Toxoplasma gondii is one of the most prevalent intracellular parasites and is threatening the health of both humans and animals,therefore causing incalculable economic losses worldwide.Vaccination is thought to be an efficient ways of controlling toxoplasmosis.T.gondii microneme protein 11 (MIC 11) is a soluble microneme protein which is presumably considered facilitating the early stage of cell invasion.To evaluate the protective efficacy ofT.gondii MIC 11,in the present study,a new DNA vaccine encoding the α:chain ofT.gondii MIC 11 was constructed using the pcDNA3.1 vector.Expression ofMIC11 from this vector was confirmed by indirect immunofluorescence assay following transfection into baby hamster kidney (BHK) cells.Intramuscular immunization of BALB/c mice with pcDNA/MIC 11 was carried out to evaluate the immune responses by serum antibodies titers,lymphoproliferation assay and cytokines assay.The protective efficacy was evaluated by survival rate in mice after challenging with highly virulent strain ofT.gondii.The results demonstrated that this vaccination elicited significant humoral responses and T.gondii lysate antigen (TLA):stimulated lymphoproliferation (p<0.05).Compared to controls,the pcDNA/MIC 11 immunized mice had high production oflFN: Y,IL: 12 and IL:2 (p<0.05),but not IL:4 (p>0.05),indicating that a predominant Thl type response was developed.The vaccination also increased the survival rate of immunized mice when they were challenged with a lethal dose of tachyzoites ofT.gondii RH strain.These data suggest that T.gondii MIC 11 is a reasonable vaccine candidate deserving further studies and pcDNA/MIC11 is a potential strategy for the control oftoxoplasmosis.