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Title: Mapping of Antigenic Sites on a SAT2 Foot-and-Mouth Disease Virus Vaccine Strain

Author
item OPPERMAN, P - ONDERSTEPOORT VET INST SA
item MAREE, FRANCOIS - ONDERSTEPOORT VET INST SA
item BLIGNAUT, B - ONDERSTEPOORT VET INST SA
item VOSLOO, WILNA - ONDERSTEPOORT VET INST SA
item Rieder, Aida - Elizabeth
item THERON, J - UNIV PRETORIA, SA

Submitted to: European Study Group on the Molecular Biology of Picornaviruses
Publication Type: Abstract Only
Publication Acceptance Date: 3/3/2008
Publication Date: 5/26/2008
Citation: Opperman, P.A., Maree, F.F., Blignaut, B., Vosloo, W., Rieder, A.E., Theron, J.J. 2008. Mapping of Antigenic Sites on a SAT2 Foot-and-Mouth Disease Virus Vaccine Strain. European Study Group on the Molecular Biology of Picornaviruses. P 204

Interpretive Summary:

Technical Abstract: Foot-and-mouth disease virus (FMDV) exist as seven serologically distinct serotypes based on the absence of cross-protection following infection. Even within a serotype, distinct genetic and antigenic variants are present, a likely consequence of the high mutation rate of the virus, giving rise to the concept of a quasispecies population. The variation is geographically linked and the practical implication is that an animal vaccinated against one topotype may be susceptible to infection by viruses from other topotypes within the same serotypes. We proposed to determine the antigenic sites on the capsid of a SAT2 FMDV vaccine strain using a dual approach, i.e. (a) by selecting antibody single chain variable fragments (scFv) that show affinity to the SAT2 virion and (b) using bioinformatics by determining the relationships between FMD virus genotypes and antigenic phenotypes. The advantage of scFv’s is, they can be applied in a serological assay to rapidly determine the protective nature of the vaccine strain against contemporary outbreak strains. The SAT2/ZIM/7/83 was used for the selection of scFv binders from a chicken IgY phage display library and and sequence analyses of the selected phage clones revealed three unique binders. Although two of the binders bound specifically to the ZIM/7/83 virus with no cross-reactivity to other SAT-type viruses, preliminary investigations indicate that phages produced from the binders are not recognising neutralising epitopes. Nonetheless, investigations are currently underway to determine whether the smaller, soluble scFvs are able to coat and neutralise the virus more efficiently. The alternative approach being followed to map the antigenic epitopes of SAT2 viruses integrate the capsid amino acid differences between isolates and vaccine strains to serological relatedness. Ten putative neutralising epitopes have been predicted on the virion using this approach, and these epitopes are currently being modified to the corresponding epitopes of an antigenic disparate virus. The contribution of each of the predicted epitopes will be determined using virus neutralisation assays using reference sera and the three scFv binders to distinguish if any differences in binding capabilities are observed.