Interleukin‑22 regulates the homeostasis of the intestinal epithelium during inflammation

Recombinant Interleukin - 2 2 Immunotherapy Ameliorates Inflammation and Promotes the Release of Monoamine Neurotransmitters in the Gut-Brain Axis of Schistosoma mansoni-Infected Mice

Recombinant interleukin-22 (rIL-22) has been reported as a protective agent in murine models of diseases driven by epithelial injury. Parasites have a circadian rhythm and their sensitivity to a certain drug may vary during the day. Therefore, this work aimed to investigate the effect of rIL-22 administration at different times of the day on the inflammation, oxidative status, and neurotransmitter release in the gut-brain axis of the Schistosoma mansoni-infected mice. Sixty male BALB/c mice aged six weeks weighing 25-30 g were divided into a control group (injected intraperitoneally with PBS), mice infected with 80 ± 10 cercariae of S. mansoni (infected group) then injected intraperitoneally with PBS, and rIL-22 treated groups. rIL-22 was administrated intraperitoneally (400 ng/kg) either at the onset or offset of the light phase for 14 days. IL-22 administration reduced the levels of IL-1β, tumor necrosis factor-alpha (TNF-α), nuclear factor kappa beta (NF-κβ), and enhanced the production of IL-22 and IL-17. The treatment with IL-22 increased glutathione (GSH) and reduced malondialdehyde (MDA) and nitric oxide (NO) levels both in the ileum and brain. The B-cell lymphoma 2 (BCL2) protein level in the ileum was diminished after IL-22 administration. Brain-derived neurotrophic factor (BDNF) and neurotransmitter release (serotonin, 5HT, norepinephrine, NE, dopamine, DA, Glutamate, Glu, and -amino butyric acid, GABA) were improved by rIL-22. In conclusion, rIL-22 showed promising immunotherapy for inflammation, oxidative damage, and neuropathological signs associated with schistosomiasis. The efficacy of IL-22 increased significantly upon its administration at the time of light offset.

Undenatured type II collagen protects against collagen-induced arthritis by restoring gut-joint homeostasis and immunity

Oral administration of harmless antigens can induce suppression of reactive immune responses, a process that capitalises on the ability of the gastrointestinal tract to tolerate exposure to food and commensal microbiome without triggering inflammatory responses. Repeating exposure to type II collagen induces oral tolerance and inhibits induction of arthritis, a chronic inflammatory joint condition. Although some mechanisms underlying oral tolerance are described, how dysregulation of gut immune networks impacts on inflammation of distant tissues like the joints is unclear. We used undenatured type II collagen in a prophylactic regime -7.33 mg/kg three times/week- to describe the mechanisms associated with protective oral immune-therapy (OIT) in gut and joint during experimental Collagen-Induced Arthritis (CIA). OIT reduced disease incidence to 50%, with reduced expression of IL-17 and IL-22 in the joints of asymptomatic mice. Moreover, whilst the gut tissue of arthritic mice shows substantial damage and activation of tissue-specific immune networks, oral administration of undenatured type II collagen protects against gut pathology in all mice, symptomatic and asymptomatic, rewiring IL-17/IL-22 networks. Furthermore, gut fucosylation and microbiome composition were also modulated. These results corroborate the relevance of the gut-joint axis in arthritis, showing novel regulatory mechanisms linked to therapeutic OIT in joint disease.

IL-22 promotes occludin expression by activating autophagy and treats ulcerative colitis

IL-22 serves a protective function in the intestinal barrier. These protective properties of IL-22 may offer a potential treatment for ulcerative colitis (UC). However, the exact mechanisms of action remain unclear. Autophagy plays an important protective role in stabilizing the intestinal barrier. We aimed to explore the role of autophagy in the IL-22-mediated-protective effects in UC. Dextran sulfate sodium (DSS) was administrated via drinking water over 7 days to induce acute UC in BALB/c mice. Treatments with IL-22 (0.25 μg/10 g bodyweight) were started by intraperitoneal injection on days 1, 3, and 5. Weight, disease activity index, histological score, and myeloperoxidase (MPO) activity were used to evaluate the severity of colitis. The expressions of occludin and autophagy-related proteins LC3BII/I were measured by western blot analysis. The lipopolysaccharide-induced HT-29 cell model was used to explore the mechanism. In vivo, IL-22 significantly alleviated DSS-induced clinical manifestations, reduced histological injury, and inhibited MPO activity. IL-22 upregulated the expression of occludin and the LC3B II/I ratio in the colon. In vitro, IL-22 significantly lowered TNF-α levels and enhanced the expression of occludin and the LC3B II/I ratio. Importantly, inhibiting autophagy in vitro by 3-Methyladenine (3-MA) attenuated the occludin protective effects of IL-22. In summary, our findings demonstrate that IL-22 ameliorates DSS-induced ulcerative colitis, which may be attributable to activating autophagy and then promoting occludin expression.

Interleukin-22 Alleviates Caerulein-Induced Acute Pancreatitis by Activating AKT/mTOR Pathway

BACKGROUND

Acute pancreatitis (AP) is one of the most common acute abdominal disorders; due to the lack of specific treatment, the treatment of acute pancreatitis, especially serious acute pancreatitis (SAP), is difficult and challenging. We will observe the changes of Interleukin -22 levels in acute pancreatitis animal models, and explore the mechanism of Interleukin -22 in acute pancreatitis.

OBJECTIVE

This study aims to assess the potential protective effect of Interleukin -22 on caerulein-induced acute pancreatitis and to explore its mechanism.

METHODS

Blood levels of amylase and lipase and Interleukin -22 were assessed in mice with acute pancreatitis. In animal model and cell model of caerulein-induced acute pancreatitis, the mRNA levels of P62 and Beclin-1 were determined using PCR, and the protein expression of P62, LC3-II, mTOR, AKT, p-mTOR, and p-AKT were evaluated through Western blot analysis.

RESULTS

Interleukin -22 administration reduced blood amylase and lipase levels and mitigated tissue damage in acute pancreatitis mice model. Interleukin -22 inhibited the relative mRNA levels of P62 and Beclin-1, and the Interleukin -22 group showed a decreased protein expression of LC3-II and P62 and the phosphorylation of the AKT/mTOR pathway. Furthermore, we obtained similar results in the cell model of acute pancreatitis.

CONCLUSION

This study suggests that Interleukin -22 administration could alleviate pancreatic damage in caerulein-induced acute pancreatitis. This effect may result from the activation of the AKT/mTOR pathway, leading to the inhibition of autophagy. Consequently, Interleukin -22 shows potential as a treatment.

Akkermansia muciniphila and Parabacteroides distasonis synergistically protect from colitis by promoting ILC3 in the gut

Inflammatory bowel disease (IBD) is a group of inflammatory conditions of the gastrointestinal tract. The etiology of IBD remains elusive, but the disease is suggested to arise from the interaction of environmental and genetic factors that trigger inadequate immune responses and inflammation in the intestine. The gut microbiome majorly contributes to disease as an environmental variable, and although some causative bacteria are identified, little is known about which specific members of the microbiome aid in the intestinal epithelial barrier function to protect from disease. While chemically inducing colitis in mice from two distinct animal facilities, we serendipitously found that mice in one facility showed remarkable resistance to disease development, which was associated with increased markers of epithelial barrier integrity. Importantly, we show that Akkermansia muciniphila and Parabacteroides distasonis were significantly increased in the microbiota of resistant mice. To causally connect these microbes to protection against disease, we colonized susceptible mice with the two bacterial species. Our results demonstrate that A. muciniphila and P. distasonis synergistically drive a protective effect in both acute and chronic models of colitis by boosting the frequency of type 3 innate lymphoid cells in the colon and by improving gut epithelial integrity. Altogether, our work reveals a combined effort of commensal microbes in offering protection against severe intestinal inflammation by shaping gut immunity and by enhancing intestinal epithelial barrier stability. Our study highlights the beneficial role of gut bacteria in dictating intestinal homeostasis, which is an important step toward employing microbiome-driven therapeutic approaches for IBD clinical management.

IMPORTANCE

The contribution of the gut microbiome to the balance between homeostasis and inflammation is widely known. Nevertheless, the etiology of inflammatory bowel disease, which is known to be influenced by genetics, immune response, and environmental cues, remains unclear. Unlocking novel players involved in the dictation of a protective gut, namely, in the microbiota component, is therefore crucial to develop novel strategies to tackle IBD. Herein, we revealed a synergistic interaction between two commensal bacterial strains, Akkermansia muciniphila and Parabacteroides distasonis, which induce protection against both acute and chronic models of colitis induction, by enhancing epithelial barrier integrity and promoting group 3 innate lymphoid cells in the colonic mucosa. This study provides a novel insight on how commensal bacteria can beneficially act to promote intestinal homeostasis, which may open new avenues toward the use of microbiome-derived strategies to tackle IBD.

Cryptosporidium infection of human small intestinal epithelial cells induces type III interferon and impairs infectivity of Rotavirus

Cryptosporidiosis is a major cause of severe diarrheal disease in infants from resource poor settings. The majority of infections are caused by the human-specific pathogen C. hominis and absence of in vitro growth platforms has limited our understanding of host-pathogen interactions and development of effective treatments. To address this problem, we developed a stem cell-derived culture system for C. hominis using human enterocytes differentiated under air-liquid interface (ALI) conditions. Human ALI cultures supported robust growth and complete development of C. hominis in vitro including all life cycle stages. Cryptosporidium infection induced a strong interferon response from enterocytes, possibly driven, in part, by an endogenous dsRNA virus in the parasite. Prior infection with Cryptosporidium induced type III IFN secretion and consequently blunted infection with Rotavirus, including live attenuated vaccine strains. The development of hALI provides a platform for further studies on human-specific pathogens, including clinically important coinfections that may alter vaccine efficacy.

Interleukin-22 and acute pancreatitis: A review

Acute pancreatitis (AP) is one of the most common gastrointestinal diseases, and it is divided into 3 types according to its severity:mild acute pancreatitis, moderately severe acute pancreatitis, and severe acute pancreatitis. The mortality in severe acute pancreatitis is approximately 15% to 30% due to multiorgan dysfunction and the lack of specific treatment. Interleukin-22 (IL-22) is a member of the Interleukin-10 family, and it can activate several downstream signaling pathways by binding to its receptor complex, thus it is involved in cell differentiation, proliferation, and apoptosis. Some studies have reported the elevated level of IL-22 in patients with AP, which suggests IL-22 may be involved in the pathogenesis of AP. And many studies have shown that IL-22 had a protective effect against AP. This article reviews the characteristics and mechanism of IL-22 and its role in AP to provide insight into the treatment of AP.

Cryptosporidium infection of human small intestinal epithelial cells induces type III interferon and impairs infectivity of Rotavirus

Cryptosporidiosis is a major cause of severe diarrheal disease in infants from resource poor settings. The majority of infections are caused by the human-specific pathogen C. hominis and absence of in vitro growth platforms has limited our understanding of host-pathogen interactions and development of effective treatments. To address this problem, we developed a stem cell-derived culture system for C. hominis using human enterocytes differentiated under air-liquid interface (ALI) conditions. Human ALI cultures supported robust growth and complete development of C. hominis in vitro including all life cycle stages. C. hominis infection induced a strong interferon response from enterocytes, likely driven by an endogenous dsRNA virus in the parasite. Prior infection with Cryptosporidium induced type III IFN secretion and consequently blunted infection with Rotavirus, including live attenuated vaccine strains. The development of hALI provides a platform for further studies on human-specific pathogens, including clinically important coinfections that may alter vaccine efficacy.

Intestinal organoids in coculture: redefining the boundaries of gut mucosa ex vivo modeling

All-time preservation of an intact mucosal barrier is crucial to ensuring intestinal homeostasis and, hence, the organism's overall health maintenance. This complex process relies on an equilibrated signaling system between the intestinal epithelium and numerous cell populations inhabiting the gut mucosa. Any perturbations of this delicate cross talk, particularly regarding the immune cell compartment and microbiota, may sustainably debilitate the intestinal barrier function. As a final joint event, a critical rise in epithelial permeability facilitates the exposure of submucosal immunity to microbial antigens, resulting in uncontrolled inflammation, collateral tissue destruction, and dysbiosis. Organoid-derived intestinal coculture models have established themselves as convenient tools to reenact such pathophysiological events, explore interactions between selected cell populations, and assess their roles with a central focus on intestinal barrier recovery and stabilization.

Bacterial Translocation as Inflammatory Driver in Crohn's Disease

Crohn’s disease (CD) is a chronic inflammatory disorder of the gastrointestinal tract responsible for intestinal lesions. The multifactorial etiology attributed to CD includes a combination of environmental and host susceptibility factors, which result in an impaired host–microbe gut interaction. Bacterial overgrowth and dysbiosis, increased intestinal barrier permeability, and altered inflammatory responses in patients with CD have been described in the past. Those events explain the pathogenesis of luminal translocation of bacteria or its products into the blood, a frequent event in CD, which, in turn, favors a sustained inflammatory response in these patients. In this review, we navigate through the interaction between bacterial antigen translocation, permeability of the intestinal barrier, immunologic response of the host, and genetic predisposition as a combined effect on the inflammatory response observed in CD. Several lines of evidence support that translocation of bacterial products leads to uncontrolled inflammation in CD patients, and as a matter of fact, the presence of gut bacterial genomic fragments at a systemic level constitutes a marker for increased risk of relapse among CD patients. Also, the significant percentage of CD patients who lose response to biologic therapies may be influenced by the translocation of bacterial products, which are well-known drivers of proinflammatory cytokine production by host immune cells. Further mechanistic studies evaluating cellular and humoral immune responses, gut microbiota alterations, and genetic predisposition will help clinicians to better control and personalize the management of CD patients in the future.

A Novel Microphysiological Colon Platform to Decipher Mechanisms Driving Human Intestinal Permeability

BACKGROUND & AIMS

The limited availability of organoid systems that mimic the molecular signatures and architecture of human intestinal epithelium has been an impediment to allowing them to be harnessed for the development of therapeutics as well as physiological insights. We developed a microphysiological Organ-on-Chip (Emulate, Inc, Boston, MA) platform designed to mimic properties of human intestinal epithelium leading to insights into barrier integrity.

METHODS

We combined the human biopsy-derived leucine-rich repeat-containing G-protein-coupled receptor 5-positive organoids and Organ-on-Chip technologies to establish a micro-engineered human Colon Intestine-Chip (Emulate, Inc, Boston, MA). We characterized the proximity of the model to human tissue and organoids maintained in suspension by RNA sequencing analysis, and their differentiation to intestinal epithelial cells on the Colon Intestine-Chip under variable conditions. Furthermore, organoids from different donors were evaluated to understand variability in the system. Our system was applied to understanding the epithelial barrier and characterizing mechanisms driving the cytokine-induced barrier disruption.

RESULTS

Our data highlight the importance of the endothelium and the in vivo tissue-relevant dynamic microenvironment in the Colon Intestine-Chip in the establishment of a tight monolayer of differentiated, polarized, organoid-derived intestinal epithelial cells. We confirmed the effect of interferon-γ on the colonic barrier and identified reorganization of apical junctional complexes, and induction of apoptosis in the intestinal epithelial cells as mediating mechanisms. We show that in the human Colon Intestine-Chip exposure to interleukin 22 induces disruption of the barrier, unlike its described protective role in experimental colitis in mice.

CONCLUSIONS

We developed a human Colon Intestine-Chip platform and showed its value in the characterization of the mechanism of action of interleukin 22 in the human epithelial barrier. This system can be used to elucidate, in a time- and challenge-dependent manner, the mechanism driving the development of leaky gut in human beings and to identify associated biomarkers.

Secretory Sorcery: Paneth Cell Control of Intestinal Repair and Homeostasis

Paneth cells are professional secretory cells that classically play a role in the innate immune system by secreting antimicrobial factors into the lumen to control enteric bacteria. In this role, Paneth cells are able to sense cues from luminal bacteria and respond by changing production of these factors to protect the epithelial barrier. Paneth cells rely on autophagy to regulate their secretory capability and capacity. Disruption of this pathway through mutation of genes, such as Atg16L1, results in decreased Paneth cell function, dysregulated enteric microbiota, decreased barrier integrity, and increased risk of diseases such as Crohn's disease in humans. Upon differentiation Paneth cells migrate downward and intercalate among active intestinal stem cells at the base of small intestinal crypts. This localization puts them in a unique position to interact with active intestinal stem cells, and recent work shows that Paneth cells play a critical role in influencing the intestinal stem cell niche. This review discusses the numerous ways Paneth cells can influence intestinal stem cells and their niche. We also highlight the ways in which Paneth cells can alter cells and other organ systems.

Identification of Differentially Expressed Non-coding RNA Networks With Potential Immunoregulatory Roles During Salmonella Enteritidis Infection in Ducks

Salmonella enterica serovar Enteritidis (S. Enteritidis) is a pathogen that can colonize the preovulatory follicles of poultry, thereby causing both reduced egg production and an elevated risk of foodborne salmonellosis in humans. Although a few studies have revealed S. Enteritidis preferentially invades the granulosa cell layer within these follicles, it can readily persist and proliferate through mechanisms that are not well-understood. In this study, we characterized competing endogenous RNA (ceRNA) regulatory networks within duck granulosa cells following time-course of S. Enteritidis challenge. The 8108 long non-coding RNAs (lncRNAs), 1545 circular RNAs (circRNAs), 542 microRNAs (miRNAs), and 4137 mRNAs (fold change ≥2; P < 0.01) were differentially expressed during S. Enteritidis challenge. Also, eight mRNAs, eight lncRNAs and five circRNAs were selected and the consistent expression trend was found between qRT-PCR detection and RNA-seq. Moreover, the target genes of these differentially expressed ncRNAs (including lncRNAs, circRNAs and miRNAs) were predicted, and significantly enriched in the innate immune response and steroidogenesis pathways. Then, the colocalization and coexpression analyses were conducted to investigate relationships between ncRNAs and mRNAs. The 16 differentially expressed miRNAs targeting 60 differentially expressed mRNAs were identified in granulosa cells at 3 and 6 h post-infection (hpi) and enriched in the MAPK, GnRH, cytokine-cytokine receptor interaction, Toll-like receptor, endocytosis, and oxidative phosphorylation signaling pathways. Additionally, underlying lncRNA-miRNA-mRNA and circRNA-miRNA-mRNA ceRNA networks were then constructed to further understand their interaction during S. Enteritidis infection. Lnc_012227 and novel_circ_0004892 were identified as ceRNAs, which could compete with miR-let-7g-5p and thereby indirectly modulating map3k8 expression to control S. Enteritidis infection. Together, our data thus identified promising candidate ncRNAs responsible for regulating S. Enteritidis infection in the preovulatory follicles of ducks, offering new insights regarding the ovarian transmission of this pathogen.

Fermented Rice Bran Supplementation Prevents the Development of Intestinal Fibrosis Due to DSS-Induced Inflammation in Mice

Fermented rice bran (FRB) is known to protect mice intestines against dextran sodium sulfate (DSS)-induced inflammation; however, the restoration of post-colitis intestinal homeostasis using FRB supplementation is currently undocumented. In this study, we observed the effects of dietary FRB supplementation on intestinal restoration and the development of fibrosis after DSS-induced colitis. DSS (1.5%) was introduced in the drinking water of mice for 5 days. Eight mice were sacrificed immediately after the DSS treatment ended. The remaining mice were divided into three groups, comprising the following diets: control, 10% rice bran (RB), and 10% FRB-supplemented. Diet treatment was continued for 2 weeks, after which half the population of mice from each group was sacrificed. The experiment was continued for another 3 weeks before the remaining mice were sacrificed. FRB supplementation could reduce the general observation of colitis and production of intestinal pro-inflammatory cytokines. FRB also increased intestinal mRNA levels of anti-inflammatory cytokine, tight junction, and anti-microbial proteins. Furthermore, FRB supplementation suppressed markers of intestinal fibrosis. This effect might have been achieved via the canonical Smad2/3 activation and the non-canonical pathway of Tgf-β activity. These results suggest that FRB may be an alternative therapeutic agent against inflammation-induced intestinal fibrosis.

Dysregulation of IL-17/IL-22 Effector Functions in Blood and Gut Mucosal Gamma Delta T Cells Correlates With Increase in Circulating Leaky Gut and Inflammatory Markers During cART-Treated Chronic SIV Infection in Macaques

HIV-associated inflammation has been implicated in the premature aging and increased risk of age-associated comorbidities in cART-treated individuals. However, the immune mechanisms underlying the chronic inflammatory state of cART-suppressed HIV infection remain unclear. Here, we investigated the role of γδT cells, a group of innate IL-17 producing T lymphocytes, in the development of systemic inflammation and leaky gut phenotype during cART-suppressed SIV infection of macaques. Plasma levels of inflammatory mediators, intestinal epithelial barrier disruption (IEBD) and microbial translocation (MT) biomarkers, and Th1/Th17-type cytokine functions were longitudinally assessed in blood and gut mucosa of SIV-infected, cART-suppressed macaques. Among the various gut mucosal IL-17/IL-22-producing T lymphocyte subsets including Th17, γδT, CD161+ CD8+ T, and MAIT cells, a specific decline in the Vδ2 subset of γδT cells and impaired IL-17/IL-22 production in γδT cells significantly correlated with the subsequent increase in plasma IEBD/MT markers (IFABP, LPS-binding protein, and sCD14) and pro-inflammatory cytokines (IL-6, IL-1β, IP10, etc.) despite continued viral suppression during long-term cART. Further, the plasma inflammatory cytokine signature during long-term cART was distinct from acute SIV infection and resembled the inflammatory cytokine profile of uninfected aging (inflammaging) macaques. Overall, our data suggest that during cART-suppressed chronic SIV infection, dysregulation of IL-17/IL-22 cytokine effector functions and decline of Vδ2 γδT cell subsets may contribute to gut epithelial barrier disruption and development of a distinct plasma inflammatory signature characteristic of inflammaging. Our results advance the current understanding of the impact of chronic HIV/SIV infection on γδT cell functions and demonstrate that in the setting of long-term cART, the loss of epithelial barrier-protective functions of Vδ2 T cells and ensuing IEBD/MT occurs before the hallmark expansion of Vδ1 subsets and skewed Vδ2/Vδ1 ratio. Thus, our work suggests that novel therapeutic approaches toward restoring IL-17/IL-22 cytokine functions of intestinal Vδ2 T cells may be beneficial in preserving gut epithelial barrier function and reducing chronic inflammation in HIV-infected individuals.

The role of Th17 cells in psoriasis

T helper 17 (Th17) cells have been involved in the pathogenesis of many autoimmune and inflammatory diseases, like psoriasis, multiple sclerosis (MS), rheumatoid arthritis (RA), and inflammatory bowel disease (IBD). However, the role of Th17 cells in psoriasis has not been clarified completely. Th17-derived proinflammatory cytokines including IL-17A, IL-17F, IL-21, IL-22, and IL-26 have a critical role in the pathogenesis of these disorders. In this review, we introduced the signaling and transcriptional regulation of Th17 cells. And then, we demonstrate the immunopathology role of Th17 cells and functions of the related cytokines in the psoriasis to get a better understanding of the inflammatory mechanisms mediated by Th17 cells in this disease.

Liver Buds and Liver Organoids: New Tools for Liver Development, Disease and Medical Application

The current understanding and effective treatment of liver disease is far from satisfactory. Liver organoids and liver buds (LBs) transforming cell culture from two dimensions(2D) to three dimensions(3D) has provided infinite possibilities for stem cells to use in clinic. Recent technological advances in the 3D culture have shown the potentiality of liver organoids and LBs as the promising tool to model in vitro liver diseases. The induced LBs and liver organoids provide a platform for cell-based therapy, liver disease models, liver organogenesis and drugs screening. And its genetic heterogeneity supplies a way for the realization of precision medicine.

Challenges and Pitfalls in the Engineering of Human Interleukin 22 (hIL-22) Secreting Lactobacillus reuteri

Engineered microbes for the delivery of intestinally directed therapeutics is a promising avenue for the treatment of various intestinal diseases including inflammatory bowel disease (IBD) and intestinal graft vs. host disease (GVHD). This modality of treatment would allow for the targeted delivery of therapeutics to the site of inflammation or disease while minimizing the systemic side effects that often accompany treatment of these pathologies. Here, we show the challenges encountered and overcome in successfully engineering Lactobacillus reuteri to secrete high levels of biologically active human interleukin 22 (hIL-22). Initial hIL-22 constructs secreted high levels of hIL-22, however we found the majority of hIL-22 was cleaved and not biologically active. Several strategies were explored to improve the production of intact hIL-22, with the optimization of the signal sequence for peptide secretion having the most impact of production of intact hIL-22. This resulted in L. reuteri secreting high concentrations (up to 700 ng/mL) of hIL-22. Bioactivity of hIL-22 was confirmed by the secretion of interleukin 10 (IL-10) from the colon cancer derived epithelial cell line Colo205 and the secretion of Regenerating islet-derived protein 3 alpha (Reg3α) from human jejunal enteroids. The secretion of bioactive hIL-22 imposed a significant cost for L. reuteri as bacterial growth was significantly impaired upon induction. Future challenges and optimization strategies for the delivery of hIL-22 to the human intestinal tract are discussed.

A Novel Mouse Model of Enteric Vibrio parahaemolyticus Infection Reveals that the Type III Secretion System 2 Effector VopC Plays a Key Role in Tissue Invasion and Gastroenteritis

The Gram-negative marine bacterium Vibrio parahaemolyticus is a common cause of infectious gastroenteritis due to the ingestion of contaminated seafood. Most virulent V. parahaemolyticus strains encode two type III secretion systems (T3SS1 and T3SS2); however, the roles they and their translocated effectors play in causing intestinal disease remain unclear. While studies have identified T3SS1 effectors as responsible for killing epithelial cells in culture, the T3SS2 effectors caused massive epithelial cell disruption in a rabbit ileal loop model. Additional models are thus needed to clarify the pathogen-host interactions that drive V. parahaemolyticus-associated gastroenteritis. Germfree mice were infected with a pathogenic clinical isolate of V. parahaemolyticus, RIMD2210633 (RIMD). The pathogen was found to adhere to as well as invade the cecal mucosa, accompanied by severe inflammation and dramatic mucosal damage, including widespread sloughing of infected epithelial cells. Mice infected with a V. parahaemolyticus strain lacking the T3SS1 (POR2) also developed severe pathology, similar to that seen with RIMD. In contrast, the ΔT3SS2 strain (POR3) appeared unable to invade the intestinal mucosa or cause any mucosal pathology. Confirming a role for TS332 effectors, a strain expressing the T3SS2 but lacking VopC (POR2ΔvopC), a T3SS2 effector implicated in epithelial cell invasion in culture, was strongly attenuated in invading the intestinal mucosa and in causing gastroenteritis, although infection with this mutant resulted in more pathology than the ΔT3SS2 strain. We thus present an experimental system that enables further characterization of T3SS effectors as well as the corresponding host inflammatory response involved in the gastroenteritis caused by invasive V. parahaemolyticus IMPORTANCE Vibrio parahaemolyticus causes severe gastroenteritis following consumption of contaminated seafood. Global warming has allowed this pathogen to spread worldwide, contributing to recent outbreaks. Clinical isolates are known to harbor an array of virulence factors, including T3SS1 and T3SS2; however, the precise role these systems play in intestinal disease remains unclear. There is an urgent need to improve our understanding of how V. parahaemolyticus infects hosts and causes disease. We present a novel mouse model for this facultative intracellular pathogen and observe that the T3SS2 is essential to pathogenicity. Moreover, we show that the T3SS2 effector VopC, previously shown to be a Rac and Cdc42 deamidase that facilitates bacterial uptake by nonphagocytic cells, also plays a key role in the ability of V. parahaemolyticus to invade the intestinal mucosa and cause gastroenteritis. This experimental model thus provides a valuable tool for future elucidation of virulence mechanisms used by this facultative intracellular pathogen during in vivo infection.

Epithelial Wntless is dispensable for intestinal tumorigenesis in mouse models

Wnt signaling is essential for the maintenance of adult stem cells and its aberrant activation is a stimulator of carcinogenesis. The transmembrane protein, Wntless, is an essential Wnt signaling component through regulating the secretion of Wnt ligands. Here, we generated a mouse model with specific Wntless knockout in intestinal epithelium to study its function in the intestinal epithelium. Wntless knockout exhibits no obvious defects in mice but significantly disrupted proliferation and differentiation of small intestinal organoids. We also discovered that these deficiencies could be partially rescued by Wnt3a supplement but not Wnt9b. To further investigate the role of Wntless in tumorigenesis, APC-deficient spontaneous intestinal tumors and chemical induced colorectal cancer mouse models were employed. To our surprise, intestinal epithelium-specific knockout of Wntless did not cause significant differences in tumor number and size. In summary, our data demonstrated that epithelial Wntless was required for the growth and differentiation of small intestinal organoids but not in live animals, suggesting the other tissues, such as mesenchymal tissue, play critical role for Wnt secretion in both intestinal homeostasis as well as tumorigenesis.