Cytokines in host defense against Salmonella

Immunostimulatory effects of recombinant Erysipelothrix rhusiopathiae expressing porcine interleukin-18 in mice and pigs

Interleukin-18 (IL-18), which was originally called gamma interferon (IFN-γ)-inducing factor, has been shown to play an important role in innate and acquired immune responses. In this study, attenuated Erysipelothrix rhusiopathiae strains were engineered to produce porcine IL-18 (poIL-18) and evaluated for their potential immunostimulatory effect in animals. Recombinant poIL-18 was successfully expressed in the recombinant E. rhusiopathiae strains YS-1/IL-18 and KO/IL-18. The culture supernatant of YS-1/IL-18 was confirmed to induce IFN-γ production in murine splenocytes in vitro, and this production was inhibited by incubation with anti-poIL-18 monoclonal antibodies. Furthermore, more IFN-γ production was induced upon stimulation of splenocytes with concanavalin A for splenocytes from mice that were intraperitoneally inoculated with YS-1/IL-18 than for splenocytes from control mice inoculated with the parent strain YS-1. Peritoneal macrophages from mice preinoculated with YS-1/IL-18 exhibited enhanced phagocytosis of Salmonella enterica subsp. enterica serovar Typhimurium compared with peritoneal macrophages from control mice preinoculated with YS-1. We also confirmed the immunostimulatory effect on humoral immune responses against antigens of E. rhusiopathiae and Mycoplasma hyopneumoniae in gnotobiotic pigs that were orally preinoculated with KO/IL-18. Thus, these results provide evidence that E. rhusiopathiae is a promising vector for the expression of host cytokines and suggest the potential utility of E. rhusiopathiae vector-encoded cytokines in the activation of host innate and acquired immune responses.

IFNγ expression by an attenuated strain of Salmonella enterica serovar Typhimurium improves vaccine efficacy in susceptible TLR4-defective C3H/HeJ mice

C3H/HeJ mice carry a mutated allele of TLR4 gene (TLR4 ( d )) and thus are hyporesponsive to the lethal effects of lipopolysaccharide (LPS). Characteristically, however, the mice are also hypersusceptible to infections, particularly by Gram-negative bacteria such as Salmonella enterica serovar Typhimurium (S. typhimurium) and are known to be difficult to vaccinate against virulent exposure. This is observed despite the expression of wild-type allele of Nramp1 gene, another important determinant of Salmonella susceptibility. In contrast, C3H/HeN mice (TLR4 ( n ) Nramp1 ( n )) express a functional TLR4 protein and are resistant to infection, even by virulent strains of S. typhimurium. In the present study, we describe the immune system-enhancing properties of an attenuated strain of S. typhimurium engineered to express murine IFN-γ. This strain (designated GIDIFN) was able to modulate immune responses following systemic inoculation by upregulating the production of inflammatory mediators (IL-6 and IL-12) and anti-bacterial effector molecules (nitric oxide; NO). Consequently, this led to a more effective control of bacterial proliferation in systemic target organs in both C3H/HeJ and C3H/HeN mice. Although evidence for the enhancement in immune responses could be observed as early as few hours post-inoculation, sustained improvements required 2-3 days to manifest. Vaccination of C3H/HeJ mice with GIDIFN strain, even at low doses, conferred a significantly higher degree of protection against challenge with virulent Salmonella in susceptible C3H/HeJ mice. Our data demonstrate that IFNγ-expressing Salmonella are immunogenic and confer excellent protection against virulent challenge in susceptible C3H/HeJ mice; in addition they may be used as an effective mucosal delivery vectors against virulent infection and for boosting immune responses in immunodeficient hosts.

NKRP1A+ γδ and αβ T cells are preferentially induced in patients with Salmonella infection

NKRP1A(+) γδ and αβ T cells play an important role at the early phase of Salmonella infection in mice. Meanwhile, association between NKRP1A(+) T cells and human Salmonella infection has not been reported. The objective of this study was to investigate the role of the peripheral NKRP1A(+) T cells in immune response to Salmonella infection. Expression of NKRP1A in peripheral γδ and αβ T cells and production of interferon (IFN) γ and interleukin (IL)-4 in NKRP1A(+) γδ and αβ T cells were analyzed in 28 patients with acute phase Salmonella infection, 23 patients with acute bacterial enterocolitis other than Salmonella infection (disease controls) and 44 normal controls by flow cytometry. The proportion of γδ T cells expressing NKRP1A and that of IFNγ-producing cells in NKRP1A(+) γδ cells were significantly higher in Salmonella group than those in other two groups. Compared with normal controls, the proportion of αβ T cells expressing NKRP1A and that of IL-4-producing cells in NKRP1A(+) αβ cells were significantly higher in Salmonella group. These data suggested that NKRP1A(+) T cells might play an important role in the early defense mechanism against Salmonella infection.

Early immune dynamics following infection with Salmonella enterica serovars Enteritidis, Infantis, Pullorum and Gallinarum: cytokine and chemokine gene expression profile and cellular changes of chicken cecal tonsils

Salmonella enterica subspecies enterica infection remains a serious problem in a wide range of animals and in man. Poultry-derived food is the main source of human infection with the non-host-adapted serovars while fowl typhoid and pullorum disease are important diseases of poultry. We have assessed cecal colonization and immune responses of newly hatched and older chickens to Salmonella serotypes Enteritidis, Infantis, Gallinarum and Pullorum. S. Enteritidis and S. Infantis colonized the ceca more efficiently than S. Gallinarum and S. Pullorum. Salmonella infection was also associated with increased staining for B-lymphocytes and macrophages in the cecal tonsils of infected birds. S. Enteritidis infection in newly hatched birds stimulated the expression of CXCLi1 and CXCLi2 chemokines in the cecal tonsils, while S. Gallinarum up-regulated the expression of LITAF. In older chickens, S. Enteritidis infection resulted in a significantly higher expression of CXCLi2, iNOS, LITAF and IL-10 while S. Pullorum appeared to down-regulate CXCLi1 expression in the cecal tonsils. Data from spleens showed either no expression or down-regulation of the tested genes.

Molecular and cellular characterization of a Salmonella enterica serovar Paratyphi a outbreak strain and the human immune response to infection

Enteric fever is an invasive life-threatening systemic disease caused by the Salmonella enterica human-adapted serovars Typhi and Paratyphi. Increasing incidence of infections with Salmonella enterica serovar Paratyphi A and the spreading of its antibiotic-resistant derivates pose a significant health concern in some areas of the world. Herein, we describe a molecular and phenotypic characterization of an S. Paratyphi A strain accounted for a recent paratyphoid outbreak in Nepal that affected at least 37 travelers. Pulsed-field gel electrophoresis analysis of the outbreak isolates revealed one genetic clone (pulsotype), confirming a single infecting source. Genetic profiling of the outbreak strain demonstrated the contribution of specific bacteriophages as a prime source of genetic diversity among clinical isolates of S. Paratyphi A. Phenotypic characterization in comparison with the S. Paratyphi A ATCC 9150 reference sequenced strain showed differences in flagellar morphology and increased abilities of the outbreak strain with respect to its motility, invasion into nonphagocytic cells, intracellular multiplication, survival within macrophages, and higher induction of interleukin-8 (IL-8) secreted by host cells. Collectively, these differences suggest an enhanced virulence potential of this strain and demonstrate an interesting phenotypic variation among S. Paratyphi A isolates. In vivo profiling of 16 inflammatory cytokines in patients infected with the outbreak strain revealed a common profile of a remarkable gamma interferon (IFN-γ) induction together with elevated concentrations of tumor necrosis factor alpha (TNF-α), IL-6, IL-8, IL-10, and IL-15, but not IL-12, which was previously demonstrated as elevated in nontyphoidal Salmonella infections. This apparent profile implies a distinct immune response to paratyphoid infections.

β-Galactomannan and Saccharomyces cerevisiae var. boulardii modulate the immune response against Salmonella enterica serovar Typhimurium in porcine intestinal epithelial and dendritic cells

Salmonella enterica serovar Typhimurium is a facultative intracellular pathogen that causes inflammation, necrosis, and diarrhea in pigs, as well as being an important source of food-borne diseases in humans. Probiotics and prebiotics are promising alternatives to antibiotics to control and prevent intestinal infections. The present work investigated a recently developed β-galactomannan (βGM) prebiotic compared to the proven probiotic Saccharomyces cerevisiae var. boulardii on porcine ileum intestinal epithelial cells (IECs) of the IPI-2I line and monocyte-derived dendritic cells (DCs) cocultured in vitro with Salmonella. We observed that both S. cerevisiae var. boulardii and βGM inhibited the association of Salmonella with IECs in vitro. Our data indicated that βGM has a higher ability than S. cerevisiae var. boulardii to inhibit Salmonella-induced proinflammatory mRNA (cytokines tumor necrosis factor alpha [TNF-α], interleukin-1α [IL-1α], IL-6, and granulocyte-macrophage colony-stimulating factor [GM-CSF] and chemokines CCL2, CCL20, and CXCL8) and at protein levels (IL-6 and CXCL8). Additionally, βGM and S. cerevisiae var. boulardii induced some effects on DCs that were not observed on IECs: βGM and S. cerevisiae var. boulardii showed slight upregulation of mRNA for TNF-α, GM-CSF, and CCR7 receptor on porcine monocyte-derived dendritic cells (DCs). Indeed, the addition of βGM or S. cerevisiae var. boulardii on DCs cocultured with Salmonella showed higher gene expression (mRNA) for TNF-α, GM-CSF, and CXCL8 compared to that of the control with Salmonella. In conclusion, the addition of βGM inhibits Salmonella-induced proinflammatory profiles in IECs but may promote DC activation, although associated molecular mechanisms remain to be elucidated.

Immunization of chickens with Salmonella enterica subspecies enterica serovar Enteritidis pathogenicity island-2 proteins

Several structural components of the type III secretion systems (T3SS) encoded by Salmonella pathogenicity island (SPI)-1 and SPI-2 are exposed to the host's immune system prior to/during the infection/invasion process, making them potential vaccine candidates. In this study we evaluated whether chickens vaccinated with SPI-2 T3SS components could mount a significant humoral immune response (as measured by serum IgG titres) and whether these antibodies could be transferred to progeny (as measured by egg yolk IgG titres), and whether vaccinates and progeny of vaccinates could be protected against challenge with SE. The results of our studies show that vaccinated chickens do produce high levels of SPI-2 T3SS specific serum IgG that they are able to transfer to their progeny. It was demonstrated that vaccinates and progeny of vaccinates had lower overall countable recovered Salmonella enterica subspecies enterica serovar Enteritidis (SE) per bird in most situations.

Mouse models to assess the efficacy of non-typhoidal Salmonella vaccines: revisiting the role of host innate susceptibility and routes of challenge

Non-typhoidal Salmonella enterica (NTS) serovars Typhimurium and Enteritidis are important causes of bacterial gastroenteritis in the USA and worldwide. In sub-Saharan Africa these two serovars are emerging as agents associated with lethal invasive disease (e.g., bacteremia, meningitis). The development of NTS vaccines, based on mucosally administered live attenuated strains and parenteral non-living antigens, could diminish the NTS disease burden globally. Mouse models of S. Typhimurium and S. Enteritidis invasive disease can accelerate the development of NTS vaccines. Live attenuated NTS vaccines elicit both cellular and humoral immunity in mice and their efficacy is well established. In contrast, non-living vaccines that primarily elicit humoral immunity have demonstrated variable efficacy. An analysis of the reported studies with non-living vaccines against S. Typhimurium and S. Enteritidis reveals that efficacy is influenced by two important independent variables: (1) the innate susceptibility to NTS infection that differs dramatically between commonly used mouse strains and (2) the virulence of the NTS strain used for challenge. Protection by non-living vaccines has generally been seen only in host-pathogen interactions where a sub-lethal infection results, such as challenging resistant mice with either highly virulent or weakly virulent strains or susceptible mice with weakly virulent strains. The immunologic basis of this discrepancy and the implications for human NTS vaccine development are reviewed herein.

Salmonella and Caspase-1: A complex Interplay of Detection and Evasion

Salmonellae are intracellular pathogens that replicate within epithelial cells and macrophages, and are a significant public health threat in both developed and developing countries. The innate immune system detects microbes through pattern recognition receptors, which are compartmentalized on the subcellular level to detect either extracellular (e.g., TLRs) or cytosolic (e.g., NLRs) perturbations. Salmonella infection is detected by the NLRC4 and NLRP3 inflammasomes, which activate Caspase-1, resulting in reduced bacterial burdens during infection. NLRC4 responds to the SPI1 type III secretion system via detection of inadvertently translocated flagellin and rod protein. The signals for NLRP3 detection during Salmonella infection remain undefined. Salmonella have evolved evasion strategies to attenuate Caspase-1 responses. We review recent findings describing the interplay between detection and evasion of S. typhimurium infection by the inflammasome. We discuss how the interplay between detection and evasion affects Caspase-1 effector functions mediated by IL-1β secretion, IL-18 secretion, and pyroptosis.

Interleukin-17A is required to suppress invasion of Salmonella enterica serovar Typhimurium to enteric mucosa

Salmonella enterica serovar Typhimurium (S. typhimurium) causes a localized enteric infection and its elimination is dependent on a T helper type 1 immune response. However, the mechanism of the protective immune response against the pathogen in gut-associated lymphoid tissue (GALT) at an early stage of the infection is not yet clarified. Here, we show that interleukin-17A (IL-17A) was constitutively expressed in GALT; it was also detected on crypt and epithelial cells of the small intestine. Neutralization of the IL-17A in the intestinal lumen exacerbated epithelial damage induced by intestinal S. typhimurium infection at an early stage of the infection. The result suggests that IL-17A has a pivotal role in the immediate early stage of protection against bacterial infection at the intestinal mucosa. As IL-17A neutralization also suppressed the constitutive localization of β-defensin 3 (BD3), an IL-17A-induced antimicrobial peptide, at the apical site of the intestinal mucosa, it is estimated that IL-17A constitutively induces the expression of the antimicrobial peptide to kill invading pathogens at the epithelial surface immediately after the infection. In contrast, interferon-γ is induced around 3 days after S. typhimurium infection, and its expression level increases thereafter. Taken together, the findings lead to the hypothesis that IL-17A participates in the immediate early stage of protection against S. typhimurium intestinal infection whereas interferon-γ is important at a later stage of the infection.

Oral treatment with Saccharomyces cerevisiae strain UFMG 905 modulates immune responses and interferes with signal pathways involved in the activation of inflammation in a murine model of typhoid fever

Salmonella spp. are Gram-negative, facultative, intracellular pathogens that cause several diarrheal diseases ranging from self-limiting gastroenteritis to typhoid fever. Previous results from our laboratory showed that Saccharomyces cerevisiae strain UFMG 905 isolated from 'cachaça' production presented probiotic properties due to its ability to protect against experimental infection with Salmonella enterica serovar Typhimurium. In this study, the effects of oral treatment with S. cerevisiae 905 were evaluated at the immunological level in a murine model of typhoid fever. Treatment with S. cerevisiae 905 inhibited weight loss and increased survival rate after Salmonella challenge. Immunological data demonstrated that S. cerevisiae 905 decreased levels of proinflammatory cytokines and modulated the activation of mitogen-activated protein kinases (p38 and JNK, but not ERK1/2), NF-κB and AP-1, signaling pathways which are involved in the transcriptional activation of proinflammatory mediators. Experiments in germ-free mice revealed that probiotic effects were due, at least in part, to the binding of Salmonella to the yeast. In conclusion, S. cerevisiae 905 acts as a potential new biotherapy against S. Typhimurium infection due to its ability to bind bacteria and modulate signaling pathways involved in the activation of inflammation in a murine model of typhoid fever.

Organotypic 3D cell culture models: using the rotating wall vessel to study host-pathogen interactions

Appropriately simulating the three-dimensional (3D) environment in which tissues normally develop and function is crucial for engineering in vitro models that can be used for the meaningful dissection of host-pathogen interactions. This Review highlights how the rotating wall vessel bioreactor has been used to establish 3D hierarchical models that range in complexity from a single cell type to multicellular co-culture models that recapitulate the 3D architecture of tissues observed in vivo. The application of these models to the study of infectious diseases is discussed.

Role of innate immunity in Helicobacter pylori-induced gastric malignancy

Helicobacter pylori colonizes the majority of persons worldwide, and the ensuing gastric inflammatory response is the strongest singular risk factor for peptic ulceration and gastric cancer. However, only a fraction of colonized individuals ever develop clinically significant outcomes. Disease risk is combinatorial and can be modified by bacterial factors, host responses, and/or specific interactions between host and microbe. Several H. pylori constituents that are required for colonization or virulence have been identified, and their ability to manipulate the host innate immune response will be the focus of this review. Identification of bacterial and host mediators that augment disease risk has profound ramifications for both biomedical researchers and clinicians as such findings will not only provide mechanistic insights into inflammatory carcinogenesis but may also serve to identify high-risk populations of H. pylori-infected individuals who can then be targeted for therapeutic intervention.

Salmonella enterica serovar Typhimurium ruvB mutant can confer protection against salmonellosis in mice

Salmonella enterica is an important pathogen that causes a variety of infectious diseases in animals and humans. Live attenuated vaccines generally confer better protection than killed or subunit vaccines; however, the former are limited by their inherent toxicity. We evaluated the potential of a novel candidate Salmonella vaccine strain that lacks the ruvB gene. The ruvB gene encodes a Holliday junction helicase that is required to resolve junctions that arise during the repair of non-arresting lesions after DNA replication. The deletion of this gene in Salmonella significantly impaired cell survival and proliferation within epithelial cells and macrophages. The defective virulence in ruvB mutant may be partially due to decreased expression of ssaG, a Salmonella pathogenicity island-2 gene, and increased sensitivity to hydrogen peroxide in the lack of ruvB gene. The virulence of the ruvB-deleted mutant was also greatly attenuated in BALB/c mice. The ruvB mutant conferred strong and durable immune-based protection against a challenge with a lethal dose of a virulent strain of Salmonella Typhimurium. Moreover, protective immunity was induced by a single dose of the vaccine, and the efficacy of protection was maintained for at least 6 months. These results suggest the use of the S. Typhimurium ruvB mutant as a novel vaccine.

Visiting the cell biology of Salmonella infection

Salmonella, a Gram-negative facultative intracellular pathogen is capable of infecting vast array of hosts. The striking ability of Salmonella to overcome every hurdle encountered in the host proves that they are true survivors. In the host, Salmonella infects various cell types and needs to survive and replicate by countering the defense mechanism of the specific cell. In this review, we will summarize the recent insights into the cell biology of Salmonella infection. Here, we will focus on the findings that deal with the specific mechanism of various cell types to control Salmonella infection. Further, the survival strategies of the pathogen in response to the host immunity will also be discussed in detail. Better understanding of the mechanisms by which Salmonella evade the host defense system and establish pathogenesis will be critical in disease management.

Cytokine levels in patients with Epstein-Barr virus associated laryngeal carcinoma

OBJECTIVE

Some researchers have suggested that Epstein-Barr virus may play a role in the pathogenesis of laryngeal malignancies. In order to clarify the role of cytokines in this disease context, the current study aimed to determine the serum levels of cytokines in Epstein-Barr virus DNA positive patients with laryngeal carcinoma.

SUBJECTS

The study included 10 patients with diagnosed laryngeal carcinoma and Epstein-Barr virus DNA positive tumour tissue samples. The control group comprised 10 Epstein-Barr virus DNA negative patients diagnosed with laryngeal carcinoma, 10 patients with acute Epstein-Barr virus infection and 10 healthy individuals.

METHOD

Serum cytokine levels were determined by enzyme-linked immunosorbent assay.

RESULTS

The Epstein-Barr virus DNA positive and negative laryngeal carcinoma patients showed no differences regarding serum levels of the following cytokines: interleukins 1beta, 2, 6 and 12, tumour necrosis factor alpha, and interferon gamma. However, serum levels of interleukin 10 and transforming growth factor beta1 were significantly higher in Epstein-Barr virus DNA positive laryngeal carcinoma patients compared with Epstein-Barr virus DNA negative laryngeal carcinoma patients (p < 0.05).

CONCLUSION

Our results suggest that the cytokines interleukin 10 and transforming growth factor beta1 may act as growth factors in Epstein-Barr virus related laryngeal carcinoma. These cytokines may thus represent potential targets for molecular therapeutic treatment for laryngeal carcinoma; they may also be useful as indicators of disease prognosis.

Molecular mechanisms of Salmonella virulence and host resistance

Salmonella species can cause typhoid fever and gastroenteritis in humans and pose a global threat to human health. In order to establish a successful infection, Salmonella utilize a large number of genes encoding a variety of virulence factors. Different animal models of infection have been used to better understand the mechanisms underlying each disease including cattle, rodents, and nematodes. To date, a number of different bacterial virulence factors have been identified using such animal models, most of which are secreted by two type three secretion systems (T3SS) encoded within Salmonella pathogenicity islands (SPI) 1 and 2. These proteins alter various host cell pathways, facilitating the invasion of epithelial cells during infection, as well as the survival and replication of Salmonella inside phagocytic cells. On the other hand, host genetics and resistance also play a role in the susceptibility to Salmonella infection. The natural resistance-associated macrophage protein 1 (Nramp1), for example, is critical for host defense, since mice lacking Nramp1 fail to control bacterial replication and succumb to low doses of S. Typhimurium. In this chapter, we analyze the different pathogen and host factors that play a role in the dynamic interaction between Salmonella and its host and their impact on disease.

Morphologic and cytokine profile characterization of Salmonella enterica serovar typhimurium infection in calves with bovine leukocyte adhesion deficiency

The role of neutrophils in the pathogenesis of Salmonella enterica Typhimurium-induced ruminant and human enteritis and diarrhea has yet to be characterized with in vivo models. To address this question, the in vivo bovine ligated ileal loop model of nontyphoidal salmonellosis was used in calves with the naturally occurring bovine leukocyte adhesion deficiency (BLAD) mutation whose neutrophils are unable to extravasate and infiltrate the extravascular matrix. Data obtained from 4 BLAD Holstein calves homozygous for BLAD (CD18-), 1 to 5 weeks of age, were compared with 4 controls, age-matched Holstein calves negative for BLAD (CD18+). Morphologic studies revealed that infection of CD18- calves with S Typhimurium resulted in no significant tissue infiltration by neutrophils, less tissue damage, reduced luminal fluid accumulation, and increased bacterial invasion, when compared with CD18+ calves. Ultrastructurally, lesions in enterocytes induced by S Typhimurium infection in CD18- calves--including attachment and disruption of the brush border, apical membrane ruffling formation, and cellular degeneration--were similar to the ones reported in the literature for CD18- calves. Study of cytokine gene expression by quantitative real-time polymerase chain reaction revealed that early stages of acute infection (4-8 hours postinfection) were associated with increased interleukin 8 gene expression in the absence of tissue influx of neutrophils in CD18- calves, whereas later stages of infection (12 hours postinfection) were associated with increased expression of growth-related oncogene alpha in the presence of neutrophil influx in CD18+ calves. In contrast, the proinflammatory cytokines interleukin 1beta and tumor necrosis factor alpha were poorly correlated with the presence or absence of tissue neutrophils.

IL-15 prevents apoptosis, reverses innate and adaptive immune dysfunction, and improves survival in sepsis

IL-15 is a pluripotent antiapoptotic cytokine that signals to cells of both the innate and adaptive immune system and is regarded as a highly promising immunomodulatory agent in cancer therapy. Sepsis is a lethal condition in which apoptosis-induced depletion of immune cells and subsequent immunosuppression are thought to contribute to morbidity and mortality. This study tested the ability of IL-15 to block apoptosis, prevent immunosuppression, and improve survival in sepsis. Mice were made septic using cecal ligation and puncture or Pseudomonas aeruginosa pneumonia. The experiments comprised a 2 x 2 full factorial design with surgical sepsis versus sham and IL-15 versus vehicle. In addition to survival studies, splenic cellularity, canonical markers of activation and proliferation, intracellular pro- and antiapoptotic Bcl-2 family protein expression, and markers of immune cell apoptosis were evaluated by flow cytometry. Cytokine production was examined both in plasma of treated mice and splenocytes that were stimulated ex vivo. IL-15 blocked sepsis-induced apoptosis of NK cells, dendritic cells, and CD8 T cells. IL-15 also decreased sepsis-induced gut epithelial apoptosis. IL-15 therapy increased the abundance of antiapoptotic Bcl-2 while decreasing proapoptotic Bim and PUMA. IL-15 increased both circulating IFN-gamma, as well as the percentage of NK cells that produced IFN-gamma. Finally, IL-15 increased survival in both cecal ligation and puncture and P. aeruginosa pneumonia. In conclusion, IL-15 prevents two immunopathologic hallmarks of sepsis, namely, apoptosis and immunosuppression, and improves survival in two different models of sepsis. IL-15 represents a potentially novel therapy of this highly lethal disorder.

Quantitative analysis of the immune response upon Salmonella typhimurium infection along the porcine intestinal gut

Salmonella enterica serovar Typhimurium causes enteric disease and compromises food safety. In pigs, the molecular response of the intestine to S. typhimurium has been traditionally characterized by in vitro models that do not reflect the actual immunological competence of the intestinal mucosa. In this work, we performed an oral S. typhimurium infection study to obtain insight into the in vitro response in three different sections (jejunum, ileum and colon) of the porcine intestine. For this, samples from one-month-old infected piglets were collected during a time course comprising 1, 2, and 6 days post inoculation to evaluate the intestinal response by quantifying the mRNA expression of gene coding for 28 innate immune system molecules using quantitative real-time PCR assays. In addition, samples from non-infected control animals were also employed to establish differences in the steady state gene expression between intestinal sections. The panel of quantified molecules included an assortment of cytokines, chemokines, pattern-recognition receptors, intracellular signaling molecules, transcription factors and antimicrobial molecules. Changes in gene expression occurred in the three different parts of the intestine and during the course of the S. typhimurium infection. Moreover, the high variation observed in expression patterns of genes coding for inflammatory mediators could indicate that each intestinal section responds differently to the infection. Thus, on the contrary to findings in the jejunum and colon, a down-regulation and lack of induction of some proinflammatory cytokine transcripts was observed in the ileum. Nevertheless, all chemoattractant cytokines assayed were up-regulated in the ileum and jejunum whereas only interleukin-8 and MIP-1α mRNA were over expressed in the colon. In conclusion, our results reveal regional differences in gene expression profiles along the porcine intestinal gut as well as regional differences in the inflammatory response to S. typhimurium infection. Taken together, these data should provide a basis for a complete understanding of the porcine intestinal response to bacterial infection.

The role of neutrophils in the event of intestinal inflammation

The transmigration of polymorphonuclear leukocytes (PMNs; neutrophils) into the intestinal lumen is a classical phenomenon associated with a wide variety of disease states, including those of both pathogenic and autoimmune/idiopathic origin. While PMNs are highly effective at killing invading pathogens by releasing microbiocidal products, excessive or unnecessary release of these substances can cause substantial damage to the intestinal epithelium. Therefore, it is necessary to understand the underlying mechanisms that lure neutrophils into the lumen allowing them to perform their desired functions, so that researchers may begin to identify which processes may be potential targets for inhibiting the transmigration of PMNs during noninfectious states.

Lactobacillus delbrueckii UFV-H2b20 induces type 1 cytokine production by mouse cells in vitro and in vivo

Lactobacillus delbrueckii UFV-H2b20 has been shown to increase clearance of bacteria injected into the blood of germ-free mice. Moreover, it induces the production of type 1 cytokines by human peripheral mononuclear cells. The objective of the present study was to investigate the production of inflammatory cytokines [interleukin-12 (IL-12 p40), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma)] triggered in vitro by live, heat-killed or lysozyme-treated L. delbrueckii UFV-H2b20 and in vivo by a live preparation. Germ-free, L. delbrueckii-monoassociated and lipopolysaccharide (LPS)-resistant C3H/HeJ mice were used as experimental models. UFV-H2b20 induced the production of IL-12 p40 and TNF-alpha by peritoneal cells and IFN-gamma by spleen cells from germ-free or monoassociated Swiss/NIH mice and LPS-hyporesponsive mice (around 40 ng/mL for IL-12 p40, 200 pg/mL for TNF-alpha and 10 ng/mL for IFN-gamma). Heat treatment of L. delbrueckii did not affect the production of these cytokines. Lysozyme treatment decreased IL-12 p40 production by peritoneal cells from C3H/HeJ mice, but did not affect TNF-alpha production by these cells or IFN-gamma production by spleen cells from the same mouse strain. TNF-alpha production by peritoneal cells from Swiss/NIH L. delbrueckii-monoassociated mice was inhibited by lysozyme treatment. When testing IL-12 p40 and IFN-gamma levels in sera from germ-free or monoassociated Swiss/NIH mice systemically challenged with Escherichia coli we observed that IL-12 p40 was produced at marginally higher levels by monoassociated mice than by germ-free mice (40 vs 60 ng/mL), but IFN-gamma was produced earlier and at higher levels by monoassociated mice (monoassociated 4 and 14 ng/mL 4 and 8 h after infection, germfree 0 and 7.5 ng/mL at the same times). These results show that L. delbrueckii UFV-H2b20 stimulates the production of type 1 cytokines in vitro and in vivo, therefore suggesting that L. delbrueckii might have adjuvant properties in infection in which these cytokines play a major role.

Effect of a BIOcocktail on the Immune Response at the Early Postoperative Period in Mice

Since human subjects and laboratory animals may develop impaired immune response during surgery and the postoperative period, efforts have been made to preserve normal immune functions following surgery by the administration of nutritional supplements and probiotics. The present study was designed to examine the effect of a new nutritional supplement, BIOcocktail, on immune parameters in mice exposed to surgery. Forty mice were assigned to 4 groups containing 10 animals each. Two control groups (with and without subsequent sham laparotomy) were given tap water for 45 min every day for 2 weeks. The remaining 2 groups, with and without laparotomy, received BIOcocktail given orally for the same period of time. The proliferative response of splenic cells (splenocytes) stimulated with phytohemagglutinin (PHA), concanavalin A (Con A) and lipopolysaccharide (LPS) was determined by [3H]thymidine uptake. Cytokine levels were measured in splenocyte supernatants and sera using enzyme-linked immunosorbent assay (ELISA) kits. Natural killer cell activity of splenocytes was evaluated by 51Cr-release assay. Laparotomy, without BIOcocktail administration, was followed by a decreased proliferative response of splenocytes to PHA, Con A, and LPS and an increase in interleukin (IL)-6 serum level. In addition, a decreased secretion of IL-1beta, IL-12 and tumor necrosis factor (TNF)-alpha by the splenocytes was observed. Mice treated with BIOcocktail before laparotomy maintained a preoperative level of splenocyte proliferative response and serum concentrations of IL-12. It is concluded that BIOcocktail administered to mice for 2 weeks before operation resulted in the preservation of T- and B-cell proliferative response to mitogens and in the prevention of postoperative decrease in IL-12 serum level.

Serum levels of interferon-γ, interleukin-12, tumour necrosis factor-α, and interleukin-10, and bacterial clearance in patients with gastroenteric Salmonella infection

Cytokines as intercellular signal molecules are responsible to a great extent for the pathological processes in Salmonella infection, as well as for the development of protective mechanisms in the disease. The present study aimed to reveal the correlation between serum levels of IFN-gamma, IL-12, TNF-alpha and IL-10, measured by enzyme-immunoassay, and clearance of bacteria in stool of patients with gastroenteric Salmonella infection. The study included 36 patients with culture confirmed gastroenteric Salmonella infection. At discharge from hospital, 20 patients recovered with bacteriological negative stool culture for Salmonella and 16 were Salmonella excretors. Mean serum concentrations of IFN-gamma, IL-12, TNF-alpha and IL-10 in the acute stage were compared between the 2 groups of patients and with those of healthy controls. Serum levels of examined cytokines were increased (p<0.001) in the patients in comparison with the healthy controls. In patients with early bacterial clearance mean serum concentrations of IFN-gamma, IL-12 and TNF-alpha in the acute stage were significantly (p<0.05) higher than in the non-clearance group. IL-10 serum level showed an opposite correlation (p<0.01) and higher values in Salmonella excretors. The accumulated data imply that Th1 type cytokines probably participate in protective immunity and early bacterial clearance in patients with gastroenteric Salmonella infection.

Interactions between human NK cells and macrophages in response to Salmonella infection

NK cells play a key role in host resistance to a range of pathogenic microorganisms, particularly during the initial stages of infection. NK cell interactions with cells infected with viruses and parasites have been studied extensively, but human bacterial infections have not been given the same attention. We studied crosstalk between human NK cells and macrophages infected with intracellular Salmonella. These macrophages activated NK cells, resulting in secretion of IFN-gamma and degranulation. Reciprocally, NK cell activation led to a dramatic reduction in numbers of intramacrophagic live bacteria. We identified three elements in the interaction of NK cells with infected macrophages. First, communication between NK cells and infected macrophages was contact-dependent. The second requirement was IL-2- and/or IL-15-dependent priming of NK cells to produce IFN-gamma. The third was activation of NK cells by IL-12 and IL-18, which were secreted by the Salmonella-infected macrophages. Adhesion molecules and IL-12Rbeta2 were enriched in the contact zone between NK cells and macrophages, consistent with contact- and IL-12/IL-18-dependent NK activation. Our results suggest that, in humans, bacterial clearance is consistent with a model invoking a "ménage à trois" involving NK cells, IL-2/IL-15-secreting cells, and infected macrophages.

Development of bacterial vectors for tumor-targeted gene therapy

Gene therapy holds great promise for the treatment of cancer. The success of the strategy relies on effective gene transfer into tumor microenvironments. Although a variety of gene delivery vehicles, such as viral vectors, has been developed, most of them suffer from some limitations, including inadequate tumor targeting, inefficient gene transfer, and potential toxicity. This situation suggests that it is necessary to develop novel vectors for effective tumor-targeted gene transfer. The discovery of tumor-targeting bacteria has spurred interest in the use of these bacteria as gene transfer vectors. In this review, we focus on the current status of the development of bacterial vectors for cancer gene therapy and highlight some of the directions that the field may take.

Effects of recombinant interferon-γ on cytokine secretion from monocyte-derived macrophages infected with Salmonella typhi

Salmonella typhi (S. typhi) is an important pathogen which causes typhoid fever. The cytokines released from the macrophages, playing a role in the host defense against Salmonella infection, are crucial in the defense against the infection. IFN-gamma provides a protection against Salmonella infection by developing macrophage activation in different mechanisms. This study was designed to investigate the effect of the recombinant IFN-gamma (rIFN-gamma) on the cytokines secreted from S. typhi stimulated macrophages. Macrophage isolation was done in the heparinized blood samples obtained from healthy people, and following the priming with rIFN-gamma for 72h the cells were stimulated by S. typhi and then the cytokine levels in culture supernatants were determined by enzyme-linked immunosorbent assay. It was observed that rIFN-gamma reversely increased the levels of IL-1, IL-2 the levels of which were decreased by S. typhi and that it increased TNF-alpha levels while suppressing the levels of antiinflammatory cytokines such as IL-10 and TGF-beta the levels of which were increased by S. typhi. Consequently, rIFN was observed to increase protective Th1 response by affecting the secretion of cytokine during S. typhi infection and it was considered to be a good target especially to prevent and treat invasive Salmonella infections.

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.

Early immune response following Salmonella enterica subspecies enterica serovar Typhimurium infection in porcine jejunal gut loops

Salmonella enterica subspecies enterica serovar Typhimurium, commonly called S. Typhimurium, can cause intestinal infections in humans and various animal species such as swine. To analyze the host response to Salmonella infection in the pig we used an in vivo gut loop model, which allows the analysis of multiple immune responses within the same animal. Four jejunal gut-loops were each inoculated with 3×10⁸ cfu of S. Typhimurium in 3 one-month-old piglets and mRNA expressions of various cytokines, chemokines, transcription factors, antimicrobial peptides, toll like and chemokine receptors were assessed by quantitative real-time PCR in the Peyer’s patch and the gut wall after 24 h. Several genes such as the newly cloned CCRL1/CCX-CKR were assessed for the first time in the pig at the mRNA level. Pro-inflammatory and T-helper type-1 (Th1) cytokine mRNA were expressed at higher levels in infected compared to non-infected control loops. Similarly, some B cell activation genes, NOD2 and toll like receptor 2 and 4 transcripts were more expressed in both tissues while TLR5 mRNA was down-regulated. Interestingly, CCL25 mRNA expression as well as the mRNA expressions of its receptors CCR9 and CCRL1 were decreased both in the Peyer’s patch and gut wall suggesting a potential Salmonella strategy to reduce lymphocyte homing to the intestine. In conclusion, these results provide insight into the porcine innate mucosal immune response to infection with entero-invasive microorganisms such as S. Typhimurium. In the future, this knowledge should help in the development of improved prophylactic and therapeutic approaches against porcine intestinal S. Typhimurium infections.

Analysis of porcine transcriptional response to Salmonella enterica serovar Choleraesuis suggests novel targets of NFkappaB are activated in the mesenteric lymph node

BACKGROUND

Specific knowledge of the molecular pathways controlling host-pathogen interactions can increase our understanding of immune response biology as well as provide targets for drug development and genetic improvement of disease resistance. Toward this end, we have characterized the porcine transcriptional response to Salmonella enterica serovar Choleraesuis (S. Choleraesuis), a Salmonella serovar that predominately colonizes swine, yet can cause serious infections in human patients. Affymetrix technology was used to screen for differentially expressed genes in pig mesenteric lymph nodes (MLN) responding to infection with S. Choleraesuis at acute (8 hours (h), 24 h and 48 h post-inoculation (pi)) and chronic stages (21 days (d) pi).

RESULTS

Analysis of variance with false discovery rate control identified 1,853 genes with significant changes in expression level (p-value < 0.01, q-value < 0.26, and fold change (FC) > 2) during infection as compared to un-inoculated control pigs. Down-regulation of translation-related genes at 8 hpi and 24 hpi implied that S. Choleraesuis repressed host protein translation. Genes involved in the Th1, innate immune/inflammation response and apoptosis pathways were induced significantly. However, antigen presentation/dendritic cell (DC) function pathways were not affected significantly during infection. A strong NFkappaB-dependent response was observed, as 58 known NFkappaB target genes were induced at 8, 24 and/or 48 hpi. Quantitative-PCR analyses confirmed the microarray data for 21 of 22 genes tested. Based on expression patterns, these target genes can be classified as an "Early" group (induced at either 8 or 24 hpi) and a "Late" group (induced only at 48 hpi). Cytokine activity or chemokine activity were enriched within the Early group genes GO annotations, while the Late group was predominantly composed of signal transduction and cell metabolism annotated genes. Regulatory motif analysis of the human orthologous promoters for both Early and Late genes revealed that 241 gene promoters were predicted to contain NFkappaB binding sites, and that of these, 51 Early and 145 Late genes were previously not known to be NFkappaB targets.

CONCLUSION

Our study provides novel genome-wide transcriptional profiling data on the porcine response to S. Choleraesuis and expands the understanding of NFkappaB signaling in response to Salmonella infection. Comparison of the magnitude and timing of porcine MLN transcriptional response to different Salmonella serovars, S. Choleraesuis and S. Typhimurium, clearly showed a larger but later transcriptional response to S. Choleraesuis. Both microarray and QPCR data provided evidence of a strong NFkappaB-dependent host transcriptional response during S. Choleraesuis infection. Our data indicate that a lack of strong DC-mediated antigen presentation in the MLN may cause S. Choleraesuis infected pigs to develop a systemic infection, and our analysis predicts nearly 200 novel NFkappaB target genes which may be applicable across mammalian species.

Molecular differences between the divergent responses of ovalbumin-specific CD4 T cells to alum-precipitated ovalbumin compared to ovalbumin expressed by Salmonella

CD4 T helper (Th) cell differentiation defined by in vitro cytokine-directed culture systems leaves major gaps in our knowledge of the mechanisms driving divergent Th differentiation. This is evident from our analysis of the response of mouse ovalbumin-specific CD4 T cells to different forms of ovalbumin that induce markedly distinct responses in vivo. We show that live attenuated ovalbumin-expressing Salmonella (SalOVA) induce Th1-associated T-bet and IFN-gamma. Conversely, alum-precipitated ovalbumin (alumOVA) induces the Th2-associated GATA-3 and IL-4. The early diversity occurring within these CD4 T cells isolated 3 days after immunization was assessed using real-time RT-PCR microfluidic cards designed with 384 selected genes. The technique was validated both at the population and single cell levels at different stages of the responses, showing beta2-microglobulin to be a more stably expressed reference mRNA than either beta-actin or 18S RNA. SalOVA was then shown selectively to induce the OVA-specific CD4 T cells to produce many chemokines and pro-inflammatory cytokines, contrasting with alumOVA-induced cells that only produced a few Th2-associated cytokines. Several cytokines and features associated with follicular helper functions were induced in the OVA-specific CD4 T cells by both antigens. Finally, IL-17RB is strongly associated with OVA-specific CD4 T cells responding to alumOVA, suggesting that alum may promote Th2 immune response through a role for the IL-25/IL-17RB pathway.

Distinct isoforms of phospholipase A2 mediate the ability of Salmonella enterica serotype typhimurium and Shigella flexneri to induce the transepithelial migration of neutrophils

Salmonella spp. and Shigella spp. are responsible for millions of cases of enteric disease each year worldwide. While these pathogens have evolved distinct strategies for interacting with the human intestinal epithelium, they both induce significant proinflammatory responses that result in massive transepithelial migration of neutrophils across the intestinal mucosa. It has previously been shown with Salmonella enterica serotype Typhimurium that the process of neutrophil transmigration is mediated in part by the secretion of hepoxilin A(3) (HXA(3); 8-hydroxy-11,12-epoxy-eicosatetraenoic acid), a potent neutrophil chemoattractant, from the apical surface of infected model intestinal epithelium. This study confirms that HXA(3) is also secreted in response to infection by Shigella flexneri, that it is produced by a pathway involving 12/15-lipoxygenase (12/15-LOX), and that S. enterica serovar Typhimurium and S. flexneri share certain elements in the mechanism(s) that underlies the otherwise separate signal transduction pathways that are engaged to induce polymorphonuclear leukocyte (PMN) transepithelial migration (protein kinase C and extracellular signal-regulated kinases 1 and 2, respectively). PMN transepithelial migration in response to infection with S. flexneri was dependent on 12/15-LOX activity, the enzyme responsible for the initial metabolism of arachidonic acid to HXA(3). Probing further into this pathway, we also found that S. enterica serovar Typhimurium and S. flexneri activate different subtypes of phospholipase A(2), a critical enzyme involved in the liberation of arachidonic acid from cellular membranes. Thus, although S. enterica serovar Typhimurium and S. flexneri utilize different mechanisms for triggering the induction of PMN transepithelial migration, we found that their reliance on 12/15-LOX is conserved, suggesting that enteric pathogens may ultimately stimulate similar pathways for the synthesis and release of HXA(3).

The inositol phosphatase SHIP controls Salmonella enterica serovar Typhimurium infection in vivo

The SH2 domain-containing inositol 5'-phosphatase, SHIP, negatively regulates various hematopoietic cell functions and is critical for maintaining immune homeostasis. However, whether SHIP plays a role in controlling bacterial infections in vivo remains unknown. Salmonella enterica causes human salmonellosis, a disease that ranges in severity from mild gastroenteritis to severe systemic illness, resulting in significant morbidity and mortality worldwide. The susceptibility of ship(+/+) and ship(-/-) mice and bone marrow-derived macrophages to S. enterica serovar Typhimurium infection was compared. ship(-/-) mice displayed an increased susceptibility to both oral and intraperitoneal serovar Typhimurium infection and had significantly higher bacterial loads in intestinal and systemic sites than ship(+/+) mice, indicating a role for SHIP in the gut-associated and systemic pathogenesis of serovar Typhimurium in vivo. Cytokine analysis of serum from orally infected mice showed that ship(-/-) mice produce lower levels of Th1 cytokines than do ship(+/+) animals at 2 days postinfection, and in vitro analysis of supernatants taken from infected bone marrow-derived macrophages derived to mimic the in vivo ship(-/-) alternatively activated (M2) macrophage phenotype correlated with these data. M2 macrophages were the predominant population in vivo in both oral and intraperitoneal infections, since tissue macrophages within the small intestine and peritoneal macrophages from ship(-/-) mice showed elevated levels of the M2 macrophage markers Ym1 and Arginase 1 compared to ship(+/+) cells. Based on these data, we propose that M2 macrophage skewing in ship(-/-) mice contributes to ineffective clearance of Salmonella in vivo.

Intravaginal immunization of mice with recombinant Salmonella enterica serovar Typhimurium expressing human papillomavirus type 16 antigens as a potential route of vaccination against cervical cancer

Cervical cancer, the second leading cause of cancer deaths in women, is the consequence of high-risk human papillomavirus (HPV) infections. Toward the development of therapeutic vaccines that can induce both innate and adaptive mucosal immune responses, we analyzed intravaginal (ivag) vaccine delivery of live attenuated Salmonella enterica serovar Typhimurium expressing HPV16L1 as a model antigen. Innate immune responses were examined in cervicovaginal tissues by determining gene expression patterns by microarray analysis using nylon membranes imprinted with cDNA fragments coding for inflammation-associated genes. At 24 h, a wide range of genes, including those for chemokines and Th1- and Th2-type cytokine and chemokine receptors were up-regulated in mice ivag immunized with Salmonella compared to control mice. However, the majority of transcripts returned to their steady-state levels 1 week after immunization, suggesting a transient inflammatory response. Indeed, cervicovaginal histology of immunized mice showed a massive, but transient, infiltration of macrophages and neutrophils, while T cells were still increased after 7 days. Ivag immunization also induced humoral and antitumor immune responses, i.e., serum and vaginal anti-HPV16VLP antibody titers similar to those induced by oral immunization, and significant protection in tumor protection experiments using HPV16-expressing C3 tumor cells. These results show that ivag immunization with live attenuated Salmonella expressing HPV16 antigens modulates the local mucosal gene expression pattern into a transient proinflammatory profile, elicits strong systemic and mucosal immunity against HPV16, and confers protection against HPV16 tumor cells subcutaneously implanted in mice. Examination of the efficacy with which ivag HPV16E7E6 Salmonella induces regression of tumors located in cervicovaginal tissue is warranted.

Motility allows S. Typhimurium to benefit from the mucosal defence

The mammalian intestine is colonized by a dense bacterial community, called microbiota. The microbiota shields from intestinal infection (colonization resistance). Recently, we have shown that enteropathogenic Salmonella spp. can exploit inflammation to compete with the intestinal microbiota. The mechanisms explaining the enhanced pathogen growth in the inflamed intestine are elusive. Here, we analysed the function of bacterial flagella in the inflamed intestine using a mouse model for acute Salmonella Typhimurium enterocolitis. Mutations affecting flagellar assembly (Fla(-)) and chemotaxis (Che(-)) impaired the pathogen's fitness in the inflamed intestine, but not in the normal gut. This was attributable to a localized source of high-energy nutrients (e.g. galactose-containing glyco-conjugates, mucin) released as an element of the mucosal defence. Motility allows Salmonella Typhimurium to benefit from these nutrients and utilize them for enhanced growth. Thus, nutrient availability contributes to enhanced pathogen growth in the inflamed intestine. Strategies interfering with bacterial motility or nutrient availability might offer starting points for therapeutic approaches.

Cytokine gene expression in chicken cecal tonsils following treatment with probiotics and Salmonella infection

Probiotics are currently employed for control of pathogens and enhancement of immune response in chickens. In this study, we investigated the underlying immunological mechanisms of the action of probiotics against colonization of the chicken intestine by Salmonella enterica subsp. enterica serovar Typhimurium (Salmonella serovar Typhimurium). Birds received probiotics by oral gavage on day 1 of age and, subsequently, received Salmonella serovar Typhimurium on day 2 of age. Cecal tonsils were removed on days 1, 3 and 5 post-infection (p.i.), RNA was extracted and subjected to real-time quantitative RT-PCR for measurement of interleukin (IL)-6, IL-10, IL-12 and interferon (IFN)-gamma gene expression. There was no significant difference in IL-6 and IL-10 gene expression in cecal tonsils of chickens belonging to various treatment groups. Salmonella serovar Typhimurium infection resulted in a significant increase in IL-12 expression in cecal tonsils on days 1 and 5p.i. However, when chickens were treated with probiotics prior to experimental infection with Salmonella, the level of IL-12 expression was similar to that observed in uninfected control chickens. Treatment of birds with probiotics resulted in a significant decrease in IFN-gamma gene expression in cecal tonsils of chickens infected with Salmonella compared to the Salmonella-infected birds not treated with probiotics. These findings reveal that repression of IL-12 and IFN-gamma expression is associated with probiotic-mediated reduction in intestinal colonization with Salmonella serovar Typhimurium.

Novel insight in the association between salmonellosis or campylobacteriosis and chronic illness, and the role of host genetics in susceptibility to these diseases

We studied the role of host genetics in the susceptibility to severe Salmonella and Campylobacter infections and chronic sequelae of these infections. Participants of a previous case-control study were sent a buccal swab kit and a questionnaire about occurrence of chronic sequelae. Single nucleotide polymorphisms (SNPs) in the TLR4 (rs4986790), IFNG (rs2430561 and rs1861493), STAT1 (rs1914408), IL1B (rs16944), NRAMP (SLC11A1 rs2276631), JUN (rs11688) and VDR (rs10735810) genes were determined. In total, 687 controls, 457 Campylobacter cases and 193 Salmonella cases participated. None of the SNPs were associated with Campylobacter or Salmonella infections. None of the participants developed Guillain-Barré, Miller-Fisher or Reiter's syndrome. Reactive arthritis occurred in 5% and 2% of cases and controls, respectively. Campylobacter cases more frequently experienced gastroenteritis episodes than controls. Campylobacter or Salmonella infection in women, use of proton pump inhibitors and an SNP in the IFNG gene were independent risk factors for reactive arthritis. Another SNP in the IFNG gene and use of proton pump inhibitors were risk factors for recurrent episodes of gastroenteritis. In conclusion, reactive arthritis and recurrent gastroenteritis episodes are common after infection and host genetic factors play a role in susceptibility to these long-term health effects.