Discrimination within epitope specific antibody populations against Classical swine fever virus is a new means of differentiating infection from vaccination

Serological differentiation between infection and vaccination depends on the detection of pathogen specific antibodies for an epitope that is modified or lacking in a vaccine. Here we describe a new assay principle that is based on differences in the binding properties of epitope specific antibodies. C-DIVA is a potent Classical swine fever vaccine candidate that differs from the parental C-strain life attenuated vaccine in the highly immunogenic TAVSPTTLR epitope by the deletion of two and the mutation of one amino acid (TAGS Delta Delta TLR). We show that C-DIVA vaccination elicits antibodies with high affinity for both the TAGS Delta Delta TLR and TAVSPTTLR epitope, whereas infection elicits only TAVSPTTLR specific antibodies. Differentiation is achieved with a double competition assay with negative selection for antibodies with affinity for the TAGS Delta Delta TLR epitope followed by positive selection for antibodies with affinity for the TAVSFTTLR epitope. Our findings add a new strategy for the development of marker vaccines and their accompanying discrimination assays and offer an alternative to the devastating stamping out policy for Classical swine fever. (C) 2015 Elsevier B.V. All rights reserved.