Abstract. Detailed knowledge of factors associated with resistance to Schistosoma mansoni infection in endemic areas might facilitate more effective schistosomiasis control. We conducted a cross-sectional study of persons resistant to schistosomiasis and found no association between socioeconomic status and resistance to infection. Mononuclear cells of resistant subjects produced higher levels of interleukin-5 (IL-5), IL-13 and interferon-g upon stimulation with soluble egg antigen (SEA) compared with infected persons. When stimulated with Sm21.6 or Sm22.6, levels of IL-10 were higher in cell culture of resistant persons. Levels of IgE against soluble adult worm antigen (SWAP) and against interleukin-4-inducing principle from S. mansoni eggs (IPSE) and levels of IgG4 against SWAP, SEA, and Sm22.6 were lower in the resistant group compared with the susceptible group. Our data suggest that socioeconomic status could not fully explain resistance to S. mansoni infection observed in the studied area. However, a mixture of Th1 and Th2 immune responses and low levels of specific IgG4 against parasite antigens could be mediating resistance to infection.

Schistosoma mansoni infection is associated with a low prevalence of asthma and a less severe form of the disease. The mechanisms underlying this association may include the production of regulatory cells and cytokines. The aim of this study was to evaluate the immune response induced by the S. mansoni antigens, Sm22.6, PIII, and Sm29 and their ability to suppress allergen-specific IL-5 production by peripheral blood mononuclear cells (PBMC) from asthmatic individuals. PBMCs were stimulated in vitro with S. mansoni antigens in the presence or absence of antigen-1 of the mite Dermatophagoides pteronyssinus (Der p1). Cytokines were measured in PBMC supernatants by enzyme-linked immunosorbent assay (ELISA), and the phenotype of cells producing IL-10 was assessed using flow cytometry. High production of S. mansoni antigen-specific IL-10 was observed not only in cells of S. mansoni-infected individuals, but also in cells of noninfected asthmatic individuals. In the former group, the main cellular sources of IL-10 were CD4 1 CD25 1 , and CD14 1 cells. The levels of IFN-g, IL-5, and IL-13 in the noninfected asthmatic group were $100 pg/ml in response to the antigens. Moreover, when S. mansoni antigens were added to cultures stimulated with Der p1, levels of IL-10 were increased (Der p1 5 2347118; Der p11Sm22.6 5 11897595; Derp11PIII 5 7997331; Derp11Sm29 5 6527288 pg/ ml) with reduced levels of IL-5 (Der p1 5 2867219; Der p11Sm22.6 5 937153; Derp11 PIII 5 1327188; Derp11Sm29 5 96786 pg/ml). The S. mansoni antigens evaluated in the present study induced the production of the regulatory cytokine IL-10 and down-modulated the Th2 immune response that participates in the pathology of asthma. Drug Dev Res 72:538-548, 2011.

This is a prospective, double-blinded, and placebo-controlled trial evaluating the influence of antihelminthic treatments on asthma severity in individuals living in an endemic area of schistosomiasis. Patients from group 1 received placebo of Albendazole or of Praziquantel and from group 2 received Albendazole and Praziquantel. Asthma severity was assessed by clinical scores and by pulmonary function test. There was no significant difference in the asthma scores from D0 to D1–D7 after Albendazole or Praziquantel and from D0 to D30–90 after Albendazole or Praziquantel in both, group 1 and 2. It was observed, however, a clinical worsening of the overall studied population after 6 months and 12 months of antihelminthic treatments. Additionally, we observed increased frequency of forced expiratory volume in 1 second (FEV1) <80% on 12 and 18 months after treatment. The worsening of asthma severity after repeated antihelminthic treatments is consistent with the hypothesis of the protective role conferred by helminths in atopic diseases.

Protective factors associated with atopy or asthma in rural areas include socioeconomic level, overcrowding, and helminth infection. However, little epidemiological information was originated from schistosomiasis areas. This study aimed to investigate factors associated with asthma in a schistosomiasis endemic area. A questionnaire was used to obtain information on demographics, socioeconomic, and environmental features. The ISAAC questionnaire was used to identify individuals with asthma. Parasitological exam was done in all participants and skin prick test to aeroallergens in all asthmatics. Prevalence of Schistosoma mansoni infection was 57.4% and Ascaris lumbricoides, 30.8%. Asthma was found in 13.1% of the population, and 35.1% of them had a positive SPT. Active and passive smoking was positively associated with asthma, whereas A. lumbricoides was negatively associated. In a schistosomiasis hyperendemic region, current infection with A. lumbricoides is protective against asthma. However, we cannot rule out the involvement of S. mansoni infection in this process.