Background

[PubMed]

Interleukin-18 (IL-18) is a proinflammatory cytokine produced by macrophages, epithelial cells, and activated T cells (1, 2), and it plays an important role in inflammation and immune response (3, 4). IL-18 induces production of tumor necrosis factor and IL-1 in mononuclear cells. A variety of normal and malignant cells can produce and respond to IL-18 through its receptor (IL-18R). A soluble secreted IL-18 binding protein (IL-18bp) was found to bind to IL-18 with high affinity (dissociation constant (K_d) = 0.4 nM) and to neutralize the biological effects of IL-18 by blocking its interaction with IL-18R (5, 6). IL-18bp-Fc is a 40-kDa glycoprotein with an immunoglobulin (Ig) domain.

The interleukin-1 family of two proinflammatory cytokines, IL-1α and IL-1β, which bind to two IL-1 receptors (IL-1R1 and IL-1R2), and an IL-1R antagonist (IL-1ra), is mainly produced by activated macrophages and tissue macrophages (7). IL-1α and IL-1β are important mediators of the inflammatory response and hematopoiesis, and they are involved in a variety of cellular activities, including cell proliferation, differentiation, and apoptosis. IL-1 is involved in chronic inflammatory diseases and in neuropathological conditions (8, 9). The balancing action of IL-1 and IL-1ra plays an important role in the regulation of inflammation and immune responses (10). IL-1ra has been shown to be effective as an anti-inflammatory treatment in several chronic inflammatory diseases and stroke (11, 12). A human recombinant, non-glycosylated form of the human IL-1ra (rhIL-1ra, Anakinra) has been approved by the United States Food and Drug Administration for the treatment of rheumatoid arthritis (13).

IL-1 and IL-18 exhibit additive or synergistic effects in promoting pathophysiological processes observed in many inflammatory diseases (14). A dual domain IL-18bp-Fc-IL-1ra fusion protein was constructed by joining IL-18bp and IL-1ra cDNA to the Fc fragment of human IgG₁ cDNA in an expression plasmid (15). The amino-terminal segment binds to IL-18, and the carboxyl-terminal sequence binds to the IL-1R. Liu et al. (15) radiolabeled IL-18bp-Fc-IL-1ra with ^99mTc via 2-iminothiolane reduction to produce ^99mTc-IL-18bp-Fc-IL-1ra for use with single-photon emission computed tomography (SPECT) imaging of inflammation in mice.

Synthesis

[PubMed]

Liu et al. (15) reported the synthesis of ^99mTc-IL-18bp-Fc-IL-1ra. IL-18bp-Fc-IL-1ra was incubated with 2-iminothiolane for 30 min at 37°C in phosphate-buffered saline (PBS, pH 7.4). A solution of 1,110 MBq (30 mCi) ^99mTcO₄− was added to a mixture of SnCl₂ and glucoheptonic acid and incubated at room temperature for 5 min to produce ^99mTc-glucoheptonate, which was then incubated with the thiolated IL-18bp-Fc-IL-1ra for 30 min at room temperature, with a radiolabel yield of 75%. ^99mTc-IL-18bp-Fc-IL-1ra was purified on a PD-10 column, with >95% radiochemical purity. The specific activity was 7.4–8.3 MBq/µg (0.20–0.22 mCi/µg). ^99mTc-IL-18bp-Fc-IL-1ra remained >95% intact for up to 5 h in both saline at room temperature and serum at 37°C.

In Vitro Studies: Testing in Cells and Tissues

[PubMed]

Liu et al. (15) performed binding competition experiments with ^99mTc-IL-18bp-Fc-IL-1ra (2 nM) and IL-18bp-Fc-IL-1ra (0.1–10,000 nM) using rat leukocytes, which contain both IL-18R and IL-1R. The IC₅₀ value for IL-18bp-Fc-IL-1ra was 73.56 nM.

Animal Studies

Human Studies

[PubMed]

No publication is currently available.

NIH Support

R01 HL090716, P41 EB002035

References

1.

Dinarello C.A. Interleukin-18. Methods. 1999;19(1):121–32. [PubMed: 10525448]

2.

Arend W.P., Palmer G., Gabay C. IL-1, IL-18, and IL-33 families of cytokines. Immunol Rev. 2008;223:20–38. [PubMed: 18613828]

3.

Dinarello C.A. Interleukin-18 and the pathogenesis of inflammatory diseases. Semin Nephrol. 2007;27(1):98–114. [PubMed: 17336692]

4.

Dinarello C.A., Fantuzzi G. Interleukin-18 and host defense against infection. J Infect Dis. 2003;187 Suppl 2:S370–84. [PubMed: 12792854]

5.

Dinarello C.A. Targeting interleukin 18 with interleukin 18 binding protein. Ann Rheum Dis. 2000;59 Suppl 1:i17–20. [PMC free article: PMC1766611] [PubMed: 11053080]

6.

Faggioni R., Cattley R.C., Guo J., Flores S., Brown H., Qi M., Yin S., Hill D., Scully S., Chen C., Brankow D., Lewis J., Baikalov C., Yamane H., Meng T., Martin F., Hu S., Boone T., Senaldi G. IL-18-binding protein protects against lipopolysaccharide- induced lethality and prevents the development of Fas/Fas ligand-mediated models of liver disease in mice. J Immunol. 2001;167(10):5913–20. [PubMed: 11698468]

7.

Dinarello C.A. Biologic basis for interleukin-1 in disease. Blood. 1996;87(6):2095–147. [PubMed: 8630372]

8.

McColl B.W., Allan S.M., Rothwell N.J. Systemic infection, inflammation and acute ischemic stroke. Neuroscience. 2009;158(3):1049–61. [PubMed: 18789376]

9.

Simi A., Tsakiri N., Wang P., Rothwell N.J. Interleukin-1 and inflammatory neurodegeneration. Biochem Soc Trans. 2007;35(Pt 5):1122–6. [PubMed: 17956293]

10.

Dinarello C.A., Simon A., van der Meer J.W. Treating inflammation by blocking interleukin-1 in a broad spectrum of diseases. Nat Rev Drug Discov. 2012;11(8):633–52. [PMC free article: PMC3644509] [PubMed: 22850787]

11.

Neven B., Marvillet I., Terrada C., Ferster A., Boddaert N., Couloignier V., Pinto G., Pagnier A., Bodemer C., Bodaghi B., Tardieu M., Prieur A.M., Quartier P. Long-term efficacy of the interleukin-1 receptor antagonist anakinra in ten patients with neonatal-onset multisystem inflammatory disease/chronic infantile neurologic, cutaneous, articular syndrome. Arthritis Rheum. 2010;62(1):258–67. [PubMed: 20039428]

12.

Emsley H.C., Smith C.J., Georgiou R.F., Vail A., Hopkins S.J., Rothwell N.J., Tyrrell P.J. A randomised phase II study of interleukin-1 receptor antagonist in acute stroke patients. J Neurol Neurosurg Psychiatry. 2005;76(10):1366–72. [PMC free article: PMC1739363] [PubMed: 16170078]

13.

Thompson R.C., Dripps D.J., Eisenberg S.P. Interleukin-1 receptor antagonist (IL-1ra) as a probe and as a treatment for IL-1 mediated disease. Int J Immunopharmacol. 1992;14(3):475–80. [PubMed: 1535616]

14.

Sims J.E. IL-1 and IL-18 receptors, and their extended family. Curr Opin Immunol. 2002;14(1):117–22. [PubMed: 11790541]

15.

Liu Z., Wyffels L., Barber C., Wan L., Xu H., Hui M.M., Furenlid L.R., Woolfenden J.M. Characterization of 99mTc-labeled cytokine ligands for inflammation imaging via TNF and IL-1 pathways. Nucl Med Biol. 2012;39(7):905–15. [PMC free article: PMC3443298] [PubMed: 22749187]