Immune response to liposome-associated recombinant SEF21 following oral immunization in chickens

Everything You Always Wanted to Know About Salmonella Type 1 Fimbriae, but Were Afraid to Ask

Initial attachment to host intestinal mucosa after oral infection is one of the most important stages during bacterial pathogenesis. Adhesive structures, widely present on the bacterial surface, are mainly responsible for the first contact with host cells and of host-pathogen interactions. Among dozens of different bacterial adhesins, type 1 fimbriae (T1F) are one of the most common adhesive organelles in the members of the Enterobacteriaceae family, including Salmonella spp., and are important virulence factors. Those long, thin structures, composed mainly of FimA proteins, are responsible for recognizing and binding high-mannose oligosaccharides, which are carried by various glycoproteins and expressed at the host cell surface, via FimH adhesin, which is presented at the top of T1F. In this review, we discuss investigations into the functions of T1F, from the earliest work published in 1958 to operon organization, organelle structure, T1F biogenesis, and the various functions of T1F in Salmonella-host interactions. We give special attention to regulation of T1F expression and their role in binding of Salmonella to cells, cell lines, organ explants, and other surfaces with emphasis on biofilm formation and discuss T1F role as virulence factors based on work using animal models. We also discuss the importance of allelic variation in fimH to Salmonella pathogenesis, as well as role of FimH in Salmonella host specificity.

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.