Abstract: 　Objective To identify the potential DNA vaccine candidate which can induce the protective immune response to Toxoplasma gondii by inoculating mice with plasmid DNAs encoding three different forms of P30 antigen (membranous secretory,and intracellular). Methods Three forms of recombinant plasmid: pcDNA3 P30Mb(contain the whole P30 gene sequence,including the gene encoding signal peptide and hydrophobic tail),pcDNA3 P30Se(contain the whole P30 gene sequence, without the gene encoding hydrophobic tail) and pcDNA3 P30In(contain the whole P30 gene sequence,without the gene encoding signal peptide) were constructed by PCR and subcloning technique. The mice were immunized with different forms of recombinant plasmids and IgG antibodies in the mice were detected by ELISA and Western blotting. Results Three forms of expression recombinant plasmid of Toxoplasma gondii P30 gene were successfully constructed. The P30 inserts were identified by restrictive enzyme digestion and sequencing. ELISA and Western blotting analysis demonstrated that specific IgG antibody could be induced in three immunized groups, but there was some difference in appearence time and intensity of IgG.Conclusion Genetically immunization of mice with the recombinant plasmids could elicit specific IgG antibodies. In respect to IgG response, the immune efficiency of the three forms of recombinant plasmids was different at the beginning (2 wk),but 4 wk later approximately same.

Key words: Toxoplasma gondii, P30, DNA vaccine