A liquid-phase ELISA and its use in the identification of epitopes on foot-and-mouth disease virus antigens.

An enzyme-linked immunosorbent assay was developed which would detect antigen/antibody reactions in liquid-phase; that is under test conditions which should not alter the structure or reactivity of either antigen or antibody. This liquid-phase ELISA was at least as efficient, both qualitatively and quantitatively, as the double sandwich or antigen-trapping ELISA (Crowther and Abu Elzein, 1979), but six to eight times more sensitive than the indirect ELISA. The liquid-phase test can be used to assay both antisera and hybridoma cultures, and will show the greatest discrimination of antibody specificities. Since the liquid-phase ELISA will detect antibody/antigen reactions which are of direct relevance to the protective immune response in vivo (opsonisation; neutralisation of pathogen infectivity), it is recommended that this assay should be used to characterise the antibody reactivity of antisera and hybridoma culture supernatants.