Maria Ilma Araujo

Polymyxin B as inhibitor of LPS contamination of Schistosoma mansoni recombinant proteins in human cytokine analysis

BackgroundRecombinant proteins expressed in Escherichia coli vectors are generally contaminated with endotoxin. In this study, we evaluated the ability of Polymyxin B to neutralize the effect of LPS present as contaminant on Schistosoma mansoni recombinant proteins produced in E. coli in inducing TNF-α and IL-10. Peripheral blood mononuclear cells from individuals chronically infected with S. mansoni were stimulated in vitro with recombinant Sm22.6, Sm14 and P24 antigens (10 μg/mL) in the presence of Polymyxin B (10 μg/mL).ResultsThe levels of cytokines were measured using ELISA. There was greater than 90 % reduction (p < 0.05) in the levels of TNF-α and IL-10 when Polymyxin B was added to the cultures stimulated with LPS. In cultures stimulated with S. mansoni recombinant proteins in the presence of Polymyxin B, a reduction in the levels of TNF-α and IL-10 was also observed. However, the percentage of reduction was lower when compared to the cultures stimulated with LPS, probably because these proteins are able to induce the production of these cytokines by themselves.ConclusionThis study showed that Polymyxin B was able to neutralize the effect of endotoxin, as contaminant in S. mansoni recombinant antigens produced in E. coli, in inducing TNF-α and IL-10 production.

Inverse Association between Skin Response to Aeroallergens and Schistosoma mansoni Infection

Background: Helminthic infections and allergic disease are highly prevalent in many areas of the world. It is known that IgE antibodies are involved in the pathogenesis of both helminthiasis and atopy. However, the consequences of the presence of helminthic infections in atopic patients are still not completely understood. Methods: Subjects infected by Schistosoma mansoni with more than 200 eggs/g of feces (n = 42) and uninfected subjects (n = 133) were selected from an endemic area of schistosomiasis. The history of allergy and results of the immediate hypersensitivity prick tests with inhalant allergen extracts were registered. Total IgE and IgE specific to S. mansoni and aeroallergens were measured in serum by ELISA. Results: The proportion of individuals with a positive skin test to allergens was higher in the uninfected group (24.3%) than in the group with more than 200 eggs/g of feces (4.8%). The odds of atopy (defined as a positive test for at least one of the antigens) were 5 times higher (odds ratio = 7.0; 95% confidence interval = 1.6–31.1%; p = 0.01) in the uninfected group, after taking into account the potential influence of gender and age. While there was a tendency for higher total and S. mansoni-specific IgE levels in infected patients, an opposite trend, that is higher aeroallergen-specific IgE, was observed in uninfected subjects. Conclusions: There was a strong and statistically significant inverse association between the immediate skin test response to common aeroallergens and infection by S. mansoni. The results indicate that immediate hypersensitivity reactions may be suppressed in S. mansoni-infected individuals.

Immunology of Parasitic Helminth Infections

Parasitic helminths, or worms, comprise a diverse group of metazoan organisms that infect billions of people and their domesticated animals worldwide ([22][1]). In large part, helminthiases are caused by members of the phyla Nematoda and Platyhelminthes ([59][2], [68][3]). Species belonging to both

Association of Type 2 Cytokines with Hepatic Fibrosis in Human Schistosoma mansoni Infection

ABSTRACT The objective of this study was to evaluate the role of cytokines in hepatic fibrosis in the prehepatosplenic and early hepatosplenic stages of schistosomiasis mansoni. Hepatic fibrosis was classified by ultrasonography of 94 patients. Immunological evaluation was performed by the measurement of secreted cytokines (interleukin-5 [IL-5], IL-10, IL-13, gamma interferon, tumor necrosis factor alpha, and transforming growth factor β) in peripheral blood mononuclear cells (PBMC) stimulated by Schistosoma mansoni antigens. Significantly, higher levels of IL-5, IL-10, and IL-13 were found in supernatants of soluble egg antigen-stimulated PBMC from subjects with degree III hepatic fibrosis compared to patients with degree I or II fibrosis. Significant increases in IL-5 and IL-13 levels were also observed in some of the subjects who remained untreated for 1 year following initial assessment and developed more serious fibrosis during this period. The data suggest a role for type 2 cytokines in hepatic fibrosis in human schistosomiasis mansoni.

Schistosoma mansoni Antigens Modulate Experimental Allergic Asthma in a Murine Model: a Major Role for CD4 CD25 Foxp3 T Cells Independent of Interleukin-10

ABSTRACT In areas where schistosomiasis is endemic, a negative correlation is observed between atopy and helminth infection, associated with a low prevalence of asthma. We investigated whether Schistosoma mansoni infection or injection of parasite eggs can modulate airway allergic inflammation in mice, examining the mechanisms of such regulation. We infected BALB/c mice with 30 S. mansoni cercariae or intraperitoneally injected 2,500 schistosome eggs, and experimental asthma was induced by ovalbumin (OVA). The number of eosinophils in bronchoalveolar lavage fluid was higher in the asthmatic group than in asthmatic mice infected with S. mansoni or treated with parasite eggs. Reduced Th2 cytokine production, characterized by lower levels of interleukin-4 (IL-4), IL-5, and immunoglobulin E, was observed in both S. mansoni-treated groups compared to the asthmatic group. There was a reduction in the number of inflammatory cells in lungs of S. mansoni-infected and egg-treated mice, demonstrating that both S. mansoni infection and the egg treatment modulated the lung inflammatory response to OVA. Only allergic animals that were treated with parasite eggs had increased numbers of CD4+ CD25+ Foxp3+ T cells and increased levels of IL-10 and decreased production of CCL2, CCL3, and CCL5 in the lungs compared to the asthmatic group. Neutralization of IL-10 receptor or depletion of CD25+ T cells in vivo confirmed the critical role of CD4+ CD25+ Foxp3+ regulatory T cells in experimental asthma modulation independent of IL-10.

Impaired Th2 development and increased mortality during Schistosoma mansoni infection in the absence of CD40/CD154 interaction.

The role of CD40/CD154 interaction during infection has primarily focused on pathogens that drive inflammatory Th1 responses. In this study, we show that CD40/CD154 interaction is a fundamental requirement for Th2 response development to the parasitic helminth Schistosoma mansoni. Compared with infected wild-type mice, greatly reduced levels of Th2-associated cytokines were measured both in vitro and in vivo, and no IgE or IgG1 was detected in infected CD154−/− mice. In the absence of an overt Th2 response, no exaggerated Th1 response was mounted by CD154−/− mice. Infected CD154−/− mice suffered severe morbidity and mortality, even though parasitemias in wild-type and CD154−/− mice did not differ significantly. These data indicate that CD40/CD154 interaction is required to allow development of a Th2-dominated immune response to S. mansoni and support the view that failure to develop such a response can have fatal consequences.

Mecanismos de resposta imune às infecções

Knowledge acquired about the main immune mechanisms protecting against various infectious agents leads to a better understanding of the pathogenesis of infectious/parasitic diseases and of various strategies specific to the host and parasite. The immune system performs along a cooperation network, which involves the participation of several structural, molecular and cellular components. The fine balance between health and disease is found in this scenario, in which deficiency as much as excess may result in tissue damage. This article explores such aspects and a number of therapies arising from the knowledge acquired.

Interleukin-12 promotes pathologic liver changes and death in mice coinfected with Schistosoma mansoni and Toxoplasma gondii.

ABSTRACT We previously demonstrated that mice concurrently infected withSchistosoma mansoni and Toxoplasma gondiiundergo accelerated mortality which is preceded by severe liver damage. Abnormally high levels of serum tumor necrosis factor alpha (TNF-α) in the dually infected mice suggested a role for this and related proinflammatory mediators in the pathologic alterations. In order to evaluate the factors involved in increased inflammatory-mediator production and mortality, interleukin-12−/−(IL-12−/−) mice were coinfected with S. mansoni and T. gondii, and survival and immune responses were monitored. These IL-12−/− mice displayed decreased liver damage and prolonged time to death relative to wild-type animals also coinfected with these parasites. Relative to the response of cells from the coinfected wild-type animals, levels of TNF-α, gamma interferon, and NO produced by splenocytes from coinfected IL-12−/− mice were reduced, and levels of IL-5 and IL-10 were increased, with the net result that the immune response of the dually infected IL-12−/− mice was similar to that of the wild-type mice infected with S. mansoni alone. While dually infected wild-type animals succumb in the absence of overt parasitemia, the delayed death in the absence of IL-12 is associated with relatively uncontrolled T. gondii replication. These data support the view that S. mansoni-infected mice are acutely sensitive to infection with T. gondii as a result of their increased hepatic sensitivity to high levels of proinflammatory cytokines; IL-12 and TNF-α are implicated in this process.

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

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

Gene Encoding Duffy Antigen/Receptor for Chemokines Is Associated with Asthma and IgE in Three Populations

RATIONALE Asthma prevalence and severity are high among underserved minorities, including those of African descent. The Duffy antigen/receptor for chemokines is the receptor for Plasmodium vivax on erythrocytes and functions as a chemokine-clearing receptor. Unlike European populations, decreased expression of the receptor on erythrocytes is common among populations of African descent, and results from a functional T-46C polymorphism (rs2814778) in the promoter. This variant provides an evolutionary advantage in malaria-endemic regions, because Duffy antigen/receptor for chemokines-negative erythrocytes are more resistant to infection by P. vivax. OBJECTIVES To determine the role of the rs2814778 polymorphism in asthma and atopy as measured by total serum IgE levels among four populations of African descent (African Caribbean, African American, Brazilian, and Colombian) and a European American population. METHODS Family-based association tests were performed in each of the five populations to test for association between the rs2814778 polymorphism and asthma or total IgE concentration. MEASUREMENTS AND MAIN RESULTS Asthma was significantly associated with the rs2814778 polymorphism in the African Caribbean, Colombian, and Brazilian families (P < 0.05). High total IgE levels were associated with this variant in African Caribbean and Colombian families (P < 0.05). The variant allele was not polymorphic among European Americans. CONCLUSIONS Susceptibility to asthma and atopy among certain populations of African descent is influenced by a functional polymorphism in the gene encoding Duffy antigen/receptor for chemokines. This genetic variant, which confers resistance to malarial parasitic infection, may also partially explain ethnic differences in morbidity of asthma.