Salmonella infection does not increase expression and activity of the high affinity IL-12 receptor

The potential role of nontyphoidal salmonellosis in gastric cancer: a nationwide matched cohort study

BACKGROUND

The research is to explore the association between nontyphoidal salmonellosis (NTS) and subsequent gastric cancer.

METHODS

We conducted a retrospective study by analyzing hospitalization dataset from the National Health Insurance Research Database in Taiwan. Patients aged 20 years and older with NTS (n = 9 097) admitted between January 1, 2000, and December 31, 2012, were enrolled and followed up until December 31, 2013. The primary outcome was the incidence of gastric cancer. Cox proportional hazards regression was used to estimate the risk of malignancy, accounting for the competing risk of death. In addition, we conducted a sensitivity analysis by propensity score matching and exclusion of malignancy within 1 year observation to minimize measurable confounding and protopathic bias. Negative controls were applied to examine the presence of possible unmeasured confounders in the study.

RESULTS

The study included 18 194 patients (9097 in each NTS and non-NTS group). The median follow-up time was 7 years. The incidence density rate of gastric cancer was 0.72 per 1000 person-years for the NTS group and 0.40 per 1000 person-years for the non-NTS group. The NTS group had a modestly higher risk of gastric cancer (aHR, 2.02; 95% CI 1.18-3.45) than the non-NTS group. The sensitivity analyses revealed consistent results.

CONCLUSIONS

Patients with NTS are associated with increased risk of subsequent gastric cancer compared with non-NTS patients. Future research is needed to examine whether NTS is parallel, reactive or causative to gastric cancer.

Diet-induced obese mice exhibit altered immune responses to early Salmonella Typhimurium oral infection

Obesity is a chronic disease associated with different metabolic diseases as well as alterations in immune cell function. It is characterized by a chronic systemic low grade inflammation. There are several studies demonstrating the influence of obesity on the impaired immune response to infection. However, it is not completely clear whether the obese environment influences the development or maintenance of the immune response against infections. The aim of this study was to determine how obesity induced by a high-fat diet affects the immune response to an early oral Salmonella infection. Four groups of mice were kept in separate cages. Two of these designated as controls, fed with a normal diet; whereas other two groups were fed with a high fat diet for 10 weeks. Some mice were used for Salmonella oral infection. After 7 days of oral infection with S. Thypimurium the proportions of spleen cell subsets expressing activation markers in normal diet and HFD obese mice were stained with monoclonal antibodies and analyzed by flow cytometry. Also, mRNA levels of different cytokines were quantified by RT-PCR. It was found that obesity affects the function of the immune system against an early oral Salmonella infection, decreasing NK cells, altering the expression of activation molecules as well as cytokines mRNA levels. Interestingly, the expression some activation molecules on T lymphocytes was reestablished after Salmonella infection, but not the CD25 expression. Immune alterations could lead to immunosuppression or increased susceptibility to infections in HFD obese mice.

Exploring the immune response of porcine mesenteric lymph nodes to Salmonella enterica serovar Typhimurium: an analysis of transcriptional changes, morphological alterations and pathogen burden

Infections caused by Salmonella enterica serovar Typhimurium (S. typhimurium) cause important economic problems in the swine industry and threaten the integrity of a safe and healthy food supply. Controlling the prevalence of Salmonella in pig production requires a thorough knowledge of the response processes that occurs in the gut associated immune tissues. To explore the in vivo porcine response to S. typhimurium, MLN samples from four control pigs and twelve infected animals at 1, 2 and 6 days post infection (dpi) were collected to quantify the mRNA expression of gene coding for 42 innate immune-related molecules. In addition, the presence of S. typhimurium in MLN was examined and its effect on tissue micro-anatomy. Higher S. typhimurium loads were observed at 2dpi, triggering an innate immune response, marked by a substantial infiltration of phagocytes and up-regulation of pro-inflammatory genes. Such response resulted in a significant decrease in pathogen burden in MLN at 6dpi, although Salmonella could not be completely eliminated from tissue. Furthermore, our results suggest that in porcine infections, S. typhimurium might interferes with dendritic cell-T cell interactions and this strategy could be involved in the conversion of Salmonella infected pigs to a carrier state.

Type IVB piliated Salmonella typhi enhance IL-6 and NF-κB production in human monocytic THP-1 cells through activation of protein kinase C

Salmonella typhi is an important human pathogen responsible for typhoid fever. Type IVB pili, encoded by the S. typhi pil operon located in the major pathogenicity island, are used to facilitate bacterial entry into human intestinal cells in vitro and may be important in the mediation of enteric fever in humans. However, possible involvement of the type IVB pili of S. typhi in signal transduction in infected immune cells has not been examined previously. In this study, we have compared the effect of piliated and nonpiliated S. typhi on the activities of protein kinase C (PKC), the production of interleukin-6 (IL-6) and nuclear transcription factor NF-kappaB in human monocytic THP-1 cells. We find that piliated S. typhi can stimulate significantly higher activities of PKC, the production of IL-6 and NF-kappaB than a nonpiliated strain based on substrate phosphorolysis kinase assay, Western blot, RT-PCR, and luciferase reporter gene assay. In time course experiments, PKC activity increased in a time-dependent fashion after stimulation by the piliated bacteria. The PKC inhibitor Dequalinium chloride (DECA) remarkably reduced the production of IL-6, NF-kappaB and the activity of PKC induced by the piliated S. typhi. These results suggest that the induction of IL-6 and NF-kappaB depend on the PKC signal pathway. Our report demonstrates that the type IVB pili of S. typhi play important roles in the production of NF-kappaB and the proinflammatory cytokine IL-6, and in the stimulation of PKC activity and therefore, may have effects on the development of fever and other inflammatory responses.

Expression and immunogenicity of an Escherichia coli K99 fimbriae subunit antigen in soybean

Enterotoxigenic Escherichia coli (ETEC) cause acute diarrhea in humans and farm animals, and can be fatal if the host is left untreated. As a potential alternative to traditional needle vaccination of cattle, we investigated the feasibility of expressing the major K99 fimbrial subunit, FanC, in soybean (Glycine max) for use as an edible subunit vaccine. As a first step in this developmental process, a synthetic version of fanC was optimized for expression in the cytosol and transferred to soybean via Agrobacterium-mediated transformation. Western analysis of T(0) events revealed the presence of a peptide with the expected mobility for FanC in transgenic protein extracts, and immunofluorescense confirmed localization to the cytosol. Two T(0) lines, which accumulated FanC to levels near 0.5% of total soluble protein, were chosen for further molecular characterization in the T(1) and T(2) generations. Mice immunized intraperitoneally with protein extract derived from transgenic leaves expressing synthetic FanC developed significant antibody titers against bacterially derived FanC and produced antigen-specific CD4(+) T lymphocytes, demonstrating the ability of transgenic FanC to function as an immunogen. These experiments are the first to demonstrate the expression and immunogenicity of a model subunit antigen in the soybean system, and mark the first steps toward the development of a K99 edible vaccine to protect against ETEC.

STAT3 activation in macrophages following infection with Salmonella

The induction of signal transducer and activators of transcription (STATs) in macrophages is necessary for cellular activation, and we investigated the activation of STAT3 in these cells following infection with Salmonella. Increased activation of STAT3 was observed at 6 and 24 h post-infection in the mesenteric lymph nodes and spleens when compared to control mice. CD11b+ cells isolated from the mesenteric lymph nodes of infected mice demonstrated increased STAT3 activation as early as 6 h following infection. Culturing bone marrow-derived macrophages with Salmonella resulted in translocation of STAT3 to the nucleus and STAT3 phosphorylation as early as 30 min post-exposure. Increased STAT3 activation was also observed in the lymphoid organs or in macrophages from mice deficient for IL-6 or IL-10 production following infection. Taken together, these studies clearly demonstrate an early increase in the activation of STAT3 in vivo and in vitro following infection with wild type Salmonella.

Murine gammaherpesvirus-68 elicits robust levels of interleukin-12 p40, but not interleukin-12 p70 production, by murine microglia and astrocytes

Murine gammaherpesvirus-68 (gamma HV-68) is a tractable model to investigate the pathophysiology of human gammaherpesvirus infections, including Epstein-Barr virus (EBV). Herpesvirus infections are thought to play a role in the pathology of damaging, inflammatory diseases states of the central nervous system (CNS), such as multiple sclerosis. The ability of the host to mount a strong cell-mediated immune response is critical in determining the outcome of viral infections. Interleukin (IL)-12 is an important inflammatory cytokine that plays a pivotal role in the development of protective cell-mediated immune responses to viral infections. Given recent reports of associations between gammaherpesvirus infections and inflammatory disorders of the CNS, the authors investigated the ability of gamma HV-68 to induce the production of bioactive IL-12 in resident CNS cell types. In the present study, the authors demonstrate that gamma HV-68 infection is a potent stimulus for IL-12p40 production by murine microglia and astrocytes. However, despite the elevated expression of mRNA encoding IL-12p40 subunit, concomitant with robust secretion of IL-12p40 protein, gamma HV-68 failed to elicit the production of the bioactive IL-12p70 heterodimer. This failure did not result from an absence of T lymphocyte-derived signals or interactions between CNS cell types as determined by coculture studies. Taken together, these data suggest that the resident CNS cell types, astrocytes and microglia, are not significant sources of proinflammatory IL-12p70 in response to gammaherpesvirus infection. Indeed, the production of IL-12p40 may point to an anti-inflammatory role for these cells during herpesvirus infections of the CNS.

Cyclooxygenase-2-mediated prostaglandin E2 production in mesenteric lymph nodes and in cultured macrophages and dendritic cells after infection with Salmonella

Although numerous studies have demonstrated the ability of intestinal epithelial cells to produce PGs after infection with wild-type strains of Salmonella, few studies have focused on Salmonella-induced prostanoids in mucosal lymphoid tissues. This is surprising in view of the profound effects PGs can have on the host response. To begin to address PG production at mucosal sites, mice were orally inoculated with Salmonella, and at varying times postinfection cyclooxygenase-2 (COX-2) mRNA expression and PGE(2) synthesis were investigated. COX-2 mRNA expression was highly inducible in the mesenteric lymph nodes, whereas COX-1 mRNA levels were constitutive. PGE(2) production also increased significantly in the mesenteric lymph nodes following exposure to viable Salmonella, but not after exposure to killed bacteria. This increased PGE(2) response could be blocked by treatment of mice with the selective COX-2 inhibitor, celecoxib. Treatment of mice with celecoxib during salmonellosis resulted in increased viable bacteria in the mesenteric lymph nodes by day 3 postinfection. However, celecoxib treatment prolonged the survival of lethally infected animals. In vitro studies demonstrated Salmonella-induced up-regulation of COX-2 mRNA expression and PGE(2) secretion by both macrophages and dendritic cells, which could also be blocked in the presence of celecoxib. Interestingly, exposure of these cultured APCs to viable Salmonella was a much greater stimulus for induction of PGE(2) synthesis than exposure to Salmonella-derived LPS. The present study demonstrates induction of PGE(2) synthesis in mesenteric lymph nodes, macrophages, and dendritic cells after infection with wild-type salmonella.

Functional CD40 expression induced following bacterial infection of mouse and human osteoblasts

Bacterially induced bone infections often result in significant local inflammatory responses which are coupled with loss of bone. However, the mechanisms necessary for the protective host response, or those responsible for pathogen-induced bone loss, are not clear. Recent evidence demonstrates that bacterially infected osteoblasts secrete chemokines and cytokines, suggesting that these cells may have an unappreciated role in supporting localized inflammation. In this study, mouse and human osteoblasts were investigated for their ability to express functional CD40 upon exposure to two important pathogens of bone, Staphylococcus aureus and Salmonella enterica serovar Dublin. Bacterial infection of cultured mouse or human osteoblasts resulted in increased CD40 mRNA and CD40 protein expression induced by either pathogen. Importantly, CD40 expression by osteoblasts was functional, as assessed by ligation of this molecule with recombinant, soluble CD154. CD40 activity was assessed by induction of interleukin-6 and granulocyte-macrophage colony-stimulating factor in osteoblasts following ligation. Cocultures of activated CD4(+) T lymphocytes and osteoblasts could interact via CD40 and CD154, since an antibody against CD40 could block macrophage inflammatory protein-1alpha secretion. Taken together, these studies conclusively demonstrate that infected osteoblasts can upregulate expression of functional CD40 molecules which mediate cytokine secretion. This surprising result further supports the notion that bone-forming osteoblasts can directly interact with CD154-expressing cells (i.e., T lymphocytes) and can contribute to the host response during bone infection.

Fimbriated Salmonella enterica serovar typhimurium abates initial inflammatory responses by macrophages

Oral immunization of mice with a Salmonella vaccine expressing colonization factor antigen I (CFA/I) from enterotoxigenic Escherichia coli results in the rapid onset of interleukin-4 (IL-4) and IL-5 production, which explains the observed elevations in mucosal immunoglobulin A (IgA) and serum IgG1 antibodies. In contrast, oral immunization with the Salmonella vector does not result in the production of Th2-type cytokines. To begin to assess why such differences exist between the two strains, it should be noted that in vitro infection of RAW 264.7 macrophages resulted in the absence of nitric oxide (NO) production in cells infected with the Salmonella-CFA/I vaccine. This observation suggests differential proinflammatory cytokine production by these isogenic Salmonella strains. Upon measurement of proinflammatory cytokines, minimal to no tumor necrosis factor alpha (TNF-alpha), IL-1alpha, IL-1beta, or IL-6 was produced by Salmonella-CFA/I-infected RAW 264.7 or peritoneal macrophages, but production was greatly induced in Salmonella vector-infected macrophages. Only minute levels of IL-12 p70 were induced by Salmonella vector-infected macrophages, and none was induced by Salmonella-CFA/I-infected macrophages. The absence of IL-12 was not due to overt increases in production of either IL-12 p40 or IL-10. CFU measurements taken at 8 h postinfection showed no differences in colonization in RAW 264.7 cells infected with either Salmonella construct, but there were differences in peritoneal macrophages. However, after 24 h, the Salmonella vector strain colonized to a greater extent in RAW 264.7 cells than in peritoneal macrophages. Infection of RAW 264.7 cells or peritoneal macrophages with either Salmonella construct showed no difference in macrophage viabilities. This evidence shows that the expression of CFA/I fimbriae alters how macrophages recognize or process salmonellae and prevents the rapid onset of proinflammatory cytokines which is typical during Salmonella infections.

Murine gammaherpesvirus-68-induced interleukin-10 increases viral burden, but limits virus-induced splenomegaly and leukocytosis

Based on its genomic sequence and its pathogenesis, murine gammaherpesvirus-68 (gammaHV-68) has been established as a tractable model for the study of viral infections caused by the human gammaherpesviruses, Epstein-Barr virus or human herpesvirus-8. Despite significant advances, the mechanisms responsible for gammaHV-68-induced alterations in the protective host response, and the accompanying virus-induced leukocytosis, are not clear. In the present study, we questioned whether viral infection resulted in endogenous interleukin-10 (IL-10) production that might alter the host response. Infection of C57BL/6 mice resulted in increased IL-10 expression, demonstrating that gammaHV-68 could induce endogenous production of this cytokine. Infected C57BL/6 mice demonstrated the characteristic splenomegaly associated with this viral infection, however, we were surprised to discover that the splenomegaly was greater in syngeneic mice genetically deficient in IL-10 (IL-10-/-). These results strongly suggested that endogenously produced IL-10 might serve to limit leukocytosis in wild-type mice. Quantification of viral burden demonstrated a significant elevation in C57BL/6 versus IL-10-/- mice, with increases in virus being observed in both the macrophage and B-lymphocyte populations. The decreased viral load in syngeneic IL-10-/- mice correlated with an increased expression of endogenous IL-12, suggesting a mechanism of protection that was IL-12 dependent. Taken together, these studies demonstrate a surprising dichotomy for endogenous IL-10 production during gammaHV-68 infection. While the lack of IL-10 results in increased IL-12 expression and a lower viral burden, IL-10-/- mice also experience an increased leukocytosis.