Diplomatic Assistance: Can Helminth-Modulated Macrophages Act as Treatment for Inflammatory Disease?

Type I Cystatin Derived from Cysticercus pisiformis-Stefins, Suppresses LPS-Mediated Inflammatory Response in RAW264.7 Cells

Cysticercus pisiformis is a kind of tapeworm larvae of Taenia pisiformis, which parasitizes the liver envelope, omentum, mesentery, and rectum of rodents such as rabbits. Cysteine protease inhibitors derived from helminth were immunoregulatory molecules of intermediate hosts and had an immunomodulatory function that regulates the production of inflammatory factors. Thus, in the present research, the recombinant Stefin of C. pisiformis was confirmed to have the potential to fight inflammation in LPS-Mediated RAW264.7 murine macrophages. CCK8 test showed that rCpStefin below 50 μg/mL concentration did not affect cellular viability. Moreover, the NO production level determined by the Griess test was decreased. In addition, the secretion levels of IL-1β, IL-6, and TNF-α as measured by ELISA were decreased. Furthermore, it exerted anti-inflammatory activity by decreasing the production of proinflammatory cytokines and proinflammatory mediators, including IL-1β, IL-6, TNF-α, iNOS, and COX-2 at the gene transcription level, as measured by qRT-PCR. Therefore, Type I cystatin derived from C. pisiformis suppresses the LPS-Mediated inflammatory response of the intermediate host and is a potential candidate for the treatment of inflammatory diseases.

Association between helminth infection and allergic disorders among children in Batu, Ethiopia

BACKGROUND

Helminths are potent immunomodulators and in their chronic infection state they may protect against allergy-related disease and atopy. However, they are also known for inducing allergic conditions. This study aimed to assess the association between helminths,  atopy and allergic conditions.

METHODS

A total of 461 school children participated in this cross-sectional study. Data on allergic symptoms and a range of confounding variables was gathered from parents via an interviewer-led questionnaire. Skin sensitization to house dust mite and cockroaches was analyzed, and a stool sample was collected for helminth analysis. Serum total Immunoglobulin E using enzyme-linked immunosorbent assay and eosinophil count were also measured.

RESULTS

Overall sensitivity to both allergens was 2.4%. Self-reported allergic outcomes in the last 12 months for the 461 participants had been : wheezing 3.7%, asthma 2.2%, eczema 13.2% and hay fever 6.9%. Overall, the prevalence of helminth infection was 11.9% (53/444). A borderline significant association was found between atopy and any allergy symptoms (odds ratio [OR]: 3.32, 95% confidence interval [95% CI: 0.99, 11.1], p = .052). There was no significant association between helminths and atopy (OR: 0.64 [95% CI: 0.29, 1.41], p = .268) and also between helminths and allergic symptoms (OR: 0.64 [95% CI: 0.29, 1.41], p = .268). Bivariate analysis showed keeping an animal in the house increases the risk of atopy while maternal and paternal history of allergy increases the risk of developing allergic symptoms in the children.

CONCLUSION AND CLINICAL RELEVANCE

This study found a non-significant inverse association between helminths infection and atopy and allergic disorders, likely due to reduced statistical power, resulting in a lower prevalence of atopy and allergic conditions. A high powered longtitudinal study is necessary to explore the casuality and potential therapeutic benefits of helminths for allergic disorders.

Therapeutic effect of Echinococcus granulosus cyst fluid on bacterial sepsis in mice

BACKGROUND

The primary pathophysiological process of sepsis is to stimulate a massive release of inflammatory mediators to trigger systemic inflammatory response syndrome (SIRS), the major cause of multi-organ dysfunction and death. Like other helminths, Echinococcus granulosus induces host immunomodulation. We sought to determine whether E. granulosus cyst fluid (EgCF) displays a therapeutic effect on sepsis-induced inflammation and tissue damage in a mouse model.

METHODS

The anti-inflammatory effects of EgCF were determined by in vitro culture with bone marrow-derived macrophages (BMDMs) and in vivo treatment of BALB/C mice with cecal ligation and puncture (CLP)-induced sepsis. The macrophage phenotypes were determined by flow cytometry, and the levels of cytokines in cell supernatants or in sera of mice were measured (ELISA). The therapeutic effect of EgCF on sepsis was evaluated by observing the survival rates of mice for 72 h after CLP, and the pathological injury to the liver, kidney, and lung was measured under a microscope. The expression of TLR-2/MyD88 in tissues was measured by western blot to determine whether TLR-2/MyD88 is involved in the sepsis-induced inflammatory signaling pathway.

RESULTS

In vitro culture with BMDMs showed that EgCF promoted macrophage polarization to M2 type and inhibited lipopolysaccharide (LPS)-induced M1 macrophages. EgCF treatment provided significant therapeutic effects on CLP-induced sepsis in mice, with increased survival rates and alleviation of tissue injury. The EgCF conferred therapeutic efficacy was associated with upregulated anti-inflammatory cytokines (IL-10 and TGF-β) and reduced pro-inflammatory cytokines (TNF-α and INF-γ). Treatment with EgCF induced Arg-1-expressed M2, and inhibited iNOS-expressed M1 macrophages. The expression of TLR-2 and MyD88 in EgCF-treated mice was reduced.

CONCLUSIONS

The results demonstrated that EgCF confers a therapeutic effect on sepsis by inhibiting the production of pro-inflammatory cytokines and inducing regulatory cytokines. The anti-inflammatory effect of EgCF is carried out possibly through inducing macrophage polarization from pro-inflammatory M1 to regulatory M2 phenotype to reduce excessive inflammation of sepsis and subsequent multi-organ damage. The role of EgCF in regulating macrophage polarization may be achieved by inhibiting the TLR2/MyD88 signaling pathway.

Immunomodulatory effects of chronic trichinellosis on Toxoplasma gondii RH virulent strain in experimental rats

Mixed parasitic infections could affect the host immunological responses and re-design the pathogenesis of each other. The impact of Toxoplasma gondii (T. gondii) and Trichinella spiralis (T. spiralis) co-infection on the immune response remains unclear. The objective of the present study was to investigate the possible effect of chronic trichinellosis on the immune response of rats infected with T. gondii virulent RH strain. Animals were divided into four groups: group I: non-infected negative control; group II: infected with T. spiralis; group III: infected with T. gondii and group IV: infected with T. spiralis then infected with T. gondii 35 days post T. spiralis infection (co-infected group). The interaction between T. spiralis and T. gondii was evaluated by histopathological examination of liver and brain tissues, immunohistochemical expression of inducible nitric oxide synthase (iNOS), and β-catenin in the brain tissues, and CD4+ and CD8+ T cells percentages, and tumor necrosis factor (TNF)-alpha expression in the spleen tissues. Along with, splenic interleukin (IL)-4 and IL-10 mRNA expression levels were measured 15 days post-Toxoplasma infection. Our study revealed that prior infection with T. spiralis leads to attenuation of Th1 response against T. gondii, including iNOS, TNF-α, and CD8+ T-cell response with improvement of the histopathological changes in the tissues. In conclusion, in the co-infected rats, a balanced immune response has been developed with the end result, improvement of the histopathological changes in the liver and brain.

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.

Host Immune Response to Clinical Hypervirulent Klebsiella pneumoniae Pulmonary Infections via Transcriptome Analysis

Klebsiella pneumoniae (K. pneumoniae), especially those with hypervirulence, is becoming a global concern and posing great threat to human health. Studies on individual immune cells or cytokines have partially revealed the function of the host immune defense against K. pneumoniae pulmonary infection. However, systematic immune response against K. pneumoniae has not been fully elucidated. Herein, we report a transcriptome analysis of the lungs from a mouse pneumonia model infected with a newly isolated K. pneumoniae clinical strain YBQ. Total RNA was isolated from the lungs of mice 48 hours post infection to assess transcriptional alteration of genes. Transcriptome data were analyzed with KEGG, GO, and ICEPOP. Results indicated that upregulated transcription level of numerous cytokines and chemokines was coordinated with remarkably activated ribosome and several critical immune signaling pathways, including IL-17 and TNF signaling pathways. Notably, transcription of cysteine cathepsin inhibitor (stfa1, stfa2, and stfa3) and potential cysteine-type endopeptidase inhibitor (cstdc4, cstdc5, and cstdc6) were upregulated. Results of ICEPOP showed neutrophils functions as the most essential cell type against K. pneumoniae infection. Critical gene alterations were further validated by rt-PCR. Our findings provided a global transcriptional perspective on the mechanisms of host defense against K. pneumoniae infection and revealed some unique responding genes.

Trichinella spiralis cystatin alleviates polymicrobial sepsis through activating regulatory macrophages

BACKGROUND

Sepsis is a life-threateningorgandysfunction caused by the cytokine storm induced by the severe bacterial infection. Excessive inflammatory responses are responsible for the lethal organ damage during the early stage of sepsis. Helminth infection and helminth-derived proteins have been identified to have the ability to immunomodulate the host immune system by reducing inflammation against inflammatory diseases. Trichinella spiralis cystatin (Ts-Cys) is a cysteine protease inhibitor with strong immunomodulatory functions on host immune system. Our previous studies have shown that excretory-secretory proteins of T. spiralis reduced sepsis-induced inflammation and Ts-Cys was able to inhibit macrophages to produce inflammatory cytokines. Whether Ts-Cys has a therapeutic effect on polymicrobial sepsis and related immunological mechanism are not yet known.

METHODS

Sepsis was induced in BALB/c mice using cecal ligation and puncture (CLP), followed by intraperitoneal injection of 15 µg recombinant Ts-Cys (rTs-Cys). The therapeutic effect of rTs-Cys on sepsis was evaluated by observing the 72-hour survival rates of CLP-induced septic mice and the acute injury of lung and kidney through measuring the wet/dry weight ratio of lung, the levels of blood urea nitrogen (BUN) and creatinine (Cr) in sera and the tissue section pathology. The potential underlying mechanism was investigated using mouse bone marrow-derived macrophages (BMDMs) by observing the effect of rTs-Cys on LPS-stimulated macrophage polarization. The expression of genes associated with macrophage polarization in BMDMs and tissues of septic mice was measured by Western Blotting and qPCR.

RESULTS

In this study, we demonstrated the treatment with rTs-Cys alleviated CLP-induced sepsis in mice with significantly reduced pathological injury in vital organs of lung and kidney and reduced mortality of septic mice. The further study identified that treatment with rTs-Cys promoted macrophage polarization from classically activated macrophage (M1) to alternatively activated macrophage (M2) phenotype via inhibiting TLR2/MyD88 signal pathway and increasing expression of mannose receptor (MR), inhibited pro-inflammatory cytokines (TNF-α, IL-6 and IL-1β) and increased regulatory anti-inflammatory cytokines (IL-10 and TGF-β) in sera and tissues (lung and kidney) of mice with polymicrobial sepsis.

CONCLUSIONS

Our results demonstrated that rTs-Cys had a therapeutic effect on sepsis through activating regulatory macrophages possibly via suppressing TLR2/MyD88 signal pathway. We also identified that rTs-Cys-induced M2 macrophage differentiation was associated with increased expression of MR on the surface of macrophages. Our results underscored the importance of MR in regulating macrophages during the treatment with rTs-Cys, providing another immunological mechanism in which helminths and their derived proteins modulate the host immune system. The findings in this study suggest that rTs-Cys is a potential therapeutic agent for the prevention and treatment of sepsis and other inflammatory diseases.

Bone erosion in inflammatory arthritis is attenuated by Trichinella spiralis through inhibiting M1 monocyte/macrophage polarization

Helminths and helminth-derived products hold promise for treating joint bone erosion in rheumatoid arthritis (RA). However, the mechanisms of helminths ameliorating the osteoclastic bone destruction are incompletely understood. Here, we report that Trichinella spiralis infection or treatment with the excreted/secreted products of T. spiralis muscle larvae (MES) attenuated bone erosion and osteoclastogenesis in mice with collage-induced arthritis (CIA) through inhibiting M1 monocyte/macrophage polarization and the production of M1-related proinflammatory cytokines. In vitro, MES inhibited LPS-induced M1 macrophage activation while promoting IL-4-induced M2 macrophage polarization. Same effects of MES were also observed in monocytes derived from RA patients, wherein MES treatment suppressed LPS-induced M1 cytokine production. Moreover, MES treatment attenuated LPS and RANKL co-stimulated osteoclast differentiation from the RAW264.7 macrophages through inhibiting activation of the NF-κB rather than MAPK pathway. This study provides insight into the M1 subset as a potential target for helminths to alleviate osteoclastic bone destruction in RA.

Parasite worm antigens instruct macrophages to release immunoregulatory extracellular vesicles

Emerging evidence suggests that immune cells not only communicate with each other through cytokines, chemokines, and cell surface receptors, but also by releasing small membranous structures known as extracellular vesicles (EVs). EVs carry a variety of different molecules that can be taken up by recipient cells. Parasitic worms are well known for their immunomodulatory properties, but whether they can affect immune responses by altering EV-driven communication between host immune cells remains unclear. Here we provide evidence that stimulation of bone marrow-derived macrophages (BMDMs) with soluble products of Trichuris suis (TSPs), leads to the release of EVs with anti-inflammatory properties. Specifically, we found that EVs from TSP-pulsed BMDMs, but not those from unstimulated BMDMs can suppress TNFα and IL-6 release in LPS-stimulated BMDMs and BMDCs. However, no polarization toward M1 or M2 was observed in macrophages exposed to EVs. Moreover, EVs enhanced reactive oxygen species (ROS) production in the exposed BMDMs, which was associated with a deregulated redox homeostasis as revealed by pathway analysis of transcriptomic data. Proteomic analysis identified cytochrome p450 (CYP450) as a potential source of ROS in EVs from TSP-pulsed BMDMs. Finally, pharmacological inhibition of CYP450 activity could suppress ROS production in those BMDMs. In summary, we find that TSPs can modulate immune responses not only via direct interactions but also indirectly by eliciting the release of EVs from BMDMs that exert anti-inflammatory effects on recipient cells.

Nrf2 Participates in M2 Polarization by Trichinella spiralis to Alleviate TNBS-Induced Colitis in Mice

Trichinella spiralis induced alternative activated macrophages (M2), leading to protect against Crohn's disease, known as Th1 -related inflammation, which enhances oxidative stress in the host. However, the relationship of oxidative stress and T. spiralis -mediated immune response is still unknown. In our study, we showed that nuclear factor erythroid 2-related factor-2 (Nrf2), a key transcription factor in antioxidant, participated in M2 polarization induced by T. spiralis muscle larval excretory/secretory (ES) products in vitro. ES -treated M2 were injected intravenously after TNBS challenge and we demonstrated that ES-M could alleviate the severity of the colitis in mice. Adoptive transfer of ES -treated M2 decreased the level of IFN-γ and increased the levels of IL-4 and IL-10 in vivo. However, the capacity of ES -treated Nrf2 KO macrophages to treat colitis was dramatically impaired. ES -treated Nrf2 KO macrophages was insufficient to result in the elevated levels of IL-4 and IL-10. These findings indicate that Nrf2 was required for M2 polarization induced by T. spiralis ES to alleviate colitis in mice.

Fasciola hepatica hijacks host macrophage miRNA machinery to modulate early innate immune responses

Fasciola hepatica, a global worm parasite of humans and their livestock, regulates host innate immune responses within hours of infection. Host macrophages, essential to the first-line defence mechanisms, are quickly restricted in their ability to initiate a classic protective pro-inflammatory immune response. We found that macrophages from infected animals are enriched with parasite-derived micro(mi)RNAs. The most abundant of these miRNAs, fhe-miR-125b, is released by the parasite via exosomes and is homologous to a mammalian miRNA, hsa-miR-125b, that is known to regulate the activation of pro-inflammatory M1 macrophages. We show that the parasite fhe-miR-125b loads onto the mammalian Argonaut protein (Ago-2) within macrophages during infection and, therefore, propose that it mimics host miR-125b to negatively regulate the production of inflammatory cytokines. The hijacking of the miRNA machinery controlling innate cell function could be a fundamental mechanism by which worm parasites disarm the early immune responses of their host to ensure successful infection.

Excretory/Secretory Products From Trichinella spiralis Adult Worms Attenuated DSS-Induced Colitis in Mice by Driving PD-1-Mediated M2 Macrophage Polarization

Helminth-modulated macrophages contribute to attenuating inflammation in inflammatory bowel diseases. The programmed death 1 (PD-1) plays an important role in macrophage polarization and is essential in the maintenance of immune system homeostasis. Here, we investigate the role of PD-1-mediated polarization of M2 macrophages and the protective effects of excretory/secretory products from Trichinella spiralis adult worms (AES) on DSS-induced colitis in mice. Colitis in mice was induced by oral administration of dextran sodium sulfate (DSS) daily. Mice with DSS-induced colitis were treated with T. spiralis AES intraperitoneally, and pathological manifestations were evaluated. Macrophages in mice were depleted with liposomal clodronate. Markers for M1-type (iNOS, TNF-α) and M2-type (CD206, Arg-1) macrophages were detected by qRT-PCR and flow cytometry. Macrophage expression of PD-1 was quantified by flow cytometry; RAW 264.7 cells and peritoneal macrophages were used for in vitro tests, and PD-1 gene knockout mice were used for in vivo investigation of the role of PD-1 in AES-induced M2 macrophage polarization. Macrophage depletion was found to reduce DSS-induced colitis in mice. Treatment with T. spiralis AES significantly increased macrophage expression of CD206 and Arg-1 and simultaneously attenuated colitis severity. We found T. spiralis AES to enhance M2 macrophage polarization; these findings were confirmed studying in vitro cultures of RAW264.7 cells and peritoneal macrophages from mice. Further experimentation revealed that AES upregulated PD-1 expression, primarily on M2 macrophages expressing CD206. The AES-induced M2 polarization was found to be decreased in PD-1 deficient macrophages, and the therapeutic effects of AES on colitis was reduced in PD-1 knockout mice. In conclusion, the protective effects of T. spiralis AES on DSS-induced colitis were found to associate with PD-1 upregulation and M2 macrophage polarization. Thus, PD-1-mediated M2 macrophage polarization is a key mechanism of helminth-induced modulation of the host immune system.

Adoptive transfer of Trichinella spiralis-activated macrophages can ameliorate both Th1- and Th2-activated inflammation in murine models

Trichinella spiralis is a zoonotic nematode and food borne parasite and infection with T. spiralis leads to suppression of the host immune response and other immunopathologies. Alternative activated macrophages (M2) as well as T_reg cells, a target for immunomodulation by the helminth parasite, play a critical role in initiating and modulating the host immune response to parasite. The precise mechanism by which helminths modulate host immune response is not fully understood. To determine the functions of parasite-induced M2 macrophages, we compared the effects of M1 and M2 macrophages obtained from Trichinella spiralis-infected mice with those of T. spiralis excretory/secretory (ES) protein-treated macrophages on experimental intestinal inflammation and allergic airway inflammation. T. spiralis infection induced M2 macrophage polarization by increasing the expression of CD206, ARG1, and Fizz2. In a single application, we introduced macrophages obtained from T. spiralis-infected mice and T. spiralis ES protein-treated macrophages into mice tail veins before the induction of dextran sulfate sodium (DSS)-induced colitis, ovalbumin (OVA)-alum sensitization, and OVA challenge. Colitis severity was assessed by determining the severity of colitis symptoms, colon length, histopathologic parameters, and Th1-related inflammatory cytokine levels. Compared with the DSS-colitis group, T. spiralis-infected mice and T. spiralis ES protein-treated macrophages showed significantly lower disease activity index (DAI) at sacrifice and smaller reductions of body weight and proinflammatory cytokine level. The severity of allergic airway inflammation was assessed by determining the severity of symptoms of inflammation, airway hyperresponsiveness (AHR), differential cell counts, histopathologic parameters, and levels of Th2-related inflammatory cytokines. Severe allergic airway inflammation was induced after OVA-alum sensitization and OVA challenge, which significantly increased Th2-related cytokine levels, eosinophil infiltration, and goblet cell hyperplasia in the lung. However, these severe allergic symptoms were significantly decreased in T. spiralis-infected mice and T. spiralis ES protein-treated macrophages. Helminth infection and helminth ES proteins induce M2 macrophages. Adoptive transfer of macrophages obtained from helminth-infected mice and helminth ES protein-activated macrophages is an effective treatment for preventing and treating airway allergy in mice and is promising as a therapeutic for treating inflammatory diseases.

Immunoproteomics and Surfaceomics of the Adult Tapeworm Hymenolepis diminuta

In cestodiasis, mechanical and molecular contact between the parasite and the host activates the immune response of the host and may result in inflammatory processes, leading to ulceration and intestinal dysfunctions. The aim of the present study was to identify antigenic proteins of the adult cestode Hymenolepis diminuta by subjecting the total protein extracts from adult tapeworms to 2DE immunoblotting (two-dimensional electrophoresis combined with immunoblotting) using sera collected from experimentally infected rats. A total of 36 protein spots cross-reacting with the rat sera were identified using LC-MS/MS. As a result, 68 proteins, including certain structural muscle proteins (actin, myosin, and paramyosin) and moonlighters (heat shock proteins, kinases, phosphatases, and glycolytic enzymes) were identified; most of these were predicted to possess binding and/or catalytic activity required in various metabolic and cellular processes, and reported here as potential antigens of the adult cestode for the first time. As several of these antigens can also be found at the cell surface, the surface-associated proteins were extracted and subjected to in-solution digestion for LC-MS/MS identification (surfaceomics). As a result, a total of 76 proteins were identified, from which 31 proteins, based on 2DE immunoblotting, were predicted to be immunogenic. These included structural proteins actin, myosin and tubulin as well as certain moonlighting proteins (heat-shock chaperones) while enzymes with diverse catalytic activities were found as the most dominating group of proteins. In conclusion, the present study shed new light into the complexity of the enteric cestodiasis by showing that the H. diminuta somatic proteins exposed to the host possess immunomodulatory functions, and that the immune response of the host could be stimulated by diverse mechanisms, involving also those triggering protein export via yet unknown pathways.

The Untapped Pharmacopeic Potential of Helminths

The dramatic rise in immunological disorders that occurs with socioeconomic development is associated with alterations in microbial colonization and reduced exposure to helminths. Excretory-secretory (E/S) helminth products contain a mixture of proteins and low-molecular-weight molecules representing the primary interface between parasite and host. Research has shown great pharmacopeic potential for helminth-derived products in animal disease models and even in clinical trials. Although in its infancy, the translation of worm-derived products into therapeutics is highly promising. Here, we focus on important key aspects in the development of immunomodulatory drugs, also highlighting novel approaches that hold great promise for future development of innovative research strategies.

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

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

Global issues in allergy and immunology: Parasitic infections and allergy

Allergic diseases are on the increase globally in parallel with a decrease in parasitic infection. The inverse association between parasitic infections and allergy at an ecological level suggests a causal association. Studies in human subjects have generated a large knowledge base on the complexity of the interrelationship between parasitic infection and allergy. There is evidence for causal links, but the data from animal models are the most compelling: despite the strong type 2 immune responses they induce, helminth infections can suppress allergy through regulatory pathways. Conversely, many helminths can cause allergic-type inflammation, including symptoms of "classical" allergic disease. From an evolutionary perspective, subjects with an effective immune response against helminths can be more susceptible to allergy. This narrative review aims to inform readers of the most relevant up-to-date evidence on the relationship between parasites and allergy. Experiments in animal models have demonstrated the potential benefits of helminth infection or administration of helminth-derived molecules on chronic inflammatory diseases, but thus far, clinical trials in human subjects have not demonstrated unequivocal clinical benefits. Nevertheless, there is sufficiently strong evidence to support continued investigation of the potential benefits of helminth-derived therapies for the prevention or treatment of allergic and other inflammatory diseases.

Opening a Can of Worms: Leprosy Reactions and Complicit Soil-Transmitted Helminths

Background

> 94% of new annual leprosy cases are diagnosed in populations co-endemic for soil-transmitted helminths (STH). STH can profoundly dysregulate host immune responses towards Th2 bias, which can be restored over time after deworming. We hypothesize that STH co-infection is associated with leprosy reaction (denoted as simply “reaction” herein) occurrence within a co-endemic population.

Methods

A cohort study was performed on a cohort of Nepalese leprosy patients across treatment and diagnostic classifications who were screened by routine fecal smear microscopy and multiplex quantitative PCR (qPCR) for Ascaris lumbricoides (Al), Strongyloides stercoralis (Ss), Ancyclostoma duodenale (Ad) and Necator americanus (Na).

Results

Among 145 patients, 55% were positive for ≥ 1 STH (STH +): 34% Al +, 18% Ss +, 17% Ad + and 5% Na +. Significant inverse STH and reaction relationships were evidenced by the bulk of cases: 63% reaction-negative were STH + of total cases (p = 0.030) while 65% reaction-positive were STH − in new cases (96; p = 0.023). Strikingly, the majority of STH + were reaction-negative, even when considering each species: 59% Al +, 60% Ss +, 62% Ad + and 67% Na + of new leprosy cases.

Conclusions

Absence of STH co-infection is associated with leprosy reaction at diagnosis within a co-endemic population. This is likely due to immune reconstitution effects after deworming or interruption of chronic STH-mediated immune dysregulation.

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Fecal screening by qPCR revealed that 55% of 145 leprosy patients hosted 1 or more soil-transmitted helminth (STH) co-infections

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STH coinfection was significantly and inversely associated with leprosy reaction

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Chronic STH-induced immune bias followed by disruption of co-infection, potentially by deworming, may initiate immune reconstitution that can lead to reaction development

Toxoplasma Co-infection Prevents Th2 Differentiation and Leads to a Helminth-Specific Th1 Response

Nematode infections, in particular gastrointestinal nematodes, are widespread and co-infections with other parasites and pathogens are frequently encountered in humans and animals. To decipher the immunological effects of a widespread protozoan infection on the anti-helminth immune response we studied a co-infection with the enteric nematode Heligmosomoides polygyrus in mice previously infected with Toxoplasma gondii. Protective immune responses against nematodes are dependent on parasite-specific Th2 responses associated with IL-4, IL-5, IL-13, IgE, and IgG1 antibodies. In contrast, Toxoplasma gondii infection elicits a strong and protective Th1 immune response characterized by IFN-γ, IL-12, and IgG2a antibodies. Co-infected animals displayed significantly higher worm fecundity although worm burden remained unchanged. In line with this, the Th2 response to H. polygyrus in co-infected animals showed a profound reduction of IL-4, IL-5, IL-13, and GATA-3 expressing T cells. Co-infection also resulted in the lack of eosinophilia and reduced expression of the Th2 effector molecule RELM-β in intestinal tissue. In contrast, the Th1 response to the protozoan parasite was not diminished and parasitemia of T. gondii was unaffected by concurrent helminth infection. Importantly, H. polygyrus specific restimulation of splenocytes revealed H. polygyrus-reactive CD4⁺ T cells that produce a significant amount of IFN-γ in co-infected animals. This was not observed in animals infected with the nematode alone. Increased levels of H. polygyrus-specific IgG2a antibodies in co-infected mice mirrored this finding. This study suggests that polarization rather than priming of naive CD4⁺ T cells is disturbed in mice previously infected with T. gondii. In conclusion, a previous T. gondii infection limits a helminth-specific Th2 immune response while promoting a shift toward a Th1-type immune response.

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.

Can Parasitic Worms Cure the Modern World's Ills?

There has been increasing recognition that the alarming surge in allergy and autoimmunity in the industrialised and developing worlds shadows the rapid eradication of pathogens, such as parasitic helminths. Appreciation of this has fuelled an explosion in research investigating the therapeutic potential of these worms. This review considers the current state-of-play with a particular focus on exciting recent advances in the identification of potential novel targets for immunomodulation that can be exploited therapeutically. Furthermore, we contemplate the prospects for designing worm-derived immunotherapies for an ever-widening range of inflammatory diseases, including, for example, obesity, cardiovascular disease, and ageing as well as neurodevelopmental disorders like autism.

Helminth Immunomodulation in Autoimmune Disease

Helminths have evolved to become experts at subverting immune surveillance. Through potent and persistent immune tempering, helminths can remain undetected in human tissues for decades. Redirecting the immunomodulating "talents" of helminths to treat inflammatory human diseases is receiving intensive interest. Here, we review therapies using live parasitic worms, worm secretions, and worm-derived synthetic molecules to treat autoimmune disease. We review helminth therapy in both mouse models and clinical trials and discuss what is known on mechanisms of action. We also highlight current progress in characterizing promising new immunomodulatory molecules found in excretory/secretory products of helminths and their potential use as immunotherapies for acute and chronic inflammatory diseases.

Chronic infections with viruses or parasites: breaking bad to make good

Eukaryotic forms of life have been continually invaded by microbes and larger multicellular parasites, such as helminths. Over a billion years ago bacterial endosymbionts permanently colonized eukaryotic cells leading to recognized organelles with a distinct genetic lineage, such as mitochondria and chloroplasts. Colonization of our skin and mucosal surfaces with bacterial commensals is now known to be important for host health. However, the contribution of chronic virus and parasitic infections to immune homeostasis is being increasingly questioned. Persistent infection does not necessarily equate to exhibiting a chronic illness: healthy hosts (e.g. humans) have chronic viral and parasitic infections with no evidence of disease. Indeed, there are now examples of complex interactions between these microbes and hosts that seem to confer an advantage to the host at a particular time, suggesting that the relationship has progressed along an axis from parasitic to commensal to one of a mutualistic symbiosis. This concept is explored using examples from viruses and parasites, considering how the relationships may be not only detrimental but also beneficial to the human host.

Intestinal helminth infection induces highly functional resident memory CD4+ T cells in mice

Immunity to intestinal nematodes requires CD4⁺ Th2-cell responses, including IL-4 and IL-13 production. Chronic infection with intestinal nematodes leads to downregulation of these responses, and few functional T helper (Th) 2 cells are detected in secondary lymphoid organs in the chronic phase or after abrogation of infection. Here, we show with a natural murine infection with Heligmosomoides polygyrus that highly functional memory Th2 cells persist in the lamina propria and in addition in the peritoneal cavity (PC) after abrogation of infection. While both tissue-resident memory (T_RM ) populations proliferate in situ and express IL-4, IL-5, and IL-13 upon TCR-dependent stimulation, only peritoneal memory cells express high levels of the IL-33 receptor and produce IL-5 and IL-13 upon TCR-independent stimulation with IL-33 and IL-7. Most importantly, PC-derived T_RM cells are able to mediate anti-helminthic effects by decreasing the fecundity of female worms upon transfer into recipient mice. These results show that nonlymphoid compartments can serve as reservoirs for Th2 memory cells, and furthermore that innate effector function of Th2 memory cells is restricted to CD4⁺ memory T cells residing in the PC.

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.