A DIAGNOSTIC IMMUNOASSAY FOR NEWCASTLE-DISEASE VIRUS-BASED ON THE NUCLEOCAPSID PROTEIN EXPRESSED BY A RECOMBINANT BACULOVIRUS

A recombinant baculovirus containing a cDNA clone encoding the nucleoc apsid (NP) protein of Newcastle disease virus (strain Ulster 2C) has b een used to infect insect cells (Spodoptera frugiperda). High levels o f overexpressed NP protein were observed, comprising up to 40% of tota l cellular protein, which were subsequently shown to be antigenic. Nuc leoprotein derived from the crude soluble lysate of infected insect ce lls has been used in an indirect ELISA to detect the presence of anti- NDV antibodies in a cohort of chicken sera. Data produced from these t ests indicated a good correlation between ELISA titre and haemagglutin ation inhibition test data. The test was not affected by interference from background cellular proteins nor by cross-reactivity with non-NDV poultry pathogens. Additionally, the test did not generate false-posi tive readings.