Expression and purification of recombinant ovine interleukin-1 beta from Escherichia coli.

An expression vector bearing the gene segment encoding the mature form of ovine interleukin-1 beta (OvIL-1 beta) was constructed. This vector provided a rapid method for obtaining Escherichia coli derived recombinant OvIL-1 beta (rOvIL-1 beta) using the expression plasmid pGEX-2T. The level of expression of fusion protein in the soluble fraction was approximately 20% of the total accumulated proteins. Affinity purification by glutathione-Sepharose yielded a fusion protein and subsequent thrombin cleavage of this material yielded rOvIL-1 beta. The specific activity of the purified recombinant protein was 10(3)-10(4) times higher than the fusion protein. The rOvIL-1 beta was 10-100 times more potent than human interleukin-1 beta (HuIL-1 beta) in an ovine thymocyte proliferation assay, although they were of equal potency in the NOB-1/CTLL assay. This simple purification method, which produces purified rOvIL-1 beta with a high specific activity (approximately 10(8) U mg-1), will now make it possible to evaluate the in vivo effects of IL-1 beta in sheep.