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

This 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.

Immunology of human schistosomiasis

There is a wealth of immunologic studies that have been carried out in experimental and human schistosomiasis that can be classified into three main areas: immunopathogenesis, resistance to reinfection and diagnostics. It is clear that the bulk of, if not all, morbidity due to human schistosomiasis results from immune-response-based inflammation against eggs lodged in the body, either as regulated chronic inflammation or resulting in fibrotic lesions. However, the exact nature of these responses, the antigens to which they are mounted and the mechanisms of the critical regulatory responses are still being sorted out. It is also becoming apparent that protective immunity against schistosomula as they develop into adult worms develops slowly and is hastened by the dying of adult worms, either naturally or when they are killed by praziquantel. However, as with anti-egg responses, the responsible immune mechanisms and inducing antigens are not clearly established, nor are any potential regulatory responses known. Finally, a wide variety of immune markers, both cellular and humoral, can be used to demonstrate exposure to schistosomes, and immunologic measurement of schistosome antigens can be used to detect, and thus diagnose, active infections. All three areas contribute to the public health response to human schistosome infections.

Schistosomiasis vaccine:research to development

In this article, Robert Bergquist and Dan Colley deal with the consolidated, international efforts to generate a schistosomiasis vaccine; in particular, they summarize the deliberations of a series of meetings, held in Cairo, Egypt, 21-25 May 1997, with the aim of reviewing the current status of affairs in this respect in order to make recommendations for the future course of schistosomiasis vaccine development.

Early responses associated with chronic pathology in murine schistosomiasis

Inbred male CBA/J mice infected with Schistosoma mansoni develop either hypersplenomegaly syndrome (HSS) or moderate splenomegaly syndrome (MSS) by 20 weeks of infection. Pathologically and immunologically, MSS and HSS closely parallel the intestinal and hepatosplenic clinical forms of schistosomiasis in humans, respectively. By 6 weeks after infection, mice that eventually will become MSS develop T cell-stimulatory, cross-reactive idiotypes (CRI) while HSS mice never produce CRI. Because presence of CRI is useful to predict degree of chronic pathology, we used this measure to investigate what other early immunological events occurred in animals destined to develop severe morbidity. At 8 weeks of infection, there was a strong inverse correlation between CRI and splenomegaly, egg counts, and liver hydroxyproline. Similarly, phorbol myristate acetate (PMA)- and ionomycin-stimulated intracellular cytokine expression of IL-4, IL-5, and GM-CSF in splenic CD4(+) T cells was inversely correlated with serum CRI and directly correlated with spleen size. In contrast, spleen cell intracellular TNF-alpha and peritoneal cell production of nitric oxide demonstrated positive correlations with CRI and inverse correlations with measures of morbidity. Surprisingly, IL-10 and IFN-gamma were not correlated with CRI levels. These studies link chronic pathology to certain immunological responses during the acute phase of schistosomiasis.

Protective immunity and vaccines to schistosomiasis

Human schistosomiasis is a major health problem in endemic areas and it is estimated that world-wide more than 200 million people are infected. Active infection, exposure to attenuated parasites, or appropriate immunization with parasite extracts or purified antigens can lead to partial protection against challenge infections. Studies of the humoral and cellular mechanisms responsible for these forms of resistance, and the definition, purification or production of recombinant moieties responsible for the induction of immunity are currently the focus of considerable research efforts.

PD-L2+ dendritic cells and PD-1+ CD4+ T cells in schistosomiasis correlate with morbidity

Dendritic cells (DC) are critical antigen-presenting cells for the induction and control of immune responses. PD-L2 (B7-DC) is a regulatory ligand on subpopulations of DC, and binds to the co-regulatory receptor PD-1, present on some activated T lymphocytes, leading to down-regulation. We now show that very early during experimental schistosomiasis (by 5 weeks) a significantly higher proportion of splenic CD11c+/B220- DC express PD-L2, and by 6 weeks after infection a higher proportion of splenic CD4 T cells express PD-1. In this CBA/J mouse/Schistosoma mansoni chronic infection model we have shown that most mice develop moderate morbidity (Moderate Splenomegaly Syndrome, MSS), while some parallel-infected mice express different immune characteristics and die or develop severe morbidity (Hypersplenomegaly Syndrome, HSS). We now report a positive correlation between the proportion of splenic CD11c+/B220- DC that express PD-L2 and showing MSS. In contrast, there is an inverse correlation between the proportion of splenic CD3+/CD4+ T lymphocytes that express PD-1 and showing MSS. The data demonstrate that schistosomes can induce sustained elevated percentages of PD-L2-expressing, B220-negative DC. Furthermore, when this potentially immunoregulatory environment occurs chronically, infected mice are most likely to have developed MSS, expressing moderate morbidity.

Cellular immune responses of schistosomiasis patients are altered by human immunodeficiency virus type 1 coinfection

In vitro studies suggest that CD4(+) cells with a T helper 2 (Th2) phenotype better support human immunodeficiency virus type 1 (HIV-1) replication than do cells of the Th1 phenotype. As a result, Th2-type immune responses may be substantially affected by HIV-1 coinfection. To test this hypothesis, a comparison was done of proliferation and cytokine production by peripheral blood mononuclear cells from patients with schistosomiasis who were positive or negative for HIV-1. Patients with schistosomiasis with HIV-1 coinfections had significantly lower interleukin (IL)-4 and IL-10 production than did HIV-1-negative individuals. In contrast, interferon-gamma production levels were similar between the 2 groups. Furthermore, in patients with HIV-1, a decrease in CD4(+) T cells was correlated with an increased Th1:Th2 cytokine production ratio. The effect of praziquantel treatment on proliferation and cytokine responses also differed between HIV-1 infection groups. Thus, HIV-1 infection affects immune response patterns of patients with schistosomiasis.

Mouse model for Chagas disease: immunohistochemical distribution of different stages of Trypanosoma cruzi in tissues throughout infection

Different stages of Trypanosoma cruzi are seen during mammalian infection. Histologic sections of infected hearts have shown amastigotes and, when using immunohistochemistry (IHC), parasite antigens; however, demonstration of trypomastigotes in these tissues has proven elusive. Using a mouse strain that develops chagasic cardiomyopathy (histologically similar to human infection) 70 days after injecting T. cruzi-Brazil strain, we studied the distribution of parasite stages and the extent of inflammation. All organs had varying amounts of mononuclear inflammation by day 10, which peaked between day 20 and day 30, and decreased by day 50. Amastigotes were detected in myocytes, histiocytes, acinar pancreatic cells, astrocytes and ependymal cells by day 10, and the number of amastigotes peaked on day 30. Immunohistochemistry demonstrated trypomastigotes in sinusoids, vessels and interstitial tissues of several organs between day 15 and 50. Abundant parasite antigens (granular staining) were detected in connective tissues throughout the infection. The burden of amastigotes and trypomastigotes during the acute phase seems to correlate with the degree of inflammation and granular staining in the chronic stage.

Parasitic diseases: opportunities and challenges in the 21st century

The opportunities and challenges for the study and control of parasitic diseases in the 21st century are both exciting and daunting. Based on the contributions from this field over the last part of the 20th century, we should expect new biologic concepts will continue to come from this discipline to enrich the general area of biomedical research. The general nature of such a broad category of infections is difficult to distill, but they often depend on well-orchestrated, complex life cycles and they often involve chronic, relatively well-balanced host/parasite relationships. Such characteristics force biological systems to their limits, and this may be why studies of these diseases have made fundamental contributions to molecular biology, cell biology and immunology. However, if these findings are to continue apace, parasitologists must capitalize on the new findings being generated though genomics, bioinformatics, proteomics, and genetic manipulations of both host and parasite. Furthermore, they must do so based on sound biological insights and the use of hypothesis-driven studies of these complex systems. A major challenge over the next century will be to capitalize on these new findings and translate them into successful, sustainable strategies for control, elimination and eradication of the parasitic diseases that pose major public health threats to the physical and cognitive development and health of so many people worldwide.

The effect of treatment of schistosomiasis on blood plasma HIV-1 RNA concentration in coinfected individuals

OBJECTIVE

To determine whether drug treatment of Schistosomiasis mansoni infection leads to a reduction in plasma HIV-1 RNA concentration in coinfected individuals.

METHODS

Stool and plasma samples were obtained prospectively from a cohort of HIV-infected persons (n = 30) in Kisumu, Kenya, before and after treatment of schistosomiasis with praziquantel (mean follow-up, 5.6 months; range 1-15 months). Schistosomal circulating cathodic antigen (CCA) concentrations in plasma were determined by ELISA and fecal egg counts were determined by microscopy. HIV-1 RNA concentrations were measured in pre- and post-treatment plasma samples obtained from the patients whose stool samples remained free of schistosomal eggs for the great majority of the follow-up period.

RESULTS

Comparison of pretreatment and follow-up samples revealed that mean +/- SD fecal egg burden was reduced by 96.7% (481.5+/-803.5 versus 16.1+/-24.4 eggs/g feces) and mean plasma CCA concentration decreased by 90.1% (3.22+/-3.26 versus 0.32+/-0.38 microg/ml). In contrast, mean plasma HIV-1 load increased from 3.60+/-0.90 to 3.93+/-0.95 log10 RNA copies/ml (P< 0.001). Although no correlation was found between changes in HIV-1 load and changes in schistosomal burden, there was a significant correlation between changes in plasma HIV load and the time interval between pretreatment and follow-up samples (r = 0.41; P = 0.027).

CONCLUSIONS

Treatment of schistosomiasis was not associated with a reduction in plasma HIV-1 load. This study does not, however, exclude the possibility of an adverse effect of helminthic infections on HIV-1 pathogenesis.

T-cell repertoire analysis in acute and chronic human Chagas' disease: differential frequencies of Vbeta5 expressing T cells

Here, we analysed the use of Vbeta-TCR regions by CD4+ and CD8+ T cells from acute and chronic chagasic patients using flow cytometry. We determined the Vbeta expression in cells freshly isolated from patients, as well as after in vitro stimulation with antigens derived from epimastigote (EPI) or trypomastigote (TRYPO) forms of Trypanosoma cruzi. Analysis of Vbeta-TCR expression of T cells freshly isolated from patients showed a decrease in Vbeta5 expression in the CD4+ T-cell population from acutely infected individuals, whereas CD4+Vbeta5+ T cells were found to be increased in chronic patients with the cardiac, but not indeterminate, clinical form. After culturing peripheral blood mononuclear cells (PBMC) from chronic patients with EPI or TRYPO, we found that both antigenic preparations led to a preferential expansion of CD4+Vbeta5+ T cells. EPI stimulation also led to the expansion of CD8+Vbeta5+ T cells, whereas TRYPO led to the expansion of this cell population only if PBMC were from cardiac and not indeterminate patients. We observed that TRYPO stimulation led to an increase in the frequency of CD4+Vbeta17+ T cells in cultures of PBMC from indeterminate patients, whereas an increase in the frequency of CD8+Vbeta17+ T cells was found upon TRYPO stimulation of PBMC from cardiac patients. Despite this increase in the frequency of Vbeta17+ T-cell populations upon TRYPO stimulation, the same antigenic preparation led to a much higher expansion of Vbeta5+ T cells. These results show a differential expression of Vbeta5-TCR in cells freshly isolated from chagasic patients in different stages of the disease and that parasite-specific antigens stimulate a portion of the T-cell repertoire with preferential usage of Vbeta5-TCR.

Susceptibility and resistance to Schistosoma mansoni reinfection: parallel cellular and isotypic immunologic assessment

Cellular and humoral immune responses to Schistosoma mansoni antigen preparations were evaluated in individuals presumed to be susceptible or resistant to reinfection after chemotherapeutic cure. A consistent proliferative increase in the response to soluble egg antigen (SEA) was observed post-treatment in both the susceptible and resistant groups. However, this change was not related to resistance. Isotype studies showed that IgM antibody levels to soluble worm antigen preparation (SWAP) and cercariae antigens were significantly higher in the resistant group than in the susceptible group. Post-treatment, an increase in IgE anti-SWAP and anti-schistosomular tegument (STEG) responses and a decrease in IgG4 anti-SEA and anti-STEG responses were observed in the resistant group. These finding are similar to those we have reported previously for a putative resistant group termed endemic normals, and are compatible with immunologic studies in different endemic areas. Together, these findings indicate that even on the population level, high IgE specificities coupled with low IgG4 specificities correlate well with documented resistance to reinfection.

Self and nonself stimulatory molecules induce preferential expansion of CD5+ B cells or activated T cells of chagasic patients, respectively

It has previously been demonstrated that Trypanosoma cruzi-derived antigens (TRP) and human parasite-specific antibodies (Id) stimulate proliferation of cells from Chagasic patients. More recently, we have shown that activated T cells and CD5+ B cells are present in elevated levels in the peripheral blood of Chagasic patients. Upon in vitro exposure to these two different types of stimulatory molecules (TRP, Id), we now show that each of these elevated populations respond differentially to TRP or Id. We found that stimulation with TRP led to preferential expansion of activated T cells, while Id preferentially stimulated CD5+ B cells and CD8+ T cells. Moreover, this expansion of CD5+ B cells by Id was even more pronounced in cultures of cells from Chagasic patients with the severe, cardiac form of the disease, as compared to indeterminate patients. CD8+ T cells comprise approximately 50% of the total T cells in cultures stimulated by Id while in TRP-stimulated cultures their frequency is proportionally lower. Since parasite antigens and antiparasite antibodies are always present in the host during the chronic phase of the disease, they may also be involved with differential activation mechanisms of these cell populations in vivo.

Molecular characterisation of a NADH ubiquinone oxidoreductase subunit 5 from Schistosoma mansoni and inhibition of mitochondrial respiratory chain function by testosterone

Complementary DNA, encoding the mitochondrial enzyme NADH-ubiquinone oxidoreductase subunit 5 (SmND5) of the human parasite Schistosoma mansoni was isolated by screening a S. mansoni cDNA library with a human androgen receptor (hAR) cDNA probe. The complete nucleotide and deduced aminoacid sequences of SmND5 were determined. Southern blot analysis revealed the occurrence of a single copy gene for SmND5 and by means of RT-PCR, it was shown that sex- and stage-specific expression of SmND5 occurred. In order to establish a functional relationship between the mitochondrial enzyme and the androgen receptor, the effects of testosterone were compared to those of classical respiratory chain inhibitors, using adult schistosome and beef heart submitochondrial particles. Physiological concentrations of testosterone were able to inhibit the maintenance of proton gradient across the mitochondrial membranes, as well as ATP synthesis. The steroid was found to be cytotoxic to the larvae, but not to adult schistosomes. A model is proposed to explain the observed in vivo testosterone-related differences in worm burdens, in experimental chronic infections.

Neonatal exposure to idiotype induces Schistosoma mansoni egg antigen-specific cellular and humoral immune responses

Exposure of neonatal mice to appropriate, cross-reactive Id (CRI) preparations alters immune responsiveness, ameliorates pathology, and prolongs survival of animals upon subsequent Schistosoma mansoni infection. However, because schistosome infections profoundly affect host immunobiology, which responses are effected by neonatal Id exposure alone and which responses are influenced by infection is unclear. To directly examine the schistosome soluble egg Ag (SEA)-specific immune responses altered by CRI exposure, neonatal mice were injected with CRI-expressing (CRI+) SEA-specific Ab preparations, SEA-specific Abs that did not express CRI (CRI-), or normal mouse Ig. At 9 wk of age, only mice that were neonatally exposed to CRI+ anti-SEA Abs displayed significant SEA-specific IgG serum levels and spleen cell proliferative responses. SEA-stimulated spleen cells from these CRI+-exposed mice also produced IFN-gamma, although not at significantly higher levels than mice receiving CRI- Id or normal mouse Ig. If CRI+-exposed mice were also injected with SEA at 8 wk of age, the 9-wk IFN-gamma responses were significantly higher than those of the other neonatal injection groups. The presence of both CRI and anti-CRI in the sera of animals neonatally injected with CRI, but receiving no exposure to S. mansoni Ags or infection, suggested a functional idiotypic network led to these responses. These data demonstrate that appropriate idiotypic exposure induces B and T cell responsiveness to the Ag recognized by the Id and support the hypothesis that neonatal idiotypic exposure can be an important immunoregulatory factor in schistosomiasis.

Clinical forms of human Schistosoma mansoni infection are associated with differential activation of T-cell subsets and costimulatory molecules

The current study has compared the activation status and the expression of the CD28 molecule on circulating CD4+ and CD8+ lymphocytes from patients with different clinical forms of schistosomiasis. The data show that patients with acute schistosomiasis have an increase on the mean percentage of CD4+ HLA-DR+ cells, whereas chronic asymptomatic patients exhibit an increased mean percentage of CD8+ HLA-DR+ cells. Patients with the hepatosplenic disease showed an increase in both CD4+ HLA-DR+ and CD8+ HLA-DR+ cells. Despite the high levels of CD8+ HLA-DR+ cells in hepatosplenic patients, they presented a decreased ratio of CD8+ CD28+/CD8+ cells. These findings of a different percentage of circulating CD8+ CD28+ cells might explain the different in vitro cellular reactivity of asymptomatic and hepatosplenic patients and the defects in the cytokine secretion patterns reported in individuals with hepatosplenic schistosomiasis.

Neonatal idiotypic exposure alters subsequent cytokine, pathology, and survival patterns in experimental Schistosoma mansoni infections

Exposure to maternal idiotypes (Ids) or antigens might predispose a child to develop an immunoregulated, asymptomatic clinical presentation of schistosomiasis. We have used an experimental murine system to address the role of Ids in this immunoregulation. Sera from mice with 8-wk Schistosoma mansoni infection, chronic (20-wk infection) moderate splenomegaly syndrome (MSS), or chronic hypersplenomegaly syndrome (HSS) were passed over an S. mansoni soluble egg antigen (SEA) immunoaffinity column to prepare Ids (8WkId, MSS Id, HSS Id). Newborn mice were injected with 8WkId, MSS Id, HSS Id, or normal mouse immunoglobulin (NoMoIgG) and infected with S. mansoni 8 wk later. Mice exposed to 8WkId or MSS Id as newborns had prolonged survival and decreased morbidity compared with mice that received HSS Id or NoMoIgG. When stimulated with SEA, 8WkId, or MSS Id, spleen cells from mice neonatally injected with 8WkId or MSS Id produced more interferon gamma than spleen cells from mice neonatally injected with HSS Id or NoMoIgG. Furthermore, neonatal exposure to 8WkId or MSS Id, but not NoMoIgG or HSS Id, led to significantly smaller granuloma size and lower hepatic fibrosis levels in infected mice. Together, these results indicate that perinatal exposure to appropriate anti-SEA Ids induces long-term effects on survival, pathology, and immune response patterns in mice subsequently infected with S. mansoni.

Polymerase chain reaction amplification of three different Trypanosoma cruzi DNA sequences from human chagasic cardiac tissue

Chagas' disease is caused by the hemoflagellate protozoan Trypanosoma cruzi. The most common, serious manifestation of Chagas' disease is a progressive inflammatory cardiomyopathy, which occurs decades after primary infection. The inability to consistently demonstrate T. cruzi by histologic techniques in inflammatory cardiac lesions has suggested that the parasites' persistence may not be required for the pathology of the chronic phase. In this report we further analyze the persistence and localization of T. cruzi DNA in the hearts of seven patients with chronic chagasic cardiomyopathy, along with four indeterminate patients and seven control patients seronegative for T. cruzi infection. In the seven patients with chronic chagasic cardiomyopathy, we extracted DNA from selected inflammatory foci-positive (IFP) and inflammatory foci-negative (IFN) areas of' hematoxylin and eosin-stained cardiac tissue. We then used polymerase chain reaction methodology to amplify three different T. cruzi sequences (a minicircle sequence [MCS], a satellite repetitive sequence [RS], and, a low copy number sequence within the gene coding for a flagellar protein [FPS]). The MCS was detected in approximately 100% of both the IFP and IFN areas analyzed. The RS was detected in 37.5% and 23% of the IFP and IFN areas, respectively (difference not statistically significant; P > 0.10, degrees of freedom = 1, G test of independence = 1.9522). The FPS was rarely detected (2%), and was only present in DNA extracted from IFP areas. The MCS was also detected in most indeterminate cases (none of whom had inflammatory lesions) although with a markedly diminished amplification signal relative to cardiomyopathy cases. The MCS was not amplified from the cardiac tissues from seronegative controls. These results suggest that the quantity of T. cruzi DNA persisting in hearts of patients with Chagas' disease correlates with cardiomyopathy, but may not be preferentially associated with inflammatory foci.

Cytokine mRNA levels in the hearts of inbred mice that develop different degrees of cardiomyopathy during infection with Trypanosoma cruzi

Profiles of cytokine mRNA expression were examined by semiquantitative RT-PCR in the hearts of DBA/2 (pathopermissive) and B10.D2 (pathoresistant) mice during infection with the Brazil strain of Trypanosoma cruzi. The levels and time-course profiles of IFNgamma, IL-1beta and IL-10 mRNA expression were similar in each strain. TNFalpha, iNOs, and IL-13 mRNA expression peaked at comparable levels and times after infection in each strain, but declined more rapidly in B10.D2 than in DBA/2 mice. Peak IL-2 mRNA levels were also similar between the two strains, but occurred earlier in DBA/2 than in B10.D2 mice. Levels of IL-4, IL-6 and IL-12 mRNA were significantly higher in DBA/2 than in B10.D2 mice from day 10 through day 50 of infection. With the exception of IL-1beta, which was expressed constitutively in both strains, the levels of mRNA of all other cytokines examined reached their peak no later than day 20 and declined significantly by day 50 after infection. The inflammatory infiltrate paralleled the latter cytokines; starting at day 10 in DBA/2 mice and at day 15 in the B10.D2 s, peaking between days 20 and 30 in both strains, decreasing to minimal levels by day 50 in the pathoresistant mice, but maintaining a mild amount through day 70 in the pathopermissive strain. The inflammation was composed mostly of lymphocytes and histiocytes throughout the entire process. These data demonstrate differences in the profiles of cytokine mRNA that may be related to the differential degree of cardiac pathology that develops in these two strains of mice upon infection with T. cruzi.

Studies on schistosomiasis in western Kenya: II. Efficacy of praziquantel for treatment of schistosomiasis in persons coinfected with human immunodeficiency virus-1

Praziquantel is the drug of choice for schistosomiasis chemotherapy. Although the exact mechanism of how praziquantel kills schistosomes remains poorly understood, the immune response of the host is an important factor in drug efficacy. It is thus possible that disease states of humans that lead to immunodeficiencies, such as infection with human immunodeficiency virus-1 (HIV-1), may render praziquantel less effective in treating schistosomiasis. To test this hypothesis, persons with high levels of Schistosoma mansoni infection who were or were not also infected with HIV-1 were treated with a standard regimen of praziquantel and monitored by quantitative fecal examination and plasma circulating cathodic antigen. Both groups responded to praziquantel therapy equally and individuals with low percentages (< 20%) of CD4+ T cells did not differ from individuals with higher CD4 cell percentages. These data demonstrate that persons with HIV-1 infection can be treated effectively for schistosomiasis with praziquantel.

Analysis of anti-Trypanosoma cruzi antibody isotype specificities by western blot in sera from patients with different forms of Chagas' disease

Infection of humans with Trypanosoma cruzi leads to either a lifelong asymptomatic infection or to symptomatic presentations such as cardiomyopathy, mega-syndromes, or both. The reasons for the different clinical manifestations are not understood. We have previously studied a group of chronically infected individuals with different clinical forms of Chagas' disease and found that the levels of some anti-T. cruzi antibody isotypes, analyzed by enzyme-linked immunosorbent assay, differed among patients with different clinical presentations. We have expanded these studies to examine the antigen specificity of these patients' IgG1, 2, 3, IgM, and IgA by western blot. We observed that binding of particular antigens by some antibody isotypes were more prevalent in some clinical groups as compared to others. For example, IgG3 from 13 of 19 (68%) individuals with digestive manifestations bound a 68-kDa antigen, but only 3 of 31 (9%) individuals with cardiac involvement detected this same moiety. We also found that, regardless of the clinical group, the profiles of antigens recognized by each antibody isotype differs dramatically from the profiles recognized by each other isotype. Together with our previous observations demonstrating that the levels of anti-parasite antibody isotypes correlates with the clinical form, these data suggest that overall anti-T. cruzi antibody reactivities may indeed be skewed toward different antigens in individuals with different clinical presentations.

Cytokine profiles during experimental Chagas' disease

People infected with Trypanosoma cruzi remain so for life, yet only 30-40% of these individuals develop characteristic chagasic cardiomyopathies. Similarly, when infected with the Brazilian strain of T. cruzi, DBA/2 mice develop severe cardiac damage while B10.D2 mice do not. To better understand the immunological parameters that may be involved in the disease process, we have used this murine model (DBA/2 vs B10.D2) and compared the changes in cytokine production during the course of infection with T cruzi. Concanavalin A (Con A) stimulation of spleen cells harvested during the acute phase (day 30) resulted in similarly high levels of IFN-gamma in both mouse strains. However, the amount of IFN-gamma in supernatants from cultures of B10.D2 spleen cells initiated during the chronic phase (day 72) was at subacute levels, whereas secretion by chronic DBA/2 spleen cells remained high. In addition, Con A-stimulated spleen cells from acute DBA/2 mice produced approximately twice as much IL-10 and significantly more IL-4 than cells from B10.D2 mice. IL-4 secretion remained low by cells from chronic B10.D2 mice, but when using cells from chronic DBA/2 mice, levels continued to increase beyond the already high levels secreted by cells harvested during the acute phase. Proliferative responses to Con A stimulation by spleen cells from DBA/2 mice were significantly higher than those from B10.D2 mice in both the acute and chronic phases. These data suggest that enhanced responses in DBA/2 mice, which may be related to a higher parasite burden, a lack of down-regulation, and/or the onset of autoimmune phenomena, correlate with the more severe cardiomyopathy seen in pathopermissive mice.

Cytokine regulation of human immune response to Schistosoma mansoni: analysis of the role of IL-4, IL-5 and IL-10 on peripheral blood mononuclear cell responses

The role of cytokines on the in vitro proliferative response of peripheral blood mononuclear cells (PBMC) from Schistosoma mansoni infected patients to soluble egg (SEA) and adult worm antigens (SWAP) were evaluated. The results obtained demonstrated that the proliferative response of PBMC from chronic intestinal (INT) patients to SEA and SWAP is increased by the blockage of IL-10 with specific monoclonal antibodies (MAb). The effects of these antibodies were readily reversed by the addition of recombinant IL-10. In contrast, no effect was observed on the PBMC response of acute and hepatosplenic patients (HS) in the presence of anti-IL-10. Anti-IL-4 antibodies decreased the PBMC response of the intestinal (INT) and HS individuals to SEA and SWAP, and the PBMC response of acute patients to SEA but not to SWAP. Addition of anti-IL-5 MAb did not decrease the PBMC response of acute patients to SEA or SWAP. These results suggested that IL-10 has an important role in the modulation of the immune response in chronic asymptomatic patients and that this cytokine may be an important factor in controlling morbidity.

Flow cytometric study of blood leucocytes in clinical forms of human schistosomiasis

The aim of this study was to examine three distinct groups of schistosomiasis patients and to determine whether cell phenotype profiles could be correlated with the different clinical forms of the disease. The data obtained indicate that Schistosoma mansoni infected patients have a lower percentage of CD3+ T cells than do non-infected individuals. Interestingly, infected patients presented more than twice the mean percentage of circulating activated T cells (CD3+HLA-DR+) when compared to the control group. Examination of T lymphocyte subpopulations showed that patients with the severe hepatosplenic form (HS) of the disease had lower levels of both CD8High+ and CD8Low+ cells when compared to the other groups of patients. All infected individuals had a higher percentage of circulating B cells, with an increase in the CD5+ B cell population that was more evident in the HS group. The data presented here are evidence to support a relationship between the hepatosplenic form of the disease, a decrease on the CD8+ cell population and an elevation on CD5+ B cells.

IL-10 deficit correlates with chronic, hypersplenomegaly syndrome in male CBA/J mice infected with Schistosoma mansoni

Twenty weeks after moderate level infections with Schistosoma mansoni, approximately 20% of male CBA/J mice develop hypersplenomegaly syndrome (HSS) while the rest present with moderate splenomegaly syndrome (MSS). HSS and MSS mice differ pathophysiologically (degree of splenomegaly, anaemia, ascites, periportal fibrosis, portal hypertension) and immunologically with regard to antibodies (idiotypic expression, isotype levels) to schistosome soluble egg antigens (SEA), and spleen cell phenotypic profiles. This study compared in vitro proliferative responses and IL-2, IFN gamma, IL-4, and IL-10 production by spleen cells from uninfected mice and mice with acute (8 wk), MSS or HSS schistosomiasis mansoni, upon exposure to anti-CD3 epsilon or SEA, Spleen cells from uninfected mice produce Il-2 to anti-CD3 epsilon but exposure of cells from all three groups of infected mice to anti-CD3 epsilon or SEA led to only very low levels of supernatant IL-2. Anti-CD3 epsilon- or SEA-stimulated production of IFN gamma or Il-4, and anti-CD3 epsilon-stimulated production of IL-10, displayed similar patterns: highest cytokine production by cells from mice with acute infections and lower levels of production that did not differ between the two chronic groups. In contrast, while SEA-stimulated IL-10 production was again highest with cells from mice with acute infections, spleen cells from mice with MSS produced significantly more IL-10 than did those from mice with HSS. This association of low levels of antigen-induced IL-10 with severe pathology is consistent with the theory that IL-10 plays a role in the immunoregulation that occurs in chronic schistosomiasis.

Studies on schistosomiasis in western Kenya: I. Evidence for immune-facilitated excretion of schistosome eggs from patients with Schistosoma mansoni and human immunodeficiency virus coinfections

Persons employed as vehicle washers in the town of Kisumu, Kenya are exposed for several hours each day to water in Lake Victoria that contains Schistosoma mansoni-infected Biomphalaria pherifferi snails. This results in a focus of high endemicity for schistosomiasis and these persons have very high concentrations of eggs in their feces (mean +/- SD = 1,469 +/- 1,581 eggs per gram [EPG] of feces). Fecal egg counts, but not circulating cathodic antigen (CCA) levels, in these schistosomiasis patients differed strikingly based on the patient's seropositivity for human immunodeficiency virus (HIV). Patients who were infected with S. mansoni and were seropositive for HIV had similar levels of CCA but excreted fewer eggs (643 +/- 622 EPG; n = 16) than individuals who were not seropositive for HIV infection (1,891 +/- 1,779 EPG; n = 37) (P = 0.009). Egg excretion ratios (EPG/CCA) of the seronegative group were also significantly higher than those of the seropositive group. Those in the seropositive group showed a significant correlative relationship between egg excretion ratios and CD4+ lymphocyte percentages. These observations are compatible with the hypothesis that schistosome eggs exit the human host through the requisite facilitation of functional immune responses, and that the efficacy of this process decreases in schistosomiasis patients co-infected with HIV as their peripheral blood CD4- cell levels decrease.

Immunoregulatory idiotypes stimulate T helper 1 cytokine responses in experimental Schistosoma mansoni infections

Inbred male CBA/J mice with chronic Schistosoma mansoni infections develop two distinct syndromes. Hypersplenomegaly syndrome (HSS) demonstrates pathologic similarities to the hepatosplenic form of chronic human schistosomiasis, and moderate splenomegaly syndrome (MSS) resembles the asymptomatic intestinal form. Immunoaffinity-purified Abs against S. mansoni soluble egg Ags (SEA) from infected patients' sera differ idiotypically according to the donor's clinical form of the disease. We now show that immunoaffinity-purified anti-SEA Abs (Id) from MSS or HSS mice parallel idiotypic preparations of the analogous human clinical form by their differential ability to stimulate the proliferation of anti-Id T cells. MSS Id preparations stimulate spleen cells from either MSS or HSS animals. In contrast, HSS Id does not stimulate spleen cells from either group. In an anti-SEA ELISA, MSS and HSS Id preparations contained comparable levels of IgM and IgG1. However, the MSS Id preparation had higher levels of SEA-specific IgG2a and IgG2b than did HSS Id. The Ig isotypes of these Id preparations suggested differences in cytokine expression patterns. Studies of the cytokine profiles of the spleen cells responding to anti-SEA Id preparations demonstrated that while Id preparations from acutely infected mice stimulate IL-4 and IL-10 production, Id preparations from chronic MSS mice stimulate IFN-gamma production. HSS Id did not stimulate the production of any of these cytokines. The possibility that distinct immunoregulatory environments may contribute to the development of MSS and HSS correlates with earlier hypotheses that hepatosplenic pathology results at least in part from a lack of development or expression of appropriate regulatory Ids.

Immunoregulatory idiotypes stimulate T helper 1 cytokine responses in experimental Schistosoma mansoni infections

Inbred male CBA/J mice with chronic Schistosoma mansoni infections develop two distinct syndromes. Hypersplenomegaly syndrome (HSS) demonstrates pathologic similarities to the hepatosplenic form of chronic human schistosomiasis, and moderate splenomegaly syndrome (MSS) resembles the asymptomatic intestinal form. Immunoaffinity-purified Abs against S. mansoni soluble egg Ags (SEA) from infected patients' sera differ idiotypically according to the donor's clinical form of the disease. We now show that immunoaffinity-purified anti-SEA Abs (Id) from MSS or HSS mice parallel idiotypic preparations of the analogous human clinical form by their differential ability to stimulate the proliferation of anti-Id T cells. MSS Id preparations stimulate spleen cells from either MSS or HSS animals. In contrast, HSS Id does not stimulate spleen cells from either group. In an anti-SEA ELISA, MSS and HSS Id preparations contained comparable levels of IgM and IgG1. However, the MSS Id preparation had higher levels of SEA-specific IgG2a and IgG2b than did HSS Id. The Ig isotypes of these Id preparations suggested differences in cytokine expression patterns. Studies of the cytokine profiles of the spleen cells responding to anti-SEA Id preparations demonstrated that while Id preparations from acutely infected mice stimulate IL-4 and IL-10 production, Id preparations from chronic MSS mice stimulate IFN-gamma production. HSS Id did not stimulate the production of any of these cytokines. The possibility that distinct immunoregulatory environments may contribute to the development of MSS and HSS correlates with earlier hypotheses that hepatosplenic pathology results at least in part from a lack of development or expression of appropriate regulatory Ids.

Schistosoma mansoni: susceptibility differences between male and female mice can be mediated by testosterone during early infection

In murine Schistosoma mansoni infections, fewer adult worms develop in male than in female mice infected with the same number of cercariae. To evaluate a potential role for testosterone in this phenomenon, testosterone levels were manipulated in groups of CBA/J mice that were then infected and monitored for survival rates, worm burdens, organomegaly, and egg production. By 16 weeks of infection, more than 80% of mice in groups with low levels of testosterone (untreated females, castrated males, or carrier-treated castrates) were dead, while less than 40% of those in groups with high levels of testosterone (sham-castrated males, testosterone-treated castrates, or testosterone-treated female mice) succumbed to infection. The mean number of worms recovered from mice in the low testosterone level groups was comparable among groups, and significantly greater than that from those in high-testosterone-level groups. The degree of organomegaly observed correlated strongly with worm burden, but the number of hepatic eggs per female worm did not differ significantly between groups. When male mice were castrated or sham-castrated 5 weeks after S. mansoni infection, no significant differences in host survival occurred. Furthermore, female mice treated with testosterone demonstrated reduced worm burdens if the testosterone was given 10 days prior to infection but not if the testosterone was given 10 days or 5 weeks after infection. Thus, the host sex bias observed in parallel-infected male and female mice appears to be related to the presence of male gonadal tissue or testosterone early in infection, during the development of immature schistosomules.

Influence of parasite presence on the immunologic profile of peripheral blood mononuclear cells from chagasic patients after specific drug therapy

The aim of this study is to evaluate the effects of parasite clearance on the immunological profile of peripheral blood mononuclear cells (PBMC) from chagasic patients submitted to specific drug therapy. PBMC were examined by flow cytometry and proliferative responsiveness to Trypanosoma cruzi-related stimuli. Three groups of patients were studied: not treated (NT), treated not cured (TNC) and cured (C). All data were compared to values from uninfected individuals (NI). NT displayed a lower percentage of CD3+ cells as compared to NI, while TNC and C had mean values that were between those from NI and NT. Infected patients had double the percent of CD3+ HLA-DR+ cells, independent of the efficacy of the treatment. Thus, absence of circulating parasites did not reduce T cell activation in Chagas' disease. NT displayed a higher percentage of CD5+ B cells as compared to NI, while TNC and C had mean values between those from NI and NT. In contrast to the phenotypic data, the in vitro mean proliferative responses to parasite-related stimuli of PBMC from C were reduced to the low mean levels observed in NI. These striking differences were statistically different from the high responses seen in NT and TNC. Our data suggest that proliferative responses of PBMC from C reflect immunological changes due elimination of parasite. However, successful treatment did not alter the levels of peripheral T cell activation.

Schistosoma mansoni: relationship of tumor necrosis factor-alpha to morbidity and collagen deposition in chronic experimental infection

Chronic (20-week) Schistosoma mansoni infections in male CBA/J mice present as one of two pathophysiologic forms: severe hypersplenomegaly syndrome (HSS) or a less severe, moderate splenomegaly syndrome (MSS). HSS mice are cachectic (including anemia and hypertriglyceridemia) and exhibit high levels of periportal and perioval fibrosis. Because tumor necrosis factor-alpha (TNF-alpha) is associated with the symptoms of cachexia, we measured TNF-alpha protein and mRNA levels in the livers of infected and uninfected animals. TNF-alpha levels in liver homogenates from mice with acute infections (8-week) were high (mean +/- SEM; 41.0 +/- 1.6 ng/g tissue) and remained high in livers of HSS mice (41.8 +/- 3.0 ng/g tissue) while TNF-alpha levels in liver homogenates of MSS mice were significantly lower (27.9 +/- 2.0 ng/g tissue). Similarly, hepatic TNF-alpha mRNA levels from HSS mice were two- to threefold higher than those from MSS mice. Hydroxyproline levels in these animals were determined as a measure of collagen deposition and fibrosis and showed increased overall levels in the livers of HSS animals. To investigate the progression of HSS development, hematocrit and serum triglyceride levels were followed over a 20-week period after infection. In mice that developed HSS, hematocrit levels decreased significantly and progressively from Weeks 10 through 20. These same animals showed significant increases in serum triglycerides compared to 8-week-infected mice or the mice which developed MSS over the same time period. These results suggest that failure to downregulate hepatic production of TNF-alpha correlates with, and may contribute to, the development of liver fibrosis and HSS in experimental schistosomiasis.

Immunopathogenesis and immunoregulation in schistosomiasis. Distinct chronic pathologic syndromes in CBA/J mice

Inbred CBA/J mice with chronic (20-week) Schistosoma mansoni infections demonstrate two distinct syndromes. Hypersplenomegaly syndrome (HSS), characterized by a massive spleen, liver fibrosis, ascites, and anemia, resembles hepatosplenic human schistosomiasis, complete with portal hypertension and shunting. Moderate splenomegaly (MSS) syndrome, with less severe pathology, parallels most chronic human infections. Phenotypic analyses of spleen cells for CD44, CD62L, CD45RB, Ia, and CD25 indicate that HSS mice have more activated and memory CD4+ T cells than do MSS mice. HSS animals also have more B cells that highly express B7-2. Anti-CD3 stimulated spleen cells from 8-week or chronically infected mice produce IL-4 and IL-10 in a manner that appears not to involve the CD28/B7-2 costimulation pathway. By contrast IFN-gamma production is augmented in the presence of anti-CD28 and decreased in the presence of anti-B7-2. Infected mice make very little IL-2 to anti-CD3, even with added anti-CD28. As cytokines affect resultant B-cell responses and HSS and MSS mice display distinctive isotypes, differential regulatory or anergy hypotheses may best explain MSS/HSS differences.

Anti-Trypanosoma cruzi antibody isotype profiles in patients with different clinical manifestations of Chagas' disease

Chagas' disease results from infection with the protozoan hemoflagellate Trypanosoma cruzi. Patients in the chronic phase of infection can be categorized into four groups based on the presence of cardiac abnormalities (CARD), gastrointestinal involvement (DIGEST), a combination of both presentations (BOTH), or indeterminate (IND) if Chagas' related pathology is not apparent. Previous studies have indicated that parasite-specific antibody production is important in both resistance to and pathogenesis of disease. The anti-T. cruzi epimastigote stage antibody isotype profiles in the sera of Brazilian patients from each clinical category, as well as from uninfected individuals (UNINF) from the same endemic area were analyzed. Anti-epimastigote immunoglobulin G (IgG)1 and IgG3 levels were strikingly high with titers > or = 1:100,000. Sera from patients in the CARD group had higher levels of IgM than either UNINF or IND individuals, which is consistent with the theory that autoimmunity may contribute to chagasic cardiomyopathy. The IgA levels were higher in sera from patients with gastrointestinal involvement when compared with individuals from any of the other clinical categories as well as from uninfected controls. Interestingly, patients with both digestive and cardiac involvement did not express high serum levels of IgA. However, like patients with cardiac involvement alone, persons with both clinical manifestations produced elevated levels of IgG2 compared with the IND or UNINF groups. These data suggest the presence of complex immunoregulatory processes, most likely related to differential cytokine involvement, which can influence the expression of antibody isotypes and possibly the course of disease.

Antibodies reactive to Trypanosoma cruzi epimastigotes or amastigotes express different idiotypic patterns if from patients with different clinical forms of Chagas' disease

Antibodies (Abs) were purified from pooled sera of patients with either indeterminate (IND or I) or cardiac (CARD or C) Chagas' disease, on either epimastigote (EPI or E) or amastigote-enriched (AMAST or A) antigen (Ag) columns and their idiotypic (Id) expression examined. Anti-Id rabbit Abs were raised to the different preparations (E-IdI, E-IdC, A-IdI and A-IdC). Competitive ELISAs using anti-Ids were able to discriminate between IdI and IdC, disregarding Ag reactivity. E-IdI and A-IdI present different inhibitory abilities, as do E-IdC and A-IdC, but IdC always competes with IdI for anti-IdI comparably. In contrast, a 4-8-fold increase of IdI is required to compete in parallel with IdC for anti-IdC. Therefore, Ids from IND patients share only low levels of the Ids that are most characteristic of CARD patients. While some CARD Abs also express Ids in common with IND patients, these studies reveal that CARD Abs express some Ids that are characteristic to only CARD patients, and these Ids are present on Abs purified with either EPI or AMAST.

Cross-reactive idiotypes on rabbit anti-SEA antibodies stimulate anti-idiotype spleen and lymph node cell responses of mice infected with Schistosoma mansoni

Antibodies to Schistosoma mansoni soluble egg antigens (SEA) generated in outbred rabbits from two different sources were used to study cross-reactive idiotype/anti-idiotype (Id/anti-Id) interactions in S. mansoni-infected mice in two different locations. Immunoaffinity purified rabbit polyclonal anti-SEA antibody preparations (RabId) were predominantly Ig by SDS-PAGE and demonstrated anti-SEA activity by ELISA and Western blot. RabId prepared from three separate rabbits and used at 40 micrograms/ml in vitro stimulated lymphocyte proliferative responses of spleen cells from mice with eight week infections (Mean +/- SEM [E-C]) of 3869 +/- 764, 18594 +/- 3046 and 8962 +/- 1734 cpm. Spleen cells from uninfected mice exposed to the same RabId preparations in vitro had respective [E-C] values of 206 +/- 144, 494 +/- 154 and 363 +/- 180. Lymph node cells from mice infected for 8 weeks demonstrated [E-C] of 123 +/- 400, 5073 +/- 828 and 2361 +/- 656 upon exposure to these 3 RabId preparations. Lymph node cells from uninfected mice had [E-C] of 220 +/- 76, 194 +/- 82 and 143 +/- 72 when exposed to these RabId. Maximum in vitro proliferative response to Ig from unimmunized rabbits was 761 +/- 400 by spleen cells from mice with eight week infections. These data indicate the presence of cross-reactive Id on rabbit anti-SEA antibodies from different rabbits that can stimulate in vitro lymphoproliferative responses of spleen or lymph node cells from S. mansoni-infected mice.

Chagasic patients lack CD28 expression on many of their circulating T lymphocytes

A balanced host-parasite interaction during Trypanosoma cruzi infection allows for the establishment of a chronic infection that can last for many years. T cells are a major element responsible for parasite specific and non-specific immunity during the complex immune response of the host. However, the subpopulations of T cells involved in the response, as well as the exact mechanisms through which those cells are activated or rendered unresponsive, are not well defined. It is known that co-stimulatory signals, some of which are mediated via CD28, are of critical importance in the triggering of appropriate T cell responses. In this study the authors performed double-labelling studies to determine the frequency of expression of CD28 by CD4+ and CD8+ T lymphocytes in the peripheral blood of patients with Chagas' disease. The results show that chagasic patients throughout the spectrum of chronic clinical forms of the infection have significantly higher mean frequencies of CD4+CD28- and CD8+CD28-T cells, as compared with non-chagasic individuals. Considering the importance of CD28 for T-cell activation, the observed down-regulation or loss of CD28 during infection may indicate a possible basis for observed immunoregulatory events or distinct stages of T-cell activation in this infection. Recent evidence from patients with HIV/AIDS indicates that CD28- cell populations are more likely to undergo apoptosis, and increased apoptosis has been observed in experimental Chagas disease.

Early development and progression of lymphocyte-stimulatory cross-reactive idiotypes expressed on antibodies to soluble egg antigens during Schistosoma mansoni infection of mice

Idiotypes (Id) that stimulate immunoregulatory anti-Id T lymphocyte proliferation are expressed on murine and human antibodies (Ab) to soluble egg antigens (SEA) of Schistosoma mansoni. Kinetics of early expression of these stimulatory Id have now been studied using immunoaffinity-purified serum anti-SEA Ab from mice infected with S. mansoni for 6, 7, 8, 12, or 16 weeks. Rabbit anti-Id Ab specific for mouse anti-SEA Id expressed at 8 weeks post-infection (anti-8WkId) demonstrated the strongest interactions with Id present at 7 and 8 weeks post-infection by competitive enzyme-linked immunosorbent assay. Anti-8WkId Ab reacted progressively less well with 12 WkId, 6WkId, and 16WkId. Splenocytes from mice infected for 8 weeks demonstrated the highest blast transformation responses in vitro to anti-SEA Id from mice infected for 6 weeks, while 7, 8, 12, and 16 weeks post-infection Id preparations stimulated progressively less proliferation. These data indicate that although eventual Id-associated immunoregulatory events contribute to chronicity in this disease, production of anti-SEA Ab that express stimulatory cross-reactive immunoregulatory Id comprises a substantial portion of the initial, acute anti-SEA response in mice infected with Schistosoma mansoni. Furthermore, either this particular Id-expressing response is not maintained, or its proportional presence is greatly diminished by the cumulative production of other multiple anti-SEA Ab during the establishment of chronicity, perhaps in response to its immunoregulatory influence very early in infection.

Elevated innate peripheral blood eosinophilia fails to augment irradiated cercarial vaccine-induced resistance to Schistosoma mansoni in IL-5 transgenic mice

Numerous factors contribute to host resistance to infection with Schistosoma mansoni. Although several studies have investigated the eosinophil as an effector cell of protective responses, its true role remains unclear. In vitro, human, but not mouse, eosinophils can kill schistosomula. Studies on schistosome infection susceptibility in naive or vaccinated eosinophil-deficient mice have yielded conflicting results. Using the gamma-irradiated cercariae (irr-cerc) model, we vaccinated interleukin (IL)-5 transgenic mice in parallel with background-matched controls (C3H/HeN) to examine whether innate eosinophilia contributes to increased protection from a challenge infection. In our laboratory, mean peripheral blood eosinophil (PBE) levels in IL-5 transgenic mice were 21,000 mm3, whereas in naive C3H/HeN mice this value was 240 mm3. In 3 separate experiments, both groups of vaccinated mice showed significant resistance to challenge infection. However, there was no significant difference in the percent worm reduction between transgenic IL-5 C3H mice (mean % protection = 44.3; range = 42-45%) and the control C3H/HeN mice (mean % protection = 51.7; range = 41-64%). Our findings indicate that high levels of innate PBE due to constitutive production of IL-5 do not augment irr-cerc-stimulated immunity.

Comparison of antibody isotype responses to Schistosoma mansoni antigens by infected and putative resistant individuals living in an endemic area

The isotypic patterns of antibodies against Schistosoma mansoni antigenic preparations from eggs (SEA), adult worms (SWAP) and cercariae (CERC) have been studied in sera from two groups of individuals living in an area endemic for S. mansoni. One of the groups was comprised of individuals diagnosed as having S. mansoni infections based on their patency, i.e. those passing eggs in their faeces (patent infections, PI). The other group has been consider 'putatively resistant' due to their residence in an endemic area, their documented exposure to positive transmission sites, and their repeated negativity upon stool examinations (endemic normals, EN). There are strong specific responses of IgG1, IgG4 and IgM, particularly to SEA and CERC, by both groups. The reactivities of all isotypes were lower to SWAP. The responses of IgG4, IgM and IgE anti-CERC in EN and PI are higher than those found in normal individuals from outside endemic areas. In general, EN individuals express a relative higher level of anti-STEG IgE as compared to IgG4. On the other hand the pool of sera from PI showed the opposite pattern of higher IgG4 as compared to IgE. Several correlations are seen between isotypic responses to SEA, SWAP and CERC based on comparisons to the anti-SWAP IgE responses of the individuals in the two groups. These comparisons indicate the presence of distinct immunologic differences between individuals in the PI and the EN groups.

Interferon-gamma production by peripheral blood mononuclear cells from residents of an area endemic for Schistosoma mansoni

During human schistosomiasis host responses to antigens of various parasite life-cycle stages may contribute to whether the severe, hepatosplenic state develops or the patient remains relatively asymptomatic throughout infection, and may play a role in resistance. This study evaluated production of interferon gamma (IFN-gamma) in vitro by schistosome antigen-stimulated peripheral blood mononuclear cells (PBMCs) from asymptomatic patients, and by PBMCs from apparently uninfected, untreated persons living in areas endemic for Schistosoma mansoni ('endemic normals'). IFN-gamma production parallels PBMC proliferation in that schistosomal egg antigens stimulate patent patients' cells poorly, but strongly stimulate PBMCs from 'endemic normals'. This is proportionally true for antigens from adult worms and cercariae. Although asymptomatic patent patients' cells produced little or no IFN-gamma in response to the 3 schistosomal antigenic extracts, their PBMCs, and PBMCs from 'endemic normals', produced expected amounts of IFN-gamma when exposed to phytohaemagglutinin. This implies that persons with patent infections have schistosome antigen-specific defects in their ability to respond to IFN-gamma production that are not exhibited by putatively resistant 'endemic normals'.

Activated T and B lymphocytes in peripheral blood of patients with Chagas' disease

Whole blood preparations from patients with either the indeterminate (asymptomatic) or cardiac clinical forms of chronic Trypanosoma cruzi infection were analyzed by flow cytometry using double-labeling to identify subsets of circulating lymphocytes. Several significant differences were demonstrated between the blood lymphocyte profiles of chagasic patients and non-chagasic controls. Clear increase in the percentages and actual numbers of double-positive cells of the phenotype CD3+/HLA-DR+, as well as decrease in the percentage of CD45RA+/CD4+ and CD45RA+/CD8+ T cells, indicate greater numbers of activated T cells circulating in the blood of infected patients. Consistent parallel increases were seen also in the B lymphocyte subset which stained double-positive for CD19/CD5. There were no significant differences in the circulation of these chronic chagasic patients in the CD4:CD8 ratios. Also, no substantive phenotypic differences were observed in the lymphocyte populations between the two ends of the clinical spectrum (indeterminate versus cardiac) in chronic human Chagas' disease. These observations demonstrate that increased levels of activated T cells and CD5+ B cells are present in the circulation of people with chronic Chagas' disease. These are cell phenotypes that have been associated in other conditions with autoimmune, polyclonal, and hyperimmune responses. The specificities of these activated cells and the roles they may play in resistance or pathogenesis during chronic Chagas' disease need now to be determined.

Immunological profiles of patients from endemic areas infected with Schistosoma mansoni

Crude extracts of eggs (SEA) adult worms (SWAP) or cercariae (Cerc) have been used to stimulate Peripheral Blood Mononuclear cells (PBMC) and have provided rather distinct profiles of responses in different types of patients. In general it is clear that patients with early infections respond strongly to SEA while response to SWAP are develop more slowly. As infection progresses into the more chronic phases, a general pattern is seen which leads to lower anti-SEA proliferative responses in the face of higher responses to SWAP and variable anti-cerc responsiveness. Cured not re-exposed patients express very high levels of anti-SEA proliferation. It has recently been seen that those individuals who live in endemic areas and have continued water contact, but are repeatedly stool-negative (who are presumed to have self-cured or be putatively resistant; endemic normals) are strongly responsive to antigenic extracts, particularly to SEA. Furthermore, our results show that endemic normal individuals have significantly higher IFN gamma production upon PBMC stimulation with schistosome antigens than infected individuals. With the emergence of more studies it is becoming apparent that both the intensity and the prevalence of a given area may influence or shape the general responsiveness of the population under study.