Murine hybridoma antibodies enhance bactericidal activity of human cord blood against K1 Escherichia coli strains.

Murine hybridoma antibodies directed against the capsule and O-side chain determinants of the Escherichia coli strain Bort (018ac:K1:H7) were evaluated for their ability to enhance bactericidal activity of cord blood against K1 E. coli strains possessing O antigens common in neonatal E. coli infection, i.e. 018, 07, and 01. The antibodies to the K1 capsule and O-side chain efficiently enhanced cord polymorphonuclear leukocyte-mediated killing of K1 encapsulated E. coli strain possessing a homologous O antigen, but the IgM antibody to the K1 capsule exhibited approximately 10-fold greater activity than did the IgG3 antibody to O-side chain (weight basis). Both antibodies required complement for their opsonic activities. Our findings indicate that antibodies directed against the capsule and O-lipopolysaccharides are able to restore the opsonic activity of cord blood against K1 E. coli, suggesting that these antibodies may be useful in the prevention and therapy of neonatal E. coli infection.