Objective To investigate the humoral immune response induced by a recombinant DNA vaccine based on oncosphere stage-specific antigen. Methods The recombinant plasmid pcDNA3.1/TSO45-4Band the plasmid pcDNA3.1were amplified using alkali pyrolysis.Forty-five female Kunming mice(4-6wks)were randomly divided into 3groups:mice intramuscularly injected with 100μl of normal saline(group A),mice intramuscularly injected with 100μg of the plasmid pcDNA3.1(group B),and mice intramuscularly injected with 100μg of the r...