Evaluation of tissue cyst protection in pigs immunized by intradermal and intramuscular routes with a DNA vaccine (rop18 + sag1) against Toxoplasma gondii.

The aim of the present study was to evaluate the protection against tissue cyst formation from T. gondii in pigs immunized with a DNA vector plasmid encoding partial rop18 and sag1 genes. Ten pigs were divided into three groups (G): G1, and G2 received 150μg of pcDNA3.1+rop18, and 150μg of pcDNA3.1+sag1 by intradermal (ID) and intramuscular (IM) routes, respectively. G3 received 300μg of pcDNA 3.1 alone by IM. All groups received 2% (v/v) of levamisole as an adjuvant. Four immunizations were carried out on days 0, 14, 35, and 56; the challenge was performed with ∼ 4x103 oocysts of the ME49 strain by oral route at day 70, and animals were culled on day 100. Humoral immune response of IgM and IgG antibodies was assessed using indirect ELISA, and tissue cysts were evaluable by mouse bioassay. The results showed that the animals immunized with the DNA vaccine (sag1+rop18) developed partial protection against the formation of tissue cysts, however, more studies with higher number of pigs should be conducted.