Production and Epitopic Characterization of Monoclonal Antibodies Against Bovine β-Lactoglobulin

Sixty-nine murine monoclonal antibodies were produced against the bovine β-lactoglobulin (β-LG) variant B. Thirty-eight specificity groups of monoclonal antibodies were defined according to the reactivity in indirect or capture ELISA with bovine β-LG B, for bovine β-LG B coated at pH ranging from 2.3 to 9.4, and for β-LG with naturally occurring residue substitutions such as bovine β-LG variant A and ovine, caprine, porcine, and equine β-LG. Ten monoclonal antibodies appeared to be monospecific for bovine β-LG, 58 monoclonal antibodies recognized only ruminants β-LG, and 1 recognized all species. The specificity of the monoclonal antibodies was also studied with sequenced tryptic peptides of β-LG variant B. Critical residues involved in the epitopes of nine classes of monoclonal antibodies were characterized. Moreover, 5 monoclonal antibodies were able to discriminate between a fresh solution of β-LG and a solution that had been stored for ≥2 d at 4°C, and 3 monoclonal antibodies distinguished bovine β-LG that has been purified by gel filtration from that purified by salt fractionation. This array of monoclonal antibodies could be efficient probes for characterizing conformational structures involved in biological properties of β-LG (e.g., interaction with ligands and hypersensitivity reactions) and for studying conformational changes occurring upon physical treatments such as heat denaturation.