获得性抗性是曲妥株单抗治疗HER2+乳腺癌的主要障碍，因此值得寻找其他治疗策略如抗HER2瘤苗。然而，肿瘤免疫耐受是当今瘤苗免疫治疗的重要挑战。成熟树突状细胞囊泡靶向的T细胞疫苗（T-EXO）能够有效刺激CD8+ CTL和免疫记忆，提示其是一种有潜力打破肿瘤自身耐受的新型瘤苗。本课题利用人HER2和HLA-A2.1双转基因小鼠HER2/HLA-A2.1和大鼠neu转基因小鼠FVBneuN，研究T-EXOHER2/neu诱导HER2/neu特异性CTL反应及保护性抗肿瘤免疫效能；并体外扩增HLA-A2.1和H-2Kq限制性的HER2/neu特异性CTLs，研究其对肿瘤靶细胞的体外直接杀伤效应，和对曲妥株单抗敏感和抗性的人乳腺癌裸鼠原位移植瘤的体内治疗功效。该课题将为HER2+尤其是曲妥株单抗抗性的乳腺癌病人提供一种新的治疗选择，并且为T-EXO疫苗在肿瘤免疫治疗中的应用提供实验依据。

One of the major obstacles in trastuzumab targeted therapy (passive immunotherapy) for human epeidermal growth factor receptor (HER2)-overexpressing breast cancer is the development of trastuzumab acquired resistance，warranting the search for other therapeutic strategies such as anti-HER2 cancer vaccine-based active immunotherapy. However, tumor immune tolerance and immunosuppressive microenvironment is currently an important challenge for cancer vaccine. Antigen-loaded mature dentritic cell (DC)-derived exosome (EXO)-targeted T cell-based vaccine (T-EXO) can efficiently stimulate antigen-specific CD8+ cytotoxic T lymphocyte (CTL) responses and long-term CTL memory via exosomal peptide/major histocompatibility complex (pMHC)-I，CD80 and endogenous IL-2 and CD40L signalling, suggesting a novel and promising cancer vaccine capable of potentially breaking self-tolerance to tumor-associated antigens (TAAs). Therefore, in this project, we will firstly culture bone marrow-derived DC (BM-DC) from HLA-A2.1 transgenic and FVB/NJ mice and prepare HER2/neu-specfic T-EXOHER2 and T-EXOneu anti-HER2/neu vaccine using adenoviral vectors (AdVHER2 expressing HER2 and AdVneu expressing neu)-infected BM-DC (DCHER2 and DCneu)-secreted EXOs (EXOHER2 and EXOneu). Then we assess the stimulatory effect of T-EXOHER2 on in vivo HER2-specfic CD8+ CTL responses by tetramer assay and CTL-mediated preventive and therapeutic antitumor immunity using HLA-A2.1/HER2 double gene-transfected B16HLA-A2.1/HER2 mouse melanoma cells in HER2/HLA-A2.1 double transgenic mice expressing human HER2 and human MHC class I molecule HLA-A2.1 with HLA-A2.1-restricted self-tolerance to human HER2; and also assess the stimulatory effect of in vivo T-EXOneu on neu-specfic CD8+ CTL responses by tetramer assay and CTL-mediated preventive and therapeutic antitumor immunity using neu-expressing Tg1-1 breast cancer cells in FVBneuN transgenic mice expressing rat neu with self-tolerance to rat neu and spontaneous development of mammary tumors. Lastly, we in vitro amplify HER2/neu-specific CD8+ CTLs (CTLHER2 and CTLneu) and investigate their killing activity to B16HLA-A2.1/HER2 and Tg1-1 tumor target cells in vitro, respectively. More importantly, we further evaluate the therapeutic effect of CTLHER2 on trastuzumab-resistant BT474HLA-A2.1 as well as trastuzumab-sensitive MCF-7 human breast cancer cells in vitro and in vivo in 7-day BT474HLA-A2.1 and MCF-7 xenograft tumors implanted in mammary fat pads of BALB/c nude mice. This project will provide a new therapeutic alternative for women with HER2-postive breast cancer, especially for trastuzumab-resistant breast cancer patients, and lay the experimental foundation for the application of novel exosome-targeted T cell-based vaccine in cancer immunotherapy.