多次跨膜蛋白（MMPs）是单抗药物的重要分子靶点，但因为天然MMPs纯化困难导致其抗体研发缓慢。目前的解决手段包括改良抗原纯化方法或者用细胞荷载膜蛋白免疫动物。这些方法不但难以彻底解决抗原制备的问题，而且需要通过杂交瘤技术筛选抗体，费时费力，且无法直接获得全人抗体。为了提高MMPs抗体研发效率，本课题拟开发一种基于抗原抗体共展示技术的抗体文库筛查系统。该系统在酵母细胞膜表面同时展示MMPs抗原和抗体文库，通过所偶联的检测系统报告两者的相互作用。本系统通过融合跨膜肽将抗体展示在酵母细胞膜表面，替代了传统的细胞壁展示技术。这一策略使得MMPs得以在细胞膜表面与抗体文库直接对话，既保证了抗原的天然构象，又实现了抗体的文库筛查。同时，抗原抗体的亲和力通过克隆的生长速度得以直接观察，避免了盲目地对候选抗体亲和力的测定。该系统的建立将大大提升膜蛋白抗体开发的效率，有望成为MMPs抗体开发的主流技术。

Multi-pass membrane proteins (MMPs) are important molecular targets of monoclonal antibody drugs, however it is hard to develop their antibodies because of the difficulty of MMPs purification. Current methods include improving antigen purification methods or the cell-based membrane proteins immunization. These methods are not only difficult to completely solve the problem of antigen preparation, but also have to use hybridoma technology to select antibodies, which wastes time and energy and cannot directly obtain human antibody. In order to improve the efficiency of the development of MMPs antibody, this study aims to develop an antibody library screening system based on Antigen Antibody Co-Display (AACD) technology. The system displays both the MMPs and the antibody library on the surface of yeast cell membrane, and reports the interactions between them by the coupled detection system. In AACD system, the antibody was displayed on the surface of yeast cell membrane through a transmembrane peptide fused at the N-terminus of antibody. This strategy enables MMPs and antibodies to directly interact on the surface of cell membrane, which not only ensures the natural conformation of antigen, but also realizes the screening of antibody library. At the same time, the affinity of antigen-antibody can be observed directly by the growth rate of clones, so as to avoid the pointless affinity assay of the plenty of candidate antibodies. The establishment of this system will greatly improve the efficiency of the development of MMPs antibody, and it is expected to become the mainstream technology in MMPs antibody development.