The intestinal epithelium: sensors to effectors in nematode infection

Animal healer for refractory diseases: Myth or reality?

A vast amount of knowledge has been acquired through human activities such as farming, hunting, and fishing. Throughout history, humans have utilized living creatures for disease treatment, relying on the natural world's healing powers. The special "healers" may be able to treat patients via the power of nature. However, there was no systematic introduction or summary of these treatments. Therefore, we conducted a literature review based on PubMed, Google Scholar, Web of Science, Scopus, CNKI and WanFang DATA. Here, we defined this unique method as "animal healer" and six common kinds of animal healers were reviewed. These are fish therapy, pet therapy, worm therapy, leech therapy, maggot therapy, and bee therapy. According to the different characteristics of healers, treatment methods mainly included bite, parasitism, contact and communication. With the advantages of green and effectiveness, animal healers have great therapy potential against a variety of refractory diseases. The main purpose of this review is to draw people's attention to animal healer, promote it to become a possible clinical treatment strategy, and make further exploration in species cultivation, mechanism research, animal welfare, standard setting, safety evaluation and other aspects. In the future, animal healers will play an increasingly important role in medicine and hopefully solve more medical problems and dilemmas.

In vitro differentiated human CD4+ T cells produce hepatocyte growth factor

Differentiation of naive CD4⁺ T cells into effector T cells is a dynamic process in which the cells are polarized into T helper (Th) subsets. The subsets largely consist of four fundamental categories: Th1, Th2, Th17, and regulatory T cells. We show that human memory CD4⁺ T cells can produce hepatocyte growth factor (HGF), a pleiotropic cytokine which can affect several tissue types through signaling by its receptor, c-Met. In vitro differentiation of T cells into Th-like subsets revealed that HGF producing T cells increase under Th1 conditions. Enrichment of HGF producing cells was possible by targeting cells with surface CD30 expression, a marker discovered through single-cell RNA-sequencing. Furthermore, pharmacological inhibition of PI3K or mTOR was found to inhibit HGF mRNA and protein, while an Akt inhibitor was found to increase these levels. The findings suggest that HGF producing T cells could play a role in disease where Th1 are present.

GLP-1 Receptor Agonists in Obese Patients with Inflammatory Bowel Disease: from Molecular Mechanisms to Clinical Considerations and Practical Recommendations for Safe and Effective Use

PURPOSE OF REVIEW

To discuss current literature and provide practical recommendations for the safe and effective use of glucagon-like peptide 1 receptor agonists (GLP-1 RA) in people with inflammatory bowel disease (IBD) and type 2 diabetes (T2D) and/or obesity. The molecular mechanisms that justify the potential benefits of GLP-1 RA in IBD and the links between IBD, obesity, and cardiovascular disease are also discussed.

RECENT FINDINGS

Preliminary data suggest that GLP-1 RA can modulate crucial pathways in the pathogenesis of IBD, such as chronic inflammation circuits, intestinal tight junctions, and gut microbiome dysbiosis, setting the stage for human trials to investigate the role of these agents in the treatment of IBD among people with or without diabetes and obesity. However, gastrointestinal side effects related to GLP-1 RA need appropriate clinical management to mitigate risks and maximize the benefits of therapy in people with IBD. GLP-1 RA originally emerged as drugs for the treatment of hyperglycemia and are currently licensed for the management of T2D and/or overweight/obesity. However, their wealth of pleiotropic actions soon raised expectations that they might confer benefits on non-metabolic disorders. Future studies are expected to clarify whether GLP-1 RA deserve an adjunct place in the arsenal of drugs against IBD.

An update on the biological characteristics and functions of tuft cells in the gut

The intestine is a powerful digestive system and one of the most sophisticated immunological organs. Evidence shows that tuft cells (TCs), a kind of epithelial cell with distinct morphological characteristics, play a significant role in various physiological processes. TCs can be broadly categorized into different subtypes depending on different molecular criteria. In this review, we discuss its biological properties and role in maintaining homeostasis in the gastrointestinal tract. We also emphasize its relevance to the immune system and highlight its powerful influence on intestinal diseases, including inflammations and tumors. In addition, we provide fresh insights into future clinical diagnostic and therapeutic strategies related to TCs.

Effects of helminths on the human immune response and the microbiome

Helminths have evolved sophisticated immune regulating mechanisms to prevent rejection by their mammalian host. Our understanding of how the human immune system responds to these parasites remains poor compared to mouse models of infection and this limits our ability to develop vaccines as well as harness their unique properties as therapeutic strategies against inflammatory disorders. Here, we review how recent studies on human challenge infections, self-infected individuals, travelers, and endemic populations have improved our understanding of human type 2 immunity and its effects on the microbiome. The heterogeneity of responses between individuals and the limited access to tissue samples beyond the peripheral blood are challenges that limit human studies on helminths, but also provide opportunities to transform our understanding of human immunology. Organoids and single-cell sequencing are exciting new tools for immunological analysis that may aid this pursuit. Learning about the genetic and immunological basis of resistance, tolerance, and pathogenesis to helminth infections may thus uncover mechanisms that can be utilized for therapeutic purposes.

Defining the early stages of intestinal colonisation by whipworms

Whipworms are large metazoan parasites that inhabit multi-intracellular epithelial tunnels in the large intestine of their hosts, causing chronic disease in humans and other mammals. How first-stage larvae invade host epithelia and establish infection remains unclear. Here we investigate early infection events using both Trichuris muris infections of mice and murine caecaloids, the first in-vitro system for whipworm infection and organoid model for live helminths. We show that larvae degrade mucus layers to access epithelial cells. In early syncytial tunnels, larvae are completely intracellular, woven through multiple live dividing cells. Using single-cell RNA sequencing of infected mouse caecum, we reveal that progression of infection results in cell damage and an expansion of enterocytes expressing of Isg15, potentially instigating the host immune response to the whipworm and tissue repair. Our results unravel intestinal epithelium invasion by whipworms and reveal specific host-parasite interactions that allow the whipworm to establish its multi-intracellular niche.

Whipworms are large parasites causing chronic disease in humans and other mammals. Here, the authors show how larvae create tunnels inside the gut lining and reveal the early host response to infection via Isg15 in mice and murine caecaloids.

Intestinal epithelial tuft cell induction is negated by a murine helminth and its secreted products

Helminth parasites are adept manipulators of the immune system, using multiple strategies to evade the host type 2 response. In the intestinal niche, the epithelium is crucial for initiating type 2 immunity via tuft cells, which together with goblet cells expand dramatically in response to the type 2 cytokines IL-4 and IL-13. However, it is not known whether helminths modulate these epithelial cell populations. In vitro, using small intestinal organoids, we found that excretory/secretory products (HpES) from Heligmosomoides polygyrus blocked the effects of IL-4/13, inhibiting tuft and goblet cell gene expression and expansion, and inducing spheroid growth characteristic of fetal epithelium and homeostatic repair. Similar outcomes were seen in organoids exposed to parasite larvae. In vivo, H. polygyrus infection inhibited tuft cell responses to heterologous Nippostrongylus brasiliensis infection or succinate, and HpES also reduced succinate-stimulated tuft cell expansion. Our results demonstrate that helminth parasites reshape their intestinal environment in a novel strategy for undermining the host protective response.

The Association Between Gut Microbiota, Toll-Like Receptors, and Colorectal Cancer

The large number of microbes found in the gut are involved in various critical biological processes in the human body and have dynamic and complex interactions with the immune system. Disruptions in the host’s gut microbiota and the metabolites produced during fermentation promote the development of intestinal inflammation and colorectal cancer (CRC). Toll-like receptors (TLRs) recognize specific microbial-associated molecular patterns specific to microorganisms whose signaling is involved in maintaining intestinal homeostasis or, under certain conditions, mediating dysbiosis-associated intestinal inflammation. The signaling pathways of TLRs are described first, followed by a discussion of the interrelationship between gut microbes and TLRs, including the activation of TLRs by gut microbes and the effect of TLRs on the distribution of gut microbiota, particularly the role of microbes in colorectal carcinogenesis via TLRs. Finally, we discuss the potential roles of various TLRs in colorectal cancer.

Risk and protection strategies of Amolops wuyiensis intestine against gastrointestinal nematode (Cosmocercoides wuyiensis n. sp.) infection

Anuran amphibians are susceptible to infection by intestinal nematodes, but the damage and response mechanisms that occur in their intestines after infection are only partially understood. In this study, the intestinal disruption and response mechanisms in Amolops wuyiensis frogs infected with Cosmocercoides wuyiensis n. sp. were revealed through analysis of the intestinal histopathology, digestive enzyme activity, transcriptome and intestinal microbiota. Tissue section analysis showed histological damage and inflammation in the infected intestine, and the digestive enzyme activity indicated a decrease in digestion and absorption of some nutrients. We found that infection led to differences in the intestinal microbiota composition, including lower diversity and symbiotic relationships. The greater relative abundance of the genera Burkholderia and Rhodococcus may enhance intestinal immunity to resist pathogenic infections. A comparison of the transcriptomes of infected and uninfected intestines revealed 1055 differentially expressed genes. GO enrichment and KEGG pathways analyses suggested that the guts of infected C. wuyiensis n. sp. show enhanced complement activation, cell adhesion molecule function, NOD-like receptor signalling pathway activity and other innate immunity responses. Among the adaptive immune responses, the intestinal immune network for IgA production was significantly enriched, and the expression of IL-17D and transforming growth factor beta-1 genes were upregulated in the infected intestine. These results imply that C. wuyiensis n. sp. infection of A. wuyiensis intestine may trigger innate and adaptive immune responses, which reduce the post-infection burden. Furthermore, the intestine of A. wuyiensis may also respond to C. wuyiensis n. sp. infection by increasing metallocarboxypeptidase activity and accelerating smooth muscle contraction.

Enteric Tuft Cells in Host-Parasite Interactions

Enteric tuft cells are chemosensory epithelial cells gaining attention in the field of host-parasite interactions. Expressing a repertoire of chemosensing receptors and mediators, these cells have the potential to detect lumen-dwelling helminth and protozoan parasites and coordinate epithelial, immune, and neuronal cell defenses against them. This review highlights the versatility of enteric tuft cells and sub-types thereof, showcasing nuances of tuft cell responses to different parasites, with a focus on helminths reflecting the current state of the field. The role of enteric tuft cells in irritable bowel syndrome, inflammatory bowel disease and intestinal viral infection is assessed in the context of concomitant infection with parasites. Finally, the review presents pertinent questions germane to understanding the enteric tuft cell and its role in enteric parasitic infections. There is much to be done to fully elucidate the response of this intriguing cell type to parasitic-infection and there is negligible data on the biology of the human enteric tuft cell—a glaring gap in knowledge that must be filled.

PGD2 and CRTH2 counteract Type 2 cytokine-elicited intestinal epithelial responses during helminth infection

Type 2 inflammation is associated with epithelial cell responses, including goblet cell hyperplasia, that promote worm expulsion during intestinal helminth infection. How these epithelial responses are regulated remains incompletely understood. Here, we show that mice deficient in the prostaglandin D2 (PGD2) receptor CRTH2 and mice with CRTH2 deficiency only in nonhematopoietic cells exhibited enhanced worm clearance and intestinal goblet cell hyperplasia following infection with the helminth Nippostrongylus brasiliensis. Small intestinal stem, goblet, and tuft cells expressed CRTH2. CRTH2-deficient small intestinal organoids showed enhanced budding and terminal differentiation to the goblet cell lineage. During helminth infection or in organoids, PGD2 and CRTH2 down-regulated intestinal epithelial Il13ra1 expression and reversed Type 2 cytokine-mediated suppression of epithelial cell proliferation and promotion of goblet cell accumulation. These data show that the PGD2-CRTH2 pathway negatively regulates the Type 2 cytokine-driven epithelial program, revealing a mechanism that can temper the highly inflammatory effects of the anti-helminth response.

Foxo1 controls gut homeostasis and commensalism by regulating mucus secretion

Mucus produced by goblet cells in the gastrointestinal tract forms a biological barrier that protects the intestine from invasion by commensals and pathogens. However, the host-derived regulatory network that controls mucus secretion and thereby changes gut microbiota has not been well studied. Here, we identify that Forkhead box protein O1 (Foxo1) regulates mucus secretion by goblet cells and determines intestinal homeostasis. Loss of Foxo1 in intestinal epithelial cells (IECs) results in defects in goblet cell autophagy and mucus secretion, leading to an impaired gut microenvironment and dysbiosis. Subsequently, due to changes in microbiota and disruption in microbiome metabolites of short-chain fatty acids, Foxo1 deficiency results in altered organization of tight junction proteins and enhanced susceptibility to intestinal inflammation. Our study demonstrates that Foxo1 is crucial for IECs to establish commensalism and maintain intestinal barrier integrity by regulating goblet cell function.

Helminth Induced Immunoregulation and Novel Therapeutic Avenue of Allergy

Allergic diseases are increasing at an alarming rate worldwide, particularly in developed countries. In contrast, there is a decrease in the prevalence of helminthic infections and other neglected diseases. The hygiene hypothesis elaborates parasitic infection, and allergy-associated diseases have an inverse relationship. Acute helminthic infection and allergic reaction stimulate Type 2 helper cells (Th2) immune response with up-regulation of cytokines IL-4-, IL-5-, and IL-13-mediated IgE and mast cell production, as well as eosinophilia. However, people who chronically suffer from helminthic infections are demarcated through polarized Th2 resulting in alternative macrophage activation and T regulatory response. This regulatory system reduces allergy incidence in individuals that are chronically diseased through helminth. As a result, the excretory-secretory (ES) substance derived from parasites and extracellular vesicular components can be used as a novel therapeutic modality of allergy. Therefore, the aim of this review meticulously explored the link between helminth infection and allergy, and utilization of the helminth secretome for therapeutic immunomodulation.

Development of caecaloids to study host-pathogen interactions: new insights into immunoregulatory functions of Trichuris muris extracellular vesicles in the caecum

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Development of new methods to generate, culture and characterise mouse caecaloids is described.

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Caecaloids recapitulate the caecal epithelium composition and spatial organisation.

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Caecaloids can be used to study host–caecal pathogen interactions in vitro.

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Trichuris muris EVs exert novel immunoregulatory effects on intestinal epithelial cells.

The caecum, an intestinal appendage in the junction of the small and large intestines, displays a unique epithelium that serves as an exclusive niche for a range of pathogens including whipworms (Trichuris spp.). While protocols to grow organoids from small intestine (enteroids) and colon (colonoids) exist, the conditions to culture organoids from the caecum have yet to be described. Here, we report methods to grow, differentiate and characterise mouse adult stem cell-derived caecal organoids, termed caecaloids. We compare the cellular composition of caecaloids with that of enteroids, identifying differences in intestinal epithelial cell populations that mimic those found in the caecum and small intestine. The remarkable similarity in the intestinal epithelial cell composition and spatial conformation of caecaloids and their tissue of origin enables their use as an in vitro model to study host interactions with important caecal pathogens. Thus, exploiting this system, we investigated the responses of caecal intestinal epithelial cells to extracellular vesicles secreted/excreted by the intracellular helminth Trichuris muris. Our findings reveal novel immunoregulatory effects of whipworm extracellular vesicles on the caecal epithelium, including the downregulation of responses to nucleic acid recognition and type-I interferon signalling.

Ginsenoside Rk3 alleviated DSS-induced ulcerative colitis by protecting colon barrier and inhibiting NLRP3 inflammasome pathway

Ginsenosides have a variety of pharmacological activities, including immunomodulatory, antitumor and anti-inflammatory activities. However, the effect of Rk3 on ulcerative colitis has rarely been reported. This study evaluated the effect of Rk3 on DSS-induced ulcerative colitis and preliminarily explored the anti-inflammatory mechanisms. Rk3 administration significantly attenuated the weight loss, increased DAI scores, colonic shortening, and increased MPO and iNOS activities caused by DSS in mice. Histological improvement was apparent, tight junctions in the colon were restored, and the levels of short-chain fatty acids (acetic acid, butyric acid and isovaleric acid) were increased. In addition, Rk3 reduced the expression of proinflammatory factors (TNF-α, IL-1β and IL-6), NLRP3, ASC, and Caspase-1, indicating blockade of the NLRP3 inflammasome pathway. These results show that Rk3 can improve DSS-induced ulcerative colitis by protecting intestinal barrier function and inhibiting NLRP3 inflammasome expression, indicating that Rk3 could be used as a potential drug for treating ulcerative colitis.

Sequential Changes in the Host Gut Microbiota During Infection With the Intestinal Parasitic Nematode Strongyloides venezuelensis

Soil-transmitted helminths (STHs) are medically important parasites that infect 1. 5 billion humans globally, causing a substantial disease burden. These parasites infect the gastrointestinal tract (GIT) of their host where they co-exist and interact with the host gut bacterial flora, leading to the coevolution of the parasites, microbiota, and host organisms. However, little is known about how these interactions change through time with the progression of infection. Strongyloidiasis is a human parasitic disease caused by the nematode Strongyloides stercoralis infecting 30-100 million people. In this study, we used a closely related rodent parasite Strongyloides venezuelensis and mice as a model of gastrointestinal parasite infection. We conducted a time-course experiment to examine changes in the fecal microbiota from the start of infection to parasite clearance. We found that bacterial taxa in the host intestinal microbiota changed significantly as the infection progressed, with an increase in the genera Bacteroides and Candidatus Arthromitus, and a decrease in Prevotella and Rikenellaceae. However, the microbiota recovered to the pre-infective state after parasite clearance from the host, suggesting that these perturbations are reversible. Microarray analysis revealed that this microbiota transition is likely to correspond with the host immune response. These findings give us an insight into the dynamics of parasite-microbiota interactions in the host gut during parasite infection.

Experimental models to study intestinal microbes–mucus interactions in health and disease

A close symbiotic relationship exists between the intestinal microbiota and its host. A critical component of gut homeostasis is the presence of a mucus layer covering the gastrointestinal tract. Mucus is a viscoelastic gel at the interface between the luminal content and the host tissue that provides a habitat to the gut microbiota and protects the intestinal epithelium. The review starts by setting up the biological context underpinning the need for experimental models to study gut bacteria-mucus interactions in the digestive environment. We provide an overview of the structure and function of intestinal mucus and mucins, their interactions with intestinal bacteria (including commensal, probiotics and pathogenic microorganisms) and their role in modulating health and disease states. We then describe the characteristics and potentials of experimental models currently available to study the mechanisms underpinning the interaction of mucus with gut microbes, including in vitro, ex vivo and in vivo models. We then discuss the limitations and challenges facing this field of research.

Increased susceptibility to oral Trichuris muris infection in the specific absence of CXCR5+ CD11c+ cells

Trichuris muris is a natural mouse helminth pathogen which establishes infection specifically in the caecum and proximal colon. The rapid expulsion of T. muris in resistant mouse strains is associated with the induction of a protective T helper cell type 2 (Th2)‐polarized immune response. Susceptible mouse strains, in contrast, mount an inappropriate Th1 response to T. muris infection. Expression of the chemokine CXCL13 by stromal follicular dendritic cells attracts CXCR5‐expressing cells towards the B‐cell follicles. Previous studies using a complex in vivo depletion model have suggested that CXCR5‐expressing conventional dendritic cells (cDC) help regulate the induction of Th2‐polarized responses. Here, transgenic mice with CXCR5 deficiency specifically restricted to CD11c⁺ cells were used to determine whether the specific absence CXCR5 on CD11c⁺ cells such as cDC would influence susceptibility to oral T. muris infection by affecting the Th1/Th2 balance. We show that in contrast to control mice, those which lacked CXCR5 expression on CD11c⁺ cells failed to clear T. muris infection and developed cytokine and antibody responses that suggested a disturbed Th1/Th2 balance with enhanced IFN‐γ expression. These data suggest an important role of CXCR5‐expressing CD11c⁺ cells such as cDC in immunity to oral T. muris infection.

The Notch signaling pathway promotes basophil responses during helminth-induced type 2 inflammation

Basophils promote type 2 inflammation that mediates worm clearance during murine infection with the gastrointestinal helminth parasite Trichuris muris. Webb et al. show for the first time that basophil–intrinsic Notch signaling is required for basophil gene expression and a functional program that support helminth expulsion.

Type 2 inflammation drives the clearance of gastrointestinal helminth parasites, which infect over two billion people worldwide. Basophils are innate immune cells that support host-protective type 2 inflammation during murine infection with the helminth Trichuris muris. However, the mechanisms required for basophil function and gene expression regulation in this context remain unclear. We show that during T. muris infection, basophils localized to the intestine and up-regulated Notch receptor expression, rendering them sensitive to Notch signals that rapidly regulate gene expression programs. In vitro, Notch inhibition limited basophil cytokine production in response to cytokine stimulation. Basophil-intrinsic Notch signaling was required for T. muris–elicited changes in genome-wide basophil transcriptional programs. Mice lacking basophil-intrinsic functional Notch signaling had impaired worm clearance, decreased intestinal type 2 inflammation, altered basophil localization in the intestine, and decreased CD4⁺ T helper 2 cell responses following infection. These findings demonstrate that Notch is required for basophil gene expression and effector function associated with helminth expulsion during type 2 inflammation.

The therapeutic prospect of crosstalk between prokaryotic and eukaryotic organisms in the human gut

The peaceful phenomenon of the co-evolution between the prokaryotes (microbiota) and the eukaryotes (parasites including protozoa and helminths) in the animal gut has drawn the researchers' attention. Importantly, exploring the potential of helminths for therapeutic uses was one of the reasons behind understanding the physiological and immunological crosstalk existing between them. Here we discuss the interactive immunological associations of helminths and microbial responses individually and in combination with their hosts. Considering that there is probably crosstalk between eukaryotic organisms like helminths and protozoa with their host's gut microbiota, in this review we searched the literature identifying the privileged and favourable relationship generated between them in the host. Understanding the possibilities of the role of helminths along with gut microbiota as a black box would certainly help decode the therapeutic intrusion with helminths in experimental clinical trials, and a successful trial could be used to consider possible future and safe treatments for various immune-inflammatory diseases in humans.

Immune response against subclinical haemonchosis in Himalayan hill goats

Haemonchosis commonly occurs as chronic and subclinical infection in small ruminants, and understanding of immunological response against subclinical haemonchosis is of paramount importance for designing and implementing effective control strategies. The present study was designed to evaluate immunological response during subclinical haemonchosis, experimentally established in goats. Sixteen 5-6 month-old helminth naive kids were randomly allocated into one of two groups, infected and uninfected; the infected group being infected per os with 250 Haemonchus contortus larvae per kg body weight. Faecal, blood and serum samples were collected every third day up to 30 days post-infection (DPI), thereafter weekly up to 58 DPI to record changes in faecal egg count (FEC), haemoglobin (Hb), packed cell volume (PCV), peripheral eosinophil percentage and immunological parameters, such as macrophage cytokine interleukin-12 (IL-12), Th1 cytokine (IFN-γ), Th2 cytokines (IL-4, 13, 25, 33) and immunoglobulins (IgG and IgE). Pre-patent period of H. contortus in the present study was 18 days and eggs per gram (EPG) peaked on 30 DPI. The total reduction in body weight gain in the infected group was 26 g per day when compared with uninfected animals. Hb (7.35 ± 0.34 g/dL in infected animals compared with 9.76 ± 0.67 in control animals) and PCV levels (22 ± 1.54 g/dL in infected animals compared with 29.2 ± 1.27 in control animals) decreased significantly up to 44 DPI in infected group (P = 0.000). IL-4, IL-13, IL-33, IgG and IgE showed significant increase in infected animals at different periods. IFN-γ, IL-12 and IL-25 did not show any significant changes barring a steep rise of IFN-γ on 27 DPI. A positive correlation was observed between IgE and IL-4 in subclinical haemonchosis. Of particular note was that all the major cytokines, such as IFN-γ (P = 0.000), IL-4 (P = 0.000), IL-13 (P = 0.009), and both IgG (P = 0.000) and IgE (P = 0.003), were observed at the lowest concentration on 24 DPI. The effect of infection was found to be significant on cytokines with a strong interaction with time. Taken together, the data suggest that Th2 immune response is predominating in subclinical haemonchosis. The economic loss in term of body weight gain due to subclinical haemonchosis was considerable.

Exclusive dependence of IL-10Rα signalling on intestinal microbiota homeostasis and control of whipworm infection

The whipworm Trichuris trichiura is a soil-transmitted helminth that dwells in the epithelium of the caecum and proximal colon of their hosts causing the human disease, trichuriasis. Trichuriasis is characterized by colitis attributed to the inflammatory response elicited by the parasite while tunnelling through intestinal epithelial cells (IECs). The IL-10 family of receptors, comprising combinations of subunits IL-10Rα, IL-10Rβ, IL-22Rα and IL-28Rα, modulates intestinal inflammatory responses. Here we carefully dissected the role of these subunits in the resistance of mice to infection with T. muris, a mouse model of the human whipworm T. trichiura. Our findings demonstrate that whilst IL-22Rα and IL-28Rα are dispensable in the host response to whipworms, IL-10 signalling through IL-10Rα and IL-10Rβ is essential to control caecal pathology, worm expulsion and survival during T. muris infections. We show that deficiency of IL-10, IL-10Rα and IL-10Rβ results in dysbiosis of the caecal microbiota characterised by expanded populations of opportunistic bacteria of the families Enterococcaceae and Enterobacteriaceae. Moreover, breakdown of the epithelial barrier after whipworm infection in IL-10, IL-10Rα and IL-10Rβ-deficient mice, allows the translocation of these opportunistic pathogens or their excretory products to the liver causing organ failure and lethal disease. Importantly, bone marrow chimera experiments indicate that signalling through IL-10Rα and IL-10Rβ in haematopoietic cells, but not IECs, is crucial to control worm expulsion and immunopathology. These findings are supported by worm expulsion upon infection of conditional mutant mice for the IL-10Rα on IECs. Our findings emphasize the pivotal and complex role of systemic IL-10Rα signalling on immune cells in promoting microbiota homeostasis and maintaining the intestinal epithelial barrier, thus preventing immunopathology during whipworm infections.

IL-33 Induces Murine Intestinal Goblet Cell Differentiation Indirectly via Innate Lymphoid Cell IL-13 Secretion

Regulation of the intestinal mucus layer by goblet cells is important for preventing inflammation and controlling infection. IL-33, a cytokine upregulated in inflammatory bowel disease and helminth infection, induces intestinal goblet cells, but the mechanism remains unclear. Enteroids are three-dimensional structures of primary small intestinal epithelial cells that contain all differentiated intestinal epithelial cell types. We developed an enteroid-immune cell coculture model to determine the mechanism through which IL-33 affects intestinal goblet cell differentiation. We report that IL-33 does not directly induce goblet cell differentiation in murine enteroids; however, IL-13, a cytokine induced by IL-33, markedly induces goblet cells and gene expression consistent with goblet cell differentiation. When enteroids are cocultured with CD90⁺ mesenteric lymph node cells from IL-33-treated mice, IL-33 then induces IL-13 secretion by group 2 innate lymphoid cells and enteroid gene expression consistent with goblet cell differentiation. In cocultures, IL-33-induced Muc2 expression is dependent on enteroid Il4ra expression, demonstrating a requirement for IL-13 signaling in epithelial cells. In vivo, IL-33-induced intestinal goblet cell hyperplasia is dependent on IL-13. These studies demonstrate that IL-33 induces intestinal goblet cell differentiation not through direct action on epithelial cells but indirectly through IL-13 production by goup 2 innate lymphoid cells.

Bovine neutrophils form extracellular traps in response to the gastrointestinal parasite Ostertagia ostertagi

Ostertagia ostertagi (OO) is a widespread parasite that causes chronic infection in cattle and leads to annual losses of billions of dollars in the cattle industry. It remains unclear why cattle are unable to mount an effective immune response despite a large influx of immune cells to the infected abomasal mucosa and draining lymph nodes. Neutrophils, the immune system’s first responders, have the capacity to release neutrophil extracellular traps (NETs) to contain various pathogens, including some parasites. In the present study, the mechanisms by which O. ostertagi influences bovine NET formation were investigated. O. ostertagi larval soluble extract (OO extract) was able to induce typical NETs by purified neutrophils in vitro, confirmed by co-localization of extracellular DNA with typical NET-associated proteins histone and neutrophil elastase (NE). Consistent with existing literature, inhibition assays demonstrated that these OO extract-induced NETs were dependent upon the enzymes NADPH oxidase and myeloperoxidase (MPO). Live OO stage 4 larvae (L4) stimulated neutrophils to form NETs similar to those induced by OO extract. Bovine neutrophils also released NETs in response to Caenorhabditis elegans, a free-living soil nematode, suggesting that bovine NET production may be a conserved mechanism against a broad range of nematodes. This is the first report demonstrating O. ostertagi-induced NET formation by bovine neutrophils, a potentially underappreciated mechanism in the early immune response against nematode infections.

Goblet cells: multifaceted players in immunity at mucosal surfaces

Goblet cells (GCs) are specialized epithelial cells that line multiple mucosal surfaces and have a well-appreciated role in barrier maintenance through the secretion of mucus. Moreover, GCs secrete anti-microbial proteins, chemokines, and cytokines demonstrating functions in innate immunity beyond barrier maintenance. Recently it was appreciated that GCs can form goblet cell-associated antigen passages (GAPs) and deliver luminal substances to underlying lamina propria (LP) antigen-presenting cells (APCs) in a manner capable of inducing adaptive immune responses. GCs at other mucosal surfaces share characteristics with the GAP forming intestinal GCs, suggesting that GAP formation may not be restricted to the gut, and that GCs may perform this gatekeeper function at other mucosal surfaces. Here we review observations of how GCs contribute to immunity at mucosal surfaces through barrier maintenance, the delivery of luminal substances to APCs, interactions with APCs, and secretion of factors modulating immune responses.

Mucin 2 (MUC2) promoter characterization: an overview

Transgenic livestock have been studied with a well-known interest in improving quantitative and qualitative traits. In order to direct heterologous gene expression, it is indispensable to identify and characterize a promoter suitable for directing the expression of the gene of interest (GOI) in a tissue-specific way. The gastrointestinal tract is a desirable target for gene expression in several mammalian models. Throughout the surface of the intestinal epithelium, there is an intricate polymer network, formed by gel-forming mucins (especially MUC2 and MUC5AC, of which MUC2 is the major one), which plays a protective role due to the formation of a physical, chemical and immunological barrier between the organism and the environment. The characterization of the gel-forming mucins is difficult because of their large size and repetitive DNA sequences and domains. The main mucin in the small and large intestine, mucin 2 (MUC2), is expressed specifically in goblet cells. MUC2 plays an important role in intestinal homeostasis and its disruption is associated with several diseases and carcinomas. This mucin is also an important marker for elucidating mechanisms that regulate differentiation of the secretory cell lineage. This review presents the state of the art of MUC2 promoter structure and functional characterization.

Intraperitoneal administration of the anti-IL-23 antibody prevents the establishment of intestinal nematodes in mice

Previous studies have established that an increased Th-9 response creates a hostile environment for nematode parasites. Given that IL-23, a cytokine required for maintenance of the IL-17-secreting phenotype, has inhibitory effects on IL-9 production, we hypothesized that reducing circulating IL-23 by treatment with anti-IL-23 antibodies would reduce the establishment and development of parasitic intestinal nematodes. In this study, we show that animals treated with anti-IL-23 monoclonal antibodies showed a drastic reduction in the number of mouse pinworms (Aspiculuris tetraptera) recovered from the intestine (p < 0.001) at 23 days post-infection compared to the untreated animals. The cytokine levels in Peyer's patches (PP) in treated and infected animals increase the expression of interleukins such as IL-25, IL-21, and IL-9, augmenting mucus production in the crypts, and boosting chemokines, such as OX40 and CCL20 in the mucosa. Our results suggest that the Th17/Th2 regulatory mechanism provoked by the administration of the anti-IL-23 antibody prevents the implantation of the intestinal nematode in mice. The diminished inflammatory IL-17 levels alter the Th9 environment perhaps as a consequence of IL-17 inhibiting IL-9 expression. These Th9 conditions may explain the successful treatment against Inflammatory Bowel Disease (IBD) both with antibodies against IL-23 or through parasitization with nematodes.

Helminth Infections: Recognition and Modulation of the Immune Response by Innate Immune Cells

The survival of helminths in the host over long periods of time is the result of a process of adaptation or dynamic co-evolution between the host and the parasite. However, infection with helminth parasites causes damage to the host tissues producing the release of danger signals that induce the recruitment of various cells, including innate immune cells such as macrophages (Mo), dendritic cells (DCs), eosinophils, basophils, and mast cells. In this scenario, these cells are able to secrete soluble factors, which orchestrate immune effector mechanisms that depend on the different niches these parasites inhabit. Here, we focus on recent advances in the knowledge of excretory-secretory products (ESP), resulting from helminth recognition by DCs and Mo. Phagocytes and other cells types such as innate lymphocyte T cells 2 (ILC2), when activated by ESP, participate in an intricate cytokine network to generate innate and adaptive Th2 responses. In this review, we also discuss the mechanisms of innate immune cell-induced parasite killing and the tissue repair necessary to assure helminth survival over long periods of time.

Sodium Butyrate Inhibits Inflammation and Maintains Epithelium Barrier Integrity in a TNBS-induced Inflammatory Bowel Disease Mice Model

G Protein Coupled Receptor 109A (GPR109A), which belongs to the G protein coupled receptor family, can be activated by niacin, butyrate, and β-hydroxybutyric acid. Here, we assessed the anti-inflammatory activity of sodium butyrate (SB) on 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis mice, an experimental model that resembles Crohn's disease, and explored the potential mechanism of SB in inflammatory bowel disease (IBD). In vivo, experimental GPR109a^-/- and wild-type (WT) mice were administered SB (5g/L) in their drinking water for 6weeks. The mice were then administered TNBS via rectal perfusion to imitate colitis. In vitro, RAW246.7 macrophages, Caco-2 cells, and primary peritoneal macrophages were used to investigate the protective roles of SB on lipopolysaccharide (LPS)-induced inflammatory response and epithelium barrier dysfunction. In vivo, SB significantly ameliorated the inflammatory response and intestinal epithelium barrier dysfunction in TNBS-induced WT mice, but failed to provide a protective effect in TNBS-induced GPR109a^-/- mice. In vitro, pre-treatment with SB dramatically inhibited the expression of TNF-α and IL-6 in LPS-induced RAW246.7 macrophages. SB inhibited the LPS-induced phosphorylation of the NF-κB p65 and AKT signaling pathways, but failed to inhibit the phosphorylation of the MAPK signaling pathway. Our data indicated that SB ameliorated the TNBS-induced inflammatory response and intestinal epithelium barrier dysfunction through activating GPR109A and inhibiting the AKT and NF-κB p65 signaling pathways. These findings therefore extend the understanding of GPR109A receptor function and provide a new theoretical basis for treatment of IBD.

Histochemical and immunohistochemical characterization of rodlet cells in the intestine of two teleosts, Anguilla anguilla and Cyprinus carpio

Rodlet cells (RC) are characterized by a distinctive cell cortex and conspicuous inclusions named "rodlets." These cells are particularly abundant and large in size in intestine of eels. Histochemical, immunohistochemical and ultrastructural investigations were carried out on European eel Anguilla anguilla and Common carp Cyprinus carpio from Northern Italy. Eight biotinylated lectins were used to probe for specific carbohydrate residues in deparaffinized, hydrated intestinal sections of eel and carp. Five antibodies were tested on intestinal sections of both fish species: inducible nitric oxide synthase (i-NOS), leu-enkephalin, lysozyme, serotonin and tumour necrosis factor-α. Lectin histochemistry revealed rodlet cells (RCs) of the eel intestine to react with two of the eight lectins tested, specifically Concanavalin A (ConA) and Sambucus Nigra Agglutinin (SNA). This contrasted to lectin staining of RCs in the intestine of common carp, where four of the eight lectins showed a positive reaction; Dolichos Biflorus Agglutinin (DBA), Wheat Germ Agglutinin (WGA), SNA and ConA. RCs in eel and carp intestine were immunoreactive with antibodies to lysozyme and i-NOS. The occurrence of the inflammatory peptides lysozyme and i-NOS in RCs of the eel and common carp poses in favour that these cells are involved in the mechanism of defence against pathogens.

Intestinal immunity suppresses carrying capacity of rats for the model tapeworm, Hymenolepis diminuta

Hymenolepis diminuta is a parasitic tapeworm of the rat small intestine and is recognized as a useful model for the analysis of cestode-host interactions. In this study, we analyzed factors affecting the biomass of the tapeworm through use of rat strains carrying genetic mutations, namely X-linked severe combined immunodeficiency (xscid; T, B and NK cells deficiency), nude (rnu; T cell deficiency), and mast cell deficient rats. The worm biomass of F344-xscid rats after infection with 5 cysticercoids was much larger than control F344 rats from 3 to 8 weeks. The biomass of F344-rnu rats was also larger than the controls, but was intermediate between F344-xscid and control rats. These observations demonstrated that host immunity can control the maximal tapeworm biomass, i.e., carrying capacity, of the rat small intestine. Both T cell and other immune cells (B and NK cells) have roles in determining the carrying capacity of tapeworms. Total worm biomass and worm numbers in mast cell deficient rats (WsRC-Ws/Ws) were not significantly different from control WsRC-+/+ rats after 3 and 6 weeks of primary infection. Mast cell deficient rats displayed reinfection resistance for worm biomass but not worm expulsion. These findings suggest that the mast cell has a role for controlling the biomass of this tapeworm in reinfection alone, but does not affect the rate of worm expulsion. Overall, our findings indicate that the mast cell is not a major effector cell for the control of the carrying capacity of tapeworms. The identity of the major effector cell remains unknown.

Enteroendocrine cells-sensory sentinels of the intestinal environment and orchestrators of mucosal immunity

The intestinal epithelium must balance efficient absorption of nutrients with partitioning commensals and pathogens from the bodies' largest immune system. If this crucial barrier fails, inappropriate immune responses can result in inflammatory bowel disease or chronic infection. Enteroendocrine cells represent 1% of this epithelium and have classically been studied for their detection of nutrients and release of peptide hormones to mediate digestion. Intriguingly, enteroendocrine cells are the key sensors of microbial metabolites, can release cytokines in response to pathogen associated molecules and peptide hormone receptors are expressed on numerous intestinal immune cells; thus enteroendocrine cells are uniquely equipped to be crucial and novel orchestrators of intestinal inflammation. In this review, we introduce enteroendocrine chemosensory roles, summarize studies correlating enteroendocrine perturbations with intestinal inflammation and describe the mechanistic interactions by which enteroendocrine and mucosal immune cells interact during disease; highlighting this immunoendocrine axis as a key aspect of innate immunity.

Protective responses of intestinal mucous cells in a range of fish-helminth systems

Histopathological, immunofluorescence and ultrastructural studies were conducted on the intestines of four fish species infected with different taxa of enteric helminths. Brown trout (Salmo trutta trutta), eel (Anguilla anguilla) and tench (Tinca tinca) obtained from Lake Piediluco (central Italy) were examined. Brown trout and eel were infected with two species of acanthocephalans, and tench was parasitized with a tapeworm species. In addition to the above site, specimens of chub (Squalius cephalus) and brown trout infected with an acanthocephalan were examined from the River Brenta (north Italy). Moreover, eels were examined from a brackish water, Comacchio lagoons (north Italy), where one digenean species was the predominant enteric worm. All the helminths species induced a similar response, the hyperplasia of the intestinal mucous cells, particularly of those secreting acid mucins. Local endocrine signals seemed to affect the production and secretion of mucus in the parasitized fish, as worms often were surrounded by an adherent mucus layer or blanket. This is the first quantitative report of enteric worm effects on the density of various mucous cell types and on the mucus composition in intestine of infected/uninfected conspecifics. We provide a global comparison between the several fish-helminth systems examined.

Self-adjuvanting C18 lipid vinil sulfone-PP2A vaccine: study of the induced immunomodulation against Trichuris muris infection

Despite the importance of the adjuvant in the immunization process, very few adjuvants merge with the antigens in vaccines. A synthetic self-adjuvant oleic-vinyl sulfone (OVS) linked to the catalytic region of recombinant serine/threonine phosphatase 2A from the nematode Angiostrongylus costaricensis (rPP2A) was used for intranasal immunization in mice previously infected with Trichuris muris. The animal intranasal immunization with rPP2A-OVS showed a reduction of 99.01% in the number of the nematode eggs and 97.90% in adult. The immunohistochemical analysis of the intestinal sections showed that in immunized animals with lipopeptide the mucus was significantly higher than in the other experimental groups. Also, these animals presented significantly different chemokine, CCL20 and CCL11, levels. However, although the number and size of Tuft cells did not vary between groups, the intensity of fluorescence per cell was significant in the group immunized with the rPP2A-OVS. The results of the present study suggest that mice immunized with the lipopeptide are capable of activating a combined Th17/Th9 response. This strategy of immunization may be of great applicability not only in immunotherapy and immunoprophylaxis to control diseases caused by nematodes but also in pathologies necessitating action at the level of the Th9 response in the intestinal mucosa.

Papilloma-pseudovirus eradicates intestinal tumours and triples the lifespan of ApcMin/+ mice

Inducing tumour-specific adaptive immunity, such as cytotoxic T lymphocyte (CTL) response, can result in promising antitumour effect against several human malignancies, especially in combination with immune checkpoint blockade strategies. However, little is known whether activation of innate immunity can lead to direct tumoricidal effect. Here, we develop a papilloma pseudovirus-based oral immunotherapeutic approach that shows strong tumoricidal effects in the gut, resulting in an almost tripled lifespan of Apc^Min/+ mice (an animal model of human intestinal tumorigenesis). Mechanistically, these pseudoviruses activate the NLRP3 and AIM2 inflammasomes, leading to caspase-1-mediated tumour regression that is dependent on neither cytotoxic T lymphocytes nor humoral immune response. Blocking caspase-1 activation abrogated the therapeutic effects of the pseudoviruses. Thus, targeting innate immune sensors in tumours by the pseudoviruses might represent a strategy to treat intestinal tumours.

Isoliquiritigenin inhibits TNF-α-induced release of high-mobility group box 1 through activation of HDAC in human intestinal epithelial HT-29 cells

The suppression of pro-inflammatory cytokine-induced inflammation responses is an attractive pharmacological target for the development of therapeutic strategies for inflammatory bowel disease (IBD). In the present study, we evaluated the anti-inflammatory properties of flavonoid isoliquiritigenin (ISL) in intestinal epithelial cells and determined its mechanism of action. ISL suppressed the expression of inflammatory molecules, including IL-8, IL-1β and COX-2, in TNF-α-stimulated HT-29 cells. Moreover, ISL induced activation of Nrf2 and expression of its target genes, such as HO-1 and NQO1. ISL also inhibited the TNF-α-induced NF-κB activation in HT-29 cells. High-mobility group box 1 (HMGB1), which is one of the critical mediators of inflammation, is actively secreted from inflammatory cytokine-stimulated immune or non-immune cells. ISL inhibited HMGB1 secretion by preventing TNF-α-stimulated HMGB1 relocation, whereas the RNA and protein expression levels of cellular HMGB1 did not change in response to TNF-α or ISL. Moreover, we found that HMGB1 acetylation was associated with HMGB1 translocation to the cytoplasm and the extracellular release in TNF-α-stimulated HT-29 cells; however, ISL significantly decreased the amount of acetylated HMGB1 in both the cytoplasm and extracellular space of HT-29 cells. Histone deacetylase (HDAC) inhibition by Scriptaid abrogated ISL-induced HDAC activity and reversed the ISL-mediated decrease in acetylated HMGB1 release in TNF-α-stimulated HT-29 cells, suggesting that, at least in TNF-α-stimulated HT-29 cells, ISL suppresses acetylated HMGB1 release via the induction of HDAC activity. Together, the current results suggest that inhibition of HMGB1 release via the induction of HDAC activity using ISL may be a promising therapeutic intervention for IBD.

Immunity to gastrointestinal microparasites of fish

Fish intestinal parasites cause direct mortalities and also morbidity, poor growth, higher susceptibility to opportunistic pathogens and lower resistance to stress. This review is focused on microscopic parasites (Protozoa and Metazoa) that invade the gastrointestinal tract of fish. Intracellular parasites (mainly Microsporidia and Apicomplexa) evoke almost no host immune reaction while they are concealed in the cytoplasmic and nuclear compartments, and can even use fish cells (macrophages) as Trojan horses to spread in the host. Inflammatory reaction only appears when the parasite bursts infected cells. Immunity against extracellular parasites is depicted for the myxozoans Ceratonova shasta and Enteromyxum spp. The cellular and humoral innate responses and the production of antibodies are crucial for resolving some of these myxozoonoses, but an excessive inflammatory reaction (concerted by cytokines) can become a fatal pathophysiological consequence. The local immune response plays a key role, with numerous genes more strongly regulated in the intestine than at lymphohaematopoietic organs.

Intestinal Epithelial Cell-Intrinsic Deletion of Setd7 Identifies Role for Developmental Pathways in Immunity to Helminth Infection

The intestine is a common site for a variety of pathogenic infections. Helminth infections continue to be major causes of disease worldwide, and are a significant burden on health care systems. Lysine methyltransferases are part of a family of novel attractive targets for drug discovery. SETD7 is a member of the Suppressor of variegation 3-9-Enhancer of zeste-Trithorax (SET) domain-containing family of lysine methyltransferases, and has been shown to methylate and alter the function of a wide variety of proteins in vitro. A few of these putative methylation targets have been shown to be important in resistance against pathogens. We therefore sought to study the role of SETD7 during parasitic infections. We find that Setd7-/- mice display increased resistance to infection with the helminth Trichuris muris but not Heligmosomoides polygyrus bakeri. Resistance to T. muris relies on an appropriate type 2 immune response that in turn prompts intestinal epithelial cells (IECs) to alter differentiation and proliferation kinetics. Here we show that SETD7 does not affect immune cell responses during infection. Instead, we found that IEC-specific deletion of Setd7 renders mice resistant to T. muris by controlling IEC turnover, an important aspect of anti-helminth immune responses. We further show that SETD7 controls IEC turnover by modulating developmental signaling pathways such as Hippo/YAP and Wnt/β-Catenin. We show that the Hippo pathway specifically is relevant during T. muris infection as verteporfin (a YAP inhibitor) treated mice became susceptible to T. muris. We conclude that SETD7 plays an important role in IEC biology during infection.

Immunological aspects of intestinal mucus and mucins

A number of mechanisms ensure that the intestine is protected from pathogens and also against our own intestinal microbiota. The outermost of these is the secreted mucus, which entraps bacteria and prevents their translocation into the tissue. Mucus contains many immunomodulatory molecules and is largely produced by the goblet cells. These cells are highly responsive to the signals they receive from the immune system and are also able to deliver antigens from the lumen to dendritic cells in the lamina propria. In this Review, we will give a basic overview of mucus, mucins and goblet cells, and explain how each of these contributes to immune regulation in the intestine.

Type 3 muscarinic receptors contribute to intestinal mucosal homeostasis and clearance of Nippostrongylus brasiliensis through induction of TH2 cytokines

Despite increased appreciation for the role of nicotinic receptors in the modulation of and response to inflammation, the contribution of muscarinic receptors to mucosal homeostasis, clearance of enteric pathogens, and modulation of immune cell function remains relatively undefined. Uninfected and Nippostrongylus brasiliensis-infected wild-type and type 3 muscarinic receptor (M3R)-deficient (Chrm3(-/-)) mice were studied to determine the contribution of M3R to mucosal homeostasis as well as host defense against the TH2-eliciting enteric nematode N. brasiliensis Intestinal permeability and expression of TH1/TH17 cytokines were increased in uninfected Chrm3(-/-) small intestine. Notably, in Chrm3(-/-) mice infected with N. brasiliensis, small intestinal upregulation of TH2 cytokines was attenuated and nematode clearance was delayed. In Chrm3(-/-) mice, TH2-dependent changes in small intestinal function including smooth muscle hypercontractility, increased epithelial permeability, decreased epithelial secretion and absorption, and goblet cell expansion were absent despite N. brasiliensis infection. These findings identify an important role for M3R in host defense and clearance of N. brasiliensis, and support the expanding role of cholinergic muscarinic receptors in maintaining mucosal homeostasis.

The role of evolutionary biology in research and control of liver flukes in Southeast Asia

Stimulated largely by the availability of new technology, biomedical research at the molecular-level and chemical-based control approaches arguably dominate the field of infectious diseases. Along with this, the proximate view of disease etiology predominates to the exclusion of the ultimate, evolutionary biology-based, causation perspective. Yet, historically and up to today, research in evolutionary biology has provided much of the foundation for understanding the mechanisms underlying disease transmission dynamics, virulence, and the design of effective integrated control strategies. Here we review the state of knowledge regarding the biology of Asian liver Fluke-host relationship, parasitology, phylodynamics, drug-based interventions and liver Fluke-related cancer etiology from an evolutionary biology perspective. We consider how evolutionary principles, mechanisms and research methods could help refine our understanding of clinical disease associated with infection by Liver Flukes as well as their transmission dynamics. We identify a series of questions for an evolutionary biology research agenda for the liver Fluke that should contribute to an increased understanding of liver Fluke-associated diseases. Finally, we describe an integrative evolutionary medicine approach to liver Fluke prevention and control highlighting the need to better contextualize interventions within a broader human health and sustainable development framework.

Transmissible Plasmid Containing Salmonella enterica Heidelberg Isolates Modulate Cytokine Production During Early Stage of Interaction with Intestinal Epithelial Cells

The variation in cytokine production during bacterial invasion of human intestinal epithelial cells (IECs) is a contributing factor for progression of the infection. A few Salmonella enterica Heidelberg strains isolated from poultry products harbor transmissible plasmids (TPs), including those that encode a type-IV secretion system. Earlier, we showed that these TPs are responsible for increased virulence during infection. This study examines the potential role of these TPs in cytokine production in IECs. This study showed that S. Heidelberg strains containing TPs (we refer as virulent strains) caused decreased interleukin (IL)-10 production in IECs after 1 h infection. The virulent strains induced a high level of tumor necrosis factor-α production under identical conditions. The virulent strains of S. Heidelberg also altered the production of IL-2, IL-17, and granulocyte macrophage colony-stimulating factor compared to an avirulent strain. As a part of infection, bacteria cross the epithelial barrier and encounter intestinal macrophages. Hence, we examined the cytotoxic mechanism of strains of S. Heidelberg in macrophages. Scanning electron microscopy showed cell necrosis occurs during the early stage of infection. In conclusion, virulent S. Heidelberg strains were able to modify the host cytokine profile during the early stages of infection and also caused necrosis in macrophages.

Helminths and the microbiota: parts of the hygiene hypothesis

In modern societies, diseases that are driven by dysregulated immune responses are increasing at an alarming pace, such as inflammatory bowel diseases and diabetes. There is an urgent need to understand these epidemiological trends, which are likely to be driven by the changing environment of the last few decades. There are complex interactions between human genetic factors and this changing environment that is leading to the increasing prevalence of metabolic and inflammatory diseases. Alterations to human gut bacterial communities (the microbiota) and lowered prevalence of helminth infections are potential environmental factors contributing to immune dysregulation. Helminths have co-evolved with the gut microbiota and their mammalian hosts. This three-way interaction is beginning to be characterized, and the knowledge gained may enable the design of new therapeutic strategies to treat metabolic and inflammatory diseases. However, these complex interactions need to be carefully investigated in the context of host genetic backgrounds to identify optimal treatment strategies. The complex nature of these interactions raises the possibility that only with highly personalized treatment, with knowledge of individual genetic and microbiota communities, will therapeutic interventions be successful for a majority of the individuals suffering from these complex diseases of immune dysregulation.

Type 2 immunity-dependent reduction of segmented filamentous bacteria in mice infected with the helminthic parasite Nippostrongylus brasiliensis

BACKGROUND

Dynamic interactions between the host and gastrointestinal microbiota play an important role for local and systemic immune homeostasis. Helminthic parasites modulate the host immune response, resulting in protection against autoimmune disease but also increased susceptibility to pathogen infection. The underlying mechanisms remain largely unknown.

RESULTS

We showed that the type 2 immune response to enteric Nippostrongylus brasiliensis infection in mice was associated with altered intestinal mucin and AMP expression and shifts in microbiota composition. Most strikingly, infection reduced concentrations of intestinal segmented filamentous bacteria (SFB), known inducers of T helper 17 cells, and IL-17-associated gene expression. Infected mice deficient in IL-13 or STAT6 did not reduce SFB or IL-17, and exogenous IL-25 replicated the effects of parasite infection in wild type mice.

CONCLUSIONS

Our data show that parasite infection acts through host type 2 immunity to reduce intestinal SFB and expression of IL-17, providing an example of a microbiota-dependent immune modulation by parasites.

Short communication: Experimental toxocarosis in Chinese Kun Ming mice: Dose-dependent larval distribution and modulation of immune responses

Toxocarosis is an important parasitic zoonosis which is mainly caused by the infective larvae of Toxocara canis. To identify whether there are correlations among the infectious dose, the larval migrans and immune modulation in inbred Chinese Kun Ming (KM) mice, experimental infections were carried out with a range of dosages of 100, 500, 1000, 2000, and 3000 embryonated eggs (EE). Pathogenic reactions were observed in terms of physical and central nervous symptoms. Distributions of T. canis larvae in liver, lung, kidney, heart and brain organs were respectively detected by scanning tissue sections. Moreover, quantitative real-time PCR was employed to identify the variations of Th2 immune response. The results showed that high inocula resulted in advanced larval emergences and arrested migrations in liver, lung, kidney and brain. However, no larvae were found in any of the histological sections of heart tissues. Higher levels of interleukin (IL)-4, IL-5, and IL-10 were detected along with the increasing inoculation doses, but the heaviest inoculum (3000 EE in this study) resulted in the sharp reduction of these ILs. Although no neurological symptoms or mortalities were noticed, these results indicated dose-dependent distribution patterns and immune regulations of T. canis larvae infection in KM mice.