Cloning and expression of the gene coding for IL-2(60)-PE40, a molecular targeted protein.

It has recently been shown that chimeric toxin composed of IL2 fused tp PE40, a mutant form of Pseudomonas Exotoxin A devoid of its native cell recognition and binding domain was cytotoxic to IL2 receptor bearing cells. We here amplified the gene IL-2 (60), which codes for the N-terminal 1-60 amino acids of human IL-2 by PCR. After that, we fused it to PE40 and the new chimeric protein IL-2(60)-PE40 was expressed in E. coli. SDS-PAGE revealed that IL-2(60)-PE40 chimeric protein accounts for more than 18% of total cell proteins. As the region IL-2 binds with its receptor was defined in the N-terminal residues 8-54 of IL-2, such fusion proteins will have the same activity with IL-2-PE40. Following primary purification, IL-2(60)-PE40 was shown to be very toxic to IL-2 receptor-positive cells but non measurable effect on the cells lacking IL-2 receptors. Such a structure has not been reported by now. The fusion protein is useful for suppressing the immune response in cases of rejection of allografts and organ transplants and as therapeutic agents for the treatment of IL-2 receptor related diseases such as autoimmune disease, ATL (adult T-cell leukemia), et al.