2014-10-24-世界卫生组织-WHO_BS_2014.2234_Collaborative_study_to_evaluate_a_candidate_IS_for_anti-Typhoid_capsular_Vi_polysaccharide_IgG_human_25页_831kb

WHO Expert Committee on Biological Standardization Collaborative Study: Evaluation of Candidate International Standard 10/126 for Anti-Typhoid Capsular Vi Polysaccharide IgG (Human)

A collaborative study assessed candidate International Standard (IS) 10/126, derived from pooled human serum of volunteers vaccinated with Vi-TT, for use in Vi-specific ELISAs. Ten laboratories from seven countries evaluated its suitability.

Potency varied by ELISA format: GM relative potency was 0.65 (GCV 15%), 1.40 (GCV 67%), and 0.41 (GCV 77%) for kit, Vi 05, and in-house ELISAs, respectively. Overall GM was 0.80 (95% CI 0.52–1.24; GCV 105%).

The candidate IS was deemed suitable, and the Committee recommended its establishment as the first International Standard for anti-Typhoid Vi polysaccharide IgG with assigned potency 0.5 IU per ampoule. Study results highlighted significant variability in ELISA formats, attributed to differences in reference material matrices, reagent preparations, and potential non-specific binding. This underscores the need for further standardization of Vi ELISAs.

Stability testing showed minimal potency loss at storage temperatures, including -20°C. No other major deviations or safety concerns were noted, with recommendations for ongoing calibration and use in immunogenicity assessments.