H-IPSE Is a Pathogen-Secreted Host Nucleus-Infiltrating Protein (Infiltrin) Expressed Exclusively by the Schistosoma haematobium Egg Stage

The PPE2 protein of Mycobacterium tuberculosis is secreted during infection and facilitates mycobacterial survival inside the host

Mycobacterium tuberculosis secrets various effector proteins to evade host immune responses for facilitating its intracellular survival. The bacterial genome encodes several unique PE/PPE family proteins, which have been implicated to play important role in mycobacterial pathogenesis. A member of this family, PPE2 have been shown to contain a monopartite nuclear localization signal (NLS) and a DNA binding domain. In this study, we demonstrate that PPE2 protein is present in the sera of mice infected with either M. smegmatis expressing PPE2 or a clinical strain of M. tuberculosis (CDC1551). It was found that exogenously added PPE2 can permeate through the macrophage cell membrane and eventually translocate into the nucleus which requires the presence of NLS which showed considerable homology to HIV-tat like cell permeable peptides. Exogenously added PPE2 could inhibit NO production and decreased mycobacterial survival in macrophages. PPE2-null mutant of M. tuberculosis failed to inhibit NO production and had poor survival in macrophages which could be rescued by complementation with full-length PPE2. PPE2-null mutants also had poor survival in the lungs of infected mice indicating that PPE2 even when present in the bloodstream can confer a survival advantage to mycobacteria.

Chromosome-level genome of Schistosoma haematobium underpins genome-wide explorations of molecular variation

Urogenital schistosomiasis is caused by the blood fluke Schistosoma haematobium and is one of the most neglected tropical diseases worldwide, afflicting > 100 million people. It is characterised by granulomata, fibrosis and calcification in urogenital tissues, and can lead to increased susceptibility to HIV/AIDS and squamous cell carcinoma of the bladder. To complement available treatment programs and break the transmission of disease, sound knowledge and understanding of the biology and ecology of S. haematobium is required. Hybridisation/introgression events and molecular variation among members of the S. haematobium-group might effect important biological and/or disease traits as well as the morbidity of disease and the effectiveness of control programs including mass drug administration. Here we report the first chromosome-contiguous genome for a well-defined laboratory line of this blood fluke. An exploration of this genome using transcriptomic data for all key developmental stages allowed us to refine gene models (including non-coding elements) and annotations, discover ‘new’ genes and transcription profiles for these stages, likely linked to development and/or pathogenesis. Molecular variation within S. haematobium among some geographical locations in Africa revealed unique genomic ‘signatures’ that matched species other than S. haematobium, indicating the occurrence of introgression events. The present reference genome (designated Shae.V3) and the findings from this study solidly underpin future functional genomic and molecular investigations of S. haematobium and accelerate systematic, large-scale population genomics investigations, with a focus on improved and sustained control of urogenital schistosomiasis.

More than 100 million people are infected with the carcinogenic blood fluke Schistosoma haematobium, the aetiological agent of urogenital schistosomiasis—a neglected tropical disease (NTD). In spite of its major significance, little is known about this fluke, its interactions with the human and snail intermediate hosts and the pathogenesis of the urogenital form of schistosomiasis at the molecular and biochemical levels. To enable research in these areas, we report the first chromosome-level genome and markedly enhanced gene models for S. haematobium. Comparative genomic analyses also reveal evidence of past introgression events between or among closely related schistosome species. This present reference genome for S. haematobium and the findings from this study should underpin future functional genomic and molecular investigations of S. haematobium and accelerate systematic, large-scale population genomics investigations, with a focus on improved control of urogenital schistosomiasis.

Schistosome immunomodulators

Schistosomes are long lived, intravascular parasitic platyhelminths that infect >200 million people globally. The molecular mechanisms used by these blood flukes to dampen host immune responses are described in this review. Adult worms express a collection of host-interactive tegumental ectoenzymes that can cleave host signaling molecules such as the "alarmin" ATP (cleaved by SmATPDase1), the platelet activator ADP (SmATPDase1, SmNPP5), and can convert AMP into the anti-inflammatory mediator adenosine (SmAP). SmAP can additionally cleave the lipid immunomodulator sphingosine-1-phosphate and the proinflammatory anionic polymer, polyP. In addition, the worms release a barrage of proteins (e.g., SmCB1, SjHSP70, cyclophilin A) that can impinge on immune cell function. Parasite eggs also release their own immunoregulatory proteins (e.g., IPSE/α1, omega1, SmCKBP) as do invasive cercariae (e.g., Sm16, Sj16). Some schistosome glycans (e.g., LNFPIII, LNnT) and lipids (e.g., Lyso-PS, LPC), produced by several life stages, likewise affect immune cell responses. The parasites not only produce eicosanoids (e.g., PGE2, PGD2-that can be anti-inflammatory) but can also induce host cells to release these metabolites. Finally, the worms release extracellular vesicles (EVs) containing microRNAs, and these too have been shown to skew host cell metabolism. Thus, schistosomes employ an array of biomolecules-protein, lipid, glycan, nucleic acid, and more, to bend host biochemistry to their liking. Many of the listed molecules have been individually shown capable of inducing aspects of the polarized Th2 response seen following infection (with the generation of regulatory T cells (Tregs), regulatory B cells (Bregs) and anti-inflammatory, alternatively activated (M2) macrophages). Precisely how host cells integrate the impact of these myriad parasite products following natural infection is not known. Several of the schistosome immunomodulators described here are in development as novel therapeutics against autoimmune, inflammatory, and other, nonparasitic, diseases.

Immunomics-guided discovery of serum and urine antibodies for diagnosing urogenital schistosomiasis: a biomarker identification study

Background

Sensitive diagnostics are needed for effective management and surveillance of schistosomiasis so that current transmission interruption goals set by WHO can be achieved. We aimed to screen the Schistosoma haematobium secretome to find antibody biomarkers of schistosome infection, validate their diagnostic performance in samples from endemic populations, and evaluate their utility as point of care immunochromatographic tests (POC-ICTs) to diagnose urogenital schistosomiasis in the field.

Methods

We did a biomarker identification study, in which we constructed a proteome array containing 992 validated and predicted proteins from S haematobium and screened it with serum and urine antibodies from endemic populations in Gabon, Tanzania, and Zimbabwe. Arrayed antigens that were IgG-reactive and a select group of antigens from the worm extracellular vesicle proteome, predicted to be diagnostically informative, were then evaluated by ELISA using the same samples used to probe arrays, and samples from individuals residing in a low-endemicity setting (ie, Pemba and Unguja islands, Zanzibar, Tanzania). The two most sensitive and specific antigens were incorporated into POC-ICTs to assess their ability to diagnose S haematobium infection from serum in a field-deployable format.

Findings

From array probing, in individuals who were infected, 208 antigens were the targets of significantly elevated IgG responses in serum and 45 antigens were the targets of significantly elevated IgG responses in urine. Of the five proteins that were validated by ELISA, Sh-TSP-2 (area under the curve [AUC]_serum=0·98 [95% CI 0·95–1·00]; AUC_urine=0·96 [0·93–0·99]), and MS3_01370 (AUC_serum=0·93 [0·89–0·97]; AUC_urine=0·81 [0·72–0·89]) displayed the highest overall diagnostic performance in each biofluid and exceeded that of S haematobium-soluble egg antigen in urine (AUC=0·79 [0·69–0·90]). When incorporated into separate POC-ICTs, Sh-TSP-2 showed absolute specificity and a sensitivity of 75% and MS3_01370 showed absolute specificity and a sensitivity of 89%.

Interpretation

We identified numerous biomarkers of urogenital schistosomiasis that could form the basis of novel antibody diagnostics for this disease. Two of these antigens, Sh-TSP-2 and MS3_01370, could be used as sensitive, specific, and field-deployable diagnostics to support schistosomiasis control and elimination initiatives, with particular focus on post-elimination surveillance.

Funding

Australian Trade and Investment Commission and Merck Global Health Institute.

IPSE, a parasite-derived, host immunomodulatory infiltrin protein, alleviates resiniferatoxin-induced bladder pain

The transient receptor potential cation channel subfamily V member 1 (TRPV1) receptor is an important mediator of nociception and its expression is enriched in nociceptive neurons. TRPV1 signaling has been implicated in bladder pain and is a potential analgesic target. Resiniferatoxin is the most potent known agonist of TRPV1. Acute exposure of the rat bladder to resiniferatoxin has been demonstrated to result in pain-related freezing and licking behaviors that are alleviated by virally encoded IL-4. The interleukin-4-inducing principle of Schistosoma mansoni eggs (IPSE) is a powerful inducer of IL-4 secretion, and is also known to alter host cell transcription through a nuclear localization sequence-based mechanism. We previously reported that IPSE ameliorates ifosfamide-induced bladder pain in an IL-4- and nuclear localization sequence-dependent manner. We hypothesized that pre-administration of IPSE to resiniferatoxin-challenged mice would dampen pain-related behaviors. IPSE indeed lessened resiniferatoxin-triggered freezing behaviors in mice. This was a nuclear localization sequence-dependent phenomenon, since administration of a nuclear localization sequence mutant version of IPSE abrogated IPSE’s analgesic effect. In contrast, IPSE’s analgesic effect did not seem IL-4-dependent, since use of anti-IL-4 antibody in mice given both IPSE and resiniferatoxin did not significantly affect freezing behaviors. RNA-Seq analysis of resiniferatoxin- and IPSE-exposed bladders revealed differential expression of TNF/NF-κb-related signaling pathway genes. In vitro testing of IPSE uptake by urothelial cells and TRPV1-expressing neuronal cells showed uptake by both cell types. Thus, IPSE’s nuclear localization sequence-dependent therapeutic effects on TRPV1-mediated bladder pain may act on TRPV1-expressing neurons and/or may rely upon urothelial mechanisms.

Does Schistosoma Mansoni Facilitate Carcinogenesis?

Schistosomiasis is one of the most prominent parasite-induced infectious diseases, causing tremendous medical and socioeconomic problems. Current studies have reported on the spread of endemic regions and the fear of development of resistance against praziquantel, the only effective drug available. Among the Schistosoma species, only S. haematobium is classified as a Group 1 carcinogen (definitely cancerogenic to humans), causing squamous cell carcinoma of the bladder, whereas infection with S. mansoni is included in Group 3 of carcinogenic hazards to humans by the International Agency for Research on Cancer (IARC), indicating insufficient evidence to determine its carcinogenicity. Nevertheless, although S. mansoni has not been discussed as an organic carcinogen, the multiplicity of case reports, together with recent data from animal models and cell culture experiments, suggests that this parasite can predispose patients to or promote hepatic and colorectal cancer. In this review, we discuss the current data, with a focus on new developments regarding the association of S. mansoni infection with human cancer and the recently discovered biomolecular mechanisms by which S. mansoni may predispose patients to cancer development and carcinogenesis.

Modulation of the Host Immune Response by Schistosome Egg-Secreted Proteins Is a Critical Avenue of Host-Parasite Communication

During a schistosome infection, the interactions that occur between the mammalian host and the parasite change rapidly once egg laying begins. Both juvenile and adult schistosomes adapt to indefinitely avoid the host immune system. In contrast, the survival of eggs relies on quickly traversing from the host. Following the commencement of egg laying, the host immune response undergoes a shift from a type 1 helper (Th1) inflammatory response to a type 2 helper (Th2) granulomatous response. This change is driven by immunomodulatory proteins within the egg excretory/secretory products (ESPs), which interact with host cells and alter their behaviour to promote egg translocation. However, in parallel, these ESPs also provoke the development of chronic schistosomiasis pathology. Recent studies using high-throughput proteomics have begun to characterise the components of schistosome egg ESPs, particularly those of Schistosoma mansoni, S. japonicum and S. haematobium. Future application of this knowledge may lead to the identification of proteins with novel immunomodulatory activity or pathological importance. However, efforts in this area are limited by a lack of in situ or in vivo functional characterisation of these proteins. This review will highlight the current knowledge of the content and demonstrated functions of schistosome egg ESPs.

Schistosome Infection and Schistosome-Derived Products as Modulators for the Prevention and Alleviation of Immunological Disorders

Parasitic helminths, comprising the flatworms (tapeworms and flukes) and nematodes (roundworms), have plagued humans persistently over a considerable period of time. It is now known that the degree of exposure to these and other pathogens inversely correlates with the incidence of both T helper 1 (Th1)-mediated autoimmunity and Th2-mediated allergy. Accordingly, there has been recent increased interest in utilizing active helminth worm infections and helminth-derived products for the treatment of human autoimmune and inflammatory diseases and to alleviate disease severity. Indeed, there is an accumulating list of novel helminth derived molecules, including proteins, peptides, and microRNAs, that have been shown to exhibit therapeutic potential in a variety of disease models. Here we consider the blood-dwelling schistosome flukes, which have evolved subtle immune regulatory mechanisms that promote parasite survival but at the same time minimize host tissue immunopathology. We review and discuss the recent advances in using schistosome infection and schistosome-derived products as therapeutics to treat or mitigate human immune-related disorders, including allergic asthma, arthritis, colitis, diabetes, sepsis, cystitis, and cancer.

Spirocerca lupi Proteomics and Its Role in Cancer Development: An Overview of Spirocercosis-Induced Sarcomas and Revision of Helminth-Induced Carcinomas

Spirocerca lupi is a parasitic nematode of canids that induces a myriad of clinical manifestations in its host and, in 25% of infections, leads to the formation of sarcomas. The description of the protein composition of the excretory and secretory products (Sl-ESP) of S. lupi has shed light on its possible interactions with the host environment, including migration within the host and mechanisms of immunomodulation. Despite this, the process by which S. lupi induces cancer in the dog remains poorly understood, and some hypotheses have arisen regarding these possible mechanisms. In this review, we discuss the role of specific ESP from the carcinogenic helminths Clonorchis sinensis, Opisthorchis viverrini and Schistosoma haematobium in inducing chronic inflammation and cancer in their host’s tissues. The parasitic worms Taenia solium, Echinococcus granulosus, Heterakis gallinarum, Trichuris muris and Strongyloides stercoralis, which have less-characterized mechanisms of cancer induction, are also analyzed. Based on the pathological findings in spirocercosis and the mechanisms by which other parasitic helminths induce cancer, we propose that the sustained inflammatory response in the dog´s tissues produced in response to the release of Sl-ESP homologous to those of other carcinogenic worms may lead to the malignant process in infected dogs.

Interleukin (IL)-33 is dispensable for Schistosoma mansoni worm maturation and the maintenance of egg-induced pathology in intestines of infected mice

BACKGROUND

Schistosomes are trematode worms that dwell in their definitive host's blood vessels, where females lay eggs that need to be discharged into the environment with host excreta to maintain their life-cycle. Both worms and eggs require type 2 immunity for their maturation and excretion, respectively. However, the immune molecules that orchestrate such immunity remain unclear. Interleukin (IL)-33 is one of the epithelium-derived cytokines that induce type 2 immunity in tissues. The aim of this study was to determine the role of IL-33 in the maturation, reproduction and excretion of Schistosoma mansoni eggs, and in the maintenance of egg-induced pathology in the intestines of mice.

METHODS

The morphology of S. mansoni worms and the number of eggs in intestinal tissues were studied at different time points post-infection in S. mansoni-infected IL-33-deficient (IL-33-/-) and wild-type (WT) mice. IL-5 and IL-13 production in the spleens and mesenteric lymph nodes were measured. Tissue histology was performed on the terminal ilea of both infected and non-infected mice.

RESULTS

Worms from IL-33-/- and WT mice did not differ morphologically at 4 and 6 weeks post-infection (wpi). The number of eggs in intestinal tissues of IL-33-/- and WT mice differed only slightly. At 6 wpi, IL-33-/- mice presented impaired type 2 immunity in the intestines, characterized by a decreased production of IL-5 and IL-13 in mesenteric lymph nodes and fewer inflammatory infiltrates with fewer eosinophils in the ilea. There was no difference between IL-33-/- and WT mice in the levels of IL-25 and thymic stromal lymphopoietin (TSLP) in intestinal tissues.

CONCLUSIONS

Despite its ability to initiate type 2 immunity in tissues, IL-33 alone seems dispensable for S. mansoni maturation and its absence may not affect much the accumulation of eggs in intestinal tissues. The transient impairment of type 2 immunity observed in the intestines, but not spleens, highlights the importance of IL-33 over IL-25 and TSLP in initiating, but not maintaining, locally-induced type 2 immunity in intestinal tissues during schistosome infection. Further studies are needed to decipher the role of each of these molecules in schistosomiasis and clarify the possible interactions that might exist between them.

IPSE, a urogenital parasite-derived immunomodulatory molecule, suppresses bladder pathogenesis and anti-microbial peptide gene expression in bacterial urinary tract infection

BACKGROUND

Parasitic infections can increase susceptibility to bacterial co-infections. This may be true for urogenital schistosomiasis and bacterial urinary tract co-infections (UTI). We previously reported that this co-infection is facilitated by S. haematobium eggs triggering interleukin-4 (IL-4) production and sought to dissect the underlying mechanisms. The interleukin-4-inducing principle from Schistosoma mansoni eggs (IPSE) is one of the most abundant schistosome egg-secreted proteins and binds to IgE on the surface of basophils and mast cells to trigger IL-4 release. IPSE can also translocate into host nuclei using a nuclear localization sequence (NLS) to modulate host transcription. We hypothesized that IPSE is the factor responsible for the ability of S. haematobium eggs to worsen UTI pathogenesis.

METHODS

Mice were intravenously administered a single 25 μg dose of recombinant S. haematobium-derived IPSE, an NLS mutant of IPSE or PBS. Following IPSE exposure, mice were serially weighed and organs analyzed by histology to assess for toxicity. Twenty-four hours after IPSE administration, mice were challenged with the uropathogenic E. coli strain UTI89 by urethral catheterization. Bacterial CFU were measured using urine. Bladders were examined histologically for UTI-triggered pathogenesis and by PCR for antimicrobial peptide and pattern recognition receptor expression.

RESULTS

Unexpectedly, IPSE administration did not result in significant differences in urine bacterial CFU. However, IPSE administration did lead to a significant reduction in UTI-induced bladder pathogenesis and the expression of anti-microbial peptides in the bladder. Despite the profound effect of IPSE on UTI-triggered bladder pathogenesis and anti-microbial peptide production, mice did not demonstrate systemic ill effects from IPSE exposure.

CONCLUSIONS

Our data show that IPSE may play a major role in S. haematobium-associated urinary tract co-infection, albeit in an unexpected fashion. These findings also indicate that IPSE either works in concert with other IL-4-inducing factors to increase susceptibility of S. haematobium-infected hosts to bacterial co-infection or does not contribute to enhancing vulnerability to this co-infection.

A comparative proteomics analysis of the egg secretions of three major schistosome species

Morbidity associated with hepatic and urogenital schistosomiasis stems primarily from the host immune response directed against schistosome eggs. When eggs become entrapped in host tissues, the development of fibrotic plaques drives downstream pathology. These events occur due to the antigenic nature of egg excretory/secretory products (ESPs). Both Schistosoma mansoni and S. japonicum ESPs have been shown to interact with several cell populations in the host liver including hepatocytes, macrophages, and hepatic stellate cells, with both immunomodulatory and pathological consequences. Several protein components of the ESPs of S. mansoni and S. japonicum eggs have been characterised; however, studies into the collective contents of schistosome egg ESPs are lacking. Utilising shotgun mass spectrometry and an array of in silico analyses, we identified 266, 90 and 50 proteins within the S. mansoni, S. japonicum and S. haematobium egg secretomes respectively. We identified numerous proteins with already established immunomodulatory activities, vaccine candidates and vesicle markers. Relatively few common orthologues within the ESPs were identified by BLAST, indicating that the three egg secretomes differ in content significantly. Having a clearer understanding of these components may lead to the identification of new proteins with uncharacterised immunomodulatory potential or pathological relevance. This will enhance our understanding of host-parasite interactions, particularly those occurring during chronic schistosomiasis, and pave the way towards novel therapeutics and vaccines.

IPSE, an abundant egg-secreted protein of the carcinogenic helminth Schistosoma haematobium, promotes proliferation of bladder cancer cells and angiogenesis

BACKGROUND

Schistosoma haematobium, the helminth causing urogenital schistosomiasis, is a known bladder carcinogen. Despite the causal link between S. haematobium and bladder cancer, the underlying mechanisms are poorly understood. S. haematobium oviposition in the bladder is associated with angiogenesis and urothelial hyperplasia. These changes may be pre-carcinogenic events in the bladder. We hypothesized that the Interleukin-4-inducing principle of Schistosoma mansoni eggs (IPSE), an S. haematobium egg-secreted "infiltrin" protein that enters host cell nuclei to alter cellular activity, is sufficient to induce angiogenesis and urothelial hyperplasia. Methods: Mouse bladders injected with S. haematobium eggs were analyzed via microscopy for angiogenesis and urothelial hyperplasia. Endothelial and urothelial cell lines were incubated with recombinant IPSE protein or an IPSE mutant protein that lacks the native nuclear localization sequence (NLS-) and proliferation measured using CFSE staining and real-time monitoring of cell growth. IPSE's effects on urothelial cell cycle status was assayed through propidium iodide staining. Endothelial and urothelial cell uptake of fluorophore-labeled IPSE was measured. Findings: Injection of S. haematobium eggs into the bladder triggers angiogenesis, enhances leakiness of bladder blood vessels, and drives urothelial hyperplasia. Wild type IPSE, but not NLS-, increases proliferation of endothelial and urothelial cells and skews urothelial cells towards S phase. Finally, IPSE is internalized by both endothelial and urothelial cells. Interpretation: IPSE drives endothelial and urothelial proliferation, which may depend on internalization of the molecule. The urothelial effects of IPSE depend upon its NLS. Thus, IPSE is a candidate pro-carcinogenic molecule of S. haematobium.

SUMMARY

Schistosoma haematobium acts as a bladder carcinogen through unclear mechanisms. The S. haematobium homolog of IPSE, a secreted schistosome egg immunomodulatory molecule, enhances angiogenesis and urothelial proliferation, hallmarks of pre-carcinogenesis, suggesting IPSE is a key pro-oncogenic molecule of S. haematobium.

Immunomodulation and Immune Escape Strategies of Gastrointestinal Helminths and Schistosomes

Parasitic worms (helminths) developed various immunoregulatory mechanisms to counteract the immune system of their host. The increasing identification and characterization of helminth-derived factors with strong immune modulatory activity provides novel insights into immune escape strategies of helminths. Such factors might be good targets to enhance anti-helminthic immune responses. In addition, immunosuppressive helminth-derived factors could be useful to develop new therapeutic strategies for treatment of chronic inflammatory conditions. This review will take an in depth look at the effects of immunomodulatory molecules produced by different helminths with a focus on schistosomes and mouse models of hookworm infections.

Schistosoma mansoni Egg-Secreted Antigens Activate Hepatocellular Carcinoma-Associated Transcription Factors c-Jun and STAT3 in Hamster and Human Hepatocytes

Clinical data have provided evidence that schistosomiasis can promote hepatocellular carcinogenesis. c-Jun and STAT3 are critical regulators of liver cancer development and progression. The aim of the present study was to investigate the hepatocellular activation of c-Jun and STAT3 by Schistosoma mansoni infection. Expression and function of c-Jun and STAT3 as well as proliferation and DNA repair were analyzed by western blotting, electrophoretic mobility-shift assay, and immunohistochemistry in liver of S. mansoni-infected hamsters, Huh7 cells, primary hepatocytes, and human liver biopsies. Hepatocellular activation of c-Jun was demonstrated by nuclear translocation of c-Jun, enhanced phosphorylation (Ser73), and AP-1/DNA-binding in response to S. mansoni infection. Nuclear c-Jun staining pattern around lodged eggs without ambient immune reaction, and directionally from granuloma to the central veins, suggested that substances released from schistosome eggs were responsible for the observed effects. In addition, hepatocytes with c-Jun activation show cell activation and DNA double-strand breaks. These findings from the hamster model were confirmed by analyses of human biopsies from patients with schistosomiasis. Cell culture experiments finally demonstrated that activation of c-Jun and STAT3 as well as DNA repair were induced by an extract from schistosome eggs (soluble egg antigens) and culture supernatants of live schistosome egg (egg-conditioned medium), and in particular by IPSE/alpha-1, the major component secreted by live schistosome eggs. The permanent activation of hepatocellular carcinoma-associated proto-oncogenes such as c-Jun and associated transcription factors including STAT3 by substances released from tissue-trapped schistosome eggs may be important factors contributing to the development of liver cancer in S. mansoni-infected patients. Therefore, identification and therapeutic targeting of the underlying pathways is a useful strategy to prevent schistosomiasis-associated carcinogenesis.

The Potential Role of Schistosome-Associated Factors as Therapeutic Modulators of the Immune System

The parasites and eggs of helminths, including schistosomes, are associated with factors that can modulate the nature and outcomes of host immune responses, particularly enhancing type 2 immunity and impairing the effects of type 1 and type 17 immunity. The main species of schistosomes that cause infection in humans are capable of generating a microenvironment that allows survival of the parasite by evasion of the immune response. Schistosome infections are associated with beneficial effects on chronic immune disorders, including allergies, autoimmune diseases, and alloimmune responses. Recently, there has been increasing research interest in the role of schistosomes in immunoregulation during human infection, and the mechanisms underlying these roles continue to be investigated. Further studies may identify potential opportunities to develop new treatments for immune disease. In this review, we provide an update on the advances in our understanding of schistosome-associated modulation of the cells of the innate and adaptive immune systems as well as the potential role of schistosome-associated factors as therapeutic modulators of immune disorders, including allergies, autoimmune diseases, and transplant immunopathology. We also discuss potential opportunities for targeting schistosome-induced immunoregulation for future translation to the clinical setting.

Interleukin-4 Signaling Plays a Major Role in Urogenital Schistosomiasis-Associated Bladder Pathogenesis

Interleukin-4 (IL-4) is crucial in many helminth infections, but its role in urogenital schistosomiasis, infection with Schistosoma haematobium worms, remains poorly understood due to a historical lack of animal models. The bladder pathology of urogenital schistosomiasis is caused by immune responses to eggs deposited in the bladder wall. A range of pathology occurs, including urothelial hyperplasia and cancer, but associated mechanisms and links to IL-4 are largely unknown. We modeled urogenital schistosomiasis by injecting the bladder walls of IL-4 receptor-alpha knockout (Il4ra-/- ) and wild-type mice with S. haematobium eggs. Readouts included bladder histology and ex vivo assessments of urothelial proliferation, cell cycle, and ploidy status. We also quantified the effects of exogenous IL-4 on urothelial cell proliferation in vitro, including cell cycle status and phosphorylation patterns of major downstream regulators in the IL-4 signaling pathway. There was a significant decrease in the intensity of granulomatous responses to bladder-wall-injected S. haematobium eggs in Il4ra-/- versus wild-type mice. S. haematobium egg injection triggered significant urothelial proliferation, including evidence of urothelial hyper-diploidy and cell cycle skewing in wild-type but not Il4ra-/- mice. Urothelial exposure to IL-4 in vitro led to cell cycle polarization and increased phosphorylation of AKT. Our results show that IL-4 signaling is required for key pathogenic features of urogenital schistosomiasis and that particular aspects of this signaling pathway may exert these effects directly on the urothelium. These findings point to potential mechanisms by which urogenital schistosomiasis promotes bladder carcinogenesis.

Schistosomiasis then and now: what has changed in the last 100 years?

Only with the completion of the life cycles of Fasciola hepatica in 1883 and 30 years later those of Schistosoma japonicum (1913), Schistosoma haematobium and Schistosoma mansoni (1915) did research on schistosomiasis really get underway. One of the first papers by Cawston in 1918, describing attempts to establish the means of transmission of S. haematobium in Natal, South Africa, forms the historical perspective against which to judge where we are now. Molecular biology techniques have produced a much better definition of the complexity of the schistosome species and their snail hosts, but also revealed the extent of hybridization between human and animal schistosomes that may impact on parasite adaptability. While diagnostics have greatly improved, the ability to detect single worm pair infections routinely, still falls short of its goal. The introduction of praziquantel ~1982 has revolutionized the treatment of infected individuals and led directly to the mass drug administration programmes. In turn, the severe pathological consequences of high worm burdens have been minimized, and for S. haematobium infections the incidence of associated squamous cell carcinoma has been reduced. In comparison, the development of effective vaccines has yet to come to fruition. The elimination of schistosomiasis japonica from Japan shows what is possible, using multiple lines of approach, but the clear and present danger is that the whole edifice of schistosome control is balanced on the monotherapy of praziquantel, and the development of drug resistance could topple that.

In-depth proteomic characterization of Schistosoma haematobium: Towards the development of new tools for elimination

BACKGROUND

Schistosomiasis is a neglected disease affecting hundreds of millions worldwide. Of the three main species affecting humans, Schistosoma haematobium is the most common, and is the leading cause of urogenital schistosomiasis. S. haematobium infection can cause different urogenital clinical complications, particularly in the bladder, and furthermore, this parasite has been strongly linked with squamous cell carcinoma. A comprehensive analysis of the molecular composition of its different proteomes will contribute to developing new tools against this devastating disease.

METHODS AND FINDINGS

By combining a comprehensive protein fractionation approach consisting of OFFGEL electrophoresis with high-throughput mass spectrometry, we have performed the first in-depth characterisation of the different discrete proteomes of S. haematobium that are predicted to interact with human host tissues, including the secreted and tegumental proteomes of adult flukes and secreted and soluble egg proteomes. A total of 662, 239, 210 and 138 proteins were found in the adult tegument, adult secreted, soluble egg and secreted egg proteomes, respectively. In addition, we probed these distinct proteomes with urine to assess urinary antibody responses from naturally infected human subjects with different infection intensities, and identified adult fluke secreted and tegument extracts as being the best predictors of infection.

CONCLUSION

We provide a comprehensive dataset of proteins from the adult and egg stages of S. haematobium and highlight their utility as diagnostic markers of infection intensity. Protein composition was markedly different between the different extracts, highlighting the distinct subsets of proteins that different development stages present in their different niches. Furthermore, we have identified adult fluke ES and tegument extracts as best predictors of infection using urine antibodies of naturally infected people. This study provides the first steps towards the development of novel tools to control this important neglected tropical disease.

IPSE, a parasite-derived host immunomodulatory protein, is a potential therapeutic for hemorrhagic cystitis

Chemotherapy-induced hemorrhagic cystitis is characterized by bladder pain and voiding dysfunction caused by hemorrhage and inflammation. Novel therapeutic options to treat hemorrhagic cystitis are needed. We previously reported that systemic administration of the Schistosomiasis hematobium-derived protein H-IPSE^H06 (IL-4-inducing principle from Schistosoma mansoni eggs) is superior to three doses of MESNA in alleviating hemorrhagic cystitis (Mbanefo EC, Le L, Pennington LF, Odegaard JI, Jardetzky TS, Alouffi A, Falcone FH, Hsieh MH. FASEB J 32: 4408-4419, 2018). Based on prior reports by others on S. mansoni IPSE (M-IPSE) and additional work by our group, we reasoned that H-IPSE mediates its effects on hemorrhagic cystitis by binding IgE on basophils and inducing IL-4 expression, promoting urothelial proliferation, and translocating to the nucleus to modulate expression of genes implicated in relieving bladder dysfunction. We speculated that local bladder injection of the S. hematobium IPSE ortholog IPSE^H03, hereafter called H-IPSE^H03, might be more efficacious in preventing hemorrhagic cystitis compared with systemic administration of IPSE^H06. We report that H-IPSE^H03, like M-IPSE and H-IPSE^H06, activates IgE-bearing basophils in a nuclear factor of activated T-cells reporter assay, indicating activation of the cytokine pathway. Furthermore, H-IPSE^H03 attenuates ifosfamide-induced increases in bladder wet weight in an IL-4-dependent fashion. H-IPSE^H03 relieves hemorrhagic cystitis-associated allodynia and modulates voiding patterns in mice. Finally, H-IPSE^H03 drives increased urothelial cell proliferation, suggesting that IPSE induces bladder repair mechanisms. Taken together, H-IPSE^H03 may be a potential novel therapeutic to treat hemorrhagic cystitis by basophil activation, attenuation of allodynia, and promotion of urothelial cell proliferation.

IPSE, a urogenital parasite-derived immunomodulatory protein, ameliorates ifosfamide-induced hemorrhagic cystitis through downregulation of pro-inflammatory pathways

Ifosfamide and other oxazaphosphorines can result in hemorrhagic cystitis, a constellation of complications caused by acrolein metabolites. We previously showed that a single dose of IPSE (Interleukin-4-inducing principle from Schistosoma eggs), a schistosome-derived host modulatory protein, can ameliorate ifosfamide-related cystitis; however, the mechanisms underlying this urotoxicity and its prevention are not fully understood. To provide insights into IPSE’s protective mechanism, we undertook transcriptional profiling of bladders from ifosfamide-treated mice, with or without pretreatment with IPSE or IPSE-NLS (a mutant of IPSE lacking nuclear localization sequence). Ifosfamide treatment upregulated a range of proinflammatory genes. The IL-1β-TNFα-IL-6 proinflammatory cascade via NFκB and STAT3 pathways was identified as the key driver of inflammation. The NRF2-mediated oxidative stress response pathway, which regulates heme homoeostasis and expression of antioxidant enzymes, was highly activated. Anti-inflammatory cascades, namely Wnt, Hedgehog and PPAR pathways, were downregulated. IPSE drove significant downregulation of major proinflammatory pathways including the IL-1β-TNFα-IL-6 pathways, interferon signaling, and reduction in oxidative stress. IPSE-NLS reduced inflammation but not oxidative stress. Taken together, we have identified signatures of acute-phase inflammation and oxidative stress in ifosfamide-injured bladder, which are reversed by pretreatment with IPSE. This work revealed several pathways that could be therapeutically targeted to prevent ifosfamide-induced hemorrhagic cystitis.

Modulation of Host Immunity by Helminths: The Expanding Repertoire of Parasite Effector Molecules

Helminths are extraordinarily successful parasites due to their ability to modulate the host immune response. They have evolved a spectrum of immunomodulatory molecules that are now beginning to be defined, heralding a molecular revolution in parasite immunology. These discoveries have the potential both to transform our understanding of parasite adaptation to the host and to develop possible therapies for immune-mediated disease. In this review we will summarize the current state of the art in parasite immunomodulation and discuss perspectives on future areas for research and discovery.

Schistosoma "Eggs-Iting" the Host: Granuloma Formation and Egg Excretion

Schistosomiasis is a major cause of morbidity in humans invoked by chronic infection with parasitic trematodes of the genus Schistosoma. Schistosomes have a complex life-cycle involving infections of an aquatic snail intermediate host and a definitive mammalian host. In humans, adult male and female worms lie within the vasculature. Here, they propagate and eggs are laid. These eggs must then be released from the host to continue the life cycle. Schistosoma mansoni and Schistosoma japonicum reside in the mesenteric circulation of the intestines with egg excreted in the feces. In contrast, S. haematobium are present in the venus plexus of the bladder, expelling eggs in the urine. In an impressive case of exploitation of the host immune system, this process of Schistosome “eggs-iting” the host is immune dependent. In this article, we review the formation of the egg granuloma and explore how S. mansoni eggs laid in vasculature must usurp immunity to induce regulated inflammation, to facilitate extravasation through the intestinal wall and to be expelled in the feces. We highlight the roles of immune cell populations, stromal factors, and egg secretions in the process of egg excretion to provide a comprehensive overview of the current state of knowledge regarding a vastly unexplored mechanism.

Schistosoma mansoni Egg-Released IPSE/alpha-1 Dampens Inflammatory Cytokine Responses via Basophil Interleukin (IL)-4 and IL-13

Schistosomes control inflammation in their hosts via highly effective mechanisms such as induction of Tregs, Bregs, and alternatively activated macrophages (AAMs). Notably, IPSE/alpha-1, the major secretory product from Schistosoma mansoni eggs, triggers basophils to release interleukin (IL)-4 and IL-13. Both cytokines are essential for AAM induction, suggesting an important role for IPSE/alpha-1 in inflammation control. Here, we show by in vitro co-culture experiments that IPSE/alpha-1-induced basophil IL-4/IL-13 inhibited pro-inflammatory cytokine release from human LPS-activated monocytes. This effect was cell/cell contact-independent but dependent on IL-4, since it was abrogated in the presence of anti-IL-4 antibodies. Importantly, the IPSE/alpha-1-induced IL-4/IL-13 release from basophils was amplified in the presence of LPS. Moreover, monocytes co-cultured in the presence of LPS with IPSE/alpha-1-stimulated basophils adopted an AAM-like phenotype as assessed by elevated expression of CD206 and CD209. The putative in vivo relevance of these findings was supported by immunohistological staining of S. mansoni-infected murine tissue revealing close physical contact between IPSE/alpha-1 and basophils in schistosome egg granulomas. Taken together, we found that IPSE/alpha-1 dampens inflammatory cytokine responses by triggering basophil IL-4/IL-13, in particular in the context of TLR activation, thereby turning inflammatory monocytes into anti-inflammatory AAMs. This might represent a mechanism used by schistosomes to control inflammation in the host.

Understanding Urogenital Schistosomiasis-Related Bladder Cancer: An Update

Infection with Schistosoma haematobium leads to urogenital schistosomiasis, which has been correlated with the occurrence of bladder cancer. However, mechanisms responsible for this association have not yet been clearly identified. In this short review, we provide an update, highlighting the most recent studies on schistosome-associated bladder cancer, including those that focus on identifying changes in host biology during S. haematobium infection, as well as studies for the identification of potentially pro-carcinogenic parasite molecules, and we offer a discussion on some possible mechanisms driving schistosomal bladder cancer.

Therapeutic exploitation of IPSE, a urogenital parasite-derived host modulatory protein, for chemotherapy-induced hemorrhagic cystitis

Chemotherapy-induced hemorrhagic cystitis (CHC) can be difficult to manage. Prior work suggests that IL-4 alleviates ifosfamide-induced hemorrhagic cystitis (IHC), but systemically administered IL-4 causes significant side effects. We hypothesized that the Schistosoma hematobium homolog of IL-4-inducing principle from Schistosoma mansoni eggs (H-IPSE), would reduce IHC and associated bladder pathology. IPSE binds IgE on basophils and mast cells, triggering IL-4 secretion by these cells. IPSE is also an “infiltrin,” translocating into the host nucleus to modulate gene transcription. Mice were administered IL-4, H-IPSE protein or its nuclear localization sequence (NLS) mutant, with or without neutralizing anti-IL-4 antibody, or 2-mercaptoethane sulfonate sodium (MESNA; a drug used to prevent IHC), followed by ifosfamide. Bladder tissue damage and hemoglobin content were measured. Spontaneous and evoked pain, urinary frequency, and bladdergene expression analysis were assessed. Pain behaviors were interpreted in a blinded fashion. One dose of H-IPSE was superior to MESNA and IL-4 in suppressing bladder hemorrhage in an IL-4-dependent fashion and comparable with MESNA in dampening ifosfamide-triggered pain behaviors in an NLS-dependent manner. H-IPSE also accelerated urothelial repair following IHC. Our work represents the first therapeutic exploitation of a uropathogen-derived host modulatory molecule in a clinically relevant bladder disease model and indicates that IPSE may be an alternative to MESNA for mitigating CHC.—Mbanefo, E. C., Le, L., Pennington, L. F., Odegaard, J. I., Jardetzky, T. S., Alouffi, A., Falcone, F. H., Hsieh, M. H. Therapeutic exploitation of IPSE, a urogenital parasite-derived host modulatory protein, for chemotherapy-induced hemorrhagic cystitis.

Exploring Structural and Physical Properties of Schistosome Eggs: Potential Pathways for Novel Diagnostics?

In this era of increasing demand for sensitive techniques to diagnose schistosomiasis, there is a need for an increased focus on the properties of the parasite eggs. The eggs are not only directly linked to the morbidity of chronic infection but are also potential key targets for accurate diagnostics. Eggs were the primary target of diagnostic tools in the past and we argue they could be the target of highly sensitive tools in the future if we focus on characteristics of their structure and shell surface that could be exploited for enhanced detection. In this review, we discuss the current state of knowledge of the physical structures of schistosome eggs and eggshells with a view to identifying pathways to a comprehensive understanding of their role in the host-parasite relationship and pathogenesis of infection, and pathways to new strategies for development of diagnostics.