Immunization with a DNA plasmid encoding the SAG1 (P30) protein of Toxoplasma gondii is immunogenic and protective in rodents

Immunization with DNA can induce humoral and cell-mediated immune responses , both of which are important in conferring immunity to Taxoplasma gondii, The efficacy of genetic vaccination with a cDNA encoding the T. gondii SAG1 (P30) surface antigen was evaluated. Sera of immunized mice showed recogni tion of T. gondii tachyzoites by immunofluorescence and exhibited high tite rs of antibody to SAG1 by ELISA, SAG1-stimulated splenocytes from vaccinate d mice produced primarily interferon-gamma and interleukin-2, Vaccinated mi ce survived challenge with 80 tissue cysts of ME49 strain, whereas all cont rol mice died; challenge with 20 tissue cysts resulted in fewer brain cysts , compared with controls, Challenge of vaccinated rats with VEG strain oocy sts resulted in a reduction in brain cysts. No protection was observed when mice were challenged with the highly virulent RH strain tachyzoites, These results suggest that nucleic acid vaccination can provide protection again st T. gondii infection in mice.