Secreted expression of the combinant antimicrobial peptide PL in Pichia pastoris and its antibacterial activity in vitro / 生物工程学报

In order to obtain a high activity antibacterial peptide, An expression vector pPICZalphaA-pl is constructed with a tandem of four antimicrobial peptides in the same direction,which includes Protegrin-1 (PG-1), Scorpion Defensin (SD), Metalnikowin-2A and Sheep Myeloid Antibacterial Peptide (SMAP-29) (serial number in GenBank are AAB27599, AAAB27538, P80409 and P49928 respectively). At the same time the expression vector pPICZalphaA-sd which express Scorpion Defensin was contructed. The expression vectors of pPICZalphaA-pl and pPICZalphaA-sd were linearized and transformed into the yeast host strain X-33 respectively. Under the control of the promoter AOX1 (alcohol oxidase1), the peptides PL and SD were secreted expressed. Their heat-stable property, acid-stable property and MIC were detected in vitro. The results suggest the peptides PL and SD have good heat-stable and acid-stable properties, and the combinant PL peptide showes higher antibacterial activity against several Gram-positive bacteria (G+) and Gram-negative bacteria (G-) than the peptide SD, especially against Escherichia coli. The antibacterial activity of combinant antimicrobial peptide PL shows its far exploiting perspective.

Influence of epitope A modification and N-linked glycosylated site mutation of PRRSV NJ-a strain ORF5 gene on the ability to induce neutralizing antibodies and T cell proliferation response / 生物工程学报

To enhance the DNA immunogencity of PRRSV ORF5 gene, CpG sequence and the universal helper T cell antigen epitope (PADRE) sequence were inserted between the decoy epitope and the neutralizing epitope. At the same time, site-mutations were introduced at N33 and N51 to diminish the coverage effect to epitope B from the polysaccharides. Subsequently, the modified ORF5 gene (MORF5) and PRRSV ORF6 gene were cloned into the eukaryotic expression vector pcDNA3.0 under the control of two CMV promoters, respectively. With indirect immunofluorescence assay and Western-blot the expression in vitro of the two genes was confirmed, then six-week-old Balb/C mouse were immunized with the modified expression plasmid pcDNA-M5A-6A. The non-modified expression plasmid pcDNA-5A-6A, the blank eukaryotic expression plasmid pcDNA3.0, living attenuated vaccine and inactivated vaccine were used as controls. The PRRSV specific neutralizing antibodies and the T cell proliferation response were elevated with virus neutralization assay and MTf method. Results indicate that the modified plasmid pcDNA-M5A-6A can elicit not only higher titer of neutralizing antibodies in a rapid time, but also more vigorous T cell proliferation response compared with the non-modified plasmid pcDNA-5A-6A and commercial vaccines, indicating that DNA vaccine pcDNA-M5A-6A maybe a promising candidate for PRRS prevention.