Immunogenicity of polysaccharides from type III, group B Streptococcus

Area of Science:

• Bacteriology
• Immunology
• Vaccine Development

Background:

• Group B Streptococcus (GBS) is a leading cause of invasive disease in infants.
• Effective vaccines are needed to prevent GBS infections.
• Natural antibody levels to GBS capsular polysaccharide vary in adults.

Purpose of the Study:

• To evaluate the immunogenicity and safety of two GBS type III polysaccharide vaccines.
• To assess antibody response in adults with low pre-existing antibody levels.

Main Methods:

• Two polysaccharide vaccines (trichloroacetic acid and EDTA methods) were prepared from GBS type III.
• Vaccines were tested for pyrogenicity and toxicity in animals.
• Adults received a single 50-microgram subcutaneous injection.
• Antibody concentrations were measured and compared to controls.

Main Results:

• Both vaccines were non-pyrogenic and non-toxic in animals.
• A significant increase in antibody concentration was observed in vaccinees compared to controls.
• Antibody levels peaked by 2 weeks and were sustained for 21 weeks.
• The larger molecular size polysaccharide vaccine was more immunogenic.
• Mild, transient local reactions occurred in 45% of vaccinees; no systemic reactions were recorded.

Conclusions:

• Subcutaneous administration of GBS type III polysaccharide vaccines is safe and immunogenic in adults.
• Vaccine-induced antibodies are primarily IgG and persist for at least 21 weeks.
• Polysaccharide size influences immunogenicity, with larger molecules being more effective.