An increase in epithelial cell apoptosis is associated with chronic intestinal nematode infection

Nematode Galectin Inhibits Basophilic Leukaemia RBL-2H3 Cells Apoptosis in IgE-Mediated Activation

Mast cells are essential immune cells involved in the host's defence against gastrointestinal nematodes. To evade the immune response, parasitic nematodes produce a variety of molecules. Galectin 1, produced by Teladorsagia circumcincta (Tci-gal-1), reduces mast cell degranulation and selectively regulates mediator production and release in an IgE-dependent manner. To uncover the activity of Tci-gal-1, we have examined the effect of the protein on gene expression, protein production, and apoptosis in activated basophilic leukaemia RBL-2H3 cells. Rat RBL-2H3 cells were activated with anti-DNP IgE and DNP-HSA, and then treated with Tci-gal-1. Microarray analysis was used to examine gene expression. The levels of several apoptosis-related molecules and cytokines were determined using antibody arrays and ELISA. Early and late apoptosis was evaluated cytometrically. Degranulation of cells was determined by a β-hexosaminidase release assay. Treatment of activated RBL-2H3 cells with Tci-gal-1 resulted in inhibited apoptosis and decreased degranulation, although we did not detect significant changes in gene expression. The production of pro-apoptotic molecules, receptor for advanced glycation end products (RAGE) and Fas ligand (FasL), and the cytokines IL-9, IL-10, IL-13, TNF-α, and IL-2 was strongly inhibited. Tci-gal-1 modulates apoptosis, degranulation, and production of cytokines by activated RBL-2H3 cells without detectable influence on gene transcription. This parasite protein is crucial for modulation of the protective immune response and the inhibition of chronic inflammation driven by mast cell activity.

Macrophage Migration Inhibitory Factor on Apoptotic Extracellular Vesicles Regulates Compensatory Proliferation

Apoptotic cells can signal to neighboring cells to stimulate proliferation and compensate for cell loss to maintain tissue homeostasis. While apoptotic cell-derived extracellular vesicles (AEVs) can transmit instructional cues to mediate communication with neighboring cells, the molecular mechanisms that induce cell division are not well understood. Here we show that macrophage migration inhibitory factor (MIF)-containing AEVs regulate compensatory proliferation via ERK signaling in epithelial stem cells of larval zebrafish. Time-lapse imaging showed efferocytosis of AEVs from dying epithelial stem cells by healthy neighboring stem cells. Proteomic and ultrastructure analysis of purified AEVs identified MIF localization on the AEV surface. Pharmacological inhibition or genetic mutation of MIF, or its cognate receptor CD74, decreased levels of phosphorylated ERK and compensatory proliferation in the neighboring epithelial stem cells. Disruption of MIF activity also caused decreased numbers of macrophages patrolling near AEVs, while depletion of the macrophage lineage resulted in a reduced proliferative response by the epithelial stem cells. We propose that AEVs carrying MIF directly stimulate epithelial stem cell repopulation and guide macrophages to cell non-autonomously induce localized proliferation to sustain overall cell numbers during tissue maintenance.

Garlic-derived organosulfur compounds regulate metabolic and immune pathways in macrophages and attenuate intestinal inflammation in mice

Scope: Garlic is a source of bioactive phytonutrients that may have anti‐inflammatory or immunomodulatory properties. The mechanism(s) underlying the bioactivity of these compounds and their ability to regulate responses to enteric infections remains unclear.

Methods and Results: This study investigates if a garlic‐derived preparation (PTSO‐PTS) containing two organosulfur metabolites, propyl‐propane thiosulfonate (PTSO), and propyl‐propane thiosulfinate (PTS), regulate inflammatory responses in murine macrophages and intestinal epithelial cells (IEC) in vitro, as well as in a model of enteric parasite‐induced inflammation. PTSO‐PTS decreases lipopolysaccharide‐induced secretion of TNFα, IL‐6, and IL‐27 in macrophages. RNA‐sequencing demonstrates that PTSO‐PTS strongly suppresses pathways related to immune and inflammatory signaling. PTSO‐PTS induces the expression of a number of genes involved in antioxidant responses in IEC during exposure to antigens from the parasite Trichuris muris. In vivo, PTSO‐PTS does not affect T. muris establishment or intestinal T‐cell responses but significantly alters cecal transcriptomic responses. Notably, a reduction in T. muris‐induced expression of Tnf, Saa2, and Nos2 is observed.

Conclusion: Garlic‐derived organosulfur compounds exert anti‐inflammatory effects in macrophages and IEC, and regulate gene expression during intestinal infection. These compounds and related organic molecules may thus hold potential as functional food components to improve gut health in humans and animals.

Enterocyte-innate lymphoid cell crosstalk drives early IFN-γ-mediated control of Cryptosporidium

The intestinal parasite, Cryptosporidium, is a major contributor to global child mortality and causes opportunistic infection in immune deficient individuals. Innate resistance to Cryptosporidium, which specifically invades enterocytes, is dependent on the production of IFN-γ, yet whether enterocytes contribute to parasite control is poorly understood. In this study, utilizing a mouse-adapted strain of C. parvum, we show that epithelial-derived IL-18 synergized with IL-12 to stimulate innate lymphoid cell (ILC) production of IFN-γ required for early parasite control. The loss of IFN-γ-mediated STAT1 signaling in enterocytes, but not dendritic cells or macrophages, antagonized early parasite control. Transcriptional profiling of enterocytes from infected mice identified an IFN-γ signature and enrichment of the anti-microbial effectors IDO, GBP, and IRG. Deletion experiments identified a role for Irgm1/m3 in parasite control. Thus, enterocytes promote ILC production of IFN-γ that acts on enterocytes to restrict the growth of Cryptosporidium.

Management of cell death in parasitic infections

For a long time, host cell death during parasitic infection has been considered a reflection of tissue damage, and often associated with disease pathogenesis. However, during their evolution, protozoan and helminth parasites have developed strategies to interfere with cell death so as to spread and survive in the infected host, thereby ascribing a more intriguing role to infection-associated cell death. In this review, we examine the mechanisms used by intracellular and extracellular parasites to respectively inhibit or trigger programmed cell death. We further dissect the role of the prototypical “eat-me signal” phosphatidylserine (PtdSer) which, by being exposed on the cell surface of damaged host cells as well as on some viable parasites via a process of apoptotic mimicry, leads to their recognition and up-take by the neighboring phagocytes. Although barely dissected so far, the engagement of different PtdSer receptors on macrophages, by shaping the host immune response, affects the overall infection outcome in models of both protozoan and helminth infections. In this scenario, further understanding of the molecular and cellular regulation of the PtdSer exposing cell-macrophage interaction might allow the identification of new therapeutic targets for the management of parasitic infection.

Morphological variability in the mucosal attachment site of Trichuris muris revealed by X-ray microcomputed tomography

Parasitic infections can be challenging to study because two dimensional light and electron microscopy are often limited in visualising complex and inaccessible attachment sites. Exemplifying this, Trichuris spp. inhabit a tunnel of epithelial cells within the host caecum and colon. A significant global burden of this infection persists, partly because available anthelminthics lack efficacy, although the mechanisms underlying this remain unknown. Consequently, there is a need to pioneer new approaches to better characterize the parasite niche within the host and investigate how variation in its morphology and integrity may contribute to resistance to therapeutic intervention. To address these aims, we exploited three-dimensional X-ray micro-computed tomography (microCT) to image the mouse whipworm, Trichuris muris, in caeca of wild-type C57BL/6 and SCID mice ex vivo. Using osmium tetroxide staining to effectively enhance the contrast of worms, we found that a subset exhibited preferential positioning towards the bases of the intestinal crypts. Moreover, in one rare event, we demonstrated whipworm traversal of the lamina propria. This morphological variability contradicts widely accepted conclusions from conventional microscopy of the parasite niche, showing Trichuris in close contact with the host proliferative and immune compartments that may facilitate immunomodulation. Furthermore, by using a skeletonization-based approach we demonstrate considerable variation in tunnel length and integrity. The qualitative and quantitative observations provide a new morphological point of reference for future in vitro study of host-Trichuris interactions, and highlight the potential of microCT to characterise enigmatic host-parasite interactions more accurately.

Trichuris muris and comorbidities - within a mouse model context

Trichuris muris is a mouse intestinal parasitic nematode that inhabits the large intestine of its host and induces a strong immune response. The effects of this strong anti-parasite response can be found locally within the intestinal niche and also systemically, having effects on multiple organs. Additionally, the anti-parasite response can have multiple effects on infectious organisms and on microbiota that the host is harbouring. It has been shown that Th1 responses induced by T. muris can affect progression of bowel inflammation, cause colitic-like intestinal inflammation, reduce barrier function and intestinal mucosal responses. In the brain, T. muris can exacerbate stroke outcome and other neurological conditions. In the lung, T. muris can suppress airway inflammation and alter immune responses to other parasites. Additionally, T. muris induced responses can inhibit anti-tumour immunity. Although this parasite maintains a localized niche in the large intestine, its effects can be far-reaching and substantially impact other infections through modulation of bystander immune responses.

Oxidative stress mediated apoptotic potential of mefloquine on experimental trichinellosis

Conventional anthelmintics such as albendazole could not achieve complete cure of trichinellosis till now. The antimalarial mefloquine mediates oxidative stress and disrupts lysosomal functions leading to cell death. Therefore, the aim of this work was to investigate the effect of mefloquine on experimental acute and chronic trichinellosis and to clarify the possible mechanisms of such effects. Mice were divided into four groups; Group I: Uninfected untreated control (20 mice); Group II: Infected untreated control (40 mice); Group III: infected and treated with albendazole (400 mg/kg) (40 mice); Group IV: infected and treated with mefloquine (300 mg/kg) (40 mice). All infected treated groups were equally subdivided into 2 subgroups; (a) treated on the 2^nd day post infection (dpi) for 3 days, (b) treated on the 35^th dpi for 5 days. Parasitological adults and larvae counting besides immunohistopathological examination of intestines and muscles were done. Biochemical assay of oxidant/antioxidant status, apoptotic, cytoprotective and inflammatory biomarkers in intestinal and muscle homogenates were achieved. Results showed that both albendazole and mefloquine significantly reduced adults and larvae counts with higher efficacy of albendazole in the intestinal phase and superiority of mefloquine in the muscle phase. The superiority of mefloquine was indicated by increased inflammatory immune infiltration and decreased anti-apoptotic immunohistochemical markers expression in both jejunal and muscle tissues. Biochemically, mefloquine treatment showed highly significant oxidative, apoptotic and inflammatory effects. So, our results suggest that mefloquine might be a superior treatment for chronic trichinellosis.

Non-neoplastic colorectal disease biopsies: evaluation and differential diagnosis

A wide variety of non-neoplastic conditions may be encountered on colorectal biopsy encompassing idiopathic, infectious, vascular and immune-mediated aetiologies. Although interpretation of such biopsies may be challenging, appreciation of the dominant pattern of injury and subsequent host response may allow for a more focused histological diagnosis in the correct clinical and endoscopic setting. This article aims to provide a systematic, methodical approach to the assessment of such biopsies, concentrating mainly on diagnoses other than inflammatory bowel disease.

The Intestinal Epithelium at the Forefront of Host-Helminth Interactions

Gastrointestinal helminth infection still constitutes a major public health issue, particularly in the developing world. As these parasites can undergo a large part of their lifecycle within the intestinal tract the host has developed various structural and cellular specializations at the epithelial barrier to contend with infection. Detailed characterization of these cells will provide important insights about their contributions to the protective responses mediated against helminths. Here, we discuss how key components of the intestinal epithelium may function to limit the initial establishment of helminths, and how these cells are altered during an active response to infection.

The influence of selected gastrointestinal parasites on apoptosis in intestinal epithelial cells

Studies on the parasite–host interaction may provide valuable information concerning the modulation of molecular mechanisms as well as of the host immune system during infection. To date, it has been demonstrated that intestinal parasites may affect, among others, the processes of digestion in the gastrointestinal system of the host, thus limiting the elimination of the parasite, the immune response as well as inflammation. However, the most recent studies suggest that intestinal parasites may also affect modulation of the apoptosis pathway of the host. The present paper presents the latest scientific information on the influence of intestinal parasite species (Blastocystis sp., Giardia sp., Cryptosporidium sp., Trichuris sp., Entamoeba histolytica, Nippostrongylus brasiliensis, Heligmosomoides polygyrus) on the molecular mechanisms of apoptosis in intestinal epithelial cells. This paper stresses that the interdependency between the intestinal parasite and the host results from the direct effect of the parasite and the host’s defense reactions, which lead to modulation of the apoptosis pathways (intrinsic and extrinsic). Moreover, the present paper presents the role of proteins involved in the mechanisms of apoptosis as well as the physiological role of apoptosis in the host’s intestinal epithelial cells.

TNFAIP8 Deficiency Exacerbates Acute Graft Versus Host Disease in a Murine Model of Allogeneic Hematopoietic Cell Transplantation

BACKGROUND

Gastrointestinal acute graft-versus-host disease (GVHD) occurring after allogeneic hematopoietic cell transplant is an allo-reactive T cell and inflammatory cytokine driven organ injury with epithelial apoptosis as 1 of its hallmark findings and is associated with significant mortality. Tumor necrosis factor (TNF)-alpha-induced protein 8 (TNFAIP8 or TIPE) acts as a negative mediator of apoptosis via inhibition of caspase-3 activation, promotes cell proliferation and Tipe deficiency is associated with increased inflammation.

METHODS

To evaluate the role of TIPE in acute GVHD, naive C57BL/6 and Tipe C57BL/6 mice were conditioned with 1000 cGy single dose total body irradiation, followed by transplantation of 10 million bone marrow cells and 20 million splenocytes from either syngeneic C57BL/6 or allogeneic BALB/c donors.

RESULTS

Allo TIPE-deficient mice developed exacerbated gut GVHD compared with allo controls and had significantly decreased survival (6 wk overall survival: 85% versus 37%; P < 0.05), higher clinical GVHD scores, more profound weight loss, increased serum proinflammatory cytokines (interleukin-17A, TNF, interleukin-6, and interferon-γ). T-cell infiltration into the ileum was increased; epithelial proliferation was decreased along with significantly higher levels of chemokines KC and monokine induced by gamma interferon. Using bone marrow chimeric experiments, TIPE was found to have a role in both hematopoietic and nonhematopoietic cells.

CONCLUSIONS

Absence of TIPE results in excessive inflammation and tissue injury after allo-HCT, supporting that TIPE confers immune homeostasis and has tissue-protective function during the development of gut GVHD and may be a potential future target to prevent or treat this complication after allogeneic HCT.

Host-Parasite Interactions Promote Disease Tolerance to Intestinal Helminth Infection

Parasitic helminths are among the most pervasive pathogens of the animal kingdom. To complete their life cycle, these intestinal worms migrate through host tissues causing significant damage in their wake. As a result, infection can lead to malnutrition, anemia and increased susceptibility to co-infection. Despite repeated deworming treatment, individuals living in endemic regions remain highly susceptible to re-infection by helminths, but rarely succumb to excessive tissue damage. The chronicity of infection and inability to resist numerous species of parasitic helminths that have co-evolved with their hosts over millenia suggests that mammals have developed mechanisms to tolerate this infectious disease. Distinct from resistance where the goal is to destroy and eliminate the pathogen, disease tolerance is an active process whereby immune and structural cells restrict tissue damage to maintain host fitness without directly affecting pathogen burden. Although disease tolerance is evolutionary conserved and has been well-described in plant systems, only recently has this mode of host defense, in its strictest sense, begun to be explored in mammals. In this review, we will examine the inter- and intracellular networks that support disease tolerance during enteric stages of parasitic helminth infection and why this alternative host defense strategy may have evolved to endure the presence of non-replicating pathogens and maintain the essential functions of the intestine.

Helminth-induced apoptosis: a silent strategy for immunosuppression

During microbial infections, both innate and adaptive immunity are activated. Viruses and bacteria usually induce an acute inflammation in the first setting of infection, which helps the eliciting an effective immune response. In contrast, macroparasites such as helminths are a highly successful group of invaders known to be capable of maintaining a chronic infestation with the minimum instigation. Undoubtedly, generating such an immunoregulatory environment requires the exploitation of various immunosuppressive mechanisms to debilitate host immunity supporting their survival and replication. Several mechanisms have been recognized whereby helminths prolong their infections including an increase of immunoregulatory cells, inhibition of Th1 or Th2 responses, targeting pattern recognition receptors (PRRs) and lowering the immune cells quantity via induction of apoptosis. Apoptosis is a programmed intracellular process involving a series of consecutive downstream signalling event evolved to cell death. It plays a pivotal role in several immunological reactions in particular deletion of autoreactive immune cells. Helminth-triggered apoptosis in immune cells exhausts host immunity, which paves the way for generating a permissive environment and chronic infection. This review provides a compilation of recent investigations discussing the apoptotic mechanisms exploited by different worms and the immunological consequences of immune cell death. Finally, the anti-cancer effects of some worm-derived molecules due to their apoptotic effects are discussed, highlighting as potentially druggable candidates to combat cancer.

Chronic Trichuris muris infection causes neoplastic change in the intestine and exacerbates tumour formation in APC min/+ mice

Incidences of infection-related cancers are on the rise in developing countries where the prevalence of intestinal nematode worm infections are also high. Trichuris muris (T. muris) is a murine gut-dwelling nematode that is the direct model for human T. trichiura, one of the major soil-transmitted helminth infections of humans. In order to assess whether chronic infection with T. muris does indeed influence the development of cancer hallmarks, both wild type mice and colon cancer model (APC ^min/+) mice were infected with this parasite. Parasite infection in wild type mice led to the development of neoplastic change similar to that seen in mice that had been treated with the carcinogen azoxymethane. Additionally, both chronic and acute infection in the APC^min/+ mice led to an enhanced tumour development that was distinct to the site of infection suggesting systemic control. By blocking the parasite induced T regulatory response in these mice, the increase in the number of tumours following infection was abrogated. Thus T. muris infection alone causes an increase in gut pathologies that are known to be markers of cancer but also increases the incidence of tumour formation in a colon cancer model. The influence of parasitic worm infection on the development of cancer may therefore be significant.

It is estimated that now 2 billion people currently live with chronic parasitic worm infections. As the incidences of cancer increase worldwide, the importance of these chronic inflammatory conditions on the development of cancer becomes more important. Several bacterial, viral and parasitic infections are already known to influence cancer development but as colon cancer is particularly prevalent worldwide, we wanted to assess the effect of a large intestinal dwelling worm, Trichuris muris (T. muris) on its aetiology. This whipworm is a natural infection of mice and has significant homology to human whipworm. From our studies, we showed that chronic infection alone induced changes in the caecum of the mouse that were comparable to those seen with a well-known carcinogen. In addition to this, T. muris infection was also able to increase the development of adenomas in the small intestine of mutant mice that spontaneously develop tumours. This change was abrogated if a T regulatory cell type was blocked during infection. The T regulatory cell type that arises during infection has been shown to play an important role in protecting the host from damage caused by the parasite and the immune response to it. The present study using the mouse model however, suggests that regulatory T cells can have negative effects, at least in terms of the development of bowel cancer. As so many people live with chronic, regulated parasitic infections, the importance of the parasites in cancer development may therefore be significant.

Subcutaneous injection of exosomes reduces symptom severity and mortality induced by Echinostoma caproni infection in BALB/c mice

Recent studies have shown the importance of exosomes in the host-parasite relationship. These vesicles are an important part of the excretory/secretory pathway for proteins with the potential to alter immune responses. Therefore, in the present study, we examined the immunomodulatory role of exosomes in BALB/c mice using Echinostoma caproni as an experimental model of intestinal helminth infection. For this purpose, BALB/c mice were injected twice s.c. with purified exosomes of E. caproni, followed by experimental infection. We report a delay in the development of the parasite in mice immunised with exosomes, a concomitant reduced symptom severity and increased survival upon infection. Immunisations with exosomes evoked systemic antibody responses with high levels of IgM and IgG. IgG1, IgG2b and IgG3 are the subtypes responsible for the IgG increase. These antibodies showed specific recognition of exosomal proteins, indicating that these vesicles carry specific antigens that are involved in the humoral response. The administration of exosomes induced an increase of IFN-γ, IL-4 and TGF-β levels in the spleen of mice prior to infection. The subsequent infection with E. caproni resulted in a further increase of IL-4 and TGF-β, together with an abrupt overproduction of IL-10, suggesting the development of a Th2/Treg immune response. Our results show that the administration of exosomes primes the immune response in the host, which in turn can contribute to tolerance of the invader, reducing the severity of clinical signs in E. caproni infection.

Resistance against Echinostoma caproni (Trematoda) secondary infections in mice is not dependent on the ileal protein production

Echinostoma caproni (Trematoda: Echinostomatidae) is an intestinal trematode, which has been widely employed to investigate the factors determining the rejection of intestinal helminths. Protein production patterns of intestinal epithelial cells are related to the infection-induced changes that determine the course of E. caproni infections. Herein, we compare the protein production profiles in the ileum of four experimental groups of mice: control; infected; dewormed and reinfected. Worm burdens were significantly lower in secondary infections, confirming the generation of partial resistance to homologous secondary infections in mice. However, quantitative comparison by 2D-DIGE showed that the protein production profile is similar in control and dewormed mice, and after primary and secondary E. caproni infections. These results showed that, unexpectedly, protein production changes in E. caproni infections are not responsible of resistance development. Fifty-one protein spots were differentially produced between control/treated and infected/reinfected mice and 37 of them were identified by mass spectrometry. The analysis of differentially abundant proteins indicate that cell metabolism and the regulation of proliferation and cell death are the most affected processes after primary and secondary E. caproni infections. These results provide new insights into the proteins involved in the regulation of tissue homeostasis after intestinal infection.

SIGNIFICANCE

Intestinal helminthiases are highly prevalent parasitic infections with about 1 billion people infected worldwide. In this scenario, better understanding of host-parasite relationships is needed to elucidate the factors that determine intestinal helminth rejection. The intestinal trematode Echinostoma caproni has been broadly employed in this field, with resistance against secondary homologous infections reported in mice. In this paper, new insights are provided in the regulation of tissue homeostasis after intestinal infection. The unexpected lack of an altered pattern of ileal protein production associated to resistance development suggests that this resistance depends on rapid changes, affecting the early establishment of worms, rather than the activation of later effector mechanisms. These results may contribute to the development of new control tools for the management of these parasitic infections.

ALCAM is a Novel Cytoplasmic Membrane Protein in TNF-α Stimulated Invasive Cholangiocarcinoma Cells

BACKGROUND

Cholangiocarcinoma (CCA), or bile duct cancer, is incurable with a high mortality rate due to a lack of effective early diagnosis and treatment. Identifying cytoplasmic membrane proteins of invasive CCA that facilitate cancer progression would contribute toward the development of novel tumor markers and effective chemotherapy.

MATERIALS AND METHODS

An invasive CCA cell line (KKU-100) was stimulated using TNF-α and then biotinylated and purified for mass spectrometry analysis. Novel proteins expressed were selected and their mRNAs expression levels were determined by real-time RT-PCR. In addition, the expression of ALCAM was selected for further observation by Western blot analysis, immunofluorescent imaging, and antibody neutralization assay.

RESULTS

After comparing the proteomics profile of TNF-α induced invasive with non-treated control cells, over-expression of seven novel proteins was observed in the cytoplasmic membrane of TNF-α stimulated CCA cells. Among these, ALCAM is a novel candidate which showed significant higher mRNA- and protein levels. Immunofluorescent assay also supported that ALCAM was expressed on the cell membrane of the cancer, with increasing intensity associated with TNF-α.

CONCLUSIONS

This study indicated that ALCAM may be a novel protein candidate expressed on cytoplasmic membranes of invasive CCA cells that could be used as a biomarker for development of diagnosis, prognosis, and drug or antibody-based targeted therapies in the future.

Altered Protein Expression in the Ileum of Mice Associated with the Development of Chronic Infections with Echinostoma caproni (Trematoda)

Background

Echinostoma caproni (Trematoda: Echinostomatidae) is an intestinal trematode that has been extensively used as experimental model to investigate the factors determining the expulsion of intestinal helminths or, in contrast, the development of chronic infections. Herein, we analyze the changes in protein expression induced by E. caproni infection in ICR mice, a host of high compatibility in which the parasites develop chronic infections.

Methodology/Principal Findings

To determine the changes in protein expression, a two-dimensional DIGE approach using protein extracts from the intestine of naïve and infected mice was employed; and spots showing significant differential expression were analyzed by mass spectrometry. A total of 37 spots were identified differentially expressed in infected mice (10 were found to be over-expressed and 27 down-regulated). These proteins were related to the restoration of the intestinal epithelium and the control of homeostatic dysregulation, concomitantly with mitochondrial and cytoskeletal proteins among others.

Conclusion/Significance

Our results suggests that changes in these processes in the ileal epithelium of ICR mice may facilitate the establishment of the parasite and the development of chronic infections. These results may serve to explain the factors determining the development of chronicity in intestinal helminth infection.

Intestinal helminth infections are among the most prevalent parasitic diseases and about 1 billion people are currently infected with intestinal helminths. Incidence of intestinal helminth infections is high due to both socio-economic factors that facilitates continuous re-infections and the lack of effective vaccines. In this context, further knowledge on the host-parasite relationships is required to elucidate the factors that determine the expulsion of the intestinal helminths or, in contrast, the chronic establishment of the infections. Echinostoma caproni (Trematoda) is an intestinal trematode that has been extensively used as experimental model to investigate these factors. Depending on the host species. E. caproni is rapidly rejected or develops chronic infections. Herein, we analyze the changes in protein expression induced by E. caproni infection in a host in which the parasites develop chronic infections. These data may serve to get a better understanding of the factors determining the development of chronic intestinal infections. A total of 37 spots were identified differentially expressed. These proteins were related to the restoration of the intestinal epithelium and the control of homeostatic dysregulation, mitochondrial and cytoskeletal proteins among others. This suggests that the changes in these processes in the intestinal mucosa may facilitate the development of chronic infections.

Blocking peripheral serotonin synthesis by telotristat etiprate (LX1032/LX1606) reduces severity of both chemical- and infection-induced intestinal inflammation

Mucosal inflammation is accompanied by an alteration in 5-HT. Intestinal 5-HT synthesis is catalyzed by tryptophan hydroxylase 1 (Tph1) and we have shown that mice deficient in this rate-limiting enzyme have reduced severity of intestinal inflammation in models of chemical-induced experimental colitis. Here, we investigated the effect of blocking peripheral 5-HT synthesis in generation of intestinal inflammation by a using peripheral Tph inhibitor, telotristat etiprate (LX1606), in models of intestinal inflammation. LX1606 was given orally either prophylactically or therapeutically to mice with dextran sulfate sodium (DSS)-induced colitis or with infection with Trichuris muris. Severity of intestinal inflammation was measured by assessment of disease activity scores, histological damage, and MPO and inflammatory cytokine levels. LX1606 significantly reduced intestinal 5-HT levels and delayed onset and severity of DSS-induced acute and chronic colitis. This was associated with decreased MPO and proinflammatory cytokine levels compared with vehicle-treated controls. In the infection-induced inflammation model, treatment with LX1606 enhanced worm expulsion as well as increased IL-10 production and goblet cell numbers. LX1606-treated mice had significantly lower MPO and IL-1β levels compared with controls postinfection. Our results demonstrate that peripheral 5-HT plays an important role in intestinal inflammation and in the generation of immune responses. Pharmacological reduction of peripheral 5-HT may serve as a potential strategy for modulating various intestinal inflammatory disorders.

Intestine and multivisceral transplantation: current status and future directions

Intestinal failure and associated parenteral nutrition-induced liver failure cause significant morbidity, mortality, and health care burden. Intestine transplantation is now considered to be the standard of care in patients with intestinal failure who fail intestinal rehabilitation. Intestinal failure-associated liver disease is an important sequela of intestinal failure, caused by parenteral lipids, requiring simultaneous liver-intestine transplant. Lipid minimization and, in recent years, the emergence of fish oil-based lipid emulsions have been shown to reverse parenteral nutrition-associated hyperbilirubinemia, but not fibrosis. Significant progress in surgical techniques and immunosuppression has led to improved outcomes after intestine transplantation. Intestine in varying combination with liver, stomach, and pancreas, also referred to as multivisceral transplantation, is performed for patients with intestinal failure along with liver disease, surgical abdominal catastrophes, neuroendocrine and slow-growing tumors, and complete portomesenteric thrombosis with cirrhosis of the liver. Although acute and chronic rejection are major problems, long-term survivors have excellent quality of life and remain free of parenteral nutrition.

A role for the pattern recognition receptor Nod2 in promoting recruitment of CD103+ dendritic cells to the colon in response to Trichuris muris infection

The ability of the colon to generate an immune response to pathogens, such as the model pathogen Trichuris muris, is a fundamental and critical defense mechanism. Resistance to T. muris infection is associated with the rapid recruitment of dendritic cells (DCs) to the colonic epithelium via epithelial chemokine production. However, the epithelial-pathogen interactions that drive chemokine production are not known. We addressed the role of the cytosolic pattern recognition receptor Nod2. In response to infection, there was a rapid influx of CD103(+)CD11c(+) DCs into the colonic epithelium in wild-type (WT) mice, whereas this was absent in Nod2(-/-) animals. In vitro chemotaxis assays and in vivo experiments using bone marrow chimeras of WT mice reconstituted with Nod2(-/-) bone marrow and infected with T. muris demonstrated that the migratory function of Nod2(-/-) DCs was normal. Investigation of colonic epithelial cell (CEC) innate responses revealed a significant reduction in epithelial production of the chemokines CCL2 and CCL5 but not CCL20 by Nod2-deficient CECs. Collectively, these data demonstrate the importance of Nod2 in CEC responses to infection and the requirement for functional Nod2 in initiating host epithelial chemokine-mediated responses and subsequent DC recruitment and T-cell responses following infection.

Endoplasmic reticulum stress-mediated apoptosis is activated in intestines of mice with Trichinella spiralis infection

Gastrointestinal helminth infection, including Trichinella spiralis, initiates a series of intestinal structural, cellular and physiological changes. Intestinal invasion is an important stage of trichinellosis because it determines the development and subsequent course of the disease and its consequences. Apoptosis mediated by endoplasmic reticulum stress (ERS) plays a key role in infectious diseases, but the effect of T. spiralis infection on inducing apoptosis in the small intestine has been neglected. We investigated apoptosis and changes in ERS-associated apoptosis molecules in the intestine of mice with T. spiralis infection. TUNEL staining and detection of the apoptotic marker cleaved caspase 3 revealed that apoptosis occurred in the mouse intestine at days 3 and 7 post-infection. The ER chaperone 78-kDa glucose-regulated protein (GRP78) was upregulated at days 3 and 7 post-infection. The ERS-associated apoptosis molecules C/EBP homologous protein, cleaved caspase 12 and c-Jun NH2-terminal kinase were upregulated at days 3 and 7, days 3, 7 and 10 and days 7 and 10 post-infection, respectively. Thus, apoptosis occurred in the intestine of mice with T. spiralis infection, and the ERS-mediated apoptosis pathway was activated by infection with this small intestine dwelling nematode.

Sex-dependent genetic effects on immune responses to a parasitic nematode

BACKGROUND

Many disease aetiologies have sex specific effects, which have important implications for disease management. It is now becoming increasingly evident that such effects are the result of the differential expression of autosomal genes rather than sex-specific genes. Such sex-specific variation in the response to Trichuris muris, a murine parasitic nematode infection and model for the human parasitic nematode T. trichiura, has been well documented, however, the underlying genetic causes of these differences have been largely neglected. We used the BXD mouse set of recombinant inbred strains to identify sex-specific loci that contribute to immune phenotypes in T. muris infection.

RESULTS

Response phenotypes to T. muris infection were found to be highly variable between different lines of BXD mice. A significant QTL on chromosome 5 (TM5) associated with IFN-γ production was found in male mice but not in female mice. This QTL was in the same location as a suggestive QTL for TNF-α and IL-6 production in male mice suggesting a common control of these pro-inflammatory cytokines. A second QTL was identified on chromosome 4 (TM4) affecting worm burden in both male and female cohorts. We have identified several genes as potential candidates for modifying responses to T. muris infection.

CONCLUSIONS

We have used the largest mammalian genetic model system, the BXD mouse population, to identify candidate genes with sex-specific effects in immune responses to T. muris infection. Some of these genes may be differentially expressed in male and female mice leading to the difference in immune response between the sexes reported in previous studies. Our study further highlights the importance of considering sex as an important factor in investigations of immune response at the genome-wide level, in particular the bias that can be introduced when generalizing results obtained from only one sex or a mixed sex population. Rather, analyses of interaction effects between sex and genotype should be part of future studies.

Susceptibility to Salmonella carrier-state: a possible Th2 response in susceptible chicks

Infection of chicken with Salmonella may lead to a carrier-state characterized by the persistence of bacteria in the ceca for a long period of time and result in their excretion in feces. This excretion is the source of contamination of their congeners and food. During infection, enterocytes are the primary target cells for Salmonella, the producers of soluble factors which launch immune response and cells which are reciprocally responsive to surrounding immune cells. This study used microarrays to compare the gene expression profile during carrier-state of enterocytes purified from infected and control chicks which are either resistant or susceptible to Salmonella Enteritidis carrier-state. In total, we identified 271 genes significantly differentially expressed with an absolute fold change greater than 1.5. A global analysis determined interaction networks between differentially regulated genes. Using an a priori approach, our analyses focused on differentially expressed genes which were transcriptionally linked to cytokines playing a major role in the fate of the immune response. The expression of genes transcriptionally linked to type I interferon and TGF-β was down-regulated in infected chicks from both lines. Gene expression linked to the Th1 axis suggests the latter is inhibited in both lines. Finally, the expression of genes linked to IL-4, IL-5 and IL-13 indicates that susceptibility to carrier-state could be associated with a Th2 bias. Overall, these results highlight that the response to Salmonella during the acute phase and carrier-state is different and that enterocytes play a central role in this response.

Mycobacterium bovis BCG infection severely delays Trichuris muris expulsion and co-infection suppresses immune responsiveness to both pathogens

BACKGROUND

The global epidemiology of parasitic helminths and mycobacterial infections display extensive geographical overlap, especially in the rural and urban communities of developing countries. We investigated whether co-infection with the gastrointestinal tract-restricted helminth, Trichuris muris, and the intracellular bacterium, Mycobacterium bovis (M. bovis) BCG, would alter host immune responses to, or the pathological effect of, either infection.

RESULTS

We demonstrate that both pathogens are capable of negatively affecting local and systemic immune responses towards each other by modifying cytokine phenotypes and by inducing general immune suppression. T. muris infection influenced non-specific and pathogen-specific immunity to M. bovis BCG by down-regulating pulmonary TH1 and Treg responses and inducing systemic TH2 responses. However, co-infection did not alter mycobacterial multiplication or dissemination and host pulmonary histopathology remained unaffected compared to BCG-only infected mice. Interestingly, prior M. bovis BCG infection significantly delayed helminth clearance and increased intestinal crypt cell proliferation in BALB/c mice. This was accompanied by a significant reduction in systemic helminth-specific TH1 and TH2 cytokine responses and significantly reduced local TH1 and TH2 responses in comparison to T. muris-only infected mice.

CONCLUSION

Our data demonstrate that co-infection with pathogens inducing opposing immune phenotypes, can have differential effects on compartmentalized host immune protection to either pathogen. In spite of local and systemic decreases in TH1 and increases in TH2 responses co-infected mice clear M. bovis BCG at the same rate as BCG only infected animals, whereas prior mycobacterial infection initiates prolonged worm infestation in parallel to decreased pathogen-specific TH2 cytokine production.

Lactobacillus rhamnosus ingestion promotes innate host defense in an enteric parasitic infection

Enteric parasite infections around the world are a huge economic burden and decrease the quality of life for many people. The use of beneficial bacteria has attracted attention for their potential therapeutic applications in various diseases. However, the effects of beneficial bacteria in enteric parasitic infections remain largely unexplored. We investigated the effects of ingestion of Lactobacillus rhamnosus (JB-1) in a model of enteric nematode (Trichuris muris) infection. C57BL/6 (resistant to infection), AKR (susceptible to infection), interleukin 10 (IL-10) knockout (KO), and mucin Muc2 KO mice were infected with T. muris and treated orally with probiotic JB-1 or medium. The mice were sacrificed on various days postinfection to examine goblet cells, epithelial cell proliferation, cytokines, and worm burdens. Treatment with JB-1 significantly enhanced worm expulsion in resistant C57BL/6 mice, and this was associated with increases in IL-10 levels, goblet cell numbers, and epithelial cell proliferation. Beneficial effects of JB-1 were absent in IL-10 KO and resistant mice treated with γ-irradiated bacteria. Live JB-1 treatment also expedited worm expulsion in Muc2 KO mice and, more importantly, in AKR mice (susceptible to infection). Injection of IL-10 directly into the colonic tissue of uninfected mice induced goblet cell hyperplasia. These findings demonstrate that JB-1 modulates goblet cell biology and promotes parasite expulsion via an IL-10-mediated pathway and provide novel insights into probiotic effects on innate defense in nematode infection.

Trichuris muris: a model of gastrointestinal parasite infection

Infection with soil-transmitted gastrointestinal parasites, such as Trichuris trichiura, affects more than a billion people worldwide, causing significant morbidity and health problems especially in poverty-stricken developing countries. Despite extensive research, the role of the immune system in triggering parasite expulsion is incompletely understood which hinders the development of anti-parasite therapies. Trichuris muris infection in mice serves as a useful model of T. trichiura infection in humans and has proven to be an invaluable tool in increasing our understanding of the role of the immune system in promoting either susceptibility or resistance to infection. The old paradigm of a susceptibility-associated Th1 versus a resistance-associated Th2-type response has been supplemented in recent years with cell populations such as novel innate lymphoid cells, basophils, dendritic cells and regulatory T cells proposed to play an active role in responses to T. muris infection. Moreover, new immune-controlled mechanisms of expulsion, such as increased epithelial cell turnover and mucin secretion, have been described in recent years increasing the number of possible targets for anti-parasite therapies. In this review, we give a comprehensive overview of experimental work conducted on the T. muris infection model, focusing on important findings and the most recent reports on the role of the immune system in parasite expulsion.

Expansion of Paneth cell population in response to enteric Salmonella enterica serovar Typhimurium infection

Paneth cells residing at the base of the small intestinal crypts contribute to the mucosal intestinal first line defense by secreting granules filled with antimicrobial polypeptides including lysozyme. These cells derive from the columnar intestinal stem cell located at position 0 and the transit amplifying cell located at position +4 in the crypts. We have previously shown that Salmonella enterica serovar Typhimurium (ST), a leading cause of gastrointestinal infections in humans, effects an overall reduction of lysozyme in the small intestine. To extend this work, we examined small-intestinal tissue sections at various time points after ST infection to quantify and localize expression of lysozyme and assess Paneth cell abundance, apoptosis, and the expression of Paneth cell differentiation markers. In response to infection with ST, the intestinal Paneth cell-specific lysozyme content, the number of lysozyme-positive Paneth cells, and the number of granules per Paneth cell decreased. However, this was accompanied by increases in the total number of Paneth cells and the frequency of mitotic events in crypts, by increased staining for the proliferation marker PCNA, primarily at the crypt side walls where the transit amplifying cell resides and not at the crypt base, and by apoptotic events in villi. Furthermore, we found a time-dependent upregulation of first β-catenin, followed by EphB3, and lastly Sox9 in response to ST, which was not observed after infection with a Salmonella pathogenicity island 1 mutant deficient in type III secretion. Our data strongly suggest that, in response to ST infection, a Paneth cell differentiation program is initiated that leads to an expansion of the Paneth cell population and that the transit amplifying cell is likely the main progenitor responder. Infection-induced expansion of the Paneth cell population may represent an acute intestinal inflammatory response similar to neutrophilia in systemic infection.

Identification of quantitative trait loci affecting resistance to gastrointestinal parasites in a double backcross population of Red Maasai and Dorper sheep

A genome-wide scan for quantitative trait loci (QTL) affecting gastrointestinal nematode resistance in sheep was completed using a double backcross population derived from Red Maasai and Dorper ewes bred to F(1) rams. This design provided an opportunity to map potentially unique genetic variation associated with a parasite-tolerant breed like Red Maasai, a breed developed to survive East African grazing conditions. Parasite indicator phenotypes (blood packed cell volume - PCV and faecal egg count - FEC) were collected on a weekly basis from 1064 lambs during a single 3-month post-weaning grazing challenge on infected pastures. The averages of last measurements for FEC (AVFEC) and PCV (AVPCV), along with decline in PCV from challenge start to end (PCVD), were used to select lambs (N = 371) for genotyping that represented the tails (10% threshold) of the phenotypic distributions. Marker genotypes for 172 microsatellite loci covering 25 of 26 autosomes (1560.7 cm) were scored and corrected by Genoprob prior to qxpak analysis that included Box-Cox transformed AVFEC and arcsine transformed PCV statistics. Significant QTL for AVFEC and AVPCV were detected on four chromosomes, and this included a novel AVFEC QTL on chromosome 6 that would have remained undetected without Box-Cox transformation methods. The most significant P-values for AVFEC, AVPCV and PCVD overlapped the same marker interval on chromosome 22, suggesting the potential for a single causative mutation, which remains unknown. In all cases, the favourable QTL allele was always contributed from Red Maasai, providing support for the idea that future marker-assisted selection for genetic improvement of production in East Africa will rely on markers in linkage disequilibrium with these QTL.

A differential interplay between the expression of Th1/Th2/Treg related cytokine genes in Teladorsagia circumcincta infected DRB1*1101 carrier lambs

Substantial debate exists on whether the immune response between sheep resistant and susceptible to gastrointestinal nematodes can be differentiated into a Th1 and Th2 phenotype. The present study addresses the hypothesis that variation in resistance to Teladorsagia circumcincta between DRB1*1101 (associated with reduced faecal egg count and worm burden) carriers and non-carriers is due to a differential interplay in the expression of Th1/Th2 and regulatory T (Treg) related cytokine genes. Lambs from each genotype were either slaughtered at day 0 (un-infected control) or infected with 3 × 10⁴ Teladorsagia circumcincta L3 and slaughtered at 3, 7, 21, and 35 days later. Lambs carrying the DRB1*1101 allele had a significantly lower worm burden (P < 0.05) compared to the non-carriers. Abomasal mucosal cytokine gene expression was evaluated by quantitative real-time PCR and comparison made for time and genotype effects. The response generated varied through the course of infection and was affected by genotype. DRB1*1101 carriers had an up-regulated expression of the Th1-related cytokine genes (IL-1β, TNFα, and IFN-γ) at day 3, but this was replaced by an up-regulated expression of Th2-related cytokine genes (IL-10 and IL-13) and Treg-related cytokine genes (IL-2RA-CD25, TGFα, TGFβ, Arg2, MIF and FOXP3) by day 7. Conversely, in the non-carriers these changes in gene expression were delayed until days 7 and 21 post infection (pi), respectively. It is concluded that resistance to Teladorsagia circumcincta in animals carrying the DRB1*1101 allele is influenced by an earlier interplay between Th1, Th2 and T regulatory immune response genes.

Apoptosis induced by parasitic diseases

Fatalities caused by parasitic infections often occur as a result of tissue injury that results from a form of host-cell death known as apoptosis. However, instead of being pathogenic, parasite-induced apoptosis may facilitate host survival. Consequently, it is of utmost importance to decipher and understand the process and the role of apoptosis induced or controlled by parasites in humans. Despite this, few studies provide definitive knowledge of parasite-induced host-cell apoptosis. Here, the focus is on a consideration of host-cell apoptosis as either a pathogenic feature or as a factor enabling parasite survival and development.

Cell death by apoptotic-like mechanisms could be described as a ride to death with a return ticket, as initiation of the pathway may be reversed, with the potential that it could be manipulated for therapeutic purposes. The management of host-cell apoptosis could thus be an adjunctive factor for parasitic disease treatment. Evidence that the apoptotic process could be reversed by anti-apoptotic drugs has recently been obtained, leading to the possibility of host-cell rescue after injury. An important issue will be to predict the beneficial or deleterious effects of controlling human cell death by apoptotic-like mechanisms during parasitic diseases.

Systems biology of ovine intestinal parasite resistance: disease gene modules and biomarkers

This study reports on the molecular systems biology of gastrointestinal nematode (GIN) infection and potential biomarkers for GIN resistance in sheep. Microarray gene expression data were obtained for 3 different tissues at 4 time points from sheep artificially challenged with two types of nematodes, Haemonchus contortus (HC) and Trichostrongylus colubriformis (TC). We employed an integrated systems biology approach, integrating 3 main methods: standard differential gene expression analyses, weighted gene co-expression network analyses (WGCNA) and quantitative genetic analyses of gene expression traits of key biomarkers. Using standard differential gene expression analyses we identified differentially expressed genes (DE) which responded differently in sheep challenged with HC compared to those challenged with TC. These interaction genes (e.g. MRPL51, SMEK2, CAT, MAPK1IP1 and SLC25A20A) were enriched in Wnt receptor signalling pathway (p = 0.0132) and positive regulation of NFκβ transcription factor activity (p = 0.00208). We report FCER1A, a gene encoding a high-affinity receptor for the Fc region of immunoglobulin E, which is linked to innate immunity to GIN in sheep. Using weighted gene co-expression network analysis (WGCNA) methods, we identified gene modules that were correlated with the length of infection (disease modules). Hub genes (with high intramodular connectivity) were filtered further to identify biomarkers that are related to the length of infection (e.g. CAT, FBX033, COL15A1, IGFBP7, FBLN1 and IgCgamma). The biomarkers we found in HC networks were significantly associated with functions such as T-cell and B-cell regulations, TNF-alpha, interleukin and cytokine production. In TC networks, biomarkers were significantly associated with functions such as protein catabolic process, heat shock protein binding, protein targeting and localization, cytokine receptor binding, TNF receptor binding, apoptosis and IGF binding. These results provide specific gene targets for therapeutic interventions and provide insights into GIN infections in sheep which may be used to infer the same in related host species. This is also the first study to apply the concept of estimating breeding values of animals to expression traits and reveals 11 heritable candidate biomarkers (0.05 to 0.92) that could be used in selection of animals for GIN resistance.

Mucin gene deficiency in mice impairs host resistance to an enteric parasitic infection

BACKGROUND & AIMS

Hyperplasia of mucin-secreting intestinal goblet cells accompanies a number of enteric infections, including infections by nematode parasites. Nevertheless, the precise role of mucins in host defense in nematode infection is not known. We investigated the role of the mucin (Muc2) in worm expulsion and host immunity in a model of nematode infection.

METHODS

Resistant (BALB/c, C57BL/6), susceptible (AKR), and Muc2-deficient mouse strains were infected with the nematode, Trichuris muris, and worm expulsion, energy status of the whipworms, changes in mucus/mucins, and inflammatory and immune responses were investigated after infection.

RESULTS

The increase in Muc2 production, observed exclusively in resistant mice, correlated with worm expulsion. Moreover, expulsion of the worms from the intestine was significantly delayed in the Muc2-deficient mice. Although a marked impairment in the development of periodic acid Schiff (PAS)-stained intestinal goblet cells was observed in Muc2-deficient mice, as infection progressed a significant increase in the number of PAS-positive goblet cells was observed in these mice. Surprisingly, an increase in Muc5ac, a mucin normally expressed in the airways and stomach, was observed after infection of only the resistant animals. Overall, the mucus barrier in the resistant mice was less permeable than that of susceptible mice. Furthermore, the worms isolated from the resistant mice had a lower energy status.

CONCLUSIONS

Mucins are an important component of innate defense in enteric infection; this is the first demonstration of the important functional contribution of mucins to host protection from nematode infection.

Epithelial cell apoptosis facilitates Entamoeba histolytica infection in the gut

Entamoeba histolytica is the protozoan parasite that causes amebic colitis. The parasite triggers apoptosis on contact with host cells; however, the biological significance of this event during intestinal infection is unclear. We examined the role of apoptosis in a mouse model of intestinal amebiasis. Histopathology revealed that abundant epithelial cell apoptosis occurred in the vicinity of amoeba in histological specimens. Epithelial cell apoptosis occurred rapidly on co-culture with amoeba in vitro as measured by annexin positivity, DNA degradation, and mitochondrial dysfunction. Administration of the pan caspase inhibitor ZVAD decreased the rate and severity of amebic infection in CBA mice by all measures (cecal culture positivity, parasite enzyme-linked immunosorbent assay, and histological scores). Similarly, caspase 3 knockout mice on the resistant C57BL/6 background exhibited even lower cecal parasite antigen burden and culture positive rates than wild type mice. The permissive effect of apoptosis on infection could be tracked to the epithelium, in that transgenic mice that overexpressed Bcl-2 in epithelial cells were more resistant to infection as measured by cecal parasite enzyme-linked immunosorbent assay and histological scores. We concluded that epithelial cell apoptosis in the intestine facilitates amebic infection in this mouse model. The parasite's strategy for inducing apoptosis may point to key virulence factors, and therapeutic maneuvers to diminish epithelial apoptosis may be useful in amebic colitis.

An apoptosis-inducing serine protease secreted by the entomopathogenic nematode Steinernema carpocapsae

Steinernema carpocapsae is an insect parasitic nematode able to parasitise and kill the host within 48 h. Secreted products (ESP) of the parasitic stage of a virulent strain contain higher amounts of proteolytic activity than a low virulence strain, suggesting proteases are involved in virulence. From the ESP we purified a protein (Sc-SP-3) with a M(r) of 30 kDa and a pI of 7 that cleaved the synthetic substrate N-succinyl-Ala-Ala-Pro-Phe-pNA and was inhibited by phenylmethanesulfonyl fluoride, benzamidine and chymostatin, thus indicating that it belongs to the chymotrypsin-like serine protease family. Sc-SP-3 has a V(max) of 0.3 mM min(-1)ml(-1) and K(m) of 6.6 x 10(-4)M, with maximum activity at pH 8 and 40 degrees C. The full-length cDNA was obtained using degenerate oligonucleotides for serine proteases. This open reading frame encodes a preproprotein containing a putative signal peptide composed of 16 amino acid residues, a prodomain of 40 residues and a mature protease domain of 261 residues, including the catalytic triad His/Asp/Ser characteristic of trypsin-like serine proteases. The N-terminal sequence and the peptide masses fingerprint obtained by MALDI-TOF-MS for the purified protein matched the cDNA. Gene expression analysis by quantitative real-time-PCR showed that this gene is expressed only during the parasitic stage and that pre-invasive nematodes inside the mid-gut expressed higher amounts of Sc-SP-3 than those that already enter the haemocoel. Sc-SP-3 caused histolysis in the insect mid-gut. In vitro assays demonstrated that Sc-SP-3 digested extracellular proteins and induced apoptosis in Sf9 insect cells, thus suggesting Sc-SP-3 is a multifunctional chymotrypsin-like protease involved in pathogenesis.

The intestinal epithelium: sensors to effectors in nematode infection

The role of the intestinal epithelium as part of the physical barrier to infection is well established alongside its central roles in food absorption, sensing nutrients, and water balance. Nematodes are one of the most common types of pathogen to dwell in the intestine. This article reviews recent data that have identified crucial roles for intestinal epithelial cells in sensing these kinds of pathogens and initiating innate responses, which qualitatively influence adaptive immune responses against them. Moreover, it is now clear that the epithelium itself--in addition to the cells that lie within it--are key to many of the protective mechanisms that result in expulsion of these large multicellular parasites from the intestine. An understanding of the IEC and intraepithelial leukocyte response is crucial to both development of mucosal vaccines, and the mechanisms that underlie the emerging use of intestinal dwelling helminths for therapeutic treatments of inflammatory and autoimmune disease.

Gender and genetic control of resistance to intestinal amebiasis in inbred mice

Resistance to the establishment of intestinal Entamoeba histolytica infection is dependent on the inbred mouse strain. In this work we used the inbred strains B6 (resistant), CBA (susceptible), B6CBAF(1) and a backcross of B6CBAF(1) to CBA to further examine the genetic basis of resistance. Mouse genotype was assessed with single nucleotide polymorphism and microsatellite markers and infection assessed by culture 9 days after intracecal E. histolytica challenge. The backcross population showed a male predisposition to culture positivity (P<0.002). F1 genotype at two loci on chromosomes 1 and 2 exhibited suggestive linkage with resistance to infection (P=0.0007 and 0.0200). Additional suggestive quantitative trait locus were observed on chromosomes 1, 9 and 13 for cecal parasite antigen load and histologic evidence of inflammation. Infection in C3H x B6 recombinant inbred mice supported the mapping data. Candidate B6 genes on chromosomes 1 and 2 were examined by microarray analysis of epithelial tissues from B6 vs CBA mice. This work shows a male predisposition to intestinal amebiasis and suggests that relatively few B6 loci can confer resistance in inbred mice. Future identification of regional candidate genes has implications for understanding the human variability to amebic infection.

Deciphering the 'black box' of the intestinal stem cell niche: taking direction from other systems

PURPOSE OF REVIEW

Study of developmental signaling pathways suggests that the intestinal stem cell niche regulates the activity of the crypt-based epithelial progenitors during homeostasis and injury states. The cellular origin of these signals, however, remains poorly defined. Here, we examine the current state of knowledge regarding intestinal epithelial progenitor niches and highlight applicable lessons learned from other systems.

RECENT FINDINGS

Cell-cell contact, regulatory factor delivery, stem cell polarity, and mesenchymal stem cells are considered.

SUMMARY

Based on the findings in other niche systems as well as the overall complexity and unique organization of the intestinal progenitor niche, future studies will focus on defining peri-cryptal architecture, cellular sources of regulatory factors, and the dynamic nature of the niche during homeostasis and injury repair. These insights may lead to novel cell-based therapies for a variety of conditions that damage the mucosal lining of the gut.

Persistence of Entamoeba histolytica infection in CBA mice owes to intestinal IL-4 production and inhibition of protective IFN-gamma

The mechanisms whereby certain mouse strains develop persistent intestinal infection with Entamoeba histolytica remain unclear. In this work, we characterized the kinetic pattern of cytokine responses during the course of natural infection in CBA mice and showed that intracecal amebic infection led to a rapid and sustained upregulation of Th2 (IL-4, IL-5, IL-13) and Th17 cytokine responses while Th1 cytokines, IL-12p35 and interferon (IFN)-gamma, were suppressed. Depletion of IL-4 cleared infection by 14 days post-challenge, and this clearance correlated with and was mediated by IFN-gamma. The protective role for IFN-gamma was not strain-specific, as 129 background IFN-gammaR knockout mice exhibited a higher infection rate than their wild-type littermates. These studies indicate that IL-4 plays a critical pathogenic role in the persistence of E. histolytica infection through suppression of protective IFN-gamma and provide a possible explanation for why certain humans spontaneously clear amebiasis while others progress to invasive disease.