ASSESSING THE QUALITY OF THE STANDARD BATCH OF DIPHTHERIA TOXIN DiTox Vn03 USED FOR POTENCY CONTROL TEST OF DIPHTHERIA COMPONENT BY CHALLENGE ASSAY AND VERO CELL METHOD

Abstract

The potency of the diphtheria vaccine is determined by the guinea pig challenge method and the Vero cell neutralization assay (using mouse serum). Both methods require the use of a reference diphtheria toxin whose potency has been determined as toxic units or LD₅₀ (for the challenge method) or Lm dose (for the Vero cell assay). To meet this requirement, a standard batch of diphtheria toxin DiTox Vn03 was prepared and then evaluated its quality as a secondary standard sample for diphtheria potency testing using both methods. This study aimed to assess the quality and stability of the diphtheria batch of diphtheria toxin Ditox Vn03. The LD₅₀ stability of the toxin batch was estimated annually from 2020 to 2025 and monitored through back titration of the challenge toxin in the diphtheria potency test. The results showed that we produced 150 tubes of DiTox Vn03 toxin reaching an average of 2834,81LD₅₀ units; the Lm/10000 dose reached 9600Lm/ml, and the Lm/100000 dose reached 96000Lm/ml. The DiTox Vn03 toxin batch is stable after 5 years of storage at temperatures ≤ -40^oC, suitable for determining the potency of the diphtheria component using both methods.