Production and evaluation of recombinant granule antigen protein GRA7 for serodiagnosis of Toxoplasma gondii infection in cattle.

The precise detection of Toxoplasma gondii infection in cattle has important public health significance. In the present study, recombinant granule antigen protein GRA7 was evaluated as a potential diagnostic marker for T. gondii infection in cattle by an indirect enzyme-linked immunosorbent assay (ELISA) using the reference serum samples determined by immunofluorescence assay and Western blotting, showing that GRA7-ELISA has a sensitivity of 96.4%, and a specificity of 98.6%. The detection results by GRA7- and Toxoplasma lysate antigen-based ELISAs were compared, indicating that no significant difference (p>0.05) and perfect agreement (κ=0.74) was observed between the two tests. Receiver operating characteristic analysis showed a relative sensitivity and specificity of 100% and 97.3% at the cut-off value of 0.3 for GRA7-ELISA. These data demonstrate that GRA7 is a promising serodiagnostic marker for T. gondii infection in cattle.