| Although cancer vaccines can induce immune response against tumour in animal models or patients, the use of cancer vaccines for solid tumors, especially when other immunotherapeutic approaches currently in preclinical and clinical trials have shown far more positive results. There are many kinds of mechanism for tumor immune escape. Eliminating both tumor and lymphocyte-mediated immune suppressive mechanisms without adversely affecting the desired antitumor effector cells holds great promise.B7-H1, a new member of B7 family of co-stimulatory molecules, is involved in regulation of T cell function and cytokine secretion through the PD-1/non-PD-1 receptor on T and B cells. Immunohistochemistry analysis showed B7-H1 is scarcely expressed in normal tissue, but is expressed in a majority of freshly isolated cancer cells, such as human lung, ovarian, colon, melanoma, head and neck cancers, and breast cancers. Cancer cell–associated B7-H1 increases apoptosis of antigen-specific human T-cell clones in vitro and in vivo. Recently, it is suggested that B7-H1 played an important role in tumor immune escape. Blocked of B7-H1, by anti mouse B7-H1 monoclonal antibody, could delay tumor growth and prolong the survival on tumor-bearing mice. Our previous study also showed B7-H1 vaccine induced high-titer anti-B7-H1 Ab, which could inhibit the growth of B7-H1+SP20 metastatic tumor . HER-2/neu is known to be overexpressed in many epithelial tumors and HER-2/neu overexpression represents a marker of poor prognosis. So,HER-2/neu has been considered as a potential target for immunotherapy. In addition, the"humanized"monoclonal antibody Herceptin has been proved to be an effective adjuvant therapy for HER-2/neu-positive breast and ovarian cancers by FDA. HER-2/neu can be immunogenic and generate antibody production and activation of peptide-specific CTLs and T helper (Th) cells, so, active vaccination–HER2/neu vaccine has potential advantages. Vaccination strategie about HER2/neu come out one after the other, including the There are various vaccination approaches to immunotherapy targeting the HER-2/neu molecule, including peptide vaccine, gene vaccine, gene-modified cell vaccine, and so on. However, HER-2/neu, as a self-antigen, induces active tolerance and there are many kinds of mechanism for tumor immune escape, vaccination targeting the HER-2/neu molecule is remaining far from expectation.According to literature, a truncated HER2-ECD was chosen to construct HER-2 vaccine, which includes more antigen epitopes. The gene of fragment (aa 511-629) of HER-2 extracellular domain was cloned into the multiple cloning site of pRc/CMV with The signal peptide genes which were inserted upstream of HER-2 to mediate its secretion. Thus, we constructed HER2 gene vaccine, also called CH-vaccine. The same HER-2 sequence was cloned into the multiple cloning site of pQE-30, then it was transformed into E. coli DH5α. HER2-ECD fragment was expressed in DH5αand purified through Ni-NTA resin affinity chromatography. Thus, we achieved HER2-ECD peptide vaccine,also called pH vaccine. Otherwise,E. coli strain including pQE-30-TT-B7-H1IgV plamid was actived and rhB7-H1 protein was expressed and purified according to previous purification-procedure.CH and pH vaccines were used to immunize BALB/c mice combination with B7-H1vaccine. Titer of Ab and CTL response were identified by ELISA and ELISPOT. The result showed that B7-H1 vaccine could enhance HER2-specific humoral immunity and cell immunity elicited by CH and pH vaccines. To identify whether combination B7-H1vaccine with HER2 vaccines have stronger effect of tumor-inhibition, BALB/c mice after immunization were challenged with HER-2/neu+EMT6. The result showed that vaccine could inhibit the growth of tumor and that B7-H1 vaccine could enhance effect of HER-2 vaccines against EMT6 tumors .Besides, the effect of vaccines to tumor-bearing mice was observed. The result showed that vaccine could suppress tumor growth to some extent. Although individual variation of tumor volume was big, it seemed that combining usage of vaccine inhibited tumor growth more effective.At last, toxicology study on vaccines was analyzed. We observed body weights, food consumption, clinical signs, local tolerance, hematology, serum biochemistry, complete necropsy, histopathology of main organ and lymphocyte phenotyping by flow cytometry. The result showed that weight of the mice treated by gene vaccines became lower than others and several items of hematology and serum biochemistry in several animal have little changes. Visible changes were not found in main organs for macropathology and histopathology. The CD4+T cell level of almost all vaccination groups became higher, and this phenomenon might suggest to generate immune response.In short, our study confirm that B7-H1 vaccine and HER2 vaccine have synergism, and B7-H1 can impove HER2-specific humoral and cellular immunity responses and then impove the effect of HER-2 vaccines against EMT6 tumors. The study provides new idea and evidence for designing tumor vaccine which not only can induce strong tumor-specific immune response, but also can block tumor immue escape. |
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