The chemerin/CMKLR1 axis regulates intestinal graft-versus-host disease.

Gastrointestinal graft-versus-host disease (GvHD) is a major cause of mortality and morbidity following allogeneic bone marrow transplantation (allo-BMT). Chemerin is a chemotactic protein that recruits leukocytes to inflamed tissues by interacting with ChemR23/CMKLR1, a chemotactic receptor expressed by leukocytes, including macrophages. During acute GvHD, chemerin plasma levels were strongly increased in allo-BM-transplanted mice. The role of the chemerin/CMKLR1 axis in GvHD was investigated using Cmklr1-KO mice. WT mice transplanted with an allogeneic graft from Cmklr1-KO donors (t-KO) had worse survival and more severe GvHD. Histological analysis demonstrated that the gastrointestinal tract was the organ mostly affected by GvHD in t-KO mice. The severe colitis of t-KO mice was characterized by massive neutrophil infiltration and tissue damage associated with bacterial translocation and exacerbated inflammation. Similarly, Cmklr1-KO recipient mice showed increased intestinal pathology in both allogeneic transplant and dextran sulfate sodium-induced colitis. Notably, the adoptive transfer of WT monocytes into t-KO mice mitigated GvHD manifestations by decreasing gut inflammation and T cell activation. In patients, higher chemerin serum levels were predictive of GvHD development. Overall, these results suggest that CMKLR1/chemerin may be a protective pathway for the control of intestinal inflammation and tissue damage in GvHD.

Within-host evolution of a gut pathobiont facilitates liver translocation.

Gut commensal bacteria with the ability to translocate across the intestinal barrier can drive the development of diverse immune-mediated diseases1-4. However, the key factors that dictate bacterial translocation remain unclear. Recent studies have revealed that gut microbiota strains can adapt and evolve throughout the lifetime of the host5-9, raising the possibility that changes in individual commensal bacteria themselves over time may affect their propensity to elicit inflammatory disease. Here we show that within-host evolution of the model gut pathobiont Enterococcus gallinarum facilitates bacterial translocation and initiation of inflammation. Using a combination of in vivo experimental evolution and comparative genomics, we found that E. gallinarum diverges into independent lineages adapted to colonize either luminal or mucosal niches in the gut. Compared with ancestral and luminal E. gallinarum, mucosally adapted strains evade detection and clearance by the immune system, exhibit increased translocation to and survival within the mesenteric lymph nodes and liver, and induce increased intestinal and hepatic inflammation. Mechanistically, these changes in bacterial behaviour are associated with non-synonymous mutations or insertion-deletions in defined regulatory genes in E. gallinarum, altered microbial gene expression programs and remodelled cell wall structures. Lactobacillus reuteri also exhibited broadly similar patterns of divergent evolution and enhanced immune evasion in a monocolonization-based model of within-host evolution. Overall, these studies define within-host evolution as a critical regulator of commensal pathogenicity that provides a unique source of stochasticity in the development and progression of microbiota-driven disease.

Are Pattern Recognition Receptors Associated with Hepatocellular Carcinoma?

BACKGROUND: Hepatocellular carcinoma (HCC) is one of the important causes of mortality due to malignancy. Toll-like receptors (TLRs) are very important in liver pathophysiology in terms of their roles in the innate immune system, such as the regulation of inflammation, wound healing, stimulation of adaptive immune responses, promotion of epithelial regeneration, and carcinogenesis. In this study, we planned to examine the role of TLR1 (rs4833095, rs5743551) and nucleotide-binding oligomerization domain (NOD2) (rs2066844, rs2066845, rs2066847) polymorphisms in the development of HCC and their effects on the clinical presentation of HCC patients. METHODS: Our study was designed prospectively. Cirrhotic and HCC patients who were followed up in our clinic between January 2015 and September 2018 were included in the study. Sex, age, cirrhosis etiology, Child-Pugh class, and MELD scores were recorded. TLR1 and NOD2 polymorphisms were studied by the PCR method. RESULTS: HCC developed in 88 (31.4%) of the 280 patients who were followed up, either during the recruitment phase of our study or during the follow-up. The mean follow-up time of our patient group was 17.04 ± 11.72 months, and the mean follow-up time of HCC patients was 12.09 ± 10.26 months. TLR1 (rs5743551) polymorphism was associated with HCC development (P = .003). TLR1 (rs5743551) and NOD2 (rs2066844) polymorphisms were associated with the development of spontaneous bacterial peritonitis (SBP) in the HCC patient group (P = .013 and P = .021, respectively). CONCLUSION: We think that increased bacterial translocation in cirrhotic patients may contribute to HCC development by causing chronic inflammation, especially in patients with TLR 1 (rs5743551) polymorphism.

Effects of Lipid Peroxidation-Mediated Ferroptosis on Severe Acute Pancreatitis-Induced Intestinal Barrier Injury and Bacterial Translocation.

Ferroptosis is a recently recognized type of regulated cell death characterized by iron- and lipid peroxidation-mediated nonapoptotic cell death. However, whether ferroptosis is involved in severe acute pancreatitis- (SAP-) induced intestinal barrier injury is unknown. The aim of this study was to investigate whether ferroptosis is involved in SAP-induced intestinal barrier injury, particularly intestinal epithelial cell (IEC) death, and determine whether the inhibition of ferroptosis would ameliorate intestinal barrier injury and prevent bacterial translocation (BT). Sodium taurocholate (5%) was retrogradely perfused into the biliopancreatic duct to establish a rat model of SAP. The rats were divided into three groups: sham operation (SO), SAP-induced intestinal barrier injury (SAP), and ferroptosis inhibitor liproxstatin-1 (SAP + Lip). Serum indexes were measured in the rats. In addition, the biochemical and morphological changes associated with ferroptosis were observed, including iron accumulation in intestinal tissue, lipid peroxidation levels, and mitochondrial shrinkage. Hematoxylin staining and eosin staining were used to assess histological tissue changes. Western blot, RT-PCR, and immunofluorescent staining were performed to analyze the expression of ferroptosis-related proteins and genes as well as tight junction. BT was detected by 16S rDNA sequencing analysis. The results indicated that ferroptosis was significantly induced in the IECs from rats with SAP and ferroptosis was mediated by lipid peroxidation. The specific lipid peroxidation of IECs clearly upregulated ferroptosis and exacerbated intestinal barrier injury. Furthermore, treatment with liproxstatin-1 lowered the levels of serum damage markers, decreased lipid peroxidation, and alleviated intestinal and acute remote organ injury in SAP rats. In addition, inhibition of ferroptosis reduced BT. Our findings are the first to demonstrate that ferroptosis contributes to SAP-induced intestinal barrier injury via lipid peroxidation-mediated IEC death. These results suggest that ferroptosis is a potential therapeutic target for SAP-induced intestinal barrier injury.

Plasma Biomarkers of Risk of Tuberculosis Recurrence in HIV Co-Infected Patients From South Africa.

There is an urgent need to identify immunological markers of tuberculosis (TB) risk in HIV co-infected individuals. Previously we have shown that TB recurrence in HIV co-infected individuals on ART was associated with markers of systemic inflammation (IL-6, IL1ß and IL-1Rα). Here we examined the effect of additional acute inflammation and microbial translocation marker expression on risk of TB recurrence. Stored plasma samples were drawn from the TB Recurrence upon Treatment with HAART (TRuTH) study, in which individuals with previously treated pulmonary TB were screened for recurrence quarterly for up to 4 years. Recurrent TB cases (n = 37) were matched to controls (n = 102) by original trial study arm assignment and ART start date. Additional subsets of HIV infected (n = 41) and HIV uninfected (n = 37) individuals from Improving Recurrence Success (IMPRESS) study were sampled at active TB and post successful treatment completion. Plasma concentrations of soluble adhesion molecules (sMAdCAM, sICAM and sVCAM), lipopolysaccharide binding protein (LBP) and transforming growth factor-beta (TGF-ß1, TGF-ß2, TGF-ß3) were measured by multiplex immunoassays and ELISA. Cytokine data was square root transformed in order to reduce variability. Multivariable analysis adjusted for a number of potential confounders measured at sample time-point: age, BMI, CD4 count, viral load (VL) and measured at baseline: presence or absence of lung cavities, previous history of TB, and WHO disease stage (4 vs 3). The following analytes were associated with increased risk of TB recurrence in the multivariable model: sICAM (aOR 1.06, 95% CI: 1.02-1.12, p = 0.009), LBP (aOR 8.78, 95% CI: 1.23-62.66, p = 0.030) and TGF-ß3 (aOR 1.44, 95% CI 1.01-2.05, p = 0.044). Additionally, we observed a positive correlation between LBP and sICAM (r= 0.347, p<0.0001), and LBP and IL-6, identified to be one of the strongest predictors of TB risk in our previous study (r=0.623, p=0.03). These data show that increased risk of TB recurrence in HIV infected individuals on ART is likely associated with HIV mediated translocation of microbial products and the resulting chronic immune activation.

YSIRK-G/S-directed translocation is required for Streptococcus suis to deliver diverse cell wall anchoring effectors contributing to bacterial pathogenicity.

The Streptococcus suis serotype 2 (SS2) is a significant zoonotic pathogen that is responsible for various swine diseases, even causing cytokine storms of Streptococcal toxic shock-like syndromes amongst human. Cell wall anchoring proteins with a C-terminal LPxTG are considered to play vital roles during SS2 infection; however, their exporting mechanism across cytoplasmic membranes has remained vague. This study found that YSIRK-G/S was involved in the exportation of LPxTG-anchoring virulence factors MRP and SspA in virulent SS2 strain ZY05719. The whole-genome analysis indicated that diverse LPxTG proteins fused with an N-terminal YSIRK-G/S motif are encoded in strain ZY05719. Two novel LPxTG proteins SspB and YzpA were verified to be exported via a putative transport system that was dependent on the YSIRK-G/S directed translocation, and portrayed vital functions during the infection of SS2 strain ZY05719. Instead of exhibiting an inactivation of C5a peptidase in SspB, another LPxTG protein with an N-terminal YSIRK-G/S motif from Streptococcus agalactiae was depicted to cleave the C5a component of the host complement. The consequent domain-architecture retrieval determined more than 10,000 SspB/YzpA like proteins that are extensively distributed in the Gram-positive bacteria, and most of them harbor diverse glycosyl hydrolase or peptidase domains within their middle regions, thus presenting their capability to interact with host cells. The said findings provide compelling evidence that LPxTG proteins with an N-terminal YSIRK-G/S motif are polymorphic effectors secreted by Gram-positive bacteria, which can be further proposed to define as cell wall anchoring effectors in a new subset.

Multiple Salmonella-pathogenicity island 2 effectors are required to facilitate bacterial establishment of its intracellular niche and virulence.

The pathogenesis of Salmonella Typhimurium depends on the bacterium's ability to survive and replicate within host cells. The formation and maintenance of a unique membrane-bound compartment, termed the Salmonella-containing vacuole (SCV), is essential for S. Typhimurium pathogenesis. SCV-bound S. Typhimurium induces formation of filamentous tubules that radiate outwards from the SCV, termed Salmonella-induced filaments (SIFs). SIF formation is concomitant with the onset of replication within host epithelial cells. SIF biogenesis, formation and maintenance of the SCV, and the intracellular positioning of the SCV within the host cell requires translocation of bacterial proteins (effectors) into the host cell. Effectors secreted by the type III secretion system encoded on Salmonella pathogenicity island 2 (T3SS2) function to interfere with host cellular processes and promote both intracellular survival and replication of S. Typhimurium. Seven T3SS2-secreted effectors, SifA, SopD2, PipB2, SteA, SseJ, SseF, and SseG have previously been implicated to play complementary, redundant, and/or antagonistic roles with respect to SIF biogenesis, intracellular positioning of the SCV, and SCV membrane dynamics modulation during infection. We undertook a systematic study to delineate the contribution of each effector to these processes by (i) deleting all seven of these effectors in a single S. Typhimurium strain; and (ii) deleting combinations of multiple effectors based on putative effector function. Using this deletion mutant library, we show that each of SIF biogenesis, intracellular SCV localization, intramacrophage replication, colonization, and virulence depends on the activities of multiple effectors. Together, our data demonstrates the complex interplay between these seven effectors and highlights the necessity to study T3SS2-secreted effectors as groups, rather than studies of individual effectors.

Transcriptome analysis of human brain microvascular endothelial cells response to Neisseria meningitidis and its antigen MafA using RNA-seq.

Interaction of Neisseria meningitidis (NM) with human brain microvascular endothelial cells (hBMECs) initiates of multiple cellular processes, which allow bacterial translocation across the blood-brain barrier (BBB). NM is equipped with several antigens, which interacts with the host cell receptors. Recently we have shown that adhesin MafA (UniProtKB-X5EG71), relatively less studied protein, is one of those surface exposed antigens that adhere to hBMECs. The present study was designed to comprehensively map the undergoing biological processes in hBMECs challenged with NM or MafA using RNA sequencing. 708 and 726 differentially expressed genes (DEGs) were identified in hBMECs exposed to NM and MafA, respectively. Gene ontology analysis of the DEGs revealed that several biological processes, which may alter the permeability of BBB, were activated. Comparative analysis of DEGs revealed that MafA, alike NM, might provoke TLR-dependent pathway and augment cytokine response. Moreover, both MafA and NM were able to induce genes involved in cell surface modifications, endocytosis, extracellular matrix remodulation and anoikis/apoptosis. In conclusion, this study for the first time describes effect of NM on the global gene expression in hBMECs using high-throughput RNA-seq. It also presents ability of MafA to induce gene expression, which might aid NM in breaching the BBB.

Intestinal IL-17R Signaling Constrains IL-18-Driven Liver Inflammation by the Regulation of Microbiome-Derived Products.

Interleukin (IL)-17 signaling to the intestinal epithelium regulates the intestinal microbiome. Given the reported links between intestinal dysbiosis, bacterial translocation, and liver disease, we hypothesize that intestinal IL-17R signaling plays a critical role in mitigating hepatic inflammation. To test this, we study intestinal epithelium-specific IL-17RA-deficient mice in an immune-driven hepatitis model. At the naive state, these mice exhibit microbiome dysbiosis and increased translocation of bacterial products (CpG DNA), which drives liver IL-18 production. Upon disease induction, absence of enteric IL-17RA signaling exacerbates hepatitis and hepatocyte cell death. IL-18 is necessary for disease exacerbation and is associated with increased activated hepatic lymphocytes based on Ifng and Fasl expression. Thus, intestinal IL-17R regulates translocation of TLR9 ligands and constrains susceptibility to hepatitis. These data connect enteric Th17 signaling and the microbiome in hepatitis, with broader implications on the effects of impaired intestinal immunity and subsequent release of microbial products observed in other extra-intestinal pathologies.

Leaky gut biomarkers in depression and suicidal behavior.

OBJECTIVE: Inflammation is associated with major depressive disorder (MDD) and suicidal behavior. According to the 'leaky gut hypothesis', increased intestinal permeability may contribute to this relationship via bacterial translocation across enterocytes. We measured plasma levels of gut permeability markers, in patients with a recent suicide attempt (rSA), MDD subjects with no history of a suicide attempt (nsMDD), and healthy controls (HC), and related these markers to symptom severity and inflammation. METHOD: We enrolled rSA (n = 54), nsMDD (n = 13), and HC (n = 17). Zonulin, intestinal fatty acid binding protein (I-FABP), soluble CD14, and interleukin-6 (IL-6) were quantified in plasma. Montgomery-Åsberg Depression Rating Scale (MADRS) and Suicide Assessment Scale (SUAS) were used for symptom assessments. RESULTS: The rSA group displayed higher I-FABP and lower zonulin levels compared with both the nsMDD and the HC groups (all P < 0.001). IL-6 correlated positively with I-FABP (r = 0.24, P < 0.05) and negatively with zonulin (r = -0.25, P < 0.05). In all subjects, I-FABP levels correlated positively with MADRS (r = 0.25, P < 0.05) and SUAS scores (r = 0.38, P < 0.001), and the latter correlation was significant also in the nsMDD group (r = 0.60, P < 0.05). CONCLUSION: The 'leaky gut hypothesis' may improve our understanding of the link between inflammation and suicidal behavior. These findings should be considered preliminary until replicated in larger cohorts.

Microbial Translocation Does Not Drive Immune Activation in Ugandan Children Infected With HIV.

Objective: Immune activation is associated with morbidity and mortality during human immunodeficiency virus (HIV) infection, despite receipt of antiretroviral therapy (ART). We investigated whether microbial translocation drives immune activation in HIV-infected Ugandan children. Methods: Nineteen markers of immune activation and inflammation were measured over 96 weeks in HIV-infected Ugandan children in the CHAPAS-3 Trial and HIV-uninfected age-matched controls. Microbial translocation was assessed using molecular techniques, including next-generation sequencing. Results: Of 249 children included, 142 were infected with HIV; of these, 120 were ART naive, with a median age of 2.8 years (interquartile range [IQR], 1.7-4.0 years) and a median baseline CD4+ T-cell percentage of 20% (IQR, 14%-24%), and 22 were ART experienced, with a median age of 6.5 years (IQR, 5.9-9.2 years) and a median baseline CD4+ T-cell percentage of 35% (IQR, 31%-39%). The control group comprised 107 children without HIV infection. The median increase in the CD4+ T-cell percentage was 17 percentage points (IQR, 12-22 percentage points) at week 96 among ART-naive children, and the viral load was <100 copies/mL in 76% of ART-naive children and 91% of ART-experienced children. Immune activation decreased with ART use. Children could be divided on the basis of immune activation markers into the following 3 clusters: in cluster 1, the majority of children were HIV uninfected; cluster 2 comprised a mix of HIV-uninfected children and HIV-infected ART-naive or ART-experienced children; and in cluster 3, the majority were ART naive. Immune activation was low in cluster 1, decreased in cluster 3, and persisted in cluster 2. Blood microbial DNA levels were negative or very low across groups, with no difference between clusters except for Enterobacteriaceae organisms (the level was higher in cluster 1; P < .0001). Conclusion: Immune activation decreased with ART use, with marker clustering indicating different activation patterns according to HIV and ART status. Levels of bacterial DNA in blood were low regardless of HIV status, ART status, and immune activation status. Microbial translocation did not drive immune activation in this setting. Clinical Trials Registration: ISRCTN69078957.

Intestinal epithelial cell-specific IGF1 promotes the expansion of intestinal stem cells during epithelial regeneration and functions on the intestinal immune homeostasis.

It is well known that insulin-like growth factor 1 (IGF1) acts as a trophic factor in small intestine under both physiological and pathophysiological conditions. However, it still lacks direct in vivo evidence of the functions of intestinal epithelial cell (IEC)-specific IGF1 under both normal and pathological conditions. Using IEC-specific IGF1-knockout (cKO) mice and Lgr5-eGFP-CreERT mice, we demonstrate that IEC-specific IGF1 can enhance nutrient uptake, reduce protein catabolism and energy consumption, and promote the proliferation and expansion of intestinal epithelial cells, including intestinal epithelial stem cells and intestinal secretory cells. Next, we showed that IEC-specific IGF1 renders IECs resistant to irradiation and promotes epithelial regeneration. Strikingly, transcriptome profiling assay revealed that many differentially expressed genes involved in the differentiation and maturation of lymphoid lineages were significantly suppressed in the cKO mice as compared with the control mice. We demonstrated that deletion of IGF1 in IECs enhances bacterial translocation to the mesenteric lymph nodes and liver. Furthermore, high-throughput sequencing of 16S ribosomal RNA genes of gut microbiota revealed that IEC-specific IGF1 loss profoundly affected the gut microbial composition at various levels of classification. Therefore, our findings shed light on the in vivo roles of IEC-specific IGF1 in intestinal homeostasis, epithelial regeneration, and immunity, broadening our current insights on IGF1 functions.

Elevated systemic microbial translocation in pregnant HIV-infected women compared to HIV-uninfected women, and its inverse correlations with plasma progesterone levels.

In HIV infection, increased adverse perinatal outcomes reported among HIV-associated pregnancies are not fully understood. Currently, microbial product translocation (MT) from a permeable mucosa is demonstrated as a driver of inflammation, and may contribute to preterm delivery in HIV. Here, our results showed that plasma LPS levels (a representative marker of MT) were increased in HIV-infected women in the first and second trimester. Progesterone levels were significantly decreased in HIV-infected subjects in the first trimester and second trimester. There were significant inverse correlations between plasma LPS and progesterone in the first and second trimester. These results suggested heightened systemic MT and decreased plasma progesterone levels in HIV-infected pregnant women may play a role in increased incidence of preterm delivery.

An RNA-dependent mechanism for transient expression of bacterial translocation filaments.

The prokaryotic RNA chaperone Hfq mediates sRNA-mRNA interactions and plays a significant role in post-transcriptional regulation of the type III secretion (T3S) system produced by a range of Escherichia coli pathotypes. UV-crosslinking was used to map Hfq-binding under conditions that promote T3S and multiple interactions were identified within polycistronic transcripts produced from the locus of enterocyte effacement (LEE) that encodes the T3S system. The majority of Hfq binding was within the LEE5 and LEE4 operons, the latter encoding the translocon apparatus (SepL-EspADB) that is positively regulated by the RNA binding protein, CsrA. Using the identified Hfq-binding sites and a series of sRNA deletions, the sRNA Spot42 was shown to directly repress translation of LEE4 at the sepL 5' UTR. In silico and in vivo analyses of the sepL mRNA secondary structure combined with expression studies of truncates indicated that the unbound sepL mRNA is translationally inactive. Based on expression studies with site-directed mutants, an OFF-ON-OFF toggle model is proposed that results in transient translation of SepL and EspA filament assembly. Under this model, the nascent mRNA is translationally off, before being activated by CsrA, and then repressed by Hfq and Spot42.

Lysogenisation of Shiga toxin-encoding bacteriophage represses cell motility.

Bacteriophages are genetic elements that play key roles in the evolution and diversification of bacterial genomes. The Shiga toxin (Stx)-encoding phage plays an important role in the horizontal transfer of the stx gene. However, the influence of the Stx phage integration on the physiological properties and gene expression pattern of the host have not been clearly resolved. In this study, we constructed the Sp5 lysogen through lysogenisation of E. coli K-12 by Sp5, an Stx2 phage in enterohaemorrhagic E. coli (EHEC) O157:H7 Sakai, and examined the effect of the resulting lysogen on cell motility under various growth conditions. Sp5 lysogenisation decreased cell motility and the expression of fliC, which encodes flagellin, under anaerobic conditions at 37°C. Sp5 also lowered the expression of fliA, which encodes the FliA-sigma factor responsible for the transcription of fliC, and flhD, which facilitates the expression of fliA. Sp5 lysogenisation reduced the amount of FlhD and FlhC expressed from the araBAD promoter, suggesting that one or more genes present in Sp5 represses flhDC at the post-transcriptional level. Flagellin is highly antigenic and triggers an immune response in the host. Thus, Sp5 might enhance its viability by repressing the expression of the flagellar regulon to circumvent the immune response of host cells.

Gut-liver axis, cirrhosis and portal hypertension: the chicken and the egg.

The term gut-liver axis is used to highlight the close anatomical and functional relationship between the intestine and the liver. The intestine has a highly specialized epithelial membrane which regulates transport across the mucosa. Due to dysbiosis, impairment of the intestinal barrier and altered immunity status, bacterial products can reach the liver through the portal vein, where they are recognized by specific receptors, activate the immune system and lead to a proinflammatory response. Gut microbiota and bacterial translocation play an important role in the pathogenesis of chronic liver diseases, including alcoholic and non-alcoholic fatty liver disease, cirrhosis, and its complications, such as portal hypertension, spontaneous bacterial peritonitis and hepatic encephalopaty. The gut microbiota also plays a critical role as a modulator of bile acid metabolism which can also influence intestinal permeability and portal hypertension through the farnesoid-X receptor. On the other hand, cirrhosis and portal hypertension affect the microbiota and increase translocation, leading to a "chicken and egg" situation, where translocation increases portal pressure, and vice versa. A myriad of therapies targeting gut microbiota have been evaluated specifically in patients with chronic liver disease. Further studies targeting intestinal microbiota and its possible hemodynamic and metabolic effects are needed. This review summarizes the current knowledge about the role of gut microbiota in the pathogenesis of chronic liver diseases and portal hypertension.

Role for FimH in Extraintestinal Pathogenic Escherichia coli Invasion and Translocation through the Intestinal Epithelium.

The translocation of bacteria across the intestinal epithelium of immunocompromised patients can lead to bacteremia and life-threatening sepsis. Extraintestinal pathogenic Escherichia coli (ExPEC), so named because this pathotype infects tissues distal to the intestinal tract, is a frequent cause of such infections, is often multidrug resistant, and chronically colonizes a sizable portion of the healthy population. Although several virulence factors and their roles in pathogenesis are well described for ExPEC strains that cause urinary tract infections and meningitis, they have not been linked to translocation through intestinal barriers, a fundamentally distant yet important clinical phenomenon. Using untransformed ex situ human intestinal enteroids and transformed Caco-2 cells, we report that ExPEC strain CP9 binds to and invades the intestinal epithelium. ExPEC harboring a deletion of the gene encoding the mannose-binding type 1 pilus tip protein FimH demonstrated reduced binding and invasion compared to strains lacking known E. coli virulence factors. Furthermore, in a murine model of chemotherapy-induced translocation, ExPEC lacking fimH colonized at levels comparable to that of the wild type but demonstrated a statistically significant reduction in translocation to the kidneys, spleen, and lungs. Collectively, this study indicates that FimH is important for ExPEC translocation, suggesting that the type 1 pilus is a therapeutic target for the prevention of this process. Our study also highlights the use of human intestinal enteroids in the study of enteric diseases.

Streptococcus pyogenes translocates across an epithelial barrier.

Streptococcus pyogenes is a ß-hemolytic organism responsible for a wide variety of human diseases that commonly occur as self-limiting purulent diseases of the pharynx and skin. Although the occurrence of invasive infections by S. pyogenes is rare, mortality rates remain high even with progressive medical therapy. As a prerequisite for causing the severe invasive disease, S. pyogenes must invade underlying sterile tissues by translocating across the epithelial barrier. In this study, streptolysin S and SpeB were identified as the novel factors that facilitate bacterial translocation via degradation of intercellular junctions. Furthermore, we found that S. pyogenes exploits host plasminogen for acceleration of bacterial invasion into deeper tissues via tricellular tight junctions. Here, I would like to show our study on bacterial translocation across the epithelial barrier through paracellular route.

Cysteine Protease-Dependent Mucous Disruptions and Differential Mucin Gene Expression in Giardia duodenalis Infection.

The intestinal mucous layer provides a critical host defense against pathogen exposure and epithelial injury, yet little is known about how enteropathogens may circumvent this physiologic barrier. Giardia duodenalis is a small intestinal parasite responsible for diarrheal disease and chronic postinfectious illness. This study reveals a complex interaction at the surface of epithelial cells, between G. duodenalis and the intestinal mucous layer. Here, we reveal mechanisms whereby G. duodenalis evades and disrupts the first line of host defense by degrading human mucin-2 (MUC2), depleting mucin stores and inducing differential gene expression in the mouse small and large intestines. Human colonic biopsy specimens exposed to G. duodenalis were depleted of mucus, and in vivo mice infected with G. duodenalis had a thinner mucous layer and demonstrated differential Muc2 and Muc5ac mucin gene expression. Infection in Muc2-/- mice elevated trophozoite colonization in the small intestine and impaired weight gain. In vitro, human LS174T goblet-like cells were depleted of mucus and had elevated levels of MUC2 mRNA expression after G. duodenalis exposure. Importantly, the cysteine protease inhibitor E64 prevented mucous degradation, mucin depletion, and the increase in MUC2 expression. This article describes a novel role for Giardia's cysteine proteases in pathogenesis and how Giardia's disruptions of the mucous barrier facilitate bacterial translocation that may contribute to the onset and propagation of disease.

Editor's Highlight: OrganophosphateDiazinon Altered Quorum Sensing, Cell Motility, Stress Response, and Carbohydrate Metabolism of Gut Microbiome.

The gut microbiome plays a key role in energy production, immune system development, and host resistance against invading pathogens, etc. Disruption of gut bacterial homeostasis is associated with a number of human diseases. Several environmental chemicals have been reported to induce alterations of the gut microbiome. Diazinon, one of important organophosphate insecticides, has been widely used in agriculture. Diazinon and its metabolites are readily detected in different environmental settings and human urine. The toxicity of organophosphates has been a long-standing public health concern. We recently demonstrated that organophosphate insecticide diazinon perturbed the gut microbiome composition of mice. However, the functional impact of exposure on the gut microbiome has not been adequately assessed yet. In particular, the molecular mechanism responsible for exposure-induced microbial profile and community structure changes has not been identified. Therefore, in this study, we used metatranscriptomics to examine the effects of diazinon exposure on the gut metatranscriptome in C57BL/6 mice. Herein, we demonstrated for the first time that organophosphate diazinon modulated quorum sensing, which may serve as a key mechanism to regulate bacterial population, composition, and more importantly, their functional genes. In addition, we also found that diazinon exposure activated diverse stress response pathways and profoundly impaired energy metabolism of gut bacteria. These findings provide new understandings of the functional interplay between the gut microbiome and environmental chemicals, such as organophosphates.