[Development of the recombinant SAG1 antigen of Toxoplasma gondii by high-density fermentation and identification of its immunoreactivity].

Objective: To develop a technology for production of recombinant SAG1 of Toxoplasma gondii (T.g) in batches.

Methods: The rSAG1 of T.g was expressed in E.coli by high-density fermentation and purified by Sephadex G-75 column chromatography after Ni-NTA agarose at native condition. The activity of rSAG1 and its efficacy in T.g diagnosis were identified by Western blotting and ELISA, respectively.

Results: The optical density (OD) of the bacteria reached 20.21 after induction, and 300 g bacteria were harvested from 11.5 L broth. The rSAG1 was highly expressed in E.coli as a fusion protein, accounting for about 25.82% of the total bacterial protein. The purity of rSAG1 reached 98.54% after purification by Ni-NTA combined with Sephadex G-75 column chromatography. Western blotting revealed a distinct band reacting with the sera of rabbits vaccinated by T.g. Twenty-four of the 25 sera of mice infected with T.g and 36 of the 38 sera of human subjects with IgG antibody against T.g were detected by rSAG1-ELISA.

Conclusion: A large-scale production of immunoreactive SAG1 of T.g is developed by high-density fermentation and purification with Ni-NTA combined with Sephadex G-75 column chromatography.