Targeted mutagenesis with the aim of improving the binding of Avelumab antibody to antigen in cancer inhibition

Introduction: Cancer occurs due to the uncontrolled division of cells and their spread to other tissues from the primary origin. During tumorigenesis and the transformation of a normal cell into a malignant one, in addition to changing the signaling pathways, changes also occur in the tumor microenvironment. In the tumor microenvironment of T-lymphocyte cells, the antigen presented on the surface of the tumor cell identifies the antigen presenting through the histocompatibility complex and plays a role in inhibiting the tumor with cytotoxic activity. Tumor cell by expressing PDL-۱ on its surface inhibits recognition and suppression of the immune system and progresses. Programmed death ligand protein inhibits the activity and proliferation of T cells by binding to its ligand PD-۱ on the surface of T cells and also helps tumor progression by resisting apoptosis. Today, immunotherapy and the use of antibodies against this receptor have positive results in the treatment and prevention of cancer. Materials and Methods: In this study, the molecular structure of Avalumab antibody and PDL۱ antigen was obtained from PDB server and Sab Dab server and analyzed by PyMOL software. CDR sequence and essential amino acids in antigen binding were determined. Glycine amino acid was selected in CDR۳ at position ۱۰۲, the bond length of this amino acid was calculated from the antibody with two amino acids valine at position ۷۶ and glutamine at position ۷۷, then it was replaced by targeted mutagenesis with tryptophan amino acid and the bond length was again It was calculated. Results and Discussions: The glycine-۱۰۲ amino acid of cdr ۳ in the heavy chain of the antibody was linked with valine ۷۶ with a length of ۴.۵ angstroms and with glutamine with a length of ۵.۴ angstroms. Due to the long link length, these links are weak. By replacing amino acid glycine with tryptophan, the length of these bonds decreased to ۲.۹ and ۳.۶ angstroms, respectively. Conclusion: Anticancer treatments and immunotherapy targeting these proteins have been developed, and inhibitors targeting PD-L۱ have been clinically approved. Inhibition of PD۱/PDL۱ binding by antibodies leads to cytotoxic activity of T cells in the tumor microenvironment and tumor inhibition. Antibodies are members of a family of glycoproteins and heterodimeric proteins containing two light and heavy chains that play an important role in stimulating specific immune responses. The variable domain of antibody heavy chain can be divided into ۳ complementary determining regions. ۳ CDRs of the light chain and ۳ CDRs of the heavy chain form the antigen binding site. Engineered molecules are like monoclonal antibodies and are used to restore and strengthen the immune system against tumor cells. In this study, the monoclonal antibody Avelumab was considered to inhibit the PDL-۱ receptor. Substitution of amino acid glycine-۱۰۲ with tryptophan by targeted mutagenesis method reduced the bond length in the range of ۳ angstroms with amino acid valine-۷۶ and glutamine-۷۷, which indicates the improvement of antibody and antigen binding and inhibitory function of antibody.

کلیدواژه ها:

Cancer ، T cell ، Programmed death ligand protein