Transplacental or Enteral Transfer of Maternal Immunization-Induced Antibody Protects Suckling Rats from Type III Group B Streptococcal Infection

Abstract

Deficiency of maternal group B streptococcal (GBS) type-specific IgG increases neonatal susceptibility to GBS infection. We asked if immunization-induced maternal type III GBS opsonic antibody transferred prenatally (via placenta) or postnatally (via breast milk) would affect suckling rat survival after GBS infection. Pregnant immunized dams with type III GBS opsonic antibody (20 through 320 dil-1) and nonimmunized dams without GBS antibody were matched (n = 16). Half of each litter was cross-suckled to a matching dam creating four pup groups with different exposure to maternal type III GBS opsonic antibody: none, postnatal, prenatal, and combined (pre- and postnatal). After infection with type III GBS, group survival (n) was 41% (51), 66% (47), 98% (43), and 98% (47), respectively. Type III GBS opsonic antibody in surviving pups was directly related to their immunized dam's antibody either postnatally (R = 0.85), prenatally (R = 0.84), or combined (R = 0.81). Pups exposed postnatally to high titers (80 to 320 dilution-1) of type III GBS opsonic antibody survived more often than those exposed to low titers (20 to 40 dil-1) (p less than 0.03). Immunization-induced maternal type III GBS opsonic antibody is transferred pre- and postnatally and results in improved neonatal survival after GBS infection. Survival of pups exposed to postnatal antibody appears related to the concentration of maternal type III GBS opsonic antibody. Breast milk with high titers of GBS type-specific antibody may modify the course of GBS infection. GBS vaccines and strategies could be tested in this model.