title: Estimation of protective levels of anti-O-specific lipopolysaccharide immunoglobulin G antibody against experimental Escherichia coli infection.
abstract: Serum obtained after immunization with an O18 polysaccharide-toxin A conjugate vaccine was evaluated for the estimation of protective levels of anti-O-specific lipopolysaccharide (LPS) immunoglobulin G (IgG) antibody against bacteremia and death caused by a homologous serotype of Escherichia coli K1 strains. Passive transfer of rabbit serum conferred significant protection from a lethal E. coli infection in a neonatal rat model. The overall incidence of bacteremia and mortality was 4% in rat pups receiving undiluted postvaccination serum, while that in control animals was 100% (P < 0.001). The overall incidences of bacteremia were 5 and 72% for animals with serum anti-O18 LPS IgG concentrations of > 1.0 and < 1.0 microgram/ml, respectively, while the overall incidences of mortality for animals with serum anti-O18 LPS IgG levels of > 1.0 and < 1.0 microgram/ml were 0 and 72%, respectively (P < 0.001). Protection against E. coli infection was also demonstrated with human anti-O18 polysaccharide IgG. None of the animals with human anti-O18 LPS IgG levels of > 1 microgram/ml had bacteremia after bacterial challenge, whereas all animals with bacteremia at 18 h had levels of < 1 microgram/ml. These findings suggest that serum anti-O18 LPS IgG concentrations of > 1.0 microgram/ml may provide protection against bacteremia and death caused by a homologous E. coli K1 infection.
authors.affiliation: Childrens Hospital Los Angeles, California 90027.
authors.forename: D E
authors.initials: DE
authors.lastname: Schiff
authors.forename: C A
authors.initials: CA
authors.lastname: Wass
authors.forename: S J
authors.initials: SJ
authors.lastname: Cryz
authors.forename: A S
authors.initials: AS
authors.lastname: Cross
authors.forename: K S
authors.initials: KS
authors.lastname: Kim
mesh_terms: D000818:Animals; D016470:Bacteremia / Q000276:immunology; D004926:Escherichia coli / Q000276:immunology; D004927:Escherichia coli Infections / Q000276:immunology / Q000517:prevention & control*; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D008070:Lipopolysaccharides / Q000276:immunology*; D019081:O Antigens; D011135:Polysaccharides, Bacterial / Q000276:immunology*; D011247:Pregnancy; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D007074:Immunoglobulin G; D008070:Lipopolysaccharides; D019081:O Antigens; D011135:Polysaccharides, Bacterial