title: Engineering human IL-18 with increased bioactivity and bioavailability.
abstract: Cytokines in plasmid form can act as potent adjuvants when co-administered with DNA vaccines, resulting in an enhanced immune response to the DNA-encoded antigen. This is true of interleukin-18 (IL-18), which has been shown to serve as an adjuvant in conjunction with certain DNA vaccines. To determine if the properties of IL-18 could be optimized for use as a DNA vaccine adjuvant, a model of IL-18/IL-18R binding was developed to identify variants of human IL-18 that were predicted to improve receptor interactions and potentially bioactivity. The linkage of mature IL-18 to a secretion signal sequence provided improved protein expression from mammalian cells and signal peptidase cleavage of this protein produced the authentic N-terminus. The IL-18 variant proteins secreted this way were bioactive, as demonstrated by their ability to induce interferon gamma (IFNgamma) expression by human peripheral blood mononuclear cells (PBMCs) and to bind to IL-18R, as demonstrated by BIAcore analysis. The IL-18 variants were inhibited by IL-18 binding protein (IL-18BP), the soluble inhibitor of IL-18, as measured by neutralization of the IFNgamma response in PBMCs. One variant, V11I/T63A, demonstrated increases both in bioactivity and mammalian cell expression as compared to native IL-18, indicating that this molecule may be particularly well suited for use as a DNA-encoded vaccine adjuvant.
authors.affiliation: Centocor Inc., Biopharmaceutical Research, 145 King of Prussia Road, Radnor, PA 19087, USA. bswenck2@cntus.jnj.com
authors.forename: Bethany
authors.initials: B
authors.lastname: Swencki-Underwood
authors.forename: Mark R
authors.initials: MR
authors.lastname: Cunningham
authors.forename: George A
authors.initials: GA
authors.lastname: Heavner
authors.forename: Cheryl
authors.initials: C
authors.lastname: Blasie
authors.forename: Stephen G
authors.initials: SG
authors.lastname: McCarthy
authors.forename: Tara
authors.initials: T
authors.lastname: Dougherty
authors.forename: Mike
authors.initials: M
authors.lastname: Brigham-Burke
authors.forename: George R
authors.initials: GR
authors.lastname: Gunn
authors.forename: Theresa J
authors.initials: TJ
authors.lastname: Goletz
authors.forename: Linda A
authors.initials: LA
authors.lastname: Snyder
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D014644:Genetic Variation; D006801:Humans; D007371:Interferon-gamma / Q000235:genetics; D020382:Interleukin-18 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010957:Plasmids / Q000378:metabolism; D015202:Protein Engineering / Q000379:methods*; D017434:Protein Structure, Tertiary; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014162:Transfection; D019444:Vaccines, DNA / Q000235:genetics
chemical_list: D020382:Interleukin-18; D019444:Vaccines, DNA; D007371:Interferon-gamma