Activation of iNKT Cells Prevents Salmonella-Enterocolitis and Salmonella-Induced Reactive Arthritis by Downregulating IL-17-Producing γδT Cells

Reactive arthritis (ReA) is an inflammatory condition of the joints that arises following an infection. Salmonella enterocolitis is one of the most common infections leading to ReA. Although the pathogenesis remains unclear, it is known that IL-17 plays a pivotal role in the development of ReA. IL-17-producers cells are mainly Th17, iNKT, and γδT lymphocytes. It is known that iNKT cells regulate the development of Th17 lineage. Whether iNKT cells also regulate γδT lymphocytes differentiation is unknown. We found that iNKT cells play a protective role in ReA. BALB/c Jα18−/− mice suffered a severe Salmonella enterocolitis, a 3.5-fold increase in IL-17 expression and aggravated inflammation of the synovial membrane. On the other hand, activation of iNKT cells with α-GalCer abrogated IL-17 response to Salmonella enterocolitis and prevented intestinal and joint tissue damage. Moreover, the anti-inflammatory effect of α-GalCer was related to a drop in the proportion of IL-17-producing γδT lymphocytes (IL17-γδTcells) rather than to a decrease in Th17 cells. In summary, we here show that iNKT cells play a protective role against Salmonella-enterocolitis and Salmonella-induced ReA by downregulating IL17-γδTcells

Impaired synthesis and secretion of SopA in <i>Salmonella</i> Typhimurium <i>dam</i> mutants

DNA adenine methylation regulates virulence gene expression in certain bacteria, including Salmonella Typhimurium. The aim of this study was to investigate the involvement of DNA adenine methylase (Dam) methylation in the expression and secretion of the SPI-1 effector protein SopA. For this purpose, SopA–FLAG-tagged wild-type and dam strains of Salmonella Typhimurium were constructed. The expression and secretion of SopA were determined in bacterial culture and in intracellular bacteria recovered from infected HEp-2 epithelial cells. Bacterial culture supernatants and pellets were used to investigate secreted proteins and cell-associated proteins, respectively. Western blot and quantitative reverse transcriptase PCR analysis showed that the dam mutant expresses lower levels of SopA than the wild-type strain. Interestingly, the strain lacking Dam synthesizes SopA under nonpermissive conditions (28 °C). In addition, SopA secretion was drastically impaired in the dam mutant. In vivo experiments showed that the intracellular Salmonella dam mutant synthesizes SopA although in lower amounts than the wild-type strain. Taken together, our results suggest that Dam methylation modulates the expression and secretion of SopA in Salmonella Typhimurium

Salmonella enterica serovar Enteritidis enterocolitis during late stages of gestation induces an adverse pregnancy outcome in the murine model.

Foodborne diseases caused by Salmonella enterica serovar Enteritidis (S. Enteritidis) are a significant health problem. Pregnancy, state of immunological tolerance, is a predisposing condition for the development of infections with intracellular pathogens. Salmonella species can cause pregnancy complications such as chorioamnionitis, transplacental fetal infection, pre term labor, abortions, neonatal and maternal septicemia. However, the specific mechanisms by which Salmonella infections trigger these alterations are not clear. In the present work, using a self-limiting enterocolitis murine model, we show that the ingestion of a low dose of S. Enteritidis at late stages of pregnancy (day 15 of gestation) is sufficient to induce massive maternal infection. We found that Salmonella infection leads to 40% of pre term delivery, 33% of abortion and fetal growth restriction. Placental dysfunction during S. Enteritidis enterocolitis was confirmed through cellular infiltration and hypoxia markers (MPO activity and COX-1 and COX-2 expression, respectively). Apoptosis in placental tissue due to Salmonella infection was also evident at day 18 of gestation when investigated by morphometric procedure, DNA fragmentation and Fas/FasL expression. Also, the expression of IFN-γ, TNF-α, IL-17 and IL-10 was up regulated in response to Salmonella not only in placenta, but also in amniotic fluid and maternal serum. Altogether, our results demonstrate that S. Enteritidis enterocolitis during late stages of gestation causes detrimental effect on pregnancy outcome

Schematic diagram of the proposed regulatory network of <i>wzz</i> gene expression in <i>S.</i> Enteritidis.

<p>The regulatory cascade for <i>wzz</i> gene expression involves Dam methylation, PmrB/PmrA and RcsC/RcsD/RcsB two-component regulatory system and a putative third regulator (X). Proteins are indicated by ovals, whereas genes are symbolized by block arrows. Black dots indicate methylation sites (5′-GATC-3′ sequences). Dashed lines indicate direct interactions demonstrated in <i>S.</i> Typhimurium. Positive regulation (induction) is labeled with ↑ and (+), whereas negative regulation (repression) is labeled with ⊥ and (−). The question mark indicates a putative regulation.</p

Effect of LCFM on intestinal IL-10 and TGF-β.

<p>Cytokines expression was analyzed by qPCR. <i>L. casei</i> only group: mice fed for a week with LCFM. EC group: mice received 20 mg of streptomycin 24 h before intragastric infection with 3-4 x 10³ CFU of <i>S</i>. Enteritidis. <i>L. casei</i> + EC group: mice received the probiotic for a week before enterocolitis onset. Control group: untreated mice. <i>L. casei</i> + Strep group: animals were fed with the probiotic for a week and then received streptomycin. Results are expressed as mean +/- SD. Four animals per group were analyzed. (NS): no significant differences. Representative data from 3 independent experiments.</p

Bacterial strains and plasmids used in this study.

<p>Bacterial strains and plasmids used in this study.</p