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.

Cytokine production associated with periportal fibrosis during chronic schistosomiasis mansoni in humans.

Volunteers living in an area where schistosomiasis mansoni is endemic were subjected to ultrasound examination and classified into groups according to the levels of fibrosis diagnosed, namely, absence of indications of fibrosis (group 0), incipient fibrosis (group 1), and moderate/severe fibrosis (group 2). Peripheral blood mononuclear cells (PBMC) collected from the volunteers were stimulated with soluble antigens from adult schistosomes or from schistosome eggs, and the production of the cytokines gamma interferon, tumor necrosis factor alpha, transforming growth factor beta (TGF-beta), interleukin-4 (IL-4), IL-10, and IL-13 was determined. Potential associations of the level of fibrosis with age, sex, intensity of infection, and cytokine production were investigated between the three groups. Univariate analysis identified associations of age (>50), gender (male), and absence of eggs/g of feces with moderate/severe fibrosis and an association of intensity of infection (>100 eggs) with incipient fibrosis. When cytokine production in PBMC cultures stimulated by soluble egg antigens was categorized as low or high, significant differences in the distribution of IL-13 levels were established between groups 0 and 2. No significant differences were detected between the groups in the cytokines produced by PBMC cultures stimulated with soluble antigens from adult schistosomes. When all variables were tested in multivariate analyses, only IL-13 was strongly associated with fibrosis (odds ratio = 5.8; 95% confidence interval [CI] = 1.1 to 30.5). While high levels of TGF-beta appeared to be associated with protection against fibrosis, the strength of the association was low.

Genetic epidemiology of fecal egg excretion during Schistosoma mansoni infection in an endemic area in Minas Gerais, Brazil.

There is considerable variation in the level of fecal egg excretion during Schistosoma mansoni infections. Within a single endemic area, the distribution of egg counts is typically overdispersed, with the majority of eggs excreted coming from a minority of residents. The purpose of this study was to quantify the influence of genetic factors on patterns of fecal egg excretion in a rural study sample in Brazil. Individual fecal egg excretions, expressed in eggs per gram of feces, were determined by the Kato-Katz method on stool samples collected on three different days. Detailed genealogic information was gathered at the time of sampling, which allowed assignment of 461 individuals to 14 pedigrees containing between 3 and 422 individuals. Using a maximum likelihood variance decomposition approach, we performed quantitative genetic analyses to determine if genetic factors could partially account for the observed pattern of fecal egg excretion. The quantitative genetic analysis indicated that between 21-37% of the variation in S. mansoni egg counts was attributable to additive genetic factors and that shared environment, as assessed by common household, accounted for a further 12-21% of the observed variation. A maximum likelihood heritability (h2) estimate of 0.44 +/- 0.14 (mean +/- SE) was found for the 9,604 second- and higher-degree pairwise relationships in the study sample, which is consistent with the upper limit (37%) of the genetic factor determined in the variance decomposition analysis. These analyses point to the significant influence of additive host genes on the pattern of S. mansoni fecal egg excretion in this endemic area.

Genetic epidemiology of fecal egg excretion during Schistosoma mansoni infection in an endemic area in Minas Gerais, Brazil

There is considerable variation in the level of fecal egg excretion during Schistosoma mansoni infections. Within a single endemic area, the distribution of egg counts is typically overdispersed, with the majority of eggs excreted coming from a minority of residents. The purpose of this study was to quantify the influence of genetic factors on patterns of fecal egg excretion in a rural study sample in Brazil. Individual fecal egg excretions, expressed in eggs per gram of feces, were determined by the Kato-Katz method on stool samples collected on three different days. Detailed genealogic information was gathered at the time of sampling, which allowed assignment of 461 individuals to 14 pedigrees containing between 3 and 422 individuals. Using a maximum likelihood variance decomposition approach, we performed quantitative genetic analyses to determine if genetic factors could partially account for the observed pattern of fecal egg excretion. The quantitative genetic analysis indicated that between 21-37 percent of the variation in S. mansoni egg counts was attributable to additive genetic factors and that shared environment, as assessed by common household, accounted for a further 12-21 percent of the observed variation. A maximum likelihood heritability (h²) estimate of 0.44 ± 0.14 (mean ± SE) was found for the 9,604 second- and higher-degree pairwise relationships in the study sample, which is consistent with the upper limit (37 percent) of the genetic factor determined in the variance decomposition analysis. These analyses point to the significant influence of additive host genes on the pattern of S. mansoni fecal egg excretion in this endemic area

Apoptosis: a mechanism of immunoregulation during human Schistosomiasis mansoni.

People infected with schistosomes may present with a variety of clinical manifestations ranging from the relatively asymptomatic intestinal (INT) form to the hepatointestinal (HI) or hepatosplenic (HS) forms characterized by hepatomegaly and hepatosplenomegaly with severe portal hypertension, respectively. Flow cytometry analyses were used to evaluate the contribution of apoptosis in specific cell populations from schistosomiasis patients to the development of the different clinical forms of the disease. The results showed that cell death induced by combinations of specific antigen and cytokines corresponds with specific clinical presentations. It was shown that soluble egg antigen (SEA) increased the level of apoptosis only in T cells from INT patients. Stimulation with soluble lung worm antigen preparation (SLAP) did not induce significant differences in the levels of apoptosis in T cells from the patients with the different clinical forms of schistosomiasis. These results suggest for the first time that apoptosis plays an important role in the modulation of the anti-SEA response in INT patients.

Familial resemblance in humoral immune response to defined and crude Schistosoma mansoni antigens in an endemic area in Brazil.

This study addressed whether the humoral immune response to crude and defined Schistosoma mansoni antigens aggregates within families. The sample included 155 siblings from 42 nuclear families in Brazil. Sera examined by ELISA for antibody isotypes reactive to defined schistosome antigens and crude schistosome antigens (soluble adult worm antigen preparation and soluble egg antigen) demonstrated that there was a difference in sibling-pair correlations between defined and crude S. mansoni antigens. In contrast to the finding with crude antigens, egg-positive sibling pairs showed significant familial resemblance for all IgG subclasses and IgE to adult-stage antigens Smp20.8 and Smp50. Only the IgE and IgG4 isotypes showed familial resemblance to the egg-stage antigen, Smp40. Egg-negative sibling pairs showed significant familial resemblance only for IgE and IgG4 to Smp40. That both the IgE and IgG4 response to defined S. mansoni antigens showed familial resemblance is interesting in light of the converging evidence for the role of IgE and IgG4 in human susceptibility and resistance to reinfection.

HPLC fractionated soluble egg antigen from Schistosoma mansoni elicits a heterogeneous human immune response.

Peripheral blood mononuclear cells (PBMC) from five chronic schistosomiasis patients, three former patients, a SEA sensitized individual, and normal controls were tested in lymphoblastogenesis assays for their ability to proliferate in response to soluble egg antigen (SEA) and soluble worm antigen preparation (SWAP) from Schistosoma mansoni. Cells from all patients and the SEA sensitized individual gave significantly higher responses than the normal controls when stimulated with SEA and SWAP. However, the chronic patients' SEA responses were much lower than those of the former patients and the SEA sensitized individual. When cells from the same donors were tested in the in vitro granuloma assay, all produced significant granulomatous responses except the normal controls. Once it was established that all individuals in the study gave significant lymphoproliferative responses and granulomatous reactions, SEA was subjected to HPLC fractionation to identify immunogenic protein components of SEA. HPLC separation yielded 25 major fractions. SEA responses from the sensitized individual and former patients exhibited broad, unregulated responsiveness including fractions with neutral, less charged proteins while the chronic patients demonstrated a more restricted range of responsiveness. SEA-HPLC fractions 14, 21, and 22 contain the most immunodominant proteins based on cellular proliferation data from reactive individuals tested.

Evidence that cellular immune responses to soluble and membrane associated antigens are independently regulated during human schistosomiasis mansoni.

We have made a comparative analysis of human cellular and antibody responses to membrane associated adult worm antigens (Mb-A), soluble adult worm antigens (SWAP) and soluble egg antigens (SEA) derived from Schistosoma mansoni. Chronically infected patients with the intestinal (I) and hepatosplenic (HS) forms of the disease as well as non-infected putative immune 'endemic normals' (EN), were studied. We observed that the cellular responses, of individuals, to the two adult worm preparations, SWAP and Mb-A, may be distinct and can be related to the occurrence of resistance or pathology. The resistant group (EN) presented higher levels of both cellular proliferation, and IFN-gamma production, in response to Mb-A as compared with SWAP whereas HS individuals presented higher levels of cellular proliferation to SWAP as compared with Mb-A. Individuals with intestinal disease had similar levels of proliferation to both antigens. The response to SEA by all groups was generally similar, and not predictive of any clinical form. The specific antibody response to the three antigens were in general higher among infected patients than in resistant EN individuals. These results support the hypothesis that the response to adult worm antigens may be pivotal in determining both the development of resistance and severity of disease.

Differential cellular reactivity to adult worm antigens of patients with different clinical forms of schistosomiasis mansoni.

Analysis of the proliferation in vitro of peripheral blood mononuclear cells and the production of interferon-gamma (IFN-gamma) in individuals infected with Schistosoma mansoni and showing different clinical forms of the disease, as well as normal putatively immune individuals from an endemic area, was undertaken using total and fractionated soluble adult worm antigens (SWAP). A higher frequency of detectable response to fractionated antigens in T cell Western blot assays was observed in individuals with the more severe forms of the disease. Analysis of variance showed that, in the Western blot assays, there was a statistically significant difference in the level of cellular proliferation to antigens with low molecular weight (less than 21 kDa) between hepatosplenic patients and those with intestinal and hepatointestinal forms of the disease. No correlation between cellular proliferation and IFN-gamma production was observed. Most of the normal individuals from an endemic area failed to show significant proliferative responses to SWAP T cell Western blot assays or to antigen immobilized on nitrocellulose; they did show significant proliferative responses to whole soluble SWAP with positive IFN-gamma production. The results are consistent with the hypothesis that variations in the cellular immune responses to SWAP influence both the development of pathology and resistance to infection in schistosomiasis mansoni.

Antibodies reactivity in human Schistosoma mansoni disease: detection and functional activity.

The detection and description of the functional activity of anti S. mansoni antibodies, and the relationship between five different antigen preparations, each corresponding to one immunological test for schistosomiasis, are described. This study, using functional assay, suggests that human antibodies detected by skin tests, direct lysis of sheep erythrocytes, complement fixation reaction, indirect immunofluorescent staining and complement-mediated death of schistosomules, show important dissimilarities in reactivities, and it is impossible to ascribe these reactivities to the same class of antibodies.