Induction of protective immunity against toxoplasmosis in mice by DNA immunization with a plasmid encoding Toxoplasma gondii GRA4 gene.

摘要

GRA4 is a dense granule protein of Toxoplasma gondii that is a candidate for vaccination against this parasite. We have inserted the entire coding sequence of GRA4 into a eukaryotic expression vector to determine whether DNA immunization can elicitprotective immune response to T. gondii. Susceptible C57BL/6 mice were then vaccinated intramuscularly with GRA4 DNA and orally challenged with a lethal dose of 76 K T. gondii strain cysts. Immunization with pGRA4 resulted in a 62% survival of C57BL/6 infected mice. Mice immunized with GRA4 DNA developed high levels of serum anti-GRA4 immunoglobulin G antibodies as well as a cellular immune response, as assessed by splenocyte proliferation, in response to recombinant GRA4 protein restimulation in vitro.The cellular immune response was associated with IFN-gamma and IL-10 synthesis, suggesting a modulated Th1-type response. Splenocyte proliferation was strongly enhanced and protection slightly higher by inoculation with GRA4 DNA combined with a granulocyte-macrophage colony-stimulating factor expressing vector. This is the first report that demonstrates the establishment of a DNA vaccine-induced protective immunity against the acute phase of T. gondii infection.