WHO/BS/2017.2315 Collaborative Study for Evaluation of Proposed 2nd IS for Pertussis Toxin Code: 15/126

Overview

Reference preparations of pertussis toxin (PTx) are needed for the quality control and assessment of pertussis vaccines. Stocks of the existing WHO 1st International Standard (IS) for Pertussis Toxin (JNIH-5) are low and a replacement is required. One candidate material was donated by a vaccine manufacturer to NIBSC. It was formulated, lyophilised into sealed glass ampoules and coded 15/126. An international collaborative study was organized to determine the suitability of this material to replace JNIH-5 as the second International Standard for Pertussis Toxin and to assign potency values to 15/126 relative to the current IS (JNIH-5). International Units were estimated for the proposed 2 nd IS using the lethal murine histamine sensitisation assay (HIST) and the Chinese Hamster Ovary (CHO) cell clustering assay as these were the methods used to assign units to JNIH-5. Other in vitro methods for the measurement of pertussis toxin activity were also performed in the study and the behaviour of the material in these assays assessed. A total of 14 laboratories from 12 countries took part in the study. Eleven of these performed HIST, 14 performed CHO cell clustering assay and three performed the biochemical assays (which measure the enzymatic and carbohydrate binding activities of the toxin).