Preparation of fusion protein of PD-L1 single-chain antibody and verification of its antitumor activity / 中国免疫学杂志

ABSTRACT

Objective: Using yeast surface presentation technology, secreted anti-PD-L1 single-chain antibody fragment ( sc Fv), then purify the sc Fv that specifically binds PD-L1 antigen. The sc Fv antibody gene sequence was synthesized based on the single chain antibody gene sequence. We express this sc Fv-mFc protein by using p Fuse eukaryotic expression vector to study its affinity and in vitro and in vivo inhibition of lung adenocarcinoma cells ( A549). Methods: Recombinant plasmid p Fuse-scFv was constructed by gene engineering. The recombinant plasmid p Fuse-scFv was transfected into 293 F ( human embryonic kidney cells) and cultured in serum-free Pro293 a-CDM for 72 hours, then the fusion protein was collected, and use the Rapid Protein Liquid Phase Separation and Purification System to purify the sc Fv-mFc fusion protein. Then the fusion protein and the tumor cells were detected by immunohistochemistry; the affinity of fusion protein and tumor cells was analyzed by flow cytometry; ADCC was used to determine the proliferation of tumor cells in vitro. The nude mice inoculated with lung adenocarcinoma cells, and use the fusion protein to verify its anti-tumor effect in vivo. Results: sc Fv-mFc fusion protein was secreted into serum-free culture medium by recombinant plasmid transfection into the 293 F cells; immunohistochemistry and flow cytometry showed that the fusion protein was highly expressed with the surface of PD-L1 protein;ADCC showed that the fusion protein inhibited the proliferation of tumor cells in vitro; the results of tumor-bearing mice showed that the fusion protein inhibited the growth of the tumor. At the dose of 5 mg/kg, The tumor volume growth rate decreased from 14. 90％ to3. 72％, the two independent samples t test P＜0. 05, the difference was statistically significant. Conclusion: The fusion protein containing single chain antibody was successfully prepared, which had good binding ability to A549 cells and inhibited the proliferation of tumor cells in vitro and in vivo, and provided the laboratory basis for the development of targeted anti-tumor drugs.