title: Human IgG antibody to group b Streptococcus type III: comparison of protective levels in a murine model with levels in infected human neonates.
abstract: We determined the serum concentration of human IgG antibody to the native capsular polysaccharide of group B Streptococcus (GBS) type III needed to passively protect mice against lethal homologous challenge. Antibody was measured by an ELISA, standardized by two methods, and corrected for nonprecipitating antibody. A concentration of 1.3 micrograms of IgG antibody to GBS type III/ml protected 126 (97%) of 130 mice from an 80%-96% lethal dose bacterial challenge. Concentrations of IgG antibody to GBS type III in sera from 42 infected infants were less than or equal to 0.3 micrograms/ml. Concentrations of antibody ranged from less than 0.02 to 21.7 micrograms/ml in sera from 102 unselected pregnant women (median, 0.05 microgram/ml); 13% had concentrations greater than or equal to 1.3 microgram/ml. Levels in 25 women colonized with GBS type III who gave birth to normal infants were significantly higher and ranged from 0.1 to 10.7 microgram/ml (median, 0.78 micrograms/ml). In a study of transplacental passage of antibody, protective levels were found in a number of infants with gestational ages between 28 and 36 weeks.
mesh_terms: D000818:Animals; D002846:Chromatography, Affinity; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005312:Fetal Blood; D006801:Humans; D007116:Immunization, Passive; D007074:Immunoglobulin G / Q000032:analysis*; D007231:Infant, Newborn; D007234:Infant, Premature; D008297:Male; D008431:Maternal-Fetal Exchange; D051379:Mice; D011247:Pregnancy; D013291:Streptococcus / Q000276:immunology*
chemical_list: D007074:Immunoglobulin G