MONOCLONAL-ANTIBODIES WITH A HIGH-DEGREE OF SPECIFICITY FOR LISTERIA-MONOCYTOGENES SEROTYPE 4B

Strains of Listeria monocytogenes serotype 4b account for a large frac tion of sporadic listeriosis cases, as well as all major food-borne ep idemics attributed to this pathogen. We have identified a set of three monoclonal antibodies which showed a high degree of specificity for s trains of L. monocytogenes serotype 4b. Two of these antibodies (c74.3 3 and c74.180, isotypes immunoglobulin M [IgM] and IgG3, respectively) recognized all serotype 4b strains, whereas antibody c74.22 (isotype IgG1) failed to recognize certain epidemic-associated strains. The cor responding antigens were located on the surface of the bacteria and we re expressed following bacterial growth in different media and over a wide range of temperatures (4, 22, and 37 degrees C). Heating L. monoc ytogenes cells at 80, 90, or 100 degrees C abolished reactivity for c7 4.22 but not for c74.33 MAb. These MAbs were negative for all of the n on-listeria strains tested, including representatives of several gram- negative and gram-positive species. The surface antigen recognized by c74.22 appeared to be associated with the ability of the bacteria to e nter (invade) mammalian cells in culture.