Expression and purification of canine granulocyte colony-stimulating factor (cG-CSF)

Canine granulocyte colony-stimulating factor (cG-CSF) with modification of cysteine at position 17 to serine was expressed in Brevibacillus choshinensis HPD31. cG-CSF secreted into the culture medium was purified by ammonium sulfate precipitation and consecutive column chromatography, using butyl sepharose and DEAE sepharose. Biological activity of the recombinant cG-CSF was 8.0 × 10⁶ U/mg protein, as determined by its stimulatory effect on NFS-60 cell proliferation. Purified cG-CSF was subcutaneously administered once a day for two successive days to dogs (1, 5, 25, or 125 μg). Neutrophil count increased the following day in all dogs except those administered the lowest dose (1 μg). No severe side effects were observed in dogs after administration of cG-CSF.