Indirect ELISA for serosurveillance of Japanese encephalitis in pigs

For monitoring the activity of Japanese encephalitis (JE) in pigs, no effective assay is available in Indian context. Being its endemicity in India and role of pigs as amplifiers, there was need to develop rapid and sensitive assay for serosurveillance of JE in pigs. An Indirect ELISA (I-ELISA) was standardized using ultracentrifuge sucrose density gradient purified JE antigen from standard virus strain. Cross reaction studies were done with West Nile antigen and comparative efficacy of IELISA assessed with Virus Neutralization Test (VNT). Optimum results recorded for detection of IgG and IgM, respectively, at 50 ng/well antigen and 1:200 and 1:300 serum dilutions. The positive - to - negative ratio of ≥2 considered positive for JE antibodies. The overall prevalence of JE in pigs recorded to be 28.89%. The concordance of the indirect ELISA (IgG) visa- vis VNT revealed good agreement (kappa = 0.66) and moderate agreement (kappa = 0.56) of standardized I- ELISA towards detection of IgG and IgM, respectively. The assay standardized in the present study could be useful for JE serosurveillance in pig population from endemic and non endemic areas in India.