Further studies on the adjuvant for dried BCG vaccine.

The authors describe some recent investigations undertaken in Japan with the object of finding an adjuvant for dried BCG vaccine which would make it possible for the vaccine to be stored at room temperature in tropical countries without suffering any serious loss of viability.The first series of experiments, carried out with sodium glutamate as adjuvant, was designed to determine the effect of the concentration of adjuvant, the concentration of bacilli, the pH of the bacterial suspension, and the method of freeze-drying on the preservability of the vaccine. The sucrose vaccine in current use in Japan served as a control. In the light of the results, the authors make certain suggestions as to the optimum conditions for freeze-drying, but they stress that their proposals are tentative and that further research on the subject is needed.In the second series of experiments the authors investigated the adjuvant properties of certain organic acids known to be involved in the metabolic reactions of the tubercle bacillus. Reasonably good results were obtained with alpha-ketoglutaric, malic, lactic, and citric acids, but none of these substances proved to be as satisfactory an adjuvant as sodium glutamate for storage at 37 degrees C.