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    Immunological Interactions between 2 Common Pathogens, Th1-Inducing Protozoan Toxoplasma gondii and the Th2-Inducing Helminth Fasciola hepatica


    Miller, Catherine M. D. and Smith, Nicholas C. and Ikin, Rowan J. and Boulter, Nicola R. and Dalton, John P. and Donnelly, Sheila (2009) Immunological Interactions between 2 Common Pathogens, Th1-Inducing Protozoan Toxoplasma gondii and the Th2-Inducing Helminth Fasciola hepatica. PLoS ONE, 4 (5 e5692). pp. 1-10. ISSN 1932-6203

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    Abstract

    Background: The nature of the immune response to infection is dependent on the type of infecting organism. Intracellular organisms such as Toxoplasma gondii stimulate a Th1-driven response associated with production of IL-12, IFN-c, nitric oxide and IgG2a antibodies and classical activation of macrophages. In contrast, extracellular helminths such as Fasciola hepatica induce Th2 responses characterised by the production of IL-4, IL-5, IL-10 and IgG1 antibodies and alternative activation of macrophages. As co-infections with these types of parasites commonly exist in the field it is relevant to examine howthe various facets of the immune responses induced by each may influence or counter-regulate that of the other. Principal Findings: Regardless, of whether F. hepatica infection preceded or succeeded T. gondii infection, there was little impact on the production of the Th1 cytokines IL-12, IFN-c or on the development of classically-activated macrophages induced by T. gondii. By contrast, the production of helminth-specific Th2 cytokines, such as IL-4 and IL-5, was suppressed by infection with T. gondii. Additionally, the recruitment and alternative activation of macrophages by F. hepatica was blocked or reversed by subsequent infection with T. gondii. The clinical symptoms of toxoplasmosis and the survival rate of infected mice were not significantly altered by the helminth. Conclusions: Despite previous studies showing that F. hepatica suppressed the classical activation of macrophages and the Th1-driven responses of mice to bystander microbial infection, as well as reduced their ability to reject these, here we found that the potent immune responses to T. gondii were capable of suppressing the responses to helminth infection. Clearly, the outcome of particular infections in polyparasitoses depends on the means and potency by which each pathogen controls the immune response.

    Item Type: Article
    Additional Information: This work was supported by an Institute for the Biotechnology of Infectious Diseases Fellowship awarded to CMM. SD and JPD were supported by the National Health and Medical Research Council of Australia Project. This work was supported by an Institute for the Biotechnology of Infectious Diseases Fellowship awarded to CMM. SD and JPD were supported by the National Health and Medical Research Council of Australia Project Grant 352912. JPD is a recipient of a NSW Government 2003 BioFirst award. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
    Keywords: Immunological Interactions; Common Pathogens; Th1-Inducing Protozoan Toxoplasma gondii; Th2-Inducing Helminth Fasciola hepatica;
    Academic Unit: Faculty of Science and Engineering > Biology
    Faculty of Science and Engineering > Research Institutes > Institute of Immunology
    Item ID: 2229
    Identification Number: e5692
    Depositing User: Users 308 not found.
    Date Deposited: 03 Nov 2010 12:31
    Journal or Publication Title: PLoS ONE
    Publisher: Public Library of Science
    Refereed: Yes
    URI:

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