Immunological changes induced by Toxoplasma gondii Glutathione-S-Transferase (TgGST) delivered as a DNA vaccine

• High levels of classes IgG, IgA, IgM and subclasses IgG1& IgG2a post TgGST vaccination.
• After TgGST vaccination, significant changes in cytokines IFN-γ, IL-4, IL-17, but not TGF-β1, were obtained.
• TH1, TH2 and TH17 immune responses are stimulated after TgGST vaccination.
• Significant recruitment of CD8+ T lymphocyte subset following the presentation of TgGST through MHC-I.
• Partial resistance to acute T. gondii infection.

In this study, a DNA vaccine (pTgGST) encoding T. gondii antioxidant glutathione-S-transferase (TgGST) inserted into eukaryotic expression vector pVAX I was constructed and the immune protective efficacy of intramuscular vaccination of mice with pTgGST was analyzed. Mice immunized with pTgGST elicited high titers of total IgG, IgG1, IgG2a, IgA and IgM antibodies, while IgE showed no changes. Also, significant cytokine production of IFN-γ, IL-4 and IL-17 was detected in mice immunized with pTgGST, but not TGF-β1. CD8+ T cells subsets and MHC-I molecules showed significant increase in contrast to CD4+ subsets. Immunization with pTgGST significantly prolonged survival time (14 days) after challenge infection with the virulent T. gondii RH strain, compared with the control groups which died within 8 days. These results suggested that TgGST DNA vaccine could trigger strong humoral and cellular responses and induce partial protection against acute toxoplasmosis.

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