Recently identified interferon-epsilon (IFN-epsilon) belongs to type I interferons. IFN-epsilon is highly and constitutively expressed in the brain, but its biochemical and biological characteristics are poorly understood. In this study, full-length IFN-epsilon cDNA was cloned from human peripheral blood lymphocyte by RT-PCR, and was expressed in Escherichia coli (E coli). Reverse phase high pressure liquid chromatography was used to purify recombinant human IFN-epsilon (rhIFN-epsilon) and to facilitate refolding of the protein. About 0.8 mg of highly purified rhIFN-epsilon, protein was obtained from 100 ml of E. coli culture. Functional study of rhIFN-epsilon demonstrated that the antiviral activity of rhIFN-epsilon was 6 +/- 0.5 x 10(5) IU/mg, which was lower than that of rhIFN-alpha-2b in the WISH-VSV (WISH cells infected with vesicular stomatitis virus) assay system.