New insights into processing of bovine viral diarrhea virus glycoproteins E(rns) and E1.

Bovine viral diarrhea virus (BVDV) is a member of the genus Pestivirus within the family Flaviviridae. Its single-stranded RNA encodes a polyprotein that is cleaved co- and post-translationally by viral and cellular proteases. However, the cleavage between the envelope proteins E(rns) and E1 is still unexplained. In this study, an E(rns)-E1 protein could be identified and characterized with a new E1-specific antiserum. With bicistronic constructs bearing a deletion in the E(rns)-encoding region and expressing E(rns) or the E(rns)-E1 protein, it could be shown that this protein is not essential for virus replication. Furthermore, two putative cleavage sites were mutated in eukaryotic expression plasmids, as well as in full-length cDNA constructs. The mutation of position P3 of a potential signal peptide peptidase site abolished cleavage completely and no infectious virus progeny could be observed, indicating that cleavage of the E(rns)-E1 protein is indispensable for virus growth.