The increased availability and identification of genes from human and other genomes has led to an increased need for efficient expression and purification of recombinant proteins. The expression of proteins in bacteria is by far the most widely used approach for the production of cloned genes. For many reasons, expression in bacteria is preferred to expression in eukaryotic cells. For example, bacteria are much easier to grow than eukaryotic cells. More specifically, the availability of a wealth of sophisticated molecular genetic tools and thousands of mutants make E. coli, as an expression host, extremely useful for protein production. However, the high-level production of functional proteins in E. coli., especially those from eukaryotic sources has often been difficult.
IL-28A, IL-28B, and IL-29 comprise a recently discovered new family of proteins that have sequence homology to type I interferons and genomic homology to IL-10. This new family is fully described in co-owned PCT application WO 02/086087 and Sheppard et al., Nature Immunol. 4:63-68, 2003. Functionally, IL-28A, IL-28B and IL-29 resemble type I INFs in their ability to induce an antiviral state in cells but, unlike type I IFNs, they do not display antiproliferative activity against certain B cell lines.
Recombinant IL-29 has been produced in prokaryotic cells, in particular E. coli. The resulting bacterial produced protein is not glycosylated, and is produced in an aggregated state. Production of IL-29 from E. coli requires that the aggregated proteins be solubilized from the insoluble inclusion bodies and renatured or refolded. Without renaturation, the specific activity of the recombinant protein will be significantly reduced.
Despite advances in the expression of recombinant proteins in bacterial hosts, there exists a need for improved methods for producing biologically active and purified recombinant IL-29 proteins in prokaryotic systems which result in higher yields for protein production. These and other aspects of the invention will become evident upon reference to the following detailed description.