Systemic and local cytokine response of young piglets to oral infection with Salmonella enterica serotype Typhimurium

Salmonella enterica serovar Typhimurium-infected pigs with different shedding levels exhibit distinct clinical, peripheral cytokine and transcriptomic immune response phenotypes

Foodborne salmonellosis costs the US $2.7 billion/year, including $100.0 million in annual losses to pork producers. Pigs colonized with Salmonella are usually asymptomatic with varied severity and duration of fecal shedding. Thus, understanding the responses that result in less shedding may provide a mechanism for control. Fifty-four pigs were inoculated with Salmonella enterica serovar Typhimurium (ST) and clinical signs, fecal ST shedding, growth performance, peripheral cytokines and whole blood gene expression were measured. Persistently shedding (PS) pigs had longer pyrexia and elevated serum IL-1β, TNF-α and IFN-γ compared with low shedding (LS) pigs, while LS pigs had brief pyrexia, less shedding that decreased more rapidly and greater serum CXCL8 than PS pigs. The PS pigs up-regulated genes involved with the STAT1, IFNB1 and IFN-γ networks on d 2, while up-regulation of genes involved in immune response regulation were only detected in LS pigs. This is the first study to examine host responses to ST infection at a clinical, performance, cytokine and transcriptomic level. The results indicated that pigs with different shedding outcomes developed distinct immune responses within the first 2 d of ST infection, and elucidated alternative mechanisms that could be targeted to reduce Salmonella shedding and spread.

NK cell-mediated cytotoxicity modulation by A(2) adenosine receptor agonist in different mammalian species

Adenosines, endogenous purine nucleosides, appear in the extracellular space under metabolically stressful conditions associated with ischemia, inflammation, and cell damage. Their activity on innate immunity is prevalently inhibitory and can develop both in infectious and neoplastic diseases. During cancer development, tumor cells that release high concentrations of adenosines can impair the function of tumor-infiltrating lymphocytes and assist tumor growth by neo-angiogenesis. We evaluated the influence of A(2) adenosine receptor (A(2)AR) agonist on cytotoxic-cell response comparing human with other mammalian species (rodents, pigs, goats), both in healthy and in cancer conditions. The A(2)AR agonist developed dose-dependent inhibition of the cytotoxic activity of immune effector cells in all studied species. However, variability of the response was observed in relation to the species and the target cells that were used. Altogether, our data indicate that the A(2)AR plays a central role in adenosine-mediated inhibition of immune response to tumors.

Correlating blood immune parameters and a CCT7 genetic variant with the shedding of Salmonella enterica serovar Typhimurium in swine

The porcine response to Salmonella infection is critical for control of Salmonella fecal shedding and the establishment of Salmonella carrier status. In this study, 40 crossbred pigs were intranasally inoculated with Salmonella enterica serovar Typhimurium (Salmonella Typhimurium) and monitored for Salmonella fecal shedding and blood immune parameters at 2, 7, 14 and 20 days post-inoculation (dpi). Using a multivariate permutation test, a positive correlation was observed between Salmonella Typhimurium shedding levels at 2 and 7dpi and serum interferon-gamma (IFNgamma) levels at 2dpi (p<0.05), with Salmonella being shed in greater numbers from animals with higher IFNgamma levels. A positive correlation was also observed between IFNgamma levels and the number of banded neutrophils (2dpi), circulating neutrophils (7 and 14dpi), monocytes (7dpi), and white blood cells (WBCs) (7, 14 and 20dpi). We have further performed association studies on these immune response parameters as well as shedding status of the Salmonella-infected pigs with a single nucleotide polymorphism (SNP) in the porcine gene CCT7, previously shown by our group to be transcriptionally up-regulated in swine experimentally inoculated with Salmonella Typhimurium. Our analyses with the 40 pigs suggest a positive association (p=0.0012) of SNP genotype A/G at position AK240296.c1153G>A of the CCT7 gene with Salmonella shedding at 7dpi compared to the G/G homozygote genotype. Linking specific genes and genetic polymorphisms with the porcine immune response to Salmonella infection and shedding may identify potential markers for carrier pigs as well as targets for disease diagnosis, intervention and prevention.

Impact of Salmonella Typhimurium DT104 virulence factors invC and sseD on the onset, clinical course, colonization patterns and immune response of porcine salmonellosis

The present study was conducted to study the impact of the virulence factors invC and sseD of the two type III secretion systems of Salmonella enterica serovar Typhimurium (S. Typhimurium) on the pathogenesis of the porcine S. Typhimurium DT104 infection. For this purpose, two S. Typhimurium mutant strains with a disrupted invC gene of the Salmonella pathogenicity island 1 or with a disrupted sseD gene of the Salmonella pathogenicity island 2 have been studied in experimental infection of pigs. Twenty-two 7-week-old male hybrid pigs were either infected with one of the mutants or the wild-type S. Typhimurium DT104 strain. Each group was examined for clinical signs, Salmonella shedding rate and the specific antibody response. Survival and replication were evaluated by qualitative and quantitative determination of the colonization rate. The humoral and cellular immune responses were examined using isotype-specific ELISA and quantitative real-time PCR of IL-2, IL-4, IL-10, IL-12 and IFN-gamma. The results proved that both mutants had a lower virulence (with marked differences between both mutants) than the wild-type and that both virulence factors have importance in porcine salmonellosis. Only pigs infected with the wild-type S. Typhimurium DT104 exhibited typical clinical symptoms of salmonellosis like anorexia, vomiting, disturbed demeanour, fever and diarrhoea. Deletion of the invC gene resulted in a significantly reduced colonization rate. Interestingly, the mRNA expression of both type-1 and type-2 cytokines were significantly decreased in pigs infected with either the invC-mutant and the sseD-mutant strain.

Bacteria and the gastrointestinal tract: beneficial and harmful effects

Bacteria are unique microorganisms that have a variety of physiological functions which are beneficial to human beings. However, bacteria can also be harmful and cause infections if translocated from the gastrointestinal tract to the epithelial tissue following surgery. The process of translocation can lead to surgical wounds becoming contaminated with gastrointestinal microbes such as Escherichia coli, Proteus or Klebsiella species. Bacteria can also cause severe gastrointestinal infections as a consequence of the ingestion of contaminated food. Food-borne bacterial infections can lead to serious consequences for the patient. Nurses managing the care of surgical patients and older people need to be aware of the physiological role that bacteria play but also the detrimental effects of bacterial translocation or ingestion particularly in older people, infants and people who are immunosuppressed.

Role of SPI-1 in the interactions of Salmonella Typhimurium with porcine macrophages

Salmonella Pathogenicity Island 1 (SPI-1) genes are indispensable for virulence of Salmonella Typhimurium in mice after oral challenge. These genes mediate invasion in intestinal epithelial cells and induce cell death in murine macrophages. The role of SPI-1 in the pathogenesis of Salmonella Typhimurium infections in food producing animals is not known. It was the aim of the present study to characterize the interactions of a porcine Salmonella Typhimurium field strain and its isogenic mutants in the SPI-1 genes hilA, sipA and sipB with porcine macrophages. SPI-1 was found to be important in the invasion of porcine pulmonary alveolar macrophages (PAM) and the induction of the formation of spacious phagosomes. Both early and delayed cytotoxicity were seen in PAM, but only the early cytotoxicity was SPI-1 dependent. Exposure of PAM to Salmonella Typhimurium induced the production of reactive oxygen species (ROS) and interleukin-8, but no differences were noticed between the induction mediated by the wild type strain and its SPI-1 mutant strains. In conclusion, invasion of porcine macrophages and the induction of early, but not delayed, cytotoxicity by Salmonella Typhimurium is SPI-1 dependent. SPI-1 dependent invasion, however, is not a prerequisite to induce a pro-inflammatory response.

Protection of gnotobiotic pigs against Salmonella enterica serotype Typhimurium by rough mutant of the same serotype is accompanied by the change of local and systemic cytokine response

We have demonstrated that severe systemic disease caused by virulent LT2 strain Salmonella enterica serotype Typhimurium in gnotobiotic piglets can be alleviated by oral inoculation with an avirulent rough (R) mutant of the same serotype 24 h before challenge with the virulent strain. Protected piglets had no signs of enteritis. The concentrations of TNF-alpha, IL-1beta, IL-8 and IL-10 were measured by ELISA in ileal washings and plasma of uninfected and infected pigs. The cytokines were not detected in plasma of germ-free piglets, and low concentrations of IL-1beta and IL-8 were found in their ileal washings. The pre-inoculation of the rough mutant induced an increase in IL-8 and decrease in IL-1beta and IL-10 in plasma. The virulent LT2 strain induced very high TNF-alpha concentrations in the ileum which were reduced in the pigs pre-inoculated with the R mutant.

Inflammatory mediator production in swine following endotoxin challenge with or without co-administration of dexamethasone

The inflammatory response in swine challenged with lipopolysaccharide (LPS) has only been partially characterized. As swine are increasingly used in biomedical research, it is important to determine if they respond to endotoxin challenge in a manner similar to other model systems. Accordingly, 24 Poland China x Landrace barrows were treated with saline, LPS, dexamethasone, or LPS and dexamethasone, with six animals in each treatment group. The kinetics of TNFalpha, IL-1beta, IL-6, IL-8, IL-10, nitric oxide (nitrate/nitrite), and neopterin production in swine plasma were examined at 1, 3, 6, 9, and 24 h after acute LPS challenge. Lipopolysaccharide increased plasma TNFalpha levels, which peaked 1 h post-challenge. Dexamethasone decreased LPS-induced TNFalpha by approximately 60%. Plasma IL-6 levels peaked 3 h post-LPS challenge, returning to basal levels by 9 h. Swine given both LPS and dexamethasone had minimal IL-6 levels. Control and dexamethasone-only treated animals never exhibited systemic TNFalpha or IL-6 levels. Lipopolysaccharide increased plasma IL-10 1 h after challenge. Dexamethasone did not alter plasma IL-10 levels in LPS-challenged swine. Interleukin-1beta was constitutively present in plasma and was not altered by any combination of treatments. Plasma IL-8 was not observed in any treatment group. Plasma nitrate/nitrite levels were maximal 24 h post-challenge. Dexamethasone treatment prevented increases in plasma nitrate/nitrite levels in LPS-treated animals. Lipopolysaccharide induced levels of neopterin; dexamethasone served to further increase plasma neopterin levels in LPS-challenged animals. The discordant regulation of inflammatory mediators suggests that the immunological responses by swine to LPS are distinct from the responses seen in rodent and human studies.