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 (TAGSΔΔTLR). We show that C-DIVA vaccination elicits
antibodies with high affinity for both the TAGSΔΔTLR 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 TAGSΔΔTLR
epitope followed by positive selection for
antibodies with affinity for the TAVSPTTLR
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.