Immunofluorescence studies of biotype-specific expression of bovine viral diarrhoea virus epitopes in infected cells

The expression of biotype-specific epitopes in cells infected with cytopathic (cp) and non-cytopathic (ncp) bovine viral diarrhoea virus (BVDV) was analysed by immunofluorescence. Four monoclonal antibodies (MAbs) directed against different epitopes on the viral glycoprotein gp48 were used. With cells infected with cpBVDV strain NADL, the four MAbs yielded a strong and granular cytoplasmic fluorescence. The same pattern was observed when cells were infected with ncpBVDV 7443 with two of the MAbs (BVD/C12, BVD/C42). in contrast, reactivity with the other two MAbs (BVD/C38, BVD/C46) was restricted to a narrow perinuclear zone. These biotype-specific differences were not observed either with a gp53-specific MAb, or with an MAb specific for the nonstructural protein pl25/p80. Double immunofluorescence staining of living cells with a polyclonal BVDV-specific serum and with the Mabs revealed that expression of viral proteins on the surface of cells infected with cp- or ncpBVDV, respectively, was not detectable.