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Background: Anthelminthic treatment options against schistosomiasis are limited. The current treatment relies almost exclusively on a single drug, praziquantel (PZQ). As a consequence, the development of resistance to PZQ and limited activity of PZQ against earlier development stages are respectively a risk and a limitation to achieving the goals of the new WHO roadmap towards elimination. For the discovery of new chemical starting points, the in vitro drug screening on Schistosoma mansoni (S. mansoni) against newly transformed schistosomula (NTS) is still the most predominant approach. The use of only NTS in the initial screening limits sensitivity to potential new compounds which are predominantly active in later developmental stages. Using our recently described highly standardized, straightforward and reliable culture method that generates high rates of juvenile worms, we aimed to repurpose a subset of the National Center for Advancing Translational Sciences (NCATS) Pharmaceutical Collection (340 compounds) to identify new hits with an in vitro worm culture assay., Methodology/principal Findings: Cercariae were mechanically transformed into skin-stage (SkS) schistosomula and continuously cultured for 3-6 weeks to the liver stage (LiS). A commercial source of serum was identified, and decrease of NTS/well along with optimal drug testing conditions was established to test compounds on early and late LiS worms. The library was screened in 96-well format assays using praziquantel (PZQ) as a positive control. Primary screening allowed a 5.9% hit rate and generated two confirmed hits on adult worms; a prophylactic antianginal agent and an antihistaminic drug., Conclusion: With this standardized and reliable in vitro assay, important S. mansoni developmental stages up to LiS worms can be generated and cultured over an extended period. When exposed to a subset of the NCATS Pharmaceutical Collection, 3 compounds yielded a defined anti-schistosomal phenotype on juvenile worms. Translation of activity on perfused adult S. mansoni worms was achieved only for perhexiline (a prophylactic antianginal agent) and astemizole (an antihistaminic drug)., Competing Interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: TS is an employee of Ares Trading SA, an affiliate of Merck KGaA, Darmstadt, Germany. The other authors have declared that no competing interests exist.

Introduction: Schistosomiasis is a neglected tropical disease (NTD) caused by blood-dwelling flatworms which develop from skin-penetrating cercariae, the freely swimming water-borne infective stage of Schistosoma mansoni , into adult worms. This natural course of infection can be mimicked in experimental mouse models of schistosomiasis. However, only a maximum of 20-30% of penetrated cercariae mature into fecund adults. The reasons for this are unknown but could potentially involve soluble factors of the innate immune system, such as complement factors and preexisting, natural antibodies., Materials and Methods: Using our recently developed novel serum- and cell-free in vitro culture system for newly transformed schistosomula (NTS), which supports long-term larval survival, we investigated the effects of mouse serum and its major soluble complement factors C1q, C3, C4 as well as preexisting, natural IgM in vitro and assessed worm development in vivo by infecting complement and soluble (s)IgM-deficient animals., Results: In contrast to sera from humans and a broad variety of mammalian species, serum from mice, surprisingly, killed parasites already at skin stage in vitro . Interestingly, the most efficient killing component(s) were heat-labile but did not include important members of the perhaps best known family of heat-labile serum factors, the complement system, nor consisted of complement-activating natural immunoglobulins. Infection of complement C1q and sIgM-deficient mice with S. mansoni as well as in vitro tests with sera from mice deficient in C3 and C4 revealed no major role for these soluble factors in vivo in regard to parasite maturation, fecundity and associated immunopathology. Rather, the reduction of parasite maturation from cercariae to adult worms was comparable to wild-type mice., Conclusion: This study reveals that not yet identified heat-labile serum factors are major selective determinants of the host-specificity of schistosomiasis, by directly controlling schistosomal development and survival., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Anisuzzaman, Frahm, Prodjinotho, Bhattacharjee, Verschoor and Prazeres da Costa.)

Background: The arsenal in anthelminthic treatment against schistosomiasis is limited and relies almost exclusively on a single drug, praziquantel (PZQ). Thus, resistance to PZQ could constitute a major threat. Even though PZQ is potent in killing adult worms, its activity against earlier stages is limited. Current in vitro drug screening strategies depend on newly transformed schistosomula (NTS) for initial hit identification, thereby limiting sensitivity to new compounds predominantly active in later developmental stages. Therefore, the aim of this study was to establish a highly standardized, straightforward and reliable culture method to generate and maintain advanced larval stages in vitro. We present here how this method can be a valuable tool to test drug efficacy at each intermediate larval stage, reducing the reliance on animal use (3Rs)., Methodology/principal Findings: Cercariae were mechanically transformed into skin-stage (SkS) schistosomula and successfully cultured for up to four weeks with no loss in viability in a commercially available medium. Under these serum- and cell-free conditions, development halted at the lung-stage (LuS). However, the addition of human serum (HSe) propelled further development into liver stage (LiS) worms within eight weeks. Skin and lung stages, as well as LiS, were submitted to 96-well drug screening assays using known anti-schistosomal compounds such as PZQ, oxamniquine (OXM), mefloquine (MFQ) and artemether (ART). Our findings showed stage-dependent differences in larval susceptibility to these compounds., Conclusion: With this robust and highly standardized in vitro assay, important developmental stages of S. mansoni up to LiS worms can be generated and maintained over prolonged periods of time. The phenotype of LiS worms, when exposed to reference drugs, was comparable to most previously published works for ex vivo harvested adult worms. Therefore, this in vitro assay can help reduce reliance on animal experiments in search for new anti-schistosomal drugs., Competing Interests: The authors have declared that no competing interests exist.

Early exposure to immune stimuli, including maternal infection during the perinatal period, is increasingly recognized to affect immune predisposition during later life. This includes exposure to not only viral and bacterial infection but also parasitic helminths which remain widespread. Noted effects of helminth infection, including altered incidence of atopic inflammation and vaccine responsiveness, support further research into the impact these infections have for skewing immune responses. At the same time, despite a sea of recommendations, clear phenotypic and mechanistic understandings of how environmental perturbations in pregnancy and nursing modify immune predisposition and allergy in offspring remain unrefined. Schistosomes, as strong inducers of type 2 immunity embedded in a rich network of regulatory processes, possess strong abilities to shift inflammatory and allergic diseases in infected hosts, for example by generating feedback loops that impair T cell responses to heterologous antigens. Based on the current literature on schistosomiasis, we explore in this review how maternal schistosome infection could drive changes in immune system development of offspring and how this may lead to identifying factors involved in altering responses to vaccination as well as manifestations of immune disorders including allergy.

The molecular mechanisms through which dendritic cells (DCs) prime T helper 2 (Th2) responses, including those elicited by parasitic helminths, remain incompletely understood. Here, we report that soluble egg antigen (SEA) from Schistosoma mansoni, which is well known to drive potent Th2 responses, triggers DCs to produce prostaglandin E2 (PGE2), which subsequently-in an autocrine manner-induces OX40 ligand (OX40L) expression to license these DCs to drive Th2 responses. Mechanistically, SEA was found to promote PGE2 synthesis through Dectin-1 and Dectin-2, and via a downstream signaling cascade involving spleen tyrosine kinase (Syk), extracellular signal-regulated kinase (ERK), cytosolic phospholipase A2 (cPLA2), and cyclooxygenase 1 and 2 (COX-1 and COX-2). In addition, this pathway was activated independently of the actions of omega-1 (ω-1), a previously described Th2-priming glycoprotein present in SEA. These findings were supported by in vivo murine data showing that ω-1-independent Th2 priming by SEA was mediated by Dectin-2 and Syk signaling in DCs. Finally, we found that Dectin-2-/-, and to a lesser extent Dectin-1-/- mice, displayed impaired Th2 responses and reduced egg-driven granuloma formation following S. mansoni infection, highlighting the physiological importance of this pathway in Th2 polarization during a helminth infection. In summary, we identified a novel pathway in DCs involving Dectin-1/2-Syk-PGE2-OX40L through which Th2 immune responses are induced.

Schistosomiasis is a severe and chronic disease caused by the parasitic trematode Schistosoma mansoni after deposition of eggs in the liver and intestines. The immune response to S. mansoni eggs is characterized by increased Th2 cells, eosinophilia, and high serum IgE levels. Granulomas are formed around the eggs to protect the organs against tissue damage caused by toxic products that are secreted from the eggs. Egg-derived components have further been shown to activate the IgE-mediated release of IL-4 and IL-13 from basophils, suggesting that basophils could be involved in protection against a fatal course of infection. Using T cell-specific IL-4/IL-13-deficient mice and basophil-deficient Mcpt8Cre mice, we determined the contribution of Th2 cells and basophils for protective immunity against S. mansoni egg-induced pathology during the patent stage of infection. Our results demonstrate that T cell-derived IL-4/IL-13 was essential for granuloma formation, IgE production, basophilia, differentiation of alternatively activated macrophages, and protection against fatal infection. Although basophils were recruited into liver granulomas, they appeared to be dispensable as a source of IL-4/IL-13 both for differentiation of Th2 cells and for prevention of weight loss and mortality., (Copyright © 2014 by The American Association of Immunologists, Inc.)

The continual rise of asthma in industrialised countries stands in strong contrast to the situation in developing lands. According to the modified Hygiene Hypothesis, helminths play a major role in suppressing bystander immune responses to allergens, and both epidemiological and experimental studies suggest that the tropical parasitic trematode Schistosoma mansoni elicits such effects. The focus of this study was to investigate which developmental stages of schistosome infection confer suppression of allergic airway inflammation (AAI) using ovalbumin (OVA) as a model allergen. Moreover, we assessed the functional role and localization of infection-induced CD4(+)Foxp3(+) regulatory T cells (Treg) in mediating such suppressive effects. Therefore, AAI was elicited using OVA/adjuvant sensitizations with subsequent OVA aerosolic challenge and was induced during various stages of infection, as well as after successful anti-helminthic treatment with praziquantel. The role of Treg was determined by specifically depleting Treg in a genetically modified mouse model (DEREG) during schistosome infection. Alterations in AAI were determined by cell infiltration levels into the bronchial system, OVA-specific IgE and Th2 type responses, airway hyper-sensitivity and lung pathology. Our results demonstrate that schistosome infection leads to a suppression of OVA-induced AAI when mice are challenged during the patent phase of infection: production of eggs by fecund female worms. Moreover, this ameliorating effect does not persist after anti-helminthic treatment, and depletion of Treg reverts suppression, resulting in aggravated AAI responses. This is most likely due to a delayed reconstitution of Treg in infected-depleted animals which have strong ongoing immune responses. In summary, we conclude that schistosome-mediated suppression of AAI requires the presence of viable eggs and infection-driven Treg cells. These data provide evidence that helminth derived products could be incorporated into treatment strategies that specifically target suppression of immune responses in AAI by inducing Treg cells.

NTS were cultured in HM supplemented with 200 U/ml Penicillin and 200 g/ml Streptomycin and 20% HSe for 1 week to generate LuS (B, D, F and H) and 6 weeks to obtain LiS (A, C, E, G) schistosomula. NTS were cultured in HM supplemented with 200 U/ml Penicillin and 200 g/ml Streptomycin and 20% HSe for 1 week to generate LuS (B, D, F and H) and 6 weeks to obtain LiS (A, C, E, G) schistosomula. ×× p <= 0.01 comparing HM vs. 1% HSe; ++ p <= 0.01 comparing HM vs. 5% HSe; p <= 0.01 comparing HM vs. 10% HSe; /=/= p <= 0.01 comparing HM vs. 20% HSe; ** comparing p <= 0.01 HM vs. 50% HSe. [Extracted from the article]

Background: Chronic hepatitis B develops more frequently in countries with high prevalence of helminth infections. The crosstalk between these 2 major liver-residing pathogens, Schistosoma mansoni and hepatitis B virus (HBV), is barely understood.Methods: We used state-of-the-art models for both acute and chronic HBV infection to study the pathogen-crosstalk during the different immune phases of schistosome infection.Results: Although liver pathology caused by schistosome infection was not affected by either acute or chronic HBV infection, S mansoni infection influenced HBV infection outcomes in a phase-dependent manner. Interferon (IFN)-γ secreting, HBV- and schistosome-specific CD8 T cells acted in synergy to reduce HBV-induced pathology during the TH1 phase and chronic phase of schistosomiasis. Consequently, HBV was completely rescued in IFN-γ-deficient or in TH2 phase coinfected mice demonstrating the key role of this cytokine. It is interesting to note that secondary helminth infection on the basis of persistent (chronic) HBV infection increased HBV-specific T-cell frequency and resulted in suppression of virus replication but failed to fully restore T-cell function and eliminate HBV.Conclusions: Thus, schistosome-induced IFN-γ had a prominent antiviral effect that outcompeted immunosuppressive effects of TH2 cytokines, whereas HBV coinfection did not alter schistosome pathogenicity. [ABSTRACT FROM AUTHOR]

The molecular mechanisms through which dendritic cells (DCs) prime T helper 2 (Th2) responses, including those elicited by parasitic helminths, remain incompletely understood. Here, we report that soluble egg antigen (SEA) from Schistosoma mansoni, which is well known to drive potent Th2 responses, triggers DCs to produce prostaglandin E2 (PGE2), which subsequently—in an autocrine manner—induces OX40 ligand (OX40L) expression to license these DCs to drive Th2 responses. Mechanistically, SEA was found to promote PGE2 synthesis through Dectin-1 and Dectin-2, and via a downstream signaling cascade involving spleen tyrosine kinase (Syk), extracellular signal-regulated kinase (ERK), cytosolic phospholipase A2 (cPLA2), and cyclooxygenase 1 and 2 (COX-1 and COX-2). In addition, this pathway was activated independently of the actions of omega-1 (ω-1), a previously described Th2-priming glycoprotein present in SEA. These findings were supported by in vivo murine data showing that ω-1–independent Th2 priming by SEA was mediated by Dectin-2 and Syk signaling in DCs. Finally, we found that Dectin-2−/−, and to a lesser extent Dectin-1−/− mice, displayed impaired Th2 responses and reduced egg-driven granuloma formation following S. mansoni infection, highlighting the physiological importance of this pathway in Th2 polarization during a helminth infection. In summary, we identified a novel pathway in DCs involving Dectin-1/2-Syk-PGE2-OX40L through which Th2 immune responses are induced. [ABSTRACT FROM AUTHOR]

The continual rise of asthma in industrialised countries stands in strong contrast to the situation in developing lands. According to the modified Hygiene Hypothesis, helminths play a major role in suppressing bystander immune responses to allergens, and both epidemiological and experimental studies suggest that the tropical parasitic trematode Schistosoma mansoni elicits such effects. The focus of this study was to investigate which developmental stages of schistosome infection confer suppression of allergic airway inflammation (AAI) using ovalbumin (OVA) as a model allergen. Moreover, we assessed the functional role and localization of infection-induced CD4+Foxp3+ regulatory T cells (Treg) in mediating such suppressive effects. Therefore, AAI was elicited using OVA/adjuvant sensitizations with subsequent OVA aerosolic challenge and was induced during various stages of infection, as well as after successful anti-helminthic treatment with praziquantel. The role of Treg was determined by specifically depleting Treg in a genetically modified mouse model (DEREG) during schistosome infection. Alterations in AAI were determined by cell infiltration levels into the bronchial system, OVA-specific IgE and Th2 type responses, airway hyper-sensitivity and lung pathology. Our results demonstrate that schistosome infection leads to a suppression of OVA-induced AAI when mice are challenged during the patent phase of infection: production of eggs by fecund female worms. Moreover, this ameliorating effect does not persist after anti-helminthic treatment, and depletion of Treg reverts suppression, resulting in aggravated AAI responses. This is most likely due to a delayed reconstitution of Treg in infected-depleted animals which have strong ongoing immune responses. In summary, we conclude that schistosome-mediated suppression of AAI requires the presence of viable eggs and infection-driven Treg cells. These data provide evidence that helminth derived products could be incorporated into treatment strategies that specifically target suppression of immune responses in AAI by inducing Treg cells. Author Summary: Infections with schistosomes, such as S. mansoni, S. japonicum and S. haematobium, are considered a major public health concern. Morbidity arises through granulomatous responses to eggs that become trapped in infected tissues. Interestingly, schistosomes belong to the group of helminths that have been shown to reduce allergy or autoimmunity. Indeed, the evidence provided by epidemiological surveys and experimental animal models has been so overwhelming that such helminths are now included in the Hygiene Hypothesis. However, since helminths provoke immunological responses that are similar to those seen in allergy (increased eosinophilia and IgE) it is suggested that additional mechanisms dampen such allergic responses. Helminth-induced regulatory T cells (Treg) are considered a component of these modulatory networks. Using an allergic airway inflammation model, we have elucidated that schistosome-mediated protection requires patency, that is, active egg production from fecund female worms. In addition, protection was shown to be mediated by infection-induced Treg. Interestingly, in endemic countries it is usually individuals with strong patent infections that show reduced allergic prevalence. Thus, further research into the immunomodulatory capacity of schistosome-egg derived factors may elucidate novel drug candidates or enhance treatment strategies to reduce allergic responses on the cellular level. [ABSTRACT FROM AUTHOR]

Helicobacter pylori chronically colonizes the stomach and is strongly associated with gastric cancer. Its concomitant occurrence with helminths such as schistosomes has been linked to reduced cancer incidence, presumably due to suppression of H. pylori -associated pro-inflammatory responses. However, experimental evidence in support of such a causal link or the mutual interaction of both pathogens is lacking. We investigated the effects of co-infection during the different immune phases of S. mansoni infection. Surprisingly, co-infected mice had increased H. pylori gastric colonization during the interferon gamma (IFNγ) phase of schistosome infection but reduced infiltration of T cells in the stomach due to misdirection of antigen-experienced CXCR3+ T cells to the liver. Unexpectedly, H. pylori co-infection resulted in partial protection from schistosome-induced liver damage. Here, we demonstrate that an increase in fibrosis-protective IL-13Ra2 is associated with H. pylori infection. Thus, our study strongly points to an immunological interaction of anatomically isolated pathogens, eventually resulting in altered disease pathology. • Co-infection of H. pylori and S. mansoni results in altered disease-specific pathology • S. mansoni infection induces misdirection of H. pylori -associated CXCR3+ T cells • Immune misdirection of cells is helminth-immune-phase dependent • H. pylori infection ameliorates schistosome-associated liver fibrosis Co-infection is ubiquitous in human populations and is yet not the most widely studied experimental topic. Bhattacharjee et al. demonstrate that the immunological interaction of two prominent, anatomically isolated human pathogens, H. pylori and S. mansoni , eventually results in an unusual, mutually ameliorating effect on the detrimental course of both infections. [ABSTRACT FROM AUTHOR]