Prevention and therapy of experimental Escherichia coli infection with monoclonal antibody.

Mouse hybridoma antibody of immunoglobulin class M prepared with live group B meningococci was evaluated for its ability to protect against and treat Escherichia coli infections in a newborn-rat model. In these studies, antibody was administered intraperitoneally and bacteria were administered subcutaneously to avoid introducing the antibody and bacteria to the same site. The activity of this hybridoma antibody was specific; the antibody provided protection against the K-1 strain, but not against the K-92 strain. In addition, the amount of the antibody required for protection was dependent upon the size of bacterial challenge. With an increase of the bacterial inocula from the 100% lethal dose to 10 times the 100% lethal dose there was a threefold increase in the amount of the antibody required for 50% protection. Similarly, therapeutic efficacy of the antibody was also dependent upon the magnitude of bacteremia before therapy. The antibody successfully cleared the bacteremia only when the pretherapy bacterial counts in blood were less than 10(4) CFU/ml. These findings suggest that the monoclonal immunoglobulin M antibody against the capsular polysaccharide of the group B meningococcus may be useful in the prevention and treatment of K-1 E. coli infections.