Cloning and expression of the canine interferon-beta gene

We isolated the canine interferon-beta (IFN-beta) gene from dog liver chromosomal DNA by the polymerase chain reaction (PCR). The coding region encodes a predicted protein of 197 amino acids, consisting of a signal sequence of 32 amino acids and a mature IFN-beta of 165 amino acids. In the IFN-beta sequence, there are five potential N-glycosylation sites and four cysteine residues. Canine IFN-beta has 44% and 60% amino acid sequence homology with murine and human IFN-beta, respectively, whereas it has only 28% homology with canine IFN-alpha. The canine IFN-beta gene was expressed in insect cells under the control of the polyhedrin promoter in a recombinant baculovirus. After infecting Sf21 cells with the recombinant baculovirus, IFN activity was detected in the culture medium, indicating that it is secreted from the cells. This activity was stable from pH 2 to 12 for 18 h at 4 degrees C. Southern blot analysis indicated that the gene for canine IFN-beta is a single gene in the dog haploid chromosome.