Several lines of evidence suggest that passive immunization as adjunctive
therapy for or prevention of group B streptococcal (GBS)
sepsis in neonates will require the use of preparations of human
intravenous immune globulin (
IVIG) that are hyperimmune for protective
antibodies to GBS. Results from both in vitro and in vivo experiments utilizing commercially available
IVIG preparations suggest that the doses necessary for achieving levels of pathogen-specific antibody capable of promoting efficient opsonization and phagocytosis of GBS may be prohibitive. Several laboratories have reported that standard
IVIG preparations contain only modest levels of
antibodies to the four capsular
polysaccharides of GBS (the protective moieties), are variable in their effect on in vitro opsonophagocytosis by dose and method of preparation, and are significantly less protective in animal models than is
IVIG prepared from adults immunized with GBS
polysaccharide vaccines. Further, when we gave a single infusion of standard
IVIG at a dose of either 500 or 750 mg/kg to 10 premature neonates during the first week of life, opsonophagocytosis of type III GBS by their sera and adult neutrophils was observed only when high levels of specific antibody were achieved, levels only transiently achieved in nonimmune infants. Commercial preparation of human
immune globulin hyperimmune for GBS will be required for optimal adjunctive
therapy in patients with
sepsis due to GBS and for the possible prevention of late-onset infant disease.