The helminth product, ES-62, protects against airway inflammation by resetting the Th cell phenotype

Succinate coenzyme A ligase β-like protein from Trichinella spiralis is a potential therapeutic molecule for allergic asthma

BACKGROUND

For decades, studies have demonstrated the anti-inflammatory potential of proteins secreted by helminths in allergies and asthma. Previous studies have demonstrated the immunomodulatory capabilities of Succinate Coenzyme A ligase beta-like protein (SUCLA-β) derived from Trichinella spiralis, a crucial excretory product of this parasite.

OBJECTIVE

To explore the therapeutic potential of SUCLA-β in alleviating and controlling ovalbumin (OVA)-induced allergic asthma, as well as its influence on host immune modulation.

METHODS

In this research, we utilized the rTs-SUCLA-β protein derived from T. spiralis to investigate its potential in mitigating airway inflammation in a murine model of asthma induced by OVA sensitization/stimulation, both pre- and post-challenge. The treatment's efficacy was assessed by quantifying the extent of inflammation in the lungs.

RESULTS

Treatment with rTs-SUCLA-β demonstrated efficacy in ameliorating OVA-induced airway inflammation, as evidenced by a reduction in eosinophil infiltration, levels of OVA-specific Immunoglobulin E, interferon-γ, interleukin (IL)-9, and IL-17A, along with an elevation in IL-10. The equilibrium between Th17 and Treg cells plays a pivotal role in modulating the abundance of inflammatory cells within the organism, thereby ameliorating inflammation and alleviating symptoms associated with allergic asthma.

CONCLUSIONS AND CLINICAL RELEVANCE

Our data revealed that T. spiralis-derived Ts-SUCLA-β protein may inhibit the allergic airway inflammation by regulating host immune responses.

Epigenetic changes induced by parasitic worms and their excretory-secretory products

Parasitic worms are pathogens of major medical and veterinary importance. They have evolved highly effective and sophisticated strategies of immune system manipulation, typically involving actively excreted/secreted (E-S) products. These molecules dampen and regulate the host immune responses that would otherwise result in parasite expulsion, thereby enabling the worms to survive in the host for many years, and they can also help prevent the potentially serious tissue damage that the worms can induce. Reflecting these E-S product-associated anti-inflammatory activities, there is also increasing evidence that parasitic worms and their products may serendipitously protect against allergic and autoimmune conditions and in addition, comorbidities of ageing that are associated with inflammatory responses, like type 2 diabetes and obesity. Research in this area has to date generally focused on identifying the cellular and effector targets of immunomodulation induced by the worm E-S products. However, increasing evidence that they can induce stably imprinted phenotypes of haematopoietic and stromal cells which promote their long-lasting survival has recently ignited interest in the ability of the molecules to epigenetically rewire cells to 'resolve and repair' phenotypes. Here, we review and discuss these new data in the context of their potential for exploitation in identifying novel gene signatures for the development of advanced and safe therapeutics for chronic inflammatory diseases.

Reduction in creatine metabolites in macrophages exposed to small molecule analogues of the anti-inflammatory parasitic worm product ES-62

ES-62, a protein secreted by Acanthocheilonema viteae, is anti-inflammatory by virtue of covalently attached phosphorylcholine (PC) residues and thus a library of drug-like small molecule analogues (SMAs) based on its PC moieties has been designed for therapeutic purposes. Two members, SMAs 11a and 12b, were previously found to suppress production of pro-inflammatory cytokines by mouse bone marrow-derived macrophages (BMMs) exposed to cytosine-phosphate-guanosine oligodeoxynucleotides (CpG), agonists for Toll-like receptor 9. In order to explore the mechanism of action underlying such activities, an untargeted mass spectrometry-based metabolomics screen was undertaken. Stimulation of BMMs with CpG produced significant metabolic changes relating to glycolysis and the TCA cycle but the SMAs had little impact on this. Also, the SMAs did not promote alterations in metabolites known to be associated with macrophage M1/M2 polarization. Rather, BMMs exposed to SMAs 11a or 12b prior to CpG treatment, or even alone, revealed downregulation of metabolites of creatine, a molecule whose major role is in the transport of high energy phosphate from the mitochondria to the cytosol. These data therefore provide insight into a possible mechanism of action of molecules with significant therapeutic potential that has not previously been described for parasitic worm products.

Protection against lung pathology during obesity-accelerated ageing in mice by the parasitic worm product ES-62

Mice develop pathology in the lungs as they age and this may be accelerated by a high calorie diet (HCD). ES-62 is a protein secreted by the parasitic worm Acanthocheilonema viteae that is immunomodulatory by virtue of covalently attached phosphorylcholine (PC) moieties. In this study, we show that weekly treatment of C57BL/6J mice with ES-62 protected against pathology in the lungs in male but not female mice fed a HCD from 10 weeks of age as shown by reductions in cellular infiltration and airway remodelling, particularly up to 160 days of age. ES-62 also reduced gene expression of the cytokines IL-4 and IL-17 and in addition the TLR/IL-1R adaptor MyD88, in the lungs of male mice although HCD-induced increases in these inflammatory markers were not detected until between 340 and 500 days of age. A combination of two drug-like ES-62 PC-based small molecule analogues (SMAs), produced broadly similar protective effects in the lungs of male mice with respect to both lung pathology and inflammatory markers, in addition to a decrease in HCD-induced IL-5 expression. Overall, our data show that ES-62 and its SMAs offer protection against HCD-accelerated pathological changes in the lungs during ageing. Given the targeting of Th2 cytokines and IL-17, we discuss this protection in the context of ES-62's previously described amelioration of airway hyper-responsiveness in mouse models of asthma.

Helminth-derived biomacromolecules as therapeutic agents for treating inflammatory and infectious diseases: What lessons do we get from recent findings?

Despite the tremendous progress in healthcare sectors, a number of life-threatening infectious, inflammatory, and autoimmune diseases are continuously challenging mankind throughout the globe. In this context, recent successes in utilizing helminth parasite-derived bioactive macromolecules viz. glycoproteins, enzymes, polysaccharides, lipids/lipoproteins, nucleic acids/nucleotides, and small organic molecules for treating various disorders primarily resulted from inflammation. Among the several parasites that infect humans, helminths (cestodes, nematodes, and trematodes) are known as efficient immune manipulators owing to their explicit ability to modulate and modify the innate and adaptive immune responses of humans. These molecules selectively bind to immune receptors on innate and adaptive immune cells and trigger multiple signaling pathways to elicit anti-inflammatory cytokines, expansion of alternatively activated macrophages, T-helper 2, and immunoregulatory T regulatory cell types to induce an anti-inflammatory milieu. Reduction of pro-inflammatory responses and repair of tissue damage by these anti-inflammatory mediators have been exploited for treating a number of autoimmune, allergic, and metabolic diseases. Herein, the potential and promises of different helminths/helminth-derived products as therapeutic agents in ameliorating immunopathology of different human diseases and their mechanistic insights of function at cell and molecular level alongside the molecular signaling cross-talks have been reviewed by incorporating up-to-date findings achieved in the field.

Foxp2 inhibits Th9 cell differentiation and attenuates allergic airway inflammation in a mouse model of ovalbumin-induced asthma

This study aimed to explore the effects of forkhead box P2 gene (Foxp2) on T-helper 9 (Th9) differentiation in asthmatic mice. An in vivo asthmatic mouse model was induced with ovalbumin (OVA). An in vitro model was established by culturing CD4⁺ T cells with TGF-β, IL-4, and anti-IFN-γ. ELISA, flow cytometry, qRT-PCR and Western blot were performed to examine IL-9 secretion, Th9 cell number, and Th9 cell transcription factor expression, respectively. Pathological changes in lung tissues and airway mucus secretion were assessed with HE and PAS glycogen staining. Anti-IL-9 mAb reversed the elevation in Th9 cells and IL-9 expression in lung tissues and bronchoalveolar lavage fluid (BALF) of asthmatic mice. Foxp2 was downregulated in BALF and lung tissue of asthmatic mice and Th9 cells. Overexpression of Foxp2 inhibited Th9 cell differentiation in vitro and improved airway inflammation in vivo. Our study suggests that overexpression of Foxp2 attenuates allergic asthma by inhibiting Th9 cell differentiation.

Mini Review: Structure and Function of Nematode Phosphorylcholine-Containing Glycoconjugates

An unusual aspect of the biology of nematodes is the covalent attachment of phosphorylcholine (PC) to carbohydrate in glycoconjugates. Investigation of the structure of these molecules by ever-increasingly sophisticated analytical procedures has revealed that PC is generally in phosphodiester linkage with C6 of N-acetylglucosamine (GlcNAc) in both N-type glycans and glycosphingolipids. Up to five PC groups have been detected in the former, being located on both antenna and core GlcNAc. The PC donor for transfer to carbohydrate appears to be phosphatidylcholine but the enzyme responsible for transfer remains to be identified. Work primarily involving the PC-containing Acanthocheilonema viteae secreted product ES-62, has shown that the PC attached to nematode N-glycans possesses a range of immunomodulatory properties, subverting for example, pro-inflammatory signalling in various immune system cell-types including lymphocytes, mast cells, dendritic cells and macrophages. This has led to the generation of PC-based ES-62 small molecule analogues (SMAs), which mirror the parent molecule in preventing the initiation or progression of disease in mouse models of a number of human conditions associated with aberrant inflammatory responses. These include rheumatoid arthritis, systemic lupus erythematosus and lung and skin allergy such that the SMAs are considered to have widespread therapeutic potential.

A Helminth-Derived Chitinase Structurally Similar to Mammalian Chitinase Displays Immunomodulatory Properties in Inflammatory Lung Disease

Immunomodulation of airway hyperreactivity by excretory-secretory (ES) products of the first larval stage (L1) of the gastrointestinal nematode Trichuris suis is reported by us and others. Here, we aimed to identify the proteins accounting for the modulatory effects of the T. suis L1 ES proteins and studied six selected T. suis L1 proteins for their immunomodulatory efficacy in a murine OVA-induced allergic airway disease model. In particular, an enzymatically active T. suis chitinase mediated amelioration of clinical signs of airway hyperreactivity, primarily associated with suppression of eosinophil recruitment into the lung, the associated chemokines, and increased numbers of RELMα⁺ interstitial lung macrophages. While there is no indication of T. suis chitinase directly interfering with dendritic cell activation or antigen presentation to CD4 T cells, treatment of allergic mice with the worm chitinase influenced the hosts' own chitinase activity in the inflamed lung. The three-dimensional structure of the T. suis chitinase as determined by high-resolution X-ray crystallography revealed high similarities to mouse acidic mammalian chitinase (AMCase) but a unique ability of T. suis chitinase to form dimers. Our data indicate that the structural similarities between the parasite and host chitinase contribute to the disease-ameliorating effect of the helminth-derived chitinase on allergic lung inflammation.

Immunoprotective inference of experimental chronic Trichinella spiralis infection on house dust mites induced allergic airway remodeling

Allergic bronchial asthma is characterized by chronic inflammation of the respiratory airways mediated by T-helper 2 (Th2), Th17 and their cytokines. Although most asthmatic patients suffer from allergic airway remodeling (AAR), aggressive anti-allergic treatment failed to reverse it. The hygiene hypothesis illuminated the counter relationship between allergy and helminthic infections. The immune system is modulated by Trichinella spiralis (T. spiralis) infection to maintain homeostasis. Therefore, this work aimed to investigate the impact of chronic T. spiralis infection on induced AAR in C57BL/6 mice sensitized by house dust mites (HDM) allergens. Forty mice were divided into 3 groups: I (10 healthy mice), IΙ (15 HDM sensitized mice), and ΙΙI (15 T. spiralis chronically infected mice and sensitized with HDM allergens). The assessment aimed to evaluate the effects of regulatory CD4+CD25+FOXP3+ cells (Tregs) and their cytokines comparative to hypersensitivity mediated cytokines. Chronic T. spiralis infection effectively prevented the host's AAR. This result was evidenced by upregulated Tregs in blood by flow cytometric analysis and increased interleukin-10 (IL-10) levels in bronchoalveolar lavage (BAL) by Enzyme linked immunosorbent assay (ELISA) as well as improved lung histopathological changes. Also, serum HDM specific immunoglobulin E (IgE), BAL eosinophils, BAL IL-5 levels, and IL-17 gene expression in lung tissues were significantly reduced in T. spiralis chronically infected mice. In conclusion, the immune response in chronic T. spiralis infection could provide a promising mechanistic tool for protection against AAR, which paves the way for innovative preventive measures of other immunological disorders.

The Functional Parasitic Worm Secretome: Mapping the Place of Onchocerca volvulus Excretory Secretory Products

Nematodes constitute a very successful phylum, especially in terms of parasitism. Inside their mammalian hosts, parasitic nematodes mainly dwell in the digestive tract (geohelminths) or in the vascular system (filariae). One of their main characteristics is their long sojourn inside the body where they are accessible to the immune system. Several strategies are used by parasites in order to counteract the immune attacks. One of them is the expression of molecules interfering with the function of the immune system. Excretory-secretory products (ESPs) pertain to this category. This is, however, not their only biological function, as they seem also involved in other mechanisms such as pathogenicity or parasitic cycle (molting, for example). We will mainly focus on filariae ESPs with an emphasis on data available regarding Onchocerca volvulus, but we will also refer to a few relevant/illustrative examples related to other worm categories when necessary (geohelminth nematodes, trematodes or cestodes). We first present Onchocerca volvulus, mainly focusing on the aspects of this organism that seem relevant when it comes to ESPs: life cycle, manifestations of the sickness, immunosuppression, diagnosis and treatment. We then elaborate on the function and use of ESPs in these aspects.

Development of Acanthocheilonema viteae in Meriones shawi: Absence of microfilariae and production of active ES-62

AIMS

ES-62 is a well-studied anti-inflammatory molecule secreted by L4-adult stage Acanthocheilonema viteae. We maintain the life cycle of A viteae using Meriones libycus as the definitive host. Here, we investigated whether the full life cycle could be maintained, and functional ES-62 produced, in a related jird species-Meriones shawi.

METHODS AND RESULTS

Adult worms were produced in comparable numbers in the two species, but very few microfilariae (MF) were observed in the M shawi bloodstream. M shawi ES-62 produced ex vivo was functional and protective in a mouse model of arthritis. Myeloid-derived cells from naïve and infected jirds of both species were compared with respect to ROS production and osteoclast generation, and some differences between the two species in both the absence and presence of infection were observed.

CONCLUSIONS

The life cycle of A viteae cannot be successfully completed in M shawi jirds but L3 stage worms develop to adulthood and produce functional ES-62. Preliminary investigation into jird immune responses suggests that infection can differentially modulate myeloid responses in the two species. However, species-specific reagents are required to understand the complex interplay between A viteae and its host and to explain the lack of circulating MF in infected M shawi jirds.

Harnessing helminth-driven immunoregulation in the search for novel therapeutic modalities

Parasitic helminths have coevolved with humans over millennia, intricately refining and developing an array of mechanisms to suppress or skew the host’s immune system, thereby promoting their long-term survival. Some helminths, such as hookworms, cause little to no overt pathology when present in modest numbers and may even confer benefits to their human host. To exploit this evolutionary phenomenon, clinical trials of human helminth infection have been established and assessed for safety and efficacy for a range of immune dysfunction diseases and have yielded mixed outcomes. Studies of live helminth therapy in mice and larger animals have convincingly shown that helminths and their excretory/secretory products possess anti-inflammatory drug-like properties and represent an untapped pharmacopeia. These anti-inflammatory moieties include extracellular vesicles, proteins, glycans, post-translational modifications, and various metabolites. Although the concept of helminth-inspired therapies holds promise, it also presents a challenge to the drug development community, which is generally unfamiliar with foreign biologics that do not behave like antibodies. Identification and characterization of helminth molecules and vesicles and the molecular pathways they target in the host present a unique opportunity to develop tailored drugs inspired by nature that are efficacious, safe, and have minimal immunogenicity. Even so, much work remains to mine and assess this out-of-the-box therapeutic modality. Industry-based organizations need to consider long-haul investments aimed at unraveling and exploiting unique and differentiated mechanisms of action as opposed to toe-dipping entries with an eye on rapid and profitable turnarounds.

Therapeutic applicability of helminths in autoimmune diseases - literature overview

This paper presents an overview of published studies conducted on helminths – parasites of the human gastrointestinal tract. Making use of their ability for immunomodulation may lead to the introduction of effective therapies for autoimmune diseases. This paper presents chronologically attempts to treat autoimmune diseases not only of the gastrointestinal tract, but also of the nervous and endocrine systems, which have been undertaken for decades. The overview of analysed reports demonstrates that as medical knowledge on the cells and mediators participating actively in inflammatory processes accumulates, clinical trials focus on ever more specific areas concerning the pathomechanisms of autoimmune diseases. The outcomes of clinical trials conducted both on animals and humans give reasons to assume that the modification of the human intestinal microflora may be the key to fighting against these diseases.

Synthetic small molecule analogues of the immunomodulatory Acanthocheilonema viteae product ES-62 promote metabolic homeostasis during obesity in a mouse model

One of the most rapidly increasing human public health problems is obesity, whose sequelae like type-2 diabetes, represent continuously worsening, life-long conditions. Over the last 15 years, data have begun to emerge from human and more frequently, mouse studies, that support the idea that parasitic worm infection can protect against this condition. We have therefore investigated the potential of two synthetic small molecule analogues (SMAs) of the anti-inflammatory Acanthocheilonema viteae product ES-62, to protect against metabolic dysfunction in a C57BL/6 J mouse model of high calorie diet-induced obesity. We found weekly subcutaneous administration of the SMAs in combination (1 μg of each), starting one week before continuous exposure to high calorie diet (HCD), decreased fasting glucose levels and reversed the impaired glucose clearance observed in male mice, when measured at approximately 7 and 13 weeks after exposure to HCD. Fasting glucose levels were also-reduced in male mice fed a HCD for some 38 weeks when given SMA-treatment 13 weeks after the start of HCD, indicating an SMA-therapeutic potential. For the most part, protective effects were not observed in female mice. SMA treatment also conferred protection against each of reduced ileum villus length and liver fibrosis, but more prominently in female mice. Previous studies in mice indicate that protection against metabolic dysfunction is usually associated with polarisation of the immune system towards a type-2/anti-inflammatory direction but our attempts to correlate improved metabolic parameters with such changes were unsuccessful. Further analysis will therefore be required to define mechanism of action. Nevertheless, overall our data clearly show the potential of the drug-like SMAs as a preventative or treatment for metabolic dysregulation associated with obesity.

The parasitic worm product ES-62 normalises the gut microbiota bone marrow axis in inflammatory arthritis

The human immune system has evolved in the context of our colonisation by bacteria, viruses, fungi and parasitic helminths. Reflecting this, the rapid eradication of pathogens appears to have resulted in reduced microbiome diversity and generation of chronically activated immune systems, presaging the recent rise of allergic, autoimmune and metabolic disorders. Certainly, gastrointestinal helminths can protect against gut and lung mucosa inflammatory conditions by modulating the microbiome and suppressing the chronic inflammation associated with dysbiosis. Here, we employ ES-62, an immunomodulator secreted by tissue-dwelling Acanthocheilonema viteae to show that helminth-modulation of the gut microbiome does not require live infection with gastrointestinal-based worms nor is protection restricted to mucosal diseases. Specifically, subcutaneous administration of this defined immunomodulator affords protection against joint disease in collagen-induced arthritis, a mouse model of rheumatoid arthritis, which is associated with normalisation of gut microbiota and prevention of loss of intestinal barrier integrity.

Helminth therapy for autism under gut-brain axis- hypothesis

Autism is a neurodevelopmental disease included within Autism Syndrome Disorder (ASD) spectrum. ASD has been linked to a series of genes that play a role in immune response function and patients with autism, commonly suffer from immune-related comorbidities. Despite the complex pathophysiology of autism, Gut-brain axis is gaining strength in the understanding of several neurological disorders. In addition, recent publications have shown the correlation between immune dysfunctions, gut microbiota and brain with the behavioral alterations and comorbid symptoms found in autism. Gut-brain axis acts as the "second brain", in a communication network established between neural, endocrine and the immunological systems. On the other hand, Hygiene Hypothesis suggests that the increase in the incidence of autoimmune diseases in the modern world can be attributed to the decrease of exposure to infectious agents, as parasitic nematodes. Helminths induce modulatory and protective effects against several inflammatory disorders, maintaining gastrointestinal homeostasis and modulating brain functions. Helminthic therapy has been previously performed in diseases such as ulcerative colitis, Crohn's disease, diabetes, multiple sclerosis, asthma, rheumatoid arthritis, and food allergies. Considering gut-brain axis, Hygiene Hypothesis, and the modulatory effects of helminths I hypothesized that a treatment with Trichuris suis soluble products represents a feasible holistic treatment for autism, and the key for the development of novel treatments. Preclinical studies are required to test this hypothesis.

Failure of the Anti-Inflammatory Parasitic Worm Product ES-62 to Provide Protection in Mouse Models of Type I Diabetes, Multiple Sclerosis, and Inflammatory Bowel Disease

Parasitic helminths and their isolated secreted products show promise as novel treatments for allergic and autoimmune conditions in humans. Foremost amongst the secreted products is ES-62, a glycoprotein derived from Acanthocheilonema viteae, a filarial nematode parasite of gerbils, which is anti-inflammatory by virtue of covalently-attached phosphorylcholine (PC) moieties. ES-62 has been found to protect against disease in mouse models of rheumatoid arthritis, systemic lupus erythematosus, and airway hyper-responsiveness. Furthermore, novel PC-based synthetic small molecule analogues (SMAs) of ES-62 have recently been demonstrated to show similar anti-inflammatory properties to the parent molecule. In spite of these successes, we now show that ES-62 and its SMAs are unable to provide protection in mouse models of certain autoimmune conditions where other helminth species or their secreted products can prevent disease development, namely type I diabetes, multiple sclerosis and inflammatory bowel disease. We speculate on the reasons underlying ES-62's failures in these conditions and how the negative data generated may help us to further understand ES-62's mechanism of action.

Synthetic analogues of the parasitic worm product ES-62 reduce disease development in in vivo models of lung fibrosis

Parasitic worms are receiving much attention as a potential new therapeutic approach to treating autoimmune and allergic conditions but concerns remain regarding their safety. As an alternative strategy, we have focused on the use of defined parasitic worm products and recently taken this one step further by designing drug-like small molecule analogues of one such product, ES-62, which is anti-inflammatory by virtue of covalently attached phosphorylcholine moieties. Previously, we have shown that ES-62 mimics are efficacious in protecting against disease in mouse models of rheumatoid arthritis, systemic lupus erythematosus and skin and lung allergy. Given the potential role of chronic inflammation in fibrosis, in the present study we have focused our attention on lung fibrosis, a debilitating condition for which there is no cure and which in spite of treatment slowly gets worse over time. Two mouse models of fibrosis - bleomycin-induced and LPS-induced - in which roles for inflammation have been implicated were adopted. Four ES-62 analogues were tested - 11a and 12b, previously shown to be active in mouse models of allergic and autoimmune disease and 16b and AIK-29/62 both of which are structurally related to 11a. All four compounds were found to significantly reduce disease development in both fibrosis models, as shown by histopathological analysis of lung tissue, indicating their potential as treatments for this condition.

Nanomedicine Approaches Against Parasitic Worm Infections

Nanomedicine approaches have the potential to transform the battle against parasitic worm (helminth) infections, a major global health scourge from which billions are currently suffering. It is anticipated that the intersection of two currently disparate fields, nanomedicine and helminth biology, will constitute a new frontier in science and technology. This progress report surveys current innovations in these research fields and discusses research opportunities. In particular, the focus is on: (1) major challenges that helminth infections impose on mankind; (2) key aspects of helminth biology that inform future research directions; (3) efforts to construct nanodelivery platforms to target drugs and genes to helminths hidden in their hosts; (4) attempts in applying nanotechnology to enable vaccination against helminth infections; (5) outlooks in utilizing nanoparticles to enhance immunomodulatory activities of worm-derived factors to cure allergy and autoimmune diseases. In each section, achievements are summarized, limitations are explored, and future directions are assessed.

IL-33/ST2 signalling and crosstalk with FcεRI and TLR4 is targeted by the parasitic worm product, ES-62

ES-62 is a secreted parasitic worm-derived immunomodulator that exhibits therapeutic potential in allergy by downregulating aberrant MyD88 signalling to normalise the inflammatory phenotype and mast cell responses. IL-33 plays an important role in driving mast cell responses and promoting type-2 allergic inflammation, particularly with respect to asthma, via MyD88-integrated crosstalk amongst the IL-33 receptor (ST2), TLR4 and FcεRI. We have now investigated whether ES-62 targets this pathogenic network by subverting ST2-signalling, specifically by characterising how the functional outcomes of crosstalk amongst ST2, TLR4 and FcεRI are modulated by the worm product in wild type and ST2-deficient mast cells. This analysis showed that whilst ES-62 inhibits IL-33/ST2 signalling, the precise functional modulation observed varies with receptor usage and/or mast cell phenotype. Thus, whilst ES-62’s harnessing of the capacity of ST2 to sequester MyD88 appears sufficient to mediate its inhibitory effects in peritoneal-derived serosal mast cells, downregulation of MyD88 expression appears to be required to dampen the higher levels of cytokine production typically released by bone marrow-derived mucosal mast cells.

Small Molecule Analogues of the parasitic worm product ES-62 interact with the TIR domain of MyD88 to inhibit pro-inflammatory signalling

ES-62 is a protein secreted by the parasitic worm Acanthocheilonema viteae that is anti-inflammatory by virtue of covalently attached phosphorylcholine. Previously we have reported that drug-like Small Molecule Analogues (SMAs) of its phosphorylcholine moiety can mimic ES-62 in protecting against disease development in certain mouse models of autoimmune and allergic conditions, due to them causing partial degradation of the TLR/IL-1R adaptor MyD88. We have now taken a molecular modelling approach to investigating the mechanism underlying this effect and this predicts that the SMAs interact directly with the MyD88 TIR domain. Further support for this is provided by assay of LPS-induced MyD88/NF-κB-driven secreted alkaline phosphatase (SEAP) reporter activity in commercially-available stably transfected (TLR4-MD2-NF-κB-SEAP) HEK293 cells, as SMA12b-mediated inhibition of such SEAP activity is blocked by its pre-incubation with recombinant MyD88-TIR domain. Direct binding of SMA12b to the TIR domain is also shown to inhibit homo-dimerization of the adaptor, an event that can explain the observed degradation of the adaptor and inhibition of subsequent downstream signalling. Thus, these new data identify initial events by which drug-like ES-62 SMAs, which we also demonstrate are able to inhibit cytokine production by human cells, homeostatically maintain "safe" levels of MyD88 signalling.

Helminth Modulation of Lung Inflammation

Parasitic helminths must establish chronic infections to complete their life cycle and therefore are potent modulators of multiple facets of host physiology. Parasitic helminths have coevolved with humans to become arguably master selectors of our immune system, whereby they have impacted on the selection of genes with beneficial mutations for both host and parasite. While helminth infections of humans are a significant health burden, studies have shown that helminths or helminth products can alter susceptibility to unrelated infectious or inflammatory diseases. This has generated interest in the use of helminth infections or molecules as therapeutics. In this review, we focus on the impact of helminth infections on pulmonary immunity, especially with regard to homeostatic lung function, pulmonary viral and bacterial (co)infections, and asthma.

Hookworm recombinant protein promotes regulatory T cell responses that suppress experimental asthma

In the developed world, declining prevalence of some parasitic infections correlates with increased incidence of allergic and autoimmune disorders. Moreover, experimental human infection with some parasitic worms confers protection against inflammatory diseases in phase 2 clinical trials. Parasitic worms manipulate the immune system by secreting immunoregulatory molecules that offer promise as a novel therapeutic modality for inflammatory diseases. We identify a protein secreted by hookworms, anti-inflammatory protein-2 (AIP-2), that suppressed airway inflammation in a mouse model of asthma, reduced expression of costimulatory markers on human dendritic cells (DCs), and suppressed proliferation ex vivo of T cells from human subjects with house dust mite allergy. In mice, AIP-2 was primarily captured by mesenteric CD103⁺ DCs and suppression of airway inflammation was dependent on both DCs and Foxp3⁺ regulatory T cells (T_regs) that originated in the mesenteric lymph nodes (MLNs) and accumulated in distant mucosal sites. Transplantation of MLNs from AIP-2-treated mice into naïve hosts revealed a lymphoid tissue conditioning that promoted T_reg induction and long-term maintenance. Our findings indicate that recombinant AIP-2 could serve as a novel curative therapeutic for allergic asthma and potentially other inflammatory diseases.

The Notch pathway inhibitor stapled α-helical peptide derived from mastermind-like 1 (SAHM1) abrogates the hallmarks of allergic asthma

BACKGROUND

The Notch signaling pathway has been implicated in the pathogenesis of allergic airway inflammation. Targeting the active Notch transactivation complex by using the cell-permeable, hydrocarbon-stapled synthetic peptide stapled α-helical peptide derived from mastermind-like 1 (SAHM1) resulted in genome-wide suppression of Notch-activated genes in leukemic cells and other models. However, the efficacy of SAHM1 in allergic asthma models has remained unexplored.

OBJECTIVE

We aimed to investigate the therapeutic efficacy of SAHM1 in a house dust mite (HDM)-driven asthma model.

METHODS

Topical therapeutic intervention with SAHM1 or a control peptide was performed during sensitization, challenge, or both with HDM in mice. Airway inflammation was assessed by using multicolor flow cytometry, and bronchial hyperreactivity was studied. Additionally, SAHM1 therapy was investigated in mice with established allergic airway inflammation and in a model in which we neutralized IFN-γ during HDM challenge to support the T_H2 response and exacerbate asthma.

RESULTS

SAHM1 treatment during the challenge phase led to a marked reduction of eosinophil and T cell numbers in bronchoalveolar lavage fluid compared with those in diluent-treated or control peptide-treated mice. Likewise, T-cell cytokine content and bronchial hyperreactivity were reduced. SAHM1 treatment dampened T_H2 inflammation during ongoing HDM challenge and enhanced recovery after established asthma. Additionally, in the presence of anti-IFN-γ antibodies, SAHM1 downregulated expression of the key T_H2 transcription factor GATA3 and intracellular IL-4 in bronchoalveolar lavage fluid T cells, but expression of the T_H17 transcription factor retinoic acid-related orphan receptor γt or intracellular IL-17 was not affected. SAHM1 therapy also reduced serum IgE levels.

CONCLUSIONS

Therapeutic intervention of Notch signaling by SAHM1 inhibits allergic airway inflammation in mice and is therefore an interesting new topical treatment opportunity in asthmatic patients.

The immunology of the allergy epidemic and the hygiene hypothesis

The immunology of the hygiene hypothesis of allergy is complex and involves the loss of cellular and humoral immunoregulatory pathways as a result of the adoption of a Western lifestyle and the disappearance of chronic infectious diseases. The influence of diet and reduced microbiome diversity now forms the foundation of scientific thinking on how the allergy epidemic occurred, although clear mechanistic insights into the process in humans are still lacking. Here we propose that barrier epithelial cells are heavily influenced by environmental factors and by microbiome-derived danger signals and metabolites, and thus act as important rheostats for immunoregulation, particularly during early postnatal development. Preventive strategies based on this new knowledge could exploit the diversity of the microbial world and the way humans react to it, and possibly restore old symbiotic relationships that have been lost in recent times, without causing disease or requiring a return to an unhygienic life style.

Parasites and asthma

Nowadays, many studies have found low morbidity of asthma in epidemic areas of parasitic diseases, as shown by the hygiene hypothesis. It is obvious that some parasite infections can prevent asthma and studies have been carried out to clarify the mechanism of the preventive effect and search for the future asthmatic therapies. Previous findings have indicated that this mechanism may be related to the immune response switching from Th1 to Th2 and important cells induced by parasites, including the regulatory T cells, regulatory B cells, dendrite cells, and alternatively activated macrophages. Cytokine IL-10 also plays a nonredundant role in protection against allergic airway inflammation in asthma. This review focuses on the relationship between parasites and asthma, and the potential protection mechanism involved.

Dendritic cells provide a therapeutic target for synthetic small molecule analogues of the parasitic worm product, ES-62

ES-62, a glycoprotein secreted by the parasitic filarial nematode Acanthocheilonema viteae, subverts host immune responses towards anti-inflammatory phenotypes by virtue of covalently attached phosphorylcholine (PC). The PC dictates that ES-62 exhibits protection in murine models of inflammatory disease and hence a library of drug-like PC-based small molecule analogues (SMAs) was synthesised. Four sulfone-containing SMAs termed 11a, 11e, 11i and 12b were found to reduce mouse bone marrow-derived dendritic cell (DC) pathogen-associated molecular pattern (PAMP)-induced pro-inflammatory cytokine production, inhibit NF-κB p65 activation, and suppress LPS-induced up-regulation of CD40 and CD86. Active SMAs also resulted in a DC phenotype that exhibited reduced capacity to prime antigen (Ag)-specific IFN-γ production during co-culture with naïve transgenic TCR DO.11.10 T cells in vitro and reduced their ability, following adoptive transfer, to prime the expansion of Ag-specific T lymphocytes, specifically TH17 cells, in vivo. Consistent with this, mice receiving DCs treated with SMAs exhibited significantly reduced severity of collagen-induced arthritis and this was accompanied by a significant reduction in IL-17+ cells in the draining lymph nodes. Collectively, these studies indicate that drug-like compounds that target DCs can be designed from parasitic worm products and demonstrate the potential for ES-62 SMA-based DC therapy in inflammatory disease.

Parasite excretory-secretory products and their effects on metabolic syndrome

Obesity, one of the main causes of metabolic syndrome (MetS), is an increasingly common health and economic problem worldwide, and one of the major risk factors for developing type 2 diabetes and cardiovascular disease. Chronic, low-grade inflammation is associated with MetS and obesity. A dominant type 2/anti-inflammatory response is required for metabolic homoeostasis within adipose tissue: during obesity, this response is replaced by infiltrating, inflammatory macrophages and T cells. Helminths and certain protozoan parasites are able to manipulate the host immune response towards a TH2 immune phenotype that is beneficial for their survival, and there is emerging data that there is an inverse correlation between the incidence of MetS and helminth infections, suggesting that, as with autoimmune and allergic diseases, helminths may play a protective role against MetS disease. Within this review, we will focus primarily on the excretory-secretory products that the parasites produce to modulate the immune system and discuss their potential use as therapeutics against MetS and its associated pathologies.

The helminth product, ES-62 modulates dendritic cell responses by inducing the selective autophagolysosomal degradation of TLR-transducers, as exemplified by PKCδ

We have previously shown that ES-62, a phosphorylcholine (PC)-containing glycoprotein secreted by the parasitic filarial nematode Acanthocheilonema viteae targets dendritic cell (DC) responses, specifically by suppressing TLR4 signalling to inhibit Th1/Th17-driven inflammation. We have now investigated the molecular mechanisms underpinning such immunomodulation and show here that ES-62-mediated downregulation of protein kinase C-δ (PKC-δ), a TLR4-associated signalling mediator required for full activation of LPS-driven pro-inflammatory responses, is associated with induction of a low level of autophagic flux, as evidenced by upregulation and trafficking of p62 and LC3 and their consequent autophagolysosomal degradation. By contrast, the classical TLR4 ligand LPS, strongly upregulates p62 and LC3 expression but under such canonical TLR4 signalling this upregulation appears to reflect a block in autophagic flux, with these elements predominantly degraded in a proteasomal manner. These data are consistent with autophagic flux acting to homeostatically suppress proinflammatory DC responses and indeed, blocking of PKC-δ degradation by the autophagolysosomal inhibitors, E64d plus pepstatin A, results in abrogation of the ES-62-mediated suppression of LPS-driven release of IL-6, IL-12p70 and TNF-α by DCs. Thus, by harnessing this homeostatic regulatory mechanism, ES-62 can protect against aberrant inflammation, either to promote parasite survival or serendipitously, exhibit therapeutic potential in inflammatory disease.

Immunomodulatory effects of adult Haemonchus contortus excretory/secretory products on human monocyte-derived dendritic cells

The levels of expression of surface molecules and release of cytokines and chemokines of human monocyte-derived dendritic cells were determined after their exposure to adult H. contortus excretory/secretory (ES) products or a combination of ES products and bacterial lipopolysaccharide (LPS). Worm products provoked a weak response and only partial maturation of the dendritic cells, consistent with the hyporesponsiveness and more tolerogenic immune environment present in parasitized animals and humans. Co-stimulation with LPS demonstrated that H. contortus secretions, like those of other helminths, contain immunomodulators capable of reducing some aspects of the strong T(H)1/T(H)2 response evoked by bacterial LPS. There were significant reductions in the release of some cytokine/chemokines by LPS-stimulated mdDCs and a trend (although not significant at P < 0.05) for reduced expression levels of CD40, CD80 and HLA-DR. A prominent feature was the variability in responses of dendritic cells from the four donors, even on different days in repeat experiments, suggesting that generalized conclusions may be difficult to make, except in genetically related animals. Such observations may therefore be applicable only to restricted populations. In addition, previous exposure to parasites in a target population for immunomodulatory therapy may be an important factor in assessing the likelihood of adverse reactions or failures in the treatment to worm therapy.

Testing small molecule analogues of the Acanthocheilonema viteae immunomodulator ES-62 against clinically relevant allergens

ES-62 is a glycoprotein secreted by the filarial nematode Acanthocheilonema viteae that protects against ovalbumin (OVA)-induced airway hyper-responsiveness in mice by virtue of covalently attached anti-inflammatory phosphorylcholine (PC) residues. We have recently generated a library of small molecule analogues (SMAs) of ES-62 based around its active PC moiety as a starting point in novel drug development for asthma and identified two compounds - termed 11a and 12b - that mirror ES-62's protective effects. In this study, we have moved away from OVA, a model allergen, to test the SMAs against two clinically relevant allergens - house dust mite (HDM) and cockroach allergen (CR) extract. We show that both SMAs offer some protection against development of lung allergic responses to CR, in particular reducing eosinophil infiltration, whereas only SMA 12b is effective in protecting against eosinophil-dependent HDM-induced allergy. These data therefore suggest that helminth molecule-induced protection against model allergens may not necessarily translate to clinically relevant allergens. Nevertheless, in this study, we have managed to demonstrate that it is possible to produce synthetic drug-like molecules based on a parasitic worm product that show therapeutic potential with respect to asthma resulting from known triggers in humans.

Brugia malayi Antigen (BmA) Inhibits HIV-1 Trans-Infection but Neither BmA nor ES-62 Alter HIV-1 Infectivity of DC Induced CD4+ Th-Cells

One of the hallmarks of HIV-1 disease is the association of heightened CD4+ T-cell activation with HIV-1 replication. Parasitic helminths including filarial nematodes have evolved numerous and complex mechanisms to skew, dampen and evade human immune responses suggesting that HIV-1 infection may be modulated in co-infected individuals. Here we studied the effects of two filarial nematode products, adult worm antigen from Brugia malayi (BmA) and excretory-secretory product 62 (ES-62) from Acanthocheilonema viteae on HIV-1 infection in vitro. Neither BmA nor ES-62 influenced HIV-1 replication in CD4+ enriched T-cells, with either a CCR5- or CXCR4-using virus. BmA, but not ES-62, had the capacity to bind the C-type lectin dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) thereby inhibiting HIV-1 trans-infection of CD4+ enriched T-cells. As for their effect on DCs, neither BmA nor ES-62 could enhance or inhibit DC maturation as determined by CD83, CD86 and HLA-DR expression, or the production of IL-6, IL-10, IL-12 and TNF-α. As expected, due to the unaltered DC phenotype, no differences were found in CD4+ T helper (Th) cell phenotypes induced by DCs treated with either BmA or ES-62. Moreover, the HIV-1 susceptibility of the Th-cell populations induced by BmA or ES-62 exposed DCs was unaffected for both CCR5- and CXCR4-using HIV-1 viruses. In conclusion, although BmA has the potential capacity to interfere with HIV-1 transmission or initial viral dissemination through preventing the virus from interacting with DCs, no differences in the Th-cell polarizing capacity of DCs exposed to BmA or ES-62 were observed. Neither antigenic source demonstrated beneficial or detrimental effects on the HIV-1 susceptibility of CD4+ Th-cells induced by exposed DCs.

The parasitic worm-derived immunomodulator, ES-62 and its drug-like small molecule analogues exhibit therapeutic potential in a model of chronic asthma

Chronic asthma is associated with persistent lung inflammation and long-term remodelling of the airways that have proved refractory to conventional treatments such as steroids, despite their efficacy in controlling acute airway contraction and bronchial inflammation. As its recent dramatic increase in industrialised countries has not been mirrored in developing regions, it has been suggested that helminth infection may protect humans against developing asthma. Consistent with this, ES-62, an immunomodulator secreted by the parasitic worm Acanthocheilonema viteae, can prevent pathology associated with chronic asthma (cellular infiltration of the lungs, particularly neutrophils and mast cells, mucus hyper-production and airway thickening) in an experimental mouse model. Importantly, ES-62 can act even after airway remodelling has been established, arresting pathogenesis and ameliorating the inflammatory flares resulting from repeated exposure to allergen that are a debilitating feature of severe chronic asthma. Moreover, two chemical analogues of ES-62, 11a and 12b mimic its therapeutic actions in restoring levels of regulatory B cells and suppressing neutrophil and mast cell responses. These studies therefore provide a platform for developing ES-62-based drugs, with compounds 11a and 12b representing the first step in the development of a novel class of drugs to combat the hitherto intractable disorder of chronic asthma.

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.

Clinical trials of helminth therapy in autoimmune diseases: rationale and findings

Some helminths are major human pathogens. Recently, however, increased understanding of the immunoregulatory responses induced by this class of parasites, in combination with epidemiologic and animal studies, suggests that helminths may have therapeutic potential in autoimmune diseases (AD) and other conditions. This article reviews the rationale for and results of clinical trials to test the safety and efficacy of helminth therapy in AD. Also discussed are future prospects for investigation and the possibility that helminth treatment may serve as a probe to help reveal the pathogenesis of AD.

Looking beyond the induction of Th2 responses to explain immunomodulation by helminths

Although helminth infections are characteristically associated with Th2-mediated responses that include the production of the prototypical cytokines IL-4, IL-5 and IL-13 by CD4(+) cells, the production of IgE, peripheral blood eosinophilia and mucus production in localized sites, these responses are largely attenuated when helminth infections become less acute. This modulation of the immune response that occurs with chronic helminth infection is often induced by molecules secreted by helminth parasites, by non-Th2 regulatory CD4(+) cells, and by nonclassical B cells, macrophages and dendritic cells. This review will focus on those parasite- and host-mediated mechanisms underlying the modulated T-cell response that occurs as the default in chronic helminth infections.

Identifying the immunomodulatory components of helminths

Immunomodulatory components of helminths offer great promise as an entirely new class of biologics for the treatment of inflammatory diseases. Here, we discuss the emerging themes in helminth-driven immunomodulation in the context of therapeutic drug discovery. We broadly define the approaches that are currently applied by researchers to identify these helminth molecules, highlighting key areas of potential exploitation that have been mostly neglected thus far, notably small molecules. Finally, we propose that the investigation of immunomodulatory compounds will enable the translation of current and future research efforts into potential treatments for autoimmune and allergic diseases, while at the same time yielding new insights into the molecular interface of host-parasite biology.

Exosome-transported microRNAs of helminth origin: new tools for allergic and autoimmune diseases therapy?

Chronic diseases associated with inflammation show fast annual increase in their incidence. This has been associated with excessive hygiene habits that limit contacts between the immune system and helminth parasites. Helminthic infections induce regulation and expansion of regulatory T cells (Treg) leading to atypical Th2 type immune responses, with downregulation of the inflammatory component usually associated with these type of responses. Many cells, including those of the immune system, produce extracellular vesicles called exosomes which mediate either immune stimulation (DCs) or immune modulation (T cells). The transfer of miRNAs contained in T-cell exosomes has been shown to contribute to downregulate the production of inflammatory mediators. It has been recently described the delivery to the host-parasite interface of exosomes containing miRNAs by helminths and its internalization by host cells. In this sense, helminth microRNAs transported in exosomes and internalized by immune host cells exert an important role in the expansion of Treg cells, resulting in the control of inflammation. We here provide relevant information obtained in the field of exosomes, cell-cell communication and miRNAs, showing the high potential of helminth miRNAs delivered in exosomes to host cells as new therapeutic tools against diseases associated with exacerbated inflammatory responses.

Protective effect of small molecule analogues of the Acanthocheilonema viteae secreted product ES-62 on oxazolone-induced ear inflammation

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Small molecule analogues (SMAs) of the immunomodulator, ES-62, have been produced.

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Two SMAs protect against oxazolone-induced skin inflammation in mouse ears.

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Protection is associated with reduced cellular infiltration and collagen deposition.

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Protection is associated with decreased IFNγ mRNA in the ears.

ES-62 is the major secreted protein of the rodent filarial nematode Acanthocheilonema viteae. The molecule contains covalently attached phosphorylcholine (PC) residues, which confer anti-inflammatory properties on ES-62, underpinning the idea that drugs based on this active moiety may have therapeutic potential in human diseases associated with aberrant inflammation. Here we demonstrate that two synthetic small molecule analogues (SMAs) of ES-62 termed SMA 11a and SMA 12b are protective in the oxazolone-induced acute allergic contact dermatitis mouse model of skin inflammation, as measured by a significant reduction in ear inflammation following their administration before oxazolone sensitisation and before oxazolone challenge. Furthermore, it was found that when tested, 12b was effective at reducing ear swelling even when first administered before challenge. Histological analysis of the ears showed elevated cellular infiltration and collagen deposition in oxazolone-treated mice both of which were reduced by treatment with the two SMAs. Likewise, the oxazolone-induced increase in IFNγ mRNA in the ears was reduced but no effect on other cytokines investigated was observed. Finally, no influence on the mast cell populations in the ear was observed.

Suppression of OVA-alum induced allergy by Heligmosomoides polygyrus products is MyD88-, TRIF-, regulatory T- and B cell-independent, but is associated with reduced innate lymphoid cell activation

The murine intestinal nematode Heligmosomoides polygyrus exerts multiple immunomodulatory effects in the host, including the suppression of allergic inflammation in mice sensitized to allergen presented with alum adjuvant. Similar suppression is attained by co-administration of H. polygyrus excretory/secretory products (HES) with the sensitizing dose of ovalbumin (OVA) in alum. We investigated the mechanism of suppression by HES in this model, and found it was maintained in MyD88xTRIF-deficient mice, implying no role for helminth- or host-derived TLR ligands, or IL-1 family cytokines that signal in a MyD88- or TRIF-dependent manner. We also found suppression was unchanged in µMT mice, which lack B2 B cells, and that suppression was not abrogated when regulatory T cells were depleted in Foxp3.LuciDTR-4 mice. However, reduced IL-5 production was seen in the first 12 h after injection of OVA-alum when HES was co-administered, associated with reduced activation of IL-5(+) and IL-13(+) group 2 innate lymphoid cells. Thus, the suppressive effects of HES on alum-mediated OVA sensitization are reflected in the very earliest innate response to allergen exposure in vivo.

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.

The Differentiation of CD4(+) T-Helper Cell Subsets in the Context of Helminth Parasite Infection

Helminths are credited with being the major selective force driving the evolution of the so-called “type 2” immune responses in vertebrate animals, with their size and infection strategies presenting unique challenges to the immune system. Originally, type 2 immune responses were defined by the presence and activities of the CD4⁺ T-helper 2 subset producing the canonical cytokines IL-4, IL-5, and IL-13. This picture is now being challenged by the discovery of a more complex pattern of CD4⁺ T-helper cell subsets that appear during infection, including Tregs, Th17, Tfh, and more recently, Th22, Th9, and ThGM. In addition, a clearer view of the mechanisms by which helminths and their products selectively prime the CD4⁺ T-cell subsets is emerging. In this review, we have focused on recent data concerning the selective priming, differentiation, and functional role of CD4⁺ T-helper cell subsets in the context of helminth infection. We argue for a re-evaluation of the original Th2 paradigm and discuss how the observed plasticity of the T-helper subsets may enable the parasitized host to achieve an appropriate compromise between elimination, tissue repair, containment, and pathology.

Microorganism-induced suppression of allergic airway disease: novel therapies on the horizon?

Allergic airway disease is a major global health burden, and novel treatment options are urgently needed. Numerous epidemiological and experimental studies suggest that certain helminths and bacteria protect against respiratory allergies. These microorganisms are strong regulators of the immune system, and various potential regulatory mechanisms by which they protect against allergic airway inflammation have been proposed. Whereas early studies addressed the beneficial effect of natural infections, the focus now shifts toward identifying the dominant protective molecules and exploring their efficacy in models of allergic airway disease. In this article, we will review the evidence for microbe-mediated protection from allergic airway disease, the potential modes of action involved and discuss advances as well as limitations in the translation of this knowledge into novel treatment strategies against allergic airway disease.

Systemic impact of intestinal helminth infections

In this review, we examine the evidence that intestinal helminths can control harmful inflammatory responses and promote homeostasis by triggering systemic immune responses. Induction of separable components of immunity by helminths, which includes type 2 and immune regulatory responses, can both contribute toward the reduction in harmful type 1 immune responses that drive certain inflammatory diseases. Despite inducing type 2 responses, intestinal helminths may also downregulate harmful type 2 immune responses including allergic responses. We consider the possibility that intestinal helminth infection may indirectly affect inflammation by influencing the composition of the intestinal microbiome. Taken together, the studies reviewed herein suggest that intestinal helminth-induced responses have potent systemic effects on the immune system, raising the possibility that whole parasites or specific molecules produced by these metazoans may be an important resource for the development of future immunotherapies to control inflammatory diseases.

Small molecule analogues of the immunomodulatory parasitic helminth product ES-62 have anti-allergy properties

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Small molecule analogues of the helminth immunomodulator ES-62 have been produced.

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Two analogues inhibit mast cell functions and prevent airway hypersensitivity.

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The analogues are drug-like and could be considered for treatment of human allergy.

ES-62, a glycoprotein secreted by the filarial nematode Acanthocheilonema viteae, exhibits anti-inflammatory properties by virtue of covalently attached phosphorylcholine moieties. Screening of a library of ES-62 phosphorylcholine-based small molecule analogues (SMAs) revealed that two compounds, termed 11a and 12b, mirrored the helminth product both in inhibiting mast cell degranulation and cytokine responses in vitro and in preventing ovalbumin-induced Th2-associated airway inflammation and eosinophil infiltration of the lungs in mice. Furthermore, the two SMAs inhibited neutrophil infiltration of the lungs when administered therapeutically. ES-62-SMAs 11a and 12b thus represent starting points for novel drug development for allergies such as asthma.

Protection against collagen-induced arthritis in mice afforded by the parasitic worm product, ES-62, is associated with restoration of the levels of interleukin-10-producing B cells and reduced plasma cell infiltration of the joints

We have previously reported that ES-62, a molecule secreted by the parasitic filarial nematode Acanthocheilonema viteae, protects mice from developing collagen-induced arthritis (CIA). Together with increasing evidence that worm infection may protect against autoimmune conditions, this raises the possibility that ES-62 may have therapeutic potential in rheumatoid arthritis and hence, it is important to fully understand its mechanism of action. To this end, we have established to date that ES-62 protection in CIA is associated with suppressed T helper type 1 (Th1)/Th17 responses, reduced collagen-specific IgG2a antibodies and increased interleukin-10 (IL-10) production by splenocytes. IL-10-producing regulatory B cells have been proposed to suppress pathogenic Th1/Th17 responses in CIA: interestingly therefore, although the levels of IL-10-producing B cells were decreased in the spleens of mice with CIA, ES-62 was found to restore these to the levels found in naive mice. In addition, exposure to ES-62 decreased effector B-cell, particularly plasma cell, infiltration of the joints, and such infiltrating B cells showed dramatically reduced levels of Toll-like receptor 4 and the activation markers, CD80 and CD86. Collectively, this induction of hyporesponsiveness of effector B-cell responses, in the context of the resetting of the levels of IL-10-producing B cells, is suggestive of a modulation of the balance between effector and regulatory B-cell responses that may contribute to ES-62-mediated suppression of CIA-associated inflammation and inhibition of production of pathogenic collagen-specific IgG2a antibodies.

Secretory products of helminth parasites as immunomodulators

Parasitic helminths release molecules into their environment, which are generally referred to as excretory-secretory products or ES. ES derived from a wide range of nematodes, trematodes and cestodes have been studied during the past 30-40 years, their characterization evolving from simple biochemical procedures such as SDS-PAGE in the early days to sophisticated proteomics in the 21st century. Study has incorporated investigation of ES structure, potential as vaccines, immunodiagnostic utility, functional activities and immunomodulatory properties. Immunomodulation by ES is increasingly the area of most intensive research with a number of defined helminth products extensively analyzed with respect to the nature of their selective effects on cells of the immune system as well as the molecular mechanisms, which underlie these immunomodulatory effects. As a consequence, we are now beginning to learn the identities of the receptors that ES employ and are increasingly acquiring detailed knowledge of the signalling pathways that they interact with and subvert. Such information is contributing to the growing idea that the anti-inflammatory properties of a number of ES products makes them suitable starting points for the development of novel drugs for treating human inflammatory disease.

ES-62, a therapeutic anti-inflammatory agent evolved by the filarial nematode Acanthocheilonema viteae

Filarial nematodes cause long-term infections in hundreds of millions of people. A significant proportion of those affected develop a number of debilitating health problems but, remarkably, such infections are often unnoticed for many years. It is well known that parasitic worms modulate, yet do not completely inhibit, host immunological pathways, promoting their survival by limiting effective immune mechanisms. Such immunoregulation largely depends on molecules released by the worms, termed excretory-secretory products (ES). One of these products is the molecule ES-62, which is actively secreted by the rodent filarial nematode Acanthocheilonema viteae. ES-62 has been shown to exert anti-inflammatory actions thorough its phosphorylcholine (PC)-containing moiety on a variety of cells of the immune system, affecting intracellular signalling pathways associated with antigen receptor- and TLR-dependent responses. We summarise here how ES-62 modulates key signal transduction elements and how such immunomodulation confers protection to mice subjected to certain experimental models of inflammatory disease. Finally, we discuss recent results showing that it is possible to synthetise small molecule analogues (SMAs) that mimic the anti-inflammatory properties of ES-62, opening an exciting new drug development field in translational medicine.

Glycoconjugates in host-helminth interactions

Helminths are multicellular parasitic worms that comprise a major class of human pathogens and cause an immense amount of suffering worldwide. Helminths possess an abundance of complex and unique glycoconjugates that interact with both the innate and adaptive arms of immunity in definitive and intermediate hosts. These glycoconjugates represent a major untapped reservoir of immunomodulatory compounds, which have the potential to treat autoimmune and inflammatory disorders, and antigenic glycans, which could be exploited as vaccines and diagnostics. This review will survey current knowledge of the interactions between helminth glycans and host immunity and highlight the gaps in our understanding which are relevant to advancing therapeutics, vaccine development, and diagnostics.