Immunotherapy of a human papillomavirus (HPV) type 16 E7-expressing tumourby administration of fusion protein comprising Mycobacterium bovis bacilleCalmette-Guerin (BCG) hsp65 and HPV16 E7

Human papillomavirus type 16 (HPV16) infection has been linked to the devel opment of cervical and anal dysplasia and cancer. One hallmark of persisten t infection is the synthesis of the viral E7 protein in cervical epithelial cells. The expression of E7 in dysplastic and transformed cells and its re cognition 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 adminis tration of an adjuvant-free fusion protein comprising Mycobacterium bovis B CG heat shock protein (hsp)65 linked to HPV16 E7 (hspE7) has been developed . The data show that prophylactic immunization with hspE7 protects mice aga inst challenge with TC-1 cells and that these tumour-free animals are also protected against re-challenge with TC-1 cells. In addition, therapeutic im munization with hspE7 induces regression of palpable tumours, confers prote ction against tumour re-challenge and is associated with long-term survival (> 253 days). In vitro analyses indicated that immunization with hspE7 lea ds to the induction of a Th1-like cell-mediated immune response based on th e pattern of secreted cytokines and the presence of cytolytic activity foll owing antigenic recall. In vivo studies using mice with targeted mutations in CD8 or MHC class II or depleted of CD8 or CD4 lymphocyte subsets demonst rate 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 h uman cervical and anal dysplasia and cancer.