Cloning of cDNA for Canine Interleukin-18 and Canine Interleukin-1beta Converting Enzyme and Expression of Canine Interleukin-18

Abstract
Cloning of canine interleukin-18 (IL-18) and canine interleukin-1 beta converting enzyme (ICE) cDNA was carried out by using murine IL-18 cDNA and human ICE cDNA, respectively, as probes. Sequence homology to known sequences of human, mouse, or rat genes was noted at nucleotide and amino acid levels. Canine IL18 mRNA was expressed in various canine organs, whereas canine ICE mRNA was expressed in only a few, particularly in the brain and testis. Cloned canine IL-18 cDNA was expressed in Escherichia coli. The resulting protein promoted induction of canine interferon-gamma (IFN-gamma) from stimulated canine lymphocytes. Canine IL-18 and canine IL-12 produced canine IFN-gamma synergistically. Canine IL-18 suppressed the growth of tumor cells transplanted in SCID mice. Cloned canine IL-18 should prove useful as an anticancer agent.