Heligmosomoides polygyrus bakeri induces tolerogenic dendritic cells that block colitis and prevent antigen-specific gut T cell responses

Helminths in alternative therapeutics of inflammatory bowel disease

Inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis, is a nonspecific chronic inflammation of the gastrointestinal tract. Despite recent advances in therapeutics and newer management strategies, IBD largely remains untreatable. Helminth therapy is a promising alternative therapeutic for IBD that has gained some attention in the last two decades. Helminths have immunomodulatory effects and can alter the gut microbiota. The immunomodulatory effects include a strong Th2 immune response, T-regulatory cell response, and the production of regulatory cytokines. Although concrete evidence regarding the efficacy of helminth therapy in IBD is lacking, clinical studies and studies done in animal models have shown some promise. Most clinical studies have shown that helminth therapy is safe and easily tolerable. Extensive work has been done on the whipworm Trichuris, but other helminths, including Schistosoma, Trichinella, Heligmosomoides, and Ancylostoma, have also been explored for pre-clinical and animal studies. This review article summarizes the potential of helminth therapy as an alternative therapeutic or an adjuvant to the existing therapeutic procedures for IBD treatment.

Immunomodulatory effect of Dicrocoelium dendriticum ova on DSS-induced experimental colitis in C57BL/6 mouse

Inflammatory bowel disease (IBD) significantly diminishes an individual's quality of life and increases the risk of colorectal cancer. Recent clinical and experimental findings suggest that infection with parasitic helminths may suppress the development of certain inflammatory conditions. The objective of this study was to evaluate the immunoregulatory effects of Dicrocoelium eggs on experimentally induced colitis in C57BL/6 mice using dextran sulfate sodium (DSS). C57BL/6 mice received 3.5% DSS orally for 7 days to induce colitis, during which they were treated intraperitoneally with Dicrocoelium eggs. The severity of colitis was assessed through parameters such as body weight, stool consistency or bleeding, disease activity index (DAI), colon lengths, macroscopic scores, histopathological findings, colon gene expression levels, and serum cytokine levels. Our results indicated that Dicrocoelium eggs administration significantly reduced the severity of colitis and disease activity. Histopathological scores improved, correlating with downregulation of IFN-γ and upregulation of IL-4 expression. This findings suggest the therapeutic potential of Dicrocoelium eggs in treating colitis. Immunotherapy involving Dicrocoelium eggs primarily induces a Th2 response and modulates IFN-γ, contributing to reduced inflammation in colitis. Thus, this approach could be a promising therapeutic strategy for alleviating inflammation in IBD.

Pharmaceutical Potential of Remedial Plants and Helminths for Treating Inflammatory Bowel Disease

Research is increasingly revealing that inflammation significantly contributes to various diseases, particularly inflammatory bowel disease (IBD). IBD is a major medical challenge due to its chronic nature, affecting at least one in a thousand individuals in many Western countries, with rising incidence in developing nations. Historically, indigenous people have used natural products to treat ailments, including IBD. Ethnobotanically guided studies have shown that plant-derived extracts and compounds effectively modulate immune responses and reduce inflammation. Similarly, helminths and their products offer unique mechanisms to modulate host immunity and alleviate inflammatory responses. This review explored the pharmaceutical potential of Aboriginal remedial plants and helminths for treating IBD, emphasizing recent advances in discovering anti-inflammatory small-molecule drug leads. The literature from Scopus, MEDLINE Ovid, PubMed, Google Scholar, and Web of Science was retrieved using keywords such as natural product, small molecule, cytokines, remedial plants, and helminths. This review identified 55 important Aboriginal medicinal plants and 9 helminth species that have been studied for their anti-inflammatory properties using animal models and in vitro cell assays. For example, curcumin, berberine, and triptolide, which have been isolated from plants; and the excretory-secretory products and their protein, which have been collected from helminths, have demonstrated anti-inflammatory activity with lower toxicity and fewer side effects. High-throughput screening, molecular docking, artificial intelligence, and machine learning have been engaged in compound identification, while clustered regularly interspaced short palindromic repeats (CRISPR) gene editing and RNA sequencing have been employed to understand molecular interactions and regulations. While there is potential for pharmaceutical application of Aboriginal medicinal plants and gastrointestinal parasites in treating IBD, there is an urgent need to qualify these plant and helminth therapies through reproducible clinical and mechanistic studies.

Helminth Lessons in Inflammatory Bowel Diseases (IBD)

Helminths are multicellular invertebrates that colonize the gut of many vertebrate animals including humans. This colonization can result in pathology, which requires treatment. It can also lead to a commensal and possibly even a symbiotic relationship where the helminth and the host benefit from each other's presence. Epidemiological data have linked helminth exposure to protection from immune disorders that include a wide range of diseases, such as allergies, autoimmune illnesses, and idiopathic inflammatory disorders of the gut, which are grouped as inflammatory bowel diseases (IBD). Treatment of moderate to severe IBD involves the use of immune modulators and biologics, which can cause life-threatening complications. In this setting, their safety profile makes helminths or helminth products attractive as novel therapeutic approaches to treat IBD or other immune disorders. Helminths stimulate T helper-2 (Th2) and immune regulatory pathways, which are targeted in IBD treatment. Epidemiological explorations, basic science studies, and clinical research on helminths can lead to the development of safe, potent, and novel therapeutic approaches to prevent or treat IBD in addition to other immune disorders.

Protection from T cell-dependent colitis by the helminth-derived immunomodulatory mimic of transforming growth factor-β, Hp-TGM

In animal models of inflammatory colitis, pathology can be ameliorated by several intestinal helminth parasites, including the mouse nematode Heligmosomoides polygyrus. To identify parasite products that may exert anti-inflammatory effects in vivo, we tested H. polygyrus excretory-secretory (HES) products, as well as a recombinantly expressed parasite protein, transforming growth factor mimic (TGM), that functionally mimics the mammalian immunomodulatory cytokine TGF-β. HES and TGM showed a degree of protection in dextran sodium sulphate-induced colitis, with a reduction in inflammatory cytokines, but did not fully block the development of pathology. HES also showed little benefit in a similar acute trinitrobenzene sulphonic acid-induced model. However, in a T cell transfer-mediated model with recombination activation gene (RAG)-deficient mice, HES-reduced disease scores if administered throughout the first 2 or 4 weeks following transfer but was less effective if treatment was delayed until 14 days after T cell transfer. Recombinant TGM similarly dampened colitis in RAG-deficient recipients of effector T cells, and was effective even if introduced only once symptoms had begun to be manifest. These results are a promising indication that TGM may replicate, and even surpass, the modulatory properties of native parasite HES.

Potential of human helminth therapy for resolution of inflammatory bowel disease: The future ahead

Inflammatory bowel disease (IBD) is associated with a dysregulated mucosal immune response in the gastrointestinal tract. The number of patients with IBD has increased worldwide, especially in highly industrialized western societies. The population of patients with IBD in North America is forecasted to reach about four million by 2030; meanwhile, there is no definitive therapy for IBD. Current anti-inflammatory, immunosuppressive, or biological treatment may induce and maintain remission, but not all patients respond to these treatments. Recent studies explored parasitic helminths as a novel modality of therapy due to their potent immunoregulatory properties in humans. Research using IBD animal models infected with a helminth or administered helminth-derived products such as excretory-secretory products has been promising, and helminth-microbiota interactions exert their anti-inflammatory effects by modulating the host immunity. Recent studies also indicate that evidence that helminth-derived metabolites may play a role in anticolitic effects. Thus, the helminth shows a potential benefit for treatment against IBD. Here we review the current feasibility of "helminth therapy" from the laboratory for application in IBD management.

The ubiquitous role of spleen tyrosine kinase (Syk) in gut diseases: From mucosal immunity to targeted therapy

Spleen tyrosine kinase (Syk) is a cytoplasmic non-receptor protein tyrosine kinase expressed in a variety of cells and play crucial roles in signal transduction. Syk mediates downstream signaling by recruiting to the dually phosphorylated immunoreceptor tyrosine-based activation motifs (ITAMs) of the transmembrane adaptor molecule or the receptor chain itself. In gut diseases, Syk is observed to be expressed in intestinal epithelial cells, monocytes/macrophages, dendritic cells and mast cells. Activation of Syk in these cells can modulate intestinal mucosal immune response by promoting inflammatory cytokines and chemokines production, thus regulating gut homeostasis. Due to the restriction of specificity and selectivity for the development of Syk inhibitors, only a few such inhibitors are available in gut diseases, including intestinal ischemia/reperfusion damage, infectious disease, inflammatory bowel disease, etc. The promising outcomes of Syk inhibitors from both preclinical and clinical studies have shown to attenuate the progression of gut diseases thereby indicating a great potential in the development of Syk targeted therapy for treatment of gut diseases. This review depicts the characterization of Syk, summarizes the signal pathways of Syk, and discusses its potential targeted therapy for gut diseases.

Immunomodulatory potential of nematodes against dendritic cells is dependent on intestinal inflamation

The mouse intestinal parasite Heligmosomoides polygyrus demonstrates adaptation to the inflammatory milieu as a result of colitis induced by dextran sulphate sodium (DSS). Nematodes from mice with colitis had different effects on dendritic cells than nematodes from mice without colitis. Immature JAWSII cells pre-exposed to L4 stage H. polygyrus from DSS-treated mice were adoptively transferred to mice with induced colitis. After two days, a higher disease activity index, macroscopic damage score and colon histology score were observed. MLN T cells isolated nine days after transfer demonstrated proinflammatory IFN-γ and IL-17 production. Transfer of JAWSII stimulated with male or female L4 larvae from a control invasion resulted in a slight improvement of colitis; in addition, dendritic cells exposed to H. polygyrus female L4 larvae, provoked migration of CD8⁺CD25⁺ T cells from MLN to the colon. Nematodes from an inflammatory environment changed cytokine production by dendritic cells. Inflammatory milieu changing nematode immunomodulatory activity affects dendritic cell functions, which offers new insight into the helminth-host relationship.

Inflammatory bowel diseases, the hygiene hypothesis and the other side of the microbiota: Parasites and fungi

This review tackles the concept of the evolutionary mismatch, in relation with the reduction of the prevalence of the so-called "dirty old friends". These formed the variegated community of parasites and microorganisms, either prokaryotic or eukaryotic, that, over long evolutionary times, co-evolved with humans and their ancestors, inhabiting their digestive tracts, and other body districts. This community of microbial symbionts and metazoan parasites is thought to have evolved a complex network of inter-independence with the host, in particular in relation with their immune stimulating capacity, and with the consequent adaptation of the host immune response to this chronic stimulation. Strictly related to this evolutionary mismatch, the hygiene hypothesis, proposed by David Strachan in 1989, foresees that the increase in the incidence of inflammatory and autoimmune disorders during the twentieth century has been caused by the reduced exposure to parasites and microorganisms, especially in industrialized countries. Among these pathologies, inflammatory bowel diseases (IBDs) occupy a prominent role. From these premises, this review summarizes current knowledge on how variations in the composition of the gut bacterial microbiota, as well as its interactions with fungal communities, influence the overall immune balance, favouring or counteracting gut inflammation in IBDs. Additionally, the effect of worm parasites, either directly on the immune balance, or indirectly, through the modulation of bacterial and fungal microbiota, will be addressed. Finally, we will review a series of studies related to the use of molecules derived from parasitic worms and fungi, which hold the potential to be developed as postbiotics for the treatment of IBDs.

Immunomodulatory effect of Syphacia obvelata in treatment of experimental DSS-induced colitis in mouse model

The ability of helminth parasite infections to manipulate the immune system of their host towards T regulatory responses has been proposed to suppress the inflammatory response. The aim of this study was to investigate the protective and therapeutic effect of Syphacia obvelata in the treatment of experimental DSS -induced colitis. 50 male C57BL/6 mice were divided into 5 groups: healthy uninfected controls, DSS colitis, receiving only S. obv, preventive (S. obv + DSS) and therapeutic group (DSS + S.obv). Colitis intensity was investigated by measuring body weight changes, stool consistency/bleeding and colon length. To evaluate the immune responses induced by this nematode, TNF-α, IL-10, IL-17, IFN-γ and expressing of FoxP3⁺ T cells were measured in mesenteric lymph nodes and Peyer’s patches cells. Mice in preventive and therapeutic groups treated with S. obv egg significantly ameliorated the severity of the DSS colitis, indicated by the reduced disease manifestations, improved histopathological scores correlated with the up regulation of Treg responses and down regulation of proinflammatory cytokines. S. obv can prevention and reverse on-going murine DSS colitis. The data suggest that induction of Tregs and change in cytokine profiles during helminthic therapies were responsible for reversed inflammatory events in IBD.

Glutathione-S-transferase of Trichinella spiralis regulates maturation and function of dendritic cells

Immunomodulation by molecules from Trichinella spiralis (T. spiralis) has been widely reported. Glutathione-S-transferase (GST) is a major immune-modulator of the family of detoxification enzymes. Dendritic cells (DCs) are an important target for the regulation of the immune response by T. spiralis. In this study, the recombinant GST of T. spiralis (rTs-GST) was expressed and purified. rTs-GST induced low CD40 expression and moderate CD80, CD86 and MHC-II expressions and inhibited the increase of CD40, CD80 and CD86 on DCs induced by LPS. We showed that rTs-GST decreased the LPS-induced elevated level of pro-inflammatory cytokines of DCs and enhanced the level of regulatory cytokines IL-10 and TGF-β. Furthermore, co-culture of DCs and CD4+ T cells demonstrated that rTs-GST-treated DCs suppressed the proliferation of OVA-specific CD4+ T cells and increased the population of regulatory T cells (Tregs). rTs-GST-treated DCs induced a higher level of IL-4, IL-10 and TGF-β, but inhibited the level of IFN-γ. This indicates that rTs-GST-pulsed DCs induce both Th2-type responses and Tregs. These findings contribute to the current understanding of the immunomodulation of Ts-GST on cellular response and immunomodulation of T. spiralis.

Effects of intestinal nematode treatment on CD11b activation state in an EAE mouse model of multiple sclerosis

The experimental autoimmune encephalomyelitis (EAE) animal model of Multiple Sclerosis (MS) is characterized by episodic neurologic dysfunction arising as a consequence of perivascular mononuclear cell infiltration and demyelination in the CNS. Leukocyte integrins, which are responsible for migration through the endothelial, play key roles in the pathogenesis of autoimmune diseases and chronic inflammation. Intestinal infection of mice with Heligmosomoides polygyrus appears to target CD11b (integrin αM), which is highly expressed on myeloid cells and is critical for their migration and function. H. polygyrus infection induces suppression of ongoing experimental EAE and extensive infiltration of CD11b⁺ cells to the CNS. Therefore, the aim of the present study was to characterize the phenotype and activity of CD11b⁺ cells accompanying the tissue phase infection of L4 H. polygyrus in EAE mice. It was found that the cells displayed a CD11b⁺ state with a distinct phenotype characterised by the expression of co-stimulatory CD80/CD86, CD40, MHCII, F4/80 and the mannose receptor CD206. This activation state illustrates the heterogeneity of CD11b⁺ cells in EAE mice following nematode invasion; these may have important consequences for understanding the effects of CD11b integrin, which is involved in the downregulation of neuroinflammatory disorders.

Dendritic cells treated by Trichinella spiralis muscle larval excretory/secretory products alleviate TNBS-induced colitis in mice

BACKGROUND

Therapeutic potential of helminth have been shown to have a protective effect on immune-mediated diseases such as Crohn's disease (CD), which is associated with increased production of T helper cell type 1. However, helminth therapy is unacceptable to patients due to side-effects and the fear of parasites. As helminths regulate the cellular immune responses through innate cells such as dendritic cells (DCs), cellular immunotherapy has been considered a therapeutic option to treat CD.

METHODS

Bone marrow-dendritic cells were generated, enriched and treated with Trichinella spiralis muscle larval excretory/secretory products (Ts-MLES). DCs maturation was measured by flow cytometry and cytokine production of DCs were measured by ELISA. Colitis was generated by intrarectal administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS) solution. For adoptive transfer, Ts-MLES treated-DCs injected intravenously 24 h prior to TNBS challenge. Disease activity index (DAI) including weight loss, diarrhea, and bloody stool were measured. Colon segments were stained with hematoxylin and eosin (H.E.) and periodic acid schiff (PAS) staining for histological damage scoring. The relative mRNA expression of cytokines in colon was analyzed by RT-PCR. Cytokine production in colon was measured by ELISA. Splenocytes were separated and cytokine profiles including Th1 (IFN-γ), Th2 (IL-4, IL-13), and Treg subsets (IL-10, TGF-β) were analyzed by flow cytometry.

RESULTS

Ts-MLES regulated the maturation and cytokine production of DCs. Ts-MLES -DC ameliorated the severity of the TNBS-induced colitis. In the colon and the spleen, Ts-MLES-DC decreased IFN-γ (Th1) significantly and increased Th2 (IL-4, IL-13)- and Treg (IL-10, TGF-β)- related cytokines.

CONCLUSIONS

Ts-MLES-DC ameliorated the severity of the TNBS-induced colitis through decreasing IFN-γ. Ts-MLES-DC skewed the Th1-mediated response toward the Th2 type and regulatory T cell response.

Heligmosomoides polygyrus bakeri Infection Decreases Smad7 Expression in Intestinal CD4+ T Cells, Which Allows TGF-β to Induce IL-10-Producing Regulatory T Cells That Block Colitis

Helminthic infections modulate host immunity and may protect their hosts from developing immunological diseases like inflammatory bowel disease. Induction of regulatory T cells (Tregs) may be an important part of this protective process. Heligmosomoides polygyrus bakeri infection also promotes the production of the regulatory cytokines TGF-β and IL-10 in the gut. In the intestines, TGF-β helps induce regulatory T cells. This study used Foxp3/IL-10 double reporter mice to investigate the effect of TGF-β on the differentiation of colon and mesenteric lymph node-derived murine Foxp3^- IL-10^- CD4⁺ T cells into their regulatory phenotypes. Foxp3^- IL-10^- CD4⁺ T cells from H. polygyrus bakeri-infected mice, as opposed to T cells from uninfected animals, cultured in vitro with TGF-β and anti-CD3/CD28 mAb differentiated into Foxp3⁺ and/or IL-10⁺ T cells. The IL-10-producing T cells nearly all displayed CD25. Smad7 is a natural inhibitor of TGF-β signaling. In contrast to gut T cells from uninfected mice, Foxp3^- IL10^- CD4⁺ T cells from H. polygyrus bakeri-infected mice displayed reduced Smad7 expression and responded to TGF-β with Smad2/3 phosphorylation. The TGF-β-induced Tregs that express IL-10 blocked colitis when transferred into the Rag/CD25^- CD4⁺ T cell transfer model of inflammatory bowel disease. TGF-β had a greatly diminished capacity to induce Tregs in H. polygyrus bakeri-infected transgenic mice with constitutively high T cell-specific Smad7 expression. Thus, infection with H. polygyrus bakeri causes down-modulation in Smad7 expression in intestinal CD4⁺ T cells, which allows the TGF-β produced in response to the infection to induce the Tregs that prevent colitis.

The hygiene hypothesis at a glance: Early exposures, immune mechanism and novel therapies

The hygiene hypothesis was proposed almost three decades ago. Nevertheless, its mechanism still remains with relevant controversies. Some studies defend that early exposures during childhood to microbes and parasites are key determinants to prevent allergies and autoimmune diseases; however, other studies demonstrated that these early exposures can even potentiate the clinical scenario of the diseases. Based on several studies covering the influences of microbiome, parasites, related theories and others, this review focuses on recent advances in the hygiene hypothesis field. In addition, the main immunological mechanisms underlying the hygiene hypothesis are also discussed. We also strongly encourage that researchers do not consider the hygiene hypothesis as a theory based strictly on hygiene habits, but a theory combining diverse influences, as illustrated in this review as the hygiene hypothesis net.

Analysis of the Trichuris suis excretory/secretory proteins as a function of life cycle stage and their immunomodulatory properties

Parasitic worms have a remarkable ability to modulate host immune responses through several mechanisms including excreted/secreted proteins (ESP), yet the exact nature of these proteins and their targets often remains elusive. Here, we performed mass spectrometry analyses of ESP (TsESP) from larval and adult stages of the pig whipworm Trichuris suis (Ts) and identified ~350 proteins. Transcriptomic analyses revealed large subsets of differentially expressed genes in the various life cycle stages of the parasite. Exposure of bone marrow-derived macrophages and dendritic cells to TsESP markedly diminished secretion of the pro-inflammatory cytokines TNFα and IL-12p70. Conversely, TsESP exposure strongly induced release of the anti-inflammatory cytokine IL-10, and also induced high levels of nitric oxide (NO) and upregulated arginase activity in macrophages. Interestingly, TsESP failed to directly induce CD4+ CD25+ FoxP3+ regulatory T cells (Treg cells), while OVA-pulsed TsESP-treated dendritic cells suppressed antigen-specific OT-II CD4+ T cell proliferation. Fractionation of TsESP identified a subset of proteins that promoted anti-inflammatory functions, an activity that was recapitulated using recombinant T. suis triosephosphate isomerase (TPI) and nucleoside diphosphate kinase (NDK). Our study helps illuminate the intricate balance that is characteristic of parasite-host interactions at the immunological interface, and further establishes the principle that specific parasite-derived proteins can modulate immune cell functions.

Helminth Infections Induce Tissue Tolerance Mitigating Immunopathology but Enhancing Microbial Pathogen Susceptibility

Helminths are ubiquitous and have chronically infected vertebrates throughout their evolution. As such helminths have likely exerted considerable selection pressure on our immune systems. The large size of multicellular helminths and their limited replicative capacity in the host necessarily elicits different host protective mechanisms than the immune response evoked by microbial pathogens such as bacteria, viruses and intracellular parasites. The cellular damage resulting from helminth migration through tissues is a major trigger of the type 2 and regulatory immune responses, which activates wound repair mechanisms that increases tissue tolerance to injury and resistance mechanisms that enhance resistance to further colonization with larval stages. While these wound healing and anti-inflammatory responses may be beneficial to the helminth infected host, they may also compromise the host's ability to mount protective immune responses to microbial pathogens. In this review we will first describe helminth-induced tolerance mechanisms that develop in specific organs including the lung and the intestine, and how adaptive immunity may contribute to these responses through differential activation of T cells in the secondary lymphoid organs. We will then integrate studies that have examined how the immune response is modulated in these specific tissues during coinfection of helminths with viruses, protozoa, and bacteria.

Worms: Pernicious parasites or allies against allergies?

Type 2 immune responses are most commonly associated with allergy and helminth parasite infections. Since the discovery of Th1 and Th2 immune responses more than 30 years ago, models of both allergic disease and helminth infections have been useful in characterizing the development, effector mechanisms and pathological consequences of type 2 immune responses. The observation that some helminth infections negatively correlate with allergic and inflammatory disease led to a large field of research into parasite immunomodulation. However, it is worth noting that helminth parasites are not always benign infections, and that helminth immunomodulation can have stimulatory as well as suppressive effects on allergic responses. In this review, we will discuss how parasitic infections change host responses, the consequences for bystander immunity and how this interaction influences clinical symptoms of allergy.

T-Bet Is Dependent on Stat-4 Inhibiting Acute Colitis but Not Stat-1 Using L4 Somatic Antigen of Heligmosomoides polygyrus

Helminths may alter the immunoinflammatory reactions of colitis. Proteins derived from H. polygyrus have prospective therapy for colitis. The goal of this study was to interpret the protective mechanisms of L4 somatic antigen (LSA) from Heligmosomoides polygyrus against an inflammatory response to the pathogenesis of DNBS-induced colitis. Colitis was actuated in mice by rectal instillation of DNBS. The mice were randomly divided into five groups containing control, DNBS alone, and three groups, with different doses of LSA (50, 100, and 200 μg/mL), respectively. Mice initiated colitis by rectal administration of DNBS and after that were immunized with LSA for 14 days. Mice treated with LSA inhibited wasting disease compared with DNBS only group. The percentages of cells producing IFN-γ were reduced by LSA treatment. The level of T lymphocytes CD4⁺IFN-γ⁺ cells in the LPL was significantly diminished by LSA at both 100 and 200 μg/mL groups (p<0.05). The mRNA expression of T-bet was significantly declined in LSA immunized mice, but not RORγ-T mRNA, whereas GATA-3 expression tended to increase. The activation of STAT-4 significantly reduced LSA-treated mice but not STAT-1. It can be concluded that T-bet is required for optimal production of IFN-γ in colitis.

Helminth Therapy: Advances in the use of Parasitic Worms Against Inflammatory Bowel Diseases and its Challenges

Development of modern medicine and better living conditions in the 20th century helped in reducing a number of cases of infectious diseases. During the same time, expansion of autoimmunological disorders was noticed. Among other are Inflammatory Bowel Diseases (IBD) including ulcerative colitis and Crohn's disease which are chronic and relapsing inflammation of the gastrointestinal tract. Absence of effective treatment in standard therapies effects the search for alternative opportunities. As per hygienic hypothesis increasing number of cases of autoimmune diseases is as a result of reduced exposure to pathogens, especially parasites. Thus, one of the promising remedial acts against IBD and other allergic and autoimmune disorders is "helminth therapy". Cure with helminths seems to be the most effective therapy of IBD currently proposed. Helminth therapy focuses on advantageous results that have been obtained from the clinical trials, but its mechanisms are still unclear. Explanation of this phenomenon would help to develop new drugs against IBD based on helminth immunomodulatory molecules.

Role in Allergic Diseases of Immunological Cross-Reactivity between Allergens and Homologues of Parasite Proteins

Implied under the rubric of the hygiene hypothesis is that helminth infection can protect against allergic disease. It is well known that helminths induce processes associated with type 2 immune responses, but they also induce important regulatory responses that can modulate these type 2-associated responses-modulation that influences responses to bystander antigens including allergens. Indeed, most epidemiological studies demonstrate a beneficial effect of helminth infection on atopy, but there are also convincing data to demonstrate that helminth infection can precipitate or worsen allergic inflammation/disease. Reasons for these disparate findings are much debated, but there is a school of thought that suggests that helminth-triggered type 2-associated responses, including IgE to cross-reactive aeroallergens, can offset the regulatory effects imposed by the same organisms. The cross-reactivity among helminths and allergenic tropomyosins dominated the antigen/allergen cross-reactivity field, but recent data suggest that cross-reactivity is much more common than previously appreciated. It has been demonstrated that a high degree of molecular similarity exists between allergens and helminth proteins. Thus, an understanding of the mechanisms underlying the response induced by helminth infection and their impact on the induction of allergic disease in the host are critical for designing therapies using iatrogenic infections or parasite products to treat inflammatory diseases and for developing vaccines against helminth parasites.

Preventive Trichuris suis ova (TSO) treatment protects immunocompetent rabbits from DSS colitis but may be detrimental under conditions of immunosuppression

Trichuris suis ova (TSO) have been tested for therapeutic application in inflammatory bowel diseases (IBD) yet understanding of the underlying mechanisms and safety in an immunocompromised host is limited due to lack of a suitable animal model. We used a recently established rabbit model of dextran sodium sulphate (DSS) induced colitis to study the efficacy, mechanisms and safety of TSO therapy in immunocompetent and immunosuppressed animals. TSO treatment prevented the DSS induced weight loss, delayed the onset of DSS induced symptoms by 2 days and significantly reduced the disease activity (DAI). TSO treatment protected caecal histology and prevented the colitis-associated loss in faecal microbiota diversity. Mainly the transcriptome of lamina propria mononuclear cells (LPMC) was affected by TSO treatment, showing dampened innate and adaptive inflammatory responses. The protective effect of TSO was lost in immunosuppressed rabbits, where TSO exacerbated colitis. Our data show that preventive TSO treatment ameliorates colitis severity in immunocompetent rabbits, modulates LPMC immune responses and reduces faecal dysbiosis. In contrast, the same TSO treatment exacerbates colitis in immunosuppressed animals. Our data provide further evidence for a therapeutic effect of TSO in IBD, yet caution is required with regard to TSO treatment in immunosuppressed patients.

Life history adjustments to intestinal inflammation in a gut nematode

Many parasitic nematodes establish chronic infections. This implies a finely tuned interaction with the host immune response in order to avoid infection clearance. Although a number of immune interference mechanisms have been described in nematodes, how parasites adapt to the immune environment provided by their hosts remains largely unexplored. Here, we used the gastrointestinal nematode Heligmosomoides polygyrus to investigate the plasticity of life history traits and immunomodulatory mechanisms in response to intestinal inflammation. We adopted an experimental model of induced colitis and exposed worms to intestinal inflammation at two different developmental stages (larvae and adults). We found that H. polygyrus responded to intestinal inflammation by up-regulating the expression of a candidate gene involved in the interference with the host immune response. Worms infecting mice with colitis also had better infectivity (earlier adult emergence in the intestinal lumen and higher survival) compared with worms infecting control hosts, suggesting that H. polygyrus adjusted its life history schedule in response to intestinal inflammation.

Triggering immunological memory against the tapeworm Hymenolepis diminuta to protect against colitis

Infection with parasitic helminths can ameliorate the severity of concomitant inflammatory disease. To use the tapeworm, Hymenolepis diminuta, and to extend this concept by assessing whether triggering a memory response against the worm inhibits dinitrobenzene sulphonic acid (DNBS)-induced colitis in Balb/c mice. Initial studies revealed that oral infection with 1, 3 or 5 H. diminuta cysticercoids 8 days before intrarectal administration of DNBS (3 mg) resulted in less severe inflammation and that infected mice displayed an increased propensity for T helper-2 immunity. A 1 mg dose of a PBS-soluble extract of the worm (HdAg) delivered intraperitoneally concomitant with DNBS was anticolitic as determined by macroscopic and histological disease scores 72 hour post-DNBS. Mice infected 28 days previously had a memory response as determined by HdAg-evoked increases in interleukin (IL)-4 and IL-10 from in vitro stimulated splenocytes and serum anti-H. diminuta IgG. Moreover, mice infected with 5 H. diminuta 28 days previously were protected from DNBS-induced colitis by secondary infection or 100 μg HdAg (ip.) at the time of DNBS treatment. An additional approach to managing inflammatory disease could be infection with H. diminuta followed by eliciting antiworm recall responses.

Murine models for mucosal tolerance in allergy

Immunity is established by a fine balance to discriminate between self and non-self. In addition, mucosal surfaces have the unique ability to establish and maintain a state of tolerance also against non-self constituents such as those represented by the large numbers of commensals populating mucosal surfaces and food-derived or air-borne antigens. Recent years have seen a dramatic expansion in our understanding of the basic mechanisms and the involved cellular and molecular players orchestrating mucosal tolerance. As a direct outgrowth, promising prophylactic and therapeutic models for mucosal tolerance induction against usually innocuous antigens (derived from food and aeroallergen sources) have been developed. A major theme in the past years was the introduction of improved formulations and novel adjuvants into such allergy vaccines. This review article describes basic mechanisms of mucosal tolerance induction and contrasts the peculiarities but also the interdependence of the gut and respiratory tract associated lymphoid tissues in that context. Particular emphasis is put on delineating the current prophylactic and therapeutic strategies to study and improve mucosal tolerance induction in allergy.

Myeloid Cell Phenotypes in Susceptibility and Resistance to Helminth Parasite Infections

Many major tropical diseases are caused by long-lived helminth parasites that are able to survive by modulation of the host immune system, including the innate compartment of myeloid cells. In particular, dendritic cells and macrophages show markedly altered phenotypes during parasite infections. In addition, many specialized subsets such as eosinophils and basophils expand dramatically in response to these pathogens. The changes in phenotype and function, and their effects on both immunity to infection and reactivity to bystander antigens such as allergens, are discussed.

Therapeutic potential of helminths in autoimmune diseases: helminth-derived immune-regulators and immune balance

Helminths have accompanied human throughout history by releasing immune-evasion molecules that could counteract an aberrant immune response within the host. In the past decades, helminth infections are becoming less prevalent possibly due to the developed sanitation. Meanwhile, the incidence of autoimmune diseases is increasing, which cannot be exclusively explained by the changes of susceptibility genes. While the hygiene hypothesis casts light on the problem. The infections of helminths are believed to interact with and regulate human immunity with the byproduct of suppressing the autoimmune diseases. Thus, helminths are potential to treat or cure the autoimmune diseases. The therapeutic progresses and possible immune suppression mechanisms are illustrated in the review. The helminths that are studied most intensively include Heligmosomoides polygyrus, Hymenolepis diminuta, Schistosoma mansoni, Trichinella spiralis, and Trichuris suis. Special attentions are paid on the booming animal models and clinical trials that are to detect the efficiency of immune-modulating helminth-derived molecules on autoimmune diseases. These trials provide us with a prosperous clinical perspective, but the precise mechanism of the down-regulatory immune response remains to be clarified. More efforts are needed to be dedicated until these parasite-derived immune modulators could be used in clinic to treat or cure the autoimmune diseases under a standard management.

Helminths in the gastrointestinal tract as modulators of immunity and pathology

Helminth parasites are highly prevalent in many low- and middle-income countries, in which inflammatory bowel disease and other immunopathologies are less frequent than in the developed world. Many of the most common helminths establish themselves in the gastrointestinal tract and can exert counter-inflammatory influences on the host immune system. For these reasons, interest has arisen as to how parasites may ameliorate intestinal inflammation and whether these organisms, or products they release, could offer future therapies for immune disorders. In this review, we discuss interactions between helminth parasites and the mucosal immune system, as well as the progress being made toward identifying mechanisms and molecular mediators through which it may be possible to attenuate pathology in the intestinal tract.

Nematodes and human therapeutic trials for inflammatory disease

Helminth infections likely provide a protective influence against some immune-mediated and metabolic diseases because helminth infection dramatically decreased in developed countries shortly before the explosive rise in the prevalence of these diseases. The capacity of helminths to activate immune-regulatory circuits in their hosts and to modulate the composition of intestinal flora appears to be the mechanisms of protective action. Animal models of disease show that various helminth species prevent and/or block inflammation in various organs in a diverse range of diseases. Clinical trials have demonstrated that medicinal exposure to Trichuris suis or small numbers of Necator americanus is safe with minor, if any, reported adverse effects. This includes exposure of inflamed intestine to T. suis, asthmathic lung to N. americanus and in patients with atopy. Efficacy has been suggested in some small studies, but is absent in others. Factors that may have led to inconclusive results in some trials are discussed. To date, there have been no registered clinical trials using helminths to treat metabolic syndrome or its component conditions. However, the excellent safety profile of T. suis or N. americanus suggests that such studies should be possible.

Suppression of colitis by adoptive transfer of helminth antigen-treated dendritic cells requires interleukin-4 receptor-α signaling

Infection with helminth parasites has been explored as a treatment for autoimmune and inflammatory diseases. As helminth antigens have potent immunomodulation properties capable of inducing regulatory programs in a variety of cell types, transferring cells treated with helminth antigens represents a novel extension to helminth therapy. Previous work determined that transfer of bone marrow-derived dendritic cells (DC) pulsed with a crude extract of the tapeworm Hymenolepis diminuta (HD) can suppress colitis in recipient mice. The present study explored the mechanism of disease suppression and the importance of interleukin (IL)-4 signaling. Transfer of HD-DCs suppressed dinitrobenzene sulfonic acid (DNBS)-induced colitis through activation of recipient IL-4 receptor-α. The transferred HD-DCs required IL-4Rα and the capacity to secrete IL-10 to drive IL-4 and IL-10 production and to suppress colitis in recipient mice. Treatment of DCs with IL-4 evokes an alternatively activated phenotype, but adoptive transfer of these cells did not affect the outcome of colitis. Collectively, these studies demonstrate the complexity between IL-4 and IL-10 in donor cells and recipient, and the requirement for parasite- and host-derived factors in this novel form of cell therapy. Thus IL-4Rα signaling is revealed as a pathway that could be exploited for helminth antigen cell-based therapy.

Helminth Regulation of Immunity: A Three-pronged Approach to Treat Colitis

By reputation, the parasite is a pariah, an unwelcome guest. Infection with helminth parasites evokes stereotypic immune responses in humans and mice that are dominated by T helper (Th)-2 responses; thus, a hypothesis arises that infection with helminths would limit immunopathology in concomitant inflammatory disease. Although infection with some species of helminths can cause devastating disease and affect the course of microbial infections, analyses of rodent models of inflammatory disease reveal that infection with helminth parasites, or treatment with helminth extracts, can limit the severity of autoinflammatory disease, including colitis. Intriguing, but fewer, studies show that adoptive transfer of myeloid immune cells treated with helminth products/extracts in vitro can suppress inflammation. Herein, 3 facets of helminth therapy are reviewed and critiqued: treatment with viable ova or larvae, treatment with crude extracts of the worm or purified molecules, and cellular immunotherapy. The beneficial effect of helminth therapy often converges on the mobilization of IL-10 and regulatory/alternatively activated macrophages, while there are reports on transforming growth factor (TGF)-β, regulatory T cells and dendritic cells, and recent data suggest that helminth-evoked changes in the microbiota should be considered when defining anticolitic mechanisms. We speculate that if the data from animal models translate to humans, noting the heterogeneity therein, then the choice between use of viable helminth ova, helminth extracts/molecules or antigen-pulsed immune cells could be matched to disease management in defined cohorts of patients with inflammatory bowel disease.

Downregulation of the Syk Signaling Pathway in Intestinal Dendritic Cells Is Sufficient To Induce Dendritic Cells That Inhibit Colitis

Helminthic infections modulate host immunity and may protect people in less-developed countries from developing immunological diseases. In a murine colitis model, the helminth Heligmosomoides polygyrus bakeri prevents colitis via induction of regulatory dendritic cells (DCs). The mechanism driving the development of these regulatory DCs is unexplored. There is decreased expression of the intracellular signaling pathway spleen tyrosine kinase (Syk) in intestinal DCs from H. polygyrus bakeri-infected mice. To explore the importance of this observation, it was shown that intestinal DCs from DC-specific Syk(-/-) mice were powerful inhibitors of murine colitis, suggesting that loss of Syk was sufficient to convert these cells into their regulatory phenotype. DCs sense gut flora and damaged epithelium via expression of C-type lectin receptors, many of which signal through the Syk signaling pathway. It was observed that gut DCs express mRNA encoding for C-type lectin (CLEC) 7A, CLEC9A, CLEC12A, and CLEC4N. H. polygyrus bakeri infection downmodulated CLEC mRNA expression in these cells. Focusing on CLEC7A, which encodes for the dectin-1 receptor, flow analysis showed that H. polygyrus bakeri decreases dectin-1 expression on the intestinal DC subsets that drive Th1/Th17 development. DCs become unresponsive to the dectin-1 agonist curdlan and fail to phosphorylate Syk after agonist stimulation. Soluble worm products can block CLEC7A and Syk mRNA expression in gut DCs from uninfected mice after a brief in vitro exposure. Thus, downmodulation of Syk expression and phosphorylation in intestinal DCs could be important mechanisms through which helminths induce regulatory DCs that limit colitis.

Regulation of the host immune system by helminth parasites

Helminth parasite infections are associated with a battery of immunomodulatory mechanisms that affect all facets of the host immune response to ensure their persistence within the host. This broad-spectrum modulation of host immunity has intended and unintended consequences, both advantageous and disadvantageous. Thus the host can benefit from suppression of collateral damage during parasite infection and from reduced allergic, autoimmune, and inflammatory reactions. However, helminth infection can also be detrimental in reducing vaccine responses, increasing susceptibility to coinfection and potentially reducing tumor immunosurveillance. In this review we will summarize the panoply of immunomodulatory mechanisms used by helminths, their potential utility in human disease, and prospective areas of future research.

Chronic Gastrointestinal Nematode Infection Mutes Immune Responses to Mycobacterial Infection Distal to the Gut

Helminth infections have been suggested to impair the development and outcome of Th1 responses to vaccines and intracellular microorganisms. However, there are limited data regarding the ability of intestinal nematodes to modulate Th1 responses at sites distal to the gut. In this study, we have investigated the effect of the intestinal nematode Heligmosomoides polygyrus bakeri on Th1 responses to Mycobacterium bovis bacillus Calmette-Guérin (BCG). We found that H. polygyrus infection localized to the gut can mute BCG-specific CD4(+) T cell priming in both the spleen and skin-draining lymph nodes. Furthermore, H. polygyrus infection reduced the magnitude of delayed-type hypersensitivity (DTH) to PPD in the skin. Consequently, H. polygyrus-infected mice challenged with BCG had a higher mycobacterial load in the liver compared with worm-free mice. The excretory-secretory product from H. polygyrus (HES) was found to dampen IFN-γ production by mycobacteria-specific CD4(+) T cells. This inhibition was dependent on the TGF-βR signaling activity of HES, suggesting that TGF-β signaling plays a role in the impaired Th1 responses observed coinfection with worms. Similar to results with mycobacteria, H. polygyrus-infected mice displayed an increase in skin parasite load upon secondary infection with Leishmania major as well as a reduction in DTH responses to Leishmania Ag. We show that a nematode confined to the gut can mute T cell responses to mycobacteria and impair control of secondary infections distal to the gut. The ability of intestinal helminths to reduce DTH responses may have clinical implications for the use of skin test-based diagnosis of microbial infections.

Helminth therapy for organic diseases?

Autoimmune and chronic inflammatory organic diseases represent a "postindustrial revolution epidemics," and their frequency has increased dramatically in the last century. Today, it is assumed that the increase in hygiene standards reduced the interactions with helminth parasites that coevolved with the immune system and are crucial for its proper functioning. Several helminths have been proposed and tested in the search of the ideal therapeutic. In this review, the authors summarize the translational and clinical studies and review the caveats and possible solutions for the optimization of helminth therapies.

Brugia malayi cystatin therapeutically ameliorates dextran sulfate sodium-induced colitis in mice

OBJECTIVE

Helminth immunomodulation in the host has been shown to have therapeutic implications in inflammatory bowel diseases. In this study we aimed to evaluate the therapeutic effect of Brugia malayi recombinant cystatin (rBmCys) in a dose-dependent manner on dextran sulfate sodium (DSS)-induced colitis in mice.

METHODS

The anti-inflammatory activity of rBmCys on mice peritoneal exudate cells was initially analyzed in vitro. BALB/c mice were fed with 5% DSS for 7 days to induce colitis. The colitis mice were treated intraperitoneally with rBmCys (10, 25 or 50 µg for the three different groups of mice) on days 1, 3 and 5 of the DSS administration. Disease severity was assessed by the disease activity index (DAI) and macroscopic and histopathological scores of colon and myeloperoxidase activity in colonic mucosa. Cytokine profiles were measured in sera and cultured splenocytes of treated mice followed by stimulation with rBmCys.

RESULTS

rBmCys showed anti-inflammatory activity in vitro. Treatment of DSS-induced colitis with rBmCys in mice ameliorated the overall disease severity as reflected by a significant reduction in weight loss, the DAI, mucosal edema, colon damage and myeloperoxidase activity of the colonic mucosa. While the mRNA expressions of IFN-γ, TNF-α, interleukin (IL)-5, IL-6 and IL-17 were downregulated, IL-10 expression was upregulated in the splenocytes of colitis mice treated with rBmCys. The amelioration of DSS-induced colitis occurred in a dose-dependent manner.

CONCLUSION

The results of this study indicate an anti-inflammatory potential of rBmCys and provide evidence for using this protein as a promising therapeutic agent in ulcerative colitis.

Adoptive transfer of helminth antigen-pulsed dendritic cells protects against the development of experimental colitis in mice

Infection with helminth parasites and treatment with worm extracts can suppress inflammatory disease, including colitis. Postulating that dendritic cells (DCs) participated in the suppression of inflammation and seeking to move beyond the use of helminths per se, we tested the ability of Hymenolepis diminuta antigen-pulsed DCs to suppress colitis as a novel cell-based immunotherapy. Bone marrow derived DCs pulsed with H. diminuta antigen (HD-DCs), or PBS-, BSA-, or LPS-DCs as controls, were transferred into wild-type (WT), interleukin-10 (IL-10) knock-out (KO), and RAG-1 KO mice, and the impact on dinitrobenzene sulphonic acid (DNBS)-induced colitis and splenic cytokine production assessed 72 h later. Mice receiving HD-DCs were significantly protected from DNBS-induced colitis and of the experimental groups only these mice displayed increased Th2 cytokines and IL-10 production. Adoptive transfer of HD-DCs protected neither RAG-1 nor IL-10 KO mice from DNBS-colitis. Furthermore, the transfer of CD4(+) splenocytes from recipients of HD-DCs protected naïve mice against DNBS-colitis, in an IL-10 dependent manner. Thus, HD-DCs are a novel anti-colitic immunotherapy that can educate anti-colitic CD4(+) T cells: mechanistically, the anti-colitic effect of HD-DCs requires that the host has an adaptive immune response and the ability to mobilize IL-10.

Parasite Proximity Drives the Expansion of Regulatory T Cells in Peyer's Patches following Intestinal Helminth Infection

Helminth infections are typically chronic in nature; however, the exact molecular mechanisms by which these parasites promote or thwart host immunity remain unclear. Worm expulsion requires the differentiation of CD4(+) T cells into Th2 cells, while regulatory T cells (Tregs) act to dampen the extent of the Th2 response. Priming of T cells requires drainage or capture of antigens within lymphoid tissues, and in the case of intestinal helminths, such sites include the mucosa-associated Peyer's patches (PPs) and the draining mesenteric lymph nodes (MLN). To gain insight into when and where the activation of the adaptive T cell response takes place following intestinal helminth infection, we analyzed Th2 and Treg responses in the PPs and MLN following infection with the murine intestinal helminth Heligmosomoides polygyrus bakeri. Protective Th2 responses were observed to be largely restricted to the MLN, while a greater expansion of Tregs occurred within the PPs. Interestingly, those PPs that formed a contact with the parasite showed the greatest degree of Treg expansion and no evidence of type 2 cytokine production, indicating that the parasite may secrete products that act in a local manner to selectively promote Treg expansion. This view was supported by the finding that H. polygyrus bakeri larvae could promote Treg proliferation in vitro. Taken together, these data indicate that different degrees of Treg expansion and type 2 cytokine production occur within the PPs and MLN following infection with the intestinal helminth H. polygyrus bakeri and indicate that these organs exhibit differential responses following infection with intestinal helminths.

Unraveling the Hygiene Hypothesis of helminthes and autoimmunity: origins, pathophysiology, and clinical applications

BACKGROUND

The Hygiene Hypothesis (HH) attributes the dramatic increase in autoimmune and allergic diseases observed in recent decades in Western countries to the reduced exposure to diverse immunoregulatory infectious agents. This theory has since largely been supported by strong epidemiological and experimental evidence.

DISCUSSION

The analysis of these data along with the evolution of the Western world's microbiome enable us to obtain greater insight into microorganisms involved in the HH, as well as their regulatory mechanisms on the immune system. Helminthes and their derivatives were shown to have a protective role. Helminthes' broad immunomodulatory properties have already begun to be exploited in clinical trials of autoimmune diseases, including inflammatory bowel disease, multiple sclerosis, rheumatoid arthritis, and type-1 diabetes.

SUMMARY

In this review, we will dissect the microbial actors thought to be involved in the HH as well as their immunomodulatory mechanisms as emphasized by experimental studies, with a particular attention on parasites. Thereafter, we will review the early clinical trials using helminthes' derivatives focusing on autoimmune diseases.

Helicobacter pylori-specific protection against inflammatory bowel disease requires the NLRP3 inflammasome and IL-18

BACKGROUND

The Gram-negative bacterium Helicobacter pylori is a constituent of the human gastric microbiota. Chronic infection with H. pylori causes gastritis and predisposes to gastric carcinoma but has also been inversely linked to various allergic and chronic inflammatory conditions. In particular, large meta-analyses have documented an inverse association between H. pylori infection and the risk of developing ulcerative colitis and Crohn's disease.

METHODS

We investigated possible protective effects of experimental H. pylori infection and of regular treatment with H. pylori extract in 2 mouse models of colitis and in mouse models of type I diabetes and multiple sclerosis. The mechanism of protection was examined in mouse strains lacking specific innate immune recognition pathways and cytokines.

RESULTS

We show here that experimental infection with H. pylori and administration of regular doses of H. pylori extract both alleviate the clinical and histopathological features of dextran sodium sulfate-induced chronic colitis and of T-cell transfer-induced colitis. High resolution endoscopy of the protected animals revealed the accumulation of large amounts of colonic mucus upon H. pylori exposure, which could be attributed to transcriptional activation of the mucin 2 gene. The protection against dextran sodium sulfate-induced colitis was dependent on the NLRP3 inflammasome and interleukin-18 signaling. Other autoimmune diseases, i.e., experimental autoimmune encephalomyelitis and type I diabetes, were not controlled by H. pylori.

CONCLUSIONS

In summary, we propose here that the immunomodulatory activity of an ancient constituent of the gut microbiota, H. pylori, may be exploited for the prevention and/or treatment of inflammatory bowel diseases.

IL-17RA in intestinal inflammation: structure, signaling, function, and clinical application

: Interleukin-17 receptor A (IL-17RA) is responsible for both IL-17A and IL-25 (IL-17E) signaling pathways. Current evidences suggest distinct but interactive responses between IL-17A and IL-25 signaling, both of which are critical for intestinal immune homeostasis. IL-17RA is assumed to regulate this counterbalance and therefore becomes a crucial molecule in mucosal immunology. In this review, we will describe the structure of IL-17RA, compare IL-17A and IL-25 signaling pathways, and emphasize on the function of IL-17RA in intestinal inflammation and discuss current evidences of accomplished and ongoing clinical trials with monoclonal antibodies targeting Th17 pathway, especially IL-17RA.

Intestinal helminths regulate lethal acute graft-versus-host disease and preserve the graft-versus-tumor effect in mice

Donor T lymphocyte transfer with hematopoietic stem cells suppresses residual tumor growth (graft-versus-tumor [GVT]) in cancer patients undergoing bone marrow transplantation (BMT). However, donor T cell reactivity to host organs causes severe and potentially lethal inflammation called graft-versus-host disease (GVHD). High-dose steroids or other immunosuppressive drugs are used to treat GVHD that have limited ability to control the inflammation while incurring long-term toxicity. Novel strategies are needed to modulate GVHD, preserve GVT, and improve the outcome of BMT. Regulatory T cells (Tregs) control alloantigen-sensitized inflammation of GVHD, sustain GVT, and prevent mortality in BMT. Helminths colonizing the alimentary tract dramatically increase the Treg activity, thereby modulating intestinal or systemic inflammatory responses. These observations led us to hypothesize that helminths can regulate GVHD and maintain GVT in mice. Acute GVHD was induced in helminth (Heligmosomoides polygyrus)-infected or uninfected BALB/c recipients of C57BL/6 donor grafts. Helminth infection suppressed donor T cell inflammatory cytokine generation and reduced GVHD-related mortality, but maintained GVT. H. polygyrus colonization promoted the survival of TGF-β-generating recipient Tregs after a conditioning regimen with total body irradiation and led to a TGF-β-dependent in vivo expansion/maturation of donor Tregs after BMT. Helminths did not control GVHD when T cells unresponsive to TGF-β-mediated immune regulation were used as donor T lymphocytes. These results suggest that helminths suppress acute GVHD using Tregs and TGF-β-dependent pathways in mice. Helminthic regulation of GVHD and GVT through intestinal immune conditioning may improve the outcome of BMT.

Splenic B cells from Hymenolepis diminuta-infected mice ameliorate colitis independent of T cells and via cooperation with macrophages

Helminth parasites provoke multicellular immune responses in their hosts that can suppress concomitant disease. The gut lumen-dwelling tapeworm Hymenolepis diminuta, unlike other parasites assessed as helminth therapy, causes no host tissue damage while potently suppressing murine colitis. With the goal of harnessing the immunomodulatory capacity of infection with H. diminuta, we assessed the putative generation of anti-colitic regulatory B cells following H. diminuta infection. Splenic CD19(+) B cells isolated from mice infected 7 [HdBc(7(d))] and 14 d (but not 3 d) previously with H. diminuta and transferred to naive mice significantly reduced the severity of dinitrobenzene sulfonic acid (DNBS)-, oxazolone-, and dextran-sodium sulfate-induced colitis. Mechanistic studies with the DNBS model, revealed the anti-colitic HdBc(7(d)) was within the follicular B cell population and its phenotype was not dependent on IL-4 or IL-10. The HdBc(7(d)) were not characterized by increased expression of CD1d, CD5, CD23, or IL-10 production, but did spontaneously, and upon LPS plus anti-CD40 stimulation, produce more TGF-β than CD19(+) B cells from controls. DNBS-induced colitis in RAG1(-/-) mice was inhibited by administration of HdBc(7(d)), indicating a lack of a requirement for T and B cells in the recipient; however, depletion of macrophages in recipient mice abrogated the anti-colitic effect of HdBc(7(d)). Thus, in response to H. diminuta, a putatively unique splenic CD19(+) B cell with a functional immunoregulatory program is generated that promotes the suppression of colitis dominated by TH1, TH2, or TH1-plus-TH2 events, and may do so via the synthesis of TGF-β and the generation of, or cooperation with, a regulatory macrophage.

Induction of regulatory cells by helminth parasites: exploitation for the treatment of inflammatory diseases

Helminth parasites are highly successful pathogens, chronically infecting a quarter of the world's population, causing significant morbidity but rarely causing death. Protective immunity and expulsion of helminths is mediated by T-helper 2 (Th2) cells, type 2 (M2) macrophages, type 2 innate lymphoid cells, and eosinophils. Failure to mount these type 2 immune responses can result in immunopathology mediated by Th1 or Th17 cells. Helminths have evolved a wide variety of approaches for immune suppression, especially the generation of regulatory T cells and anti-inflammatory cytokines interleukin-10 and transforming growth factor-β. This is a very effective strategy for subverting protective immune responses to prolong their survival in the host but has the bystander effect of modulating immune responses to unrelated antigens. Epidemiological studies in humans have shown that infection with helminth parasites is associated with a low incidence of allergy/asthma and autoimmunity in developing countries. Experimental studies in mice have demonstrated that regulatory immune responses induced by helminth can suppress Th2 and Th1/Th17 responses that mediate allergy and autoimmunity, respectively. This has provided a rational explanation of the 'hygiene hypothesis' and has also led to the exploitation of helminths or their immunomodulatory products in the development of new immunosuppressive therapies for inflammatory diseases in humans.

Helminth infections decrease host susceptibility to immune-mediated diseases

Helminthic infection has become rare in highly industrialized nations. Concurrent with the decline in helminthic infection has been an increase in the prevalence of inflammatory disease. Removal of helminths from our environment and their powerful effects on host immunity may have contributed to this increase. Several helminth species can abrogate disease in murine models of inflammatory bowel disease, type 1 diabetes, multiple sclerosis, and other conditions. Helminths evoke immune regulatory pathways often involving dendritic cells, regulatory T cells, and macrophages that help to control disease. Cytokines, such as IL-4, IL-10, and TGF-β, have a role. Notable is the helminthic modulatory effect on innate immunity, which impedes development of aberrant adaptive immunity. Investigators are identifying key helminth-derived immune modulatory molecules that may have therapeutic usefulness in the control of inflammatory disease.

Production and analysis of immunomodulatory excretory-secretory products from the mouse gastrointestinal nematode Heligmosomoides polygyrus bakeri

Heligmosomoides polygyrus bakeri (Hpb) infection in mice is a convenient model for studying the pathophysiology and immunology of gastrointestinal (GI) helminth infection. Hpb infection suppresses immune responses to bystander antigens and unrelated pathogens, and it slows the progression and modifies the outcome of immune-mediated diseases. Hpb-derived excretory-secretory (ES) products potently modulate CD4(+) helper T cell (TH) responses by inducing regulatory T cells, tolerogenic dendritic cells (DCs) and immunoregulatory cytokines. This observation has spiked interest in identifying the immunomodulatory molecules, especially proteins, in ES products from Hpb and other GI nematodes for development as novel therapies to treat individuals with immune-mediated diseases, such as inflammatory bowel diseases (IBDs). In this protocol, we describe how to (i) maintain Hpb in the laboratory for experimental infections, (ii) collect adult worms from infected mice to generate ES products and (iii) evaluate the modulatory effects of ES products on toll-like receptor (TLR) ligand-induced maturation of CD11c(+) DCs. The three major sections of the PROCEDURE can be used independently, and they require ∼6, 10 and 27 h, respectively. Although other methods use a modified Baermann apparatus to collect Hpb adult worms, we describe a method that involves dissection of adult worms from intestinal tissue. The protocol will be useful to investigators studying the host-parasite interface and identifying and analyzing helminth-derived molecules with therapeutic potential.