Polysaccharide antigens

Abstract

Culturing Streptococcus agalactiae in a nutrient broth containing at least 10 g/l of glucose while maintaining the pH at 6-8 by the addition of alkaline material produces polysaccharide antigen including a fraction having a molecular size from 8-11×10 5 d. By employing a broth free from constituents having a molecular size above 10 5 , the antigens can be separated from the broth in high yield after harvesting the organisms. Vaccination of humans with Streptococcus agalactiae polysaccharide antigens having molecular sizes above 5×10 5 produces in selected individuals specific antibody levels above 200 μg/ml of antisera; globulins fractionated from such antisera contain most of the antibody and can be used for passive immunization.

What is claimed is: 
     
       1. A polysaccharide antigen in purified form specific to Type III Group B streptococci consisting essentially of repeating units having the following composition: ##STR3## in which GlcNAcp stands for N-acetyl glucosamine (in the pyranose form), Galp stands for galactose (in the pyranose form), Glcp stands for glucose (in the pyranose form) and α-D-NANA stands for sialic acid, said polysaccharide having a molecular size from 0.8×10 6  to 6×10 6  daltons. 
     
     
       2. A polysaccharide antigen in purified form specific to Type Ia and Type Ic Group B streptococci .Iadd.made by culturing Type Ia and Type Ic Group B streptococci in nutrient broth at pH 6-8 containing at least 2 g/l of glucose and recovering from the broth a polysaccharide .Iaddend.consisting essentially of .[.repeating units having the following composition:.]. ##STR4## .[.in which GlcNAcp stands for N-acetyl glucosamine (in the pryranose form), Galp stands for galactose (in the pyranose form), Glcp stands for glucose (in the pryranose form) and α-D-NANA stand for sialic acid,.]. .Iadd.sialic acid, galactose, glucose, and glucosamine .Iaddend.said polysaccharide having a molecular size from 0.8×10 6  to 6×10 6  daltons.