Protective efficacy of a modified immune serum globulin in experimental group B streptococcal infection

In spite of aggressive antimicrobial therapy and extensive support measures, the mortality rate in early-onset group B streptococcal infection continues to be exceedingly high. In previous studies, we have demonstrated that passive immunotherapy with fresh whole blood containing opsonic antibody-improved survival in human neonates with group B disease. Transfusion of whole blood, plasma, or other blood products has a number of drawbacks, however. In the present study, we have evaluated immune serum globulin and a preparation of ISG modified for intravenous use for levels of type-specific antibody, opsonic activity, and protective efficacy against type Ia, II, and III group B streptococci. Type-specific antibody was detected in most of the preparations tested. In general, the level in MISG was less than that in the comparison ISG lot. Opsonic activity was also detected in these preparations against the more antibody-sensitive group B strains but was not present for opsonin resistant strains of type Ia, II, and III. Both ISG and MISG provided protection in neonatal rats infected with group B streptococci; in most cases MISG was more efficacious than the ISG from which it was made. These studies suggest that passive immunotherapy with MISG may be a valuable adjunct to current regimens used in the management of early-onset group B disease. This would be especially so if donors could be selected whose serum or plasma contained high levels of opsonic and protective activity against both antibody-sensitive and antibody-resistant group B strains.