Detection of IgG antibody to Toxoplasma gondii with rSAG1 for immunodiagnosis of toxoplasmosis
Objective To establish a rSAG1 ELISA method with purified rSAG1 fusion protein for immunodiagnosis of toxoplasmosis. Methods rSAG1 fusion protein was expressed and purified by Ni 2+ chelating HiTrap HP column. ELISA plate was coated with different concentrations of rSAG1, reacted with pooled positive and negative sera, Goat anti human IgG conjugated to horseradish peroxidase was used as a second antibody. The appropriate detecting condition of rSAG1 ELISA assay was determined by orthogonal experiment, the reproducibility, sensitivity and specificity of the assay were tested. Fifty two IgG positive and 40 IgG negative human sera detected with imported IgG ELISA kit were tested with rSAG1 ELISA. Results The purity of rSAG1 was above 90%; the appropriate detecting condition of rSAG1 ELISA was that the concentration of coated rSAG1 must be 5μg/ml, the human serum should be 1∶100 diluted, and goat anti human IgG conjugated to horseradish peroxidase was in 1∶2000 dilution; the CV value for IgG positive and IgG negative human sera were 10.9% and 10.7% respectively; the inhibition rate of the assay was 62.6%; the total correspondence rate of rSAG1 ELISA was 87% with imported IgG ELISA kit. The positive correspondence rate and negative correspondence rate of rSAG1 ELISA was 81% (42/52) and 95% (38/40) respectively as compared with imported IgG ELISA kit of toxoplasmosis. Conclusion The rSAG1 ELISA has high sensitivity and specificity and good correspondence rate with imported IgG ELISA kit of toxoplasmosis. rSAG1 ELISA has potential value for immunodiagnosis of toxoplasmosis.