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Abstract
Recombinant human consensus interferon-alpha (cIFN-α) was obtained by synthesizing a codon-optimized gene composed of the consensus nucleotides at each position in the human alpha interferon family and expressing it in Escherichia coli. The full cIFN-α gene was synthesized in two steps of assembly and amplification by polymerase chain reaction (PCR) using long (45–50 nucleotides) overlapped primers. The two-step PCR resulted in a DNA band of 504 base pairs (bp) corresponding to the calculated size of the cIFN-α gene. The synthetic gene was cloned into temperature-regulated Power3 expression vector. The ligated Power3-cIFN-α (Power3-cIFNα) plasmid carried the cIFN-α gene under transcriptional regulation of the heat-inducible λPL promoter. This expression system was optimized with respect to heat-shock temperature and time of induction in shake flask cultures. The produced cIFN-α protein was characterized by polyacrylamide gel electrophoresis and immunoassays. The majority of the expressed cIFN-α protein of about 19 kD in size accumulated in the form of inclusion bodies. After refolding and purification utilizing single-step ion-exchange chromatography on DEAE-Sepharose, the yield was 70 mg/L. cIFN-α anti-cancer activity was assayed and compared with the commercially available IFN-α2a.
ACKNOWLEDGMENT
This study was funded by Science and Technology Development Fund STDF-ID269 for E.M.R.
Notes
a Monoclonal anti-human IFN-α antibody reacted significantly (p < 0.05) with expressed cIFN-α.
a Majority of the produced protein has aggregated in inclusion bodies (about 47% of the yield in total cell lysate).
a There is a significant difference (p < 0.05) in ELISA signals between the whole cell-lysate pellet containing cIFN-α and the purified fractions 13, 14, and 15.