Isolation of CD200 specific peptides based on phage display technology

Abstract

Immune checkpoint inhibitors represent a class of drugs designed to impede the activity of proteins constituting the immune checkpoint expressed on T cells or tumor cells. These inhibitors play a crucial role in assisting T cells to eliminate cancer cells, providing a potential avenue for anticancer therapy. CD200 (OX-2 membrane glycoprotein) can be considered an interesting target for immune checkpoints. The interaction between CD200 and its receptor, CD200R, has been implicated in immune-related diseases, including allergic diseases, infections, arthritis, transplantation, and autoimmune diseases such as multiple sclerosis and systemic lupus erythematosus. Experiments were designed to screen for anti-CD200 peptides that bind to CD200 to interfere with the binding of CD200 to CD200R. To obtain CD200, the protein was expressed using a mammalian expression system, with HEK (Human embryonic kidney) cells chosen for their high-efficiency expression. Ni-NTA chromatography was performed for protein purification, followed by protein MS to check for impurities. Phage display technology, a screening method recognizing interesting candidates based on binding affinity for a given target molecule, was used to screen peptides binding specifically to CD200. After three rounds of biopanning, phage plaques were selected, amplified, purified, and DNA sequencing was performed. As a result, the 12-mer peptide sequence was identified. The sequence chosen through further analysis is anticipated to possess the potential as an antagonist capable of blocking the interaction between CD200 and CD200R.