The tissue expression level of BPIgene in piglets from newborn to weaning and its relationship with Gram-negative bacterial infection

The bactericidal/permeability increasing protein (BPI) has an important function of nonspecific killing of Gram-negative bacteria. In this study, qPCR was used to detect the expression of the BPIgene in twelve tissues of Meishan piglets from birth to weaning. BPIgene overexpression, bacterial adhesions count and indirect immunofluorescence were applied to analyze the relationship between BPIgene expression and the infectivity of Escherichia coliand Salmonella.The results showed that the BPIgene was expressed highly in duodenum, jejunum and ileum (fold changes of relative expression levels were more than 10 000, 500 and 200, respectively). The expression of the BPIgene at 35 days of age was significantly higher (P<0.01) than that at all other days. Transcription of the BPIgene was up-regulated 2 401-fold in porcine intestinal epithelial (IPEC-J2) cells that were transfected with the BPIgene overexpression lentivirus (IPEC-J2-BPI), and significantly higher (P<0.01) than that in negative control cells (IPEC-J2-NC). Protein expression levels in IPEC-J2-BPI cells were also increased. When IPEC-J2 cells were incubated with E. coliand Salmonella,respectively, for 2, 4, 6, 8, 10 and 12 h, the number of bacterial adhesions in IPEC-J2-BPI cells was significantly less (P<0.05) than that in IPEC-J2-NC cells. The results of indirect immunofluorescence analysis showed that the number of bacterial adhesions in IPEC-J2-BPI cells was significantly less (P<0.01) than that in IPEC-J2-NC cells. These results demonstrated that the BPIgene might play an important role in regulating weaning stress especially intestinal-mediated immune response. Overexpression of the BPIgene at the cellular level could significantly enhance the anti-bactericidal ability against Gram-negative bacteria such as E. coliand Salmonella.This has important biological significance in piglet resistance to bacterial diarrhea.