APPLICATION OF RECOMBINANT BOVINE VIRAL DIARRHEA VIRUS PROTEINS IN THE DIAGNOSIS OF BOVINE VIRAL DIARRHEA INFECTION IN CATTLE

The National Animal Disease Laboratory (NADL) vaccine strain of bovine viral diarrhea virus (BVDV) genes for gp48 and p80 were expressed in Escherichia coli. The BVDV-NADL gene for gp62 was integrated into a ba culovirus genome for expression in Spodoptera frugiperda (Sf-9) insect ovarian cells. The antigenicity of baculovirus expressed BVDV protein was detected by anti-BVDV specific antibodies in an enzyme-linked imm unosorbent assay (ELISA), indirect immunofluorescent assay (LFA) and r adio-immunoprecipitation (RIP). The recombinant proteins isolated from bacteria showed antigenic properties when analyzed by ELISA and immun oblotting using BVDV antibodies. The recombinant proteins were then us ed in ELISA or IFA to detect BVDV infection by testing 54 independent bovine serum samples. The baculovirus-expressed BVDV protein was used as an ELISA and IFA antigen, and the bacteria-expressed proteins were used as ELISA antigens. BVDV-NADL-infected Madin-Darby bovine kidney ( MDBK) cell monolayers served as a control antigen. Statistical analysi s showed a high degree of correlation between the reactivity of recomb inants and natural antigens in ELISA using bovine sera. The results of ELISA or IFA proved there is a high degree of correlation with the vi rus neutralization. In the comparative ELISA assays, the insect-cell-m ediated expression revealed greater specificity and sensitivity than t he bacterial expression or the natural BVDV antigens produced by cell cultures. (C) 1997 Elsevier Science B.V.