Helminths: Immunoregulation and Inflammatory Diseases-Which Side Are Trichinella spp. and Toxocara spp. on?

Trichinella spiralis alleviates LPS-induced acute lung injury by modulating the protective Th2 immune response

Sepsis is a disorder of immune regulation caused by pathogenic microorganisms. A large number of inflammatory factors and inflammatory mediators are released, resulting in systemic inflammatory response disorder and acute lung injury (ALI). Helminths infection activate Th2 cytokines and immunomodulatory pathways, which have the function of anti-infection effector molecules. The early infection of Trichinella spiralis (T. spiralis) was mainly intestinal phase. In this study, we explored the effect of intestinal phase infection of T. spiralis on LPS-induced ALI. Compared with control mice, the serum and lung tissues of T. spiralis infected mice had a significant decrease of Th1 inflammatory cytokines, a significant increase of Th2 anti-inflammatory cytokines, and a significant decrease of inflammatory cell infiltration in lung tissue. These results suggest that T. spiralis during the intestinal phase can act on distal organs (lung) and reduce LPS-induced lung inflammation, providing evidence for a potential new pathway for immune-mediated disease in helminths and a possible role for intestinal worms in the gut-lung axis.

Interleukin 17 producing T cell responses in human chronic trichinellosis-insight from a case study

INTRODUCTION

We studied the cellular immune response in a patient infected since 10 months (along with other 51 people) during a trichinellosis outbreak caused by Trichinella spp.

METHODS

A 46 years old female resulted serologically positive for trichinellosis. We isolated peripheral blood mononuclear cells (PBMCs) and incubated them with excretory/secretory antigens (ESA) of Trichinella spiralis (T1) or Trichinella pseudospiralis (T4) to produce antigen specific T cell lines and clones, analysed for the phenotype (T helper or cytotoxic cells), for their T4 or T1 antigens specificity and for their cytokine profile (IFNγ, IL-17A, IL-4) by flow cytometry, thymidine incorporation assay and ELISpot.

RESULTS

The test performed using ESA from T1 or T4 has identified the species responsible for infection as T. pseudospiralis since the proliferative responses (evaluated by CFSE, Carboxyfluorescein succinimidyl ester, FACS analysis) was higher for T4 (72,8%) than T1 (23.6 %) antigen. The cell lines produced significant levels of IFNγ, IL-4 and IL-17A after stimulation. From the T cell line obtained in response to T1 ESA, as regards CD4 + cells, 12 % Th2, 22.8 % Th1, 6.6 % Th17, 6 % Th0, 2.2 % Th1/Th17 and 0.7 % Th2/Th17, were obtained. From the T1-specific TCL we generated 15 clones. From the TCL specific for T4 ESA, as regards CD4+, 15.2 % Th2, 27.1 % Th1, 3 % Th17, 10.3 %Th0, 1.9 % Th1/Th17 and 1 % Th2/ Th17 were obtained. From such TCL 4 clones were isolated, 1Th2, 1 Th1, 1 Th17, 1 Th1/Th17 and no Th0 nor Th2/Th17.

CONCLUSIONS

By cellular immunology techniques the species responsible of the infection resulted T. pseudospiralis, confirming the results previously obtained by serology. For the first time it was revealed in a human chronic infection the presence of Th17 cells.

Helminth-derived molecules: pathogenic and pharmacopeial roles

Parasitic helminths, taxonomically comprising trematodes, cestodes, and nematodes, are multicellular invertebrates widely disseminated in nature and have afflicted people continuously for a long time. Helminths play potent roles in the host through generating a variety of novel molecules, including some excretory/secretory products and others that are involved in intracellular material exchange and information transfer as well as the initiation or stimulation of immune and metabolic activation. The helminth-derived molecules have developed powerful and diverse immunosuppressive effects to achieve immune evasion for parasite survival and establish chronic infections. However, they also improve autoimmune and allergic inflammatory responses and promote metabolic homeostasis by promoting metabolic reprogramming of various immune functions, and then inducing alternatively activated macrophages, T helper 2 cells, and regulatory T cells-mediated immune responses. Therefore, a deeper exploration of the immunopathogenic mechanism and immune regulatory mechanisms of helminth-derived molecules exerted in the host is crucial for understanding host-helminth interactions as well as the development of therapeutic drugs for infectious or non-infectious diseases. In this review, we focus on the properties of helminth-derived molecules to give an overview of the most recent scientific knowledge about their pathogenic and pharmacopeial roles in immune-metabolic homeostasis.

Probiotics: an alternative anti-parasite therapy

This paper review about probiotic effects and mechanism of action against the gut and non-gut helminths and protozoan parasites. Gastrointestinal parasitic infections are considered a serious health problem and are widely distributed globally. The disease process which emanates from this parasite infection provides some of the many public and veterinary health problems in the tropical and sub-tropical countries. Prevention and control of the parasite disease is through antihelmintic and anti-protozoan drugs, but, due to the increasing emergence of such drug resistance, eradication of parasite infestation in human and livestock still lingers a challenge, which requires the development of new alternative strategies. The use of beneficial microorganisms i.e. probiotics is becoming interesting due to their prophylactic application against several diseases including parasite infections. Recent studies on the interactions between probiotics, parasites and host immune cells using animal models and in vitro culture systems has increased considerably and draw much attention, yet the mechanisms of actions mediating the positive effects of these beneficial microorganisms on the hosts remain unexplored. Therefore, the aim of the present review is to summarize the latest findings on the probiotic research against the gut and non-gut parasites of significance.

NLRP3 Plays a Key Role in Antihelminth Immunity in the Enteral and Parenteral Stages of Trichinella spiralis-Infected Mice

Trichinellosis is an important foodborne zoonosis, and no effective treatments are yet available. Nod-like receptor (NLR) plays a critical role in the host response against nematodes. Therefore, we aimed to explore the role of the NLRP3 inflammasome (NLRP3) during the adult, migrating, and encysted stages of Trichinella spiralis infection. The mice were treated with the specific NLRP3 inhibitor MCC950 after inoculation with T. spiralis. Then, the role that NLRP3 plays during T. spiralis infection of mice was evaluated using enzyme-linked immunosorbent assay (ELISA), Western blotting, flow cytometry, histopathological evaluation, bone marrow-derived macrophage (BMDM) stimulation, and immunofluorescence. The in vivo results showed that NLRP3 enhanced the Th1 immune response in the adult and migrating stages and weakened the Th2 immune response in the encysted stage. NLRP3 promoted the release of proinflammatory factors (interferon gamma [IFN-γ]) and suppressed the release of anti-inflammatory factors (interleukin 4 [IL-4]). Pathological changes were also improved in the absence of NLRP3 in mice during T. spiralis infection. Importantly, a significant reduction in adult worm burden and muscle larvae burden at 7 and 35 days postinfection was observed in mice treated with the specific NLRP3 inhibitor MCC950. In vitro, we first demonstrated that NLRP3 in macrophages can be activated by T. spiralis proteins and promotes IL-1β and IL-18 release. This study revealed that NLRP3 is involved in the host response to T. spiralis infection and that targeted inhibition of NLRP3 enhanced the Th2 response and accelerated T. spiralis expulsion. These findings may help in the development of protocols for controlling trichinellosis.

Potential roles of Toxocara canis larval excretory secretory molecules in immunomodulation and immune evasion

Toxocara canis larvae invade various tissues of different vertebrate species without developing into adults in paratenic host. The long-term survival of the larvae despite exposure to the well-armed immune response is a notable achievement. The larvae modulate the immune response to help the survival of both the host and the larvae. They skew the immune response to type 2/regulatory phenotype. The outstanding ability of the larvae to modulate the host immune response and to evade the immune arms is attributed to the secretion of Toxocara excretory-secretory products (TESPs). TESPs are complex mixture of differing molecules. The present review deals with the molecular composition of the TESPs, their interaction with the host molecules, their effect on the innate immune response, the receptor recognition, the downstream signals the adaptive immunity and the repair of tissues. This review also addresses the role of TESPs molecules in the immune evasion strategy and the potential effect of the induced immunomodulation in some diseases. Identification of parasite components that influence the nematode-host interactions could enhance understanding the molecular basis of nematode pathogenicity. Furthermore, the identification of helminths molecules with immunomodulatory potential could be used in immunotherapies for some diseases.

The helminth holobiont: a multidimensional host-parasite-microbiota interaction

Gastrointestinal helminths have developed multiple mechanisms by which they manipulate the host microbiome to make a favorable environment for their long-term survival. While the impact of helminth infections on vertebrate host immunity and its gut microbiota is relatively well studied, little is known about the structure and functioning of microbial populations supported by metazoan parasites. Here we argue that an integrated understanding of the helminth-associated microbiome and its role in the host disease pathogenesis may facilitate the discovery of specific microbial and/or genetic patterns critical for parasite biology and subsequently pave the way for the development of alternative control strategies against parasites and parasitic disease.

Long lasting immunity in trichinellosis - insight from a small study group

Trichinellosis in humans is most often caused by the parasite Trichinella spiralis. The clinical course of the disease is diverse and the symptoms can vary from mild to severe. Symptoms usually disappear within a few months, but encysted larvae in the muscles can cause myalgia and weakness that last for years. However, the existence of chronic trichinellosis as a disease is still debatable. This study presents the results obtained at the National Reference Laboratory for Trichinellosis - INEP, Serbia. The study was conducted to assess the immunoserological, biochemical and symptomatic disease parameters of twelve patients who acquired trichinellosis 13 and 18 years ago, respectively. They were involved in two T. spiralis outbreaks in Serbia, at the village of Kumane and the city of Belgrade (nine and three patients, respectively). Results indicated the presence of specific anti-Trichinella antibodies in 83% of the total number of patients. However, while the humoral immune response to Trichinella lasted for more than a decade reaching almost two decades after the acute infection phase (7/9 and 3/3 respectively, in two outbreaks), persistence of chronic muscular pain, as the most prolonged symptom of trichinellosis, could be found in the majority of patients from the Kumane outbreak (7/9). As a consequence, these patients suffered from limitations in daily living activities for the same period of time. The results presented in this paper are our contribution to the view that trichinellosis as a chronic disease with symptoms exists and may be related to the severity of the disease in the acute phase.

Harnessing immunomodulatory mechanisms of Trichinella spiralis to design novel nanomedical approaches for restoring self-tolerance in autoimmunity

The rapid increase in the prevalence of autoimmune diseases in recent decades, especially in developed countries, coincided with improved living conditions and healthcare. Part of this increase could be ascribed to the lack of exposure to infectious agents like helminths that co-evolved with us and display potent immune regulatory actions. In this review we discussed many investigations, including our own, showing that Trichinella spiralis via its excretory-secretory products attenuate Th1/Th17 immunopathological response in autoimmunity and potentiate the protective Th2 and or regulatory T cell response, acting as an effective induction of tolerogenic dendritic cells (DCs), and probably mimicking the autoantigen in some diseases. A recent discovery of T. spiralis extracellular vesicles (TsEVs) suggested that inducing a complex regulation of the immune response requires simultaneous delivery of different signals in nano-sized packages. Indeed, different artificial nanomedical approaches discussed here suggested that co-delivery of multiple signals via nanoparticles is the most promising strategy for the treatment of autoimmune diseases. Although a long way is ahead of us before we could completely replicate natural nano-delivery systems which are both safe and potent in restoring self-tolerance, a clear path is being opened from a careful examination of parasite-host interactions.

Detrimental role of IL-33/ST2 pathway sustaining a chronic eosinophil-dependent Th2 inflammatory response, tissue damage and parasite burden during Toxocara canis infection in mice

Toxocariasis is a neglected disease that affects people around the world. Humans become infected by accidental ingestion of eggs containing Toxocara canis infective larvae, which upon reaching the intestine, hatch, penetrate the mucosa and migrate to various tissues such as liver, lungs and brain. Studies have indicated that Th2 response is the main immune defense mechanism against toxocariasis, however, there are still few studies related to this response, mainly the IL-33/ST2 pathway. Some studies have reported an increase in IL-33 during helminth infections, including T. canis. By binding to its ST2 receptor, IL-33 stimulating the Th2 polarized immune cell and cytokine responses. Thus, we aimed to investigate the role of the IL-33/ST2 pathway in the context of T. canis larval migration and the immunological and pathophysiological aspects of the infection in the liver, lungs and brain from Wild-Type (WT) BALB/c background and genetically deficient mice for the ST2 receptor (ST2^-/-). The most important findings revealed that the IL-33/ST2 pathway is involved in eosinophilia, hepatic and cerebral parasitic burden, and induces the formation of granulomas related to tissue damage and pulmonary dysfunction. However, ST2^-/- mice, the immune response was skewed to Th1/Th17 type than Th2, that enhanced the control of parasite burden related to IgG2a levels, tissue macrophages infiltration and reduced lung dysfunction. Collectively, our results demonstrate that the Th2 immune response triggered by IL-33/ST2 pathway mediates susceptibility to T. canis, related to parasitic burden, eosinophilia and granuloma formation in which consequently contributes to tissue inflammation and injury.

Toxocariasis is a neglected disease caused by Toxocara canis, which has 19% worldwide seroprevalence, and is associated with socioeconomic, geographic and environmental factors. Humans become infected by accidental ingestion of T. canis eggs present in contaminated food, water or soil. After ingestion, the larvae hatch in the intestine and can reach various tissues such as liver, lung and brain. Helminth infections usually trigger a Th2 immune response in the host, by releasing cytokines such as IL-4, IL-5, IL-13 and IL-33. IL-33 is an alarmin that binds to the ST2 receptor, and some studies have observed an increase in this cytokine in toxocariasis, however there are no studies regarding the IL-33/ST2 role in this infection. Thus, we evaluated the influence of this pathway by analyzing immunological and pathophysiological aspects in T. canis-infected mice. Our results demonstrated that the IL-33/ST2 pathway is related to parasite burden on the liver and brain and also increases the number of eosinophils in the blood and tissues. In addition, it involved with the pulmonary immune response and granulomas with impact in lung function. In conclusion, the IL-33/ST2 pathway governs the host susceptibility to T. canis in mice.

Toxocara canis and Toxocara cati Somatic and Excretory-Secretory Antigens Are Recognised by C-Type Lectin Receptors

Toxocara canis and Toxocara cati, the worldwide occurring intestinal roundworms of canids and felids, represent an important public health threat due to various disease manifestations in humans. Host recognition of pathogens is mediated by pattern recognition receptors (PRRs). Myeloid C-type lectin receptors (CLRs) are PRRs and recognise carbohydrate structures of various pathogens. As Toxocara excretory-secretory products (TES) are predominantly composed of glycoconjugates, they represent suitable targets for CLRs. However, the range of host-derived CLRs recognising Toxocara spp. is still unknown. Using a CLR-hFc fusion protein library, T. canis and T. cati L3 somatic antigens (TSOM) were bound by a variety of CLRs in enzyme-linked immunosorbent assay (ELISA), while their TES products interacted with macrophage galactose-type lectin-1 (MGL-1). Two prominent candidate CLRs, MGL-1 and macrophage C-type lectin (MCL), were selected for further binding studies. Immunofluorescence microscopy revealed binding of MGL-1 to the oral aperture of L3. Immunoblot experiments identified distinct protein fractions representing potential ligands for MGL-1 and MCL. To evaluate how these interactions influence the host immune response, bone marrow-derived dendritic cell (BMDC) assays were performed, showing MCL-dependent T. cati-mediated cytokine production. In conclusion, MGL-1 and MCL are promising candidates for immune modulation during Toxocara infection, deserving further investigation in the future.

Toxocara Awareness Among Medical Practitioners in Saudi Arabia

Human toxocariasis is a zoonotic infection with global and regional impacts. Worldwide it is underestimated and clinically overlooked. Medical practitioners are generally unaware of the extent of the resulting disease spectrum. The objective of the study was to assess knowledge and disease awareness among medical practitioners in Aseer, south-western Saudi Arabia. A questionnaire addressing knowledge about the parasite, its visceral larva migrans and the disease spectrum generated was used to interview participants. The study included 285 participants. In answer to the question what is toxocara, only 27%, answered correctly that it is a nematode, paediatricians being the majority. With regard to years of experience among participants, 56.8% of those who answered correctly had less than 5-year experience, as opposed to 35.4% for those with more than 10-year experience. The cumulative awareness about the disease manifestations and spectrum, i.e. those who knew, was less than 30% across specialties and years of experiences. Lack of awareness regarding Toxocara infection and the disease spectrum it can generate is evident. The consequence for such lack of knowledge within our practising medical community is simply unacceptable as it might translate into misdiagnosis and consequently misguided treatment.

Trichinella spiralis: inflammation modulator

The hygiene hypothesis posits that the decreased incidence of parasitic infection in developed countries may underlie an increased prevalence of allergic and autoimmune diseases in these countries. As unique inflammation modulator of intracellular parasitism, Trichinella spiralis, or its excretory-secretory (ES) product, shows improved responses to allergies, autoimmune diseases, inflammatory bowel disease, type 1 diabetes, rheumatic arthritis and autoimmune encephalomyelitis by exerting immunomodulatory effects on both innate and adaptive immune cells in animal models. Research has shown that T. spiralis differs from other helminths in manipulation of the host immune response not only by well-known characteristics of its life cycle, but also by its inflammation modulation pathway. How the parasite achieves inflammation modulation has not been fully elucidated yet. This review will generalize the mechanism and focuses on ES immunomodulatory molecules of T. spiralis that may be important for developing new therapeutics for inflammatory disorders.

Interactions between helminths and tuberculosis infections: Implications for tuberculosis diagnosis and vaccination in Africa

Africa is the second most populous continent and has perennial health challenges. Of the estimated 181 million school aged children in sub-Saharan Africa (SSA), nearly half suffer from ascariasis, trichuriasis, or a combination of these infections. Coupled with these is the problem of tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) infection, which is a leading cause of death in the region. Compared to the effect of the human immunodeficiency virus on the development of TB, the effect of chronic helminth infections is a neglected area of research, yet helminth infections are as ubiquitous as they are varied and may potentially have profound effects upon host immunity, particularly as it relates to TB infection, diagnosis, and vaccination. Protection against active TB is known to require a clearly delineated T-helper type 1 (Th1) response, while helminths induce a strong opposing Th2 and immune-regulatory host response. This Review highlights the potential challenges of helminth-TB co-infection in Africa and the need for further research.

Infection with Toxocara canis Inhibits the Production of IgE Antibodies to α-Gal in Humans: Towards a Conceptual Framework of the Hygiene Hypothesis?

α-Gal syndrome (AGS) is a type of anaphylactic reaction to mammalian meat characterized by an immunoglobulin (Ig)E immune response to the oligosaccharide α-Gal (Galα1-3Galβ1-4GlcNAc-R). Tick bites seems to be a prerequisite for the onset of the allergic disease in humans, but the implication of non-tick parasites in α-Gal sensitization has also been deliberated. In the present study, we therefore evaluated the capacity of helminths (Toxocara canis, Ascaris suum, Schistosoma mansoni), protozoa (Toxoplasma gondii), and parasitic fungi (Aspergillus fumigatus) to induce an immune response to α-Gal. For this, different developmental stages of the infectious agents were tested for the presence of α-Gal. Next, the potential correlation between immune responses to α-Gal and the parasite infections was investigated by testing sera collected from patients with AGS and those infected with the parasites. Our results showed that S. mansoni and A. fumigatus produce the terminal α-Gal moieties, but they were not able to induce the production of specific antibodies. By contrast, T. canis, A. suum and T. gondii lack the α-Gal epitope. Furthermore, the patients with T. canis infection had significantly decreased anti-α-Gal IgE levels when compared to the healthy controls, suggesting the potential role of this nematode parasite in suppressing the allergic response to the glycan molecule. This rather intriguing observation is discussed in the context of the 'hygiene hypothesis'. Taken together, our study provides new insights into the relationships between immune responses to α-Gal and parasitic infections. However, further investigations should be undertaken to identify T. canis components with potent immunomodulatory properties and to assess their potential to be used in immunotherapy and control of AGS.

Human Toxocara Infection: Allergy and Immune Responses

BACKGROUND

Toxocariasis is a cosmopolitan infection that occurs in various regions worldwide, more frequently in developing countries. Chronic infections with Toxocara species in humans are associated with the production of high levels of specific and non-specific antibodies of all isotypes and IgG subclasses and a cytokine response characterized by the production of Th2 cytokines including IL-4, IL-5 and IL-13 by Peripheral Blood Monocytes (PBMCs) and Leukocytes (PBLs) in whole blood cultures. Other Th2 effector responses are also prominent during infection, reflected by elevated numbers of peripheral blood eosinophils and increased expression of eosinophil degranulation products. The production of IFN-γ by PBMCs/PBLs stimulated with Toxocara-secreted proteins is not prominent in toxocariasis but IL-10 production may be increased in infected individuals. The relationship between Toxocara species with allergic reactions was reported in the recent century. Experimental and epidemiological investigations revealed that toxocariasis with this parasite led to the development of allergic symptoms, such as asthma. However, the findings are conflicting since in other investigations no association between these two immunopathologies has been reported.

CONCLUSION

The present review endeavours to summarize the data on Toxocara species and findings from studies on the relationship of toxocariasis with symptoms and signs of allergy. Furthermore, the mechanisms of immune responses and the factors associated between allergy and Toxocara infection are discussed.

A Dual Role for Macrophages in Modulating Lung Tissue Damage/Repair during L2 Toxocara canis Infection

Macrophages that are classically activated (M1) through the IFN-γ/STAT1 signaling pathway have a major role in mediating inflammation during microbial and parasitic infections. In some cases, unregulated inflammation induces tissue damage. In helminth infections, alternatively activated macrophages (M2), whose activation occurs mainly via the IL-4/STAT6 pathway, have a major role in mediating protection against excessive inflammation, and has been associated with both tissue repair and parasite clearance. During the lung migratory stage of Toxocara canis, the roles of M1 and M2 macrophages in tissue repair remain unknown. To assess this, we orally infected wild-type (WT) and STAT1 and STAT6-deficient mice (STAT1^-/- and STAT6^-/-) with L2 T. canis, and evaluated the role of M1 or M2 macrophages in lung pathology. The absence of STAT1 favored an M2 activation pattern with Arg1, FIZZ1, and Ym1 expression, which resulted in parasite resistance and lung tissue repair. In contrast, the absence of STAT6 induced M1 activation and iNOS expression, which helped control parasitic infection but generated increased inflammation and lung pathology. Next, macrophages were depleted by intratracheally inoculating mice with clodronate-loaded liposomes. We found a significant reduction in alveolar macrophages that was associated with higher lung pathology in both WT and STAT1^-/- mice; in contrast, STAT6^-/- mice receiving clodronate-liposomes displayed less tissue damage, indicating critical roles of both macrophage phenotypes in lung pathology and tissue repair. Therefore, a proper balance between inflammatory and anti-inflammatory responses during T. canis infection is necessary to limit lung pathology and favor lung healing.

Probiotics for the Control of Helminth Zoonosis

This paper is a comprehensive, concise, and an up to date review about probiotics effect and mechanisms against helminth infections of zoonotic importance. Zoonoses are diseases that can be transmitted from animals to humans in a reversible way. Despite zoonotic helminth diseases being still a challenge to the public health and the agriculture industries globally, they were still neglected in both human and veterinary medicine. Moreover, the increasing emergence of anthelmintic drug resistance constitutes failures of most disease control strategies, alarming for a quest to new alternative control approaches. Consequently, the use of beneficial microorganisms, probiotics, is becoming interesting for its prophylactic or therapeutic application against several diseases including helminths. Recent studies on probiotics against parasites and the interactions between bacteria, parasites, and the immune system in the gut draw much attention. However, the effects of these beneficial microorganisms in helminth infections remain largely unexplored. Therefore, the aim of the present review is to raise attention and to summarize recent findings on probiotics research against helminth parasites of zoonotic significance. State-of-the-art research on beneficial effects of bacteria on helminth infections and their proposed mechanisms of action is thoroughly discussed.

Effect of probiotic bacteria on phagocytosis and respiratory burst activity of blood polymorphonuclear leukocytes (PMNL) in mice infected with Trichinella spiralis

This study focusses on the effect of probiotic (bacteriocinogenic) strains on parasite infection and innate immunity - phagocytosis and oxidative burst of blood monocytes and polymorphonuclear leukocytes (PMNL) in mice infected with Trichinella spiralis. Bacteriocinogenic and probiotic strains of different origin (Enterococcus faecium AL41=CCM8558, Enterococcus durans ED26E/7, Lactobacillus fermentum AD1=CCM7421, Lactobacillus plantarum 17L/1) were administered daily in dose of 10⁹CFU/ml in 100μl and mice were infected with 400 larvae of T. spiralis on 7th day of treatment. Phagocytic activity of blood leukocytes was inhibited at week 3 and 4 post infection (p.i.), i.e. in the time of massive muscle invasion with larvae T. spiralis. Administration of bacterial strains to mice prior to T. spiralis infection elevated and prolonged phagocytic activity of blood leukocytes and their ingestion capability from week 1 to 3 of the infection and the phagocytosis was inhibited only at week 4 p.i. The highest stimulative effect on phagocytosis was induced by strains E. durans ED26E/7, L. fermentum AD1=CCM7421, and L. plantarum 17L/1. The percentage of cells with respiratory burst and their enzymatic activity was increased after T. spiralis infection with the exception of week 3 p.i. In contrast, in all mice treated with bacterial strains the enzymatic stimulation was observed after the infection, with the highest intensity caused by strains E. durans ED26E/7, L. fermentum AD1=CCM7421 and L. plantarum 17L/1. The administration of probiotic strains stimulated phagocytosis and respiratory burst of blood PMNL that could contribute to a decreased larval migration and a destruction of muscle larvae and then reduced parasite burden in the host. The protective effect against T. spiralis infection was induced by all strains, but the highest reduction was recorded by E. faecium AL41=CCM8558.

Environmental contamination with Toxocara eggs: a quantitative approach to estimate the relative contributions of dogs, cats and foxes, and to assess the efficacy of advised interventions in dogs

Background

Environmental contamination with Toxocara eggs is considered the main source of human toxocariasis. The contribution of different groups of hosts to this contamination is largely unknown. Current deworming advices focus mainly on dogs. However, controversy exists about blind deworming regimens for >6-month-old dogs, as most of them do not actually shed Toxocara eggs. We aim to estimate the contribution of different non-juvenile hosts to the environmental Toxocara egg contamination and to assess the effects of different Toxocara-reducing interventions for dogs.

Methods

A stochastic model was developed to quantify the relative contribution to the environmental contamination with Toxocara eggs of household dogs, household cats, stray cats, and foxes, all older than 6 months in areas with varying urbanization degrees. The model was built upon an existing model developed by Morgan et al. (2013). We used both original and published data on host density, prevalence and intensity of infection, coprophagic behaviour, faeces disposal by owners, and cats’ outdoor access. Scenario analyses were performed to assess the expected reduction in dogs’ egg output according to different deworming regimens and faeces clean-up compliances. Estimates referred to the Netherlands, a country free of stray dogs.

Results

Household dogs accounted for 39 % of the overall egg output of >6-month-old hosts in the Netherlands, followed by stray cats (27 %), household cats (19 %), and foxes (15 %). In urban areas, egg output was dominated by stray cats (81 %). Intervention scenarios revealed that only with a high compliance (90 %) to the four times a year deworming advice, dogs’ contribution would drop from 39 to 28 %. Alternatively, when 50 % of owners would always remove their dogs’ faeces, dogs’ contribution would drop to 20 %.

Conclusion

Among final hosts of Toxocara older than 6 months, dogs are the main contributors to the environmental egg contamination, though cats in total (i.e. both owned and stray) transcend this contribution. A higher than expected compliance to deworming advice is necessary to reduce dogs’ egg output meaningfully. Actions focusing solely on household dogs and cats are unlikely to sufficiently reduce environmental contamination with eggs, as stray cats and foxes are also important contributors.

Secretory Products of Trichinella spiralis Muscle Larvae and Immunomodulation: Implication for Autoimmune Diseases, Allergies, and Malignancies

Trichinella spiralis has the unique ability to make itself "at home" by creating and hiding in a new type of cell in the host body that is the nurse cell. From this immunologically privileged place, the parasite orchestrates a long-lasting molecular cross talk with the host through muscle larvae excretory-secretory products (ES L1). Those products can successfully modulate parasite-specific immune responses as well as responses to unrelated antigens (either self or nonself in origin), providing an anti-inflammatory milieu and maintaining homeostasis. It is clear, based on the findings from animal model studies, that T. spiralis and its products induce an immunomodulatory network (which encompasses Th2- and Treg-type responses) that may allow the host to deal with various hyperimmune-associated disorders as well as tumor growth, although the latter still remains unclear. This review focuses on studies of the molecules released by T. spiralis, their interaction with pattern recognition receptors on antigen presenting cells, and subsequently provoked responses. This paper also addresses the immunomodulatory properties of ES L1 molecules and how the induced immunomodulation influences the course of different experimental inflammatory and malignant diseases.

The parasitic worm product ES-62 targets myeloid differentiation factor 88-dependent effector mechanisms to suppress antinuclear antibody production and proteinuria in MRL/lpr mice

Objective

The hygiene hypothesis suggests that parasitic helminths (worms) protect against the development of autoimmune disease via a serendipitous side effect of worm-derived immunomodulators that concomitantly promote parasite survival and limit host pathology. The aim of this study was to investigate whether ES-62, a phosphorylcholine-containing glycoprotein secreted by the filarial nematode Acanthocheilonema viteae, protects against kidney damage in an MRL/lpr mouse model of systemic lupus erythematosus (SLE).

Methods

MRL/lpr mice progressively produce high levels of autoantibodies, and the resultant deposition of immune complexes drives kidney pathology. The effects of ES-62 on disease progression were assessed by measurement of proteinuria, assessment of kidney histology, determination of antinuclear antibody (ANA) production and cytokine levels, and flow cytometric analysis of relevant cellular populations.

Results

ES-62 restored the disrupted balance between effector and regulatory B cells in MRL/lpr mice by inhibiting plasmablast differentiation, with a consequent reduction in ANA production and deposition of immune complexes and C3a in the kidneys. Moreover, by reducing interleukin-22 production, ES-62 may desensitize downstream effector mechanisms in the pathogenesis of kidney disease. Highlighting the therapeutic importance of resetting B cell responses, adoptive transfer of purified splenic B cells from ES-62–treated MRL/lpr mice mimicked the protection afforded by the helminth product. Mechanistically, this reflects down-regulation of myeloid differentiation factor 88 expression by B cells and also kidney cells, resulting in inhibition of pathogenic cross-talk among Toll-like receptor–, C3a-, and immune complex–mediated effector mechanisms.

Conclusion

This study provides the first demonstration of protection against kidney pathology by a parasitic worm–derived immunomodulator in a model of SLE and suggests therapeutic potential for drugs based on the mechanism of action of ES-62.

Allergy and worms: let's bring back old friends?

PURPOSE OF REVIEW

In order to survive in their host, parasitic worms (helminths) have evolved cunning strategies to manipulate the host immune system, some of which may lead to protection from immune dysregulatory diseases such as allergy. Thus, loss of exposure to helminths due to a highly hygienic life style might have contributed to the fact that living in an industrialized country is being associated with an increased prevalence of allergic diseases. However, it must be pointed out that certain helminth infections can in fact induce an allergic phenotype. Factors such as different parasite species, timing of infection in relation to allergic sensitization, or duration and intensity of infection may influence the association between helminth infections and the development or clinical course of allergic disease. In the present article, we review studies that have explored the interaction between helminth infections and allergy in epidemiological and experimental studies. Furthermore, the possibility of using helminths or helminth-derived molecules for the treatment of allergic diseases is discussed with a focus on evidence from clinical trials.

RECENT FINDINGS

During the past 10 years, many exciting and important studies have found that certain helminth infections protect against the development of allergic diseases. Not surprisingly, several clinical trials investigated the effects of deliberate exposure to parasites like porcine whipworm (Trichuris suis) or hookworm (Necator americanus) to develop "helminth therapies". Although they proved to be a safe option to control aberrant inflammation, the final goal is to identify the parasite-derived immunnomodulatory molecules responsible for protective effects.

Recurrent wheezing is associated with intestinal protozoan infections in Warao Amerindian children in Venezuela: a cross-sectional survey

Background

While in developed countries the prevalence of allergic diseases is rising, inflammatory diseases are relatively uncommon in rural developing areas. High prevalence rates of helminth and protozoan infections are commonly found in children living in rural settings and several studies suggest an inverse association between helminth infections and allergies. No studies investigating the relationship between parasitic infections and atopic diseases in rural children of developing countries under the age of 2 years have been published so far. We performed a cross-sectional survey to investigate the association of helminth and protozoan infections and malnutrition with recurrent wheezing and atopic eczema in Warao Amerindian children in Venezuela.

Methods

From August to November 2012, 229 children aged 0 to 2 years residing in the Orinoco Delta in Venezuela were enrolled. Data were collected through standardized questionnaires and physical examination, including inspection of the skin and anthropometric measurements. A stool sample was requested from all participants and detection of different parasites was performed using microscopy and real time polymerase chain reaction (PCR).

Results

We observed high prevalence rates of atopic eczema and recurrent wheezing, respectively 19% and 23%. The prevalence of helminth infections was 26% and the prevalence of protozoan infections was 59%. Atopic eczema and recurrent wheezing were more frequently observed in stunted compared with non-stunted children in multivariable analysis (OR 4.3, 95% CI 1.3 – 13.6, p = 0.015 and OR 4.5, 95% CI 0.97 – 21.2, p = 0.055). Furthermore, recurrent wheezing was significantly more often observed in children with protozoan infections than in children without protozoan infections (OR 6.7, 95% CI 1.5 – 30.5).

Conclusions

High prevalence rates of atopic eczema and recurrent wheezing in Warao Amerindian children under 2 years of age were related to stunting and intestinal protozoan infections respectively. Helminth infections were not significantly associated with either atopic eczema or recurrent wheezing.

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.

Chronic Opisthorchis felineus infection attenuates atherosclerosis--an autopsy study

Previously, we proposed a hypothesis that chronic helminthic infection may have beneficial effects on the development of atherosclerosis. The aim of this study was to investigate an association between Opisthorchis felineus chronic helminthic infections with aortic atherosclerosis and serum total cholesterol. A series of medico-legal autopsy specimens collected in Khanty-Mansiisk (the region in Russia endemic for O. felineus) were studied to assess O. felineus worm burden in cadaver livers. The areas of atherosclerotic lesions in the cadaver aortas were measured by visual planimetry. A family history of cardiovascular disease, smoking, hypertension or diabetes was elicited, and serum total cholesterol levels examined. Three hundred and nineteen cadavers (280 (87.8%) males and 39 (12.2%) females) aged 20-72 years were divided into five age groups: (i) 20-29, (ii) 30-39, (iii) 40-49, (iv) 50-59 and (v) >60 years old. The O. felineus mean worm burden was 257±312 worms/liver. Infected subjects were categorised into three subgroups depending on the worm burden: mild (<100 worms), moderate (100-500 worms) and severe (>500 worms). Infected subjects had lower serum total cholesterol (mild worm burden, 186.4±25.6 mg/dl; moderate worm burden, 183.4±23.1mg/dl, P=0.002; severe worm burden, 170.6±25.1mg/dl, P<0.001) than non-infected subjects (201.1±21.2 mg/dl). The average percentage of aortic surface covered by fatty streaks, fibrotic plaques and complicated lesions was negatively related to worm burden in the infected subjects. Chronic helminthic infections was a negative predictor of aortic atherosclerosis; with an odds ratio of 1.72 (1.02-2.91), P=0.041 for all subjects; and 3.19 (1.35-7.58), P=0.008 for subjects aged >40 years old. Opisthorchis felineus chronic helminthic infectionswas found to be associated with lower serum total cholesterol levels and a significant attenuation of atherosclerosis.

Current drug targets for helminthic diseases

More than 2 billion people are infected with helminth parasites across the globe. The burgeoning drug resistance against current anthelmintics in parasitic worms of humans and livestock requires urgent attention to tackle these recalcitrant worms. This review focuses on the advancements made in the area of helminth drug target discovery especially from the last few couple of decades. It highlights various approaches made in this field and enlists the potential drug targets currently being pursued to target economically important helminth species both from human as well as livestock to combat disease pathology of schistosomiasis, onchocerciasis, lymphatic filariasis, and other important macroparasitic diseases. Research in the helminths study is trending to identify potential and druggable targets through genomic, proteomic, biochemical, biophysical, in vitro experiments, and in vivo experiments in animal models. The availability of major helminths genome sequences and the subsequent availability of genome-scale functional datasets through in silico search and prioritization are expected to guide the experimental work necessary for target-based drug discovery. Organized and documented list of drug targets from various helminths of economic importance have been systematically covered in this review for further exploring their use and applications, which can give physicians and veterinarians effective drugs in hand to enable them control worm infections.