Fluorescence-Linked Immunosorbent Assay (FLISA) for Quantification of Antibodies to Food Antigens

Abstract

Serum antibodies of the IgG type from rabbits immunized with food antigens (beta-lactoglobulin, ovalbumin and gliadin) have been quantified using a fluorescence-linked immunosorbent assay (FLISA), with the antigens adsorbed as round spots (about 8 mm in diameter) on glass or plastic microscope slides. The indirect immunofluorescence intensities were determined using a microscope fluorometer, and compared to enzyme-linked immunosorbent assay (ELISA) in microtiter plates and diffusion-in-gel-E-LISA (DIG-ELISA) in plastic petri dishes. It was found that FLISA in general became more sensitive when the antigens had been adsorbed onto a plastic (Nunclon) than onto a glass surface. When the antigens were adsorbed to the plastic slides, the relative sensitivity order (maximum serum dilution) of the assays was in general the following, ELISA>FLISA>DIG-ELISA. The fluorescence-linked method appeared to require equal or less antigen and conjugated antiserum per sample. Due to the visual inspection of the surface, inhomogeneities of the antigen-coating could be readily discovered and evaluated by several measurements within the field of antigen-antibody reaction. It is proposed that spot FLISA may be an alternative to ELISA especially when the amount of antigen or antiserum is limited.