Immunoglobulin and cytokine changes induced following immunization with a DNA vaccine encoding Toxoplasma gondii selenium-dependent glutathione reductase protein

• High levels of classes IgG, IgA, IgM and subclasses IgG1 and IgG2a after immunization.
• Significant changes in cytokines IFN-γ, IL-4, IL-17 and TGF-β1were induced after TgGR immunization.
• TH1, TH2 and TH17 immune responses are stimulated after TgGR immunization.
• Significant recruitment of CD4+ T lymphocyte subpopulation following the presentation of TgGR.
• Significant long survival rate in pTgGR group.

Toxoplasma gondii Glutathione Reductase (TgGR) plays important role during the survival of the parasite. In this investigation, immunological changes and protection efficiency of this protein delivered as a DNA vaccine (pTgGR) have been evaluated. Mice were immunized with pTgGR, followed by challenge with virulent T. gondii RH strain, 2 weeks after the booster immunization. Compared to the control groups pVAX1, PBS and Blank groups, the results showed that pTgGR stimulated specific humoral response defined by significant titers of total IgG, subclasses IgG1 and IgG2a, classes IgA and IgM, but not IgE. Analysis of IFN-γ, IL-4, IL-17 and TGF-β1 cytokines after immunization and compared with the control groups showed significant increments in pTgGR group. Additionally, T lymphocytes subpopulation CD4+ T was positively recruited with significant percentage detected, while subset CD8+ appeared not to be involved in response to this antigen. Vaccinated mice showed a significantly longer survival time, 15 days, in contrast with control groups which died within 8–10 days after challenge. These results demonstrated that TgGR could induce significant humoral and cell mediated responses leading to a considerable level of resistance against toxoplasmosis infection.

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