Analysis of Listeria monocytogenes antigens with monoclonal antibodies.

Hybridomas secreting antibodies directed against Listeria monocytogenes were produced by the fusion of a drug sensitive tumor cell line with splenic B cells from mice immunized with L. monocytogenes. A solid phase radioimmunoassay (RIA) screening procedure was performed with three forms of listerial antigens: (i) heat killed L. monocytogenes (HKLM); (ii) isopycnic gradient purified soluble listerial proteins (SLP) and (iii) syngeneic macrophages which had ingested HKLM (MAC-LM). Ninety-three hybridoma lines were identified which showed antibody reactivity to at least one of the antigenic forms. The predominant isotypes of hybridoma derived antibodies were IgG2 and IgM. Of those antibodies reactive with HKLM 70% appeared species specific and did not react with L. grayi, L. denitrificans or L. murrayi. The others (30%) showed several cross-reactivity patterns with bacteria such as Staphylococcus aureus, Escherichia coli, and Bacillus subtilis. Interestingly, of those positive on MAC-LM (27), 13 lines were reactive only with HKLM, 8 with all three antigenic forms, and 6 were reactive only with MAC-LM. Three lines were also identified which reacted with SLP alone. We anticipate that these antibody reagents will prove extremely useful in the identification and purification of antigenic structures and in the study of macrophage functions relating to antigen processing and presentation.