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Monoclonal Antibodies Against Erwinia amylovora: Characterization and Evaluation of a Mixture for Detection by Enzyme-Linked Immunosorbent Assay. R. J. McLaughlin, Postdoctoral research associate, USDA-ARS, Eastern Regional Research Center, Philadelphia, PA 19118; T. A. Chen(2), and J. M. Wells(3). (2)Professor, Department of Plant Pathology, Cook College, Rutgers University, New Brunswick, NJ 08903; (3)Research plant pathologist, USDA-ARS, Eastern Regional Research Center, Philadelphia, PA 19118. Phytopathology 79:610-613. Accepted for publication 11 January 1989. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1989. DOI: 10.1094/Phyto-79-610.

Eight monoclonal antibodies that specifically react against antigens of Erwinia amylovora were evaluated. These antibodies were characterized to determine the type of antigens that they recognize and whether they are directed against different epitopes. Six reacted with protein antigens, as determined by loss of reactivity in indirect enzyme-linked immunosorbent assay (ELISA) after treatment of sonicated cells with proteinase K. Two of the antibodies (MA-8 and MA-23) reacted with purified lipopolysaccharide from E. amylovora; reactivity of these antibodies with sonicated antigen was not lost after proteinase K treatment. Four antibodies belonged to immunoglobulin class IgG1, three to subclass IgG2b, and one to subclass IgG2a. In an ELISA designed to determine epitope specificity, antibodies MA-12, MA-21, and MA-37 clearly bound to different epitopes. Antibodies MA-27 and MA-33 were complemented by MA-8, indicating similarity of binding sites, and two (MA-23 and MA-30) were too low in reactivity to determine epitope specificity. Antibodies MA-8, MA-12, and MA-21 were chosen, based on epitope binding specificity and reactivity in ELISA, to determine whether a mixture of antibodies would improve detection of E. amylovora by ELISA. Increased sensitivity of detection was observed with the mixture at the detection limits of ELISA (4.0 log cfu) and at cell concentrations up to 5.5 log cfu.