Suppression of the inflammatory cytokine IL-18 activity by controlling the receptor function

2000 Fiscal Year Final Research Report Summary

• Project/Area Number: 10480158
• Research Category: Grant-in-Aid for Scientific Research (B).
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Structural biochemistry
• Research Institution: Osaka University
• Principal Investigator: AIMOTO Saburo Institute for Protein Research, Professor, たんぱく質研究所, 教授 (80029967)
• Co-Investigator(Kenkyū-buntansha): KASHIWAMURA Shinichiro Hyogo Medical University, Associate Professor, 先端医学研究所, 講師 (00185761) ; OKAMURA Haruki Hyogo Medical University, Professor, 先端医学研究所, 教授 (60111043) ; KAWAKAMI Toru Institute for Protein Research, Instructor, たんぱく質研究所, 助手 (70273711)
• Project Period (FY): 1998 – 2000
• Keywords: interleukin-18 / antagonist / synthetic peptide / interferon γ / phage library

Research Abstract

Interleukin 18 (IL-18) is a cytokine that induces the production of interferon γ, acute hepatitis, rheumatism, self-immune reaction and so on. In order to suppress the inflammatory effect of IL-18, we searched the compounds that control the IL-18 activity.
1. Search of antibodies that inhibit IL-18 binding to its receptor
Peptides that cover all sequence of the outer cellular domain of IL-18 receptor were synthesized. Using the peptide, peptide conjugates with KHL hemocyanine and BSA were prepared and immunized. However, no antigen that inhibits IL-18 activity was obtained.
2. Evaluation of characteristics of trans-membrane domains of IL-18 receptor in terms of interference of the signal transaction through the receptor
In order to know the effect of the segment corresponding to the trans-membrane domain of the receptor to the signal transaction into cell, several segments of the trans-membrane domain were synthesized. However, no segments were able to be dissolved by detergents.
3. Search of phages that quench the function of IL-18 receptor
Phagemid libraries were prepared by using pSKAN Phagemid Display System (MoBiTec). However, phages themselves induce the production of interferon γ production. Therefore, we could not estimate the effect of peptides displayed on the phages.
4. Search of peptides that suppress the IL-18 activity
IL-18 is predicted to have a similar 3D structure to that of IL-1β and the complex crystal structure of IL-1β and IL-1 receptor has been solved. Based on the date deduced from the 3D structure, we synthesized partial sequences of IL-18 and evaluated the effects on the inhibition of IL-18 activities. As results, peptide, IL-18(113-157) and a mixture of IL-18(113-157) and IL-18(46-66) strongly inhibit the production of IFN-γ by L-18 addition.
In conclusion, the mixture of the partial sequences of IL-18 suppresses the IL-18 activity and this fact will present a solid basis for designing inhibitors against IL-18.