pVAX1-HSP40-based immunization protected against chronic infection. Number of brain cysts in mice challenged orally with 10 Pru cysts two weeks post the final immunization. The brain cysts in the pVAX1-HSP40-immunized mice were significantly lower compared with those in the control mouse groups (**p < 0.01). No significant difference was detected between the control mouse groups (p > 0.05).