Factors Affecting the Efficiency of the Aluminum Adjuvant in Diphtheria and Tetanus Toxoids

Summary The four most commonly used physicochemical states of the aluminum precipitate were compared in experimental animals as to efficiency as adjuvants for both diphtheria and tetanus toxoids, namely: AlPO4 preformed, and added to toxoid, and precipitated in the presence of the toxoid; and Al(OH)3 preformed, and added to toxoid, and precipitated in the presence of the toxoid. Findings for the two toxoids were not the same. There were significant differences between the adjuvant states for tetanus toxoid, but not for diphtheria toxoid. Tetanus toxoid adsorbed on a preformed precipitate was only about 60% as potent as when a nascent precipitate was formed in situ. Similarly tested, AlPO4 as adjuvant for tetanus toxoid was only about 60% as potent as Al(OH)3. The above findings with respect to tetanus toxoid were consistent in two experimental species, mice and guinea pigs. In the case of both diphtheria and tetanus toxoids, the circulating serum antitoxin levels of immunized guinea pigs were highly correlated with their survival times after challenge with the corresponding toxin.