Protective effects of polyclonal sera and of monoclonal antibodies active to Salmonella minnesota Re595 lipopolysaccharide during experimental endotoxemia.

Mice were passively immunized with sera from blood donors active for rough lipopolysaccharides (LPS), the J5 (Rc chemotype) mutant of Escherichia coli O111:B4, and the Re595 (Re chemotype) mutant of Salmonella minnesota. All protected the mice against lethal challenge with smooth E. coli WF96 LPS, E. coli and Salmonella rough mutant LPS, or free lipid A. Epitopes recognized by monoclonal antibodies (MAbs) reacting with the LPS of S. minnesota Re595 or lipid A were localized in the 2-keto-3-deoxy-D-manno-octulosonic acid (KDO) region and on lipid A. Core-reactive MAbs reacted with their homologous Re LPS and with free lipid A. One, GL11, cross-reacted with the KDO alone. MAbs GL6, GL11, L.4, L.6, and L.8 protected the actinomycin D-sensitized mice against the lethal effects of LPS from E. coli WF96, Salmonella enteritidis, E. coli J5, S. minnesota Re595, and free lipid A. The GL11 antibody was also protective when injected after LPS challenge. These results indicate that antibodies directed against the core glycolipid of S. minnesota Re595 LPS may be useful as an additive form of therapy that may enable decreased mortality during gram-negative bacterial sepsis.