Background

[PubMed]

Interleukin-18 (IL-18) is a proinflammatory cytokine produced by macrophages and activated T cells (1, 2), and it plays an important role in inflammation and immune response (3, 4). 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 neutralize the biological effects of IL-18 by blocking its interaction with IL-18R (5, 6). IL-18bp is a 40-kDa glycoprotein with an immunoglobulin (Ig) domain. Cao et al. (7) constructed a divalent IL-18bp-Fc fusion protein by joining IL-18bp cDNA to the CH₂ and CH₃ domains of human IgG₁ in an expression plasmid. IL-18bp-Fc binds human, mouse, and rat IL-18 with subnanomolar affinity (6). 1,4,7,10-Tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA) has been successfully coupled to IL-18bp-Fc and labeled with ⁶⁴Cu to produce a molecular imaging agent with the potential to target breast cancer lung metastasis. ⁶⁴Cu is a positron emitter with a physical half-life of 12.7 h and is suitable for positron emission tomography (PET) imaging.

Synthesis

[PubMed]

Cao et al. (7) reported the synthesis of ⁶⁴Cu-DOTA-IL-18bp-Fc. DOTA was activated by 1-ethyl-3-[3-(dimethylamino)-propyl]carbodiimide (EDC) and N-hydroxysulfonosuccimide (SNHS) (pH 5.5) for 30 min with a molar ratio of 10:5:4 (DOTA/EDC/SNHS). The DOTA-IL-18bp-Fc conjugate was purified with a PD-10 column, and the number of DOTA molecules per protein molecule was 2.5. For radiolabeling, 30 μg DOTA-IL-18bp-Fc was added to 37 MBq (1 mCi) ⁶⁴CuCl₂ diluted in 300 μl of 0.1 M sodium acetate buffer. The reaction mixture was incubated for 1 h at 40ºC. ⁶⁴Cu-IL-18bp-Fc was purified with PD-10 column chromatography with a radiolabeling yield of 21%. The specific activity and radiochemical purity of ⁶⁴Cu-DOTA-IL-18bp-Fc were not reported.

In Vitro Studies: Testing in Cells and Tissues

[PubMed]

Faggioni et al. (6) performed binding experiments with IL-18bp-Fc with the use of a Biacore sensor chip immobilized with human, mouse, or rat IL-18 with K_d values of 4.99, 0.33, and 1.84 nM, respectively. No binding data were reported for DOTA-IL-18bp-Fc.

Animal Studies

Human Studies

[PubMed]

No publication is currently available.

NIH Support

R01 CA119053, R21 CA121842, R21 CA102123, P50 CA114747, U54 CA119367, R24 CA93862

References

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

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

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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.

Cao Q., Cai W., Niu G., He L., Chen X. Multimodality imaging of IL-18--binding protein-Fc therapy of experimental lung metastasis. Clin Cancer Res. 2008;14(19):6137–45. [PubMed: 18829492]