Quantitation of IgG Antibodies to Type Ia Group B Streptococcal Type-Specific Polysaccharides Measured by Enzyme-Linked Immunosorbent Assay

The type-specific polysaccharide antigen of the group B streptococcus (GBS) type Ia as extracted and purified according to the procedures of Kane and Karakawa. Using this purified polysaccharide antigen, we made a sensitive and specific assay system of enzyme-linked immunosorbent assay (ELISA) and measured the titres of of the type-specific antibodies in maternal sera and cord blood sera. The titres of antibodies in 78 pregnant women (26 Ia carriers, 18 other types of GBS carriers and 34 non carriers) were compared. A mother of an infant affected by early onset infection of GBS Ia had a titre of antibody 1:10 at delivery, while 2 years later she became a non carrier and had a titre of antibody over 1:160. The titres of antibodies in 27 pair sera of mothers and cords were well correlated.