Production of recombinant porcine interferon alpha using PHB-intein-mediated protein purification strategy

Interferons (IFNs) are involved in the pathogenesis and recovery of viral and other infectious diseases. Recombinant IFNs have been used as anti-infectious agents exhibiting a broad range of antiviral and immunomodulatory properties in both human and domestic animals. In this report, we describe a highly efficient and economical approach to purify porcine IFN alpha (PoIFNα) using polyhydroxybutyrate (PHB) as the affinity carrier and intein for self-cleaving removal of the affinity tag. Additionally, the conditions of protein expression and purification have been optimized. Our results suggested that culture medium containing 1.62% (w/v) of sodium lactate dramatically increases the accumulation of PHB binding protein in Escherichia coli cells. High yields of recombinant PoIFNα (30-35 mg/L, 97% purity by high-performance liquid chromatography) were obtained using intein-mediated self-cleaving conditions using a cleavage-inducing buffer with a pH of 6.5 at 20 °C for 24-36 h. The antiviral activity of the recovered recombinant PoIFNα was up to 1.4 x 10⁶ IU/mg of protein ascertained using recombinant human IFNα1 as a standard. This report also demonstrates that large-scale production of intein-mediated purification of highly pure and active recombinant PoIFNα is feasible for the purposes of experimental studies, veterinary clinic therapeutics, and swine infectious disease control.