EXPRESSION OF THE BOVINE VIRAL DIARRHEA VIRUS OSLOSS-P80 PROTEIN - ITS USE AS ELISA ANTIGEN FOR CATTLE SERUM ANTIBODY DETECTION

The putative gene encoding the cytopathic bovine viral diarrhoea virus (BVDV) Osloss strain p80 protein was amplified by PCR and inserted in to a T7 promoter-based vector for expression in Escherichia coli. Bact erial expression led to cytoplasmic insoluble inclusion bodies which w ere denatured by urea treatment and renatured by dialysis. Rabbit anti sera were raised against this p80 recombinant antigen and assayed for the immunoprecipitation of either p120 or p80 protein from cytopathic or non-cytopathic BVDV biotype-infected bovine cells. The p80 gene seq uence was also integrated into a baculovirus genome for its expression in Spodoptera frugiperda insect cells. The recombinant proteins isola ted from bacteria or insect cells showed distinct antigenic properties when analysed by ELISA. Their ability to detect anti-BVDV specific an tibodies was examined in a monoclonal antibody-based competitive ELISA performed on a series of field cattle sera. This comparative assay re vealed the superiority of the insect cell-mediated expression to mimic the natural BVDV antigen produced by cell culture. The baculovirus/in sect cell recombinant antigen gave the highest correlation between the ELISA-detected antibodies and the corresponding virus neutralization data.