Immunoglobulin M and immunoglobulin G responses in BALB/c mice to conjugated outer membrane extracts of four Salmonella serotypes.

Outer membranes (OMs) of Salmonella enteritidis, S. anatum, S. typhimurium, and S. infantis were extracted and cross-linked with glutaraldehyde to form a large macromolecular antigen. The antigen consisted of OM proteins and lipopolysaccharide and was designated 4-OMP-LPS. Polyacrylamide gel electrophoresis of extracted OMs from each serotype revealed differences in protein profiles. S. enteritidis and S. infantis possessed a greater variety of proteins than did S. anatum and S. typhimurium. Immunizations with 4-OMP-LPS in phosphate-buffered saline (4-OMP-LPS-C) and 4-OMP-LPS emulsified with muramyl dipeptide in the oil phase of a hexadecane-water emulsion (4-OMP-LPS-MDP) revealed that BALB/c mice were capable of eliciting specific primary and secondary immunoglobulin M (IgM) and IgG responses. Both antigen preparations were capable of eliciting IgM and IgG specific for the cell surfaces of each live Salmonella serotype. Also, 4-OMP-LPS-MDP and 4-OMP-LPS-C were capable of evoking a substantial anamnestic response. Adsorption studies revealed that the combined serotypes had the antigenic capacity to adsorb up to 94% of the antibodies, but 4-OMP-LPS-MDP antibodies were more effectively adsorbed than were 4-OMP-LPS-C antibodies. Adsorption of pooled antiserum with heterologous bacteria yielded a variety of adsorption profiles.