cervical and anal dysplasia and cancer.

Secretory heat-shock protein as a dendritic cell-targeting molecule: a new strategy to enhance the potency of genetic vaccines

“…These findings are consistent with data in earlier reports of recombinant HSP70 fusion proteins that included HIV-1 p24, 36 OVA, 37,39 influenza virus NP, 45 or HPV16 E7 38 as model antigens or E7/HSP70 fusion proteins released from dying cells. 46,47 However, it remains a mystery why the HSP-mediated presentation of E7 antigens did not induce CD4 þ T-helper responses, presumably through the receptor-mediated class II antigen presentation pathway.…”

“…Importantly, we detected a strong E7-specific antibody response in animals vaccinated with pCMV-Sig/E7/HSP70, in contrast to earlier reports on cytoplasmic E7/HSP70 constructs, in which vaccinated mice lacked antibody responses altogether. 38 Perhaps this antibody response is further evidence of physiologically relevant secretion of fusion protein after DNA vaccination. Even though antibody-mediated immune responses have not been shown to play an important role in controlling HPV16-associated malignancies, they may be effective against other tumors, such as the experimental HER2/Neu breast cancer model.…”

“…Finally, recombinant HSP-antigen fusion proteins 36,37 were able to elicit CD4 þ -independent CD8 þ cytotoxic T-lymphocyte (CTL) responses. [38][39][40] In the present study, we sought to enhance the potency of DNA vaccines by using HSP70 as a DC-targeting molecule to enhance antigen cross-presentation and DC maturation. This novel strategy (Figure 1a) uses the human papilloma virus type-16 E7 oncoprotein (HPV16 E7) as a model antigen and HSP70 as a DC binding domain.…”

Heat shock fusion protein induces both specific and nonspecific anti‐tumor immunity

“…Several members of the HSP family were shown to play important roles in activation of DC and cross-priming of CTL [12]. A fusion protein between mycobacterial HSP65 and human papillomavirus (HPV) E7 protein was developed to treat human HPV-associated diseases [13] and is now in phase III clinical trials for treating HPV-associated anal dysplasia, genital warts, recurrent respiratory papillomatosis and cervical dysplasia. A DNA vaccine expressing a secreted form of HPV-E7-HSP70 (a fusion protein between mycobacterial HSP70 and the HPV E7 protein) was demonstrated to strongly stimulate antigen-specific CD8 + T cell responses and inhibit the growth of established tumors in mice [14].…”

Identification of a naturally processed HLA‐A*0201 HPV18 E7 T cell epitope by tumor cell mediated in vitro vaccination

“…10 The viral oncogenes E6 and E7 are therefore unique tumor associated antigens, which tag the infected cells for recognition by the immune system and target transformed cells for destruction by cytolytic T lymphocytes (CTL). 11,12 In the majority of individuals, HPV-infection is controlled by the immune system of the host. Precancerous lesions regress spontaneously at high rates accompanied by lymphocyte infiltration in up to 50%.…”