A novel domain antibody rationally designed against TNF-α using variable region of human heavy chain antibody as scaffolds to display antagonistic peptides

Neutralizing of TNF-α has been proved effective in treatment of some autoimmune diseases, e.g. rheumatoid arthritis and Crohn's disease. Low molecular weight synthetic peptides can mimic the binding sites of TNF-α receptors and block the activity of TNF-α. In order to stabilize the conformation, increase the affinity and bioactivity, in this study, heavy chain variable region of human antibody was used as a scaffold to simultaneously display three peptides, which were designed on the interaction between TNF-α and it's neutralizing monoclonal antibody. On the basis of the structural character and physical–chemical property of the families of seven kinds of heavy chain variable regions (VH) in human antibodies, the fifth type of VH was screened as scaffold to display the antagonist peptide. Based on the computer-guided molecular design method, a novel domain antibody against TNF-α (named as ATD5) was designed as TNF-α antagonist. The theoretical study showed that ATD5 was more stable than displayed antagonist peptide. The binding activity with TNF-α was higher than free peptides. After expression and purification in Escherichia coli, ATD5 could bind directly with TNF-α and inhibit the binding of TNF-α to its two receptors, TNFR1 and TNFR2. ATD5 could also reduce the TNF-α-mediated cytotoxicity and inhibit TNF-α-meditated caspase activation on L929 cells in a dose dependent manner. The activity of ATD5 was significantly stronger than three peptides displayed by ATD5. This study provides a novel strategy for the development of new TNF-α inhibitors. This study demonstrates that it is possible to screen potential antagonists of TNF-α using in vitro analysis systems in combination with the computer-aided modeling method.