Apoptotic cell identity induces distinct functional responses to IL-4 in efferocytic macrophages

Macrophages are functionally heterogeneous cells essential for apoptotic cell clearance. Apoptotic cells are defined by homogeneous characteristics, ignoring their original cell lineage identity. We found that in an interleukin-4 (IL-4)-enriched environment, the sensing of apoptotic neutrophils by macrophages triggered their tissue remodeling signature. Engulfment of apoptotic hepatocytes promoted a tolerogenic phenotype, whereas phagocytosis of T cells had little effect on IL-4-induced gene expression. In a mouse model of parasite-induced pathology, the transfer of macrophages conditioned with IL-4 and apoptotic neutrophils promoted parasitic egg clearance. Knockout of phagocytic receptors required for the uptake of apoptotic neutrophils and partially T cells, but not hepatocytes, exacerbated helminth infection. These findings suggest that the identity of apoptotic cells may contribute to the development of distinct IL-4-driven immune programs in macrophages.

Identification of Genomic Regions Implicated in Susceptibility to Schistosoma mansoni Infection in a Murine Backcross Genetic Model

Only a small number of infected people are highly susceptible to schistosomiasis, showing high levels of infection or severe liver fibrosis. The susceptibility to schistosome infection is influenced by genetic background. To assess the genetic basis of susceptibility and identify the chromosomal regions involved, a backcross strategy was employed to generate high variation in schistosomiasis susceptibility. This strategy involved crossing the resistant C57BL/6J mouse strain with the susceptible CBA/2J strain. The resulting F1 females (C57BL/6J × CBA/2J) were then backcrossed with CBA/2J males to generate the backcross (BX) cohort. The BX mice exhibited a range of phenotypes, with disease severity varying from mild to severe disease, lacking a fully resistant group. We observed four levels of infection intensity using cluster and principal component analyses and K-means based on parasitological, pathological, and immunological trait measurements. The mice were genotyped with 961 informative SNPs, leading to the identification of 19 new quantitative trait loci (QTL) associated with parasite burden, liver lesions, white blood cell populations, and antibody responses. Two QTLs located on chromosomes 15 and 18 were linked to the number of granulomas, liver lesions, and IgM levels. The corresponding syntenic human regions are located in chromosomes 8 and 18. None of the significant QTLs had been reported previously.

FMRF-NH2 -related neuropeptides in Biomphalaria spp., intermediate hosts for schistosomiasis: Precursor organization and immunohistochemical localization

Freshwater snails of the genus Biomphalaria serve as intermediate hosts for the digenetic trematode Schistosoma mansoni, the etiological agent for the most widespread form of intestinal schistosomiasis. As neuropeptide signaling in host snails can be altered by trematode infection, a neural transcriptomics approach was undertaken to identify peptide precursors in Biomphalaria glabrata, the major intermediate host for S. mansoni in the Western Hemisphere. Three transcripts that encode peptides belonging to the FMRF-NH2 -related peptide (FaRP) family were identified in B. glabrata. One transcript encoded a precursor polypeptide (Bgl-FaRP1; 292 amino acids) that included eight copies of the tetrapeptide FMRF-NH2 and single copies of FIRF-NH2 , FLRF-NH2 , and pQFYRI-NH2 . The second transcript encoded a precursor (Bgl-FaRP2; 347 amino acids) that comprised 14 copies of the heptapeptide GDPFLRF-NH2 and 1 copy of SKPYMRF-NH2 . The precursor encoded by the third transcript (Bgl-FaRP3; 287 amino acids) recapitulated Bgl-FaRP2 but lacked the full SKPYMRF-NH2 peptide. The three precursors shared a common signal peptide, suggesting a genomic organization described previously in gastropods. Immunohistochemical studies were performed on the nervous systems of B. glabrata and B. alexandrina, a major intermediate host for S. mansoni in Egypt. FMRF-NH2 -like immunoreactive (FMRF-NH2 -li) neurons were located in regions of the central nervous system associated with reproduction, feeding, and cardiorespiration. Antisera raised against non-FMRF-NH2 peptides present in the tetrapeptide and heptapeptide precursors labeled independent subsets of the FMRF-NH2 -li neurons. This study supports the participation of FMRF-NH2 -related neuropeptides in the regulation of vital physiological and behavioral systems that are altered by parasitism in Biomphalaria.

Epitope Mapping of Exposed Tegument and Alimentary Tract Proteins Identifies Putative Antigenic Targets of the Attenuated Schistosome Vaccine

The radiation-attenuated cercarial vaccine remains the gold standard for the induction of protective immunity against Schistosoma mansoni. Furthermore, the protection can be passively transferred to naïve recipient mice from multiply vaccinated donors, especially IFNgR KO mice. We have used such sera versus day 28 infection serum, to screen peptide arrays and identify likely epitopes that mediate the protection. The arrays encompassed 55 secreted or exposed proteins from the alimentary tract and tegument, the principal interfaces with the host bloodstream. The proteins were printed onto glass slides as overlapping 15mer peptides, reacted with primary and secondary antibodies, and reactive regions detected using an Agilent array scanner. Pep Slide Analyzer software provided a numerical value above background for each peptide from which an aggregate score could be derived for a putative epitope. The reactive regions of 26 proteins were mapped onto crystal structures using the CCP4 molecular graphics, to aid selection of peptides with the greatest accessibility and reactivity, prioritizing vaccine over infection serum. A further eight MEG proteins were mapped to regions conserved between family members. The result is a list of priority peptides from 44 proteins for further investigation in multiepitope vaccine constructs and as targets of monoclonal antibodies.

Association of IL-9, IL-10, and IL-17 Cytokines With Hepatic Fibrosis in Human Schistosoma mansoni Infection

This is a case series study to evaluate immunological markers associated with schistosomiasis advanced fibrosis, including 69 patients from an endemic area from the State of Sergipe and from the Hepatology Service of the University Hospital in Sergipe, Brazil. Hepatic fibrosis was classified based on Niamey protocol for ultrasonography (US). Immune response to Schistosoma mansoni antigens was evaluated by stimulating peripheral blood mononuclear cells (PBMCs) from these patients with either adult worm (SWAP-10 μg/ml) or egg (SEA-10 μg/ml) antigens or purified protein derivative of turberculin (PPD-10 μg/ml) or phytohemagglutinin (PHA-1 μg/ml) for 72 h. The levels of IFN-γ, TNF-α, IL-5, IL-10, and IL-17 were measured in these supernatants by ELISA and IL-9 by Luminex. Single nucleotide polymorphisms in IL-17, IL10, and CD209 genes were genotyped using TaqMan probe by qPCR. Higher levels of IL-9, IL-10, and IL-17 were found in PBMC supernatants of patients with advanced hepatic fibrosis. Direct correlations were detected between IL-9 and IL-17 levels with US spleen sizes, portal vein diameters, and periportal thickening. The CD209 rs2287886 AG polymorphism patients produce higher IL-17 levels. Together, these data suggest a role of these cytokines in the immunopathogenesis of advanced fibrosis in human schistosomiasis.

Association of IL-9, IL-10, and IL-17 Cytokines With Hepatic Fibrosis in Human Schistosoma mansoni Infection

This is a case series study to evaluate immunological markers associated with schistosomiasis advanced fibrosis, including 69 patients from an endemic area from the State of Sergipe and from the Hepatology Service of the University Hospital in Sergipe, Brazil. Hepatic fibrosis was classified based on Niamey protocol for ultrasonography (US). Immune response to Schistosoma mansoni antigens was evaluated by stimulating peripheral blood mononuclear cells (PBMCs) from these patients with either adult worm (SWAP-10 μg/ml) or egg (SEA-10 μg/ml) antigens or purified protein derivative of turberculin (PPD-10 μg/ml) or phytohemagglutinin (PHA-1 μg/ml) for 72 h. The levels of IFN-γ, TNF-α, IL-5, IL-10, and IL-17 were measured in these supernatants by ELISA and IL-9 by Luminex. Single nucleotide polymorphisms in IL-17, IL10, and CD209 genes were genotyped using TaqMan probe by qPCR. Higher levels of IL-9, IL-10, and IL-17 were found in PBMC supernatants of patients with advanced hepatic fibrosis. Direct correlations were detected between IL-9 and IL-17 levels with US spleen sizes, portal vein diameters, and periportal thickening. The CD209 rs2287886 AG polymorphism patients produce higher IL-17 levels. Together, these data suggest a role of these cytokines in the immunopathogenesis of advanced fibrosis in human schistosomiasis.

Schistosoma mansoni infection as a trigger to collapsing glomerulopathy in a patient with high-risk APOL1 genotype

Background

Schistosoma mansoni schistosomiasis (SM) remains a public health problem in Brazil. Renal involvement is classically manifested as a glomerulopathy, most often membranoproliferative glomerulonephritis or focal and segmental glomerulosclerosis. We report a case of collapsing glomerulopathy (CG) associated with SM and high-risk APOL1 genotype (HRG).

Case report

A 35-year-old male was admitted for hypertension and an eight-month history of lower-limb edema, foamy urine, and increased abdominal girth. He had a recent diagnosis of hepatosplenic SM, treated with praziquantel, without clinical improvement. Laboratory tests revealed serum creatinine 1.89mg/dL, blood urea nitrogen (BUN) 24mg/dL, albumin 1.9g/dL, cholesterol 531mg/dL, low-density lipoprotein 426mg/dL, platelets 115000/mm³, normal C3/C4, antinuclear antibody (ANA), rheumatoid factor (RF), and antineutrophil cytoplasmic antibodies (ANCA), negative serologies for hepatitis C virus (HCV) and human immunodeficiency virus (HIV), HBsAg negative and AntiHBc IgG positive, no hematuria or leukocyturia, 24 hour proteinuria 6.56g and negative serum and urinary immunofixation. Kidney biopsy established the diagnosis of CG. A treatment with prednisone was started without therapeutic response, progressing to end-stage kidney disease 19 months later. Molecular genetics investigation revealed an HRG.

Conclusions

This is the first report of CG associated with SM in the setting of an HRG. This case highlights the two-hit model as a mechanism for CG pathogenesis, where the high-risk APOL1 genotype exerts a susceptibility role and SM infection serves as a trigger to CG.

Schistosomiasis mansoni is still a public health problem in Brazil and renal involvement is described. In such cases, a glomerulopathy is the typical manifestation, most often membranoproliferative glomerulonephritis. In the current article, we report a patient with a recent diagnosis of hepatosplenic SM who was admitted for nephrotic syndrome associated with reduced renal function and hypertension. Kidney biopsy established the diagnosis of collapsing glomerulopathy (CG) and molecular genetics investigation identified a high-risk APOL1 genotype (HRG). Of note, HRG has been associated with increased risk to develop CG, and a two-hit model has been proposed for the genesis of this glomerulopathy. According to this model, a HRG represents the increased-susceptibility component, while an infection or other environmental factors could act as triggers for the development of CG. Based on those data and model, our case raises SM infection as a new trigger for this severe form of glomerulopathy. This is the first description of a case of CG associated with SM in a patient with an HRG. This case corroborates the interactive role between genetic and environmental factors in the pathogenesis of CG but also identifies SM infection as an additional trigger for its development.

EV-transported microRNAs of Schistosoma mansoni and Fasciola hepatica: Potential targets in definitive hosts

Trematodes are widespread parasitic flatworms that significantly affect mankind either directly as human parasites, or indirectly via the infection of livestock and the related economic damage. The two most important trematode taxa are the blood flukes Schistosoma and the liver flukes Fasciola, but detection and differentiation of these parasites remains a challenge. Recently, microRNAs (miRNAs) were described from extracellular vesicles (EV) for both parasites secreted into respective hosts. These molecules have been proposed as mediators of parasite-host communication, and potential biomarkers for the detection of parasitic infections from host blood. Our aim here was to study similarities and differences in the miRNA complements of Schistosoma mansoni and Fasciola hepatica, EV-load in particular, to predict their targets and potential functions in the parasite-host interaction. We reanalyzed the known miRNA complements of S. mansoni and F. hepatica and found 16 and 4 previously overlooked, but deeply conserved miRNAs, respectively, further moving their complements closer together. We found distinct miRNA enrichment patterns in EVs both showing high levels of flatworm miRNAs with potential for the detection of an infection from blood. Two miRNAs of the protostome specific MIR-71 and MIR-277 families were highly expressed in EVs and could, therefore, have potential as biomarkers for trematode infection. Curiously, we identified nucleotide differences in the sequence of Mir-277-P2 between S. mansoni and F. hepatica that hold great promise for the distinction of both parasites. To test whether the EV-miRNAs of S. mansoni and F. hepatica could be modulating the expression of host genes, we predicted miRNA targets in 321 human and cattle messenger RNAs that overlapped between both hosts. Of several predicted targets, wnt signaling pathway genes stood out and their suppression likely leads to changes in the glucose concentration in host blood and the reduction of inflammatory and immune responses.

Detection of Schistosoma mansoni-derived DNA in human urine samples by loop-mediated isothermal amplification (LAMP)

BACKGROUND

Schistosoma mansoni is the main species causing hepatic and intestinal schistosomiasis in Sub-Saharan Africa, and it is the only species in South America. Adult stages of the parasite reside in the mesenteric venous plexus of infected hosts, and eggs are shed in feces. Collecting patient stool samples for S. mansoni diagnostic purposes is difficult in large-scale field trials. Urine samples would be an alternative approach for molecular S. mansoni detection since they have several advantages over stool samples, including better handling, management and storage. Additionally, loop-mediated isothermal amplification (LAMP) technology is a powerful molecular diagnostic tool for infectious diseases, particularly under field conditions in developing countries. The present study aimed to assess the effectiveness of our previously developed LAMP assay (SmMIT-LAMP) for S. mansoni-specific detection in clinical urine samples.

METHODOLOGY/PRINCIPAL FINDINGS

The sensitivity of SmMIT-LAMP in urine was established in simulated fresh human urine samples artificially spiked with genomic DNA from S. mansoni. LAMP for 120 min instead of 60 min improved the sensitivity, reaching values of 0.01 fg/μL. A set of well-defined frozen stored human urine samples collected from Sub-Saharan immigrant patients was selected from a biobank to evaluate the diagnostic validity of SmMIT-LAMP. The set included urine samples from patients with microscopy-confirmed infections with S. mansoni, S. haematobium and other nonschistosome parasites, as well as urine samples from patients with microscopy-negative eosinophilia without a confirmed diagnosis. The SmMIT-LAMP was incubated for 60 and 120 min. A longer incubation time was shown to increase the LAMP-positive results in patient urine samples. We also tested urine samples from mice experimentally infected with S. mansoni, and LAMP-positive results were obtained from the third week after infection. A real-time LAMP assay was also performed with three individual urine samples.

CONCLUSIONS/SIGNIFICANCE

The SmMIT-LAMP could effectively detect S. mansoni DNA in mouse urine samples and produced promising results for human clinical samples. The detection of S. mansoni DNA in mouse urine samples from the third week after infection indicates that early diagnosis of active S. mansoni infection is possible using urine as a source of DNA. Further studies are still needed, but our method could be used as a promising molecular tool applicable to urine samples to diagnose human intestinal schistosomiasis caused by S. mansoni.

Methyl-CpG-binding (SmMBD2/3) and chromobox (SmCBX) proteins are required for neoblast proliferation and oviposition in the parasitic blood fluke Schistosoma mansoni

While schistosomiasis remains a significant health problem in low to middle income countries, it also represents a recently recognised threat to more economically-developed regions. Until a vaccine is developed, this neglected infectious disease is primarily controlled by praziquantel, a drug with a currently unknown mechanism of action. By further elucidating how Schistosoma molecular components cooperate to regulate parasite developmental processes, next generation targets will be identified. Here, we continue our studies on schistosome epigenetic participants and characterise the function of a DNA methylation reader, the Schistosoma mansoni methyl-CpG-binding domain protein (SmMBD2/3). Firstly, we demonstrate that SmMBD2/3 contains amino acid features essential for 5-methyl cytosine (5mC) binding and illustrate that adult schistosome nuclear extracts (females > males) contain this activity. We subsequently show that SmMBD2/3 translocates into nuclear compartments of transfected murine NIH-3T3 fibroblasts and recombinant SmMBD2/3 exhibits 5mC binding activity. Secondly, using a yeast-two hybrid (Y2H) screen, we show that SmMBD2/3 interacts with the chromo shadow domain (CSD) of an epigenetic adaptor, S. mansoni chromobox protein (SmCBX). Moreover, fluorescent in situ hybridisation (FISH) mediated co-localisation of Smmbd2/3 and Smcbx to mesenchymal cells as well as somatic- and reproductive- stem cells confirms the Y2H results and demonstrates that these interacting partners are ubiquitously expressed and found within both differentiated as well as proliferating cells. Finally, using RNA interference, we reveal that depletion of Smmbd2/3 or Smcbx in adult females leads to significant reductions (46-58%) in the number of proliferating somatic stem cells (PSCs or neoblasts) as well as in the quantity of in vitro laid eggs. Collectively, these results further expand upon the schistosome components involved in epigenetic processes and suggest that pharmacological inhibition of SmMBD2/3 and/or SmCBX biology could prove useful in the development of future schistosomiasis control strategies.

Dectin-1/2-induced autocrine PGE2 signaling licenses dendritic cells to prime Th2 responses

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.

T helper 2 (Th2) responses, which are initiated by dendritic cells (DCs), can cause allergic diseases, but they can also provide protection against metabolic disorders and parasitic helminth infections. As such, there is great interest in better understanding how their activity is induced and regulated by DCs. Parasitic helminths can potently induce Th2 responses. However, how helminths condition DCs for priming of Th2 responses remains incompletely understood. Here, we find that egg antigens from the parasitic helminth Schistosoma mansoni bind to pattern-recognition receptors (PRRs) Dectin-1 and Dectin-2 on DCs. This binding triggers a signaling cascade in DCs that results in synthesis of eicosanoid prostaglandin E2 (PGE₂). PGE₂ is sensed by the DCs themselves, resulting in expression of OX40 ligand (OX40L), which subsequently enables the DCs to promote Th2 differentiation. We show that this pathway is activated independently of omega-1 (ω-1), which is a glycoprotein secreted by the eggs and previously shown to condition DCs for priming of Th2 responses. Moreover, we demonstrate that this ω-1–independent pathway is crucial for Th2 induction and egg-driven immunopathology following S. mansoni infection in vivo. In summary, we identified a novel pathway in DCs involving Dectin-1/2–induced autocrine PGE₂ signaling through which Th2 responses are induced.

Schistosome egg antigens, including the glycoprotein IPSE/alpha-1, trigger the development of regulatory B cells

Infection with the helminth Schistosoma (S.) mansoni drives the development of interleukin (IL)-10-producing regulatory B (Breg) cells in mice and man, which have the capacity to reduce experimental allergic airway inflammation and are thus of high therapeutic interest. However, both the involved antigen and cellular mechanisms that drive Breg cell development remain to be elucidated. Therefore, we investigated whether S. mansoni soluble egg antigens (SEA) directly interact with B cells to enhance their regulatory potential, or act indirectly on B cells via SEA-modulated macrophage subsets. Intraperitoneal injections of S. mansoni eggs or SEA significantly upregulated IL-10 and CD86 expression by marginal zone B cells. Both B cells as well as macrophages of the splenic marginal zone efficiently bound SEA in vivo, but macrophages were dispensable for Breg cell induction as shown by macrophage depletion with clodronate liposomes. SEA was internalized into acidic cell compartments of B cells and induced a 3-fold increase of IL-10, which was dependent on endosomal acidification and was further enhanced by CD40 ligation. IPSE/alpha-1, one of the major antigens in SEA, was also capable of inducing IL-10 in naïve B cells, which was reproduced by tobacco plant-derived recombinant IPSE. Other major schistosomal antigens, omega-1 and kappa-5, had no effect. SEA depleted of IPSE/alpha-1 was still able to induce Breg cells indicating that SEA contains more Breg cell-inducing components. Importantly, SEA- and IPSE-induced Breg cells triggered regulatory T cell development in vitro. SEA and recombinant IPSE/alpha-1 also induced IL-10 production in human CD1d⁺ B cells. In conclusion, the mechanism of S. mansoni-induced Breg cell development involves a direct targeting of B cells by SEA components such as the secretory glycoprotein IPSE/alpha-1.

Infection with helminth parasites is known to be inversely associated with hyper-inflammatory disorders. While Schistosoma (S.) mansoni has been described to exert its down-modulatory effects on inflammation by inducing a network of regulatory immune cells such as regulatory B (Breg), the mechanisms of Breg cell induction remain unclear. Here, we use in vivo and in vitro approaches to show that antigens from S. mansoni eggs, among which the major glycoprotein IPSE/alpha-1, directly interact with splenic marginal zone B cells of mice which triggers them to produce the anti-inflammatory cytokine IL-10 and their capacity to induce regulatory T (Treg) cells. We also found that IPSE/alpha-1 induces IL-10 in human CD1d⁺ B cells, and that both natural and recombinant IPSE/alpha-1 are equally effective in driving murine and human Breg cells. Our study thus provides insight into the mechanisms of Breg cell induction by schistosomes, and an important step towards the development of helminth-based treatment strategies against hyper-inflammatory diseases.

Osteopontin Is Upregulated in Human and Murine Acute Schistosomiasis Mansoni

BACKGROUND

Symptomatic acute schistosomiasis mansoni is a systemic hypersensitivity reaction against the migrating schistosomula and mature eggs after a primary infection. The mechanisms involved in the pathogenesis of acute schistosomiasis are not fully elucidated. Osteopontin has been implicated in granulomatous reactions and in acute hepatic injury. Our aims were to evaluate if osteopontin plays a role in acute Schistosoma mansoni infection in both human and experimentally infected mice and if circulating OPN levels could be a novel biomarker of this infection.

METHODOLOGY/PRINCIPAL FINDINGS

Serum/plasma osteopontin levels were measured by ELISA in patients with acute (n = 28), hepatointestinal (n = 26), hepatosplenic (n = 39) schistosomiasis and in uninfected controls (n = 21). Liver osteopontin was assessed by immunohistochemistry in needle biopsies of 5 patients. Sera and hepatic osteopontin were quantified in the murine model of schistosomiasis mansoni during acute (7 and 8 weeks post infection, n = 10) and chronic (30 weeks post infection, n = 8) phase. Circulating osteopontin levels are increased in patients with acute schistosomiasis (p = 0.0001). The highest levels of OPN were observed during the peak of clinical symptoms (7-11 weeks post infection), returning to baseline level once the granulomas were modulated (>12 weeks post infection). The plasma levels in acute schistosomiasis were even higher than in hepatosplenic patients. The murine model mirrored the human disease. Macrophages were the major source of OPN in human and murine acute schistosomiasis, while the ductular reaction maintains OPN production in hepatosplenic disease. Soluble egg antigens from S. mansoni induced OPN expression in primary human kupffer cells.

CONCLUSIONS/SIGNIFICANCE

S. mansoni egg antigens induce the production of OPN by macrophages in the necrotic-exudative granulomas characteristic of acute schistosomiasis mansoni. Circulating OPN levels are upregulated in human and murine acute schistosomiasis and could be a non-invasive biomarker of this form of disease.

TPL-2 Regulates Macrophage Lipid Metabolism and M2 Differentiation to Control TH2-Mediated Immunopathology

Persistent T_H2 cytokine responses following chronic helminth infections can often lead to the development of tissue pathology and fibrotic scarring. Despite a good understanding of the cellular mechanisms involved in fibrogenesis, there are very few therapeutic options available, highlighting a significant medical need and gap in our understanding of the molecular mechanisms of T_H2-mediated immunopathology. In this study, we found that the Map3 kinase, TPL-2 (Map3k8; Cot) regulated T_H2-mediated intestinal, hepatic and pulmonary immunopathology following Schistosoma mansoni infection or S. mansoni egg injection. Elevated inflammation, T_H2 cell responses and exacerbated fibrosis in Map3k8^–/–mice was observed in mice with myeloid cell-specific (LysM) deletion of Map3k8, but not CD4 cell-specific deletion of Map3k8, indicating that TPL-2 regulated myeloid cell function to limit T_H2-mediated immunopathology. Transcriptional and metabolic assays of Map3k8^–/–M2 macrophages identified that TPL-2 was required for lipolysis, M2 macrophage activation and the expression of a variety of genes involved in immuno-regulatory and pro-fibrotic pathways. Taken together this study identified that TPL-2 regulated T_H2-mediated inflammation by supporting lipolysis and M2 macrophage activation, preventing T_H2 cell expansion and downstream immunopathology and fibrosis.

Chronic helminth infections can cause significant morbidity and organ damage in their definitive mammalian hosts. Managing this collateral damage can reduce morbidity and preserve vital tissues for normal organ function. One particular consequence of some chronic helminth infections is the deposition of fibrotic scar tissue, following immune responses directed towards helminth material. In this study we tested the role of a particular signalling kinase, TPL-2, and identified that it critically regulated the magnitude of fibrotic scarring following infection. Using several murine models with genetic deletions of TPL-2 in either all cells or specific deletion in subsets of immune cells (Map3k8^–/–Map3k8^fl/fl) we identified that expression of TPL-2 in myeloid cells was essential to prevent severe immune-mediated pathology. Using genome-wide analyses and metabolic assays, we discovered that TPL-2 was required for normal lipid metabolism and appropriate activation of myeloid cells / macrophages to limit fibrosis. These results revealed a previously unappreciated role for TPL-2 in preventing severe pathology following infection. Thus, activating this pathway may limit immune mediated pathology following chronic helminth infection. More broadly, this pathway is being targeted to treat inflammatory diseases and cancer [1, 2]. This study would suggest that caution should be taken to prevent untoward co-morbidities and fibrosis-related pathologies in patients when targeting TPL-2.

Human plasma lipid modulation in schistosomiasis mansoni depends on apolipoprotein E polymorphism

Background

Schistosomiasis mansoni is a parasitic liver disease, which causes several metabolic disturbances. Here, we evaluate the influence of Apolipoprotein E (APOE) gene polymorphism, a known modulator of lipid metabolism, on plasma lipid levels in patients with hepatosplenic schistosomiasis.

Methodology/Principal Findings

Blood samples were used for APOE genotyping and to measure total cholesterol (TC), LDL-C, HDL-C and triglycerides. Schistosomiasis patients had reduced TC, LDL-C and triglycerides (25%, 38% and 32% lower, respectively; P<0.0001) compared to control individuals, whereas HDL-C was increased (10% higher; P = 0.0136). Frequency of the common alleles, ε2, ε3 and ε4, was similar (P = 0.3568) between controls (n = 108) and patients (n = 84), implying that APOE genotype did not affect susceptibility to the advanced stage of schistosomiasis. Nevertheless, while patient TC and LDL-C levels were significantly reduced for each allele (except TC in ε2 patients), changes in HDL-C and triglycerides were noted only for the less common ε2 and ε4 alleles. The most striking finding, however, was that accepted regulation of plasma lipid levels by APOE genotype was disrupted by schistosomiasis. Thus, while ε2 controls had higher TC and LDL-C than ε3 carriers, these parameters were lower in ε2 versus ε3 patients. Similarly, the inverse relationship of TG levels in controls (ε2>ε3>ε4) was absent in patients (ε2 or ε4>ε3), and the increase in HDL-C of ε2 or ε4 patients compared to ε3 patients was not seen in the control groups.

Conclusion/Significance

We confirm that human schistosomiasis causes dyslipidemia and report for the first time that certain changes in plasma lipid and lipoprotein levels depend on APOE gene polymorphism. Importantly, we also concluded that S. mansoni disrupts the expected regulation of plasma lipids by the different ApoE isoforms. This finding suggests ways to identify new metabolic pathways affected by schistosomiasis and also potential molecular targets to treat associated morbidities.

miR-182 and miR-10a are key regulators of Treg specialisation and stability during Schistosome and Leishmania-associated inflammation

A diverse suite of effector immune responses provide protection against various pathogens. However, the array of effector responses must be immunologically regulated to limit pathogen- and immune-associated damage. CD4⁺Foxp3⁺ regulatory T cells (Treg) calibrate immune responses; however, how Treg cells adapt to control different effector responses is unclear. To investigate the molecular mechanism of Treg diversity we used whole genome expression profiling and next generation small RNA sequencing of Treg cells isolated from type-1 or type-2 inflamed tissue following Leishmania major or Schistosoma mansoni infection, respectively. In-silico analyses identified two miRNA “regulatory hubs” miR-10a and miR-182 as critical miRNAs in Th1- or Th2-associated Treg cells, respectively. Functionally and mechanistically, in-vitro and in-vivo systems identified that an IL-12/IFNγ axis regulated miR-10a and its putative transcription factor, Creb. Importantly, reduced miR-10a in Th1-associated Treg cells was critical for Treg function and controlled a suite of genes preventing IFNγ production. In contrast, IL-4 regulated miR-182 and cMaf in Th2-associed Treg cells, which mitigated IL-2 secretion, in part through repression of IL2-promoting genes. Together, this study indicates that CD4⁺Foxp3⁺ cells can be shaped by local environmental factors, which orchestrate distinct miRNA pathways preserving Treg stability and suppressor function.

The diversity of pathogens that the immune system encounters are controlled by a diverse suite of immunological effector responses. Preserving a well-controlled protective immune response is essential. Too vigorous an effector response can be as damaging as too little. Regulatory T cells (Treg) calibrate immune responses; however, how Treg cells adapt to control the diverse suite of effector responses is unclear. In this study we investigated the molecular identity of regulatory T cells that control distinct effector immune responses against two discrete pathogens, an intracellular parasitic protozoa, Leishmania major, and an extracellular helminth parasite, Schitsosoma mansoni. The two Treg populations studied were phenotypically and functionally different. We identified molecular pathways that influence this diversity and more specifically, we identified that two miRNAs (miR-182 and miR-10a) act as “regulatory hubs” critically controlling distinct properties within each Treg population. This is the first study identifying the upstream molecular pathways controlling Treg cell specialization and provides a new platform of Treg cell manipulation to fine-tune their function.

Early differential gene expression in haemocytes from resistant and susceptible Biomphalaria glabrata strains in response to Schistosoma mansoni

The outcome of infection in the host snail Biomphalaria glabrata with the digenean parasite Schistosoma mansoni is determined by the initial molecular interplay occurring between them. The mechanisms by which schistosomes evade snail immune recognition to ensure survival are not fully understood, but one possibility is that the snail internal defence system is manipulated by the schistosome enabling the parasite to establish infection. This study provides novel insights into the nature of schistosome resistance and susceptibility in B. glabrata at the transcriptomic level by simultaneously comparing gene expression in haemocytes from parasite-exposed and control groups of both schistosome-resistant and schistosome-susceptible strains, 2 h post exposure to S. mansoni miracidia, using an novel 5K cDNA microarray. Differences in gene expression, including those for immune/stress response, signal transduction and matrix/adhesion genes were identified between the two snail strains and tests for asymmetric distributions of gene function also identified immune-related gene expression in resistant snails, but not in susceptible. Gene set enrichment analysis revealed that genes involved in mitochondrial electron transport, ubiquinone biosynthesis and electron carrier activity were consistently up-regulated in resistant snails but down-regulated in susceptible. This supports the hypothesis that schistosome-resistant snails recognize schistosomes and mount an appropriate defence response, while in schistosome-susceptible snails the parasite suppresses this defence response, early in infection.

Upregulation of retinal dehydrogenase 2 in alternatively activated macrophages during retinoid-dependent type-2 immunity to helminth infection in mice

Although the vitamin A metabolite retinoic acid (RA) plays a critical role in immune function, RA synthesis during infection is poorly understood. Here, we show that retinal dehydrogenases (Raldh), required for the synthesis of RA, are induced during a retinoid-dependent type-2 immune response elicited by Schistosoma mansoni infection, but not during a retinoid-independent anti-viral immune response. Vitamin A deficient mice have a selective defect in T_H2 responses to S. mansoni, but retained normal LCMV specific T_H1 responses. A combination of in situ imaging, intra-vital imaging, and sort purification revealed that alternatively activated macrophages (AAMφ) express high levels of Raldh2 during S. mansoni infection. IL-4 induces Raldh2 expression in bone marrow-derived macrophages in vitro and peritoneal macrophages in vivo. Finally, in vivo derived AAMφ have an enhanced capacity to induce Foxp3 expression in CD4+ cells through an RA dependent mechanism, especially in combination with TGF-β. The regulation of Raldh enzymes during infection is pathogen specific and reflects differential requirements for RA during effector responses. Specifically, AAMφ are an inducible source of RA synthesis during helminth infections and T_H2 responses that may be important in regulating immune responses.

Vitamin A deficiency, a major global health concern, increases morbidity and death due to infectious diseases. For vitamin A to be utilized by the immune system, it must be metabolized into retinoic acid (RA), its active form. RA is a key determinant of T cell activity. However, its contribution to protective immunity during infection is poorly understood, as is the regulation of its synthesis in this context. We examined RA synthesis by immune cells responding to helminth infection and virus infection. While intestinal T cell responses were vitamin A-dependent during both infections, only T cell responses elicited by helminth infection were vitamin A-dependent in the liver. Consistent with this finding, the enzymes necessary for RA synthesis were expressed by inflammatory cells recruited to the liver during helminth, but not virus, infection. We identified alternatively-activated macrophages as a source of RA synthesis within immune cells responding to helminth infection and find that they can induce regulatory T cells. Our findings provide a better understanding of vitamin A utilization during infection and demonstrate that RA synthesis is an inducible component of protective immunity.

IL-10R blockade during chronic schistosomiasis mansoni results in the loss of B cells from the liver and the development of severe pulmonary disease

In schistosomiasis patients, parasite eggs trapped in hepatic sinusoids become foci for CD4+ T cell-orchestrated granulomatous cellular infiltrates. Since the immune response is unable to clear the infection, the liver is subjected to ongoing cycles of focal inflammation and healing that lead to vascular obstruction and tissue fibrosis. This is mitigated by regulatory mechanisms that develop over time and which minimize the inflammatory response to newly deposited eggs. Exploring changes in the hepatic inflammatory infiltrate over time in infected mice, we found an accumulation of schistosome egg antigen-specific IgG1-secreting plasma cells during chronic infection. This population was significantly diminished by blockade of the receptor for IL-10, a cytokine implicated in plasma cell development. Strikingly, IL-10R blockade precipitated the development of portal hypertension and the accumulation of parasite eggs in the lungs and heart. This did not reflect more aggressive Th2 cell responsiveness, increased hepatic fibrosis, or the emergence of Th1 or Th17 responses. Rather, a role for antibody in the prevention of severe disease was suggested by the finding that pulmonary involvement was also apparent in mice unable to secrete class switched antibody. A major effect of anti-IL-10R treatment was the loss of a myeloid population that stained positively for surface IgG1, and which exhibited characteristics of regulatory/anti-inflammatory macrophages. This finding suggests that antibody may promote protective effects within the liver through local interactions with macrophages. In summary, our data describe a role for IL-10-dependent B cell responses in the regulation of tissue damage during a chronic helminth infection.

Structural basis for inhibition of cathepsin B drug target from the human blood fluke, Schistosoma mansoni

Schistosomiasis caused by a parasitic blood fluke of the genus Schistosoma afflicts over 200 million people worldwide. Schistosoma mansoni cathepsin B1 (SmCB1) is a gut-associated peptidase that digests host blood proteins as a source of nutrients. It is under investigation as a drug target. To further this goal, we report three crystal structures of SmCB1 complexed with peptidomimetic inhibitors as follows: the epoxide CA074 at 1.3 Å resolution and the vinyl sulfones K11017 and K11777 at 1.8 and 2.5 Å resolutions, respectively. Interactions of the inhibitors with the subsites of the active-site cleft were evaluated by quantum chemical calculations. These data and inhibition profiling with a panel of vinyl sulfone derivatives identify key binding interactions and provide insight into the specificity of SmCB1 inhibition. Furthermore, hydrolysis profiling of SmCB1 using synthetic peptides and the natural substrate hemoglobin revealed that carboxydipeptidase activity predominates over endopeptidolysis, thereby demonstrating the contribution of the occluding loop that restricts access to the active-site cleft. Critically, the severity of phenotypes induced in the parasite by vinyl sulfone inhibitors correlated with enzyme inhibition, providing support that SmCB1 is a valuable drug target. The present structure and inhibitor interaction data provide a footing for the rational design of anti-schistosomal inhibitors.

IL-10 blocks the development of resistance to re-infection with Schistosoma mansoni

Despite effective chemotherapy to treat schistosome infections, re-infection rates are extremely high. Resistance to reinfection can develop, however it typically takes several years following numerous rounds of treatment and re-infection, and often develops in only a small cohort of individuals. Using a well-established and highly permissive mouse model, we investigated whether immunoregulatory mechanisms influence the development of resistance. Following Praziquantel (PZQ) treatment of S. mansoni infected mice we observed a significant and mixed anti-worm response, characterized by Th1, Th2 and Th17 responses. Despite the elevated anti-worm response in PBMC's, liver, spleen and mesenteric lymph nodes, this did not confer any protection from a secondary challenge infection. Because a significant increase in IL-10-producing CD4⁺CD44⁺CD25⁺GITR⁺ lymphocytes was observed, we hypothesised that IL-10 was obstructing the development of resistance. Blockade of IL-10 combined with PZQ treatment afforded a greater than 50% reduction in parasite establishment during reinfection, compared to PZQ treatment alone, indicating that IL-10 obstructs the development of acquired resistance. Markedly enhanced Th1, Th2 and Th17 responses, worm-specific IgG1, IgG2b and IgE and circulating eosinophils characterized the protection. This study demonstrates that blocking IL-10 signalling during PZQ treatment can facilitate the development of protective immunity and provide a highly effective strategy to protect against reinfection with S. mansoni.

Schistosomes are zoonotic parasitic helminths that infect hundreds of millions of people worldwide. Despite effective chemotherapy, schistosomiasis- the disease caused by these parasites, still plagues tropical regions of the world. This is due, in part, to poor resistance to reinfection resulting in high re-infection rates following treatment. This lack of resistance is intriguing, as effective treatment relies upon drug-induced parasite damage combined with host immune mediated killing. Furthermore, it has been widely reported that post-treatment, individuals develop and retain elevated levels of anti-parasite immune responses. We therefore asked why resistance to re-infection is so poor, despite the development of significant anti-worm responses post-treatment.

It is essential that immune responses are controlled by various immunosuppressive mechanisms to prevent immune-mediated pathologies. However, a robust immunoregulatory response may obstruct the development of protective immunity. Thus, a balanced immune response providing a non-pathogenic yet effective immune response may be required for the development of effective resistance to reinfection. Understanding the immunological mechanisms of resistance to re-infection and the role of effector and regulatory responses may aid in the development of more effective vaccines and treatment strategies for schistosomaisis. This study suggests that combining chemotherapy with drugs that block IL-10 might provide an improved strategy to elicit acquired immunity to this parasite.

Lack of galectin-3 disturbs mesenteric lymph node homeostasis and B cell niches in the course of Schistosoma mansoni infection

Galectin-3 is a β-galactoside-binding protein that has been shown to regulate pathophysiological processes, including cellular activation, differentiation and apoptosis. Recently, we showed that galectin-3 acts as a potent inhibitor of B cell differentiation into plasma cells. Here, we have investigated whether galectin-3 interferes with the lymphoid organization of B cell compartments in mesenteric lymph nodes (MLNs) during chronic schistosomiasis, using WT and galectin-3^-/- mice. Schistosoma mansoni synthesizes GalNAcβ1-4(Fucα1-3)GlcNAc(Lac-DiNAc) structures (N-acetylgalactosamine β1-4 N-acetylglucosamine), which are known to interact with galectin-3 and elicit an intense humoral response. Antigens derived from the eggs and adult worms are continuously drained to MLNs and induce a polyclonal B cell activation. In the present work, we observed that chronically-infected galectin-3^-/- mice exhibited a significant reduced amount of macrophages and B lymphocytes followed by drastic histological changes in B lymphocyte and plasma cell niches in the MLNs. The lack of galectin-3 favored an increase in the lymphoid follicle number, but made follicular cells more susceptible to apoptotic stimuli. There were an excessive quantity of apoptotic bodies, higher number of annexin V⁺/PI^- cells, and reduced clearance of follicular apoptotic cells in the course of schistosomiasis. Here, we observed that galectin-3 was expressed in non-lymphoid follicular cells and its absence was associated with severe damage to tissue architecture. Thus, we convey new information on the role of galectin-3 in regulation of histological events associated with B lymphocyte and plasma cell niches, apoptosis, phagocytosis and cell cycle properties in the MLNs of mice challenged with S.mansoni.

Multiple helminth infection of the skin causes lymphocyte hypo-responsiveness mediated by Th2 conditioning of dermal myeloid cells

Infection of the mammalian host by schistosome larvae occurs via the skin, although nothing is known about the development of immune responses to multiple exposures of schistosome larvae, and/or their excretory/secretory (E/S) products. Here, we show that multiple (4x) exposures, prior to the onset of egg laying by adult worms, modulate the skin immune response and induce CD4⁺ cell hypo-responsiveness in the draining lymph node, and even modulate the formation of hepatic egg-induced granulomas. Compared to mice exposed to a single infection (1x), dermal cells from multiply infected mice (4x), were less able to support lymph node cell proliferation. Analysis of dermal cells showed that the most abundant in 4x mice were eosinophils (F4/80⁺MHC-II⁻), but they did not impact the ability of antigen presenting cells (APC) to support lymphocyte proliferation to parasite antigen in vitro. However, two other cell populations from the dermal site of infection appear to have a critical role. The first comprises arginase-1⁺, Ym-1⁺ alternatively activated macrophage-like cells, and the second are functionally compromised MHC-II^hi cells. Through the administration of exogenous IL-12 to multiply infected mice, we show that these suppressive myeloid cell phenotypes form as a consequence of events in the skin, most notably an enrichment of IL-4 and IL-13, likely resulting from an influx of RELMα-expressing eosinophils. We further illustrate that the development of these suppressive dermal cells is dependent upon IL-4Rα signalling. The development of immune hypo-responsiveness to schistosome larvae and their effect on the subsequent response to the immunopathogenic egg is important in appreciating how immune responses to helminth infections are modulated by repeated exposure to the infective early stages of development.

Schistosomiasis is a major helminth disease that infects more than 200 million people in the tropics. Free-swimming aquatic cercariae infect through the skin after contact with contaminated water, and in endemic areas this can occur frequently. However, nothing is known about how multiple exposures affects innate immunity in the skin, and/or whether it impacts the acquired immune response. Consequently, we have developed an infection model in the mouse to examine the immune response to multiple infections prior to the production of eggs. We show that multiple exposures to schistosome larvae cause lymphocyte hypo-responsiveness, partly mediated by macrophages and dendritic cells from the skin which have a ‘down-regulated’ phenotype and are not able to act as efficient antigen presenting cells (APCs). These regulated APCs are conditioned amongst high levels of the cytokines IL-4 and IL-13 which follow an influx of abundant eosinophils. In the absence of the regulatory APCs, and in the absence of the common receptor chain for IL-4 and IL-13 (i.e. IL-4Rα), lymphocyte proliferation is restored. These findings are important in understanding how dermal immune responses are modulated so that we can devise new strategies for vaccine delivery, or the treatment of chronic inflammatory conditions of the skin.

Redundant and pathogenic roles for IL-22 in mycobacterial, protozoan, and helminth infections

IL-22 is a member of the IL-10 cytokine family and signals through a heterodimeric receptor composed of the common IL-10R2 subunit and the IL-22R subunit. IL-10 and IL-22 both activate the STAT3 signaling pathway; however, in contrast to IL-10, relatively little is known about IL-22 in the host response to infection. In this study, using IL-22(-/-) mice, neutralizing Abs to IL-22, or both, we show that IL-22 is dispensable for the development of immunity to the opportunistic pathogens Toxoplasma gondii and Mycobacterium avium when administered via the i.p. or i.v. route, respectively. IL-22 also played little to no role in aerosol infections with Mycobacterium tuberculosis and in granuloma formation and hepatic fibrosis following chronic percutaneous infections with the helminth parasite Schistosoma mansoni. A marked pathogenic role for IL-22 was, however, identified in toxoplasmosis when infections were established by the natural oral route. Anti-IL-22 Ab-treated mice developed significantly less intestinal pathology than control Ab-treated mice even though both groups displayed similar parasite burdens. The decreased gut pathology was associated with reduced IL-17A, IL-17F, TNF-alpha, and IFN-gamma expression. In contrast to the prior observations of IL-22 protective effects in the gut, these distinct findings with oral T. gondii infection demonstrate that IL-22 also has the potential to contribute to pathogenic inflammation in the intestine. The IL-22 pathway has emerged as a possible target for control of inflammation in certain autoimmune diseases. Our findings suggest that few if any infectious complications would be expected with the suppression of IL-22 signaling.

Suppression of mRNAs encoding tegument tetraspanins from Schistosoma mansoni results in impaired tegument turnover

Schistosomes express a family of integral membrane proteins, called tetraspanins (TSPs), in the outer surface membranes of the tegument. Two of these tetraspanins, Sm-TSP-1 and Sm-TSP-2, confer protection as vaccines in mice, and individuals who are naturally resistant to S. mansoni infection mount a strong IgG response to Sm-TSP-2. To determine their functions in the tegument of S. mansoni we used RNA interference to silence expression of Sm-tsp-1 and Sm-tsp-2 mRNAs. Soaking of parasites in Sm-tsp dsRNAs resulted in 61% (p = 0.009) and 74% (p = 0.009) reductions in Sm-tsp-1 and Sm-tsp-2 transcription levels, respectively, in adult worms, and 67%–75% (p = 0.011) and 69%–89% (p = 0.004) reductions in Sm-tsp-1 and Sm-tsp-2 transcription levels, respectively, in schistosomula compared to worms treated with irrelevant control (luciferase) dsRNA. Ultrastructural morphology of adult worms treated in vitro with Sm-tsp-2 dsRNA displayed a distinctly vacuolated and thinner tegument compared with controls. Schistosomula exposed in vitro to Sm-tsp-2 dsRNA had a significantly thinner and more vacuolated tegument, and morphology consistent with a failure of tegumentary invaginations to close. Injection of mice with schistosomula that had been electroporated with Sm-tsp-1 and Sm-tsp-2 dsRNAs resulted in 61% (p = 0.005) and 83% (p = 0.002) reductions in the numbers of parasites recovered from the mesenteries four weeks later when compared to dsRNA-treated controls. These results imply that tetraspanins play important structural roles impacting tegument development, maturation or stability.

Schistosomes, or blood flukes, reside in the blood vessels surrounding the liver and bowel of their human hosts. They infect 200 million people and kill many thousands each year in developing countries. The parasites cover themselves in a unique series of cell membranes called the tegument. Molecules in the tegument membranes are a major target for the development of new drugs and vaccines against the parasite. Here we show that at least one member of a family of tegument membrane proteins called tetraspanins, Sm-TSP-2, is integral to the proper formation of the tegument and subsequent survival of the parasite in its human host, providing a potential mechanism by which a vaccine based on Sm-TSP-2 protects immunized hosts.

Manipulation of the immune evasive properties of circulating cathodic antigen induces protective immunity against Schistosomiasis mansoni in C57BL/6 mice

Schistosome circulating cathodic antigen (CCA) has been hypothesized to take part in immune evasion mechanisms that protect against host's immunity. To dissect its immunogenicity, lymphoproliferative responses of splenocytes were assessed in C57BL/6 mice immunized with recombinant plasmid constructs expressing full-length and truncated fragments of CCA cDNA, before and after challenge infection with S. mansoni cercariae. Prior to challenge, splenocytes of immunized mice showed low responses to phytohaemagglutinin (PHA) and high responses to native CCA, compared to controls. After challenge, PHA-responses increased on day 3 through day 7 and subsequently declined. On the other hand, CCA-induced responses increased on day 3 post-challenge then declined in mice immunized with CCA fragments lacking the N-terminus (-N CCA). Whereas, mice immunized with full-length or CCA fragment lacking the C-terminus (-C CCA) showed a delayed increase of CCA-induced responses that maximize on day 25. Interestingly, animals immunized with -N CCA showed a significant reduction in worm burden between 42-51%, while, mice immunized with full-length or -C CCA showed lower protection levels of about 15 and 37%, respectively. These findings suggest that CCA may contain immunosuppressive epitopes on the N-terminus. Abrogation of these epitopes could disrupt the immune evasion mechanism orchestrated by CCA, which could aid the development of an alternative vaccination approach.

Susceptibility of two strains of mice to the infection with Schistosoma mansoni: parasitological and biochemical studies

In this article, two strains of mice BALB/C and C57 were infected with Egyptian strain of Schistosoma mansoni. BALB/C mice appeared to harbor fewer parasites than did C57 mice. The hepatic and intestinal tissues of C57 mice were loaded with more eggs than that of BALB/C mice. Regardless the strain of mice, the number of eggs per gram of liver tissues was higher than in the intestinal tissues. Some biochemical parameters were measured in the liver of infected and non-infected mice; a significant decrease in the activities of alkaline phosphatase, catalase, glutathione-s-transferase, glutathione, and total lipids of infected mice compared to their matched control were observed. However, there was a significant increase in malondialdehyde level of infected mice compared to their matched group. Detailed discussion on the parasitological and biochemical differences between the two strains was presented.

Cationic amino acid transporter-2 regulates immunity by modulating arginase activity

Cationic amino acid transporters (CAT) are important regulators of NOS2 and ARG1 activity because they regulate L-arginine availability. However, their role in the development of Th1/Th2 effector functions following infection has not been investigated. Here we dissect the function of CAT2 by studying two infectious disease models characterized by the development of polarized Th1 or Th2-type responses. We show that CAT2(-/-) mice are significantly more susceptible to the Th1-inducing pathogen Toxoplasma gondii. Although T. gondii infected CAT2(-/-) mice developed stronger IFN-gamma responses, nitric oxide (NO) production was significantly impaired, which contributed to their enhanced susceptibility. In contrast, CAT2(-/-) mice infected with the Th2-inducing pathogen Schistosoma mansoni displayed no change in susceptibility to infection, although they succumbed to schistosomiasis at an accelerated rate. Granuloma formation and fibrosis, pathological features regulated by Th2 cytokines, were also exacerbated even though their Th2 response was reduced. Finally, while IL-13 blockade was highly efficacious in wild-type mice, the development of fibrosis in CAT2(-/-) mice was largely IL-13-independent. Instead, the exacerbated pathology was associated with increased arginase activity in fibroblasts and alternatively activated macrophages, both in vitro and in vivo. Thus, by controlling NOS2 and arginase activity, CAT2 functions as a potent regulator of immunity.

Differential expression of collagen, MMP, TIMP and fibrogenic-cytokine genes in the granulomatous colon of Schistosoma mansoni-infected mice

Schistosomiasis mansoni is a major helminthic disease of the tropics characterised by chronic hepatic and intestinal granulomatous inflammation and fibrosis. The fibrotic response is regulated by the amount of collagen deposited in the tissues and the degradation of that collagen by matrix metalloproteinases (MMP). In the murine model of the disease, although hepatic granuloma formation and the ensuing fibrosis have been thoroughly examined, there is a dearth of information on the intestinal fibrotic process. The expression of fibrosis-related genes in the colons of chronically infected mice has therefore been investigated. Compared with that seen in uninfected mice, the expression of the genes coding for collagen of types I, III and IV was upregulated. Similarly, the messages for MMP-2, MMP-3 and MMP-8 were elevated, indicating the potential for collagen degradation. The genes for two tissue inhibitors of metalloproteinases (TIMP), TIMP-1 and TIMP-4, were, however, expressed at higher levels than those coding for the MMP. As a corollary, expression of the genes coding for three fibrogenic cytokines, transforming growth factor-beta, tumour necrosis factor and interleukin-4, was elevated. These data indicate that an imbalance in MMP:TIMP expression and enhanced levels of the messages for fibrogenic cytokines underlie the mechanism(s) of the colonic fibrosis seen in mice chronically infected with Schistosoma mansoni.

IL-31-IL-31R interactions negatively regulate type 2 inflammation in the lung

Interleukin (IL) 31Ralpha (glycoprotein 130-like monocyte receptor and glycoprotein 130-like receptor) heterodimerizes with oncostatin M receptor beta to bind IL-31, a cytokine expressed preferentially by CD4(+) T helper type 2 (Th2) cells. However, the functions of IL-31-IL-31R signaling in immune regulation remain unknown. Here, we identify a novel role for IL-31R in limiting type 2 inflammation in the lung. After intravenous injection of Schistosoma mansoni eggs, IL-31Ralpha(-/-) mice developed severe pulmonary inflammation, characterized by an increase in the area of granulomatous inflammation, increased numbers of resistin-like molecule alpha(+) cells, and enhanced collagen deposition compared to WT counterparts. In vitro, macrophages generated from IL-31Ralpha(-/-) mice promoted enhanced ovalbumin-specific CD4(+) T cell proliferation and purified naive CD4(+) T cells from IL-31Ralpha(-/-) mice exhibited enhanced proliferation and expression of Th2 cytokines, identifying a T cell- and macrophage-intrinsic regulatory function for IL-31R signaling. In contrast, the generation of CD4(+) T cell-mediated Th1 responses were normal in IL-31Ralpha(-/-) mice, suggesting that the regulatory role of IL-31R signaling is limited to type 2 responses. Together, these data implicate IL-31R signaling as a novel negative regulatory pathway that specifically limits type 2 inflammation.

Variation in expression of Biomphalaria glabrata SOD1: a potential controlling factor in susceptibility/resistance to Schistosoma mansoni

The snail Biomphalaria glabrata kills the blood fluke Schistosoma mansoni by a mechanism involving production of hydrogen peroxide, the enzymatic product of cytosolic Cu/Zn superoxide dismutase (SOD1). This enzyme exhibits higher activity in blood cells (hemocytes) from a predominantly resistant strain of B. glabrata than in hemocytes from a susceptible strain. Additionally, B. glabrata SOD1 polymorphisms have been associated with susceptibility/resistance to the parasite. To address the hypothesis that SOD1 transcription levels differ in accordance with variation at the SOD1 locus, quantitative PCR was performed using hemocyte-derived cDNA prepared from SOD1-genotyped snails. Here we report that individuals possessing the allele previously associated with resistance to S. mansoni express significantly higher levels of hemocyte SOD1 transcripts than individuals lacking this allele. A causal relationship between SOD1 expression and susceptibility/resistance to S. mansoni is supported by the correlation of transcript quantity with data (from a previous study) on the probability of infection.

CCR4 participation in Th type 1 (mycobacterial) and Th type 2 (schistosomal) anamnestic pulmonary granulomatous responses

CCR4 is purported to be a Th type 2 (Th2) cell-biased receptor but its functional role is unclear. Recent studies suggest that chemokine receptor expression and function are more complex in vivo and raise doubts regarding restricted CCR4 expression by Th2 cells. To address these issues, we analyzed the role of CCR4 in highly polarized models of Th type 1 (Th1) and Th2 cell-mediated pulmonary granulomas, respectively, elicited by i.v. challenge of primed mice with either mycobacterial purified protein derivative or schistosomal egg Ag-coated beads. CCR4 agonists were expressed during both responses, correlating with a shift of CCR4+ CD4+ T cells from blood to lungs. CCL22 dominated in draining nodes during the Th1 response. Analysis of CD4+ effector T cells revealed CCR4 expression and CCR4-mediated chemotaxis by both IFN-gamma and IL-4 producers. Studies of CCR4 knockout (CCR4(-/-)) mice showed partial impairment of the local type-2 cytokine response and surprisingly strong impairment of the Th1 response with abrogated IFN-gamma production during secondary but not primary challenge. Adoptive transfer indicated CCR4(-/-)CD4+ Th1 cell function was defective but this could not be reconstituted with wild-type (CCR4(+/+)) CD4+ T cells indicating involvement of another CCR4+ population. Coculture of CCR4(+/+)CD4+ T cells and CCR4(-/-) dendritic cells revealed intact IL-2 but impaired IFN-gamma production, pointing to a role for CCR4+ dendritic cells in effector cell expression. Therefore, CCR4 is not Th2-restricted and was required for sustenance and expression of the Th1 effector/memory response to mycobacterial Ags.

The host's genetic background determines the extent of angiogenesis induced by schistosome egg antigens

Schistosomiasis is characterised by periovular granuloma formation within the portal tract and presinusoidal venules. As inflammation wanes, continued attempts to wall off and repair hepatic injury, lead to the development of extensive fibrosis. The codependence of chronic inflammation and angiogenesis is a well-known phenomenon. Neovascularisation is a complex process of endothelial cell proliferation and remodelling of the extracellular matrix. Previous studies demonstrated the ability of schistosome soluble egg antigens (SEAs) to stimulate endothelial cell activation in vitro. In the present study, we investigated the angiogenic potential of SEA in Swiss and BALb/c mice, after infection with Schistosoma mansoni or S. haematobium and by implanting SEA-coated beads into the murine liver. Anti-CD34 and anti-Ki-67 immunohistochemical stainings demonstrated newly formed blood vessels within and at the periphery of the granulomas. However, in one third of the granulomas the pre-existing portal stroma was not destroyed by the granulomatous inflammation, angiogenesis was minimal or absent and further growth of the granuloma was prevented. In C57BL/6J and C3H/HeN inbred mice, this polarisation was even more pronounced. In 91% of the granulomas in C57BL6/J mice the portal stroma was preserved. These mice had significantly smaller granulomas, less fibrosis and less mortality as compared to the high pathology C3H/HeN mice, where 87% of the granulomas were of the angiogenic type with destruction of the pre-existing stroma, leading to more severe chronic pathology. Thus, host's genetic mechanisms regulating the degree of angiogenesis and fibrosis, determine the severity of schistosome-induced pathology.

Interleukin-5 does not influence differential transcription of transmembrane and soluble isoforms of IL-5R alpha in vivo

Interleukin-5 (IL-5) promotes signal transduction and expansion of eosinophil colonies in bone marrow via interactions with its heterodimeric receptor (IL-5R). Two variants encoding soluble forms of the alpha subunit (sIL-5R alpha) have been described, although the signals promoting and/or limiting differential transcription remain to be clarified.

OBJECTIVES

Our intent was to explore the role of IL-5 in regulating differential transcription of these splice variants in vivo.

METHODS

We have designed a quantitative reverse transcriptase-polymerase chain reaction assay to detect transcripts encoding the transmembrane, soluble 1 and 2 forms of IL-5R alpha in two strains of wild-type (BALB/c and C57BL/6) and corresponding IL-5 gene-deleted mice. Wild-type mice respond to S. mansoni infection with a gradual increase in serum IL-5 and eosinophilia, which is not observed in IL-5 gene-deleted mice.

RESULTS AND CONCLUSIONS

We find that IL-5 is not necessary for differential splicing to occur in vivo, as all three forms of the IL-5R alpha are detected in both strains of IL-5 gene-deleted mice, with ratios of transcript expression (transmembrane : soluble 1 : soluble 2) that were indistinguishable from their wild-type counterparts. Differential splicing does vary markedly between strains, potentially because of local effects of strain-specific polymorphisms.

Lack of antigen-specific Th1 response alters granuloma formation and composition in Schistosoma mansoni-infected MyD88-/- mice

To evaluate the role of the innate immune system during schistosomiasis in vivo, we infected myeloid differentiation factor 88 (MyD88)-deficient mice with Schistosoma mansoni and analyzed their pathognomonic formation of hepatic granulomas and T cell responses. Even though the differences between knockout and wild-type mice in terms of mortality, liver damage, serum IgE and parasite burden were insignificant, the liver granulomas in the MyD88-deficient mice were significantly smaller, less cellular and contained a reduced percentage of eosinophils. Histologically, these granulomas revealed stronger fibrosis, confirmed also by increased levels of soluble collagen and IL-13, implying a Th2 bias. Spleen cells from infected MyD88-deficient mice also produced significantly less IFN-gamma than their wild-type controls upon restimulation with Schistosoma-egg-antigen (SEA). Furthermore, SEA-loaded APC from naive wild-type or MyD88-deficient mice induced equal amounts of proliferation and cytokine secretion by T cells from wild-type infected mice. In contrast, Ag-specific T cells from infected MyD88-deficient mice produced hardly any IFN-gamma but considerably more IL-10, again regardless of the APC type. These findings indicate that the loss of IFN-gamma production is not due to impaired antigen presentation but may perhaps is due to suppression by IL-10-producing T cells. Thus, MyD88 plays an important role in cellular infiltration, granuloma composition and T cell responses during schistosomiasis.

Manganese superoxide dismutase from Biomphalaria glabrata

The investigation of the response of Biomphalaria glabrata snails to Echinostoma paraensei (digenea) at 2 days post-exposure by suppression subtractive hybridization yielded a partial sequence of the anti-oxidant enzyme manganese superoxide dismutase (MnSOD). Full-length MnSOD (669nt) from M line and BS-90 strains of B. glabrata differed by one synonymous nucleotide replacement. B. glabrata has 1-4 MnSOD loci (Southern hybridization). Both snail strains expressed MnSOD at equal baseline levels (quantitative PCR). Susceptible snails increased expression of MnSOD following infection with E. paraensei or Schistosoma mansoni, and expression was reduced in the incompatible combination (BS-90 B. glabrata and S. mansoni). Thus, MnSOD did not determine resistance or susceptibility for these parasites, but expression of MnSOD is consistent with its involvement in a stress response of B. glabrata.

Schistosomal hepatic fibrosis and the interferon gamma receptor: a linkage analysis using single-nucleotide polymorphic markers

A minority of individuals infected with the parasite Schistosoma mansoni develops hepatic fibrosis. HLA studies in Egypt and a candidate gene search in a Sudanese population indicate that the host's genetics contribute to disease susceptibility. In an Egyptian community, 32.7% of individuals 11 years and older had significant fibrosis by WHO ultrasound criteria. Linkage to 10 candidate genes was tested using 89 affected sibling pairs from 40 pedigrees in this community. The candidates included genes that initiate fibrosis, participate in collagen synthesis, or control collagen degradation. Two to four single-nucleotide polymorphisms (SNPs) were genotyped per locus, and 188 individuals were genotyped at 48 markers. Model-free modified Haseman-Elston analysis identified linkage to a SNP in the interferon gamma receptor locus (P=0.000001). There was also weak evidence for linkage to the interleukin 13-4 region and tissue growth factor beta 1.

Characterization of the divergent eosinophil ribonuclease, mEar 6, and its expression in response to Schistosoma mansoni infection in vivo

The eosinophil-associated ribonucleases (Ears) are rapidly evolving proteins found in multigene clusters that are unique to each rodent species. Of the 15 independent genes in the Mus musculus cluster, only mEars 1 and 2 are expressed at significant levels at homeostasis. Here we characterize the expression of mEar 6 in the liver and spleen in mice in response to infection with the helminthic parasite, Schistosoma mansoni. Interestingly, expression of mEar 6 is not directly related to the elevated levels of serum IL-5 or tissue eosinophilia characteristic of this disease, as no mEar 6 transcripts were detected in the liver or the spleen from uninfected IL-5-transgenic mice. The coding sequence of mEar 6 has diverged under positive selection pressure (K(a)/K(s) > 1.0) and has a unique unpaired cysteine near the carboxy-terminus of the protein. The high catalytic efficiency of recombinant mEar 6 (k(cat)/K(m) = 0.9 x 10(6)/M/s) is similar to that of the cluster's closest human ortholog, eosinophil-derived neurotoxin (EDN/RNase 2). In summary, we have identified mEar 6 as one of only two RNase A superfamily ribonucleases known to be expressed specifically in response to pathophysiologic stress in vivo.

Helminth infection protects mice from anaphylaxis via IL-10-producing B cells

Modulation of the immune system by infection with helminth parasites, including schistosomes, is proposed to reduce the levels of allergic responses in infected individuals. In this study we investigated whether experimental infection with Schistosoma mansoni could alter the susceptibility of mice to an extreme allergic response, anaphylaxis. We formally demonstrate that S. mansoni infection protects mice from an experimental model of systemic fatal anaphylaxis. The worm stage of infection is shown to mediate this protective effect. In vivo depletion studies demonstrated an imperative role for B cells and IL-10 in worm-mediated protection. Furthermore, worm infection of mice increases the frequency of IL-10-producing B cells compared with that in uninfected mice. However, transfer of B cells from worm-infected mice or in vitro worm-modulated B cells to sensitized recipients exacerbated anaphylaxis, which was attributed to the presence of elevated levels of IL-4-producing B cells. Worm-modulated, IL-10-producing B cells from IL-4-deficient, but not IL-5-, IL-9- or IL-13-deficient, mice conferred complete resistance to anaphylaxis when transferred to naive mice. Therefore, we have dissected a novel immunomodulatory mechanism induced by S. mansoni worms that is dependent on an IL-10-producing B cell population that can protect against allergic hypersensitivity. These data support a role for helminth immune modulation in the hygiene hypothesis and further illustrate the delicate balance between parasite induction of protective regulatory (IL-10) responses and detrimental (IL-4) allergic responses.

Dynamics of collagen, MMP and TIMP gene expression during the granulomatous, fibrotic process induced by Schistosoma mansoni eggs

In schistosomiasis mansoni, granulomatous inflammation and fibrotic resolution are the major pathogenetic factors. The outcome of fibrosis is influenced by the deposition of collagen and degradation mediated by matrix metalloproteinases (MMP). There is a dearth of data on the expression of MMP and the tissue inhibitors of metalloproteinase (TIMP) during the fibrosis associated with schistosomiasis. In this study, the dynamics of collagen, MMP and TIMP gene expression were analysed during murine Schistosoma mansoni infection. Expression within the granulomatous liver tissue of the genes coding for collagen of types I, III and IV was up-regulated at the onset of granuloma development, and the dominant type-I expression peaked at the chronic, fibrotic stage. The amount of deposited hepatic collagen increased with the chronicity of the infection, indicating cumulative fibrosis. Collagenase, gelatinase, stromelysin, matrilysin-specific gene activities were similarly up-regulated, but only MMP-8 (collagenase-2) expression peaked at the height of fibrosis. TIMP-1 gene expression gradually increased during the course of the disease and, along with TIMP-2, peaked at the chronic, fibrotic stage. Granuloma myofibroblasts expressed both MMP and TIMP-1 genes. In ELISA of the splenic cytokines, high levels of fibrogenic interleukin-13 and moderate production of transforming growth factor-beta were found to be concurrent with fibrosis. These data indicate that an imbalance in MMP:TIMP expression and fibrogenic cytokine production are associated with cumulative fibrosis.

IL-13 activates a mechanism of tissue fibrosis that is completely TGF-beta independent

Fibrosis is a characteristic feature in the pathogenesis of a wide spectrum of diseases. Recently, it was suggested that IL-13-dependent fibrosis develops through a TGF-beta1 and matrix metalloproteinase-9-dependent (MMP-9) mechanism. However, the significance of this pathway in a natural disorder of fibrosis was not investigated. In this study, we examined the role of TGF-beta in IL-13-dependent liver fibrosis caused by Schistosoma mansoni infection. Infected IL-13-/- mice showed an almost complete abrogation of fibrosis despite continued and undiminished production of TGF-beta1. Although MMP-9 activity was implicated in the IL-13 pathway, MMP-9-/- mice displayed no reduction in fibrosis, even when chronically infected. To directly test the requirement for TGF-beta, studies were also performed with neutralizing anti-TGF-beta Abs, soluble antagonists (soluble TGF-betaR-Fc), and Tg mice (Smad3-/- and TGF-betaRII-Fc Tg) that have disruptions in all or part of the TGF-beta signaling cascade. In all cases, fibrosis developed normally and with kinetics similar to wild-type mice. Production of IL-13 was also unaffected. Finally, several genes, including interstitial collagens, several MMPs, and tissue inhibitors of metalloprotease-1 were up-regulated in TGF-beta1-/- mice by IL-13, demonstrating that IL-13 activates the fibrogenic machinery directly. Together, these studies provide unequivocal evidence of a pathway of fibrogenesis that is IL-13 dependent but TGF-beta1 independent, illustrating the importance of targeting IL-13 directly in the treatment of infection-induced fibrosis.

The pathogenesis of schistosomiasis is controlled by cooperating IL-10-producing innate effector and regulatory T cells

IL-10 reduces immunopathology in many persistent infections, yet the contribution of IL-10 from distinct cellular sources remains poorly defined. We generated IL-10/recombination-activating gene (RAG)2-deficient mice and dissected the role of T cell- and non-T cell-derived IL-10 in schistosomiasis by performing adoptive transfers. In this study, we show that IL-10 is generated by both the innate and adaptive immune response following infection, with both sources regulating the development of type-2 immunity, immune-mediated pathology, and survival of the infected host. Importantly, most of the CD4(+) T cell-produced IL-10 was confined to a subset of T cells expressing CD25. These cells were isolated from egg-induced granulomas and exhibited potent suppressive activity in vitro. Nevertheless, when naive, naturally occurring CD4(+)CD25(+) cells were depleted in adoptive transfers, recipient IL-10/RAG2-deficient animals were more susceptible than RAG2-deficient mice, confirming an additional host-protective role for non-T cell-derived IL-10. Thus, innate effectors and regulatory T cells producing IL-10 cooperate to reduce morbidity and prolong survival in schistosomiasis.

IFN-gamma polymorphisms (IFN-gamma +2109 and IFN-gamma +3810) are associated with severe hepatic fibrosis in human hepatic schistosomiasis (Schistosoma mansoni)

Schistosome infection is a major public health concern affecting millions of people living in tropical regions of Africa, Asia, and South America. Schistosomes cause mild clinical symptoms in most subjects, whereas a small proportion of individuals presents severe clinical disease (as periportal fibrosis (PPF)) that may lead to death. Severe PPF results from an abnormal deposition of extracellular matrix proteins in the periportal spaces due to a chronic inflammation triggered by eggs and schistosome Ags. Extracellular matrix protein production is regulated by a number of cytokines, including IFN-gamma. We have now screened putative polymorphic sites within this gene in a population living in an endemic area for Schistosoma mansoni. Two polymorphisms located in the third intron of the IFN-gamma gene are associated with PPF. The IFN-gamma +2109 A/G polymorphism is associated with a higher risk for developing PPF, whereas the IFN-gamma +3810 G/A polymorphism is associated with less PPF. The polymorphisms result in changes in nuclear protein interactions with the intronic regions of the gene, suggesting that they may modify IFN-gamma mRNA expression. These results are consistent with the results of previous studies. Indeed, PPF is controlled by a major locus located on chromosome 6q22-q23, closely linked to the gene encoding the alpha-chain of the IFN-gamma receptor, and low IFN-gamma producers have been shown to have an increased risk of severe PPF. Together, these observations support the view that IFN-gamma expression and subsequent signal transduction play a critical role in the control of PPF in human hepatic schistosome infection (S. mansoni).

Global gene expression profiles during acute pathogen-induced pulmonary inflammation reveal divergent roles for Th1 and Th2 responses in tissue repair

T helper 1 responses are typically proinflammatory, while Th2 responses have been considered regulatory. Interestingly, Th2 responses characterize a number of pulmonary diseases, many of which terminate in tissue remodeling and fibrosis. We developed a mouse model using Schistosoma mansoni eggs and cytokine-deficient mice to induce highly polarized Th1- or Th2-type inflammation in the lung. In this study, we examined the pathology and cytokine profiles in Th1- and Th2-polarized environments and used oligonucleotide microarray analysis to decipher the genes responsible for these effects. We further elaborated on the results using IL-10- and IL-13-deficient mice because these cytokines are believed to be the central regulators of Th2-associated pathology. We found that the Th1-polarized mice developed small granulomas with less fibrosis while expressing genes characteristic of tissue damage. Th2-polarized mice, in contrast, formed large granulomas with massive collagen deposition and up-regulated genes associated with wound healing, specifically, arginase, collagens, matrix metalloproteinases (MMPs), and tissue inhibitors of MMP. In addition, several members of the chitinase-like family were up-regulated in the lung following egg challenge. We also developed a method of defining the net collagen deposition using the expression profiles of several collagen, MMP, and tissue inhibitors of MMP genes. We found that Th1-polarized mice did not elaborate collagens or MMPs and therefore did not have a significant capacity for repair in this model. Thus, Th1-mediated inflammation is characterized by tissue damage, while Th2 directs wound healing and fibrosis.

Protection against Schistosoma mansoni utilizing DNA vaccination with genes encoding Cu/Zn cytosolic superoxide dismutase, signal peptide-containing superoxide dismutase and glutathione peroxidase enzymes

Protection against Schistosoma mansoni infection in C57BL/6 female mice was evaluated by two DNA vaccination strategies. Mice were either vaccinated by intramuscular injection with pcDNAI/Amp constructs encoding either Cu/Zn cytosolic superoxide dismutase (CT-SOD), signal peptide-containing SOD (SP-SOD), glutathione peroxidase (GPX(bb)) or a mutated form of GPX (GPX(m)), or primed with naked DNA constructs and boosted with recombinant vaccinia virus (RVV) containing the same genes. Animals were then challenged with S. mansoni and the level of protection was assessed as the reduction in worm burden. CT-SOD showed significant levels of protection compared to the control group, ranging between 44 and 60%, while SP-SOD exhibited from 22 to 45%. GPX(bb) showed levels of protection (23-55%) higher than GPX(m) (25-34%). The prime-boost strategy gave the same results as naked DNA or recombinant vaccinia virus alone except in the case of GPX, where the protection was 85%.

Existence of host DNA sequences in schistosomes—horizontal and vertical transmission

The localization of repetitive DNA sequences in the mouse genome such as mouse type 2 Alu sequence (B2) and mouse retrovirus-related sequences was shown in the body of adult Schistosoma japonicum and Schistosoma mansoni by applying an in situ PCR and hybridization technique. Using the same method, mouse major histocompatibility complex (MHC) class I sequence was also found in schistosomes. Furthermore, mouse MHC class I sequence and type A retroviral sequence were detected in S. japonicum and S. mansoni cercarial DNA by blot hybridization. These findings indicated that horizontal and vertical transmission of host DNA sequences occurred in schistosomes. The incorporation and propagation of host sequences in schistosomes and the roles played by such host sequences form the focus of this brief review.

No evidence for a major effect of tumor necrosis factor alpha gene polymorphisms in periportal fibrosis caused by Schistosoma mansoni infection

Hepatic periportal fibrosis (PPF), associated with portal hypertension, is a major pathological consequence of infections with Schistosoma mansoni and Schistosoma japonicum. Indeed, affected subjects may die from portal hypertension. Previous studies have indicated that tumor necrosis factor alpha (TNF-alpha) may aggravate fibrosis. We therefore investigated whether PPF was associated with certain polymorphisms of the TNF-alpha gene. Four polymorphisms (TNF-alpha -376 G/A, -308 G/A, -238 G/A, and +488 G/A) were investigated in two Sudanese populations living in an area in which S. mansoni is endemic. These polymorphisms were analyzed for 105 Sudanese subjects with various grades of PPF, from mild to advanced; all subjects were from two neighboring villages (Taweela and Umzukra). They were then analyzed for 70 subjects with advanced liver disease and for 345 matched controls from the Gezira region. We found no evidence of associations between these four polymorphisms and PPF in both of these studies. Thus, these four polymorphisms, two of which (TNF-alpha -376 and -308) were found to increase TNF-alpha gene transcription, are unlikely to have a major effect on PPF progression in these populations. However, this result does not exclude the possibility that these polymorphisms have a minor effect on PPF development.

Gene microarray analysis reveals interleukin-5-dependent transcriptional targets in mouse bone marrow

Interleukin-5 (IL-5) is a hematopoietic differentiation factor that promotes the development of mature eosinophils from progenitors in bone marrow. We present a multifactorial microarray study documenting the transcriptional events in bone marrow of wild-type and IL-5-deficient mice at baseline and in response to infection with Schistosoma mansoni. The microarray data were analyzed by a 4-way subtractive algorithm that eliminated confounding non-IL-5-related sequelae of schistosome infection as well as alterations in gene expression among uninfected mice. Among the most prominent findings, we observed 7- to 40-fold increased expression of transcripts encoding the classic eosinophil granule proteins (eosinophil peroxidase, major basic protein, the ribonucleases) together with arachidonate-15-lipoxygenase and protease inhibitor plasminogen activator inhibitor 2 (PAI-2), in the IL-5-producing, infected wild-type mice only. This was accompanied by increased transcription of genes involved in secretory protein biosynthesis and granule-vesicle formation. Interestingly, we did not detect increased expression of genes encoding eosinophil-related chemokine receptors (CCR1, CCR3) or members of the GATA or CCAAT/enhancer binding protein (C/EBP) transcription factor families. These data suggest that the IL-5-responsive progenitors in the mouse bone marrow are already significantly committed to the eosinophil lineage and that IL-5 promotes differentiation of these committed progenitors into cells with recognizable and characteristic cytoplasmic granules and granule proteins.