A phage-displayed mimotope inhibits tumour necrosis factor-alpha-induced cytotoxicity more effectively than the free mimotope.

A phage-displayed peptide library was screened by direct interaction with human tumour necrosis factor-alpha (TNF-alpha) to identify novel antagonistic molecules of its biological activities. After several rounds of affinity selection, a phage displaying a mimotope sequence was shown to strongly inhibit, in a dose-dependent fashion, both mouse and human TNF-alpha-mediated cytotoxicity in L929 cells. The identified mimotope did not bear any sequence homology to the primary structures of the extracellular domains of either the 55 000 MW or the 75 000 MW TNF-alpha receptors, suggesting that it represents or mimics a conformational epitope involved with binding to TNF-alpha. The free 15-mer mimotope weakly inhibited TNF-alpha-induced cytotoxicity in vitro, and it did not bind to TNF-alpha as assessed by surface plasmon resonance, demonstrating the importance of mimotope presentation for its biological activities. In conclusion, this study highlights the potential of random combinatorial peptide libraries for the identification of novel inhibitors, which may serve as important tools in research that could lead to the development of TNF-alpha antagonists with therapeutic potential.