Indirect Elisa Using Recombinant Vp1 Capsid Protein for the Serodifferentiation of Foot-and-mouth Disease Virus Infected Animals

Introduction Foot-and-mouth disease (FMD) is a highly contagious viral disease resulting in tremendous economical losses. In order to minimize the risks of an FMD outbreak in disease-free countries due to animal imports, rapid and reliable screening of sera from susceptible animals for the presence of FMD virus (FMDV) antibodies is necessary. The reasons for the development of a novel FMDV antibody ELISA are manifold: (i) increasing the sensitivity compared to the currently used liquid phase blocking ELISA (2), (ii) availability of a simple, inexpensive test for rapid screening which allows diagnosis within one day, (iii) reliable differentiation of serotype-specific antibodies, and (vi) to have a safe test which can be used outside a containment laboratory. The VP1capsid protein gene is a highly variable region of the FMDV genome and is known to contain the two major antigenic sites of the virus (3). By expressing VP1 of various FMDV serotypes and then performing an ELISA using the respective recombinant proteins as antigens, we expect to be able to differentiate antibodies against the different FMDV serotypes. Based on our experiences with recombinant ELISA antigens for the detection of antibodies against classical swine fever virus (4), and PRRS virus (1), we expressed VP1 as a fusion protein in E. coli as well as in a baculovirus expression system.