Salmonella infections: immune and non-immune protection with vaccines

Intestinal cytokine response of commercial source broiler chicks to Salmonella typhimurium infection

Development of molecular-based immunotherapeutic strategies for controlling Salmonella Typhimurium (ST) infection in poultry requires a better understanding of intestinal and cecal cytokine responses. Accordingly, an experiment was conducted to measure changes in intestinal cytokine expression when commercial source broiler chickens were challenged with a nalidixic acid-resistant ST. Ross broiler chicks were nonchallenged with ST (control treatment) or challenged by orally giving 7.8 x 10(6) cfu at 4 d of age (STC treatment). Each treatment consisted of 4 replicate pens with 14 chicks per pen. Expression levels of proinflammatory cytokines, interferon-gamma, and antiinflammatory interleukin (IL)-10 were determined at 5 and 10 d postchallenge (PC). Intestinal flushes were also collected from each treatment at 7 d PC to estimate IgA and IgG. Results showed an upregulation in IL-1beta mRNA in STC chicks at 5 d PC. By 10 d PC, the expression of IL-1beta was further increased and accompanied by an upregulation of IL-6 and interferon-gamma mRNA, whereas IL-10 mRNA expression decreased. It was concluded that ST induced an intestinal mucosal inflammatory response in commercial source broiler chicks less than 2 wk of age.

Rapid detection of Salmonella dublin by PCR amplification of the SopE gene and its cloning

This study is directed towards the method of amplifying and cloning the SopE gene, that encodes Salmonella outer protein E. Strains used in this study were S. dublin collected from Kermanshah province. Genomic DNA was extracted by the general boiling method. Using the specific primers, a part of SopE gene was multiplied. The PCR product was inserted into the cloning vector (pTZ57R/T). Furthermore, E. coli DH5alpha bacteria were transformed to amplify the recombinant plasmid. Recombinant clones were identified by blue/white selection. Recombinant plasmids were purified by alkaline lysis procedure. Moreover, identity of the SopE/pTZ57R/T product was confirmed by restriction enzyme digestion assay and sequencing. Finally, the cloned gene was compared with that published by the NCBI Genbank (L78932). The results showed that the obtained sequence differed in four nucleotides which resulted in two amino acid differences. The cloned SopE was submitted to the NCBI Genbank (EU399750).

Vaccines against intracellular bacterial pathogens

There is a long history of remarkable success in developing vaccines against bacteria that are extracellular pathogens. In general, the development of vaccines against intracellular bacterial pathogens has proven to be more challenging. Typically, such vaccines need to induce a range of immune responses, including antibody, CD4(+) and CD8(+) T cell responses. These responses can be induced by live attenuated vaccines, but eliciting these responses with non-living vaccines has proven to be difficult. The difficulties appear to be related partly to the problems associated with the identification of protective antigens and partly with the difficulties associated with inducing CD8(+) T cell responses.

Salmonella induces prominent gene expression in the rat colon

Background

Salmonella enteritidis is suggested to translocate in the small intestine. In vivo it induces gene expression changes in the ileal mucosa and Peyer's patches. Stimulation of Salmonella translocation by dietary prebiotics fermented in colon suggests involvement of the colon as well. However, effects of Salmonella on colonic gene expression in vivo are largely unknown. We aimed to characterize time dependent Salmonella-induced changes of colonic mucosal gene expression in rats using whole genome microarrays. For this, rats were orally infected with Salmonella enteritidis to mimic a foodborne infection and colonic gene expression was determined at days 1, 3 and 6 post-infection (n = 8 rats per time-point). As fructo-oligosaccharides (FOS) affect colonic physiology, we analyzed colonic mucosal gene expression of FOS-fed versus cellulose-fed rats infected with Salmonella in a separate experiment. Colonic mucosal samples were isolated at day 2 post-infection.

Results

Salmonella affected transport (e.g. Chloride channel calcium activated 6, H⁺/K⁺ transporting Atp-ase), antimicrobial defense (e.g. Lipopolysaccharide binding protein, Defensin 5 and phospholipase A2), inflammation (e.g. calprotectin), oxidative stress related genes (e.g. Dual oxidase 2 and Glutathione peroxidase 2) and Proteolysis (e.g. Ubiquitin D and Proteosome subunit beta type 9). Furthermore, Salmonella translocation increased serum IFNγ and many interferon-related genes in colonic mucosa. The gene most strongly induced by Salmonella infection was Pancreatitis Associated Protein (Pap), showing >100-fold induction at day 6 after oral infection. Results were confirmed by Q-PCR in individual rats. Stimulation of Salmonella translocation by dietary FOS was accompanied by enhancement of the Salmonella-induced mucosal processes, not by induction of other processes.

Conclusion

We conclude that the colon is a target tissue for Salmonella, considering the abundant changes in mucosal gene expression.