Human infections with the filarial parasite Mansonella ozzardi are common in areas of tropical and subtropical Central and South America and often coexist with other endemic tropical diseases, such as malaria. In the Amazonian Basin of Brazil, infections are typically asymptomatic; most of them will remain undiagnosed. These chronic, untreated filarial infections are potentially associated with a regulatory immune environment, dominated by IL-10-producing T-cells, which mediates the suppression of T-cell proliferation in response to filarial and non-related antigens. However, the potential impact of M. ozzardi infections on immune responses to other pathogens, such as Toxoplasma gondii and Plasmodium vivax, remains unknown. Here we aim to investigate whether human M. ozzardi infections induce the expansion of CD4+ T-lymphocyte populations that express molecules with immunoregulatory potential and whether these cell populations are able to inhibit T-cell proliferative responses ex-vivo to unrelated antigens and mitogens. We will also examine plasma levels of several inflammatory and regulatory cytokines and investigate the putative cellular sources of the major immunoregulatory cytokine IL-10 during M. ozzardi infections in naturally exposed subjects living in an endemic area of Amazonas State, Brazil.
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