New insights into the antigenic structure of the glycoprotein E(rns) of classical swine fever virus by epitope mapping.

The E(rns) glycoprotein of classical swine fever virus (CSFV) has been studied in detail concerning biochemical and functional properties, whereas less is known about its antigenic structure. In order to define epitopes recognized by CSFV-specific antibodies, the binding sites of seven E(rns)-specific monoclonal antibodies were investigated. Mapping experiments using chimeric E(rns) proteins, site-directed mutagenesis and an overlapping peptide library identified one antigenic region located between amino acids (aa) 55 to 110 on the E(rns) protein of CSFV Alfort/187. The domain comprises three linear motifs *(64)TNYTCCKLQ(72), (73)RHEWNKHGW(81), and (88)DPWIQLMNR(96), respectively, and two aa at position 102 and 107 that are crucial for the interaction with antibodies. Additionally, the presentation of the epitope in a correct conformation is mandatory for an efficient antibody binding. These findings allow a better understanding of the organization and the structure of the E(rns) and provide valuable information with regard to the development of E(rns)-based diagnostic tests.