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 BPI gene in twelve tissues of Meishan piglets from birth to weaning. BPI gene overexpression, bacterial adhesions count and indirect immunofluorescence were applied to analyze the relationship between BPI gene expression and the infectivity of Escherichia coli and Salmonella. The results showed that the BPI gene 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 BPI gene at 35 days of age was significantly higher (P<0.01) than that at all other days. Transcription of the BPI gene was up-regulated 2 401-fold in porcine intestinal epithelial (IPEC-J2) cells that were transfected with the BPI gene 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. coli and 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 BPI gene might play an important role in regulating weaning stress especially intestinal-mediated immune response. Overexpression of the BPI gene at the cellular level could significantly enhance the anti-bactericidal ability against Gram-negative bacteria such as E. coli and Salmonella. This has important biological significance in piglet resistance to bacterial diarrhea.

杀菌/通透性增加蛋白（BPI）具有非特异性杀死革兰氏阴性细菌的重要功能。在这项研究中，qPCR用于检测BPI基因在梅山仔猪从出生到断奶的十二个组织中的表达。应用BPI基因过表达，细菌粘附计数和间接免疫荧光分析BPI基因表达与大肠埃希菌和沙门氏菌感染性之间的关系。结果表明，BPI基因在十二指肠，空肠和回肠中高表达（相对表达水平的倍数变化分别超过10000、500和200）。BPI的表达35日龄时该基因显着高于其他所有日龄（P <0.01）。在用BPI基因过表达慢病毒（IPEC-J2-BPI）转染的猪肠上皮（IPEC-J2）细胞中，BPI基因的转录上调了2 401倍，并且显着高于（P <0.01）在阴性对照细胞（IPEC-J2-NC）中。IPEC-J2-BPI细胞中的蛋白质表达水平也增加了。当IPEC-J2细胞分别与大肠杆菌和沙门氏菌孵育2、4、6、8、10和12 h时，IPEC-J2-BPI细胞中的细菌粘附数量显着减少（P<0.05）高于IPEC-J2-NC细胞。间接免疫荧光分析的结果表明，IPEC-J2-BPI细胞的细菌粘附数量明显少于IPEC-J2-NC细胞（P <0.01）。这些结果表明，BPI基因可能在调节断奶应激特别是肠介导的免疫反应中起重要作用。BPI基因在细胞水平上的过表达可以显着增强针对革兰氏阴性细菌（如大肠杆菌和沙门氏菌）的抗菌能力。这对仔猪抵抗细菌性腹泻具有重要的生物学意义。