Effect of Type-Specific Antiserum on the Pulmonary Hypertensive Response to Group B Streptococcus in Piglets

Abstract

Group B streptococcal (GBS) organisms are a major cause of serious bacterial infections in newborns. Both clinical and laboratory studies have shown that GBS infection is associated with circulatory disturbances including pulmonary hypertension, which may lead to the persistent pulmonary hypertension of the newborn syndrome. Previous studies in our laboratories have shown that pretreatment of GBS organisms premixed with rabbit polyclonal type-specific antibody will augment the pulmonary hypertension seen with GBS organisms alone [1]. Since passive immunotherapy is being used clinically to treat infected infants, we thought it important to further evaluate the interaction of type-specific antigen and antibody in the cardiovascular disturbances induced by GBS sepsis. Availability of a mutant GBS organism which expresses no detectable type-specific antigen [2] allowed us to study the effect of antibody, with and without its antigen, on the cardiovascular hemodynamics of GBS infusion. We tested the hypotheses that (1) administration of encapsulated GBS organisms premixed with type-specific antibodies exacerbates the adverse effects caused by injection of GBS organisms alone, and (2) type-specific antibodies do not alter hemodynamic responses to the injection of a capsule-deficient mutant GBS organism