Identification of BPI protein produced in different expression system and its association with Escherichia coli F18 susceptibility

The super antibiotic bactericidal/permeability-increasing (BPI) protein is a member of a new generation of proteins that have been implicated as endotoxin-neutralizing agents. In this study, recombinant porcine BPI protein was obtained by generating porcine BPI encoding prokaryotic, eukaryotic, and yeast expression vectors. Recombinant protein expression was detected in yeast GS115, Escherichia coli, and 293-6E cells by gel electrophoresis and Western blotting. Escherichia coli F18 is the primary Gram-negative bacteria in the gut and the main pathogen leading to diarrhea and edema disease in weaning piglets. Therefore, Escherichia coli F18-resistant and -sensitive Sutai piglets were used to test differential expression of BPI protein by Western blotting and to investigate the potential correlation between BPI protein expression and Escherichia coli F18-susceptibility. Recombinant porcine BPI protein expression was not detected in the prokaryotic and yeast expression systems; however, soluble protein was detected in the eukaryotic expression system. These data indicate the strong bacteriostatic action of the BPI protein and confirm the feasibility of obtaining large amounts of recombinant porcine BPI recombinant protein using this eukaryotic expression system. In addition, the BPI protein expression levels in the Escherichia coli F18-resistant group were significantly higher than those in the sensitive group, indicating that high BPI protein expression is associated with resistance to Escherichia coli F18. Our findings provide a basis for further investigations into the development of a drug designed to confer resistance to Escherichia coli F18 in weaning piglets.