CD4+ T cell-mediated granulomatous pathology in schistosomiasis is downregulated by a B cell-dependent mechanism requiring Fc receptor signaling

IgG persistence showed weak clinical aspects in chronic schistosomiasis patients

Schistosomiasis is a chronic parasitic disease, which affects the quality of daily life of patients and imposes a huge burden on society. Hepatic fibrosis in response to continuous insult of eggs to the liver is a significant cause of morbidity and mortality. However, the mechanisms of hepatic fibrosis in schistosomiasis are largely undefined. The purpose of our study is to detect the indicator to hepatic fibrosis in schistosomiasis. A total of 488 patients with chronic schistosomiasis japonica were enrolled in our study. The patients were divided into two groups according to liver ultrasound examination, which could indicate liver fibrosis of schistosomiasis with unique reticular changes. Logistic regression analysis showed that globulin, albumin/globulin, GGT levels and anti-Schistosoma IgG were independently associated with liver fibrosis in patients with schistosomiasis and IgG was the largest association of liver fibrosis (OR  2.039, 95% CI 1.293-3.213). We further compared IgG+ patients with IgG- patients. IgG+ patients (ALT 25 U/L, GGT 31 U/L) slightly higher than IgG- patients (ALT 22 U/L, GGT 26 U/L) in ALT and GGT. However, the fibrosis of liver in IgG+ patients (Grade II(19.7%), Grade III(7.3%)) were more severe than that in IgG- patients(Grade II(12.5%), Grade III(2.9%)) according to the grade of liver ultrasonography. Our results showed anti-Schistosoma IgG was independently associated with liver fibrosis in patients with chronic schistosomiasis japonica and patients with persistent anti-Schistosoma IgG might have more liver fibrosis than negative patients despite no obvious clinical signs or symptoms.

Dynamics of Host Immune Response Development During Schistosoma mansoni Infection

Schistosomiasis is a disease of global significance, with severity and pathology directly related to how the host responds to infection. The immunological narrative of schistosomiasis has been constructed through decades of study, with researchers often focussing on isolated time points, cell types and tissue sites of interest. However, the field currently lacks a comprehensive and up-to-date understanding of the immune trajectory of schistosomiasis over infection and across multiple tissue sites. We have defined schistosome-elicited immune responses at several distinct stages of the parasite lifecycle, in three tissue sites affected by infection: the liver, spleen, and mesenteric lymph nodes. Additionally, by performing RNA-seq on the livers of schistosome infected mice, we have generated novel transcriptomic insight into the development of schistosome-associated liver pathology and fibrosis across the breadth of infection. Through depletion of CD11c+ cells during peak stages of schistosome-driven inflammation, we have revealed a critical role for CD11c+ cells in the co-ordination and regulation of Th2 inflammation during infection. Our data provide an updated and high-resolution account of how host immune responses evolve over the course of murine schistosomiasis, underscoring the significance of CD11c+ cells in dictating host immunopathology against this important helminth infection.

Trichinella-induced immunomodulation: Another tale of helminth success

Trichinella spiralis is a unique parasite in that both the adults and larvae survive in two different intracellular niches in the same host. The immune response, albeit intense, is highly modulated to ensure the survival of both the host and the parasite. It is skewed to T helper 2 and regulatory arms. Diverse cells from both the innate and adaptive compartments of immunity, including dendritic cells, T regulatory cells, and alternatively activated macrophages are thought to mediate such immunomodulation. The parasite has also an outstanding ability to evade the immune system by several elaborate processes. The molecules derived from the parasites including Trichinella, particularly the components of the excretory-secretory products, are being continually identified and explored for the potential of ameliorating the immunopathology in animal models of diverse inflammatory and autoimmune human diseases. Herein we discuss the various aspects of Trichinella-induced immunomodulation with a special reference to the practical implications of the immune system manipulation in alleviating or possibly curing human diseases.

The Road to Elimination: Current State of Schistosomiasis Research and Progress Towards the End Game

The new WHO Roadmap for Neglected Tropical Diseases targets the global elimination of schistosomiasis as a public health problem. To date, control strategies have focused on effective diagnostics, mass drug administration, complementary and integrative public health interventions. Non-mammalian intermediate hosts and other vertebrates promote transmission of schistosomiasis and have been utilized as experimental model systems. Experimental animal models that recapitulate schistosomiasis immunology, disease progression, and pathology observed in humans are important in testing and validation of control interventions. We discuss the pivotal value of these models in contributing to elimination of schistosomiasis. Treatment of schistosomiasis relies heavily on mass drug administration of praziquantel whose efficacy is comprised due to re-infections and experimental systems have revealed the inability to kill juvenile schistosomes. In terms of diagnosis, nonhuman primate models have demonstrated the low sensitivity of the gold standard Kato Katz smear technique. Antibody assays are valuable tools for evaluating efficacy of candidate vaccines, and sera from graded infection experiments are useful for evaluating diagnostic sensitivity of different targets. Lastly, the presence of Schistosomes can compromise the efficacy of vaccines to other infectious diseases and its elimination will benefit control programs of the other diseases. As the focus moves towards schistosomiasis elimination, it will be critical to integrate treatment, diagnostics, novel research tools such as sequencing, improved understanding of disease pathogenesis and utilization of experimental models to assist with evaluating performance of new approaches.

Protective immune potential of multiple antigenic peptide (MAP) constructs comprising peptides that are shared by several cysteine peptidases against Schistosoma mansoni infection in mice

In vaccine trials, Schistosoma mansoni cathepsin B1 (SmCB1), helminth cathepsins of the L family (e.g., SmCL3), and papain consistently induce highly significant reductions in challenge worm burden and egg viability, but generated no additive protective effects when used in combination. The protective capacity of the cysteine peptidases is associated with modest (SmCB1) and poor (cathepsins L) production of cytokines and antibodies, essentially of the type 2 axis, and is only marginally reduced upon use of proteolytically inactive enzymes. In this work, peptides shared by SmCB1, cathepsins of the L family, papain and other allergens were selected, synthesized as tetrabranched multiple antigen peptide constructs (MAP-1 and MAP-2), and used in two independent experiments to immunize outbred mice, in parallel with papain. The two peptides elicited significant (P <  0.05) reduction in challenge worm burden when compared to unimmunized mice, albeit lower than that achieved by papain. Protection was associated with modest serum type 2 cytokines and antibody levels in MAP-, and papain-immunized mice. Immunization with papain also elicited a reduction in parasite egg load, viability, and granuloma numbers in liver and intestine. MAP-1 and MAP-2 immunogens displayed some opposite effects- MAP-1 leading to higher egg numbers with poor vitality, whereas MAP-2 immunization yielded fewer eggs. Cysteine peptidase thus appear to carry peptides that elicit opposing outcomes, highlighting the difficulty of reaching fully fledged protection, unless a vaccine is based on carefully selected peptides and combined with an effective adjuvant.

TLR7 modulating B-cell immune responses in the spleen of C57BL/6 mice infected with Schistosoma japonicum

B cells played an important role in Schistosoma infection-induced diseases. TLR7 is an intracellular member of the innate immune receptor. The role of TLR7 on B cells mediated immune response is still unclear. Here, C57BL/6 mice were percutaneously infected by S. japonicum for 5-6 weeks. The percentages and numbers of B cells increased in the infected mice (p < 0.05), and many activation and function associated molecules were also changed on B cells. More splenic cells of the infected mice expressed TLR7, and B cells were served as the main cell population. Moreover, a lower level of soluble egg antigen (SEA) specific antibody and less activation associated molecules were found on the surface of splenic B cells from S. japonicum infected TLR7 gene knockout (TLR7 KO) mice compared to infected wild type (WT) mice (p < 0.05). Additionally, SEA showed a little higher ability in inducing the activation of B cells from naive WT mice than TLR7 KO mice (p < 0.05). Finally, the effects of TLR7 on B cells are dependent on the activation of NF-κB p65. Altogether, TLR7 was found modulating the splenic B cell responses in S. japonicum infected C57BL/6 mice.

A preliminary investigation into the immune cell landscape of schistosome-associated liver fibrosis in humans

Schistosomiasis is a widespread helminth disease that poses a heavy social and economic burden on people worldwide. Advanced schistosomiasis often develops into schistosome‐associated liver fibrosis, the pathogenesis of which remains unclear. This study aimed preliminarily to profile immune cells of schistosome‐associated liver fibrosis using single‐cell RNA sequencing. Three patient groups were enrolled, including an Schistosomiasis japonicum (SJ) group (n = 1), a chronic liver failure (CLF) group (n = 3) and a healthy control (HC) group (n = 2), revealing 17 cell clusters out of 20 093 cells. From these limited datasets, it was observed that T cell(1), mononuclear phagocytes‐1 and dendritic cells (DCs) were higher in the SJ group. CAVIN2⁺ MP(2) was the predominant cell type in the MP subset of the SJ group (53%), and was higher than that in both the CLF (8%) and HC (1%) groups. Kupffer cell marker genes (CD163, MARCO and TIMD4) were enriched in caveolae‐associated protein 2 (CAVIN2)⁺ MP(2), which was also an important source of TGFB1. The KEGG pathways of CAVIN2⁺ MP(2) indicated that they were associated with lysosome, endocytosis, phagosome and antigen processing and presentation. The preliminary study showed that granzyme B (GZMB)⁺ T cell(1) and ankyrin repeat domain‐containing protein 36B⁺ T cell(3) were the most common T cells in the SJ group (50% and 32%, respectively). The KEGG pathways of GZMB⁺ T cell(1) were mainly related to natural killer cell‐mediated cytotoxicity. The percentage of ring1 and YY1 binding protein (RYBP)⁺ DC(1) was higher in the SJ group (57%) than in the CLF (16%) and HC (6%) groups. The KEGG pathway of RYBP⁺ DC(1) was related to Fc gamma R‐mediated phagocytosis and antigen processing and presentation. Overall, CAVIN2⁺ Kupffer cells were the main source of TGFB1, consisting primarily of mononuclear phagocytes in the livers of the SJ group subjects and potentially playing an irreplaceable role in hepatic fibrosis of schistosomiasis.

Context-dependent roles of B cells during intestinal helminth infection

The current approaches to reduce the burden of chronic helminth infections in endemic areas are adequate sanitation and periodic administration of deworming drugs. Yet, resistance against some deworming drugs and reinfection can still rapidly occur even after treatment. A vaccine against helminths would be an effective solution at preventing reinfection. However, vaccines against helminth parasites have yet to be successfully developed. While T helper cells and innate lymphoid cells have been established as important components of the protective type 2 response, the roles of B cells and antibodies remain the most controversial. Here, we review the roles of B cells during intestinal helminth infection. We discuss the potential factors that contribute to the context-specific roles for B cells in protection against diverse intestinal helminth parasite species, using evidence from well-defined murine model systems. Understanding the precise roles of B cells during resistance and susceptibility to helminth infection may offer a new perspective of type 2 protective immunity.

Schistosomes in the Lung: Immunobiology and Opportunity

Schistosome infection is a major cause of global morbidity, particularly in sub-Saharan Africa. However, there is no effective vaccine for this major neglected tropical disease, and re-infection routinely occurs after chemotherapeutic treatment. Following invasion through the skin, larval schistosomula enter the circulatory system and migrate through the lung before maturing to adulthood in the mesenteric or urogenital vasculature. Eggs released from adult worms can become trapped in various tissues, with resultant inflammatory responses leading to hepato-splenic, intestinal, or urogenital disease – processes that have been extensively studied in recent years. In contrast, although lung pathology can occur in both the acute and chronic phases of schistosomiasis, the mechanisms underlying pulmonary disease are particularly poorly understood. In chronic infection, egg-mediated fibrosis and vascular destruction can lead to the formation of portosystemic shunts through which eggs can embolise to the lungs, where they can trigger granulomatous disease. Acute schistosomiasis, or Katayama syndrome, which is primarily evident in non-endemic individuals, occurs during pulmonary larval migration, maturation, and initial egg-production, often involving fever and a cough with an accompanying immune cell infiltrate into the lung. Importantly, lung migrating larvae are not just a cause of inflammation and pathology but are a key target for future vaccine design. However, vaccine efforts are hindered by a limited understanding of what constitutes a protective immune response to larvae. In this review, we explore the current understanding of pulmonary immune responses and inflammatory pathology in schistosomiasis, highlighting important unanswered questions and areas for future research.

Changing our view of the Schistosoma granuloma to an ecological standpoint

Schistosomiasis, a neglected parasitic tropical disease that has plagued humans for centuries, remains a major public health burden. A primary challenge to understanding schistosomiasis is deciphering the most remarkable pathological feature of this disease, the granuloma - a highly dynamic and self-organized structure formed by both host and parasite components. Granulomas are considered a remarkable example of how parasites evolved with their hosts to establish complex and intimate associations. However, much remains unclear regarding life within the granuloma, and strategies to restrain its development are still lacking. Here we explore current information on the hepatic Schistosoma mansoni granuloma in the light of Ecology and propose that this intricate structure acts as a real ecosystem. The schistosomal granuloma is formed by cells (biotic component), protein scaffolds, fibres, and chemical compounds (abiotic components) with inputs/outputs of energy and matter, as complex as in classical ecosystems. We review the distinct cell populations ('species') within the granuloma and examine how they integrate with each other and interact with their microenvironment to form a multifaceted cell community in different space-time frames. The colonization of the hepatic tissue to form granulomas is explained from the point of view of an ecological succession whereby a community is able to modify its physical environment, creating conditions and resources for ecosystem construction. Remarkably, the granuloma represents a dynamic evolutionary system that undergoes progressive changes in the 'species' that compose its community over time. In line with ecological concepts, we examine the granuloma not only as a place where a community of cells is settled (spatial niche or habitat) but also as a site in which the functional activities of these combined populations occur in an orchestrated way in response to microenvironmental gradients such as cytokines and egg antigens. Finally, we assert how the levels of organization of cellular components in a granuloma as conventionally defined by Cell Biology can fit perfectly into a hierarchical structure of biological systems as defined by Ecology. By rethinking the granuloma as an integrating and evolving ecosystem, we draw attention to the inner workings of this structure that are central to the understanding of schistosomiasis and could guide its future treatment.

Schistosomiasis Morbidity Hotspots: Roles of the Human Host, the Parasite and Their Interface in the Development of Severe Morbidity

Schistosomiasis is the second most important human parasitic disease in terms of socioeconomic impact, causing great morbidity and mortality, predominantly across the African continent. For intestinal schistosomiasis, severe morbidity manifests as periportal fibrosis (PPF) in which large tracts of macro-fibrosis of the liver, visible by ultrasound, can occlude the main portal vein leading to portal hypertension (PHT), sequelae such as ascites and collateral vasculature, and ultimately fatalities. For urogenital schistosomiasis, severe morbidity manifests as pathology throughout the urinary system and genitals, and is a definitive cause of squamous cell bladder carcinoma. Preventative chemotherapy (PC) programmes, delivered through mass drug administration (MDA) of praziquantel (PZQ), have been at the forefront of schistosomiasis control programmes in sub-Saharan Africa since their commencement in Uganda in 2003. However, despite many successes, 'biological hotspots' (as distinct from 'operational hotspots') of both persistent high transmission and morbidity remain. In some areas, this failure to gain control of schistosomiasis has devastating consequences, with not only persistently high infection intensities, but both "subtle" and severe morbidity remaining prevalent. These hotspots highlight the requirement to revisit research into severe morbidity and its mechanisms, a topic that has been out of favor during times of PC implementation. Indeed, the focality and spatially-structured epidemiology of schistosomiasis, its transmission persistence and the morbidity induced, has long suggested that gene-environmental-interactions playing out at the host-parasite interface are crucial. Here we review evidence of potential unique parasite factors, host factors, and their gene-environmental interactions in terms of explaining differential morbidity profiles in the human host. We then take the situation of schistosomiasis mansoni within the Albertine region of Uganda as a case study in terms of elucidating the factors behind the severe morbidity observed and the avenues and directions for future research currently underway within a new research and clinical trial programme (FibroScHot).

New insights into regulatory B cells biology in viral, bacterial, and parasitic infections

B lymphocytes are primarily well known for their contribution to immunity by antibody production, antigen presentation and, the production of cytokines. In recent years several studies demonstrated the existence of B cells with regulatory functions, which have been termed regulatory B cells (B_regs), similar to regulatory T cells (T_regs). B_regs are a subpopulation of B cells that have immunosuppressive effects via the production of regulatory cytokines including interleukin-10 (IL-10), transforming growth factor-β (TGF-β), and IL-35. B_regs limit host defense against various pathogens. In addition, B_regs contribute to increased levels of regulatory cytokines and leads to an induction of suppressive T_regs, which exert broader suppressive functions against various pathogens. The high percentage of B_regs is positively associated with viral and bacterial load and can contribute to poor vaccine responses. B_regs can also facilitate pathogen survival at an early stage of infection, and subsequently cause increased severity of disease by inhibiting pro-inflammatory cytokine production, macrophage activation, and inflammatory T cells activation such as Th1, Th17, and Th22. Also, B_regs afford protection against the hyper-inflammatory response in parasitic infections. Here we review the central role of B_regs in many major bacterial and viral human infections, and provide an overview of the immunoregulatory mechanisms used by B_regs.

Current Understanding of Immunity Against Schistosomiasis: Impact on Vaccine and Drug Development

Schistosomiasis is a neglected tropical disease inflicting significant morbidity in humans worldwide. The disease is caused by infections with a parasitic trematode belonging to the genus Schistosoma. Over 250 million people are currently infected globally, with an estimated disability-adjusted life-years of 1.9 million attributed to the disease. Current understanding, based on several immunological studies using experimental and human models of schistosomiasis, reveals that complex immune mechanisms play off each other in the acquisition of immune resistance to infection/reinfection. Nevertheless, the precise characteristics of these responses, the specific antigens against which they are elicited, and how these responses are intricately regulated are still being investigated. What is apparent is that immunity to schistosome infections develops slowly and over a prolonged period of time, augmented by the death of adult worms occurring naturally or by praziquantel therapy. In this review, aspects of immunity to schistosomiasis, host–parasite interactions and their impact on schistosomiasis vaccine development are discussed.

The associations of hub gene polymorphisms in PI3K/AKT/mTOR pathway and Schistosomiasis Japonica infection and hepatic fibrosis

INTRODUCTION

Increasing evidence shows that the PI3K/AKT/mTOR pathway can be activated by a variety of stimulus in immune cells. Schistosomiasis Japonica is a serious threat to human health in some lakes of China.

METHODS

We analyzed the potential associations between the hub gene (PTEN, mTOR, AKT1 and AKT2) polymorphisms of PI3K/AKT/mTOR pathway and S. japonica risk, including infection risk, as well as immunological hepatic fibrosis risk. An immune database named Database of Immune Cell Expression, Expression quantitative trait loci and Epigenomics (DICE) was used to analyze the expression profiles of the hub genes in 15 types of immune cells.

RESULTS

Of them, two SNPs rs2295080 (mTOR) and rs7254617 (AKT2) were found associated with the risk of infection and fibrosis. We also performed a multivariant Cox regression analysis and found that HBV infection may increase hepatic fibrosis in chronic schistosomiasis patients, instead of genetic polymorphisms on PI3K/AKT/mTOR pathway or any other factors. We also found the expressions of mTOR (RICTOR) and AKT2 in T cells were higher than those in monocyte cells. And, the expressions of PTEN, mTOR (RICTOR) and AKT1 reduced both in activated CD4 T cells and activated CD8 T cells.

CONCLUSIONS

We concluded that rs2295080 may be an important marker in the diagnosis of susceptibility to schistosomiasis infection. But HBV infection not rs2295080 could promote immunological liver damage with fibrosis in patients with chronic schistosomiasis infection.

Behind Enemy Lines: Immunomodulatory Armamentarium of the Schistosome Parasite

The deeply rooted, intricate relationship between the Schistosoma parasite and the human host has enabled the parasite to successfully survive within the host and surreptitiously evade the host's immune attacks. The parasite has developed a variety of strategies in its immunomodulatory armamentarium to promote infection without getting harmed or killed in the battlefield of immune responses. These include the production of immunomodulatory molecules, alteration of membranes, and the promotion of granuloma formation. Schistosomiasis thus serves as a paradigm for understanding the Th2 immune responses seen in various helminthiases. This review therefore aims to summarize the immunomodulatory mechanisms of the schistosome parasites to survive inside the host. Understanding these immunomodulatory strategies not only provides information on parasite-host interactions, but also forms the basis in the development of novel drugs and vaccines against the schistosome infection, as well as various types of autoimmune and inflammatory conditions.

T Lymphocyte-Mediated Liver Immunopathology of Schistosomiasis

The parasitic worms, Schistosoma mansoni and Schistosoma japonicum, reside in the mesenteric veins, where they release eggs that induce a dramatic granulomatous response in the liver and intestines. Subsequently, infection may further develop into significant fibrosis and portal hypertension. Over the past several years, uncovering the mechanism of immunopathology in schistosomiasis has become a major research objective. It is known that T lymphocytes, especially CD4⁺ T cells, are essential for immune responses against Schistosoma species. However, obtaining a clear understanding of how T lymphocytes regulate the pathological process is proving to be a daunting challenge. To date, CD4⁺ T cell subsets have been classified into several distinct T helper (Th) phenotypes including Th1, Th2, Th17, T follicular helper cells (Tfh), Th9, and regulatory T cells (Tregs). In the case of schistosomiasis, the granulomatous inflammation and the chronic liver pathology are critically regulated by the Th1/Th2 responses. Animal studies suggest that there is a moderate Th1 response to parasite antigens during the acute stage, but then, egg-derived antigens induce a sustained and dominant Th2 response that mediates granuloma formation and liver fibrosis. In addition, the newly discovered Th17 cells also play a critical role in the hepatic immunopathology of schistosomiasis. Within the liver, Tregs are recruited to hepatic granulomas and exert an immunosuppressive role to limit the granulomatous inflammation and fibrosis. Moreover, recent studies have shown that Tfh and Th9 cells might also promote liver granulomas and fibrogenesis in the murine schistosomiasis. Thus, during infection, T-cell subsets undergo complicated cross-talk with antigen presenting cells that then defines their various roles in the local microenvironment for regulating the pathological progression of schistosomiasis. This current review summarizes a vast body of literature to elucidate the contribution of T lymphocytes and their associated cytokines in the immunopathology of schistosomiasis.

Type I interferons provide additive signals for murine regulatory B cell induction by Schistosoma mansoni eggs

The helminth Schistosoma mansoni (S. mansoni) induces a network of regulatory immune cells, including interleukin (IL)-10-producing regulatory B cells (Bregs). However, the signals required for the development and activation of Bregs are not well characterized. Recent reports suggest that helminths induce type I interferons (IFN-I), and that IFN-I drive the development of Bregs in humans. We therefore assessed the role of IFN-I in the induction of Bregs by S. mansoni. Mice chronically infected with S. mansoni or i.v. injected with S. mansoni soluble egg antigen (SEA) developed a systemic IFN-I signature. Recombinant IFN-α enhanced IL-10 production by Bregs stimulated with S. mansoni SEA in vitro, while not activating Bregs by itself. IFN-I signaling also supported ex vivo IL-10 production by SEA-primed Bregs but was dispensable for activation of S. mansoni egg-induced Bregs in vivo. These data indicate that although IFN-I can serve as a coactivator for Breg IL-10 production, they are unlikely to participate in the development of Bregs in response to S. mansoni eggs.

B1 cells protect against Schistosoma japonicum-induced liver inflammation and fibrosis by controlling monocyte infiltration

During Schistosoma infection, lack of B cells results in more severe granulomas, inflammation, and fibrosis in the liver, but the mechanisms underlying this pathology remain unclear. This study was to clarify the mechanisms underpinning the immunomodulation of B cells in mice infected with Schistosoma japonicum (S. japonicum). We found that B cell deficiency led to aggravated liver pathology, as demonstrated by increases in the size of the egg-associated granulomas, alanine transaminase levels, and collagen deposition. Compared with infected wild-type (WT) mice, infected B cell-deficient (μMT) mice showed increased infiltration of Ly6C^hi monocytes and higher levels of proinflammatory cytokines and chemokines. Furthermore, B1 cells were increased significantly in the liver of WT mice following S. japonicum infection. Adoptively transferring B1 cells, but not B2 cells, to μMT mice significantly reduced liver pathology and liver infiltration of Ly6C^hi monocytes. Additionally, secretion of IL-10 from hepatic B cells increased significantly in infected WT mice and this IL-10 was mainly derived from B1 cells. Adoptively transferring B1 cells purified from WT mice, but not from IL-10-deficient mice, to μMT mice significantly reduced liver pathology and liver infiltration of Ly6C^hi monocytes. These reductions were accompanied by decreases in the expression levels of chemokines and inflammatory cytokines. Taken together, these data indicated that after S. japonicum infection, an increased number of hepatic B1 cells secrete IL-10, which inhibits the expression of chemokines and cytokines and suppresses the infiltration of Ly6C^hi monocytes into the liver thereby alleviating liver early inflammation and late fibrosis.

Infection with Schistosoma results in strong granulomatous inflammation caused by parasite eggs deposited in the liver. Granuloma is defined as a significant number of immune cell infiltration around the eggs intermixed with hepatocytes, which can protect the host against liver damage. But excessive infiltration and inflammation lead to severe liver injury and fibrosis. Here we found that B1 cells accumulated in the liver after infection and released IL-10 to regulate inflammation. B1 cell-derived IL-10 inhibited the expression of chemokines and then restrained excessive infiltration of Ly6C^hi monocytes into the liver thereby alleviating early inflammation and later fibrosis in the liver. Our study provides insight into the immunomodulation of B1 cells in schistosomiasis and an important step towards the development of therapeutic strategies for Schistosoma-induced liver diseases.

Interleukin-4 Receptor Alpha Expressing B Cells Are Essential to Down-Modulate Host Granulomatous Inflammation During Schistosomasis

Schistosomiasis (bilharzia) is a parasitic helminth disease that can cause severe inflammatory pathology leading to organ damage in humans. Failure of the host to regulate egg-driven granulomatous inflammation causes host morbidity during chronic infection with Schistosoma mansoni. Although the importance of B cells in regulating pathology during chronic infection has been well defined, the specific contribution of IL-4Rα-expressing B cells is still unknown. To address this, we examined B cell-specific IL-4Rα-deficient (mb1^creIL-4Rα^−/lox) mice in three experimental models of schistosomiasis: high-dose (100 cercariae), low dose (30 cercariae), and a synchronous egg challenge. In the high dose model, we found that mice deficient in IL-4Rα-expressing B cells were more susceptible to acute schistosomiasis than B cell-deficient (μMT) mice, succumbing to infection at the acute stage whereas μMT mice survived until the chronic stage. An S. mansoni egg challenge model demonstrated that deleting IL-4Rα expression specifically on B cells resulted in increased lung granulomatous pathology, suggesting a role for this B cell subset in controlling granulomatous pathology. In agreement with this, a low dose model of schistosomiasis—which mimics the course of clinical chronic disease—demonstrated that depleting IL-4Rα-expressing B cells in mb1^creIL-4Rα^−/lox mice considerably impaired the host ability to down-modulate granulomatous inflammation in the liver and gut during chronic schistosomiasis. Taken together, our findings indicate that within the B cell compartment, IL-4Rα-expressing B cells in particular down-modulate the deleterious egg-driven tissue granulomatous inflammation to enable host survival during schistosomiasis in mice.

IL-4Rα-expressing CD11c+ cells contribute to driving optimal cellular responses during Schistosoma mansoni infection in mice

Development of IL‐4 receptor alpha (IL‐4Rα)‐dependent cellular immunity regulates host protection against acute schistosomiasis. In this study, we investigated the importance of IL‐4Rα‐expressing CD11c⁺ cells in driving the development of optimal cellular responses to Schistosoma mansoni infection by using CD11c^creIL‐4Rα^−/lox BALB/c mice, which lacked IL‐4Rα expression on dendritic cells and alveolar macrophages. Abrogation of IL‐4Rα expression on CD11c⁺ cells affected activation of CD4⁺ T cells, resulting in reduced numbers of effector CD4⁺ T cells and impaired production of Th1 and Th2 cytokines by CD4⁺ T cells ex vivo. However, secretion of both type 1 and type 2 Ab isotypes was unchanged in infected CD11c‐specific IL‐4Rα‐deficient mice compared to littermate controls. Together, these data demonstrate that IL‐4Rα‐expressing CD11c⁺ cells play an important role in maintaining cellular immunity during schistosomiasis in mice.

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

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

IL-4-producing B cells regulate T helper cell dichotomy in type 1- and type 2-controlled diseases

Interleukin-4 (IL-4)-induced T helper (Th) 2 cells promote susceptibility to the protozoan parasite Leishmania major, while conferring immunity to the intestinal trematode Schistosoma mansoni Here, we report that abrogation of IL-4 receptor alpha (IL-4Rα) signaling on B cells in BALB/c mice (mb1^creIL-4Rα^-/lox) transformed nonhealer BALB/c to a healer phenotype with an early type 1 and dramatically reduced type 2 immune response and an absence of ulceration and necrosis during cutaneous leishmaniasis. From adoptive reconstitution and mixed bone-marrow chimera studies in B cell-deficient (µMT) mice, we reveal a central role for B cell-derived IL-4 and IL-4Rα in the optimal induction of the susceptible type 2 phenotype to L. major infection. We further demonstrate that the absence of IL-4Rα signaling on B cells exacerbated S. mansoni-induced mortality and pathology in BALB/c mice, due to a diminished type 2 immune response. In both disease models, IL-4Rα-responsive B cells displayed increased IL-4 production as early as day 1 after infection. Together, these results demonstrate that IL-4-producing and IL-4Rα-responsive B cells are critical in regulating and assisting early T helper dichotomy toward Th2 responses, which are detrimental in cutaneous leishmaniasis but beneficial in acute schistosomiasis.

Characteristics of Schistosoma japonicum infection induced IFN-γ and IL-4 co-expressing plasticity Th cells

Schistosoma japonicum infection can induce granulomatous inflammation and cause tissue damage in the mouse liver. The cytokine secretion profile of T helper (Th) cells depends on both the nature of the activating stimulus and the local microenvironment (e.g. cytokines and other soluble factors). In the present study, we found an accumulation of large numbers of IFN-γ(+)  IL-4(+)  CD4(+) T cells in mouse livers. This IFN-γ(+)  IL-4(+) cell population increased from 0·68 ± 0·57% in uninfected mice to 7·05 ± 3·0% by week 4 following infection and to 9·6 ± 5·28% by week 6, before decreasing to 6·3 ± 5·9% by week 8 in CD4 T cells. Moreover, IFN-γ(+)  IL-4(+) Th cells were also found in mouse spleen and mesenteric lymph nodes 6 weeks after infection. The majority of the IFN-γ(+)  IL-4(+) Th cells were thought to be related to a state of immune activation, and some were memory T cells. Moreover, we found that these S. japonicum infection-induced IFN-γ(+)  IL-4(+) cells could express interleukin-2 (IL-2), IL-9, IL-17 and high IL-10 levels at 6 weeks after S. japonicum infection. Taken together, our data suggest the existence of a population of IFN-γ(+)  IL-4(+) plasticity effector/memory Th cells following S. japonicum infection in C57BL/6 mice.

Enhanced inflammatory cell profiles in schistosomiasis-induced pulmonary vascular remodeling

Schistosomiasis (bilharzia) is a neglected parasitic disease caused by trematode flatworms of the genus Schistosoma which affects over 240 million people worldwide. It is characterized by the formation of inflammatory granulomas around deposited parasite eggs. Recent studies have revealed that immune and inflammatory responses play a crucial role in pathogenesis of schistosomiasis. The aim of this paper is to systematically evaluate the number and distribution of inflammatory cells in S. mansoni-infected mice at different doses and time points. Immunohistochemistry was performed on lung and liver tissue sections from Schistosoma-infected mice and uninfected healthy controls. Positively stained cells in whole-lung/liver tissue sections, surrounding the eggs, and in the different compartments of the tissues, were counted. We found a significant increase in the number of mast cells (toluidine blue⁺), CD3⁺ cells, CD14⁺ cells, CD68⁺ cells, and CD15⁺ cells in Schistosoma-infected tissues compared with untreated healthy controls (P ≤ 0.05 for all). Our findings revealed altered and enhanced immune cell infiltration in schistosomiasis. We suggest that these cells may contribute to the pathophysiology of Schistosoma resulting in pulmonary vascular remodeling.

IgE and mast cells in host defense against parasites and venoms

IgE-dependent mast cell activation is a major effector mechanism underlying the pathology associated with allergic disorders. The most dramatic of these IgE-associated disorders is the fatal anaphylaxis which can occur in some people who have developed IgE antibodies to otherwise innocuous antigens, such as those contained in certain foods and medicines. Why would such a highly "maladaptive" immune response develop in evolution and be retained to the present day? Host defense against parasites has long been considered the only beneficial function that might be conferred by IgE and mast cells. However, recent studies have provided evidence that, in addition to participating in host resistance to certain parasites, mast cells and IgE are critical components of innate (mast cells) and adaptive (mast cells and IgE) immune responses that can enhance host defense against the toxicity of certain arthropod and animal venoms, including enhancing the survival of mice injected with such venoms. Yet, in some people, developing IgE antibodies to insect or snake venoms puts them at risk for having a potentially fatal anaphylactic reaction upon subsequent exposure to such venoms. Delineating the mechanisms underlying beneficial versus detrimental innate and adaptive immune responses associated with mast cell activation and IgE is likely to enhance our ability to identify potential therapeutic targets in such settings, not only for reducing the pathology associated with allergic disorders but perhaps also for enhancing immune protection against pathogens and animal venoms.

B10 cells induced by Schistosoma japonicum soluble egg antigens modulated regulatory T cells and cytokine production of T cells

A distinct subset of B cells, also known as regulatory B cells, can negatively regulate T cell immune responses, but the role of these cells in schistosomiasis has not been clarified. Soluble egg antigen (SEA) and soluble adult worm antigen preparation (SWAP), which are two important antigen sources during Schistosoma japonicum infection, both can induce Th1, Th2, Th17, and Treg cells and the corresponding cytokines. However, whether they can induce the production of regulatory B cells and the regulatory function of schistosome-induced regulatory B cells remains unclear. In our studies, we first analyzed the production of regulatory B cells stimulated by SEA or SWAP using flow cytometry and enzyme-linked immunosorbent assay, and observed these cells in mice immunized by SEA or SWAP. Then, B10 cells sorted by MicroBeads were co-cultured with CD4(+) T cells, and the proportion of Treg cells were detected. At the same time, the IFN-γ, IL-4, and IL-17 levels in the culture supernatant were measured. The results showed that B10 cells were preferentially induced by SEA in vitro, and B10 could also be induced in mice immunized by SEA. SEA-induced B10 cells promoted the expansion of regulatory T cells and induced IL-4 secretion, but inhibited IL-17 production. These findings reveal that the generation of B10 cells is determined by parasitic antigen, and suggest the function of B10 cell induced by SEA. This study significantly contributes to the understanding of the immune regulatory role in schistosomiasis and may help protect hosts from infection.

Cutaneous granulomas in the setting of primary immunodeficiency: a report of four cases and review of the literature

IMPORTANCE

Cutaneous granulomas without an identifiable infectious etiology are a rare manifestation of primary immunodeficiency (ID). These cutaneous lesions can be misdiagnosed, often as sarcoidosis, when the skin findings precede the diagnosis of immunodeficiency.

OBJECTIVE

We present four cases from our institution and review the literature in order to emphasize the clinical relevance of this association, discuss the histologic and immunohistochemical features, and explore possible pathogenic mechanisms of granuloma formation.

EVIDENCE REVIEW

We retrospectively reviewed case reports of all patients presenting with cutaneous granulomas in the setting of primary immunodeficiency. Cases with insufficient information to confirm an immunodeficiency state were excluded. Four patients from our clinic were included, for 54 total cases.

FINDINGS

The majority of cutaneous granulomas are seen in three types of immunodeficiencies: ataxia-telangiectasia, severe combined immunodeficiency, and combined variable immunodeficiency. Twenty-six percent of patients developed cutaneous granulomas prior to their immunodeficiency diagnosis. Histologically, various granulomatous patterns have been described. Immunohistochemistry revealed a CD4+/CD8+ lymphocyte ratio of less than or equal to 1 in our four patients, which may help differentiate cutaneous granulomas in primary ID from sarcoidal granulomas that typically show a CD4+ predominance.

CONCLUSIONS AND RELEVANCE

Cutaneous granulomas are a rare manifestation of primary ID and occur predominantly in immunodeficiencies that affect T and B cell compartments.

B Cells with Regulatory Function in Animal Models of Autoimmune and Non-Autoimmune Diseases

Although the identification of B cell subsets with negative regulatory functions and the definition of their mechanisms of action are recent events, the important negative regulatory roles of B cells in immune responses are now broadly recognized. There is an emerging appreciation for the pivotal role played by B cells in several areas of human diseases including autoimmune diseases and non-autoimmune diseases such as parasite infections and cancer. The recent research advancement of regulatory B cells in human disease coincides with the vastly accelerated pace of research on the bridging of innate and adaptive immune system. Current study and our continued research may provide better understanding of the mechanisms that promote regulatory B10 cell function to counteract exaggerated immune activation in autoimmune as well as non-autoimmune conditions. This review is focused on the current knowledge of BREG functions studied in animal models of autoimmune and non-autoimmune diseases.

CD16 expression on monocytes in healthy individuals but not schistosome-infected patients is positively associated with levels of parasite-specific IgG and IgG1

Human IgG1 antibody responses are associated with protection against Schistosoma haematobium infection and are now a target for schistosome vaccine development. This study aimed to investigate the relationship between total IgG and the IgG subclasses and the monocyte IgG receptor, known as FcγRIIIa or CD16, in schistosome exposed people. Systemic levels of schistosome-specific anti-adult worm total IgG and IgG subclass titres were measured by ELISA in 100 individuals from an S. haematobium endemic area in Zimbabwe and, using parametric statistical methods and regression analysis, related to the levels of CD16 expression on individuals' circulating monocytes, determined via flow cytometry. Monocyte CD16 expression rose with parasite-specific total IgG and IgG1 in healthy participants, but not in schistosome infected patients. Similar to parasite-specific IgG and IgG1, CD16 expression in healthy individuals is associated with protection against schistosome infection. This relationship indicates a mechanistic link between the innate and adaptive immune responses to helminth infection in protection against infection. Further understanding the elements of a protective immune response in schistosomiasis may aid in efforts to develop a protective vaccine against this disease.

Schistosomiasis is a parasitic disease caused by the parasite Schistosoma spp. Over 240 million people are infected worldwide, mainly in Sub-Saharan Africa, but an efficacious, protective vaccine has yet to be found. Protection against schistosome infection in individuals living in endemic areas is mediated by antibodies. In particular, IgG1 antibody has been shown to be protective against infection in individuals living in endemic areas, and eliciting IgG1 production has become a cornerstone of vaccine development efforts. However, little is known about the mechanisms by which IgG1 induces protection. The cell surface molecule CD16 is an IgG antibody receptor expressed on monocytes and binds preferentially to IgG antibody subclasses. The work presented here thus investigates the relationship between IgG levels and the monocyte CD16 receptor in a population endemically exposed to infection with schistosomes. We present results linking CD16 expression with IgG1 levels, whereby uninfected individuals have a positive relationship between IgG1 and CD16 expression levels, while schistosome infected individuals did not show any statistically significant relationship between the two. Thus we provide evidence to suggest a mechanistic link between the innate and adaptive immune response in parasitic infection, associating monocyte CD16 expression with a protective immune response.

P selectins and immunological profiles in HCV and Schistosoma mansoni induced chronic liver disease

Background

Hepatitis C virus (HCV) and Schistosoma mansoni are major causes of chronic liver disease (CLD) in which immune alteration is common. Recent studies suggested that certain platelets and lymphocytes activation markers may have an impact on progression of CLD. This study aimed to evaluate the potential of platelets and lymphocytes activation molecules expression on the pathogenesis of CLD in distinct or concomitant chronic HCV and schistosomiasis mansoni infections.

Methods

The study populations were divided into group-I: patients with chronic schistosomiasis mansoni, group-II: HCV patients without cirrhosis, group-III: patients with combined liver diseases without cirrhosis, group-IV: patients with chronic HCV and liver cirrhosis and group-V: Age and sex matched healthy individuals as normal controls. All groups were subjected to full clinical evaluation, ELISA anti-HCV antibodies screening, parasitological examination for diagnosing S. mansoni and flow cytometry for lymphocyte (CD3, CD4, CD8, CD19, CD22, & CD56) and platelets activation (CD41, CD42 & CD62P (P- selectins)) markers.

Results

The platelet count was significantly decreased in HCV and/or S. mansoni patients. The total T-lymphocytes and T-helper cells were significantly reduced, while T-cytotoxics were increased. The patients possessed a significantly higher platelets activation marker; CD62P (P-selectins) and higher mean fluorescent intensity (MFI) positivity. There were considerable correlations between platelets count and both of CD62P and MFI.

Conclusion

Our Findings suggest an increased expression of certain platelets and lymphocytes activation markers in chronic HCV and S. mansoni induced CLD that may have a role in disease progression.

P selectin and T cell profiles provide verification to understand the pathogenesis of liver cirrhosis in HCV and Schistosoma mansoni infections

Hepatitis C virus (HCV) and Schistosoma mansoni are two major causes of chronic liver disease (CLD). Both immune alteration and thrombocytopenia are common complications in the majority of cirrhotic patients. The current study aimed to monitor the effect of T cell profile and platelets activation on the pathogenesis of liver cirrhosis in patients suffered from single or concomitant schistosomiasis and HCV infections. The subjects were divided into 4 groups: Group I, patients infected with schistosomiasis; Group II, patients infected with HCV; Group III, patients with combined liver diseases and Group IV: healthy individuals. All groups were subjected to full clinical evaluation as well as laboratory examination including ELISA anti-HCV antibodies screening, parasitological examination, and complete blood picture as well as flow cytometry for CD41, CD42, CD62P (P selectin), CD63, CD4 and CD8. The platelets count was significantly decreased in HCV and/or schistosoma infected patients compared to controls. The percentage of the total T-lymphocytes and T-helper was significantly reduced in all infected groups, while the percentage of T-cytotoxic was increased. The patients possessed a significantly higher percentage of the platelets activation markers than control group. There were considerable correlations between the platelets counts and P selectin and MFI. Thrombocytopenia was a common finding in patients with CLD. Patients with CLD showed increased platelets activation which may contribute to the occurrence of thrombocytopenia and play a role in the pathogenesis of CLD. Infected patient showed reduction in the cell-mediated-immunity as evidenced by low T -helper cells.

Follicular helper T cells promote liver pathology in mice during Schistosoma japonicum infection

Following Schistosoma japonicum (S. japonicum) infection, granulomatous responses are induced by parasite eggs trapped in host organs, particular in the liver, during the acute stage of disease. While excessive liver granulomatous responses can lead to more severe fibrosis and circulatory impairment in chronically infected host. However, the exact mechanism of hepatic granuloma formation has remained obscure. In this study, we for the first time showed that follicular helper T (Tfh) cells are recruited to the liver to upregulate hepatic granuloma formation and liver injury in S. japonicum-infected mice, and identified a novel function of macrophages in Tfh cell induction. In addition, our results showed that the generation of Tfh cells driven by macrophages is dependent on cell–cell contact and the level of inducible costimulator ligand (ICOSL) on macrophages which is regulated by CD40–CD40L signaling. Our findings uncovered a previously unappreciated role for Tfh cells in liver pathology caused by S. japonicum infection in mice.

Schistosomiasis is a chronic helminthic disease that affects approximately 200 million people. After S. japonicum infection, parasite eggs are trapped in host liver and granulomas are induced to form around eggs. Severe granuloma subsequently results in serious liver fibrosis and circulatory impairment chronically. It is important to fully elucidate the mechanism of the granuloma formation. Here, we show that Tfh cells play a novel role of promoting the hepatic granuloma formation and liver injury, and identified a novel function of macrophages in Tfh cells induction in S. japonicum-infected mouse model. In addition, we show that the generation of Tfh cells driven by macrophages is cell–cell contact dependent and regulated by CD40-CD40L signaling. Our findings revealed a novel role and mechanism of macrophages in Tfh cell generation and the liver pathogenesis in S. japonicum-infected mouse model.

Association of Schistosoma mansoni-specific IgG and IgE antibody production and clinical schistosomiasis status in a rural area of Minas Gerais, Brazil

Background

Studies in murine models and human populations have indicated that the collagen-rich granulomatous response against parasite eggs trapped in the liver is associated with the development of severe hepatosplenic schistosomiasis, characterized by periportal fibrosis and portal hypertension. The role of the humoral response in parasite susceptibility has been well established, but its participation in disease severity remains poorly understood. In this work, we evaluated the relationship between parasite-reactive IgE and IgG levels and schistosomiasis morbidity in infected patients with similar parasite burdens.

Methodology/Principal Findings

Ninety-seven Schistosoma mansoni-infected individuals were subjected to clinical examination and abdominal ultrasound analysis. IgG reactivity and IgE concentration against Schistosoma mansoni soluble egg antigens (SEA) and adult worm antigen preparation (SWAP) were evaluated by ELISA assay. Multivariable linear regression models were used to evaluate the relationship between parasite-reactive antibodies and the co-variables investigated. The study population showed low parasite burden (median 30 eggs/g feces), constant re-infection, and signs of fibrosis was detected in more than 30% of individuals. Most infected individuals showed IgG reactivity, and the median concentrations of IgE anti-SEA and anti-SWAP antibodies were 1,870 and 1,375 ng/mL, respectively. There was no association between parasite burden and antibody response or any parameter of disease severity. However, IgG anti-SWAP level was positively associated with morbidity parameters, such as spleen size and thickness of portal vein at the entrance and secondary branch. In contrast, the data also revealed independent inverse correlations between concentration of parasite-reactive IgE and gallbladder wall thickness, a marker of fibrosis in schistosomiasis.

Conclusions/Significance

The data indicate that IgG anti-SWAP is positively associated with severe schistosomiasis, independently of parasite burden, while high production of parasite-specific IgE is associated with mild disease in the human population. Antibody profiles are good correlates for schistosomiasis severity and could be tested as biomarkers of disease severity.

Regulation of the development of the hepatic B cell compartment during Schistosoma mansoni infection

During infection with the helminth parasite Schistosoma mansoni, Ab regulates hepatic inflammation, and local production of Ig in the liver appears to play a role in this process. Exploring the development of the B cell response during infection, we found that parasite-specific IgG1-secreting plasma cells appeared first in the hepatic and mesenteric lymph nodes (LNs) and then at later times in the spleen, liver, and bone marrow. The LN B cell population peaked between weeks 10 and 12 of infection, and then contracted at a time that coincided with the expansion of the hepatic IgG1(+) B cell compartment, suggesting that B cells migrate from LNs to liver. CXCL9 and -16 expression in the liver increased during the time frame of B cell recruitment. Expression of the CXCL16 receptor CXCR6 was increased on B cells within the hepatic LNs, but not the mesenteric LNs. CXCR3, the receptor for CXCL9, was broadly expressed on IgG1(+) B cells in LNs and liver during infection. Increased hepatic expression of CXCL9 and -16 failed to occur if the IL-10R was blocked in vivo, an intervention associated with decreased liver B cell infiltration and the development of severe disease. Hepatic LN IgG1(+) cells migrated toward CXCL9 and -16 in vitro and to the liver in a pertussis toxin-sensitive fashion. Our data suggest that the coordinated expression of CXCL9 and -16 in the liver and of CXCR6 and CXCR3 on responding B cells within the hepatic LNs underpins establishment of the hepatic B cell infiltrate during chronic schistosomiasis.

The schistosoma granuloma: friend or foe?

Infection of man with Schistosoma species of trematode parasite causes marked chronic morbidity. Individuals that become infected with Schistosomes may develop a spectrum of pathology ranging from mild cercarial dermatitis to severe tissue inflammation, in particular within the liver and intestines, which can lead to life threatening hepatosplenomegaly. It is well established that the etiopathology during schistosomiasis is primarily due to an excessive or unregulated inflammatory response to the parasite, in particular to eggs that become trapped in various tissue. The eggs forms the foci of a classical type 2 granulomatous inflammation, characterized by an eosinophil-rich, CD4⁺ T helper (Th) 2 cell dominated infiltrate with additional infiltration of alternatively activated macrophages (M2). Indeed the sequela of the type 2 perioval granuloma is marked fibroblast infiltration and development of fibrosis. Paradoxically, while the granuloma is the cause of pathology it also can afford some protection, whereby the granuloma minimizes collateral tissue damage in the liver and intestines. Furthermore, the parasite is exquisitely reliant on the host to mount a granulomatous reaction to the eggs as this inflammatory response facilitates the successful excretion of the eggs from the host. In this focused review we will address the conundrum of the S. mansoni granuloma acting as both friend and foe in inflammation during infection.

Some characteristics of IL-5-producing T cells in mouse liver induced by Schistosoma japonicum infection

Schistosome infection could cause significant liver damage in animal; Th2 cells play an important role in the progress of this disease. In our study, C57BL/6 mice were infected by Schistosoma japonicum and lymphocytes were isolated from the liver to detect some characteristics of interleukin-5 (IL-5)-producing T cells by different methods. The results revealed that S. japonicum infection could induce a large amount of IL-5 in mouse liver T cells by the means of fluorescent bead immunoassay and RT-PCR. Although, mouse liver contained many T cell subsets, such as Th cells, Tc cells, NKT cells, and γδ T cells. Fluorescence activated cell sorting results indicated that Th cells were the main source of IL-5 in the T cell population after phorbol 12-myristate 13-acetate and ionomycin stimulation. Moreover, the percentage of IL-5-producing Th cells continued to increase from 4 to 8 weeks after S. japonicum infection, which differed from the changes of IFN-γ(+) Th1 cells, IL-4(+) Th2 cells, and IL-17A(+) Th17 cells during S. japonicum infection. Additionally, cytokines co-expression results demonstrated that 36.2 % of IL-5(+) Th cells could express IL-4, and 10 % of it could produce IFN-γ or IL-17A. Collectively, these findings implied that IL-5-producing Th cells posses some properties which differ from other cytokines secreting Th cells.

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.

Development of adult worms and granulomatous pathology are collectively regulated by T- and B-cells in mice infected with Schistosoma japonicum

Schistosoma blood flukes, which cause schistosomiasis affecting 200 million people in the world, are dependent on signals from host CD4⁺ T cells to facilitate parasite growth and development in the mammalian host and to induce Th2-biased inflammatory granulomas. B cells, however, are reported to down-regulate granulomatous pathology in schistosomiasis, but not to affect the development of blood flukes together with CD4⁺ T lymphocytes. Thus it is not clear whether B cells mediate parasite development, reproduction and egg granuloma formation of schistosomes without the help of CD4⁺ T lymphocytes. Using mice that have severe combined immunodeficiency (scid) and mice lacking T cells (nude), we found that the absence of B cells can more seriously hamper the development and paring of adult worms, but granuloma formation of Schistosoma japonicum in scid mice was not down-regulated comparing with that in nude mice. The level of IL-10 in the sera of nude mice was significantly higher than of scid mice at 43 days post infection (p.i.). Thus multiple mechanisms of immune modulation seem to be involved in parasite development and reproduction by helminth-induced regulatory B cells. Our findings have significance for understanding the molecular connections between schistosomes and T- and B-cells, indicating that more research is needed to develop efficient vaccine-based therapies for schistosomiasis.

Emerging trends in the formation and function of tuberculosis granulomas

The granuloma is an elaborated aggregate of immune cells found in non-infectious as well as infectious diseases. It is a hallmark of tuberculosis (TB). Predominantly thought as a host-driven strategy to constrain the bacilli and prevent dissemination, recent discoveries indicate the granuloma can also be modulated into an efficient tool to promote microbial pathogenesis. The aim of future studies will certainly focus on better characterization of the mechanisms driving the modulation of the granuloma functions. Here, we provide unique perspectives from both the innate and adaptive immune system in the formation and the role of the TB granuloma. As macrophages (Mϕs) comprise the bulk of granulomas, we highlight the emerging concept of Mϕ polarization and its potential impact in the microbicide response, and other activities, that may ultimately shape the fate of granulomas. Alternatively, we shed light on the ability of B-cells to influence inflammatory status within the granuloma.

Th2 responses in schistosomiasis

Schistosomiasis is caused by infection with parasitic flatworms of the genus Schistosoma. It is characterized by the development of strong CD4(+) T cell and B cell responses that, during primary infection, fail to eliminate the parasites, but in collaboration with cells of the innate immune system allow survival in the face of ongoing tissue damage caused by the lodging of parasite eggs in the liver and the passage of eggs across the intestinal epithelium. Mounting a tightly controlled Th2 response is key to this outcome, and while this type of response is a risk factor for the development of fibrosis, it also underpins the development of resistance to further infection; as such, understanding how Th2 responses are induced and regulated in schistosomiasis remains a critical area of research.

Immunity to the model intestinal helminth parasite Heligmosomoides polygyrus

Heligmosomoides polygyrus is a natural intestinal parasite of mice, which offers an excellent model of the immunology of gastrointestinal helminth infections of humans and livestock. It is able to establish long-term chronic infections in many strains of mice, exerting potent immunomodulatory effects that dampen both protective immunity and bystander reactions to allergens and autoantigens. Immunity to the parasite develops naturally in some mouse strains and can be induced in others through immunization; while the mechanisms of protective immunity are not yet fully defined, both antibodies and a host cellular component are required, with strongest evidence for a role of alternatively activated macrophages. We discuss the balance between resistance and susceptibility in this model system and highlight new themes in innate and adaptive immunity, immunomodulation, and regulation of responsiveness in helminth infection.

Schistosomes induce regulatory features in human and mouse CD1d(hi) B cells: inhibition of allergic inflammation by IL-10 and regulatory T cells

Chronic helminth infections, such as schistosomes, are negatively associated with allergic disorders. Here, using B cell IL-10-deficient mice, Schistosoma mansoni-mediated protection against experimental ovalbumin-induced allergic airway inflammation (AAI) was shown to be specifically dependent on IL-10-producing B cells. To study the organs involved, we transferred B cells from lungs, mesenteric lymph nodes or spleen of OVA-infected mice to recipient OVA-sensitized mice, and showed that both lung and splenic B cells reduced AAI, but only splenic B cells in an IL-10-dependent manner. Although splenic B cell protection was accompanied by elevated levels of pulmonary FoxP3(+) regulatory T cells, in vivo ablation of FoxP3(+) T cells only moderately restored AAI, indicating an important role for the direct suppressory effect of regulatory B cells. Splenic marginal zone CD1d(+) B cells proved to be the responsible splenic B cell subset as they produced high levels of IL-10 and induced FoxP3(+) T cells in vitro. Indeed, transfer of CD1d(+) MZ-depleted splenic B cells from infected mice restored AAI. Markedly, we found a similarly elevated population of CD1d(hi) B cells in peripheral blood of Schistosoma haematobium-infected Gabonese children compared to uninfected children and these cells produced elevated levels of IL-10. Importantly, the number of IL-10-producing CD1d(hi) B cells was reduced after anti-schistosome treatment. This study points out that in both mice and men schistosomes have the capacity to drive the development of IL-10-producing regulatory CD1d(hi) B cells and furthermore, these are instrumental in reducing experimental allergic inflammation in mice.

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.

Modulation of specific and allergy-related immune responses by helminths

Helminths are master regulators of host immune responses utilising complex mechanisms to dampen host protective Th2-type responses and favour long-term persistence. Such evasion mechanisms ensure mutual survival of both the parasite and the host. In this paper, we present recent findings on the cells that are targeted by helminths and the molecules and mechanisms that are induced during infection. We discuss the impact of these factors on the host response as well as their effect in preventing the development of aberrant allergic inflammation. We also examine recent findings on helminth-derived molecules that can be used as tools to pinpoint the underlying mechanisms of immune regulation or to determine new anti-inflammatory therapeutics.

B-cell depleting agents for ANCA vasculitides: a new therapeutic approach

Vasculitides associated with anti-neutrophil cytoplasmic antibody (ANCA) serum positivity affecting small and medium-sized vessels are defined as ANCA-associated vasculitis (AAV). Glomerulonephritis in AAV is characterized by focal necrosis, crescent formation, and few or no immunoglobulin deposits. In vitro and animal evidence suggests that ANCA play a pathogenic role in AAV. Specific gene expression signatures are reported to predict long-term prognosis in AAV, suggesting the possibility of individualizing therapy and identifying new therapeutic targets. Although immunosuppressants and glucocorticoids are the cornerstone of AAV therapy, results from two recent randomized controlled trials have shown the non-inferiority of rituximab, compared with cyclophosphamide, for the induction of remission in patients with severe AAV. In fact, in April 2011, the US Food and Drug Administration (FDA) approved rituximab, combined with glucocorticoids, as a front-line therapy for adult patients with granulomatosis with polyangiitis (GPA; Wegener's granulomatosis) or microscopic polyangiitis. This new indication for rituximab provided the first ever FDA-approved therapy for these two diseases and the first alternative to cyclophosphamide for the treatment of severe disease in almost 40years. However, issues regarding the use of maintenance therapy after rituximab, the concurrent use of cyclophosphamide and the toxicity of rituximab remain unanswered and should be clarified in ongoing and future randomized controlled trials.