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Updated: Nov 3, 2025
Opsonophagocytic Killing Assay to Assess Immunological Responses Against Bacterial Pathogens
Published on: April 5, 2019
Development and Validation of Enzyme-Linked Immunosorbent Assay for Group B Streptococcal Polysaccharide Vaccine
A-Yeung Jang1, Min-Joo Choi2, Yong Zhi3,4
1Department of Internal Medicine, Division of Infectious Diseases, Korea University College of Medicine, Seoul 08308, Korea.
Insights
A new enzyme-linked immunosorbent assay (ELISA) effectively measures immune responses to Group B Streptococcus (GBS) vaccines. This assay is crucial for developing and evaluating GBS vaccines against common serotypes.
Area of Science:
- Immunology
- Vaccinology
- Microbiology
Background:
- Group B Streptococcus (GBS) causes severe neonatal infections like sepsis and meningitis.
- Current GBS prevention methods have limitations, highlighting the need for effective vaccines.
Purpose of the Study:
- To develop and validate a standardized enzyme-linked immunosorbent assay (ELISA) for evaluating GBS vaccine immunogenicity.
- To assess the assay's performance against GBS serotypes Ia, III, and V.
Main Methods:
- Developed a GBS-specific ELISA using a four-parameter logistic curve-fitting method.
- Validated specificity through homologous and heterologous capsular polysaccharide (PS) adsorption.
- Assessed assay precision using multiple serum samples across independent experiments.
Main Results:
- The GBS-ELISA demonstrated high specificity, with significant homologous PS adsorption (>75% inhibition).
- The assay showed distinct antibody level reductions for different serotypes after heterologous PS adsorption.
- High precision was confirmed with a coefficient of variation <5% across experiments.
Conclusions:
- The developed GBS-ELISA is a practical and reliable tool for large-scale immunogenicity evaluation of GBS vaccines.
- This assay will aid in the development and assessment of new GBS vaccines targeting key serotypes.
Abstract:
Streptococcus agalactiae (group B Streptococcus, GBS) is a leading cause of neonatal sepsis and meningitis in infants. Limitations of prenatal GBS screening and intrapartum antibiotic prophylaxis render developing GBS vaccines a high priority. In this study, we developed an enzyme-linked immunosorbent assay (ELISA) for the practical and large-scale evaluation of GBS capsular polysaccharide (PS) vaccine immunogenicity against three main serotypes, Ia, III, and V. GBS-ELISA was developed and subsequently validated using a standardized curve-fitting four-parameter logistic method. Specificity was measured using adsorption of serum with homologous and heterologous PS. Homologous adsorption showed a ≥75% inhibition of all three serotypes, whereas with heterologous PS, IgG GBS-ELISA inhibited only ≤25% of serotypes III and V. However, with serotype Ia, IgG antibody levels decreased by >50%, even after adsorption with heterologous PS (III or V). In comparison, the inhibition opsonophagocytic killing assay (OPA) of serotypes Ia GBS exhibited a reduction in opsonophagocytic activity of only 20% and 1.1% for serotypes III and V GBS, respectively. The precision of the GBS-ELISA was assessed in five independent experiments using four serum samples. The coefficient of variation was <5% for all three serotypes. This standardized GBS-ELISA would be useful for GBS vaccine development and its evaluation.
