Serodiagnosis of Toxoplasma gondii infection in bovines from Kerala, India using a recombinant surface antigen 1 ELISA.

Data on the prevalence of toxoplasmosis in farm animals from India is scanty. Though a few reports exist on prevalence of toxoplasmosis in small ruminants, information on toxoplasmosis in large ruminants is virtually nonexistent from India. An antibody detection recombinant ELISA specific for Toxoplasma gondii was laboratory standardized using recombinant surface antigen 1 (SAG1) protein. A 958-bp truncated sequence coding for tachyzoite stage specific SAG1 protein was amplified and expressed in Escherichia coli BL21(DE3) cells. A high-level expression of the histidine-tagged thioredoxin fusion protein was obtained after 8 h of incubation. The recombinant protein was affinity purified by Ni-NTA agarose chromatography and characterized by SDS-PAGE and Western blot. Subsequently, the diagnostic potential of the recombinant protein was assessed with 258 cattle sera samples from field by a laboratory standardized recSAG1 ELISA. Sera from 71.8% of the cattle showed sero positivity for T. gondii specific IgG. The sensitivity and specificity of the recSAG1 ELISA were 84.38% and 87.88%, respectively in comparison to indirect fluorescent antibody test (IFAT). This is the first report on sensitive serodetection of Toxoplasma infection in bovines from India.