An affibody is a 58 amino acids peptide derived from the Z domain of staphylococcal protein A and generally applied in areas such as imaging diagnosis, clinical therapeutics and biotechnology research. To screen for an affibody targeting the immune checkpoint PD-L1, a combinatorial affibody library was generated in yeast using degenerate overlap PCR primers and In-fusion technology. Z-j1 and Z-j2 affibodies targeting the Ig-like V domain of PD-L1 were screened and identified from this combinatorial library using the yeast two hybrid system. The Z-j1 and Z-j2 recombinant affibody proteins were over produced in E.coli and purified. ELISA and GST pull-down assays showed that recombinant Z-j1 and Z-j2 affibody proteins bound with high affinity to PD-L1 and inhibited the interaction of PD-1/PD-L1. Thus, novel affibodies targeting the immune checkpoint PD-1/PD-L1 were identified and produced in this study and have the potential to be used in cancer immunotherapy.

中文翻译：

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抑制PD-1 / PD-L1免疫检查点相互作用的亲和体的筛选和生产。

亲和体是衍生自葡萄球菌蛋白A的Z结构域的58个氨基酸的肽，通常用于成像诊断，临床治疗和生物技术研究等领域。为了筛选靶向免疫检查点PD-L1的亲和体，使用简并重叠PCR引物和In-fusion技术在酵母中生成了组合亲和体文库。使用酵母两杂交系统，从该组合文库中筛选并鉴定了靶向PD-L1 Ig样V结构域的Z-j1和Z-j2亲和力。Z-j1和Z-j2重组亲和体蛋白在大肠杆菌中过量生产并纯化。ELISA和GST下拉分析表明重组Z-j1和Z-j2亲和体蛋白与PD-L1具有高亲和力，并抑制了PD-1 / PD-L1的相互作用。因此，