2015-10-24-世界卫生组织-WHO_BS_2015.2255.Add.1_Evaluation_of_candidate_IS_for_Meningococcal_Serogroups_A_and_X_polysaccharide_46页_1mb

Summary of the Evaluation of Candidate International Standards for Meningococcal Serogroups A and X Polysaccharides

Core Content

This document outlines the evaluation of two candidate International Standards for meningococcal serogroup A (MenA) and X (MenX) polysaccharides (PS) by the Expert Committee on Biological Standardization (ECBS). The goal is to establish these standards for use in quantification assays of vaccines and vaccine components, ensuring consistency and reliability in manufacturing and testing.

Main Points

• Purpose: To evaluate the suitability of candidate MenA and MenX PS standards for use in quantification assays, and to recommend their establishment as International Standards.
• Collaborative Study: Eleven laboratories from nine countries participated in the study, including 5 National Control Laboratories (NCLs), 5 manufacturers, and 1 Pharmacopoeia laboratory.
• Candidate Materials:
  • MenA PS (13/246): Purified from Serum Institute of India Ltd. and stored at -70°C. It was filled into 10,786 ampoules.
  • MenX PS (14/156): Provided by the Finlay Institute, Havana, and stored at -70°C. It was filled into 916 ampoules.
• Quantification Methods:
  • Quantitative NMR (qNMR): Used to determine the PS content with a level of confidence of 95% and an expanded uncertainty of k = 2.45.
  • Colorimetric Assays: Commonly used to quantify MenA and MenX PS, with additional use of ICP methods (Optima 2100 DV and ICP-MS) by some labs.
  • HPAEC-PAD: Used for measuring saccharide content, with different hydrolysis conditions for MenA and MenX.
  • Nephelometry and ELISA: Employed for antigen detection, with ELISA using monoclonal antibodies to capture MenA PS.
• Stability Studies:
  • Real-Time Stability: Conducted at -20°C for up to 12 months (MenA) and 6 months (MenX).
  • Accelerated Thermal Degradation: Performed at +4°C, +37°C, and +56°C for up to 12 months (MenA) and 6 months (MenX).
  • Reconstituted Stability: Evaluated after reconstitution in sterile water, stored at +4°C for 1–4 weeks and at -20°C for 4–8 weeks.
• Results:
  • The MenA PS standard (13/246) was found to be stable at -20°C and +4°C, with a content of 0.845 ± 0.043 mg per ampoule, as determined by qNMR.
  • The MenX PS standard (14/156) was found to be stable at -20°C and +4°C, with a content of 0.776 ± 0.089 mg per ampoule, also determined by qNMR.
  • Both standards showed a reduction in size under accelerated conditions, but the polysaccharide content remained constant.
  • Water was chosen as the diluent for both standards due to its stability and simplicity.
• Recommendation:
  • The MenA PS standard (13/246) is recommended as the 1st International Standard for Meningococcal Serogroup A Polysaccharide.
  • The MenX PS standard (14/156) is recommended as the 1st International Standard for Meningococcal Serogroup X Polysaccharide.
• Unitage Assignment:
  • Based on WHO guidelines, the unitage for these standards is assigned in SI units (mg), derived from qNMR rather than bioassays.
  • The functional weight of MenA PS (13/246) is 337.515 g/mol, and for MenX PS (14/156) is 302.2 g/mol.
  • Conversion factors from phosphorus content to PS amount are 10.897 for MenA and 9.757 for MenX.

Key Information

• Materials and Methods:
  • The candidate materials were prepared and filled at NIBSC.
  • Each preparation was labeled with a unique code (13/246 for MenA, 14/156 for MenX).
  • The materials were divided into three reference types: International Standard, Working Standard, and Pharmacopoeial Standard.
• Study Design:
  • Participants were provided with duplicate samples and asked to perform assays twice using fresh ampoules.
  • The content of the standards was provided as a guideline (0.5–3 mg per ampoule).
  • Assays were conducted using in-house standards and the candidate standards.
• Uncertainty and Traceability:
  • The uncertainty was calculated using qNMR and included combined uncertainties from multiple determinations.
  • The standards are traceable to physicochemical methods, aligning with WHO guidelines.
• Distribution:
  • 3000 ampoules of 13/246 and 856 ampoules of 14/156 were offered to WHO.
  • NIBSC acts as the custodian of the standards, stored at -20°C.
• Additional Considerations:
  • The study emphasized the importance of harmonizing PS content across meningococcal vaccines.
  • The development of new conjugate and multivalent vaccines highlights the need for standardized PS quantification methods.

Conclusion

The evaluation concluded that both MenA and MenX PS candidate materials are suitable for establishing International Standards. These standards will support the consistent quantification of polysaccharides in vaccines and vaccine components, and facilitate the calibration of assays and in-house reference materials. The recommendation to adopt these standards aligns with WHO guidelines and ensures the reliability and traceability of PS quantification in meningococcal vaccines.