Schistosome Soluble Egg Antigen Research Articles

Schistosomiasis Seroprevalence among Children Aged 0-14 Years in Nigeria, 2018.

The first nationally representative, population-based study of schistosomiasis seroprevalence in Nigeria was conducted using blood samples and risk-factor data collected during the 2018 Nigeria HIV/AIDS Indicator and Impact Survey (NAIIS). Schistosomiasis seroprevalence was estimated by analyzing samples for reactivity to schistosome soluble egg antigen (SEA) in a multiplex bead assay; NAIIS survey data were assessed to identify potential risk factors for seropositivity. The SEA antibody data were available for 31,459 children aged 0 to 14 years. Overall seroprevalence was 17.2% (95% CI: 16.3-18.1%). Seropositive children were identified in every age group, including children < 5 years, and seroprevalence increased with increasing age (P < 0.0001). Several factors were associated with increased odds of seropositivity, including being a boy (odds ratio [OR] = 1.34, 95% CI: 1.24-1.45), living in a rural area (OR = 2.2, 95% CI: 1.9-2.5), and animal ownership (OR = 1.67, 95% CI: 1.52-1.85). Access to improved sanitation and drinking water sources were associated with decreased odds of seropositivity (OR = 0.52, 95% CI: 0.47-0.58 and OR = 0.53, 95% CI: 0.47-0.60, respectively) regardless of whether the child lived in a rural (sanitation: adjusted odds ratio [aOR] = 0.7, 95% CI: 0.6-0.8; drinking water: aOR = 0.7, 95% CI: 0.6-0.8) or urban area (sanitation: aOR = 0.6, 95% CI: 0.5-0.7; drinking water: aOR = 0.5, 95% CI: 0.4-0.6), highlighting the importance of these factors for schistosomiasis prevention and control. These results identified additional risk populations (children < 5 years) and a new risk factor (animal ownership) and could be used to monitor the impact of control programs.

Deficiency in TLR4 impairs regulatory B cells production induced by Schistosome soluble egg antigen

Regulatory B cells (Bregs) producing IL-10 have negative regulatory function. Several studies have shown the important roles for Toll-like receptor 2 (TLR2), TLR4, and TLR9 ligation in the development of Bregs. We have reported that Schistosome soluble egg antigen (SEA) induced the production of Bregs. However, it remains unclear whether such activation is via the TLR pathway. The present study showed that IL-10 and TLR4 mRNA expression in spleen B cells of significantly increased in C57BL/10 J mice spleen B cells following SEA stimulation. The level of secreted IL-10 and IL-10+ B cell proportion decreased in spleen B cells derived from TLR4-deficient C57BL/10ScNJ (TLR4-/-) mice following SEA or LPS stimulation compared with C57BL/10 J mice. The CD1dhiCD5+ B cells proportion decreased in spleen B cells of TLR4-/- mice following SEA stimulation compared with control mice. NF-κB, ERK, p38MAPK and JNK signal transduction inhibitors significantly suppressed IL-10 secretion in CD1dhiCD5+ B cells induced by SEA or LPS. The phosphorylation levels of IκBα, p65, ERK, JNK and p38 were increased in CD1dhiCD5+ B cell of C57BL/10 J mice treated with LPS or SEA. In conclusion, this study suggests that TLR4 plays a critical role in Bregs activation induced by SEA. And the TLR4-triggered NF-κB and MAPK pathways activation in CD1dhiCD5+ B cells stimulated with SEA. The findings elucidated the mechanism of SEA induction of CD1dhiCD5+ B cells and helped us to understand the immune regulation during Schistosoma japonicum infection.

Schistosoma japonicum infection causes a reprogramming of glycolipid metabolism in the liver

BackgroundRecent investigations indicate that schistosome infection is closely associated with aberrant glycolipid metabolism. However, the actual glycolipid metabolism gene expression, as well as the possible pathways that regulate glycolipid metabolism in the schistosome-infected liver, has not been extensively explored.MethodsIn this study, we evaluated the dynamic expression of glycolipid metabolism-associated genes and proteins in the livers from mice infected with Schistosoma japonicum at the indicated time points using real-time PCR and immunofluorescence. Then, cultures of macrophages were treated with schistosome soluble egg antigen (SEA) to detect the expression levels of genes associated with glucose and lipid metabolism in order to identify macrophages metabolic characteristics in response to these antigens. Furthermore, SEA-stimulated macrophages were co-cultures with hepatocytes and detected the effects of macrophages on the gene expression of hepatocytes metabolism.ResultsThe expression of glycolysis-related genes (Ldha, Glut4, Pkm2, Glut1, Pfkfb3, Aldoc, HK2, Pfk) in the liver were upregulated but the gluconeogenesis gene (G6pc) was downregulated during S. japonicum infection. In addition, the mRNA levels of fatty acid (FA) oxidation-related genes (Ucp2, Atp5b, Pparg) in the liver were significantly upregulated; however, the FA synthesis genes (Fas, Acc, Scd1, Srebp1c) and lipid uptake gene (Cd36) were downregulated post-S. japonicum-infection. In consistence with these data, stimulation with SEA in vitro significantly enhanced the gene expression that involved in glycolysis and FA oxidation, but decreased genes related to gluconeogenesis, FA synthesis and lipid uptake in macrophages. The levels of phosphorylated AMPK, AKT and mTORC1 were increased in macrophages after SEA stimulation. Inhibition of phosphorylated AMPK, AKT and mTORC1 promoted SEA-treated macrophages to produce glucose. In addition, suppression of phosphorylated-AMPK, but not phosphorylated-AKT and phosphorylated-mTOR, induced the lipid accumulation in SEA-stimulated macrophages. Furthermore, SEA-treated macrophages significantly reduced the expression of Acc mRNA in hepatocytes in vitro.ConclusionsThese findings reveal S. japonicum infection induces dynamic changes in the expression levels of genes involved in catabolism (glucose uptake, glycolysis and fatty acid oxidation) and suppressing anabolism (glycogen synthesis) in the liver, which could occur via macrophages’ metabolic states, particularly those involved in the AMPK, AKT and mTORC1 pathways.

Schistosoma mansoni schistosomula antigens induce Th1/Pro-inflammatory cytokine responses.

SummaryLarvae of Schistosoma (schistosomula) are highly susceptible to host immune responses and are attractive prophylactic vaccine targets, although cellular immune responses against schistosomula antigens in endemic human populations are not well characterized. We collected blood and stool from 54 Schistosoma mansoni‐infected Ugandans, isolated peripheral blood mononuclear cells and stimulated them for 24 hours with schistosome adult worm and soluble egg antigens (AWA and SEA), along with schistosomula recombinant proteins rSmKK7, Lymphocyte Antigen 6 isoforms (rSmLy6A and rSmLy6B), tetraspanin isoforms (rSmTSP6 and rSmTSP7). Cytokines, chemokines and growth factors were measured in the culture supernatants using a multiplex luminex assay, and infection intensity was determined before and at 1 year after praziquantel (PZQ) treatment using the Kato‐Katz method. Cellular responses were grouped and the relationship between groups of correlated cellular responses and infection intensity before and after PZQ treatment was investigated. AWA and SEA induced mainly Th2 responses. In contrast, rSmLy6B, rSmTSP6 and rSmTSP7 induced Th1/pro‐inflammatory responses. While recombinant antigens rSmKK7 and rSmLy6A did not induce a Th1/pro‐inflammatory response, they had an association with pre‐treatment infection intensity after adjusting for age and sex. Testing more schistosomula antigens using this approach could provide immune‐epidemiology identifiers necessary for prioritizing next generation schistosomiasis vaccine candidates.

Effect of four rounds of annual school-wide mass praziquantel treatment for schistosoma mansoni control on schistosome-specific immune responses.

SummaryThis study evaluated potential changes in antischistosome immune responses in children from schools that received 4 rounds of annual mass drug administration (MDA) of praziquantel (PZQ). In a repeated cross‐sectional study design, 210 schistosome egg‐positive children were recruited at baseline from schools in western Kenya (baseline group). Another 251 children of the same age range were recruited from the same schools and diagnosed with schistosome infection by microscopy (post‐MDA group). In‐vitro schistosome‐specific cytokines and plasma antibody levels were measured by ELISA and compared between the 2 groups of children. Schistosome soluble egg antigen (SEA) and soluble worm antigen preparation (SWAP) stimulated higher IL‐5 production by egg‐negative children in the post‐MDA group compared to the baseline group. Similarly, anti‐SEA IgE levels were higher in egg‐negative children in the post‐MDA group compared to the baseline group. Anti‐SEA and anti‐SWAP IgG4 levels were lower in egg‐negative children in the post‐MDA group compared to baseline. This resulted in higher anti‐SEA IgE/IgG4 ratios for children in the post‐MDA group compared to baseline. These post‐MDA immunological changes are compatible with the current paradigm that treatment shifts immune responses to higher antischistosome IgE:IgG4 ratios in parallel with a potential increase in resistance to reinfection.

Schistosome Soluble Egg Antigen Decreases Mycobacterium tuberculosis-Specific CD4+ T-Cell Effector Function With Concomitant Arrest of Macrophage Phago-Lysosome Maturation.

Helminth-infected individuals possess a higher risk of developing tuberculosis, but the precise immunologic mechanism of Mycobacterium tuberculosis control remains unclear. We hypothesized that a perturbation of the M. tuberculosis-specific CD4(+) T-cell response weakens the ability of macrophages to contain M. tuberculosis We exposed peripheral blood mononuclear cells from M. tuberculosis-infected humans to schistosome soluble egg antigen (SEA) and then profiled M. tuberculosis-specific CD4(+) T cells via multiparametric flow cytometry. SEA decreased the frequency of cells producing interferon γ (6.79% vs 3.20%; P = .017) and tumor necrosis factor α (6.98% vs 2.96%; P = .012), with a concomitant increase in the median fluorescence intensity of interleukin 4 (IL-4; P < .05) and interleukin 10 (IL-10; 1440 vs 1273; P < .05). Macrophages polarized with SEA-exposed, autologous CD4(+) T-cell supernatant had a 2.19-fold decreased colocalization of lysosomes and M. tuberculosis (P < .05). When polarized with IL-4 or IL-10, macrophages had increased expression of CD206 (P < .0001), 1.5-fold and 1.9 fold increased intracellular numbers of M. tuberculosis per macrophage (P < .0005), and 1.4-fold and 1.7-fold decreased colocalization between M. tuberculosis and lysosomes (P < .001). This clarifies a relationship in which helminth-induced CD4(+) T cells disrupt M. tuberculosis control by macrophages, thereby providing a mechanism for the observation that helminth infection advances the progression of tuberculosis among patients with M. tuberculosis infection.

Screening diagnostic candidates for schistosomiasis from tegument proteins of adult Schistosoma japonicum using an immunoproteomic approach.

BackgroundSchistosomiasis is one of the world’s most prevalent zoonotic diseases and a serious worldwide public health problem. Since the tegument (TG) of Schistosoma japonicum is in direct contact with the host and induces a host immune response against infection, the identification of immune response target molecules in the schistosome TG is crucial for screening diagnostic antigens for this disease.Methodology/Principal FindingsIn this study, an immunoproteomics approach used TG proteins as screening antigens to identify potential diagnostic molecules of S. japonicum. Ten spots corresponding to six proteins were identified that immunoreacted with sera from S. japonicum-infected rabbits but not sera from uninfected rabbits and their specific IgG antibody levels declined quickly after praziquantel treatment. Recombinant phosphoglycerate mutase (PGM) and UV excision repair protein RAD23 homolog B (RAD23) proteins were expressed and their diagnostic potential for schistosomiasis was evaluated and compared with schistosome soluble egg antigen (SEA) using ELISA. The results showed high sensitivity and specificity and low crossreactivity when rSjPGM-ELISA and rSjRAD23-ELISA were used to detect water buffalo schistosomiasis. Moreover, antibodies to rSjPGM and rSjRAD23 might be short-lived since they declined quickly after chemotherapy.Conclusion/SignificanceTherefore, the two schistosome TG proteins SjPGM and SjRAD23 were identified as potential diagnostic markers for the disease. The two recombinant proteins might have the potential to evaluate the effectiveness of drug treatments and for distinguishing between current and past infection.

Schistosoma mansoni soluble egg antigens enhance T cell responses to a newly identified HIV-1 Gag H-2b epitope.

Schistosome infection induces significant T helper type 2 (Th2) and anti-inflammatory immune responses and has been shown to negatively impact vaccine efficacy. Our goal was to determine if the administration of schistosome soluble egg antigens (SEA) would negatively influence the induction of cytotoxic T lymphocyte (CTL) and Th1-type T cell responses to an HIV candidate vaccine in the Th1-biased C57BL/6 mouse strain. Initial experiments failed, as we were unable to detect any response to the defined class I epitope for HIV-1 IIIB Gag. Therefore, we initiated an epitope mapping study to identify C57BL/6 (H-2(b)) T cell epitopes in HIV-1 IIIB Gag in order to perform the experiments. This analysis defined two previously unreported minimal class I H-2(b) and class II I-A(b) epitopes for HIV-1 IIIB Gag. The newly defined HIV-1 IIIB Gag epitopes were used to evaluate the influence of SEA on the generation of CTL and Th1-type HIV-1 IIIB Gag responses. Surprisingly, in contrast to our hypothesis, we observed that the coadministration of SEA with a Listeria monocytogenes vector expressing HIV-1 IIIB Gag (Lm-Gag) led to a significantly increased frequency of gamma interferon (IFN-γ)-producing CD8(+) and CD4(+) T cells in C57BL/6 mice compared to mice immunized with Lm-Gag only. These observations suggest that SEA contains, in addition to Th2-type and immune-suppressive molecules, substances that can act with the Lm-Gag vaccine to increase CTL and Th1-type vaccine-specific immune responses.

Parasitic antigens alter macrophage polarization during Schistosoma japonicum infection in mice

BackgroundSchistosome eggs are trapped in host liver and elicit severe hepatic granulomatous inflammation, which can lead to periportal fibrosis, portal hypertension, hemorrhage, or even death in the host. It was reported that the macrophage plays an important role in host immune responses to schistosome infection. Nitric oxide (NO) produced by classically activated macrophages (M1 macrophages) is cytotoxic to schistosomula and can prevent hepatic schistosomal fibrosis, while arginase-1 (Arg-1) expressed by alternatively activated macrophages (M2 macrophages) promotes hepatic schistosomal fibrosis. However, the dynamics of macrophage polarization, as well as the possible factors that regulate macrophage polarization, during schistosome infection remain unclear.MethodsWe first analyzed M1 and M2-phenotypic markers of peritoneal macrophages from mice infected with Schistosoma japonicum (S. japonicum) at indicated time points using flow cytometry (FCM) analysis and real-time PCR. Then we treated peritoneal macrophages from normal mice with schistosome worm antigen (SWA) or schistosome soluble egg antigen (SEA) and determined M1 and M2-phenotypic markers, in order to identify macrophage polarization in responding to schistosomal antigens.ResultsIn this study, we showed that macrophages were preferentially differentiated into the M1 subtype during the acute stage of S. japonicum infection. However, the level of M1 macrophages decreased and M2 macrophages significantly increased during the chronic stage of infection. Furthermore, we showed that SWA favors the generation of M1 macrophages, whereas SEA preferentially promotes M2-polarized phenotype.ConclusionThese findings not only reveal the parasite antigen-driven dynamic changes in macrophage polarization, but also suggest that manipulation of macrophage polarization may be of therapeutic benefit in controlling excessive hepatic granulomas and fibrosis in the host with schistosomiasis.

Schistosoma japonicum Soluble Egg Antigens Attenuate Invasion in a First Trimester Human Placental Trophoblast Model

BackgroundSchistosomiasis affects nearly 40 million women of reproductive age, and is known to elicit a pro-inflammatory signature in the placenta. We have previously shown that antigens from schistosome eggs can elicit pro-inflammatory cytokine production from trophoblast cells specifically; however, the influence of these antigens on other characteristics of trophoblast function, particularly as it pertains to placentation in early gestation, is unknown. We therefore sought to determine the impact of schistosome antigens on key characteristics of first trimester trophoblast cells, including migration and invasion.MethodsFirst trimester HTR8/SVneo trophoblast cells were co-cultured with plasma from pregnant women with and without schistosomiasis or schistosome soluble egg antigens (SEA) and measured cytokine, cellular migration, and invasion responses.ResultsExposure of HTR8 cells to SEA resulted in a pro-inflammatory, anti-invasive signature, characterized by increased pro-inflammatory cytokines (IL-6, IL-8, MCP-1) and TIMP-1. Additionally, these cells displayed 62% decreased migration and 2.7-fold decreased invasion in vitro after treatment with SEA. These results are supported by increased IL-6 and IL-8 in the culture media of HTR8 cells exposed to plasma from Schistosoma japonica infected pregnant women.ConclusionsSoluble egg antigens found in circulation during schistosome infection increase pro-inflammatory cytokine production and inhibit the mobility and invasive characteristics of the first trimester HTR8/SVneo trophoblast cell line. This is the first study to assess the impact of schistosome soluble egg antigens on the behavior of an extravillous trophoblast model and suggests that schistosomiasis in the pre-pregnancy period may adversely impact placentation and the subsequent health of the mother and newborn.

Association of In Utero Sensitization to Schistosoma haematobium with Enhanced Cord Blood IgE and Increased Frequencies of CD5– B Cells in African Newborns

This study investigated in utero priming as a consequence of maternal parasitic infections. Cord blood plasma samples of 63 African newborns were assessed by enzyme-linked immunosorbent assay for their content of total and schistosome-specific or filaria-specific IgE and IgG4. The frequencies of lymphocyte phenotypes in cord blood were also determined by using flow cytometry, and were compared with those of European newborns. We found significantly increased schistosome soluble egg antigen (SEA)-specific IgE in cord plasma of those born to mothers with schistosome infections and correlations between fetal and maternal SEA-specific and filaria antigen-specific IgE. These data are evidence for in utero priming of the fetal immune system to maternal helminth infections. Furthermore, we show significantly enhanced percentages of CD5- B cells in African newborns cord blood compared with Europeans, which is consistent with earlier maturation of the African fetal immune system.

The C-Type Lectin SIGNR1 BindsSchistosoma mansoniAntigens In Vitro, but SIGNR1-Deficient Mice Have Normal Responses during Schistosome Infection

The de novo immune response to infectious organisms arises from the innate recognition of pathogen-associated molecular patterns (PAMPs) by the host's pattern recognition receptors (PRRs). As the generation of type 2 cytokine responses by the human trematode parasite Schistosoma mansoni is glycan mediated, there is a particular potential role for a C-type lectin receptor (CLR) to mediate the innate recognition of schistosome PAMPs. One such CLR, dendritic cell-specific intracellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN; CD209), has been shown to recognize glycans expressed by S. mansoni eggs. We show that SIGNR1 (SIGN-related 1; CD209b), a murine homologue of DC-SIGN that is expressed on macrophages, also binds both schistosome-soluble egg antigens and worm antigens in vitro. The generation of schistosome egg-induced pulmonary egg granulomas was not altered in SIGNR1-deficient mice. Following S. mansoni infection, the SIGNR1-deficient mice had an unaltered phenotype with an intact immunological response and no difference in pathology. In this study we demonstrate that although SIGNR1 recognizes S. mansoni antigens in vitro, this CLR is redundant during infection. This study highlights the finding that although there was binding of SIGNR1 to immunogenic factors produced in the S. mansoni life cycle, this recognition does not translate to a functional in vivo role for the PRR during infection.

Effect of Chemotherapy with Praziquantel on the Production of Cytokines and Morbidity Associated with Schistosomiasis Mansoni

The objective of the present study was to test the hypothesis that treatment of schistosomiasis mansoni with praziquantel can alter significantly the immune response of patients and generate a reversal of the level of fibrosis. Peripheral blood mononuclear cell (PBMC) samples were collected from, and abdominal ultrasound examinations conducted on, volunteers infected with Schistosoma mansoni and living in an area where the disease is endemic, both prior to and one year after treatment with praziquantel. Subjects were classified into groups according to the level of pathology (i.e., absent, incipient, moderate, or severe fibrosis). PBMCs were stimulated with schistosome soluble egg antigens (SEA), and the levels of production of the cytokines gamma interferon (IFN-gamma), tumor necrosis factor alpha, transforming growth factor beta, and interleukin-4 (IL-4), IL-10, and IL-13 were determined. The chemotherapy was effective in reducing morbidity, particularly for individuals presenting with severe fibrosis. When levels of cytokine production in posttreatment PBMC cultures stimulated by SEA were categorized as low or high, significant differences in the distribution of IL-13 levels between groups presenting with or not presenting with fibrosis were established. Comparison of pre- and posttreatment SEA-induced cytokine levels in individuals who had experienced no change in the grade of fibrosis following chemotherapy revealed that the level of IFN-gamma decreased in subjects with fibrosis whereas that of IL-10 decreased in individuals with and without fibrosis. The data suggest that chemotherapy is effective in reducing the morbidity of the disease and that the level of IL-13 may be a useful indicator of the persistence of fibrosis following treatment.

Schistosoma mansoni soluble egg antigens are internalized by human dendritic cells through multiple C-type lectins and suppress TLR-induced dendritic cell activation

In schistosomiasis, a parasitic disease caused by helminths, the parasite eggs induce a T helper 2 cell (TH2) response in the host. Here, the specific role of human monocyte-derived dendritic cells (DCs) in initiation and polarization of the egg-specific T cell responses was examined. We demonstrate that immature DCs (iDCs) pulsed with schistosome soluble egg antigens (SEA) do not show an increase in expression of co-stimulatory molecules or cytokines, indicating that no conventional maturation was induced. The ability of SEA to affect the Toll-like receptor (TLR) induced maturation of iDCs was examined by copulsing the DCs with SEA and TLR-ligands. SEA suppressed both the maturation of iDCs induced by poly-I:C and LPS, as indicated by a decrease in co-stimulatory molecule expression and production of IL-12, IL-6 and TNF-α. In addition, SEA suppressed TH1 responses induced by the poly-I:C-pulsed DCs, and skewed the LPS-induced mixed response towards a TH2 response. Immature DCs rapidly internalized SEA through the C-type lectins DC-SIGN, MGL and the mannose receptor and the antigens were targeted to MHC class II-positive lysosomal compartments. The internalization of SEA by multiple C-type lectins may be important to regulate the response of the iDCs to TLR-induced signals.

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

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

Molecular Basis of the Differences in Binding Properties of the Highly Related C-type Lectins DC-SIGN and L-SIGN to Lewis X Trisaccharide and Schistosoma mansoni Egg Antigens

The dendritic cell-specific C-type lectin DC-SIGN functions as a pathogen receptor that recognizes Schistosoma mansoni egg antigens through its major glycan epitope Galbeta1,4(Fucalpha1,3)GlcNAc (Lex). Here we report that L-SIGN, a highly related homologue of DC-SIGN found on liver sinusoidal endothelial cells, binds to S. mansoni egg antigens but not to the Lex epitope. L-SIGN does bind the Lewis antigens Lea, Leb, and Ley, similar as DC-SIGN. A specific mutation in the carbohydrate recognition domain of DC-SIGN (V351G) abrogates binding to all Lewis antigens. In L-SIGN Ser363 is present at the corresponding position of Val351 in DC-SIGN. Replacement of this Ser into Val resulted in a "gain of function" L-SIGN mutant that binds to Lex, and shows increased binding to the other Lewis antigens. These data indicate that Val351 is important for the fucose specificity of DC-SIGN. Molecular modeling and docking of the different Lewis antigens in the carbohydrate recognition domains of L-SIGN, DC-SIGN, and their mutant forms, demonstrate that Val351 in DC-SIGN creates a hydrophobic pocket that strongly interacts with the Fucalpha1,3/4-GlcNAc moiety of the Lewis antigens. The equivalent amino acid residue Ser363 in L-SIGN creates a hydrophilic pocket that prevents interaction with Fucalpha1,3-GlcNAc in Lex but supports interactions with the Fucalpha1,4-GlcNAc moiety in Lea and Leb antigens. These data demonstrate for the first time that DC-SIGN and L-SIGN differ in their carbohydrate binding profiles and will contribute to our understanding of the functional roles of these C-type lectin receptors, both in recognition of pathogen and self-glycan antigens.

Chemotherapy for schistosomiasis in Ugandan fishermen: treatment can cause a rapid increase in interleukin-5 levels in plasma but decreased levels of eosinophilia and worm-specific immunoglobulin E.

Chemotherapy for blood-dwelling schistosomes kills the worms and exposes parasite antigen to the circulation. In many people from areas of endemicity, this treatment increases parasite-specific immunoglobulin E (IgE) and other Th2 responses in the months following therapy, responses that have been associated with subsequent resistance to reinfection. Here we investigate much earlier changes in immune reactions after praziquantel therapy in Schistosoma mansoni-infected fishermen working in an area of high transmission in Uganda. The subjects gave blood before treatment and at 1 and 21 days posttreatment. Blood cultures were incubated with schistosome soluble worm antigen (SWA) or soluble egg antigen (SEA). Interleukin-4 (IL-4), IL-5, IL-10, IL-13, gamma interferon, and transforming growth factor beta levels were measured in the cultures and in plasma. A marked transient increase in plasma IL-5 levels was observed in 75% of the subjects (n = 48) by 1 day posttreatment. This response was dependent on pretreatment intensity of infection and was accompanied by a transient decrease in eosinophil numbers. One day posttreatment, blood cultures from the 16 subjects with the greatest increase in plasma IL-5 level (>100 pg/ml) displayed reduced IL-5, IL-13, and IL-10 responses to SWA, and in contrast to the rest of the cohort, these high-IL-5 subjects displayed reduced levels of SWA-specific IgE in plasma 21 days posttreatment. Twenty months after treatment, the intensity of reinfection was positively correlated with the increase in plasma IL-5 level seen 1 day posttreatment. These studies describe the heterogeneity in early immune reactions to treatment, identifying subgroups who have different patterns of reaction and who may have different capacities to mount the responses that have been associated with resistance to reinfection.

Down-regulation of specific antigen-driven cytokine production in a population with endemic Schistosoma japonicum infection.

Schistosome antigen-driven cytokine responses and antischistosome antibody levels of residents of a Schistosoma japonicum endemic island in Poyang Lake, Jiangxi Province were studied before and 45 days after treatment with praziquantel. IL-4, IL-5, IL-10 and INF-gamma were all detected in the supernatants of whole-blood cultures after stimulation with schistosome soluble egg antigen (SEA) and soluble worm antigen preparation (SWAP). The percentages of subjects producing detectable amounts of each cytokine assayed were higher in the group who were negative by stool examination at the start of the study than in those who were initially stool positive. After praziquantel treatment the percentages of subjects producing both type I and type II cytokines increased. This suggests that the production of both types of cytokine was down-regulated in the presence of live, egg-laying S. japonicum adult worms but that this was reversible by treatment. In contrast, the antibody studies showed higher levels of SWAP and SEA-specific antibodies (IgE, total IgG, IgG4, IgM) in subjects who were originally stool-positive than in those who were stool-negative. After treatment specific IgE responses were elevated, but total IgG and IgG4 anti-SEA and IgM anti-SWAP antibody levels all fell significantly.

Antibody isotype responses to Schistosoma japonicum antigens in subjects from a schistosomiasis area with repeated praziquantel chemotherapy compared with a new endemic zone in Hunan Province, P.R. China

To demonstrate the dynamics of specific antibody isotypes against schistosome adult worm (AWA) and soluble egg (SEA) antigens, we evaluated (in 1999–2000) 112 subjects infected with Schistosoma japonicum from 2 regions of Hunan Province, China. Fifty-eight subjects were from Area A, a well-known endemic area with repeated chemotherapy. Area B ( n = 54) is a new endemic focus in another part of the same province. Serum samples were collected prior to praziquantel (PZQ) chemotherapy, and at 2 and 12 months post-treatment. IgM, IgA, IgG, IgG 2, IgG 4 and IgE antibodies to AWA and SEA were measured by quantitative enzyme-linked immunosorbent assay (ELISA). Pre-treatment antibody isotype levels from Area A, except IgA against AWA and SEA, were significantly higher than those from Area B. In response to chemotherapy, most antibody isotype levels fell or remained stable. However, in Area A there was a significant increase in the IgA, IgE and IgG 4 responses to AWA 2 months after PZQ—which fell to approach pre-treatment levels by 12 months. A similar response was seen in Area B with IgE and IgG 4 to AWA. Levels of all AWA-specific IgE and IgG 4 were significantly higher in subjects from Area A compared with Area B at all time-points. AWA-IgE levels demonstrated significant linear correlations with age and number of previous PZQ treatments in Area A only. All SEA-specific isotypes in both areas fell significantly in response to treatment—except IgE, which remained stable in both areas. All SEA-specific isotype levels (except IgA) were significantly higher from Area A at baseline. This significant difference was maintained through 12-months follow-up for IgE, IgG 2 and IgG 4 only. This study suggests that multiple episodes of schistosome infection may be required to generate antibody isotype levels that have been associated with resistance to re-infection in other studies. Further, a surrogate marker of successful chemotherapy (AWA-IgG 4) performed less effectively in patients with previous treatment courses.

Cytokine control of the granulomatous response in Schistosoma mansoni-infected baboons: role of exposure and treatment.

Variations in exposure and treatment may contribute to heterogeneity in immunity and granuloma-induced pathology in human schistosomiasis. To examine this hypothesis, olive baboons were either repeatedly infected with Schistosoma mansoni cercariae or received an equivalent dose in a single infection. They were then cured with praziquantel and reinfected with a single exposure. Serial liver biopsies were obtained throughout the course of the experiment, and cytokine responses by peripheral blood mononuclear cells were measured every 2 to 3 weeks. Reinfection after treatment resulted in a twofold-smaller granuloma size at 6 and 9 weeks after infection compared to the size for the same period after primary infection (P < 0.001) but had no effect at 16 or 19 weeks postinfection. The pattern of exposure did not influence granuloma size. During primary infection schistosome-soluble egg antigen (SEA)-induced cytokine production correlated with granulomatous inflammation. Cytokine levels peaked during the acute infection, declined with chronic infection, and became undetectable after treatment. Reinfection after treatment stimulated a two- to three-fold increase in SEA-specific interleukin-4 (IL-4), IL-5, IL-10, IL-2, and transforming growth factor beta (TGF-beta) production and a marked rise in SEA-specific immunoglobulin E (IgE) and IgG regardless of the type of exposure. Cytokine production was significantly greater in repeatedly exposed animals (P < 0.001). SEA-induced gamma interferon production, however, did not increase with reinfection after treatment. SEA-induced TGF-beta was the only cytokine that remained elevated as the infection become chronic and correlated with diminished hepatic granuloma size, implying its participation in down-modulation. These studies demonstrate that baboons partially retain their ability to down-modulate the granulomatous response after treatment.