WARREN KS: MILD PROLONGED SCHISTOSOMIASIS IN MICE: ALTERATIONS IN HOST RESPONSE WITH TIME AND THE DEVELOPMENT OF PORTAL FIBROSIS

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.

Aluminum Adjuvant-Containing Vaccines in the Context of the Hygiene Hypothesis: A Risk Factor for Eosinophilia and Allergy in a Genetically Susceptible Subpopulation?

There are similarities between the immune response following immunization with aluminum adjuvants and the immune response elicited by some helminthic parasites, including stimulation of immunoglobulin E (IgE) and eosinophilia. Immunization with aluminum adjuvants, as with helminth infection, induces a Th2 type cell mediated immune response, including eosinophilia, but does not induce an environment conducive to the induction of regulatory mechanisms. Helminths play a role in what is known as the hygiene hypothesis, which proposes that decreased exposure to microbes during a critical time in early life has resulted in the increased prevalence and morbidity of asthma and atopic disorders over the past few decades, especially in Western countries. In addition, gut and lung microbiome composition and their interaction with the immune system plays an important role in a properly regulated immune system. Disturbances in microbiome composition are a risk factor for asthma and allergies. We propose that immunization with aluminum adjuvants in general is not favorable for induction of regulatory mechanisms and, in the context of the hygiene hypothesis and microbiome theory, can be viewed as an amplifying factor and significant contributing risk factor for allergic diseases, especially in a genetically susceptible subpopulation.

Schistosoma mansoni-Associated Morbidity among Preschool-Aged Children along the Shores of Lake Victoria in Uganda

Schistosoma mansoni causes morbidity in human beings, with the highest prevalence in rural sub-Saharan Africa. Prolonged S. mansoni infection with egg deposition in intestinal blood vessels leads to liver and spleen enlargement, and thus chronic morbidity. The objective of this study was to assess whether preschool-aged children develop severe S. mansoni-related morbidity. Parasitological, clinical, and ultrasonographic examinations were carried out in 916 preschool-aged children in five schistosomiasis-endemic districts (Bugiri, Buikwe, Jinja, Mayuge, and Namayingo) along the Lake Victoria shoreline in east-central Uganda. Anaemia and anthropometry measurements were also taken. Using the Kato-Katz technique on one stool sample collected on three consecutive days, 74.9% (686/916) were found infected with S. mansoni; the majority were lightly infected (57.9%), while 22.7% and 19.4% were moderately and heavily infected, respectively. The overall geometric mean intensity (GMI) of infected children was 294.2 eggs per gram faeces. Mayuge and Jinja districts had the highest (51.2%) and lowest (2.2%) number of infected children, respectively. Hookworm infection was found in 7.8% (71/916) of the children. Both liver and spleen were significantly more enlarged in the infected children than in the uninfected children (p < 0.0005), as measured by ultrasonography. Physical palpation of the spleen was more often detected in the uninfected children. A significantly (p < 0.0005) higher proportion of S. mansoni-positive children were anaemic (359/686; 52.3%) compared to the children who had no eggs in their stool samples (81/230; 35.2%). Schistosoma mansoni infection did not have any severe effect on the nutrition status of preschool-aged children. Neither infected nor uninfected children were found to be underweight or stunted. Liver fibrosis with distinct Symmer's 'pipe stems' was found in a few heavily-infected children (0.3%). In a linear multivariable regression analysis, age of the child, anaemia, liver fibrosis, and size of the left liver lobe were associated with S. mansoni intensity of infection (adjusted R² = 0.11; p < 0.0005). Our results demonstrate that S. mansoni-related morbidity does develop in children less than six years of age, and that older children (37⁻60 months) are at higher risk (regression coefficient 0.33; p <0.0005) compared to younger ones (12⁻36 months). We recommend that preschool-aged children be included in the target population for schistosomiasis mass treatment so as to prevent the childhood chronic form of schistosomiasis.

Osteopontin Is Upregulated in Human and Murine Acute Schistosomiasis Mansoni

BACKGROUND

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

METHODOLOGY/PRINCIPAL FINDINGS

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

CONCLUSIONS/SIGNIFICANCE

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

Low transformation growth factor-β1 production and collagen synthesis correlate with the lack of hepatic periportal fibrosis development in undernourished mice infected with Schistosoma mansoni

Undernourished mice infected (UI) submitted to low and long-lasting infections by Schistosoma mansoni are unable to develop the hepatic periportal fibrosis that is equivalent to Symmers’ fibrosis in humans. In this report, the effects of the host’s nutritional status on parasite (worm load, egg viability and maturation) and host (growth curves, biology, collagen synthesis and characteristics of the immunological response) were studied and these are considered as interdependent factors influencing the amount and distribution of fibrous tissue in hepatic periovular granulomas and portal spaces. The nutritional status of the host influenced the low body weight and low parasite burden detected in UI mice as well as the number, viability and maturation of released eggs. The reduced oviposition and increased number of degenerated or dead eggs were associated with low protein synthesis detected in deficient hosts, which likely induced the observed decrease in transformation growth factor (TGF)-β1 and liver collagen. Despite the reduced number of mature eggs in UI mice, the activation of TGF-β1 and hepatic stellate cells occurred regardless of the unviability of most miracidia, due to stimulation by fibrogenic proteins and eggshell glycoproteins. However, changes in the repair mechanisms influenced by the nutritional status in deficient animals may account for the decreased liver collagen detected in the present study.

Cytokine profile, proliferation and phosphorylation of ERK1/2 and Akt in circulating mononuclear cells from individuals during the chronic intestinal phase of Schistosomiasis mansoni infection

Background

The immune response to Schistosoma mansoni is characterized by a granulomatous reaction around the parasite eggs that are trapped in the host liver, and this reaction modulates the immune response during the chronic phase of the disease. The typical peripheral blood mononuclear cell (PBMC) response of patients during the chronic intestinal phase of infection is characterized by a decreased response to an S. mansoni soluble egg antigen. To obtain a greater understanding of Schistosoma infections, this study investigated the effects of the soluble egg antigen (SEA) and soluble adult worm antigen (SWAP) of S. mansoni on cellular proliferation, cytokine production, and ERK1/2 and Akt phosphorylation in PBMCs from infected (XTO) and egg-negative (NI) individuals living in the same endemic area.

Methods

The activation status was evaluated by cell immunophenotypic staining (cytometry). The cell proliferation assay was by CFSE method. Cytokine detection assay (Th1 and Th2) was by Cytometric Bead and Array phosphorylation status was by ELISA.

Results

The XTO, NI and BD (blood donor) individuals from an area not endemic for schistosomiasis were compared. The CD4⁺ T lymphocyte proliferation rate was lower in the XTO group, but not the NI group, after SEA stimulation compared to the BD group. The CD8⁺ T cell proliferation rate was lower in the XTO group in the unstimulated cultures and after both SEA and SWAP stimulation compared to the BD group. Cytokine analysis after either SEA or SWAP stimulation showed a balanced cytokine pattern in the XTO and NI groups. ERK1/2 and Akt phosphorylation were only marginally detected in all groups; however, a decrease in ERK 1/2 phosphorylation was observed in the SWAP-stimulated XTO group compared to both the NI and BD groups.

Conclusions

The data indicate that SEA-stimulated CD4⁺ T cells from infected patients have a lower proliferation rate than the same cells from the NI group. Furthermore, we observed that SWAP stimulation influences ERK1/2 phosphorylation in the XTO group.

A Study of the Granulomatous Responses Induced by Different Strains of Schistosoma mansoni

The increased pathogenesis of the Schistosoma mansoni BH strain compared with the SJ strain has been attributed to the number of granulomas formed in experimental infections, which increase the mortality in definitive hosts. The aim of the present study was to investigate the development of granulomas around the eggs of the S. mansoni BH and SJ strains and to determine whether this host reaction was strain specific. Four experimental groups were analyzed. Two groups contained mice inoculated in the caudal vein with eggs from the S. mansoni BH or SJ strains and the other two contained mice that were infected with cercariae of the BH strain prior to being inoculated with eggs. The number of granulomas per tissue area in the lungs and liver, as well as the size of the granulomas, was analyzed to characterize the response to schistosome infection. The largest granulomatous responses were observed around eggs of the BH strain. Granulomas covered a larger area in the lungs of mice that were previously infected with cercariae and subsequently inoculated with eggs of the BH strain. These results indicated that specific granulomatous responses occurred following an infection with the BH and SJ strains of S. mansoni.

Schistosoma mansoni granuloma in late evolutive phase, in a case of tumoral form in man

INTRODUCTION: Authors describe human schistosomal granuloma in late chronic phase, from the morphological and evolutionary viewpoints. METHODS: The study was based on a histological analysis of two fragments obtained from a surgical biopsy of peritoneum and large intestine of a 42-year-old patient, with a pseudotumoral form mimicking a peritoneal carcinomatosis associated to the schistosomiasis hepatointestinal form. RESULTS: Two hundred and three granulomas were identified in the pseudotumor and 27 in the intestinal biopsy, with similar morphological features, most in the late chronic phase, in fibrotic healing. A new structural classification was suggested for granulomas: zone 1 (internal), 2 (intermediate) and 3 (external). CONCLUSIONS: Regarding granuloma as a whole, we may conclude that fibrosis is likely to be controlled by different and independent mechanisms in the three zones of the granuloma. Lamellar fibrosis in zone 3 seems to be controlled by matrix mesenchymal cells (fibroblasts and myoepithelial cells) and by inflammatory exudate cells (lymphocytes, plasmocytes, neutrophils, eosinophils). Annular fibrosis in zone 2, comprising a dense fibrous connective tissue, with few cells in the advanced phase, would be controlled by epithelioid cells involving zone 1 in recent granulomas. In zone 1, replacing periovular necrosis, an initialy loose and tracery connective neoformation, housing stellate cells or with fusiform nuclei, a dense paucicellular nodular connctive tissue emerges, probably induced by fibroblasts. In several granulomas, one of the zones is missing and granuloma is represented by two of them: Z3 and Z2, Z3 and Z1 or Z2 and Z1 and, ultimately, by a scar.

[Schistosoma-associated chronic septicemic salmonellosis: evolution of knowledge and immunopathogenic mechanisms]

Chronic septicemic salmonellosis is an individualized clinical entity characterized by prolonged fever with enlargement of the liver and spleen that occurs in Schistosoma-infected individuals who are coinfected with Salmonella. Several immunopathogenic mechanisms are involved, and they depend on the peculiarities of the interactions between Salmonella and various species of the genus Schistosoma. The modifications to the immune system that are caused by parasite infection are responsible for the evolution of the disease. In this review, we analyze the evolution of the knowledge on this entity and discuss the possible immuno-physiopathogenic mechanisms that contribute towards its development.

Schistosomiasis and liver fibrosis

Schistosoma mansoni infection invariably results in liver fibrosis of the host. This fibrosis may be represented by small focal areas of chronic inflammation and excess extracellular matrix deposited in periovular granulomas, distributed in variable numbers at the periphery of the portal vein system. This is the outcome of 90% of the infected population in endemic areas. Conversely, a minority of infected individuals develop extensive disease with numerous granulomas along the entire extension of the portal spaces. This latter situation is mainly dependent on special hemodynamic changes created by a heavy worm load, with the subsequent production of numerous eggs and represents a severe form of a peculiar chronic hepatopathy. Thus, host-parasite interactions in schistosomiasis help us to understand a number of important features of liver fibrosis: its initiation and regulation, the significance of accompanying vascular changes, the dynamics of fibrosis formation and regression with antiparasitic treatment; host genetic and immunological contributions, and the pathophysiology of portal hypertension.

CD4 and CD8 distribution profile in individuals infected by Schistosoma mansoni

RATIONALE

Patients with chronic Schistosoma mansoni infection show lower anti-soluble egg antigen (SEA) proliferation responses and higher responses to soluble worm antigen preparation (SWAP).

OBJECTIVE

To compare the activation status and proliferation response of peripheral blood mononuclear cells (PBMC) of infected (XTO) and egg-negative individuals (NI) living in the same endemic area.

METHODS

XTO (n = 51) and NI individuals from the same geographical area (n = 37) and healthy blood donors (n = 22) were evaluated before and after stimulation with SEA and SWAP. The expression of activation markers (CD4(+) HLADR(+), CD8(high+)HLA-DR(+) and CD8(+) CD28(+)) and proliferation assay was assessed by flow cytometry.

FINDINGS

PBMC from infected patients showed lower frequency of CD4(+) but no change in CD8(+) T cells when compared with the healthy donor group. The ratio CD4(+)/CD8(+) was 1.3, 0.6 and 0.5 in healthy donors, infected and non-infected individuals, respectively. The HLA-DR(+) expression on CD8(+) was higher in PBMC from infected and non-infected individuals than from healthy donors, but similar in both total lymphocytes and CD4(+) populations. No intergroup proliferation response differences were observed in CD4(+) and CD8(+) PBMC unstimulated and stimulated with SEA and SWAP. The SEA but not SWAP-stimulated cells showed a decrease in the expression of phosphorylated extracellular signal-regulated kinase (ERK1/2).

CONCLUSIONS

XTO and NI individuals living in the same area presented a smaller per cent of CD4(+) and a higher per cent of CD8(+) cells. The activation by either CD8(high+)HLA-DR(+) or CD8(high+)HLA-DR(+)/CD8(+) was enhanced and decreased in XTO and NI by CD8(+) CD28(+) and CD8(+) CD28(+)/CD8(+) when compared with healthy donor. ERK phosphorylation was attenuated in XTO and NI individuals when stimulated with SEA but not SWAP.

Human schistosomiasis mansoni: immune responses during acute and chronic phases of the infection

Schistosoma mansoni infection may occur either as an acute infection in individuals who have recently visited an endemic area, with no previous contact with the parasite, or as a lasting chronic disease, if not interrupted by specific chemotherapy. The acute phase is characterized by symptoms such as fever, cough, diarrhea, anorexia, and arthralgias in combination with leukocytosis and eosinophilia, and a high cellular immune response to schistosome antigens especially those from the parasite's eggs. In the chronic phase, most patients living in endemic areas are asymptomatic, and their immune responses to egg antigens are modulated. A few develop periportal fibrosis of the liver, which may result in the hepatosplenic form of the disease. The humoral response (IgG, IgM and IgE) in acute patients to egg and worm antigens does not differ from the chronic phase. However, a high level of IgG and IgM antibodies to KLH were detected in acute patients. Acute patients express a considerably higher in vitro cellular responsiveness than do chronic patients, especially to egg antigens. They present a mixed profile of Th1 and Th2 cytokines. Ultrasound examinations of endemic population reveal a high heterogeneity between the patients as regards the presence and intensity of periportal fibrosis. Most patients are asymptomatic and their immune responses to schistosoma egg antigens (SEA) are modulated. In contrast, a high percentage of patients with incipient fibrosis (early stage of hepatosplenic) responded strongly to SEA. Patients with advanced hepatosplenic disease were likely to be non-responders to SEA. Most of the chronic patients presented a Th2 profile with low production of interferon-gamma (IFN-gamma). The intensity of infection favors the production of interleukin (IL)-10. After adjusting for age, sex, and intensity of infection, a strong correlation was observed between the production of IL-13 and the degree of fibrosis. Chronic asymptomatic patients and those with incipient fibrosis expressed very high levels of heterogeneity of their antibody responses. IgG response to soluble worm antigen preparation (SWAP) was distinct and significantly higher in hepatosplenic patients than in those asymptomatic or with incipient fibrosis. Levels of IgG4 to SEA were significantly higher in sera from patients with incipient fibrosis as compared to uninfected and hepatosplenic groups. Polyclonal idiotypic antibodies and their fragments F(ab')2, directly stimulate in culture T cells of schistosomiasis patients in presence of IL-1. Polyclonal idiotypic antibodies are able to modulate in vitro granuloma formation around SEA-polyacrylamide. The importance of idiotypes for protection or pathology in schistosomiasis is still not clear.

In vitro cultured peripheral blood mononuclear cells from patients with chronic schistosomiasis mansoni show immunomodulation of cyclin D1,2,3 in the presence of soluble egg antigens

Infection with Schistosoma mansoni induces a wide range of effects on the immune responses of the host. In the present study we investigated the influence of soluble egg antigens (SEA) on the cell cycle of peripheral blood mononuclear cells (PBMC) from infected and non-infected individuals with S. mansoni resident in an endemic area and blood donors from non-endemic area. The cell cycle, the expression of activation markers and cyclin D(+)(1,2,3) CD3(+) frequency was assessed by flow cytometry. Stimulation of PBMC from infected patients with SEA resulted in a lower frequency of CD3(+) T cells in S phase when compared with the non-infected group. In addition, infected patients presented a decrease of activation marker expression (CD69(+), HLA-DR(+) and CD28(-) on CD4(+) cells and CD25(+), HLA-DR(+) on CD8(+) cells). A reduced frequency was observed of cyclin D(1,2,3) expression in SEA-stimulated T cells from infected individuals when compared with those from the non-infected group. The decreased expression of activation markers and frequency of cyclin D(1,2,3) in T cells may result in arrest of T cells in the G(0)/G(1) phase of the cell cycle, thus explaining the down-regulation observed in chronic schistosomiasis.

The schistosome in the mammalian host: understanding the mechanisms of adaptation

In this review, we envisage the host environment, not as a hostile one, since the schistosome thrives there, but as one in which the relationship between the two organisms consists of constant communication, through signalling mechanisms involving sense organs, surface glycocalyx, surface membrane and internal organs of the parasite, with host fluids and cells. The surface and secretions of the schistosome egg have very different properties from those of other parasite stages, but adapted for the dispersal of the eggs and for the preservation of host liver function. We draw from studies of mammalian cells and other organisms to indicate how further work might be carried out on the signalling function of the surface glycocalyx, the raft structure of the surface and existence of pores in the surface membrane, the repair of the surface membrane, the role of the membrane structure in ion channel function (including recent work on the actin cytoskeleton and calcium channels) and the possible role of P-glycoproteins in the adaptation of the parasite to its environment. We are speculative in some areas, such as the suggestions that variability in surface properties of schistosomes may relate to the existence of membrane rafts and that parasite communities may exhibit quorum sensing. This speculative approach is adopted with the hope that future work on the whole organisms and their interactions will be encouraged.

Hepatic changes in congenital Schistosoma japonicum infections in pigs

The inflammatory response in liver tissue from piglets congenitally infected with Schistosoma japonicum was examined at two different timepoints after infection. The piglets, which were the offspring of three sows infected with 9000 S. japonicum cercariae in the 10th week of gestation, were allocated into two groups (n=9 and 17) killed 5 or 11 weeks after birth, respectively. All piglets developed a low level infection,with no significant difference between the groups. Inflammatory lesions in the liver consisted mainly of granulomas in portal areas, often obliterating the portal veins, and frequently with central eggs or egg remnants. The granulomatous reaction consisted of epithelioid cells and occasional giant cells surrounded by layers of lymphocytes, eosinophils, plasma cells, and various amounts of collagen and fibroblasts. Mild to moderate infiltration of portal and septal connective tissue with eosinophils and lymphocytes was common, but the connective tissue was generally not increased. At the two timepoints, slight differences were observed in the numbers of eosinophils and lymphocytes in the granulomas and in the size of the granulomatous reaction. The same pattern of immunohistochemical labelling was seen in both groups. CD79alpha(+) B cells were scarce except in granuloma-associated lymphoid follicles;the majority of lymphocytes in granulomas and at other sites were CD3epsilon(+) T cells. The granulomatous reaction in the livers of piglets to schistosoma eggs from prenatal S. japonicum infection was similar to that seen in postnatal infection. Signs of immunomodulation of granulomas between the two timepoints of infection were not demonstrable.

Histopathological study of Schistosoma mansoni infection in the murine model using the PC (Pará) and LILA (Maranhão) strains

Experimental models of Schistosoma mansoni infections in mammals have contributed greatly in understanding the pathology and pathogenesis of human infection. The absence of earlier reviews regarding specific strains of the Amazon region prompted research, which the main objective was to describe histopathological lesions in different phases of schistosomiasis in a murine model using PC (Pará) and LILA (Maranhão) S. mansoni strains. One hundred and eighty young female albino swiss mice (Mus musculus) were used and were randomly divided into five groups (PC-01, PC-02, LILA-01, LILA-02, and controls), according to the number of cercariae injected and the strain adopted. Animals were sacrificed in predetermined periods (35, 56, 112, 156, and 180 days) in an attempt to follow the evolution of the disease in the histological sections of their tissues at different phases of infection. Our findings were compatible with the data already described by others authors using different strains of S. mansoni, making it possible to identify some peculiarities, which are discussed in this work. In conclusion, the strains of parasite used did not modify the histopathological findings in the tissues of infected mice in any significant way when compared with the results of other studies using different strains.

Regulatory T Cell Responses Develop in Parallel to Th Responses and Control the Magnitude and Phenotype of the Th Effector Populatio

Host survival during schistosomiasis requires the development of a tightly regulated and Th2-polarized immune response against parasite egg Ags. In this system, Th1 response suppression has been thought to be enforced through the production of IL-10 by Th2 cells and natural T regulatory (Treg) cells. By comparing Th responses in schistosome egg-injected mice that lack IL-10, IL-4, and/or Treg cells, we have been able to build a detailed picture of the relative contributions of Treg cells, Th2 cells, and IL-10 to regulation of the egg-induced response. Our data indicate that eggs induce a marked Treg cell response, evident as the extensive proliferation of Foxp3(+) cells that is proportionally as great as the response occurring within the Th compartment. Furthermore, we show that Treg cells prevent Th1 response development and limit the magnitude of the Th2 response. Although Treg cells are able to produce IL-10 after egg injection, we found no evidence for a role for IL-10 in Treg-mediated suppression of Th cell responses, nor did we find evidence for an inhibitory effect of Th2 cells on Th1 response development. Thus, the magnitude and phenotype of the egg-induced effector Th response are controlled by a parallel response within the Treg population.

Malnutrition and hepatic fibrosis in murine schistosomiasis

In this paper, four different approaches attempting to reproduce the schistosomal liver fibrosis in undernourished mice are reported: shifting from a deficient to a balanced diet and vice-versa, repeated infections, influence of the genetic background, and immunological response. Infections were performed with 30 cercariae of Schistosoma mansoni and lasted at least four months. Undernourished mice were unable to reproduce the picture of "pipestem" fibrosis, except the C57 BL/10 inbred strain, four out of 21 mice developing the liver lesion. A link of this histological finding to the type of parasite strain can not be discarded at the moment. Repeated infections increased collagen deposition mainly in well nourished animals (seven out of 16 Swiss mice developed "pipestem"-like fibrosis). In undernourished infected Swiss mice the serum levels of soluble egg antigen specific antibodies IgG1, IgG2a, IgG2b, and IgG3 were two to four times lower than those detected for well nourished controls. The decreased humoral immune response coupled to the morphological, morphometric, and biochemical results reinforce the influence of the host nutritional status on the connective tissue changes of hepatic schistosomiasis.

Experimental models of Schistosoma mansoni infection

Experimental models of Schistosoma mansoni infections in mammals have contributed greatly to our understanding of the pathology and pathogenesis of infection. We consider here hepatic and extrahepatic disease in models of acute and chronic infection. Experimental schistosome infections have also contributed more broadly to our understanding of granulomatous inflammation and our understanding of Th1 versus Th2 related inflammation and particularly to Th2-mediated fibrosis of the liver.

Human immune response in schistosomiasis: the role of P24 in the modulation of cellular reactivity to Schistosoma mansoni antigens

Schistosome antigenic components are being tested as vaccine candidates with various degrees of success, but there are only few reports using multivalent antigens to stimulate an appropriate immune response that leads to resistance or granuloma modulation. We investigated the in vitro response of peripheral blood mononuclear cells (PBMC) from chronic intestinal schistosomiasis individuals to PIII, a multivalent antigen prepared from Schistosoma mansoni adult worm antigen, and response to P24, a single antigen obtained from PIII. Treatment of PBMC with either PIII or P24 caused significant decrease in cellular proliferation and granuloma formation induced by S. mansoni antigens, and a significant elevation in IL-10 and TNF-alpha but not in IFN-gamma production. Moreover, P24 promoted an elevation in TNF-alpha level on the in vitro granuloma reaction, when cocultured with polyacrylamide beads (PB) coupled to S. mansoni antigens. These findings suggest that, besides inducing protective immunity, PIII and P24 antigens seem to be important in the regulation of in vitro granuloma formation through stimulation of IL-10 and TNF-alpha production in human schistosomiasis. The more pronounced effect of P24 on reducing the in vitro granulomatous reaction could be associated with a balance between IL-10 and TNF-alpha production.

Hepatic schistosomiasis

Schistosomiasis is a major, worldwide cause of morbidity and mortality. Disease from the organism Schistosoma mansoni results from egg deposition in the liver, intestines, and other organs and is associated with an intense, granulomatous response from the human host. Clinical manifestations range from mild to severe intestinal forms, and hepatosplenic schistosomiasis, which is associated with hepatic fibrosis, portal hypertension, esophageal varices, and splenomegaly. This article presents information about the epidemiology, immunopathogenesis and clinical aspects of the disease, the relationship between hepatic schistosomiasis and viral infections, diagnosis, therapy, and control strategies for schistosomiasis.

Significance of schistosomal granuloma modulation

Hepatic Schistosoma mansoni periovular granulomas undergo changes in size, cellular composition and appearance with time. This phenomenon, known as "immunological modulation", has been thought to reflect host immunological status. However, as modulation has not been observed outside the liver, participation of local factors, hitherto little considered, seems crucial. Components of the extracellular matrix of periovular granulomas of the mouse were particularly studied in three different organs (liver, lung and intestine) and during three periods of infection time (acute, intermediate and chronic) by means of histological, biochemical and immunofluorescence techniques, while quantitative data were evaluated by computerized morphometry, in order to investigate participation of local factors in granuloma modulation. Results confirmed modulation as a exclusively hepatic phenomenon, since pulmonary and intestinal granulomas, formed around mature eggs, did not change size and appearance with time. The matricial components which were investigated (Type I, III and IV collagens, fibronectin, laminin, proteoglycans and elastin) were found in all granulomas and in all organs examined. However, their presence was much more prominent in the liver. Elastin was only found in hepatic granulomas of chronic infection. The large amount of extracellular matrix components found in hepatic granulomas was the main change responsible for the morphological aspects of modulation. Therefore, the peculiar environment of the liver ultimately determines the changes identified in schistosomal granuloma as "modulation".

Human peripheral blood mononuclear cells stimulated by Schistosoma mansoni antigens: association between protein tyrosine kinases, mitogen-activated protein kinases and cytokine production

Concerning schistosomiasis, little is known about the intracellular signaling response of human peripheral blood mononuclear cells (PBMC) to Schistosoma mansoni antigens. To understand the critical role of protein tyrosine kinases (PTKs) in PBMC activation by S. mansoni antigens, we investigated how inhibition of PTKs by genistein, a tyrosine kinase inhibitor, affects proliferation, cytokine production and activation of mitogen-activated protein kinases (MAPKs). Our studies showed that PTKs have an important role in proliferation of PBMC from chronic schistosomiasis patients as cells stimulated with S. mansoni soluble antigens in the presence of genistein had an impaired proliferation. In contrast, PTK inhibition failed to cause any effect on MAPKs activity. We also evaluated the cytokine production for interleukin (IL)-2, interferon gamma (IFN-gamma), and IL-10 in culture supernatants of PBMC treated with or without PTKs inhibitor. Our results show that PBMC from chronic patients produced a high amount of IL-10 when stimulated with soluble egg antigen preparation (SEA), however, the amount produced of IL-2 and IFN-gamma was not significant. In the presence of PTKs inhibitor only the production of IL-10 was decreased. The findings suggest that PTKs are involved on signal transduction pathway for PBMC activation, but may not be an absolute requirement for all signaling responses to S. mansoni antigens.

Induction of protective immunity against Schistosoma mansoni infection by antigens purified from PIII, a fraction of adult worm, associated to the downregulation of granuloma formation

This study was performed in order to define Schistosoma mansoni antigens able to function as modulator agents in BALB/c mice granulomatous hypersensitivity to parasite egg. The antigens P-24, P-35 and P-97 were purified by affinity chromatography from a fraction of S. mansoni adult worm antigenic preparation, denominated PIII, involved in the inhibition of granulomatous response to eggs. Immunization of mice with these antigens, in the presence of Corynebacterium parvum and Al(OH)3 as adjuvant, induced a significant protection degree against challenge infection, as observed by the decrease on worm burden recovered from portal system. In vitro blastogenesis assays revealed that purified antigens were able to induce significant proliferation of spleen cells from S. mansoni-infected mice. This protection was correlated to significant decrease in granuloma size induced by PIII. From these results, we concluded that PIII preparation contains antigens capable of mediating protective anti-parasite immunity and down-regulating granulomatous hypersensitivity to S. mansoni eggs.

Role of cytokines in the formation and downregulation of hepatic circumoval granulomas and hepatic fibrosis in Schistosoma mansoni-infected mice

Schistosoma mansoni infections are associated with a strong Th2 cytokine response. Treatment of mice with IL-12 or anti-IL-2 or anti-IL-4 before i.v. injection of eggs increased IFN-gamma production and downregulated Th2 responses and pulmonary granuloma size. Conversely, anti-IFN-gamma antibody treatment increased Th2 responses and granuloma size. Similar manipulation produced less dramatic results in infected mice. However, sensitization of mice with eggs + IL-12 before infection augmented the Th1 response and decreased Th2 cytokines, granuloma size and fibrosis. Antisera to IFN-gamma, TNF-alpha or IL-12 during IL-12-egg immunization partly restored granuloma size and fibrosis following infection. Variations in the size of granulomas in acute (8 week) infections may be influenced primarily by the number and state of activation of T cells. In chronic (12-16 week) infections immunologic downmodulation proceeded normally in mice without functional CD8+ cells and in IFN-gamma KO mice but not in B cell KO (microMT) mice or in mice deficient in FcR expression in spite of the fact that these mice downregulated their T cell and cytokine responses. It is evident that the participation of cytokines in granuloma formation and regulation is complicated and that the mechanisms controlling both these phenomena are likely to involve both T cells and antibody/FcR interactions.

Human Schistosomiasis mansoni: IL-10 modulates the in vitro granuloma formation

Granuloma formation and modulation around Schistosoma mansoni eggs that are trapped in host tissues play a pivotal role during schistosomiasis. It has been demonstrated that the granuloma reactions differ in patients with the different clinical forms of the disease. The pathology during murine schistosomiasis has been correlated with a Th2 response while resistance to infection with a Th1 type response. In humans, very little is known about the role of different cytokines on the development of the disease. Here we demonstrate that IL-10 is an important cytokine regulating the in vitro granulomatous reactivity of PBMC from intestinal (INT) patients. This was evidenced by the fact that blockage of this cytokine in the in vitro granuloma assay lead to a significant increase in granuloma size with cells from INT patients but not with individuals in the acute phase or with the hepatosplenic (HS) form of schistosomiasis. These results demonstrate for the first time that, in context with the model, a Th2 cytokine in human schistosomiasis plays an important role in controlling morbidity.

Systemic modulation of peripheral eosinophilia (air pouch model) in Schistosoma mansoni infection

Schistosoma mansoni infection induces in their hosts a marked and sustained eosinophilia, which is influenced or modulated by complex mechanisms, that vary according to the phase of infection. To address this phenomenon, we used the air pouch (AP) model in control and infected Swiss webster mice, analyzing the cellular, tissue response and local expression of adhesion molecules [CD18 (beta(2)-chain), CD44, ICAm-1 (CD54), L-selectin (CD62L), CD49d (alpha(4)-chain), LFA1 (CD11 alpha)]. Infected animals were studied at 3 (pre-oviposition phase), 7 (acute phase), and 14 (chronic phase) weeks after infection (5-6 mice/period of infection). Normal mice were age-matched. Results showed that after egg stimulation, compared with matched controls, the infected mice, at each point of infection, showed a lower eosinophil response in the acute (7 weeks) and chronic phase (14 weeks) of infection. However, when the infected mice were in pre-oviposition phase (3 weeks) their eosinophil response surpassed the control ones. In the AP wall of infected mice, a significant decrease in the expression of ICAM-1 and CD44 in fibroblastic-like cells and a reduction in the number of CD18 and CD11 alpha in migratory cells were observed. The other adhesion molecules were negative or weakly expressed. The results indicated that in the air pouch model, in S. mansoni-infected mice: (1) eosinophil response is strikingly down-regulated, during the acute ovular phase; (2) in the pre-oviposition phase, in contrast, it occurs an up-regulatory modulation of eosinophil response, in which the mechanisms are completely unknown; (3) in the chronic phase of the infection, the down modulation of eosinophil response is less pronounced; 4) Down-regulation of adhesion molecules, specially of ICAM-1 appear to be associated with the lower eosinophil response.

The immune response and immunopathology in infection with Schistosoma mansoni: a key role of major egg antigen Sm-p40

The immune response and related granulomatous inflammation in infection with Schistosoma mansoni are ultimately dependent on SEA-sensitized CD4+ Th cells and comprise multiple pathways variously involving the activation and recruitment of different cell populations and the production of different inflammatory cytokines, all under the influence of regulatory genetic factors. The spontaneous downregulation of granuloma formation (immunomodulation), in turn, is a well-known phenomenon, but the full extent of its precipitating factors is still uncertain. This review describes a pathway leading to immunomodulation that features at its centre the down-regulatory cytokine IL-10. This mechanism is attractive because it offers a cogent correlation between findings in the laboratory and those displayed by patients affected with the disease. The Sm-p40 antigen, a major component of schistosome eggs, elicits a strong CD4+ Th cell response in H-2k mice that correlates with intense granuloma formation; in contrast, its immunogenicity is relatively minor during infection of other mouse strains that develop smaller granulomas. Of great interest is that the Sm-p40 antigen only elicits a Th-1 type cytokine response, a phenotype that remains constant even as the overall response to SEA shifts to a Th-2 type. The Sm-p40 molecule has a dominant epitope that is the target of CD4+ Th cells from infected H-2k mice; indeed, a minimal peptide that bears the epitope binds to I-Ak. The importance of pursuing a systematic elucidation of the major egg antigens, resides in the exciting possibility of specifically desensitizing the CD4+ Th cells that mediate granuloma formation, which may achieve meaningful prevention or amelioration of clinical disease.

IL-10 Regulates Liver Pathology in Acute Murine Schistosomiasis mansoni But Is Not Required for Immune Down-Modulation of Chronic Disease

We have used IL-10 gene knockout mice (IL-10T) to examine the role of endogenous IL-10 in the down-modulation of hepatic granuloma formation and lymphocyte responses that occurs in chronic infection with the helminth parasite Schistosoma mansoni. Although IL-10-deficient animals showed 20 to 30% mortality between 8 and 14 wk postinfection, they displayed no alterations in their susceptibility to infection and produced similar numbers of eggs as their wild-type littermates. The IL-10T mice displayed a significant increase in hepatic granuloma size at the acute stage of infection, which was associated with increased IFN-γ, IL-2, IL-1β, and TNF-α mRNA expression in liver and elevated Th1-type cytokine production by lymphoid cells. Despite developing an enhanced Th1-type cytokine response, the IL-10T mice showed no consistent decrease in their Th2-type cytokine profile. Surprisingly, although granulomatous inflammation was enhanced at the acute stage of infection, the livers of IL-10T mice displayed no significant increase in fibrosis and underwent normal immune down-modulation at the chronic stage of infection. Moreover, the down-modulated state could be induced in IL-10T mice by sensitizing the animals to schistosome eggs before infection, further demonstrating that the major down-regulatory mechanism is not dependent upon IL-10. We conclude that while IL-10 plays an important role in controlling acute granulomatous inflammation, it plays no essential role in the process of immune down-modulation in chronic schistosome infection.

Cytokines as determinants of resistance and pathology in human Schistosoma mansoni infection

The role of different cytokines in the peripheral blood mononuclear cell (PBMC) proliferative response and in in vitro granuloma formation was evaluated in a cross-sectional study with patients with the different clinical forms and phases of Schistosoma mansoni infection, as well as a group of individuals "naturally" resistant to infection named normal endemic (NE). The blockage of IL-4 and IL-5 using anti-IL-4 and anti-IL-5 antibodies significantly reduced the PBMC proliferative response to soluble egg (SEA) and adult worm (SWAP) antigens in acute (ACT), chronic intestinal (INT) and hepatosplenic (HS) patients. Similar results were obtained in the in vitro granuloma formation. Blockage of IL-10 had no significant effect on either assay using PBMC from ACT or HS. In contrast, the addition of anti-IL-10 antibodies to PBMC cultures from INT patients significantly increased the proliferative response to SEA and SWAP as well as the in vitro granuloma formation. Interestingly, association of anti-IL-4 and anti-IL-10 antibodies did not increase the PBMC proliferative response of these patients, suggesting that IL-10 may act by modulating IL-4 and IL-5 secretion. Addition of recombinant IL-10 decreased the proliferative response to undetectable levels when PBMC from patients with the different clinical forms were used. Analysis of IFN-gamma in the supernatants showed that PBMC from INT patients secreted low levels of IFN-gamma upon antigenic stimulation. In contrast, PBMC from NE secreted high levels of IFN-gamma. These data suggest that IL-10 is an important cytokine in regulating the immune response and possibly controlling morbidity in human schistosomiasis mansoni, and that the production of IFN-gamma may be associated with resistance to infection.

Induction of hepatic egg granuloma hyporesponsiveness in murine schistosomiasis mansoni by intravenous injection of small doses of soluble egg antigen

This work was designed to test whether hyporesponsiveness to schistosomal egg antigen (SEA) was associated with reduction in size of hepatic granulomas. Multiple small doses of SEA (10 micrograms x 4) were injected intravenously (i.v.) into C57B1/6 mice either at 7 or 30 days prior to cercarial exposure. Eight weeks postinfection, hepatic histopathology and granuloma diameter were studied. SEA-induced lympho-proliferative response, splenic cytokines (IL-2, IL-4 and IL-5) and serum antischistosomal IgG were assessed. Worm burden and tissue egg load were counted. Compared to infected controls, the SEA-treated groups showed decrease in granuloma diameter, remarkable increase in the percentage of degenerated ova within hepatic granulomas and amelioration of histopathological changes. SEA lymphoproliferative response, and levels of Il-2 and IL-4, were lower in SEA-treated groups than infected controls. The levels of IL-5 and antishistosomal IgG were comparable to the infected controls. The intensity of infection was not influenced by i.v. injection of SEA. The present data show that i.v. administration of multiple small doses of SEA induced granulomatous hyporesponsiveness with amelioration of hepatic pathology and acceleration of egg destruction.

The role of protein kinases in antigen-activation of peripheral blood mononuclear cells of Schistosoma mansoni infected individuals

T cell recognition of antigens displayed on the surface of antigen presenting cell results in rapid activation of protein tyrosine kinases and kinase C. This process leads to second messengers, such as inositol phosphates and diacylgycerol, and phosphorylation of multiple proteins. The role of different protein kinases in the activation of peripheral blood mononuclear cells (PBMC) from Schistosoma mansoni infected individuals was evaluated using genistein and H-7, specific inhibitors of protein tyrosine kinase and kinase C, respectively. Our results showed that proliferation in response to soluble egg antigen or adult worm antigen preparation of S. mansoni was reduced when PBMC were cultured in presence of protein kinase inhibitors. Using these inhibitors on in vitro granuloma reaction, we also observed a marked reduction of granuloma index. Taken together, our results suggest that S. mansoni antigen activation of PBMC involves protein kinases activity.

Expression of class II, but not class I, major histocompatibility complex molecules is required for granuloma formation in infection with Schistosoma mansoni

Previous studies have suggested that granulomatous inflammation in schistosomiasis is mediated by CD4+ T helper lymphocytes sensitized to parasite egg antigens. However, CD8+ T cells have also frequently been associated with the immune response to schistosome eggs. To examine more precisely the role of CD4+ and CD8+ T cells in the pathology of the schistosomal infection, we used mice with targeted mutations in major histocompatibility complex (MHC) class II or class I molecules. These mutations lead, respectively, to the virtual absence of CD4+ and CD8+ T cells. The results clearly show that schistosome-infected MHC class II mutant mice failed to form granulomas around parasite eggs. In contrast, infected MHC class I mutant mice displayed characteristic granulomatous lesions that were comparable to those in wild-type control mice. Moreover, lymphoid cells from MHC class II mutant mice were unable to react to egg antigens with either proliferative or cytokine [interferon-gamma, interleukin (IL)-4, IL-10] responses; nor were they able to present egg antigens to specifically sensitized CD4+ T helper cells from infected syngeneic control mice. By comparison, cells from MHC class I mutant mice exercised all these functions in a manner comparable with those from wild-type controls. These observations clearly demonstrate that schistosomal egg granulomas are mediated by MHC class II-restricted CD4+ T helper cells. They also suggest that CD8+ T cells do not become sensitized to egg antigens and play little role, if any, in the pathogenesis of schistosomiasis.

Experimental murine schistosomiasis: reduced hepatic morbidity after pre- and/or post-infection treatment with ibuprofen or diclofenac sodium

Arachidonic-acid metabolites appear to participate in skin penetration by and transformation of schistosome cercariae and in the pathogenesis of schistosomiasis. With this in mind, mice were treated with one of two cyclooxygenase inhibitors before and/or after infection with Schistosoma mansoni. The effects of the treatment on liver morbidity and the parasitic infection were then evaluated, using infected, untreated and uninfected, treated mice as controls. Treatment with ibuprofen (20 mg/kg.day) or diclofenac sodium (2.5 mg/kg.day) for 7 days before infection led to significantly lower liver weights, worm loads and hepatic hydroxyproline contents than in the untreated mice. If treatment with either drug was continued after infection, for 28 days, there was an additional significant decrease in hepatic gamma-glutamyl transpeptidase activity. All these parameters except liver weight were similarly affected when treatment with either drug was begun on the day of infection and continued for 28 days. There was no significant change in liver weight or worm load when treatment was delayed until day 28 post-infection but faecal egg counts were reduced in the treated groups. In additional experiments, using a smaller dose of diclofenac sodium (1.25 mg/kg.day), all the measured parameters of infection were significantly decreased when the treatment was initiated 7 days before infection and continued until day 28 post-infection. The results indicate that the treatment of S. mansoni-infected mice with ibuprofen or diclofenac sodium was effective in reducing the severity of infection and in attenuating hepatic fibrosis, particularly when the treatment was started early in relation to the time of infection.

Accessory cell signals regulate Th-cell responses: from basic immunology to a model of helminthic disease

Schistosome helminths inflict serious tissue damage by eliciting T helper (Th)-cell-mediated granulomatous inflammation around parasite eggs. The egg granulomas are large in acute disease and smaller in chronic disease. To explain this downregulation in chronic disease, Miguel Stadecker and Pedro Flores Villanueva describe a mechanism whereby CD4+ Th1-type lymphocytes, which are associated with the initial vigorous granuloma formation, are rendered anergic to subsequent antigenic stimulation. This results in the reduction of granuloma size and in the dominance of Th2-type lymphocyte responses.

Aspects of the granulomatous reaction in the liver of mice infected and reinfected with two different geographical strains of Schistosoma mansoni

In this study, which was undertaken in relation to the histopathologic behavior of two different strains (LE-Belo Horizonte, MG and SJ-São José dos Campos, SP) in infections and reinfections (homologous or heterologous) with Schistosoma mansoni, the authors confirmed a more accentuated pathogenicity of the SJ strain. All the reinfections showed the presence of typical granulomas of the acute phase, when performed either with the same strain (homologous) or with a different strain (heterologous) of the parasite of the primo infection. The possible mechanisms responsible for reactivation of the immunopathologic response in reinfections are discussed.

The effect of chronic ingestion of ethanol on modulation of granulomatous inflammation in experimental schistosomiasis in mice

We studied the role of ethanol on the modulation of liver granulomata around Schistosoma mansoni eggs in mice. Albino mice, receiving 7% ethanol as the sole drinking liquid, at 60 and 90 days post-infection, presented smaller granulomata than controls did, when sacrificed at 120 days post-infection. No differences in diameters could be observed, when ethanol was given 4 months before up to 120 days after infection. The results suggested that modulation of schistosome granulomata by ethanol ingestion varies with time and duration of drug consumption.

Experimental pulmonary schistosomiasis: lack of morphological evidence of modulation in schistosomal pulmonary granulomas

Numerous pulmonary schistosome egg granulomas were present in mice submitted to partial portal vein ligation (Warren's model). The granulomas were characterized by cellular aggregations formed within alveolar tissue. Main cellular types were macrophages (epithelioid cells), eosinophils, plasma cells and lymphocytes. These cells were supported by scanty fibrous stroma and exhibited close membrane contact points amongst themselves, but without forming specialized adhesion apparatus. When granulomas involved arterial structures, proliferation of endothelial and smooth muscle cells occurred and fibrosis associated with angiogenesis became more evident. Granulomas formed around mature eggs in the pulmonary alveolar tissue presented approximately the same size and morphology regardless of the time of infection, the latter being 10, 18 and 25 weeks after cercarial exposure. This persistence of morphological appearance suggests that pulmonary granulomas do not undergo immunological modulation, as is the case with the granulomas in the liver and, to a lesser extent, in the intestines. Probably, besides general immunological factors, local (stromal) factors play an important role in schistosomal granuloma modulation.

Specific treatment of hepatosplenic schistosomiasis can increase T-lymphocyte reactivity

It has been recognized that Schistosoma mansoni infection causes depression of T-cell responsiveness. In this study we have evaluated whether immunodepression associated to schistosomiasis could be reverted by specific treatment. T-cell immune response was assessed by means of intradermal tests using recall antigens in a group of 22 patients with hepatosplenic schistosomiasis, one year after treatment with oxamniquine and compared with a group of untreated hepatosplenic patients. Only 27% of treated patients presented complete anergy to all tested antigens, in marked contrast to 80% unresponsiveness showed by hepatosplenic patients without treatment. Although most of the treated individuals showed some response to the tested antigens, in some individuals this unresponsiveness still persisted after treatment. Anergy was not found in any normal individual of the control group. It was concluded that Schistosoma mansoni infected patients may recover their normal immune responsiveness after the elimination of the worm by treatment.

Dissociation of antibody responses during human schistosomiasis and evidence for enhancement of granuloma size by anti-carbohydrate IgM

Immunoglobulin (Ig) G and IgM antibody levels to soluble egg antigens (SEA), adult worm glycoproteins (AWGP), carbohydrate antigens (CHO) and cationic exchange fraction 6 (CEF6) were measured in serum specimens taken from Brazilian patients with acute, intestinal, hepato-intestinal and hepatosplenic schistosomiasis mansoni. The antibody levels varied among the groups, with the highest anti-egg antigen responses in the acute patients and the highest anti-adult worm responses in patients with chronic disease. The responses to the component parts of the egg antigens were dissociated, with anti-carbohydrate IgG and IgM responses being highest in the acute infection group and anti-CEF6 IgG responses being uniform among the clinical groups. The possibility of a direct role for anti-CHO antibody responses in egg-induced pathology was investigated using the mouse lung model. The anti-carbohydrate monoclonal antibody NIMP/M45 significantly enhanced granuloma formation. Mice given NIMP/M45 produced granulomas larger than those of naive mice or mice given an unrelated monoclonal antibody, and as large as those produced by mice which had been presensitized to egg antigens. The independent regulation of responses to egg antigens may indicate that such responses are minimized to reduce the pathological consequences of infection whilst allowing the development of protective anti-worm responses.

T cell-dependent immunodepression in vivo in Schistosoma mansoni infected patients

T-cell function was evaluated in 29 patients with either hepatointestinal or hepatosplenic schistosomiasis by intradermal tests to recall antigens. Immunodepression was detected in 26% of the subjects with hepatointestinal schistosomiasis and in 50% of those with the hepatosplenic form. Cellular immunodepression was related to worm load and spleen size. This non specific T-cell immunodepression may represent a serious constraint to the elimination of intracellular pathogens both in hepatosplenic or hepatointestinal schistosomiasis.

Immunopathology of Schistosoma mansoni infection

Schistosomiasis mansoni is a chronic helminthic disease that affects about 100 million people in the tropics. The worms have a life span of 5 to 10 years, and they live in the mesenteric veins of the host. Lightly infected individuals are asymptomatic or manifest mild intestinal symptoms. Heavily infected individuals often develop severe morbidity with hepatosplenomegaly, sometimes with a fatal outcome. Morbidity is attributed to the strong humoral and T-cell-mediated host immune responses developed to a variety of parasite antigens and expressed as tissue inflammations. The immunopathology includes dermatitis, immune complex-mediated kidney disease, and, chiefly, T-cell-mediated granuloma formation and fibrosis around disseminated parasite eggs. This review describes the mechanisms of induction and expression of immunopathology in infected persons and experimental animals. Immunoregulatory mechanisms that modulate the enhanced immune responses and may ameliorate excessive morbidity are discussed.

[Cerebral schistosomiasis mansoni]

This paper reports a case of cerebral schistosomiasis in pseudotumoral form, located in the cortex of the left parietal lobe, causing right hemiparesy and intracranial hypertension syndrome, diagnosed by surgical biopsy. Vascular and immunological factors are considered in regard to the physiopathogeny of neuroschistosomiasis. Emphasis is placed on the necessity of more detailed studies, on more accurate diagnosis, and on the publication of the various forms of cerebral involvement in schistosomiasis mansoni. This involvement appears to be more frequent than what presently believed. Since clinical symptoms in cerebral involvement during disease is rare, descriptions of pseudotumoral form appear infrequently in medical literature.

Dynamics of hepatic connective tissue matrix constituents during murine Schistosoma mansoni infection

Hepatic fibrosis is the major clinical sequela of infection with the helminth Schistosoma mansoni. However, little is known regarding its dynamics and regulation in schistosomiasis. The present study presents the dynamics of deposition and resorption of two major extracellular matrix components of fibrosis, glycosaminoglycans and collagens, during the course of experimental S. mansoni infection. Early in infection (6 weeks), glycosaminoglycan biosynthesis was markedly elevated, as was collagen biosynthesis. This led to significant accumulations of these two molecules at a glycosaminoglycan/collagen ratio similar to that observed in livers of uninfected mice (uronic acid/hydroxyproline ratio of 1.10 at 6 weeks compared to normal value of 1.25). During maximal hepatic fibrosis (12 to 18 weeks), both collagen and glycosaminoglycan biosynthesis continued to increase but the extracellular matrix shifted to a lower glycosaminoglycan/collagen ratio of 0.42, suggesting enhanced glycosaminoglycan breakdown. In addition, during this acute stage of infection, Type I collagen was the predominant isotype synthesized, whereas total collagenolytic activity degrading Type I collagen was maximal. During chronic infection, a decrease in the content of both hepatic glycosaminoglycans and collagens were noted, with a glycosaminoglycan/collagen ratio of 0.63. Decreased glycosaminoglycan content paralleled diminished biosynthetic rates. On the other hand, an over 50% reduction in collagen content (from 18 to 24 weeks) appeared not to result from diminished biosynthesis but from a switch in the predominant collagen isotype synthesized (from Type I to Type III), matched by an enhanced constitutive collagenolytic activity directed toward this type of collagen.(ABSTRACT TRUNCATED AT 250 WORDS)

Collagen isotypes, laminin, and fibronectin in granulomas of the liver and intestines of Schistosoma mansoni-infected mice

Patterns of fibrosis within hepatic and intestinal granulomas of Schistosoma mansoni-infected mice were analyzed by indirect immunofluorescence. Deposition of collagen isotypes, laminin, and fibronectin was evaluated semiquantitatively between 8 and 20 weeks of the infection. Liver granulomas were the largest at 8 weeks and contained low amounts of type I and higher amounts of type III collagen and fibronectin. Collagen deposition became pronounced as infection progressed. The relative amounts of type I collagen deposits rose and equalled that of type III. In the smaller immunomodulated granulomas at 20 weeks both types I and III were high, and type IV collagen deposition was observed. Fibronectin and laminin deposits were also detected. The small ileal granulomas did not change their size during the course of the infection. At 8 weeks, connective tissue matrix deposition was barely detectable within these lesions. Gradually, small deposits of types I and III appeared in equal amounts and attained highest levels by 20 weeks of the infection. Fibronectin deposits at that time were very prominent but laminin and type IV collagen were absent. Colon granulomas at 8 weeks of the infection were only somewhat smaller than those of the liver, yet contained very sparse deposits of types I and III collagen. During the ensuing weeks collagen deposits rose only slightly. By 20 weeks the granulomas diminished in size and within those lesions type III collagen was predominant. Whereas the presence of fibronectin was pronounced, type IV collagen and laminin were detectable only in trace amounts. These observations indicate the existence of important organ-related differences in the intragranulomatous deposition of connective tissue matrix.