Fine mapping of a C-terminal linear epitope highly conserved among the major envelope glycoprotein E2 (gp51 to gp54) of different pestiviruses.

Envelope glycoprotein E2 (gp51 to gp54) is the major neutralizing antigen of pestiviruses, which include classical swine fever virus (CSFV), bovine viral diarrhoea virus (BVDV), and border disease virus (BVD). Previous studies carried out using a panel of monoclonal antibodies raised against CSFV strain Brescia have revealed the existence of four antigenic domains, A to D, of the E2 protein, all of which are located at the N-terminal half of the molecule. Here we report the detailed mapping, using three complementary techniques, of a novel linear epitope located at the C-terminal part of the molecule, which reacted with a monoclonal antibody (4-9D4) as well as polyclonal animal sera. This epitope is highly conserved in the three different members of pestiviruses and hence can be used as a genus-specific diagnosis tool. The observation that this epitope is not accessible on the native virus surface, together with its C-terminal location, supports a recently proposed structural model, indicating that the C-terminal part of E2 is membrane-bound while the N-terminal half of the molecule is exposed on the virus surface.