Gene Modification and Expression of Porcine Interferon Beta and Its Antiviral Activity against Porcine Reproductive and Respiratory Syndrome Virus

Based on the sequences of porcine interferon-β gene and the mature gene(mPoIFNβ) available in GenBank,the gene encoding porcine interferon-β was modified for adapting codons of Pichia pastori and a recombinant vector pPICZαC-PoIFNβ was developed,while maintaining the same protein sequence of porcine interferon-β.The plasmid pPICZαC-PoIFNβ was linearized with SacⅠ and electroporated into Pichia pastoris X-33.The recombinant colonies were selected in high resistance culture of YPDS+Zeocin and identified by PCR.Induced by menthanol,a few positive clones were obtained secretory highly expressed the PoIFNβ protein with a protein concentration of 127.9 mg/L.The expressed supernatant was identified by SDS-PAGE and Western blotting.On the gel and membrane there were two major protein bands with molecular weight about 25 and 28 ku and they showed positive reaction with anti-PoIFNβ antibody.The CPE suppression by PoIFNβ was tested for vesicular stomatitis virus(VSV) in BHK-21 cell line and the porcine reproductive and respiratory syndrome virus(PRRSV) in Marc-145 cell line.The antiviral activity of the expressed PoIFNβ on BHK-21 cell line challenged with VSV was 2.8×103 IU/mL,and 1.6×103 IU/mL on the Marc-145 cell line challenged with PRRSV.