Evaluation of transmission electron microscopy for examination of components of acellular pertussis and combination vaccines

New acellular pertussis and combination vaccines vary in the concentration and presence or absence of specific components and in extent of adsorption to adjuvants. There is a pressing need to develop new control methods for a cellular pertussis vaccines. Negative staining electron microscopy has been evaluated as a method for assessing the purity of individual vaccine compo nents and the amount of adsorption to aluminium gels. Negative staining sho wed the characteristic morphology of vaccine components and permitted detec tion of contaminants and morphological changes. Reproducible results were o btained by use of a standardized negative staining technique and confidence in the technique was increased by comparison of previously unexamined spec imens with a specimen that had been characterized by repeated observations. The degree of adsorption to aluminium adjuvants could only be assessed by observation of the amount of non-adsorbed material in the specimen. Negativ e staining electron microscopy can be used as one of a number of techniques for control of acellular pertussis combination vaccines. (C) 1999 The Inte rnational Association for Biologicals.