Temporal expression of chemokines dictates the hepatic inflammatory infiltrate in a murine model of schistosomiasis

Plasma levels of growth-related oncogene (CXCL1-3) associated with fibrosis and platelet counts in HCV-infected patients

BACKGROUND

Fibrosis progression in hepatitis C virus (HCV)-infected patients varies greatly between individuals. Chemokines recruit immune cells to the infected liver and may thus play a role in the fibrosis process.

AIM

To investigate plasma levels of a diverse chemokine panel in relation to liver fibrosis.

METHODS

African-American and Caucasian HCV genotype 1 infected patients were treated with peginterferon (pegIFN) and ribavirin (RBV) for 48 weeks (VIRAHEP-C cohort). Plasma levels of 13 cytokines were studied at baseline (n = 386). Subsequently, GROα levels were assessed in a sub cohort (n = 99) at baseline, and at 4 and 12 weeks after start of pegIFN/RBV treatment.

RESULTS

Increased severity of fibrosis (Ishak fibrosis score 0-2 vs. 3-6) was associated with increased plasma IP-10 (CXCL10) and IL-8 (CXCL8) levels, and decreased plasma levels of the chemokine growth-related oncogene (GRO, CXCL1-3). Plasma GRO levels were also positively correlated with platelet counts, and were higher in African-American as compared to Caucasian patients. In response to pegIFN/RBV treatment, GROα levels increased in Caucasian but not African-American patients from week 4 onwards.

CONCLUSIONS

The association with severity of fibrosis and platelet count positions plasma GRO as a potential biomarker for liver fibrosis in HCV-infected patients. The secretion of GRO by platelets may explain the correlation between GRO plasma level and platelet count. The ethnic difference in GRO levels both pre-treatment and in response to pegIFN/RBV might be driven by a genetic polymorphism in GROα associated with higher plasma levels and more common in the African-American population.

Mitochondrial dynamics in the mouse liver infected by Schistosoma mansoni

Mitochondrial dynamics is crucial for regulation of cell homeostasis. Schistosoma mansoni is one of the most common parasites known to cause liver disease. Mice infected by S. mansoni show acute symptoms of schistosomiasis after 8 weeks. Hence, in this study, we attempted to assess the direct effects of S. mansoni infection on mice liver, and to explore the expression of mitochondrial morphology, dynamics, and function. Our recent findings show that S. mansoni infection changes mitochondrial morphology and affects mitochondrial functions, which attenuates mitochondrial membrane potential and ATP generation. S. mansoni-infected mice increases mitochondrial numbers by upregulating of genes involved in mitochondrial biogenesis, including peroxisome proliferator-activated receptor c co-activator 1α (PGC1α) and mitochondrial transcription factor A (Tfam). This may promote mitochondria generation for accelerating the recovery of mitochondrial functions. Moreover, S. mansoni would disrupt mitochondrial dynamics including induced mitochondrial fission and promoted mitochondrial fragmentation in mice liver. More importantly, S. mansoni further stimulated upregulation both extrinsic and intrinsic apoptosis pathway in infected mice liver. The intrinsic pathway was triggered by cytochrome c release. Additionally, NFκB (nuclear factor-kappa B, p65) could play a protective role to inhibit apoptosis through reducing active caspase-3 expression. Therefore, our results confirmed the liver damage mechanism of experimental schistosomiasis in mice model.

Circulating miRNAs: Potential Novel Biomarkers for Hepatopathology Progression and Diagnosis of Schistosomiasis Japonica in Two Murine Models

BACKGROUND

Schistosomiasis remains a major public health issue, with an estimated 230 million people infected worldwide. Novel tools for early diagnosis and surveillance of schistosomiasis are currently needed. Elevated levels of circulating microRNAs (miRNAs) are commonly associated with the initiation and progression of human disease pathology. Hence, serum miRNAs are emerging as promising biomarkers for the diagnosis of a variety of human diseases. This study investigated circulating host miRNAs commonly associated with liver diseases and schistosome parasite-derived miRNAs during the progression of hepatic schistosomiasis japonica in two murine models.

METHODOLOGY/PRINCIPAL FINDINGS

Two mouse strains (C57BL/6 and BALB/c) were infected with a low dosage of Schistosoma japonicum cercariae. The dynamic patterns of hepatopathology, the serum levels of liver injury-related enzymes and the serum circulating miRNAs (both host and parasite-derived) levels were then assessed in the progression of schistosomiasis japonica. For the first time, an inverse correlation between the severity of hepatocyte necrosis and the level of liver fibrosis was revealed during S. japonicum infection in BALB/c, but not in C57BL/6 mice. The inconsistent levels of the host circulating miRNAs, miR-122, miR-21 and miR-34a in serum were confirmed in the two murine models during infection, which limits their potential value as individual diagnostic biomarkers for schistosomiasis. However, their serum levels in combination may serve as a novel biomarker to mirror the hepatic immune responses induced in the mammalian host during schistosome infection and the degree of hepatopathology. Further, two circulating parasite-specific miRNAs, sja-miR-277 and sja-miR-3479-3p, were shown to have potential as diagnostic markers for schistosomiasis japonica.

CONCLUSIONS/SIGNIFICANCE

We provide the first evidence for the potential of utilizing circulating host miRNAs to indicate different immune responses and the severity of hepatopathology outcomes induced in two murine strains infected with S. japonicum. This study also establishes a basis for the early and cell-free diagnosis of schistosomiasis by targeting circulating schistosome parasite-derived miRNAs.

Transcriptional profiling of chronic clinical hepatic schistosomiasis japonica indicates reduced metabolism and immune responses

Schistosomiasis is a significant cause of human morbidity and mortality. We performed a genome-wide transcriptional survey of liver biopsies obtained from Chinese patients with chronic schistosomiasis only, or chronic schistosomiasis with a current or past history of viral hepatitis B. Both disease groups were compared with patients with no prior history or indicators of any liver disease. Analysis showed in the main, downregulation in gene expression, particularly those involved in signal transduction via EIF2 signalling and mTOR signalling, as were genes associated with cellular remodelling. Focusing on immune associated pathways, genes were generally downregulated. However, a set of three genes associated with granulocytes, MMP7, CLDN7, CXCL6 were upregulated. Differential gene profiles unique to schistosomiasis included the gene Granulin which was decreased despite being generally considered a marker for liver disease, and IGBP2 which is associated with increased liver size, and was the most upregulated gene in schistosomiasis only patients, all of which presented with hepatomegaly. The unique features of gene expression, in conjunction with previous reports in the murine model of the cellular composition of granulomas, granuloma formation and recovery, provide an increased understanding of the molecular immunopathology and general physiological processes underlying hepatic schistosomiasis.

Inhibition of Granulomatous Inflammation and Prophylactic Treatment of Schistosomiasis with a Combination of Edelfosine and Praziquantel

BACKGROUND

Schistosomiasis is the third most devastating tropical disease worldwide caused by blood flukes of the genus Schistosoma. This parasitic disease is due to immunologic reactions to Schistosoma eggs trapped in tissues. Egg-released antigens stimulate tissue-destructive inflammatory and granulomatous reactions, involving different immune cell populations, including T cells and granulocytes. Granulomas lead to collagen fibers deposition and fibrosis, resulting in organ damage. Praziquantel (PZQ) is the drug of choice for treating all species of schistosomes. However, PZQ kills only adult Schistosoma worms, not immature stages. The inability of PZQ to abort early infection or prevent re-infection, and the lack of prophylactic effect prompt the need for novel drugs and strategies for the prevention of schistosomiasis.

METHODOLOGY/PRINCIPAL FINDINGS

Using in vitro and in vivo approaches, we have found that the alkylphospholipid analog edelfosine kills schistosomula, and displays anti-inflammatory activity. The combined treatment of PZQ and edelfosine during a few days before and after cercariae infection in a schistosomiasis mouse model, simulating a prophylactic treatment, led to seven major effects: a) killing of Schistosoma parasites at early and late development stages; b) reduction of hepatomegaly; c) granuloma size reduction; d) down-regulation of Th1, Th2 and Th17 responses at late post-infection times, thus inhibiting granuloma formation; e) upregulation of IL-10 at early post-infection times, thus potentiating anti-inflammatory actions; f) down-regulation of IL-10 at late post-infection times, thus favoring resistance to re-infection; g) reduction in the number of blood granulocytes in late post-infection times as compared to infected untreated animals.

CONCLUSIONS/SIGNIFICANCE

Taken together, these data suggest that the combined treatment of PZQ and edelfosine promotes a high decrease in granuloma formation, as well as in the cellular immune response that underlies granuloma development, with changes in the cytokine patterns, and may provide a promising and effective strategy for a prophylactic treatment of schistosomiasis.

An ex vivo model for studying hepatic schistosomiasis and the effect of released protein from dying eggs

BACKGROUND

We report the use of an ex vivo precision cut liver slice (PCLS) mouse model for studying hepatic schistosomiasis. In this system, liver tissue is unfixed, unfrozen, and alive for maintenance in culture and subsequent molecular analysis.

METHODS AND FINDINGS

Using thick naive mouse liver tissue and sterile culture conditions, the addition of soluble egg antigen (SEA) derived from Schistosoma japonicum eggs, followed 4, 24 and 48 hrs time points. Tissue was collected for transcriptional analysis and supernatants collected to quantitate liver enzymes, cytokines and chemokines. No significant hepatotoxicity was demonstrated by supernatant liver enzymes due to the presence of SEA. A proinflammatory response was observed both at the transcriptional level and at the protein level by cytokine and chemokine bead assay. Key genes observed elevated transcription in response to the addition of SEA included: IL1-α and IL1-β, IL6, all associated with inflammation. The recruitment of antigen presenting cells was reflected in increases in transcription of CD40, CCL4 and CSF1. Indications of tissue remodeling were seen in elevated gene expression of various Matrix MetalloProteinases (MMP3, 9, 10, 13) and delayed increases in TIMP1. Collagen deposition was significantly reduced in the presence of SEA as shown in COL1A1 expression by qPCR after 24 hrs culture. Cytokine and chemokine analysis of the culture supernatants confirmed the elevation of proteins including IL6, CCL3, CCL4 and CXCL5.

CONCLUSIONS

This ex vivo model system for the synchronised delivery of parasite antigen to liver tissue provides an insight into the early phase of hepatic schistosomiasis, corresponding with the release of soluble proteins from dying schistosome eggs.

Cx3cr1 deficiency in mice attenuates hepatic granuloma formation during acute schistosomiasis by enhancing the M2-type polarization of macrophages

Acute schistosomiasis is characterized by pro-inflammatory responses against tissue- or organ-trapped parasite eggs along with granuloma formation. Here, we describe studies in Cx3cr1^−/− mice and demonstrate the role of Cx3cr1 in the pathoetiology of granuloma formation during acute schistosomiasis. Mice deficient in Cx3cr1 were protected from granuloma formation and hepatic injury induced by Schistosoma japonicum eggs, as manifested by reduced body weight loss and attenuated hepatomegaly along with preserved liver function. Notably, S. japonicum infection induced high levels of hepatic Cx3cr1 expression, which was predominantly expressed by infiltrating macrophages. Loss of Cx3cr1 rendered macrophages preferentially towards M2 polarization, which then led to a characteristic switch of the host immune defense from a conventional Th1 to a typical Th2 response during acute schistosomiasis. This immune switch caused by Cx3cr1 deficiency was probably associated with enhanced STAT6/PPAR-γ signaling and increased expression of indoleamine 2,3-dioxygenase (IDO), an enzyme that promotes M2 polarization of macrophages. Taken together, our data provide evidence suggesting that CX3CR1 could be a viable therapeutic target for treatment of acute schistosomiasis.

Highlighted Article: A reduction in CX3CR1 signaling provides protection for mice against pro-inflammatory responses and hepatic granuloma formation during acute schistosomiasis.

Real-time PCR demonstrates high prevalence of Schistosoma japonicum in the Philippines: implications for surveillance and control

Background

The Philippines has a population of approximately 103 million people, of which 6.7 million live in schistosomiasis-endemic areas with 1.8 million people being at risk of infection with Schistosoma japonicum. Although the country-wide prevalence of schistosomiasis japonica in the Philippines is relatively low, the prevalence of schistosomiasis can be high, approaching 65% in some endemic areas. Of the currently available microscopy-based diagnostic techniques for detecting schistosome infections in the Philippines and elsewhere, most exhibit varying diagnostic performances, with the Kato-Katz (KK) method having particularly poor sensitivity for detecting low intensity infections. This suggests that the actual prevalence of schistosomiasis japonica may be much higher than previous reports have indicated.

Methodology/Principal Findings

Six barangay (villages) were selected to determine the prevalence of S. japonicum in humans in the municipality of Palapag, Northern Samar. Fecal samples were collected from 560 humans and examined by the KK method and a validated real-time PCR (qPCR) assay. A high S. japonicum prevalence (90.2%) was revealed using qPCR whereas the KK method indicated a lower prevalence (22.9%). The geometric mean eggs per gram (GMEPG) determined by the qPCR was 36.5 and 11.5 by the KK. These results, particularly those obtained by the qPCR, indicate that the prevalence of schistosomiasis in this region of the Philippines is much higher than historically reported.

Conclusions/Significance

Despite being more expensive, qPCR can complement the KK procedure, particularly for surveillance and monitoring of areas where extensive schistosomiasis control has led to low prevalence and intensity infections and where schistosomiasis elimination is on the horizon, as for example in southern China.

Schistosomiasis is caused by infection with trematode blood flukes of the genus Schistosoma. Schistosoma japonicum is the causative agent of schistosomiasis in the Philippines, China and parts of Indonesia. In the Philippines, 6.7 million people live in endemic areas and 1.8 million are at risk of infection whereas concerted control efforts over the past 50 years in China have reduced the number of infected individuals considerably. Currently used microscopic techniques for diagnosis, notably the Kato-Katz (KK) technique, lack sensitivity in areas with low intensity schistosome infections. We have used a molecular diagnostic approach (qPCR), to assess the prevalence of S. japonicum in humans from six barangays in Northern Samar, the Philippines. The qPCR performed considerably better than the KK as a diagnostic procedure and could be an important tool in the future for surveillance and monitoring of areas where extensive schistosomiasis control has led to low prevalence and intensity infections and where schistosomiasis elimination is possible.

An association of Aquaporin-4 with the immunoregulation of liver pathology in mice infected with Schistosoma japonicum

Background

Schistosomiasis is a chronic parasitic disease that affects approximately 200 million people. In Schistosomiasis japonica and mansoni, parasite eggs were trapped in host liver and stimulated the CD4⁺T cell responses to regulate the formation of the granulomas. Subsequently, excessive granulomatous response in some heavily, and/or repeatedly infected individuals could result in chronic liver fibrosis and circulatory impairment. Thus, elucidation of the mechanisms of these responses will not only provide more information to better understand the mechanisms of the immunoregulation in schistosomiasis, but also help to design new therapies to control granuloma-associated immunopathology. The role of aquaporin-4 (AQP4) in water transport has been extensively investigated in the central nervous system (CNS). Recently, studies have shown that AQP4 expresses in immune system and lack of AQP4 in mice results in significantly less CD4⁺CD25⁺ T regulatory cells (Treg cells) under physiological condition, one of the subpopulations of CD4⁺T cells which restrains immunopathology in hosts with schistosomiasis. However, little information exists regarding the contribution of AQP4 to the immune regulation in schistosome infection.

Methods

The liver granulomatous response in S. japonicum-infected AQP4 knockout (KO) mice and its wild-type (WT) littermates were detected by staining liver sections with hematoxylin and eosin. The generation of various CD4⁺ T subsets, including Th1, Th2, Th17, and Treg cells were analyzed by flow cytometry. In addition, the levels of total IgG, IgG1, IgG2a in serum of infected mice were detected by ELISA assay.

Results

Our results showed an enhanced granulomatous response with increased accumulation of eosinophils and macrophages around eggs in the liver of AQP4 KO mice with Schistosomiasis japonica. In addition, our study demonstrated enhanced Th2 but reduced Th1 and Treg cells generation in AQP4 KO mice with Schistosomiasis japonica, which may, at least partly, account for the enhancement of the liver granuloma formation.

Conclusion

Our study for the first time provides evidences that AQP4 has an association with the immunoregulation of the liver granuloma formation, which may confer a new option for schistosomiasis treatment.

Immune responses to Schistosoma haematobium infection

Urogenital schistosomiasis is one of the greatest single infectious sources of human morbidity and mortality known. Through a complex cycle of infection, migration and eventual maturation and mating, S. haematobium (the aetiological agent of urogenital schistosomiasis) deposits highly immunogenic eggs within the bladder and other pelvic organs, activating a wide range of immune programs that determine both infection outcome as well as downstream immunopathology. In this review, we discuss the experimental and observational bases for our current understanding of these immune programs, focusing specifically on how the balance of type 1 and type 2 responses governs subsequent immunopathology and clinical outcome.

Cytokine patterns in experimental schistosomiasis mansoni infected mice treated with silymarin

The purpose of this study was to determine cytokine patterns in experimental schistosomiasis mansoni infected mice treated with silymarin. The study was conducted upon 100 mice that were divided into five groups; 20 each: uninfected control group, Schistosoma mansoni infected untreated mice (infected control), infected mice treated with praziquantel (PZQ), infected mice treated with silymarin and infected mice treated with both praziquantel and silymarin. 10 mice from each group were sacrificed at 10th and 18th weeks post infection respectively. Histopathological investigations were performed. Liver sections were stained with hematoxylin-eosin and Masson's trichrome stain to evaluate changes of granuloma sizes and numbers. Serum levels of the cytokines (TNF-α, IFN-γ, IL-4 and TGF-β1) were assessed in the sera of all groups by immunoassay. The measured levels of cytokines (IFN-γ, IL-4, TNF-α, TGF-β1) were found to be significantly increased in infected mice compared to normal control. At the same time, treated groups with silymarin alone or combined with PZQ showed significant decrease in IL-4, TNF-α and TGF-β1 levels compared to infected control. On the other hand, there was a significant increase in IFN-γ level observed in all treated groups compared to infected control. In addition, the histopathological examination of the liver in the group treated with PZQ showed a reduction in the number of livers eggs granuloma at all periods of sacrification compared with the infected untreated group. However, there was more decrease in granulomas diameter in both silymarin treated group or combined with PZQ at all periods of sacrification when compared to infected untreated group. In conclusion; treatment with silymarin combined with PZQ in murine schistosomiasis could reduce hepatic fibrosis by their action on the production of pro-inflammatory cytokines.

Activation of nuclear factor kappa B in the hepatic stellate cells of mice with schistosomiasis japonica

Schistosomiasis japonica is a serious tropical parasitic disease in humans, which causes inflammation and fibrosis of the liver. Hepatic stellate cells (HSCs) are known to play an important role in schistosome-induced fibrosis, but their role in schistosome-induced inflammation is still largely unknown. Here, we use a murine model of schistosomiasis japonica to investigate the role that nuclear factor kappa B (NF-κB), a critical mediator of inflammatory responses, plays in schistosome-induced inflammation. We revealed that NF-κB was significantly activated in HSCs at the early stage of infection, but not at later stages. We also show that the expression levels of several chemokines regulated by NF-κB signaling (Ccl2, Ccl3 and Ccl5) were similarly elevated at early infection. TLR4 signaling, one of the strongest known inducers of NF-κB activation, seemed not activated in HSCs post-infection. Importantly, we found that levels of miR-146 (a known negative regulator of NF-κB signaling) in HSCs opposed those of NF-κB signaling, elevating at later stage of infection. These results indicate that HSCs might play an important role in the progression of hepatic schistosomiasis japonica by linking liver inflammation to fibrosis via NF-κB signaling. Moreover, our work suggests that miR-146 appeared to regulate this process. These findings are significant and imply that manipulating the function of HSCs by targeting either NF-κB signaling or miR-146 expression may provide a novel method of treating hepatic schistosomiasis japonica.

Gaining biological perspectives from schistosome genomes

Characterization of the genomic basis underlying schistosome biology is an important strategy for the development of future treatments and interventions. Genomic sequence is now available for the three major clinically relevant schistosome species, Schistosoma mansoni, S. japonicum and S. haematobium, and this information represents an invaluable resource for the future control of human schistosomiasis. The identification of a biologically important, but distinct from the host, schistosome gene product is the ultimate goal for many research groups. While the initial elucidation of the genome of an organism is critical for most biological research, continued improvement or curation of the genome construction should be an ongoing priority. In this review we will discuss prominent recent findings utilizing a systems approach to schistosome biology, as well as the increased use of interference RNA (RNAi). Both of these research strategies are aiming to place parasite genes into a more meaningful biological perspective.

Development of "-omics" research in Schistosoma spp. and -omics-based new diagnostic tools for schistosomiasis

Schistosomiasis, caused by dioecious flatworms in the genus Schistosoma, is torturing people from many developing countries nowadays and frequently leads to severe morbidity and mortality of the patients. Praziquantel based chemotherapy and morbidity control for this disease adopted currently necessitate viable and efficient diagnostic technologies. Fortunately, those “-omics” researches, which rely on high-throughput experimental technologies to produce massive amounts of informative data, have substantially contributed to the exploitation and innovation of diagnostic tools of schistosomiasis. In its first section, this review provides a concise conclusion on the progresses pertaining to schistosomal “-omics” researches to date, followed by a comprehensive section on the diagnostic methods of schistosomiasis, especially those innovative ones based on the detection of antibodies, antigens, nucleic acids, and metabolites with a focus on those achievements inspired by “-omics” researches. Finally, suggestions about the design of future diagnostic tools of schistosomiasis are proposed, in order to better harness those data produced by “-omics” studies.

Defining a pro-inflammatory neutrophil phenotype in response to schistosome eggs

Neutrophils contribute to the pathological processes of a number of inflammatory disorders, including rheumatoid arthritis, sepsis and cystic fibrosis. Neutrophils also play prominent roles in schistosomiasis japonica liver fibrosis, being central mediators of inflammation following granuloma formation. In this study, we investigated the interaction between Schistosoma japonicum eggs and neutrophils, and the effect of eggs on the inflammatory phenotype of neutrophils. Our results showed significant upregulated expression of pro-inflammatory cytokines (IL-1α, IL-1β and IL-8) and chemokines (CCL3, CCL4 and CXCL2) in neutrophils after 4 h in vitro stimulation with S. japonicum eggs. Furthermore, mitochondrial DNA was released by stimulated neutrophils, and induced the production of matrix metalloproteinase 9 (MMP-9), a protease involved in inflammation and associated tissue destruction. We also found that intact live eggs and isolated soluble egg antigen (SEA) triggered the release of neutrophil extracellular traps (NETs), but, unlike those reported in bacterial or fungal infection, NETs did not kill schistosome eggs in vitro. Together these show that S. japonicum eggs can induce the inflammatory phenotype of neutrophils, and further our understanding of the host-parasite interplay that takes place within the in vivo microenvironment of schistosome-induced granuloma. These findings represent novel findings in a metazoan parasite, and confirm characteristics of NETs that have until now, only been observed in response to protozoan pathogens.

The effect of recombinant sTGFβ1RII and sIL13Rα2 receptor proteins on schistosomiasis japonica, hepatic fibrosis and signal transduction in a mouse model of schistosome disease

This study was designed to investigate the effect of recombinant sTGFβ1RII and sIL13Rα2 receptor proteins on schistosomiasis japonica, hepatic fibrosis and the expression of SMAD3 and STAT6. The proteins sTGFβ1RII and sIL13Rα2 were expressed in Escherichiacoli, purified using affinity chromatography and characterized by Western blotting. Female BALB/C mice (48) were randomly divided into eight groups and infected with Schistosoma japonicum. Five weeks after infection, test groups were injected with the recombinant proteins at different doses. Eight weeks after infection, lung and hepatic tissue samples were obtained and stained with hematoxylin and eosin (HE) and Masson's trichrome. Immunohistochemical staining was used to detect the expression of SMAD3 and STAT6. The recombinant proteins sTGFβ1RII and sIL13Rα2 were successfully expressed, purified, and characterized. The granuloma area, hepatic hydroxyproline (HYP) level and hepatic fibrosis of the protein therapeutic groups were significantly smaller than those of the positive control group (P<0.01). Treatment with sTGFβ1RII was more effective when the protein was administered for 4weeks rather than 2 (P<0.01). Hepatic fibrosis in the groups using a low dose of protein sTGFβ1 was lower that of the combination group (P<0.05). The expression level of STAT6 was significantly lower in groups treated with sIL13Rα2 than in groups not treated with the protein (P<0.01). The recombinant proteins TGFβ1RII and sIL13Rα2 were able to decrease granuloma area and hepatic fibrosis in schistosomiasis japonica, and also reduced the expression of the signal transduction proteins SMAD3 and STAT6. The proteins were more effective when used in combination than when applied singly.

The intriguing host innate immune response: novel anti-parasitic defence by neutrophil extracellular traps

The capacity of polymorphonuclear neutrophils (PMN) and other leucocytes of the innate immune system to expel their DNA in a controlled process into the extracellular environment to trap and kill pathogenic microorganisms led to a paradigm shift in our comprehension of host leucocyte-pathogen interactions. Formation of neutrophil extracellular traps (NETs) has recently been recognized as a novel effector mechanism of the host innate immune response against microbial infections. Meanwhile evidence has arisen that NET formation is a widely spread mechanism in vertebrates and invertebrates and extends not only to the entrapment of microbes, fungi and viruses but also to the capture of protozoan and metazoan parasites. PMN produce NETs after stimulation with mitogens, cytokines or pathogens in a controlled process which depends on reactive oxygen species (ROS) and the induction of the Raf-MEK-ERK-mediated signalling pathway cascade. NETs consist of nuclear DNA as a backbone decorated with histones, antimicrobial peptides, and PMN-specific granular enzymes thereby providing an extracellular matrix capable of entrapping and killing invasive pathogens. This review is intended to summarize parasite-related data on NETs. Special attention will be given to NET-associated mechanisms by which parasites, in particular apicomplexa, might be hampered in their ability to reproduce within the host cell and complete the life cycle.

Schistosoma japonicum egg specific protein SjE16.7 recruits neutrophils and induces inflammatory hepatic granuloma initiation

Neutrophils are known to play a major role in the egg granulomatous lesions caused by Schistosoma japonicum, but the precise mechanism by which eggs recruit or active neutrophil is unknown. Here we report S. japonicum egg specific EF-hand protein-SjE16.7 is a potent neutrophil recruiter and initiates the egg associated inflammatory granuloma in schistosomiasis. We show that the expression of SjE16.7 at level of both mRNA and protein is restricted to the egg stage. It locates in the miracidium and subshell area of the egg and can be secreted by the egg. The antigenic properties of SjE16.7 strongly suggest a role for SjE16.7 as an egg-derived molecule involved in host-parasite interactions. To study SjE16.7 functions in vivo, we challenged murine air pouch with recombinant SjE16.7. The results showed SjE16.7 trigged more inflammatory cell infiltration than vehicle or control protein. Using peritoneal exudate neutrophils from mice, we found that SjE16.7 significantly induced neutrophil chemotaxis in vitro, and the observed phenotypes were associated with enhanced Rac GTPase activation in SjE16.7 treated cells. Finally, in vivo hepatic granuloma formation model showed SjE16.7 coupled beads recruited more inflammatory cell infiltration than control beads. Our findings suggest SjE16.7 is an important pathogenic factor derived from egg. By recruiting neutrophils and inducing local inflammation, SjE16.7 facilitates eggs to be excreted through gut tissues and also initiates pathology in the liver; therefore SjE16.7 is a possible target for the prevention and treatment of schistosomiasis.

As a neglected disease, schistosomiasis continues to be a significant cause of parasitic morbidity and mortality worldwide. Schistosoma japonicum is one of the major causative agents of human schistosomiasis. Trapped in the liver or intestinal tissue, S. japonicum eggs are the main cause of pathology following infection. They induce vigorous immune responses from the host, which facilitate the passage of the eggs from the tissue to the gut lumen and cause the pathology in liver. In this paper, we described, for the first time, S. japonicum egg specific EF-hand protein-SjE16.7 is a potent neutrophil recruiter and initiates the egg associated inflammatory granuloma in schistosomiasis. This study presents a precise mechanism by which eggs recruit neutrophil and induce inflammatory response. It furthers our understanding of the immunopathogenesis of human schistosomiasis. In addition, it provides a potential target for the prevention and treatment of this globally important parasite.

Cellular and chemokine-mediated regulation in schistosome-induced hepatic pathology

In hepatic schistosomiasis, pathology arises when schistosome eggs become lodged in the host liver, evoking an interleukin 4 (IL-4)- and IL-13-mediated dominant CD4(+) Th2 immune response. This response leads to the development of granulomas and fibrosis, with eosinophils, neutrophils, macrophages, hepatic stellate cells, and lymphocytes all identified as major cellular contributors to these events. This review outlines the cellular and molecular mechanisms of hepatic schistosomiasis, with an emphasis on the major cellular components and their release of chemokines. The differences between Schistosoma mansoni- and Schistosoma japonicum-induced hepatic granuloma are also discussed. This comprehensive overview of the processes associated with hepatic schistosomiasis may provide new insights into improved treatment for both schistosomiasis and other granulofibrotic diseases.

Differential expression of microRNAs in the non-permissive schistosome host Microtus fortis under schistosome infection

The reed vole Microtus fortis is the only mammal known in China in which the growth, development and maturation of schistosomes (Schistosoma japonicum) is prevented. It might be that the anti-schistosomiasis mechanisms of M. fortis associate with microRNA-mediated gene expression, given that the latter has been found to be involved in gene regulation in eukaryotes. In the present study, the difference between pathological changes in tissues of M. fortis and of mice (Mus musculus) post-schistosome infection were observed by using hematoxylin-eosin staining. In addition, microarray technique was applied to identify differentially expressed miRNAs in the same tissues before and post-infection to analyze the potential roles of miRNAs in schistosome infection in these two different types of host. Histological analyses showed that S. japonicum infection in M. fortis resulted in a more intensive inflammatory response and pathological change than in mice. The microarray analysis revealed that 162 miRNAs were expressed in both species, with 12 in liver, 32 in spleen and 34 in lung being differentially expressed in M. fortis. The functions of the differentially expressed miRNAs were mainly revolved in nutrient metabolism, immune regulation, etc. Further analysis revealed that important signaling pathways were triggered after infection by S. japonicum in M. fortis but not in the mice. These results provide new insights into the general mechanisms of regulation in the non-permissive schistosome host M. fortis that exploits potential miRNA regulatory networks. Such information will help improve current understanding of schistosome development and host-parasite interactions.

Chronic ammonia exposure does not influence hepatic gene expression in growing pigs

Housed pigs are often exposed to elevated concentrations of atmospheric ammonia. This aerial pollutant is widely considered to be an environmental stressor that also predisposes to reduced growth rates and poor health, although evidence to support this view is limited. Hepatic gene expression is very responsive to stress and metabolic effects. Two batches of growing pigs were therefore exposed to a nominal concentration of atmospheric ammonia of either 5 ppm (low) or 20 ppm (high) from 4 weeks of age for 15 weeks. Growth rates were monitored. Samples of liver were taken after slaughter (at ∼19 weeks of age). Samples from the second batch were analysed for global gene expression using 23 K Affymetrix GeneChip porcine genome arrays. Samples from both batches were subsequently tested for five candidate genes using quantitative real-time PCR (qPCR). The array analysis failed to detect any significant changes in hepatic gene expression following chronic exposure to atmospheric ammonia. Animals clustered into two main groups but this was not related to the experimental treatment. There was also no difference in growth rates between groups. The qPCR analyses validated the array results by showing similar fold changes in gene expression to the arrays. They revealed a significant batch effect in expression of lipin 1 (LPIN1), Chemokine (C-X-C motif) ligand 14 (CXCL14), serine dehydratase (SDS) and hepcidin antimicrobial peptide (HAMP). Only CXCL14, a chemotactic cytokine for monocytes, was significantly down-regulated in response to ammonia. As chronic exposure to atmospheric ammonia did not have a clear influence on hepatic gene expression, this finding implies that 20 ppm of atmospheric ammonia did not pose a significant material risk to the health or metabolism of housed pigs.

A study of immunomodulatory genes responses to macrophages of Schistosoma japonicum infection during different stages by microarray analysis

Macrophages initiate, modulate, and also serve as final effector cells in immune responses during the course of schistosomal infections. In this study, we investigated the gene expression profile and functional changes of macrophages in immune responses against the Schistosoma japonicum by microarray analysis. Hierarchical clustering analysis demonstrated that a significant switch in gene transformation associated with a type-1 response and linked with a type-2 cytokine phenotype occurs between 4.5 and 8 weeks post-infection. Moreover, the gene profiles at 3 later time-points following egg challenge were similar in complexity and magnitude. The data also showed that there were mostly inhibition of gene expression related TLR, IFN, MHC and TNFrsf at the switch between 4.5 and 8 weeks post-infection, It is suggested that these immunomodulatory genes may be down-regulated in defense against S. japonicum eggs and granuloma pathology. The induction of alternatively activated macrophage (AAMϕ) was important for dampening the inflammation in hepatic granulomas and contributing to a decrease in cytotoxicity. The gene expressions involved in repair/remodeling during liver fibrosis were also observed after egg production. Understanding the immune mechanisms associated with parasitic resistance, pathology of parasite infection, and parasite growth will provide useful insight on host-schistosome interactions and for the control of schistosomiasis.

MicroRNA-gene expression network in murine liver during Schistosoma japonicum infection

BACKGROUND

Schistosomiasis japonica remains a significant public health problem in China and Southeast Asian countries. The most typical and serious outcome of the chronic oriental schistosomiasis is the progressive granuloma and fibrosis in the host liver, which has been a major medical challenge. However, the molecular mechanism underling the hepatic pathogenesis is still not clear.

METHODOLOGY AND PRINCIPAL FINDINGS

Using microarrays, we quantified the temporal gene expression profiles in the liver of Schistosoma japonicum-infected BALB/c mice at 15, 30, and 45 day post infection (dpi) with that from uninfected mice as controls. Gene expression alternation associated with liver damage was observed in the initial phase of infection (dpi 15), which became more magnificent with the onset of egg-laying. Up-regulated genes were dominantly associated with inflammatory infiltration, whereas down-regulated genes primarily led to the hepatic functional disorders. Simultaneously, microRNA profiles from the same samples were decoded by Solexa sequencing. More than 130 miRNAs were differentially expressed in murine liver during S. japonicum infection. MiRNAs significantly dysregulated in the mid-phase of infection (dpi 30), such as mmu-miR-146b and mmu-miR-155, may relate to the regulation of hepatic inflammatory responses, whereas miRNAs exhibiting a peak expression in the late phase of infection (dpi 45), such as mmu-miR-223, mmu-miR-146a/b, mmu-miR-155, mmu-miR-34c, mmu-miR-199, and mmu-miR-134, may represent a molecular signature of the development of schistosomal hepatopathy. Further, a dynamic miRNA-gene co-expression network in the progression of infection was constructed.

CONCLUSIONS AND SIGNIFICANCE

This study presents a global view of dynamic expression of both mRNA and miRNA transcripts in murine liver during S. japonicum infection, and highlights that miRNAs may play a variety of regulatory roles in balancing the immune responses during the development of hepatic pathology. The data provide robust information for further researches on the pathogenesis and molecular events of hepatopathy induced by schistosome eggs.

Chronic schistosome infection leads to modulation of granuloma formation and systemic immune suppression

Schistosome worms have been infecting humans for millennia, but it is only in the last half century that we have begun to understand the complexities of this inter-relationship. As our sophistication about the inner workings of every aspect of the immune system has increased, it has also become obvious that schistosome infections have broad ranging effects on nearly all of the innate and adaptive immune response mechanisms. Selective pressures on both the worms and their hosts, has no doubt led to co-evolution of protective mechanisms, particularly those that favor granuloma formation around schistosome eggs and immune suppression during chronic infection. The immune modulatory effects that chronic schistosome infection and egg deposition elicit have been intensely studied, not only because of their major implications to public health issues, but also due to the emerging evidence that schistosome infection may protect humans from severe allergies and autoimmunity. Mouse models of schistosome infection have been extremely valuable for studying immune modulation and regulation, and in the discovery of novel aspects of immunity. A progression of immune reactions occurs during granuloma formation ranging from innate inflammation, to activation of each branch of adaptive immune response, and culminating in systemic immune suppression and granuloma fibrosis. Although molecular factors from schistosome eggs have been identified as mediators of immune modulation and suppressive functions of T and B cells, much work is still needed to define the mechanisms of the immune alteration and determine whether therapies for asthma or autoimmunity could be developed from these pathways.

Role of resident liver cells in the pathogenesis of schistosomiasis

Pathology in schistosomiasis occurs as a result of eggs deposited in the liver by the schistosome parasite. A granulomatous reaction occurs, resulting in portal hypertension and hepatic fibrosis. Resident non-parenchymal cells within the liver take part in this process, including hepatic stellate cells, which are responsible for collagen production, and Kupffer cells, the liver macrophages involved in both host protection and in pathology. Other cells such as liver sinusoidal endothelial cells or portal fibroblasts may also be involved in this process. This review discusses the possible role of these resident liver cells in the pathology associated with schistosomiasis and provides information which may assist our understanding of the mechanisms associated with chronic liver disease in general.

Differences in genomic architecture between two distinct geographical strains of the blood fluke Schistosoma japonicum reveal potential phenotype basis

The Chinese (SjC) and Philippine (SjP) strains of the blood fluke Schistosoma japonicum have been shown to present clearly different phenotypes in fecundity, pathology, drug sensitivity and immunology. We used microarray based comparative genomic hybridisation (aCGH) to investigate structural differences in the genomes of the two strains and identified seven distinct regions of the S. japonicum genome that present differential aCGH representing either deletion or duplication regions in SjP. Within these regions, genes predicted to be associated with the recognised phenotypic differences were identified and that may provide new insights into the biology and evolution of the two strains, with implications for the epidemiology and control of schistosomiasis japonica in China and the Philippines.

Gene profile of chemokines on hepatic stellate cells of schistosome-infected mice and antifibrotic roles of CXCL9/10 on liver non-parenchymal cells

Hepatic stellate cells (HSCs) play a key role in the development of liver fibrosis caused by schistosomiasis. Chemokines were widely expressed and involved in cellular activation, proliferation and migration in inflammatory and infectious diseases. However, little is known about the expressions of chemokines on HSCs in the schistosoma infection. In addition, the roles of chemokines in pathogenesis of liver fibrosis are not totally clear. In our study, we used microarray to analyze the temporal gene expressions of primary HSCs isolated from mice with both acute and chronic schistosomiasis. Our microarray data showed that most of the chemokines expressed on HSCs were upregulated at 3 weeks post-infection (p.i) when the egg granulomatous response was not obviously evoked in the liver. However, some of them like CXCL9, CXCL10 and CXCL11 were subsequently decreased at 6 weeks p.i when the granulomatous response reached the peak. In the chronic stage, most of the differentially expressed chemokines maintained persistent high-abundances. Furthermore, several chemokines including CCR2, CCR5, CCR7, CXCR3, CXCR4, CCL2, CCL5, CCL21, CXCL9 and CXCL10 were expressed by HCSs and the abundances of them were changed following the praziquantel treatment in the chronic stage, indicating that chemokines were possibly necessary for the persistence of the chronic stage. In vitro experiments, hepatic non-parenchymal cells, primary HSCs and human HSCs line LX-2 were stimulated by chemokines. The results showed that CXCL9 and CXCL10, but not CXCL11 or CXCL4, significantly inhibited the gene expressions of Col1α1, Col3α1 and α-SMA, indicating the potential anti-fibrosis effect of CXCL9 and CXCL10 in schistosomiasis. More interestingly, soluble egg antigen (SEA) of Schistosoma japonicum was able to inhibit transcriptional expressions of some chemokines by LX-2 cells, suggesting that SEA was capable of regulating the expression pattern of chemokine family and modulating the hepatic immune microenvironment in schistosomiasis.

Potential antifibrotic effects of AT1 receptor antagonist, losartan, and/or praziquantel on acute and chronic experimental liver fibrosis induced by Schistosoma mansoni

1. This study investigates the potential antifibrotic effect of losartan, AT-1 receptor antagonist, and/or praziquantel (PZQ) on acute and chronic hepatic fibrosis induced by Schistosoma mansoni (S. mansoni). 2. Schistosoma mansoni-infected mice were in two batches (I & II), each in four groups: (i) Infected untreated; (ii) treated with losartan, starting from the 4th or 12th weeks post-infection (PI); (iii) treated with PZQ in the 7th week PI; and (iv) treated with losartan, as group (ii) plus PZQ as group (iii). Comparable groups of uninfected mice were run in parallel with infected groups. Mice of batches I and II were killed 10 and 18 weeks PI, respectively. Hepatic content of hydroxyproline (HYP), serum levels and tissue expression of matrix metalloproteinase-2 (MMP-2), and transforming growth factor-β1 (TGF-β1) were determined. Parasitological, biochemical and histological parameters, which reflect disease severity and morbidity, were examined. 3. Losartan alone caused a considerable decrease in worm burden, hepatic tissue egg load with an increase in percentage of dead eggs, modulation of granuloma size and regression of inflammatory reactions, which was less obvious in the chronic stage. The best results were obtained when losartan was co-administered with PZQ, especially in the acute stage. This was revealed by a remarkable reduction in serum levels and tissue expression of MMP-2, TGF-β1 and HYP content, accompanied by conservation of hepatic reduced glutathione (GSH) versus the PZQ-treated group. 4. In conclusion, losartan has a promising antifibrotic action and could be introduced as a therapeutic tool with PZQ especially in acute schistosomal hepatic fibrosis.

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.

Anti-inflammatory/anti-fibrotic effects of the hepatoprotective silymarin and the schistosomicide praziquantel against Schistosoma mansoni-induced liver fibrosis

BACKGROUND

Praziquantel (PZQ) is an isoquinoline derivative (2-cyclohexylcarbonyl-1, 2, 3, 6, 7, 11b-hexahydro-4H-pyrazino{2,1-a}-isoquinoline-4-one), and is currently the drug of choice for all forms of schistosomiasis. Silymarin, a standardized milk thistle extract, of which silibinin is the main component, is known for its hepatoprotective, anti-inflammatory, antioxidant activities, and hepatocyte regeneration. This study investigates the anti-inflammatory/anti-fibrotic effects of silymarin and/or PZQ on schistosomal hepatic fibrosis.

METHODS

Schistosoma mansoni-infected mice were divided into two large groups (I & II), each with four subgroups and were run in parallel. (i) Infected untreated; (ii) treated with silymarin, starting from the 4th (3 weeks before PZQ therapy) or 12th (5 weeks after PZQ therapy) weeks post infection (PI); (iii) treated with PZQ in the 7th week PI; and (iv) treated with silymarin, as group (ii) plus PZQ as group (iii). Comparable groups of uninfected mice run in parallel with the infected groups. Mice of groups I and II were killed 10 and 18 weeks PI, respectively. Hepatic content of hydroxyproline (HYP), serum levels and tissue expression of matrix metalloproteinase-2 (MMP-2), transforming growth factor-β1 (TGF-β1) and number of mast cells were determined. In addition, parasitological, biochemical and histological parameters that reflect disease severity and morbidity were examined.

RESULTS

Silymarin caused a partial decrease in worm burden; hepatic tissue egg load, with an increase in percentage of dead eggs; modulation of granuloma size, with significant reduction of hepatic HYP content; tissue expression of MMP-2, TGF-β1; number of mast cells, with conservation of hepatic reduced glutathione (GSH). PZQ produced complete eradication of worms, eggs and alleviated liver inflammation and fibrosis. The best results were obtained, in most parameters studied, in groups of mice treated with silymarin in addition to PZQ.

CONCLUSIONS

Our results point to silymarin as a promising anti-inflammatory and anti-fibrotic agent; it could be introduced as a therapeutic tool with PZQ in the treatment of schistosomal liver fibrosis, but further studies on mechanisms of silymarin and PZQ in chronic liver diseases may shed light on developing therapeutic methods in clinical practice.

Macrophage activation governs schistosomiasis-induced inflammation and fibrosis

Macrophages regulate the initiation, maintenance, and resolution of chronic inflammatory responses and their function depends on their activation status. Studies in mice infected with the helminth parasite Schistosoma mansoni have been particularly helpful in defining the in vivo function of classically and alternatively activated macrophages (AAMϕs). These studies have shown that AAMϕs protect mice from acute and chronic S. mansoni infection through distinct mechanisms, which are discussed in this Viewpoint.

Interleukin-4 (IL-4) and IL-13 suppress excessive neutrophil infiltration and hepatocyte damage during acute murine schistosomiasis japonica

Due to the importance of neutrophils and proinflammatory cytokines in schistosomal liver damage, we analyzed the mechanisms underlying neutrophil and proinflammatory responses in murine schistosomiasis japonica. We found that granulomatous inflammation around parasite eggs in the liver was greater in Schistosoma japonicum-infected IL-4-/- IL-13-/- (double-knockout [DKO]) mice than in infected wild-type (WT) mice at 6 weeks, but not at 8 weeks, postinfection, suggesting the importance of Th2 responses in these typical hepatic lesions. Infected DKO mice also showed increased neutrophil infiltration accompanying more severe pathology, as shown by the enhanced necrosis of hepatocytes. This was not likely due to a Th1/Th2 imbalance, because there was no detectable increase in gamma interferon (IFN-γ) production in these DKO mice. mRNA expression of interleukin-17A (IL-17A), proinflammatory cytokines, and the neutrophil chemoattractant CXCL2 in liver was higher in infected DKO mice than in WT mice. However, in IL-4-/- IL-13-/- IL-17A-/- (triple-knockout [TKO]) mice, the absence of IL-17A was associated with only marginal differences in schistosomal liver damage, suggesting that IL-17A is only partially responsible for neutrophil-driven hepatic damage. Furthermore, the expression of mRNAs encoding proinflammatory cytokines was not under the control of IL-17A in TKO mice. These findings indicate that IL-4 and IL-13 suppress excessive neutrophil recruitment, proinflammatory cytokine production, and hepatic damage during the acute stage of S. japonicum infection, suggesting that neutrophils and proinflammatory cytokines are mainly responsible for hepatocyte damage during acute murine schistosomiasis japonica. However, neutrophil induction and the production of proinflammatory cytokines were not due solely to IL-17A.

Migrating Schistosoma japonicum schistosomula induce an innate immune response and wound healing in the murine lung

The migrating schistosomulum is an important stage of the schistosome lifecycle and represents a key target for elimination of infection by natural and vaccine-induced host immune responses. To gain a better understanding of how schistosomes initiate a primary host immune response we have characterised the host lung response to migrating Schistosoma japonicum schistosomula using a combination of histopathology, microarray analysis and real-time PCR. Our findings indicate that the early pulmonary response to these migrating larvae is characteristic of innate inflammation and wound healing. This response is associated with significant up-regulation of several genes with immunoregulatory function including Ch25h, Hmox1 and Retnla which may act to control the nature or magnitude of the inflammatory response to the migrating schistosomula, promoting both parasite and host survival. These findings contribute to our understanding of host-parasite interactions associated with schistosome and, especially, S. japonicum infection, and may aid the future design of novel vaccines that target the lung stage schistosomulum.

Differential expression of chemokine and matrix re-modelling genes is associated with contrasting schistosome-induced hepatopathology in murine models

The pathological outcomes of schistosomiasis are largely dependent on the molecular and cellular mechanisms of the host immune response. In this study, we investigated the contribution of variations in host gene expression to the contrasting hepatic pathology observed between two inbred mouse strains following Schistosoma japonicum infection. Whole genome microarray analysis was employed in conjunction with histological and immunohistochemical analysis to define and compare the hepatic gene expression profiles and cellular composition associated with the hepatopathology observed in S. japonicum-infected BALB/c and CBA mice. We show that the transcriptional profiles differ significantly between the two mouse strains with high statistical confidence. We identified specific genes correlating with the more severe pathology associated with CBA mice, as well as genes which may confer the milder degree of pathology associated with BALB/c mice. In BALB/c mice, neutrophil genes exhibited striking increases in expression, which coincided with the significantly greater accumulation of neutrophils at granulomatous regions seen in histological sections of hepatic tissue. In contrast, up-regulated expression of the eosinophil chemokine CCL24 in CBA mice paralleled the cellular influx of eosinophils to the hepatic granulomas. Additionally, there was greater down-regulation of genes involved in metabolic processes in CBA mice, reflecting the more pronounced hepatic damage in these mice. Profibrotic genes showed similar levels of expression in both mouse strains, as did genes associated with Th1 and Th2 responses. However, imbalances in expression of matrix metalloproteinases (e.g. MMP12, MMP13) and tissue inhibitors of metalloproteinases (TIMP1) may contribute to the contrasting pathology observed in the two strains. Overall, these results provide a more complete picture of the molecular and cellular mechanisms which govern the pathological outcome of hepatic schistosomiasis. This improved understanding of the immunopathogenesis in the murine model schistosomiasis provides the basis for a better appreciation of the complexities associated with chronic human schistosomiasis.

Schistosomiasis is a significant cause of morbidity and mortality in the tropical world although its true burden has been historically underestimated. Millions of people currently endure severe pathology as a result of schistosome infections, although some individuals appear to be less susceptible to infection despite constant parasite exposure. A similar range of disease susceptibility is evident in different strains of inbred mice infected with schistosomes, thereby mirroring the clinical situation. Granuloma formation in the liver of both humans and mice is a characteristic manifestation of chronic schistosomiasis, and is largely controlled by gene signalling pathways. Certain genes expressed in particular cohorts of mice and humans may be associated with the development of severe pathology, or may confer a protective phenotype. This murine study highlights some key molecular aspects of chronic schistosomiasis which may be responsible for the development of both mild and severe pathology, and provides a bench mark for studying the mechanisms of schistosome-induced disease in humans.

SerpinB2 deficiency modulates Th1⁄Th2 responses after schistosome infection

SerpinB2, also known as plasminogen activator inhibitor type-2, is a major product of macrophages and is upregulated during many infections. Although SerpinB2 inhibits urokinase plasminogen activator in vitro, evidence that this represents its physiological role in vivo is not compelling. We have recently shown that SerpinB2-/-mice generate enhanced Th1 responses after immunization with a Th1 immunogen. Herein,we show that Schistosoma japonicum granulomas induced liver SerpinB2 mRNA expression by >600-fold in wild-type mice. In SerpinB2-/- mice, worm and egg burden, and granuloma number and volume were unaffected. However, granulomas in these mice were associated with reduced fibrosis (as determined by Sirius red staining and image analysis) and increased iNOS, IL-6, IL-10 and TNFa and decreased Arg 1 and IL-13 mRNA expression. SerpinB2-/- mice immunized with soluble egg antigen (SEA) also showed reduced levels of SEA-specific IgG1. SerpinB2 deficiency thus promoted certain Th1 and reduced certain Th2 responses in response to this Th2 immunogen.

Hepatic stellate cells and parasite-induced liver fibrosis

Fibrogenesis is a common feature of many diseases where there is severe insult to the liver. The hepatic stellate cell trans-differentiation into a myofibroblast has been identified as an important event in liver fibrogenesis and has been well investigated over the last few years in a number of liver diseases. The trans-differentiation process can be monitored in vitro by evaluation of biomarkers that are characteristic of normal quiescent hepatic stellate cells or activated myofibroblasts. Two major parasitic diseases associated with liver injury and fibrosis are schistosomiasis and echinococcosis. Recent studies have highlighted a role for activated hepatic stellate cells in both murine and human schistosomiasis as well as demonstrating that schistosome antigens are able to regulate this trans-differentiation process. Study of the hepatic stellate cell and its interaction with parasite-derived antigens may be pivotal in our understanding of the pathology associated with schistosomiasis and other parasitic diseases, including echinococcosis, as well as revealing new information on the trans-differentiation process in this cell type.

Co-ordinated gene expression in the liver and spleen during Schistosoma japonicum infection regulates cell migration

Determining the molecular events induced in the spleen during schistosome infection is an essential step in better understanding the immunopathogenesis of schistosomiasis and the mechanisms by which schistosomes modulate the host immune response. The present study defines the transcriptional and cellular events occurring in the murine spleen during the progression of Schistosoma japonicum infection. Additionally, we compared and contrasted these results with those we have previously reported for the liver. Microarray analysis combined with flow cytometry and histochemistry demonstrated that transcriptional changes occurring in the spleen were closely related to changes in cellular composition. Additionally, the presence of alternatively activated macrophages, as indicated by up-regulation of Chi3l3 and Chi3l4 and expansion of F4/80⁺ macrophages, together with enhanced expression of the immunoregulatory genes ANXA1 and CAMP suggests the spleen may be an important site for the control of S. japonicum-induced immune responses. The most striking difference between the transcriptional profiles of the infected liver and spleen was the contrasting expression of chemokines and cell adhesion molecules. Lymphocyte chemokines, including the homeostatic chemokines CXCL13, CCL19 and CCL21, were significantly down-regulated in the spleen but up-regulated in the liver. Eosinophil (CCL11, CCL24), neutrophil (CXCL1) and monocyte (CXCL14, CCL12) chemokines and the cell adhesion molecules VCAM1, NCAM1, PECAM1 were up-regulated in the liver but unchanged in the spleen. Chemokines up-regulated in both organs were expressed at significantly higher levels in the liver. Co-ordinated expression of these genes probably contributes to the development of a chemotactic signalling gradient that promotes recruitment of effector cells to the liver, thereby facilitating the development of hepatic granulomas and fibrosis. Together these data provide, for the first time, a comprehensive overview of the molecular events occurring in the spleen during schistosomiasis and will substantially further our understanding of the local and systemic mechanisms driving the immunopathogenesis of this disease.

Schistosomiasis is a significant cause of illness and death in the developing world. Inflammation and scarring in the liver and enlargement of the spleen (splenomegaly) are common features of the disease. Changes occurring in the spleen have the potential to influence the way in which the body deals with infection but the mechanisms driving these changes are not well characterised. In the present study we determined, for the first time, the gene expression profile of the mouse spleen during infection with Schistosoma japonicum and compared these results to those previously reported for the liver to determine if processes occurring in these organs co-operate to promote hepatic inflammation and granuloma formation. Our data indicated that gene expression in the spleen is related to the types of cells present and suggest that the spleen might be important in controlling schistosome-induced inflammation. Comparison of the liver and spleen showed that expression of cell signalling molecules (chemokines) was much higher in the liver, potentially promoting the recruitment of specific cell types to this organ, causing inflammation and scarring. The results from this study enhance our knowledge of the mechanisms that drive schistosome-induced splenomegaly and liver inflammation.