Immunotherapy of a human papillomavirus type 16 E7-expressing tumor by administration of fusion protein comprised of Mycobacterium bovis BCG Hsp65 and HPV16 E7 - PubMed (original) (raw)

Immunotherapy of a human papillomavirus type 16 E7-expressing tumor by administration of fusion protein comprised of Mycobacterium bovis BCG Hsp65 and HPV16 E7

N R Chu et al. Cell Stress Chaperones. 2000 Nov.

Abstract

Human 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 tumor cell line, TC-1, as a model of cervical carcinoma, an immunotherapy based on the administration of an adjuvant-free fusion protein comprised of Mycobacterium bovis BCG Hsp65 linked to HPV16 E7 (HspE7) has been developed. Initial in vitro analyses indicate that immunization with HspE7 results in the induction of a type 1 immune response based on the pattern of secreted cytokines and the presence of cytolytic activity following antigenic recall. It has been previously shown that prophylactic immunization with HspE7 protected mice against challenge with TC-1 cells and that these tumor-free animals are also protected against rechallenge with TC-1 cells. The present report shows that a single therapeutic immunization with HspE7 induces regression of palpable tumors, confers protection against tumor rechallenge, and is associated with long-term survival (>253 days). In vivo studies using mice with targeted mutations in CD8 or MHC class II or depleted of CD8 or CD4 lymphocyte subsets demonstrate that tumor regression following therapeutic HspE7 immunization is CD8 dependent and CD4 independent. These studies extend previous observations on the induction of CTL by Hsp fusion proteins and are consistent with the clinical application of HspE7 as an immunotherapy for human cervical and anal dysplasia and cancer.

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Figures

Fig 1.

Fig 1.

A single therapeutic immunization with HspE7 induces TC-1 tumor regression and promotes long-term survival. C57BL/6 mice were injected SC in the hind flank with 1.3 × 105 TC-1 cells (day 0). Seven days postimplantation, when measurable tumor (2 × 2-mm minimum) was apparent in all animals, mice were arbitrarily assigned into groups (17 to 18 animals per group) and immunized SC in the scruff of the neck with either PBS, 1.4 nmol of (h)E7, or 1.4 nmol HspE7 (arrow). The same cohorts of PBS (O), (h)E7 (▵), or HspE7 (▪)-treated mice were used to produce the data displayed in (A), (B), and (C). (A) Percentage tumor incidence in mice receiving HspE7 therapy. Mice were scored for the presence or absence of a palpable SC tumor nodule for 50 days postimplantation. (B) Individual tumor volumes from mice receiving HspE7 therapy. Tumor volumes of SC nodules were assessed for 50 days postimplantation. (C) Long-term survival in mice receiving HspE7 therapy. Mice were monitored for survival over a 253-day period postimplantation. Mice that became moribund because of tumor burden were sacrificed. Time to death is plotted on a Kaplan-Meier survival curve (reprinted with permission; see author's note).

Fig 2.

Fig 2.

Tumor regression following HspE7 immunization is CD8 dependent and CD4 independent. (A) and (B) Antibody-depleted or nondepleted mice were injected SC in the hind flank with 1.3 × 105 TC-1 cells (day 0). Seven days postimplantation (arrow), a depleted and nondepleted group of mice (12 to 15 animals per group) were treated with 1.4 nmol HspE7, as indicated in the legend. A third group was treated with PBS. The presence of SC tumor was monitored for 37 or 39 days. Data are presented as percent tumor incidence per group. (A) CD8+ T cell–depleted mice using MoAb 53.6-72; (B) CD4+ T cell-depleted mice using MoAb GK1.5. (C) Mice with a targeted mutation in CD8α (CD8 KO) or the β chain of Ab (class II KO) were implanted with 1.3 × 105 TC-1 cells SC in the hind flank. Seven days later (arrow), the CD8 KO and class II KO cohorts were divided into 2 groups (9 to 10 per group) and immunized with PBS or 1.4 nmol HspE7, as indicated in the legend. The presence of SC tumor was monitored for 42 days. Data are presented as percentage tumor incidence per group (reprinted with permission; see author's note)

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