Programmed death receptor-ligand 1 (PD-L1) specific binding polypeptide and application thereof

Abstract

The invention relates to a programmed death receptor-ligand 1 (PD-L1) specific binding polypeptide and application thereof, and belongs to the technical field of biology. The polypeptide is obtained by mutating 1-20 amino acid residues from a staphylococcus protein A (SPA) immunoglobulin binding region (the sequence of the polypeptide is shown in SEQ ID: 2-5), and the polypeptide can specifically bind to PD-L1 and block PD-1 / PD-L1 interaction. According to the invention, a PD-L1 specific binding polypeptide coding sequence is obtained by panning from a total synthesis affinity small body polypeptide molecular library through four rounds of enrichment, a prokaryotic expression system is utilized to prepare the obtained polypeptide in a large scale, and the polypeptide is specifically bound with PD-L1, has no obvious affinity with BSA protein, and can be used for PD-L1 detection. The polypeptide has the PD-1 / PD-L1 interaction blocking capability at the same time, and the PD-1 / PD-L1 interaction blocking capability of the polypeptide is enhanced along with the increase of the concentration.

Description

technical field [0001] The present invention belongs to the field of biotechnology, and specifically relates to a polypeptide specifically binding to programmed cell death-Ligand 1 (PD-L1), or a variant thereof, or a functional fragment thereof, and the Use of polypeptides, or variants thereof, or functional fragments. Background technique [0002] Immune checkpoint (immune checkpoint) is a signaling pathway in the immune system that regulates the strength of T cell immune response through co-signaling (co-stimulation or co-inhibition) molecules, and is crucial for maintaining autoimmune tolerance under normal physiological conditions. Programmed cell death 1 (PD-1) is an important negative regulator of immune cell activation, which can play an immunosuppressive role by binding to its ligand. PD-1 is mainly expressed on the surface of activated effector T cells, regulatory T cells, B cells, monocytes, and natural killer T cells, not on resting T cells, but can be detected w...

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Problems solved by technology

[0003] In recent years, immune checkpoint blockade therapy targeting PD-1 / PD-L1 immune checkpoint has achieved great success in the field of tumor immunotherapy, among which PD-1 / PD-L1 monoclonal antibody inhibitors have been used in Significant curative effect in clinical tumor treatment (Liu B, Song Y, et al.Recent development in clinical applications of PD-1 and PD-L1 antibodies for cancer immunotherapy. Journal of Hematology&Oncology, 2017, 10(1): 174), including the observation The tumor shrunk significantly and produced a durable immune response in tumor patients. However, as a large four-polypeptide chain protein (molecular weight ~150kDa), monoclonal antibody drugs have inherent disadvantages related to their complex molecular structure: ①Complicated structure , the preparation is more difficult, the production cost increases, resulting in high treatment costs and limited wide application

② Poor stability, highly sensitive to external conditions, some common external disturbances will lead to loss of antibody activity, special transportation and storage conditions are required to ensure its activity

③The molecule is relatively large, and has poor ability to penetrate tumor tissue, and cannot effectively transport to the inside of tumor tissue. The drug concentration at the tumor site is very low, and the treatment effect on solid tumors is not good.

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