Creation of an improved mutant TNF with TNFR1-selectivity and antagonistic activity by phage display technology

Tumor necrosis factor-α (TNF), which binds two types of TNF receptors (TNFR1 and TNFR2), regulates the onset and exacerbation of autoimmune diseases such as rheumatoid arthritis and Crohn's disease. In particular, TNFR1-mediated signals are predominantly related tothe induction of inflammatory responses. We have previously generated a TNFR1 -selective antagonistic TNF-mutant (mutTNF) and shown that mutTNF efficiently inhibits TNFR1-mediated bioactivity in vitroand attenuates inflammatory conditions in vivo. In this study, we aimed to improve the TNFR1-selectivity of mutTNF. This was achieved by constructing a phage library displaying mutTNF-based variants, in which the amino acid residues at the predicted receptor binding sites were substituted to other amino acids. From this mutant TNF library, 20 candidate TNFR1- selective antagonists were isolated. Like mutTNF, all 20 candidates were found to have an inhibitory effect on TNFR1 -mediated bioactivity. However, one of the mutants, N7, displayed significantly more than 40-fold greater TNFR1-selectivty than mutTNF. Therefore, N7 could be a promising anti-autoimmune agent that does not interfere with TNFR2-mediated signaling pathways.