[Purification of Toxoplasma gondii Tachyzoites with cellulose membrane filtration and preparation of soluble antigen].

20 ml peritoneal lavage fluid of mice infected with Toxoplasma gondii RH strain was diluted to 250 ml with sterilized physiological saline, and filtered through cellulose membrane filters (pore size: 5 microm). The filtrate was centrifuged at 1512 x g for 15 min, and the sediment was pure T. gondii tachyzoites which were then sonicated. The soluble antigen was prepared by centrifugation at 11200 x g for 30 min. Sera of T. gondii infected SD rat and normal SD rats were collected for immunodetection of soluble antigen. The specificity and valence of soluble antigen were detected with indirect ELISA. The mean removal rates of mouse leukocytes and erythrocytes were 99.9% and 80.3%, respectively, and recovery rate of tachyzoites was 71%. The soluble antigen was extracted from purified T. gondii (1.38 mg per mouse). Indirect ELISA showed that the lowest effective antigen concentration was 5 microg/ml.