Standardization of an ELISA using Recombinant Nucleocapsid Protein to quantify antibody response against Newcastle Disease Virus in Chickens

The coding sequence of NP gene was amplified by RTPCR, cloned and expressed in prokaryotic expression system-E. coli. The crude extract of expressed protein was purified, extensively dialyzed and further purified by expanded bed adsorption chromatography. Three indirect ELISA using recombinant NP were standardized and the antibody titres against NDV in serum samples were found to correlate among these three ELISAs. The correlation coefficient values were 0.3 to 0.6 which were higher than table values for correlation coefficient at 1% level. The empirical ROC values were observed to be 0.929, 1.0 and 1.0 for comparisons between RP-ELISA versusHI, RP-ELISA versus WVP-ELISA and R P-ELISA versus PEPELISA respectively which are more than the standard value of 0.8.