Structural Analysis of Immunotherapeutic Peptides for Autoimmune Myasthenia Gravis

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• 作者：Hyun Ho Jung ; Hwa Jung Yi ; Seung Kyu Lee ; Ju Yeon Lee ; Hoi Jong Jung ; Sung Tae Yang ; Young-Jae Eu ; Sin-Hyeog Im ; Jae Il Kim
• 刊名：Biochemistry
• 出版年：2007
• 出版时间：December 25, 2007
• 年：2007
• 卷：46
• 期：51
• 页码：14987 - 14995
• 全文大小：491K
• 年卷期：v.46,no.51(December 25, 2007)
• ISSN：1520-4995

文摘

Myasthenia gravis (MG) and its animal model, experimental MG (EAMG), are autoimmunedisorders in which major pathogenic antibodies are directed against the main immunogenic region (MIR)of the nicotinic acetylcholine receptor (nAChR). In an earlier attempt to develop peptide mimotopes capableof preventing the anti-MIR-mediated pathogenicity, the peptide Pep.1 was initially identified from phagedisplay, and subsequently, Cyclic extended Pep.1 (Cyc.ext.Pep.1), which incorporates eight additionalresidues into the Pep.1 sequence and has an affinity for the anti-MIR antibody mAb198 3 orders ofmagnitude greater than that of Pep.1, was developed. In an animal model, Pep.1 shows no ability toinhibit mAb198-induced EAMG, whereas Cyc.ext.Pep.1 successfully blocks anti-MIR antibody 198(mAb198)-induced EAMG. Our aim in this study was to identify the structural characteristics related tothe different affinities for mAb198 of Pep.1 and Cyc.ext.Pep.1 using NMR spectroscopy and alaninescanning analysis. The NMR structural analysis revealed that Pep.1 is very flexible in solution, whereasCyc.ext.Pep.1 is highly rigid within a region containing several turn structures. Interestingly, TRNOEexperiments revealed that mAb198-bound Pep.1, particularly in the region between Asn7 and Glu11,shows significant structural similarity to the region between Asn10 and Glu14 of Cyc.ext.Pep.1, which iscritical for interaction with mAb198. We therefore conclude the higher affinity of Cyc.ext.Pep.1 for mAb198reflects the fact that incorporation of additional residues producing a single disulfide bond endows Pep.1with a conformational rigidity that mimics the structure of mAb198-bound Pep.1. Furthermore, our resultssuggest that cyclic extended peptides could be utilized generally as useful tools to optimize the affinityof phage library-derived peptide antigens.