Human monoclonal antibody with protective activity for Escherichia coli K1 and Neisseria meningitidis group B infections.

We produced human monoclonal antibody that demonstrated specific reactivity to the K1 capsule of Escherichia coli and the group B polysaccharide of Neisseria meningitidis. The antibody was nonreactive with several strains of K1- E. coli and other gram-negative bacteria. All E. coli K1 clinical isolates tested were reactive with the antibody. When assayed for in vitro opsonophagocytic ability, the antibody caused bacterial removal only in the presence of human complement and neutrophils, an observation suggesting a non-bacteriolytic, neutrophil-dependent killing mechanism. Finally, and perhaps most importantly, the antibody was highly protective for infectious disease when used prophylactically in three animal models. The data suggest a potential use for human monoclonal antibodies in preventing and/or treating infections of the blood.