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

Expression of SmATPDases 1 and 2 in Schistosoma mansoni eggs favours IL-10 production in infected individuals

A role of IL-10 is down-regulating T-cell responses to schistosome antigens. Since SmATPDases can be correlated to modulation of the immune response, we evaluated the expression of enzymes in S. mansoni eggs. Faecal samples were collected from 40 infected individuals to detect coding regions of the SmATPDases. The cytokines were measured in supernatants of PBMC. The analysis was performed by the global median determination and set up high producers (HP) of cytokines. Six individuals expressed SmATPDase1, six expressed SmATPDase2 and six expressed both enzymes. The group who expressed only SmATPDase1 showed a high frequency of IFN-γ, TNF IL-4 HP; individuals who expressed only SmATPDase2 showed a high frequency of IFN-γ, IL-6 and IL-4 HP; and individuals who expressed both enzymes showed a high frequency of IL-10 HP. The comparison of the IFN-γ/IL-10 ratio presented higher indices in the group who had SmATPDase 2 expression than those who had the expression of both enzymes. The positive correlation between infection intensity and IL-10 levels remained only in the positive SmATPDase group. The IL-10 is the only cytokine induced by the expression of both enzymes. Our data suggest that the expression of both enzymes seems to be a factor that modulates the host immune response by inducing high IL-10 production.

Helminth species-specific effects on IFN-γ producing T cells during active and latent tuberculosis

BACKGROUND

Interferon-γ (IFN-γ) is a key cytokine inducing protective immune responses during tuberculosis (TB) infection. Helminth-induced immune responses may affect IFN-γ production by T cells, although its connection with disease severity and immune recovery during treatment is unexplored. We investigated the species-specific effect of helminths on the IFN-γ production by T cells in relation to disease severity during active and latent TB infection (LTBI).

METHODS

In this study, 69 active pulmonary TB patients (PTB), 28 with LTBI and 66 healthy controls were included. Active TB was diagnosed using GenXpert MTB/RIF while QuantiFERON test (QFT) was used for the screening of healthy community controls (CCs) and for the diagnosis of LTBI. Helminth infection was identified by routine diagnosis whereas clinical disease severity was evaluated by the TB score. Intracellular IFN-γ production of T cells in stimulated peripheral blood mononuclear cells (PBMCs) was analyzed by flow cytometry using TB antigens (PPD), the polyclonal T cell activator staphylococcal enterotoxin B (SEB), or medium as unstimulated control.

RESULTS

Helminth infected CCs and LTBI subjects showed a significant reduction of IFN-γ+ CD4+ T cells by PPD-stimulation compared to non-helminth infected control groups. The significant reduction in the frequency of IFN-γ+ T cells in both latent and active PTB patients following SEB stimulation was mostly attributed to Schistosoma mansoni infection, whereas Ascaris lumbricoides, Schistosoma mansoni, and hookworm infection contributed equally in CCs. Following anti-helminthic and anti-TB treatment for 2 months, the frequency of IFN-γ+ CD4 T cells in helminth coinfected PTB was restored to levels of helminth negative PTB before treatment. Helminth coinfected PTB patients with an intermediate and severe clinical course had reduced capacity for production of IFN-γ+ T cells compared to the corresponding non-helminth infected PTB.

CONCLUSION

We found a reduction in IFN-γ producing T cells by helminth coinfection which was restored following anti-helminthic treatment. This reduction was helminth species-dependent in an exploratory sub-analysis and correlated to increased disease severity.

Profile of T and B lymphocytes in individuals resistant to Schistosoma mansoni infection

The mechanisms involved in the development of resistance to infection/reinfection by Schistosoma mansoni still arouse great interest and controversy. Some authors demonstrate that resistance to infection is attributed to a mixed Th1 and Th2 response and resistance to reinfection after repeated treatments through mechanisms associated with the Th2 response. Through flow cytometry, the phenotypic characterization of B and T lymphocytes in individuals residing in endemic areas with low parasite loads over 10 years was evaluated for the first time in humans. In this study, individuals with low parasite loads for Schistosoma mansoni had a higher proportion of Th1 and Th2 cells. In addition, lymphocytes from these individuals showed a higher degree of expression of costimulatory molecules CD28 and CTLA-4 and regulatory molecules FoxP3 and IL-10, when compared to individuals with high parasite loads. Our data indicate that the control of the parasite load of S. mansoni must be associated with a Th1, Th2, and regulatory response, and that further studies are needed to elucidate the possibility of mechanisms associated with the hyporesponsiveness of lymphocytes from individuals with high parasite loads.

Cytokine Response Profiles of School-Aged Children Infected with Schistosomiasis before and after Praziquantel Treatment

Schistosomiasis is a parasitic disease that affects millions of people in 78 countries globally. Children under the age of 14, who have the chronic disease may suffer from anemia and malnutrition that contribute to lost days at school and pervasive learning disabilities. The infection is prevalent in Kenya, especially in endemic areas, contributing to significant morbidity. The cellular response pattern is associated with both the acute and chronic phases of the disease, in which cytokines play a critical role. The objective of this study was to evaluate the cytokine profiles of IL-4, IL-2, IL-10, IL-5, IFN-γ, and TNF in serum samples of infected school-aged children by using flow cytometry before and after treatment. The analysis indicated a shift in the expression of the cytokines after treatment with all the cytokines being downregulated, except TNF. There was a general trend of decrease in the expression of the cytokines at six and twelve weeks after treatment as compared to the pretreatment levels. There were statistically significant differences in the expression in IL-2 (P=0.001^∗∗), IL-4 (P=0.033^∗), IL-10 (P=0.001^∗∗∗), IFN-γ (P=0.023^∗), and IL-5 (P=0.0001^∗∗∗), except in TNF (P=0.095). The reduction in the cytokine levels can be directly related to the influence of the drug praziquantel, modulating the cytokine response by elimination of adult worms, decline in parasitic load, and reduction of morbidity. Therefore, cytokine response is directly related with the influence of treatment in the variation of the immune response.

Functional Studies of T Regulatory Lymphocytes in Human Schistosomiasis in Western Kenya

Immunoregulation is considered a common feature of Schistosoma mansoni infections, and elevated levels of T regulatory (Treg) lymphocytes have been reported during chronic human schistosomiasis. We now report that the removal of Treg (CD4+/CD25^hi/CD127^low lymphocytes) from peripheral blood mononuclear cells (PBMCs) of S. mansoni–infected individuals leads to increased levels of phytohemagglutinin (PHA)-stimulated interferon gamma (IFNγ) production and decreased interleukin-10 (IL-10) responses. Exposure to schistosome antigens did not result in measurable IFNγ by either PBMC or Treg-depleted populations. Interleukin-10 responses to soluble egg antigens (SEA) by PBMC were unchanged by Treg depletion, but the depletion of Treg greatly decreased IL-10 production to soluble worm antigenic preparation (SWAP). Proliferative responses to PHA increased upon Treg removal, but responses to SEA or SWAP did not, unless only initially low responders were evaluated. Addition of anti-IL-10 increased PBMC proliferative responses to either SEA or SWAP, but did not alter responses by Treg-depleted cells. Blockade by anti-transforming growth factor-beta (TGF-β) increased SEA but not SWAP proliferative responses by PBMC, whereas anti-TGF-β increased both SEA- and SWAP-stimulated responses by Treg-depleted cultures. Addition of both anti-IL-10 and anti-TGF-β to PBMC or Treg-depleted populations increased proliferation of both populations to either SEA or SWAP. These studies demonstrate that Treg appear to produce much of the antigen-stimulated IL-10, but other cell types or subsets of Treg may produce much of the TGF-β. The elevated levels of Treg seen in chronic schistosomiasis appear functional and involve IL-10 and TGF-β in antigen-specific immunoregulation perhaps leading to regulation of immunopathology and/or possibly decreased immunoprotective responses.

Plasma levels of innate immune mediators are associated with liver fibrosis in low parasite burden Schistosoma mansoni-infected individuals

In the murine model, it was demonstrated that pro-inflammatory cytokines and chemokines are essential to the formation and modulation of Schistosoma-induced granulomatous inflammation. However, the relationship of these immune mediators and disease severity is hard to be established in naturally infected individuals. The current study evaluates the association between plasma concentrations of MIF, sTNF-R1, CCL3, CCL7 and CCL24 and schistosomiasis morbidity in Schistosoma mansoni-infected patients with a low parasite burden. For this propose, 97 S. mansoni-infected individuals were subjected to abdominal ultrasound analysis and clinical examination. Among them, 88 had plasma concentration of immune mediators estimated by ELISA assay. Multivariate linear regression models were used to evaluate the relationship between the plasma concentration of immune mediators and the variables investigated. Although most individuals presented low parasite burden, over 30% of them showed signs of fibrosis defined by ultrasound measurements and 2 patients had a severe form of schistosomiasis. No association between parasite burden and the plasma levels of chemokine/cytokines or disease severity was observed. There was a positive association between plasma concentration of CCL4, sTNF-R1, CCL3 and MIF with gall bladder thickness and/or with portal vein thickness that are liver fibrosis markers. In contrast, no association was found between CCL7 plasma concentrations with any of the schistosomiasis morbidity parameters evaluated. The data showed that CCL24, sTNFR1, MIF and CCL3 can be detected in plasma of S. mansoni-infected individuals and their concentration would be used as prognostic makers of Schistosoma-induced liver fibrosis, even in individuals with low parasite burden.

Schistosoma mansoni Tegument (Smteg) Induces IL-10 and Modulates Experimental Airway Inflammation

BACKGROUND

Previous studies have demonstrated that S. mansoni infection and inoculation of the parasite eggs and antigens are able to modulate airways inflammation induced by OVA in mice. This modulation was associated to an enhanced production of interleukin-10 and to an increased number of regulatory T cells. The S. mansoni schistosomulum is the first stage to come into contact with the host immune system and its tegument represents the host-parasite interface. The schistosomula tegument (Smteg) has never been studied in the context of modulation of inflammatory disorders, although immune evasion mechanisms take place in this phase of infection to guarantee the persistence of the parasite in the host.

METHODOLOGY AND PRINCIPAL FINDINGS

The aim of this study was to evaluate the Smteg ability to modulate inflammation in an experimental airway inflammation model induced by OVA and to characterize the immune factors involved in this modulation. To achieve the objective, BALB/c mice were sensitized with ovalbumin (OVA) and then challenged with OVA aerosol after Smteg intraperitoneal inoculation. Protein extravasation and inflammatory cells were assessed in bronchoalveolar lavage and IgE levels were measured in serum. Additionally, lungs were excised for histopathological analyses, cytokine measurement and characterization of the cell populations. Inoculation with Smteg led to a reduction in the protein levels in bronchoalveolar lavage (BAL) and eosinophils in both BAL and lung tissue. In the lung tissue there was a reduction in inflammatory cells and collagen deposition as well as in IL-5, IL-13, IL-25 and CCL11 levels. Additionally, a decrease in specific anti-OVA IgE levels was observed. The reduction observed in these inflammatory parameters was associated with increased levels of IL-10 in lung tissues. Furthermore, Smteg/asthma mice showed high percentage of CD11b+F4/80+IL-10+ and CD11c+CD11b+IL-10+ cells in lungs.

CONCLUSION

Taken together, these findings demonstrate that S. mansoni schistosomula tegument can modulates experimental airway inflammation.

Multivariable Regression Analysis in Schistosoma mansoni-Infected Individuals in the Sudan Reveals Unique Immunoepidemiological Profiles in Uninfected, egg+ and Non-egg+ Infected Individuals

BACKGROUND

In the Sudan, Schistosoma mansoni infections are a major cause of morbidity in school-aged children and infection rates are associated with available clean water sources. During infection, immune responses pass through a Th1 followed by Th2 and Treg phases and patterns can relate to different stages of infection or immunity.

METHODOLOGY

This retrospective study evaluated immunoepidemiological aspects in 234 individuals (range 4-85 years old) from Kassala and Khartoum states in 2011. Systemic immune profiles (cytokines and immunoglobulins) and epidemiological parameters were surveyed in n = 110 persons presenting patent S. mansoni infections (egg+), n = 63 individuals positive for S. mansoni via PCR in sera but egg negative (SmPCR+) and n = 61 people who were infection-free (Sm uninf). Immunoepidemiological findings were further investigated using two binary multivariable regression analysis.

PRINCIPAL FINDINGS

Nearly all egg+ individuals had no access to latrines and over 90% obtained water via the canal stemming from the Atbara River. With regards to age, infection and an egg+ status was linked to young and adolescent groups. In terms of immunology, S. mansoni infection per se was strongly associated with increased SEA-specific IgG4 but not IgE levels. IL-6, IL-13 and IL-10 were significantly elevated in patently-infected individuals and positively correlated with egg load. In contrast, IL-2 and IL-1β were significantly lower in SmPCR+ individuals when compared to Sm uninf and egg+ groups which was further confirmed during multivariate regression analysis.

CONCLUSIONS/SIGNIFICANCE

Schistosomiasis remains an important public health problem in the Sudan with a high number of patent individuals. In addition, SmPCR diagnostics revealed another cohort of infected individuals with a unique immunological profile and provides an avenue for future studies on non-patent infection states. Future studies should investigate the downstream signalling pathways/mechanisms of IL-2 and IL-1β as potential diagnostic markers in order to distinguish patent from non-patent individuals.

Association between allergic responses and Schistosoma mansoni infection in residents in a low-endemic setting in Brazil

INTRODUCTION

Schistosomiasis is endemic in 76 countries and territories. Several studies have found an inverse correlation between parasitic disease and the development of allergies. The purpose of the present study was to determine whether infection with Schistosoma mansoni in subjects with a low parasite load is protective against allergy. The final sample consisted of 39 S. mansoni-positive and 52 S. mansoni-negative residents of a small community in northeastern Brazil.

METHODS

All subjects were submitted to the Kato-Katz test, anti-S. mansoni IgG measurement, the prick test for aeroallergens, eosinophil counts and serum IgE measurement.

RESULTS

Subjects who reacted to one or more antigens in the prick test were considered allergic. Only 7 S. mansoni-positive subjects (17.9%) reacted to one or more antigens, whereas 20 S. mansoni-negative subjects (38.5%) tested positive for allergy.

CONCLUSIONS

Our findings suggest that, in areas of low endemicity, infection with S. mansoni significantly reduces the risk of the development of allergy in subjects with a low parasite load.

Altered levels of circulating miRNAs are associated Schistosoma japonicum infection in mice

Background

Dioecious flatworms of the genus Schistosoma causes schistosomiasis, which is a major public health problem in developing countries. Acquiring detailed knowledge of schistosome-host interactions may aid in the development of novel strategies for schistosomiasis control. MicroRNAs (miRNAs) are involved in processes such as development, cell proliferation, metabolism, and signal transduction. Circulating miRNAs not only serve as a novel class of biomarkers of many diseases but also regulate target gene expression in recipient cells, which are similar to hormones.

Methods

In the present study, we used miRNA microarrays to determine the profile of circulating miRNAs associated with S. japonicum infection of mice. The biological functions of the altered levels of miRNAs and their target genes were predicted using bioinformatics. Expression levels of selected miRNAs and their target genes were further analyzed by quantitative RT-PCR.

Results

Our study identified 294 and 189 miRNAs in infected mice that were expressed in two independent experiments at levels ≥ 2-fold higher or ≤ 0.5-fold lower, respectively, compared with uninfected mice. Thirty-six of the same miRNAs were detected in these analyses. Moreover, pathway analyses indicated that most of these miRNAs are putatively involved in signaling pathways associated with pathogenesis, such as Wnt and MAPK signaling. Further, we show an inverse correlation between the circulating levels of these miRNAs and their target genes, suggesting that changes in miRNA expression may cause aberrant expression of genes such as Creb1 and Caspase-3 in mice infected with S. japonicum.

Conclusions

Our study shows significant differences in the levels of circulating miRNAs between S. japonicum infected mice and uninfected mice. In particular, the altered levels of miR-706 and miR-134-5p were associated with altered levels of expression of the Caspase-3 and Creb1 genes, respectively, suggesting that circulating miRNAs may serve as important mediators of the pathology of hepatic schistosomiasis. Additionally, our results are expected to provide new insights for further understanding the mechanisms of schistosome-host interaction that may facilitate in the development of novel interventions for alleviating the symptom of S. japonicum infection as well as for preventing and treating schistosomiasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-0806-5) contains supplementary material, which is available to authorized users.

Sm29, but not Sm22.6 retains its ability to induce a protective immune response in mice previously exposed to a Schistosoma mansoni infection

Background

A vaccine against schistosomiasis would have a great impact in disease elimination. Sm29 and Sm22.6 are two parasite tegument proteins which represent promising antigens to compose a vaccine. These antigens have been associated with resistance to infection and reinfection in individuals living in endemic area for the disease and induced partial protection when evaluated in immunization trials using naïve mice.

Methodology/principals findings

In this study we evaluated rSm29 and rSm22.6 ability to induce protection in Balb/c mice that had been previously infected with S. mansoni and further treated with Praziquantel. Our results demonstrate that three doses of the vaccine containing rSm29 were necessary to elicit significant protection (26%–48%). Immunization of mice with rSm29 induced a significant production of IL-2, IFN-γ, IL-17, IL-4; significant production of specific antibodies; increased percentage of CD4+ central memory cells in comparison with infected and treated saline group and increased percentage of CD4+ effector memory cells in comparison with naïve Balb/c mice immunized with rSm29. On the other hand, although immunization with Sm22.6 induced a robust immune response, it failed to induce protection.

Conclusion/significance

Our results demonstrate that rSm29 retains its ability to induce protection in previously infected animals, reinforcing its potential as a vaccine candidate.

The development of a vaccine against schistosomiasis together with chemotherapy would have a great impact in the disease control and elimination. Sm29 and Sm22.6 are two promising antigens that have been associated with resistance to infection/reinfection in humans and also successfully induce protection in trials using C57BL/6 naïve mice. Despite the great results observed in C57BL/6 naïve mice, rSm29 and rSm22.6 ability to induce protection has never been assessed in mice previously exposed to the parasite antigens. In the case of schistosomiasis, this is an important assessment to be done, since the residents of endemic areas, the population mostly affected by the disease, are exposed to several infections through life. Here we evaluated these antigens in immunization trials using mice that had been submitted to a previous infection and treatment with Praziquantel. Both antigens induced a robust immune response triggering both cellular and humoral responses, but only rSm29 was able to induce a significant reduction on parasite burden and increased percentage of CD4+ memory cells. Our date reinforce Sm29 potential to compose an anti-schistosomiasis vaccine.

Parasites alter the pathological phenotype of lupus nephritis

lpr

Lupus nephritis is one of the most serious complications of systemic lupus erythematosus and manifests with considerable phenotypic and histological heterogeneity. In particular, diffuse proliferative lupus nephritis (DPLN) and membranous lupus nephritis (MLN) represent morphologic forms that are polar opposites. DPLN is associated with autoimmune responses dominated by Th1 immune response associated with high levels of interferon (IFN)-γ. In contrast, a Th2 cytokine response is associated with the pathogenesis of MLN. MRL/lpr mice develop human LN-like immune complex-associated nephritis and provide a suitable histological model for human DPLN. Infection with Schistosoma mansoni skewed a Th2-type immune response induction and IL-10 in MRL/lpr mice, drastically changing the pathophysiology of glomerulonephritis from DPLN to MLN accompanied by increased IgG1 and IgE in the sera. T cells in 32-week-old MRL/lpr mice infected with S. mansoni expressed significantly more IL-4 and IL-10 than T cells of uninfected mice; T cells with IFN-γ were comparable between infected and uninfected MR/lpr mice. Thus, the helminthic infection modified the cytokine microenvironment and altered the pathological phenotype of autoimmune nephritis.

Cytokine responses to the anti-schistosome vaccine candidate antigen glutathione-S-transferase vary with host age and are boosted by praziquantel treatment

Background

Improved helminth control is required to alleviate the global burden of schistosomiasis and schistosome-associated pathologies. Current control efforts rely on the anti-helminthic drug praziquantel (PZQ), which enhances immune responses to crude schistosome antigens but does not prevent re-infection. An anti-schistosome vaccine based on Schistosoma haematobium glutathione-S-transferase (GST) is currently in Phase III clinical trials, but little is known about the immune responses directed against this antigen in humans naturally exposed to schistosomes or how these responses change following PZQ treatment.

Methodology

Blood samples from inhabitants of a Schistosoma haematobium-endemic area were incubated for 48 hours with or without GST before (n = 195) and six weeks after PZQ treatment (n = 107). Concentrations of cytokines associated with innate inflammatory (TNFα, IL-6, IL-8), type 1 (Th1; IFNγ, IL-2, IL-12p70), type 2 (IL-4, IL-5, IL-13), type 17 (IL-17A, IL-21, IL-23p19) and regulatory (IL-10) responses were quantified in culture supernatants via enzyme-linked immunosorbent assay (ELISA). Factor analysis and multidimensional scaling were used to analyse multiple cytokines simultaneously.

Principal Findings

A combination of GST-specific type 2 (IL-5 and IL-13) and regulatory (IL-10) cytokines was significantly lower in 10–12 year olds, the age group at which S. haematobium infection intensity and prevalence peak, than in 4–9 or 13+ year olds. Following PZQ treatment there was an increase in the number of participants producing detectable levels of GST-specific cytokines (TNFα, IL-6, IL-8, IFNγ, IL-12p70, IL-13 and IL-23p19) and also a shift in the GST-specific cytokine response towards a more pro-inflammatory phenotype than that observed before treatment. Participant age and pre-treatment infection status significantly influenced post-treatment cytokine profiles.

Conclusions/Significance

In areas where schistosomiasis is endemic host age, schistosome infection status and PZQ treatment affect the cellular cytokine response to GST. Thus the efficacy of a GST-based vaccine may also be shaped by the demographic and epidemiological characteristics of targeted populations.

Schistosomiasis is caused by infection with Schistosoma spp. parasites, for which the main treatment is the drug praziquantel (PZQ). Since PZQ does not prevent reinfection, an anti-schistosome vaccine based on the Schistosoma haematobium enzyme glutathione-S-transferase (GST) is being developed. In this study we investigated the GST-specific immune responses of people naturally exposed to schistosomes and the affect that PZQ has on these responses. We cultured blood samples from a schistosome-exposed community with GST before and six weeks after PZQ treatment and measured a range of soluble proteins (cytokines) in culture supernatants as indicators of blood cell activation and phenotype. Before treatment, GST-specific cytokine responses varied with host age, particularly in children with high intensity schistosome infections. Following treatment, GST activated blood samples from more individuals to produce a broader range of cytokines and the combination of GST-specific cytokine responses reflected a more pro-inflammatory immune phenotype than that observed pre-treatment. Post-treatment responses varied according to host age and pre-treatment infection status. Taken together, our study suggests that current and future GST-based vaccine trials should take host age, schistosome infection status and PZQ treatment history into account since these factors influence GST-specific immune activation.

Transcriptional profiles of cytokine/chemokine factors of immune cell-homing to the parasitic lesions: a comprehensive one-year course study in the liver of E. multilocularis-infected mice

Pathogenesis of chronically developing alveolar echinococcosis (AE) is characterized by a continuous, granulomatous, periparasitic infiltration of immune cells surrounding the metacestode of Echinococcus multilocularis (E.multilocularis) in the affected liver. A detailed cytokine and chemokine profile analysis of the periparasitic infiltrate in the liver has, however, not yet been carried out in a comprehensive way all along the whole course of infection in E. multilocularis intermediate hosts. We thus assessed the hepatic gene expression profiles of 18 selected cytokine and chemokine genes using qRT-PCR in the periparasitic immune reaction and the subsequent adjacent, not directly affected, liver tissue of mice from day 2 to day 360 post intra-hepatic injection of metacestode. DNA microarray analysis was also used to get a more complete picture of the transcriptional changes occurring in the liver surrounding the parasitic lesions. Profiles of mRNA expression levels in the hepatic parasitic lesions showed that a mixed Th1/Th2 immune response, characterized by the concomitant presence of IL-12α, IFN-γ and IL-4, was established very early in the development of E. multilocularis. Subsequently, the profile extended to a combined tolerogenic profile associating IL-5, IL-10 and TGF-β. IL-17 was permanently expressed in the liver, mostly in the periparasitic infiltrate; this was confirmed by the increased mRNA expression of both IL-17A and IL-17F from a very early stage, with a subsequent decrease of IL-17A after this first initial rise. All measured chemokines were significantly expressed at a given stage of infection; their expression paralleled that of the corresponding Th1, Th2 or Th17 cytokines. In addition to giving a comprehensive insight in the time course of cytokines and chemokines in E. multilocularis lesion, this study contributes to identify new targets for possible immune therapy to minimize E. multilocularis-related pathology and to complement the only parasitostatic effect of benzimidazoles in AE.

Cytokine Pattern of T Lymphocytes in Acute Schistosomiasis mansoni Patients following Treated Praziquantel Therapy

Acute schistosomiasis is associated with a primary exposure and is more commonly seen in nonimmune individuals traveling through endemic regions. In this study, we have focused on the cytokine profile of T lymphocytes evaluated in circulating leukocytes of acute Schistosomiasis mansoni-infected patients (ACT group) before and after praziquantel treatment (ACT-TR group). Our data demonstrated increased values of total leukocytes, eosinophils, and monocytes in both groups. Interestingly, we have observed that patients treated with praziquantel showed increased values of lymphocytes as compared with noninfected group (NI) or ACT groups. Furthermore, a decrease of neutrophils in ACT-TR was observed when compared to ACT group. Analyses of short-term in vitro whole blood stimulation demonstrated that, regardless of the presence of soluble Schistosoma mansoni eggs antigen (SEA), increased synthesis of IFN-γ and IL-4 by T-cells was observed in the ACT group. Analyses of cytokine profile in CD8 T cells demonstrated higher percentage of IFN-γ and IL-4 cells in both ACT and ACT-TR groups apart from increased percentage of IL-10 cells only in the ACT group. This study is the first one to point out the relevance of CD8 T lymphocytes in the immune response induced during the acute phase of schistosomiasis.

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.

Concurrent urinary and intestinal schistosomiasis and intestinal helminthic infections in schoolchildren in Ilobu, South-western Nigeria

A cross-sectional study was conducted in a schistosome-endemic rural community in Southwestern Nigeria. We assessed prevalence and intensity of soil-transmitted nematodes and the co-occurrence with Schistosoma haematobium and Schistosoma mansoni. Urine and stool samples from 419 schoolchildren were examined, and a questionnaire was administered to obtain socio-demographic characteristics. In total, 78.3% (328/419) were infected with at least one helminth species, with a prevalence (mean egg-count) of 55.1% (3069.2) of Ascaris lumbricoides, 41.1% (127.5) of S. haematobium, 22.7% (98.6) of hookworms, 17.9% (161.3) of Trichuris trichiura, and 10.3% (12.9) of S. mansoni. Multiple infections were significantly more common among children from households with more playmates, absence of toilet facilities and low income level (all p<0.001). Children with heavy hookworm burden were at a significantly higher chance of acquiring S. mansoni (OR=36.35; 95% Cl: 13.22-100.97; p<0.0001). The risk of S. mansoni and A. lumbricoides infections was increased in co-infections with S. haematobium. Logistic regression analysis revealed infections by hookworms and S. mansoni (adjusted odds ratio [aOR]=3.90, 95% Cl: 2.03-7.46; p<0.0001), and by hookworms and T. trichiura (aOR=2.46, 95% Cl: 1.44-4.22; p=0.001) as significant risk factors for multiple infections. Our study shows that polyparasitism is common in the study area. Focused interventions such as mass treatment with anthelminthics and health education are needed to improve the well-being of the affected population.

Parasites induced skin allergy: a strategic manipulation of the host immunity

The absence of a consistent link between parasitoses and skin allergic symptoms in the clinical investigations contrasts to the fact that some parasites are the most potent inducers of immunoglobulin E that exist in nature. To shed some light into this question, this review is focused on the actual knowledge regarding parasites life cycle, interactions with host immunity, the influence on host behavior, and finally the role of all these factors on the skin allergy. The collected data demonstrate that parasites could manipulate the host behavior for its own benefit in different ways, altering its (epi)genetic, biochemical, immunologic or physiologic functions as well as altering its behavior and activity. In this context, skin allergy may be associated with certain stages of the parasites' life cycle and migration into biological barriers, but not necessarily with presence of the parasitosis in the host organism. As compared to T helper (Th) 1 response, the Th2 one, the eosinophilic infiltration and the complement inhibition could assure better conditions for the development of some parasites. Taken together, the suggested hypotheses could be a plausible explanation for the epidemiological puzzle regarding urticaria occurrence, Th2 response and parasitoses, but further studies are necessary to provide better-based conclusions.

KEYWORDS

Eosinophilic Infiltration; Host behavior; Parasites life cycle; Skin allergy; Th1/Th2 response.

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

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

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

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

Regulatory and activated T cells in human Schistosoma haematobium infections

Acquired immunity against helminths is characterised by a complex interplay between the effector Th1 and Th2 immune responses and it slowly manifests with age as a result of cumulative exposure to parasite antigens. Data from experimental models suggest that immunity is also influenced by regulatory T cells (Treg), but as yet studies on Treg in human schistosome infections are limited. This study investigated the relationship between schistosome infection intensity and the two cell populations regulatory T cells (TREG: CD4(+(dim))CD25(+(high))FOXP3(+)CD127(low)), and activated (Tact: CD4(+)CD25(+)FOXP3(-)) T cells in Zimbabweans exposed to Schistosoma haematobium parasites. Participants were partitioned into two age groups, young children (8-13 years) in whom schistosome infection levels were rising to peak and older people (14+ years) with declining infection levels. The relationship between Tact proportions and schistosome infection intensity remained unchanged with age. However Treg proportions rose significantly with increasing infection in the younger age group. In contrast Treg were negatively correlated to infection intensity in the older age group. The relative proportions of regulatory T cells differ significantly between young individuals in whom high infection is associated with an enhanced regulatory phenotype and older infected patients in whom the regulatory response is attenuated. This may influence or reflect different stages of the development of protective schistosome acquired immunity and immunopathogenesis.

Use of a saline gradient for the diagnosis of schistosomiasis

The development of novel methods for parasitological diagnosis that are both highly sensitive and low in cost has been strongly recommended by the World Health Organization. In this study, a new technique for diagnosis of schistosomiasis mansoni is proposed based on the differential sedimentation of eggs when subjected to a slow continuous flux of 3% saline solution through a porous plaque. This influx suspends low-density faecal material, effectively cleaning the sample. The remaining sediment covering the porous plaque surface is then transferred to a glass slide and examined under a bright field microscope. Twelve Kato-Katz slides were used for comparison in the present study. Our results suggest that the saline gradient method detects a significantly higher number of eggs than the 12 Kato-Katz slides (p < 0.0001). We also found microscopic inspection to be quicker and easier with our newly described method. After cleaning the sample, the obtained sediment can also be conserved in a 10% formaldehyde solution and examined for at least 45 days later without statistically significant egg count differences.

Schistosoma mansoni antigens modulate the allergic response in a murine model of ovalbumin-induced airway inflammation

Schistosoma mansoni infection has been associated with protection against allergies. The mechanisms underlying this association may involve regulatory cells and cytokines. We evaluated the immune response induced by the S. mansoni antigens Sm22.6, PIII and Sm29 in a murine model of ovalbumin (OVA)-induced airway inflammation. BALB/c mice were sensitized with subcutaneously injected OVA-alum and challenged with aerolized OVA. Mice were given three doses of the different S. mansoni antigens. Lung histopathology, cellularity of bronchoalveolar lavage (BAL) and eosinophil peroxidase activity in lung were evaluated. Immunoglobulin (Ig)E levels in serum and cytokines in BAL were also measured. Additionally, we evaluated the frequency of CD4+forkhead box P3 (FoxP3)+ T cells in cultures stimulated with OVA and the expression of interleukin (IL)-10 by these cells. The number of total cells and eosinophils in BAL and the levels of OVA-specific IgE were reduced in the immunized mice. Also, the levels of IL-4 and IL-5 in the BAL of mice immunized with PIII and Sm22.6 were decreased, while the levels of IL-10 were higher in mice immunized with Sm22.6 compared to the non-immunized mice. The frequency of CD4+FoxP3+ T cells was higher in the groups of mice who received Sm22.6, Sm29 and PIII, being the expression of IL-10 by these cells only higher in mice immunized with Sm22.6. We concluded that the S. mansoni antigens used in this study are able to down-modulate allergic inflammatory mediators in a murine model of airway inflammation and that the CD4+FoxP3+ T cells, even in the absence of IL-10 expression, might play an important role in this process.

Schistosoma mansoni infection in a rural area of the Jequitinhonha Valley, Minas Gerais, Brazil: analysis of exposure risk

This study examines the relative contribution of age-specific total IgE levels, eosinophils and water contact behavior to the prevalence and intensity (geometric mean egg counts) of Schistosoma mansoni infection in the poor rural population of Virgem das Graças in northern Minas Gerais State. In bivariate analysis, age was strongly correlated with both prevalence and intensity of infection, while eosinophil levels with prevalence only (p<0.0001); IgE levels and 5 demographic and socioeconomic variables were moderately correlated with prevalence (p<0.05), as were number of persons per room and TBM (total body minutes) with egg counts. In multivariate analysis, after controlling for demographic and socioeconomic factors, only total IgE levels were significantly correlated with both prevalence (p=0.248, 95% CI=1.01-1.11) and intensity (p=0.0217, 95% CI=0.01-0.14) of infection and eosinophil levels with prevalence (p=0.0005, 95% CI=1.07-1.24). Although any causal relationship cannot be confirmed by a cross-sectional study, we demonstrated an associated decrease in prevalence and intensity of S. mansoni infection with increased IgE levels.

Schistosoma mansoni infection alters co-stimulatory molecule expression and cell activation in asthma

Chronic schistosomiasis induces Th2/T regulatory responses which are able to down-modulate allergic inflammation and asthma. Because co-stimulatory molecules and IL-10 are essential for inducing tolerance, the aim of this study was to determine by flow cytometry, the expression of CD28, CTLA4, CD40L, CD80, CD86, HLA-DR, IL-10 and IL-10 receptor, by mononuclear cells from asthmatic individuals infected with Schistosoma mansoni and compare with non-infected individuals. Peripheral blood mononuclear cells were stained with fluorochrome conjugated antibodies for the expression of co-stimulatory molecules, and for intracellular CTLA4 and IL-10 expression. There was no significant difference in the frequency of T cells expressing CD28 between the two groups. However, the frequency of TCD4(+) cells expressing CTLA4 and CD40L was higher in infected asthmatics. The frequency of monocytes expressing CD80 and CD86 did not differ between groups, while the expression of HLA-DR and IL-10 receptor was higher on monocytes of infected individuals. Furthermore, monocytes and CD4(+)CD25(+) cells of infected individuals expressed higher levels of IL-10. We conclude that, besides alternatively-activated monocytes that are, together with CD4(+)CD25(+) cells, important sources of IL-10, CTLA4 and CD40L expression may also participate in the down-modulation of inflammatory allergic response in S. mansoni-infected asthmatics.

Immuno-epidemiology of Schistosoma mansoni infections in endemic populations co-infected with soil-transmitted helminths: present knowledge, challenges, and the need for further studies

This article reviews studies on epidemiological and immunological interactions between Schistosoma mansoni and soil-transmitted helminths (STH) in co-infected patients from endemic areas. In Brazil, co-infections with schistosomes and intestinal nematodes, such as Ascaris lumbricoides, Trichuris trichiura and the hookworms, are still common, especially in poor rural areas. Important factors in the co-occurrence of different helminth species are favorable environmental conditions supporting intermediate hosts and the survival of larval stages outside the human host, widespread poverty, and low levels of hygiene and sanitation. The few existing epidemiological surveys on helminth co-infections in humans indicate positive associations between schistosomes and STH, which means high prevalences of mixed infections, as well as higher intensities of infection in co-infected patients. However, these positive interactions appear to depend on the number of different helminth species present and on the intensity of infection in each individual. For the humoral immune response in co-infected patients, much cross-reactivity in antibody responses against antigenic preparations from schistosomes and STH is observed. Data on cellular immune responses in multiply infected patients are still scarce and additive effects on the cellular reactivity and the down-modulation of cytokines are proposed.

Immune response and pathogenesis of neuroschistosomiasis mansoni

The involvement of the central nervous system (CNS) by schistosomes may or may not determine clinical manifestations. When symptomatic, neuroschistosomiasis (NS) is one of the most severe presentations of schistosome infection. Considering the symptomatic form, Schistosoma mansoni causes almost always spinal cord disease. Cerebral and spinal cord disorders in S. mansoni infections are inflammatory conditions of the CNS that cause mild-moderate impairment of the blood-brain barrier and intrathecal synthesis of antibodies against schistosomal antigens. Little is known about the pathogenesis of NS, but available evidence strongly suggests that it depends basically on the presence of parasite eggs in the nervous tissue and on the host's immune response against the trapped eggs. Numerous eggs surrounded by granulomas lodged together in circumscribed areas of the CNS damage the nervous tissue by both the mass effect and the egg-induced inflammatory reaction. Vasculitis of immune etiology, which causes isquemic lesions, may also play an important role in the genesis of the neurological symptoms. Although the mechanisms involved in the immunophatogenesis of NS are largely unknown, initial investigations on cerebrospinal fluid (CSF) and serum cytokine profiles suggest the occurrence of inflammation as well as a skewed Th2 immune response that probably occur both locally and systemically.

Eosinophil activation status, cytokines and liver fibrosis in Schistosoma mansoni infected patients

We have been investigating whether human eosinophils play an important role in schistosomiasis mansoni morbidity. Our main focus has been on the activation-related cell surface markers (CD23/CD69/CD25/HLA-DR/CD28/CD80) and the detection of TNF-alpha, IL-4 and IL-5 in peripheral blood eosinophils from chronic Schistosoma mansoni-infected patients. Our studies compare both, intestinal (INT) and individuals with periportal fibrosis (FIB). Our major findings, point to distinct profile of activation-related surface markers on eosinophils as the hallmark of disease morbidity during chronic S. mansoni infection. Up-regulation of several activation-related markers was observed on eosinophils from FIB group, but not INT, which include early activation markers, such as CD69 and CD23. INT displayed a distinct profile, with up-regulation of molecules related to the late activation (CD25, HLA-DR, CD28 and CD80). These results suggest that some immunoregulatory events may take place controlling the early eosinophil activation in the INT group. Higher levels of eosinophil-derived cytokines were observed in FIB, regardless the antigen stimulation in vitro. A mixed cytokine pattern, characterized by positive correlation between TNF-alpha, IL-4 and IL-5 was observed in both INT and FIB. However, lack of correlation between the cytokine expression and the eosinophil activation status points out that even those FIB patients presenting minor increment on eosinophil activation displayed higher levels of cytokine-positive eosinophils. Indeed, the positive association between lymphocyte-derived IL-10 and the eosinophils cytokine profile was observed exclusively in INT further emphasize our hypothesis that immunoregulatory events take place controlling disease morbidity in human schistosomiasis. The impaired IL-10-driven immunoregulatory function may play an important role on the establishment of pathology in patients bearing periportal fibrosis.

The predicted impact of immunosuppression upon population age-intensity profiles for schistosomiasis

The slow development of acquired immunity is thought to be responsible for the characteristic convex age-intensity curve seen in human schistosome infection, which peaks earlier in more heavily infected populations (this is described as a peak shift). Schistosomes are able to suppress protective host responses, and it is hypothesized that this suppression is responsible for the delayed development of protective responses. A deterministic mathematical model is used to describe levels of infection and immunity in an endemic population, incorporating protective immune responses which either reduce adult worm burden or reduce superinfection. Suppression, related to current worm burden, is also included and acts against one or both protective responses. If suppression acts against the entire protective response, it is able to delay the development of protective immunity, and the peak shift is predicted to be reversed at higher infection intensities, with removal of the peaks altogether at the highest levels of infection and/or suppression. If only the anti-adult worm protective immune response is vulnerable to suppression, while the anti-reinfection response remains intact, then suppression does not remove the peak in the age-intensity curve. These findings are discussed in the light of existing field and experimental data.

Antibody and cytokine responses in Dracunculus medinensis patients at distinct states of infection

Dracunculiasis is a promising candidate for eradication, but transmission of Dracunculus medinensis and recrudescence of the disease have been observed repeatedly. In the present investigation, the D. medinensis-specific cellular cytokine response profiles and the parasite-specific antibody subclass reactivity were evaluated in dracunculiasis patients at distinct states of infection. Analysis of the cellular cytokine response in dracunculiasis patients disclosed a D. medinensis antigen-specific depression of IFN-gamma production with patent D. medinensis infection, while the T helper type 2 cytokine IL-10 was similar in patent, post-patent and control individuals, and IL-5 production was always the highest in controls. In parallel, diminished IFN-gamma and IL-12 responses to antigens from Ascaris lumbricoides, Entamoeba histolytica and mycobacteria were observed in patent and post-patent dracunculiasis cases. The parasite-specific IgG(1) and IgG(4) subclass reactivity profiles corresponded with the D. medinensis infection state, and a clear distinction between patent and post-patent patients and controls was found. Overall a depressed cytokine release was observed with patent D. medinensis, which extended beyond the parasite-specific immune responsiveness. The detection of D. medinensis-specific IgG(1) and IgG(4) isotypes may help to distinguish newly exposed, patent and post-patent D. medinensis infections.

Cytokine responses to Schistosoma haematobium in a Zimbabwean population: contrasting profiles for IFN-gamma, IL-4, IL-5 and IL-10 with age

BACKGROUND

The rate of development of parasite-specific immune responses can be studied by following their age profiles in exposed and infected hosts. This study determined the cytokine-age profiles of Zimbabweans resident in a Schistosoma haematobium endemic area and further investigated the relationship between the cytokine responses and infection intensity.

METHODS

Schistosome adult worm antigen-specific IFN-gamma, IL-4, IL-5 and IL-10 cytokine responses elicited from whole blood cultures were studied in 190 Zimbabweans exposed to S. haematobium infection (aged 6 to 40 years old). The cytokines were measured using capture ELISAs and the data thus obtained together with S. haematobium egg count data from urine assays were analysed using a combination of parametric and nonparametric statistical approaches.

RESULTS

Age profiles of schistosome infection in the study population showed that infection rose to peak in childhood (11-12 years) followed by a sharp decline in infection intensity while prevalence fell more gradually. Mean infection intensity was 37 eggs/10 ml urine (SE 6.19 eggs/10 ml urine) while infection prevalence was 54.7%. Measurements of parasite-specific cytokine responses showed that IL-4, IL-5 and IL-10 but not IFN-gamma followed distinct age-profiles. Parasite-specific IL-10 production developed early, peaking in the youngest age group and declining thereafter; while IL-4 and IL-5 responses were slower to develop with a later peak. High IL-10 producers were likely to be egg positive with IL-10 production increasing with increasing infection intensity. Furthermore people producing high levels of IL-10 produced little or no IL-5, suggesting that IL-10 may be involved in the regulation of IL-5 levels. IL-4 and IFN-gamma did not show a significant relationship with infection status or intensity and were positively associated with each other.

CONCLUSION

Taken together, these results show that the IL-10 responses develop early compared to the IL-5 response and may be down-modulating immunopathological responses that occur during the early phase of infection. The results further support current suggestions that the Th1/Th2 dichotomy does not sufficiently explain susceptibility or resistance to schistosome infection.

Ageing and Toll-like receptor expression by innate immune cells in chronic human schistosomiasis

There has been no systematic study of the immune response of individuals aged over 60 years living in Schistosomiasis mansoni-endemic areas, although senescence is reportedly associated with susceptibility to infection and progressive decline in immune function. We have shown previously, in two endemic areas in Minas Gerais, Brazil, that the frequency of individuals aged over 60 years with chronic schistosomiasis is no longer negligible. Moreover, several elderly individuals who have always lived in these endemic areas stay protected from infection. An important question for studies of ageing and disease control in developing countries is which differences in the immunological profile of these negatively tested (non-infected) individuals can account for their resistance to either infection or reinfection. We show, in the present study, that non-infected (negative) elderly individuals develop innate immune mechanisms of protection that replace the age-associated decline in T cell function. Non-infected elderly individuals from endemic areas of schistosome infection present an increase in the frequency of the natural killer (NK) CD56(low) subset of NK cells expressing Toll-like receptors (TLR)-1, -2, -3 and -4 as determined by flow cytometry analysis. In addition, the proportion of dendritic cells expressing TLR-1 is elevated as well as the frequency of monocytes expressing TLR-1 and -4. These results suggest that TLR expression by cells of the innate immune system may be related to the negative status of infection in some elderly individuals who are constantly exposed to S. mansoni. Developing mechanisms of protection from infection may represent a biomarker for healthy ageing in this population.

Cytokine secretion profile associated with periportal fibrosis in S. mansoni-infected Egyptian patients

Periportal fibrosis (PPF) is a major pathological consequence of S. mansoni infection. Ultrasonography is a well-established tool for diagnosis and grading of schistosomiasis-related pathology. This work is performed to study the effect of schistosomiasis mansoni infection on the cytokine secretion profile in S. mansoni-infected patients at various grades of fibrosis, as determined by ultrasonography using Cairo Working Group classification. The levels of IL-2, IL-4, IL5, IL-10, IFN-gamma, and TNF-alpha were measured in the absence of in vitro antigen stimulation and after stimulation with worm and egg antigens. Simple intestinal (INT) patients are characterized by strong proliferation to worm antigen and high levels of IL-10 and TNF-alpha compared to patients at various grades of infection. GradeII (GdII)-infected patients are characterized by higher IL-5 production than are patients with other clinical forms of the disease. Sharp reduction of almost all cytokines in response to both worm and egg antigens was detected in GdIII-infected patients. These results stressed the role of both IL-10 and TNF-alpha in the early stages of hepatic fibrosis, while IL-5 could be employed as a potential predictive marker for advanced stages. In conclusion, PPF is associated with cytokine production profiles that vary with the magnitude of the fibrosis.

Worms and allergy

Worms and asthma are associated with a type 2 immune response, but evidence has accumulated that helminth infection is negatively associated with atopy, prevalence of allergic diseases and severity of asthma. One important difference between these polarized type 2 responses is that in allergy modulation of the immunological response is not appropriate, whereas in infection with helminths, several host mechanisms down-regulate the host immune response. As a result, patients infected with worms have a decrease in both type 1 and type 2 responses. The main mechanism involved in this down-modulation is increased production of IL-10, but expansion of regulatory T cells and NKT cells may also participate. Regarding the interaction between worms and allergy, a few variables need to be taken in account: phase (acute or chronic) of helminth infection, parasite load and species of helminth. In animals and humans, acute helminth infection may increase manifestations of allergy, whereas chronic infection with parasites decreases atopy. The modulation of the immune response by helminths is dependent on having an adequate parasite load. Moreover, although several helminth species have been shown to modulate immune responses, most in vitro and in vivo studies have focused on the importance of Schistosoma mansoni in down-modulating allergic reactions.

Intrathecal cytokines in spinal cord schistosomiasis

We investigate the cytokine profile in the cerebrospinal fluid (CSF) and serum of patients with spinal cord schistosomiasis (SCS). Increased levels of IL-1beta, IL-4, IL-6 and IL-10 and low concentrations of TNF-alpha and IFN-gamma were observed in both CSF and serum. CSF showed higher levels of IL-4 and IL-6 when compared to the paired serum samples. A negative correlation between the concentrations of IL-10 and IFN-gamma was observed in the CSF. These findings suggest an inflammatory as well as a skewed type-2 immune response that probably occur both locally and systemically and may be involved in the pathogenesis of SCS.

Identification of paramyosin T cell epitopes associated with human resistance to Schistosoma mansoni reinfection

Paramyosin, a Schistosoma mansoni myoprotein associated with human resistance to infection and reinfection, is a candidate antigen to compose a subunit vaccine against schistosomiasis. In this study, 11 paramyosin peptides selected by TEPITOPE algorithm as promiscuous epitopes were produced synthetically and tested in proliferation and in vitro human leucocyte antigen (HLA)-DR binding assays. A differential proliferative response was observed in individuals resistant to reinfection compared to individuals susceptible to reinfection in response to Para (210-226) peptide stimulation. In addition, this peptide was able to bind to all HLA-DR molecules tested in HLA-DR binding assays, confirming its promiscuity. Para (6-22) and Para (355-371) were also shown to be promiscuous peptides, because they were able to bind to the six and eight most prevalent HLA-DR alleles used in HLA-DR binding assays, respectively, and were also recognized by T cells of the individuals studied. These results suggest that these paramyosin peptides are promising antigens to compose an anti-schistosomiasis vaccine.

Production of interferon-gamma by natural killer cells and aging in chronic human schistosomiasis

BACKGROUND

Aging is associated with several alterations in the phenotype, repertoire and activation status of lymphocytes as well as in the cytokine profile produced by these cells. As a lifelong condition, chronic parasitic diseases such as human schistosomiasis overlaps with the aging process and no systematic study has yet addressed the changes in immune response during infection with Schistosoma mansoni in older individuals.

AIM

Herein we study the influence of immunological alterations brought about by senescence in the course of schistosomiasis.

MATERIALS AND METHODS

Individuals 10-95 years of age, from both sexes, from an endemic area for S. mansoni infection were matched by intensity of infection as measured by egg counts. We analyzed, as a parameter, cytokine expression by lymphocytes and natural killer cells after in vitro stimulation with soluble egg antigen and soluble worm antigen using flow cytometry.

RESULTS

We demonstrated that the frequency of CD16+ interferon-gamma (IFN-gamma)+ natural killer cells in negative individuals over the age of 70 years is significantly higher than in positive individuals after in vitro stimulation with S. mansoni antigen extracts. The frequency of these cells is increased in all individuals over the age of 50 years and only declines in positive individuals after 70 years of age. Analysis of either CD4? or CD8? cells after antigen stimulation show no significant increase in frequency of IFN-gamma in negative or in positive individuals of this age group, suggesting that the effect on CD16+ cells is not T-cell dependent.

CONCLUSION

Since production of IFN-gamma has been related to resistance to schistosome infection, our data suggest that age-associated changes in CD16+ cells may play a role in controlling infection intensity in the elderly in S. mansoni endemic areas of Brazil.

Establishment of Schistosoma japonicum calpain-specific mouse T cell hybridomas and identification of a T cell epitope that stimulates IFNγ production

Calpain is a calcium-dependent cystein protease, and the homologues of schistosome are known as one of vaccine candidate molecules against schistosomiasis. Here, we established two IL-2 producing T cell hybridoma cell lines specific for Schistosoma japonicum calpain, to identify T cell epitope(s) on the molecule. Overlapping 15mer oligopeptides of calpain were synthesized and tested for their stimulatory abilities to the hybridomas. As a result, epitopes recognized by the two hybridoma lines were the same: EQLKIYAQRC. Spleen cells from calpain multiple antigenic peptide (MAP)-immunized BALB/c mice produced IFNgamma upon stimulation with MAP or soluble worm antigen preparation (SWAP). The identification of the T cell epitope to stimulate Th1 response will contribute to the proper design of synthetic vaccines, evaluation of their protective potentials and elucidation of protective mechanisms in murine experimental schistosomiasis.

Chronic immune activation associated with chronic helminthic and human immunodeficiency virus infections: role of hyporesponsiveness and anergy

Chronic immune activation is one of the hallmarks of human immunodeficiency virus (HIV) infection. It is present also, with very similar characteristics, in very large human populations infested with helminthic infections. We have tried to review the studies addressing the changes in the immune profiles and responses of hosts infected with either one of these two chronic infections. Not surprisingly, several of the immune derangements and impairments seen in HIV infection, and considered by many to be the "specific" effects of HIV, can be found in helminth-infected but HIV-noninfected individuals and can thus be accounted for by the chronic immune activation itself. A less appreciated element in chronic immune activation is the immune suppression and anergy which it may generate. Both HIV and helminth infections represent this aspect in a very wide and illustrative way. Different degrees of anergy and immune hyporesponsiveness are present in these infections and probably have far-reaching effects on the ability of the host to cope with these and other infections. Furthermore, they may have important practical implications, especially with regard to protective vaccinations against AIDS, for populations chronically infected with helminths and therefore widely anergic. The current knowledge of the mechanisms responsible for the generation of anergy by chronic immune activation is thoroughly reviewed.

Cytokine production in whole blood cultures from a fishing community in an area of high endemicity for Schistosoma mansoni in Uganda: the differential effect of parasite worm and egg antigens

The human host is continuously exposed to the egg and the adult worm developmental stages of Schistosoma mansoni during chronic infections with the parasite. To assess the cytokine responses induced by these different costimulating stages and how they are influenced by host age and infection intensity, whole blood samples from a cross-sectional cohort of 226 members of a Ugandan fishing community who had been resident in an area with high transmission of S. mansoni for the previous 10 years or from birth were stimulated with S. mansoni egg antigen (SEA) or worm antigen (SWA). SWA-specific gamma interferon (IFN-gamma) production increased with age, and the levels of SWA- and SEA-specific interleukin 3 (IL-3) were weakly correlated with schistosome infection intensity. The production of most cytokines was little affected by age or infection intensity but was either SEA or SWA specific. One hundred thirty-two members of the cohort coproduced IL-5 and IL-13 specifically in response to SWA, whereas only 15 produced these cytokines, and at much lower levels, in response to SEA. IL-10, IL-4, and IFN-gamma were also produced in response to SWA, whereas the response to SEA consisted almost exclusively of IL-10. Our results suggest that, in contrast to what has been described for the murine model of S. mansoni and during acute human infections, chronic intense exposure to and infection with S. mansoni in this cohort resulted in very low levels of response to SEA in vitro in the presence of a vigorous and mixed Th1-Th2 response to SWA.

Genome and genomics of schistosomes

Schistosomes infect over 200 million people and 600 million are at risk. Genomics and post-genomic studies of schistosomes will contribute greatly to developing new reagents for diagnostic purposes and new vaccines that are of interest to the biotechnology industry. In this review, the most recent advances in these fields as well as new projects and future perspectives will de described. A vast quantity of data is publicly available, including short cDNA and genomic sequences, complete large genomic fragments, and the mitochondrial genomes of three species of the genus Schistosoma. The physical structure of the genome is being studied by physically mapping large genomic fragments and characterizing the highly abundant repetitive DNA elements. Bioinformatic manipulations of the data have already been carried out, mostly dealing with the functional analysis of the genes described. Specific search tools have also been developed. Sequence variability has been used to better understand the phylogeny of the species and for population studies, and new polymorphic genomic markers are currently being developed. The information generated has been used for the development of post-genomic projects. A small microarray detected genes that were differentially expressed between male and female worms. The identification of two-dimensional spots by mass spectrometry has also been demonstrated.

Are the cellular immune responses of children and adults with Schistosoma mansoni infection intrinsically different? Cytokines produced ex vivo in response to antigens and mitogens

In recently exposed communities, intensity of schistosomiasis infection increases as children age and then drops again in adulthood, indicating that host maturity is an important aspect of resistance to schistosomiasis. We investigated whether the cellular immune response to the parasite was correlated with age in subjects with similar daily patterns of exposure, current intensities of infection and number of years of exposure. The cellular immune response of subjects with either 'low' (under 200 eggs per gram (EPG)) or 'high' (over 400 EPG) intensities of infection was investigated, in a recently established focus where subjects had similar histories of exposure and number of years of experience with Schistosoma mansoni. Subject's whole blood was cultured with adult worm antigen (AWA), a mixture of phytohaemagglutinin (PHA) and lipopolysaccharide (LPS), or left unstimulated, and culture supernatants were tested for IL-4, IL-5, IL-10 and IFN-gamma. Children and adults tended to respond differently to schistosome antigen. The most statistically significant illustration of this was the negative correlation between age and IL-5 produced by samples from people with low intensities of infection cultured with AWA (P < 0.003, P < 0.05 after Bonferroni correction). IL-10 produced by samples cultured with PHA and LPS was also notably lower in children than in adults, although not formally significant after Bonferroni correction. This indicates that it is possible for age, independently of intensity of infection or experience with the parasite, to influence the immune response to schistosomiasis.

Esquitossomose mansônica hepatoesplênica humana: produção de TNF-alfa em monócitos

OBJETIVO: Investigar os níveis de liberação de TNF-alfa?em cultura de monócitos em portadores humanos da forma hepatoesplênica de esquistossomose mansônica. MÉTODO: Foram incluídos aleatoriamente, no estudo, 39 voluntários de idades variando entre 15 e 31 anos, 19 homens e 20 mulheres, divididos em três grupos. Grupo 1 (GC) 12 indivíduos sadios, sem esquistossomose. Grupo 2 (AI) 18 indivíduos portadores de esquistossomose mansônica na forma hepatoesplênica, que tinham se submetido a esplenectomia, ligadura da veia gástrica esquerda e auto-implante de tecido esplênico no omento maior, quando tinham idades entre 7 e 16 anos. Esses pacientes receberam oxaminiquine na dose de 20mg/kg 30 dias antes do procedimento cirúrgico. O seguimento médio atual é de cerca de 8 anos. Grupo 3 - pacientes esplenectomizados sem auto-implante esplênico (ESAI) constituído de nove adultos jovens que tinham se submetido à esplenectomia sem auto-implante esplênico e desconexão ázigo-porta. Os pacientes esquistossomóticos dos grupos 2 e 3 tiveram confirmação dessa doença pela presença de fibrose de Symmers nas biópsias hepáticas realizadas durante o ato cirúrgico. Foram colhidos 6 ml de sangue periférico de cada um dos voluntários incluídos no presente estudo, cujos monócitos foram separados por centrifugação e cultivados no meio de cultura CultilabÒ). Amostras de 100ml do sobrenadante da cultura de monócitos (10(6) células/ml), de cada indivíduo dos três grupos, eram colhidos para determinação das concentrações de TNF-alfa. Essa concentração era mensurada pelo estudo colorimétrico de ELISA para citocinas (QuanticininasTM - Sistema R&D), após 4 horas de estimulação com PMA e incubação, em uma atmosfera úmida com 5% de CO² a 37ºC. RESULTADOS: As concentrações de TNF-alfa? não diferiram significantemente nos três grupos estudados [(GC 135,0 ± 51,6 pg/ml; AI 97,0 ± 25,4 pg/ml e ESAI 107,0 ±. 52,1 pg/ml) - ANOVA, F = 0,210; p = 0,813]. CONCLUSÃO: Os achados contribuem para hipótese de que após esplenectomia com ou sem auto-implante esplênico a função dos monócitos, com relação a produção de TNF-alfa, mantém-se preservada.

P38 mitogen-activated protein kinase influence on the production of IL-10 in human schistosomiasis mansoni

Schistosomiasis mansoni remains a significant public health problem in many parts of the tropics and subtropics. Clinical manifestations range from the asymptomatic intestinal form through to the hepatosplenic form of the disease, a potentially lethal clinical condition in a subsection of the exposed population. In this study, we investigated the mechanisms by which interleukin (IL)-10 production could be differentially controlled in patients with the intestinal and hepatosplenic forms of the disease, as IL-10 may play a fundamental role in the development of the hepatosplenic disease state. It is reported that p38 mitogen-activated protein (MAP) kinase signalling, and in particular p38 MAPK activation, is central to IL-10 production of cells from patients with schistosomiasis. Furthermore, the difference in the levels of activated p38 MAPK and the activation transcription factor (ATF-2), may explain the difference in the amount of IL-10 produced by cells from intestinal and hepatosplenic patients. We suggest that the type of immune response triggered in patients with hepatosplenomegaly could be influenced by the levels of phosphorylated p38 MAPK.

Infection with Schistosoma mansoni correlates with altered immune responses to Ascaris lumbricoides and hookworm

Studies were performed on humoral and cellular immune responses of patients from areas in Brazil endemic for hookworm and Ascaris lumbricoides, and either endemic or non-endemic for Schistosoma mansoni. Humoral and cellular responses were evaluated by enzyme-linked immunosorbant assay (ELISA) and peripheral blood mononuclear cell (PBMC) proliferation assays against larval hookworm antigens, A. lumbricoides egg antigens, and soluble egg antigens (SEA) or soluble whole adult antigenic preparation (SWAP) from S. mansoni. Patients from S. mansoni-endemic areas, who currently had only hookworm or Ascaris infections, expressed lower humoral and cellular responses to hookworm or Ascaris antigens, respectively, than did their counterparts from areas not endemic for S. mansoni. Individuals from S. mansoni endemic area, although without detectable S. mansoni infection, do mount humoral and cellular responses to SEA and SWAP. This group of individuals has been probably in contact with S. mansoni antigens, since the groups harboring A. lumbricoides or hookworm infections from non-S. mansoni endemic areas do not have detectable anti-S. mansoni responses. PBMC proliferative responses discriminated well between patients with active hookworm infections versus ascariasis, if they were from areas not endemic for S. mansoni.

Th1-polarizing immunization with egg antigens correlates with severe exacerbation of immunopathology and death in schistosome infection

In schistosomiasis mansoni, parasite eggs precipitate an intrahepatic granulomatous and fibrosing inflammatory process, which is mediated by, and dependent on, MHC class II-restricted CD4 T helper (Th) lymphocytes specific for schistosome egg antigens (SEA). In the mouse model of the disease, CBA mice develop large granulomas, whereas in C57BL/6 (BL/6) mice these granulomas are significantly smaller. To further investigate how the prevailing cytokine environment influences the development of the egg-induced immunopathology, we immunized the low-pathology BL/6 mice with SEA in complete Freund's adjuvant (CFA) once before, and once again during, the course of a 7-week infection. This immunization caused a pronounced Th1 shift in the SEA-specific CD4 T cell response, which was detected in the mesenteric lymph nodes (MLNs) and spleens, as well as in the granulomatous lesions themselves. The immunized mice displayed a dramatic enhancement of hepatic egg-induced immunopathology manifested by a marked increase in granuloma size and parenchymal inflammation, leading to early death. Control mice immunized with equivalent amounts of SEA or CFA alone displayed the smaller hepatic lesions in a Th2-dominant environment typically seen in the unimmunized BL/6 mice. Analysis of granuloma and MLN lymphocytes from the SEA/CFA-immunized mice revealed that the proportion of CD4 T cells was unchanged in comparison with the control BL/6 groups and remained significantly lower than that seen in the normally high-pathology CBA strain. These results suggest that the shift toward Th1-type cytokine production by a numerically stable population of CD4 T cells correlates with severe exacerbation of immunopathology in schistosomiasis.

Cytokine responses to mitogen and Schistosoma haematobium antigens are different in children with distinct infection histories

Prevalence of Schistosoma haematobium infection in children from two neighbouring villages in Zimbabwe was 77.1% and 40.3%, respectively. The age-intensity data indicated peak intensities of infection at a lower age in the high prevalence village. This study investigated whether the difference in infection histories was reflected in a difference in cytokine profiles between children resident in these two villages. Blood samples were taken to assay for cytokine secretion 1 year after treatment for schistosomiasis. They were cultured with phytohaemagglutinin (PHA), schistosome egg antigens (SEA) or cultured without stimulant and tested for the presence of interleukin (IL)-4, IL-5, IL-10, granulocyte-macrophage colony-stimulating factor (GM-CSF) and IFN-gamma. Blood samples from children from the low prevalence village were more likely to produce IL-4 (P < 0.0001) and produced higher levels of IFN-gamma (P < 0.02) and GM-CSF (P < 0.03) when cultured with PHA for 24 h. Residence in the high prevalence village was associated with production of IL-10 (P < 0.006) and GM-CSF (P < 0.04) in response to culture with SEA and IL-5 (P < 0.02) with PHA for 48 h. The interaction between age and village was not significant for these results; however, there was a significant interaction between age and village for IL-5 detected in blood samples cultured with PHA for 24 h (P < 0.01). These results concur with previous observations that major patterns of cytokine production can be related to immunosuppression, but also indicate an underlying pattern which reflects the importance of history of infection to the immune response.

Schistosoma mansoni egg-induced hepatic granulomas in mice deficient for the interferon-gamma receptor have altered populations of macrophages, lymphocytes and connective tissue cells

Systemic production and mobilization of inflammatory cells and formation of hepatic periovular granulomas were studied in Schistosoma mansoni-infected mice with deficient interferon gamma (IFN-gamma) receptor (IFN-gammaR(o/o)). The impaired IFN-gamma signaling did not cause a significant modification of the overall kinetics of inflammatory cells, but mutant mice developed smaller hepatic periovular granulomas with a two-fold reduction in all the cell lineages. In granulomas of normal mice, the fully differentiated macrophages were progressively predominant, whilst in IFN-gammaR(o/o) mice, the granulomas contained a higher percentage of immature and proliferating monocytes. Granulomas of IFN-gammaR(o/o) mice had an enhanced and accelerated fibrotic reaction, corresponding to an increased content of proliferative and activated connective tissue cells. Simultaneously, their granulomas had an increased ratio of T over B cells, with an increase in CD8(+) and a reduction in CD4(+) T cells. The functional IFN-gamma receptor was not required for initial recruitment of monocytes and lymphocytes into granulomas, but it was necessary for the maturation of macrophages, upregulation of major histocompatibility class 2 (MHC-II) expression and consequent stimulation of lymphocyte subpopulations depending upon the MHC-II-mediated antigen presentation.