Citrobacter Rodentium Research Articles (Page 1)

The natural context in which CRISPR-Cas systems are active in Enterobacteriaceae has remained enigmatic. Here we find that the Citrobacter rodentium type I-E CRISPR-Cas system is activated by the oxygen-responsive transcriptional regulator Fnr in the anoxic environment of the mouse intestine. Since Fnr-dependent regulation is predicted in ~41% of Enterobacteriaceae cas3 orthologues, we propose that anoxic regulation of CRISPR-Cas immunity is an adaptation that protects Enterobacteriaceae against threats from foreign DNA within the intestinal microbiome.

Diverse pathogen-encoded virulence factors disable apoptosis, pyroptosis or necroptosis, the host cell death programs that remove infected cells1. In the intestine, the extrusion of infected cells into the lumen for elimination provides an additional layer of host defence, but no virulence mechanisms that target the cytoskeletal changes requiredare known2. Here we show that the Escherichia coli ubiquitin ligase NleL is an inhibitor of intestinal epithelial cell (IEC) extrusion, targeting caspase-4, ROCK1 and ROCK2 for proteasomal degradation. Genetic deletion of Rock1 and Rock2 from cultured IECs diminished inflammasome-induced IEC extrusion. Moreover, mice with Rock1- and Rock2-deficient IECs were less effective than wild-type mice at constraining the numbers of Citrobacter rodentium in the colon. Notably, NleL-deficient C. rodentium triggered more IEC extrusion than did wild-type C. rodentium, resulting in diminished colonization of the colon in infected mice. Our work highlights a host-pathogen arms race focused on dynamic regulation of the host epithelial barrier.

Here, we report the identification of bacteriophage Mu contamination in a commonly used Citrobacter rodentium DBS100 ∆cpxRA mutant strain. After re-constructing a new Mu-free ∆cpxRA strain, we independently replicated the results of a recent study by A. Gilliland, C. Gavino, S. Gruenheid, and T. Raivio (Infect Immun 90:e00314-22, 2022, https://doi.org/10.1128/iai.00314-22). The only result from Gilliland et al. that was impacted by the presence of Mu was the outcome of interbacterial competition assays with the ∆cpxRA strain, as strains carrying Mu consistently outcompeted susceptible Mu-free competitors. These results are important for the field, as the contaminated DBS100 ∆cpxRA mutant strain has been used in six different studies. We believe that the Mu contamination occurred during the construction of the ∆cpxRA allele, during the conjugation of DBS100 with a popular Mu-containing donor strain. Our results highlight the importance of using Mu-free conjugal donor strains and how phage contamination can impact bacterial physiology and experimental results.

Existing technologies employed to generate antibodies against bacterial polysaccharides and proteins rely on the availability of purified or synthetic antigens. Here, we present a genetics-based platform that utilises Citrobacter rodentium (CR), an enteric mouse pathogen, to both produce and present complex heterologous polysaccharides and protein antigen complexes during natural infection. As proof of concept, we use lipopolysaccharides (O), capsular polysaccharides (K) and type 3 fimbrial (T3F) antigens expressed by the WHO critical priority pathogens Klebsiella pneumoniae (KP) and Escherichia coli (EC). Following one infection cycle (28 days), CR induces specific IgG antibodies against KPO1, ECO25b, KPK2 and KPT3F. We demonstrate that the antibodies are functional in downstream applications, including protection against pathogenic KP challenge, KP capsular serotyping and KP biofilm inhibition. Whilst KP and EC antigens were used as prototypical examples, this modular platform is now readily adaptable to generate antibodies against diverse polysaccharide and protein antigens, with basic science, public health and therapeutic applications.

Acsbg1 maintains intestinal immune homeostasis and controls inflammation by regulating ST2+ Tregs.

The sympathetic nervous system enhances host immune responses to enteric bacterial pathogens in mice.

The IFNγ-induced GTPase guanylate binding protein 1 (GBP1) binds to lipopolysaccharide (LPS) on cytosolic Gram-negative bacteria and promotes pyroptosis via the recruitment and activation of caspase-4 on the bacterial outer membrane. Enteropathogenic and enterohaemorrhagic Escherichia coli (EPEC and EHEC, respectively) are extracellular pathogens that also induce LPS- and caspase-4-dependent pyroptosis. However, whether GBP1 is involved in this process remains unknown. EPEC and EHEC adhere intimately to intestinal epithelial cells via avid interactions between the bacterial adhesin Intimin and Tir (Translocated intimin receptor), a type 3 secretion system effector protein. Intimin-mediated clustering of Tir triggers actin polymerisation, leading to pedestal-like structures at bacterial attachment sites. Here we show that GBP1 is recruited to actin pedestals in human cells infected with EPEC and EHEC in vitro and mouse colonocytes infected with the EPEC-like murine pathogen Citrobacter rodentium in vivo. GBP1-dependent caspase-4 trafficking to these sites leads to pyroptosis and IL-18 release. To dissect the mechanism of GBP1 trafficking, we engineered a chimeric receptor (FcγR-Tir) by combining the intracellular signalling domain of Tir and the extracellular ligand-binding domain of the Fcγ receptor. Clustering of FcγR-Tir with IgG-coated beads produced ‘sterile’ actin-rich pedestals that were sufficient to recruit GBP1 independently of bacteria. Our findings reveal that cytosolic GBP1 is mobilised to sites of pathogen-induced actin remodelling independently of LPS. We establish that GBP1 not only operates as a pattern-recognition receptor but also orchestrates effector-triggered immunity against pathogens that hijack the actin cytoskeleton.

Aim: This study aimed to screen Lactococcus lactis strains with varying gamma-aminobutyric acid (GABA) production and evaluate their effects on intestinal dysfunction and neurobehavioral abnormalities in an irritable bowel syndrome (IBS) mouse model, with a focus on GABAergic signaling and dose-dependent mechanisms.Methods: Three Lactococcus lactis strains were selected based on GABA yield and genetic analysis. IBS was induced in mice via Citrobacter rodentium infection and water avoidance stress. Intestinal integrity, inflammation, histopathology, and behavior were assessed. GABA levels in the colon and serum were measured by liquid chromatography-mass spectrometry (LC-MS). GABA receptor subunit expression in the colon, hippocampus, and amygdala was analyzed via quantitative real-time polymerase chain reaction and Western blotting.Results: GABA-producing strains alleviated intestinal dysfunction in IBS mice by reducing IL-6 gene expression and iNOS activity, upregulating CLDN2, and improving tissue integrity. Anxiety-like behaviors and cognitive deficits were also attenuated. Colonic GABA levels, GABRA13 mRNA, and GABRA3 protein expression increased in a dose-dependent manner, whereas TRPV1 mRNA and TRPV1 protein levels were downregulated. Serum GABA remained unchanged. In the central nervous system, the expression of hippocampal GABAA and GABAB receptors was elevated, with both GABRA13 mRNA and GABRA3 protein levels positively correlating with colonic GABA concentrations. GABRA15 expression was upregulated in the amygdala.Conclusion: GABA-producing Lactococcus lactis effectively alleviates IBS-related intestinal dysfunction and neurobehavioral abnormalities by coordinately modulating GABAergic signaling in both the gut and the central nervous system, exhibiting a clear dose-dependent effect across multiple key phenotypes.

Obesity and diabetes are interlinked diseases, but it was unclear how obesity vs. diabetes modifies the risk and severity of gut bacterial infection. We aimed to determine how obesity or hyperglycemia, indicative of diabetes, altered metabolic endotoxemia and severity of enteric infection. Metabolic endotoxemia was determined using TLR4 activity reporter assay in serum from humans with obesity or diabetes, and from hyperglycemic Akita+/- mice and genetically obese ob/ob mice. Diarrhea severity during Escherichia coli infection was determined in humans during a previous community outbreak. The enteropathogen Citrobacter rodentium was used to define the mechanisms of action that altered the severity of enteric infection in ob/ob and Akita+/- mice. We found that elevated blood glucose, indicative of diabetes, was associated with increased occurrence and severity of diarrhea during an E. coli outbreak in humans. Metabolic endotoxemia occurred in a separate cohort of people with obesity who were normoglycemic or hyperglycemic, and in mice with either obesity or hyperglycemia. Hyperglycemia, not obesity, increased mortality during infection with the diarrhea-causing pathogen C. rodentium in mouse models of type 1 and type 2 diabetes. Common indicators of poor prognosis, such as gut pathology, systemic bacteraemia, or metabolic endotoxemia, did not predict worse outcomes during enteric infection in diabetic mice. Hyperglycemia activated intestinal Wnt/β-catenin and increased mortality, which could be reversed by blocking Wnt/β-catenin, lowering blood glucose, or restoring fluid balance during infection. The increased severity of infection via overactivation of intestinal Wnt/β-catenin during hyperglycemia may be a potential target for therapeutics.NEW & NOTEWORTHY We show that elevated blood glucose is associated with worse diarrhea during an Escherichia coli outbreak in humans. Obesity or hyperglycemia was sufficient to promote metabolic endotoxemia in humans and mice. Hyperglycemia promotes worse enteric infection outcomes independent of obesity. Finally, we showed that blocking of Wnt/β-catenin, lowering blood glucose, or restoring fluids improved enteric infection outcomes in hyperglycemic mice.

Parkinson’s Disease (PD) is a neurodegenerative disorder often preceded by gastrointestinal dysfunction. Mutations in leucine-rich repeat kinase 2 (LRRK2) are known risk factors for both PD and inflammatory bowel disease (IBD), suggesting a link between PD and the gastrointestinal tract. Using single-cell RNA-sequencing and spectral flow cytometry, we demonstrated that the Lrrk2 Gly2019Ser (G2019S) mutation is associated with an increased neutrophil presence in the colonic lamina propria during Citrobacter rodentium infection. This concurred with a Th17 skewing, upregulated Il17a, and greater colonic pathology during infection. In vitro experiments showed enhanced kinase-dependent neutrophil chemotaxis and neutrophil extracellular trap (NET) formation in Lrrk2 G2019S mice compared to wild-type counterparts. Our results add to the understanding of LRRK2-driven immune cell dysregulation and its contribution to PD, offering insights into potential biomarkers for early diagnosis and intervention in PD.

There is a wealth of signals present in the human gut that mediate host-microbiota communication and intersect with the gut-brain-axis. There is differential spatial localization of the tryptophan derivatives serotonin and indole in the gut, which are important cues for enteric pathogens to find their colonization niche. Both signals are sensed by enteric pathogens such as enterohemorrhagic Escherichia coli (EHEC) and Citrobacter rodentium, a murine pathogen extensively employed as a surrogate animal model for EHEC. EHEC and C. rodentium virulence determinants include genes necessary for the attaching and effacing (AE) lesion formation on enterocytes, which are contained within the locus of enterocyte effacement (LEE) pathogenicity island. Both signals inhibit LEE expression in vitro and during mammalian infection. The roles of indole and serotonin in virulence have been initially interrogated separately. Here, we show the combinatorial effect of these signals antagonizing each other's activity on bacterial virulence in vitro and during murine infection. The role of both signals in vivo was interrogated by manipulating the serotonin levels in mice through pharmacological and genetic strategies to increase the levels of serotonin in the gut by inhibiting the serotonin reuptake transporter (SERT). Simultaneously, indole levels were altered through infection with C. rodentium strains that either produce or don't indole or recolonizing the microbiota with WT or ΔtnaA (does not produce indole) strains of Bacteroides thetaiotaomicron. Individually increasing the levels of serotonin and indole in the gut decreased C. rodentium pathogenesis. However, when both signals were elevated simultaneously, they antagonized each other's activity.IMPORTANCEPathogens sense a plethora of signals within the gut to successfully establish colonization by precise regulation of virulence gene expression within the right niche. Our study shows that it is crucial to not disregard the interaction of different signaling mechanisms to understand the complexity of virulence regulation in enteric pathogens. Even though serotonin and indole are both tryptophan derivatives with similar structures that individually decrease bacterial virulence, combinatorial sensing of these two signals cancels out each other's effect. Understanding these sensing mechanisms provides a better insight into potential therapeutic approaches against enteric infections.

Background and AimsThe Doublecortin-like kinase-1 (DCLK1) plays a chemosensory role in the gut. It’s role in the context of inflammatory diseases including inflammatory bowel disease (IBD), has not been thoroughly investigated. This study explored the role of the DCLK1 isoform (DCLK1-S) in promoting infectious/chemical colitis by utilizing high-throughput imaging mass cytometry (IMC).MethodsTransgenic mice were either infected with Citrobacter rodentium (CR) or received DSS and tissues/cells were processed via standard techniques. IMC workflow was adapted by Fluidigm (renamed Standard BioTools). Raw data was fed to Multiplexed Cell Dataset (MCD) Viewer for image generation and analyzed via histoCAT. Promoters for DCLK1 long (DCLK1-L) and short (DCLK1-S) transcripts were cloned, and promoter activities were determined via luciferase reporter assays.ResultsFollowing CR-induced infectious colitis in mice, IMC revealed accumulation of DCLK1-S in the colons of infected mice that inversely correlated with DCLK1-S repressor FoxD3 (Forkhead Box D3). Elevated DCLK1-S levels corresponded with MMP13 staining and activity, promoting collagen degradation and fibrosis. We confirmed the DCLK1-S/MMP13 axis in a knock- in mouse model overexpressing DCLK1-S, in conjunction with dextran sulfate sodium (DSS)- induced colitis. During DCLK1-L and DCLK1-S promoter-reporter assays, we observed a more dramatic decrease in DCLK1-S reporter activity in response to either MMP13 inhibitor, WAY- 170523 or DCLK1 inhibitor, DCLK1-IN-1 compared to the effect of these inhibitors on DCLK1-L promoter. Furthermore, we identified epithelial-to-mesenchymal transition (EMT) as a prelude to colitis.ConclusionsPersistent expression of DCLK1-S drives a severe inflammatory phenotype, contributing to extracellular matrix (ECM) remodeling, fibrosis, and EMT, thus playing pivotal roles in colitis pathogenesis and presenting potential avenues for novel treatment strategies.

The interleukin-1 receptor (IL-1R) plays an important role in mediating the inflammatory responses against pathogens. However, it is not clear whether a sustained IL-1R signaling following the loss of its endogenous inhibitor, IL-1R antagonist (IL-1RA), could improve mucosal immunity against the murine enteropathogen, Citrobacter rodentium. At basal levels, IL-1RA–deficient (IL1raKO) mice displayed an elevated inflammatory tone as indicated by their higher levels of circulating neutrophils, and the inflammatory marker, lipocalin-2, in both systemic and luminal contents. We reasoned that the heightened inflammatory tone of IL1raKO mice may be beneficial in clearing C. rodentium efficiently, but such was not the case. Oral challenge of C. rodentium (1 × 109 colony-forming units/mouse) resulted in luminal colonization, which peaked at day 7 postinfection, in both wild-type and IL1raKO mice. However, IL1raKO mice displayed a higher C. rodentium burden, and exacerbated colonic inflammation and hyperplasia. The aggravated infection in IL1raKO mice was corroborated using in vivo imaging of mice infected with a bioluminescent strain of C. rodentium. However, IL1raKO mice do not display any defect in their neutrophils with respect to their recruitment to the inflamed gut, generation of neutrophil extracellular traps and reactive oxygen species, or their ability to kill C. rodentium in vitro. In contrast, the macrophages of IL1raKO mice were able to upregulate more inducible nitric oxide synthase and produce more nitrite that wild-type macrophages; however, the former was less effective in mediating killing of C. rodentium in vitro. Together, our results suggest that IL-1RA plays a protective role in combating enteropathogen infection.

The gut experiences daily fluctuations in microbes and nutrients aligned with circadian rhythms that regulate nutrient absorption and immune function. Group 3 innate lymphoid cells (ILC3s) support gut homeostasis through interleukin-22 (IL-22) but can convert into interferon-γ-producing ILC1s. How circadian proteins control this plasticity remains unclear. Here we showed that the circadian proteins REV-ERBα and REV-ERBβ maintain ILC3 identity. Their combined deletion promoted ILC3-to-ILC1 conversion, reduced energy metabolism and IL-22 production, increased interferon-γ production, and heightened susceptibility to Citrobacter rodentium infection. Single-cell multiomics and gene editing revealed that REV-ERBα/REV-ERBβ deficiency upregulated the transcription factor NFIL3, which repressed the expression of RORγt via a -2-kb cis-regulatory element in the Rorc gene, shifting cells toward a T-bet-driven state. Chromatin and metabolic analyses indicated that REV-ERBα/REV-ERBβ loss reprogrammed regulatory and metabolic circuits. Thus, REV-ERBα/REV-ERBβ safeguard gut integrity by regulating clock genes that control RORγt expression and preserve ILC3 identity and resistance to intestinal inflammation.

ABSTRACT Colonic goblet cells play a crucial role in mucosal defense by secreting Muc2 mucin and other proteins that entrap and expel enteropathogens. However, the role of innate effectors in the gut like cathelicidin peptides in regulating the mucus barrier during infections remains unclear. In this study, we used cathelicidin-deficient (Camp -/- ) littermates, colonoids, and human LS174T goblet-like cells to investigate how cathelicidin modulates goblet cell function and mucosal defense against attaching/effacing enteropathogen Citrobacter rodentium. We showed that increased fecal shedding and epithelial colonization by C. rodentium in Camp -/- littermates was accompanied by impaired mucus secretion and higher retention of mucin granules and trefoil factor 3 (Tff3) in bloated colonic goblet cells. Reduction in mucus secretion by goblet cells was accompanied by reduced reactive oxygen species (ROS) production during C. rodentium infection in Camp -/- as compared to Camp +/+ littermate controls. In LS174T goblet-like cells, human cathelicidin LL-37 stimulated the secretion of TFF3 and resistin-like molecule β (RELMβ) in a ROS-dependent manner. These findings reveal that cathelicidin regulates goblet cell mucus and mucus-associated protein secretion through a ROS-mediated mechanism critical for bacterial clearance and maintenance of gut homeostasis.

Attaching and effacing pathogens overcome colonisation resistance by competing with metabolically similar organisms for limited resources. Enterohaemorrhagic E. coli (EHEC) utilises the pathogenicity island-encoded Accessory ʟ-arabinose Uptake (Aau) transporter to effectively colonise the mouse gut, hypothesised to be achieved via an enhanced capacity to scavenge ʟ-arabinose. Aau is regulated exclusively in response to ʟ-arabinose, but it is unclear how this system specifically benefits EHEC in vivo. Here, we show that Aau displays a > 200-fold higher affinity for the monosaccharide D-ribulose, over ʟ-arabinose. EHEC cannot grow on D-ribulose as a sole carbon source and this sugar does not trigger aau transcription. However, Aau effectively transports D-ribulose into the cell only in the presence of ʟ-arabinose, where it feeds into the pentose phosphate pathway, after phosphorylation by the ʟ-ribulokinase AraB, thus providing EHEC a significant fitness advantage. EHEC has therefore evolved a mechanism of hijacking the canonical ʟ-arabinose utilisation machinery to promote D-ribulose utilisation in vivo. Furthermore, Citrobacter rodentium encodes an analogous system that exclusively transports D-ribulose and metabolises it via a dedicated D-ribulokinase. These unique mechanisms of D-ribulose utilisation suggest that convergent evolution has driven the ability of distinct pathogenic species to exploit this nutrient during invasion of the gut niche.

ABSTRACT Injection of effectors via a type III secretion system (T3SS) is an infection strategy shared by various Gram-negative bacterial pathogens, many infecting mucosal surfaces. While individual T3SS effectors are well characterized, their network-level organization and the distinction between core and accessory effectors remain incompletely understood. Here, by systematically dissecting the T3SS effector network of the enteric mouse pathogen Citrobacter rodentium (CR) we identified a subset of 12 accessory effectors that, while dispensable for colonization, significantly alter infection outcomes. A strain lacking the accessory effectors (CRM12) remained virulent in susceptible mouse hosts yet resulted in reduced epithelial barrier damage, inflammation, and immune cell infiltration in resistant mice. Deep proteomic analysis specifically targeting CR-attached colonic epithelial cells revealed that, despite lacking 39% of its effector repertoire, infection with CRM12 results in similar changes to global protein expression as seen in mice infected with the wild-type strain, though key regulators of barrier integrity were differentially expressed. Using a host with impaired barrier repair (Il22 −/− mice), we confirmed that accessory effectors collectively shape infection outcomes without significantly impacting virulence. This study refines the concept of core and accessory effectors, providing a basis for further studies into effector-driven host adaptation.

Group 3 innate lymphoid cells (ILC3s) play a major role in protecting against infection with the enteric mouse pathogen Citrobacter rodentium (CR) used to model infections with enteropathogenic and enterohaemorrhagic Escherichia coli. ILC3s-secreted IL-22 induces secretion of IL-18, antimicrobial peptides and nutritional immunity proteins as well as activation of tissue regeneration processes. While ILC2s have traditionally been associated with immune responses to helminth infection and allergic inflammation via the production of type 2 cytokines (e.g. IL-4, IL-5, IL-9 and IL-13), more recently they have been implicated in protection against Clostridium difficile and Helicobacter pylori infections. Here we show that colonic lamina propria ILC2s expand in response to CR infection and secrete IL-4, IL-5 and IL- 13, which are involved in maintenance of the intestinal barrier function, tissue repair and mucus secretion. When stimulated with IL-18, and IL-33 as a control, colonic ILC2s from uninfected mice secreted type 2 cytokines. Injection of IL-18 binding protein (IL18 BP), at 2- and 3-days post CR infection, blocked expansion of ILC2s in vivo. While ILC2s do not expand in CR-infected Il22-/- mice, injection of IL-18 into Il22-/- mice at 2- and 3-days post CR infection triggered ILC2s expansion. Importantly, injection of anti-IL-13, at 2- and 4-days post CR infection, diminished local secretion of IL-10 and IL-22. These data show that ILC2s are activated in response to infection with an enteric Gram-negative pathogen. Moreover, stimulation with IL-18 plays a role in ILC2s expansion and secretion of type 2 cytokines, which may participate in shaping the local immunological landscape.

Group 3 innate lymphoid cells (ILC3s) play a major role in protecting against infection with the enteric mouse pathogen Citrobacter rodentium (CR) used to model infections with enteropathogenic and enterohaemorrhagic Escherichia coli. ILC3s-secreted IL-22 induces secretion of IL-18, antimicrobial peptides and nutritional immunity proteins as well as activation of tissue regeneration processes. While ILC2s have traditionally been associated with immune responses to helminth infection and allergic inflammation via the production of type 2 cytokines (e.g. IL-4, IL-5, IL-9 and IL-13), more recently they have been implicated in protection against Clostridium difficile and Helicobacter pylori infections. Here we show that colonic lamina propria ILC2s expand in response to CR infection and secrete IL-4, IL-5 and IL- 13, which are involved in maintenance of the intestinal barrier function, tissue repair and mucus secretion. When stimulated with IL-18, and IL-33 as a control, colonic ILC2s from uninfected mice secreted type 2 cytokines. Injection of IL-18 binding protein (IL18 BP), at 2- and 3-days post CR infection, blocked expansion of ILC2s in vivo. While ILC2s do not expand in CR-infected Il22-/- mice, injection of IL-18 into Il22-/- mice at 2- and 3-days post CR infection triggered ILC2s expansion. Importantly, injection of anti-IL-13, at 2- and 4-days post CR infection, diminished local secretion of IL-10 and IL-22. These data show that ILC2s are activated in response to infection with an enteric Gram-negative pathogen. Moreover, stimulation with IL-18 plays a role in ILC2s expansion and secretion of type 2 cytokines, which may participate in shaping the local immunological landscape.

BackgroundInflammatory bowel disease (IBD) is a gastrointestinal inflammatory disorder characterized by disturbed interactions between gut microbiota and host immune response. Barley leaf (BL) is a traditional Chinese herb recorded to have health-promoting effects. However, little is known about the beneficial role of BL against enteric infection-induced intestinal inflammation. Here, we uncover that BL protects against Citrobacter rodentium (C. rodentium)-induced infectious colitis by improving host-microbiota interactions.MethodsC3H/HeN mice were fed a diet with/without BL and infected with C. rodentium. Transcriptome sequencing, anti-CD4 antibody treatment, and flow cytometry were conducted to investigate the mechanisms of T cell immune modulation. The intervention involved administering anti-CD4 antibody at 500 µg each time for three times before and during C. rodentium infection. Analysis of gut microbiota composition was performed by 16S rRNA gene sequencing on fecal samples. Fecal microbiota transplantation was conducted by administering microbiota from donor group to recipient group via oral gavage to investigate the role of intestinal microbiota in immune modulation.ResultsBL ameliorated the severity of C. rodentium-induced colitis, and this effect was linked to improved gut homeostasis and enhanced mucosal barrier function. BL enriched the pathways of T helper 1 (Th1)/Th2 and Th17 cell differentiation in the colon, suggesting the involvement of CD4+ T cells. Consistent with this, anti-CD4 antibody treatment abrogated the effect of BL and flow cytometry analysis revealed that BL mitigated C. rodentium-induced pro-inflammatory Th1 immune response. Moreover, the protective effect of BL was associated with alleviation of gut microbiota dysbiosis and increased abundance of Lactobacillus. Our in vivo studies further revealed that live Lactobacillus plantarum (L. plantarum) administration attenuated the pathogenic effects induced by C. rodentium infection, whereas heat-inactivated L. plantarum did not show the same results. Mechanistically, BL supplementation enriched L. plantarum, which subsequently released nanosized extracellular vesicles (EVs) that serve as a key mediator in alleviating C. rodentium-associated pathology and Th1 cell dysregulation.ConclusionsOur work thus provides evidence for utilizing BL and L. plantarum-derived EVs to manage enteric infection-associated IBD.