Pharmaceutical Characterization of Mycobacterium bovis Bacillus Calmette-Guérin (BCG) Vaccine Used for the Treatment of Superficial Bladder Cancer

Abstract

Mycobacterium bovis bacillus Calmette-Guérin (BCG) vaccine, developed in the 1920s as a treatment and prophylactic for tuberculosis, has proved to be a nonspecific stimulant of the immune system and is now the major form of clinical immunotherapy approved for the treatment of superficial bladder cancer in the United States. However, methods for the production and physical characterization of the vaccine have not been significantly developed since Calmette and Guérin first devised their process for attenuating the organism in 1908. When reconstituted with sterile water immediately before use, the vaccine consists of a suspension of cellular fragments and aggregates and a mixture of dead and living cells. The dose is determined by the number of colony-forming units that develop when the vaccine is allowed to grow in a nutrient medium. This measurement of dose and viability is misleading because each cellular aggregate may consist of several hundred individual cells, but only one need be living to give rise to a single visible colony. Viability should therefore be measured on the basis of residual ATP levels. In this report, the mode of action of BCG vaccine against bladder cancer is reviewed, and attention is drawn to some factors that may need to be controlled during manufacturing and subsequent quality assurance procedures. The morphology of the various parts of the complex pleomorphic life cycle of this Mycobacteriumspecies has been investigated, and the vaccine has been physically evaluated to provide a characterization by contemporary methodologies, including measurement of ATP content and particle size distribution of the dispersed mycobacterial aggregates.