Reduction of Salmonella Enteritidis Number After Infections by Immunization of Liposome-Associated Recombinant SefA

In order to generate Salmonella enterica serovar Enteritidis (Salmonella Enteritidis) fimbriae, SEF14, the sefA gene, which encodes the main subunit of the SEF14 fimbrial protein, was amplified from Salmonella Enteritidis by polymerase chain reaction (PCR) and subcloned into a prokaryotic expression vector pET-28a(+) to yield pET-28a(+)-sefA. The recombinant SefA (rSefA) protein was highly expressed and purified by nickel-affinity chromatography. Liposome-associated rSefA was prepared for oral immunization to seek protective efficacy for intestinal infection with Salmonella Enteritidis. The titers of the IgG and IgA in the intestinal mucus were 1:256 and 1:512, respectively. Moreover, the titers of IgG and IgA in the sera were 1:256 and 1:128, respectively. Two weeks after the booster immunization, the chickens were challenged orally with 2 x 10(6) colony-forming units (CFUs) of live Salmonella Enteritidis, and fecal samples were examined for bacterial excretion from the intestinal tract. Significantly less fecal excretion of bacteria was observed in immunized chickens for 4 wk after challenge. The numbers of bacteria in the intestinal contents (cecum and rectum) were also significantly reduced in immunized chickens, in contrast with the unimmunized controls. Oral immunization with liposome-associated rSefA therefore elicits both systemic and mucosal antibody responses and results in reduced bacterial colonization in the intestinal tract and reduced excretion of Salmonella Enteritidis in the feces.