Electron immunocytochemical localization of Actinobacillus actinomycetemcomitans leukotoxin.

The Actinobacillus actinomycetemcomitans leukotoxin was localized in A. actinomycetemcomitans bacteria using an electron immunocytochemical thin-section labeling method. An immuno-dot blot procedure was initially used to ascertain the optimal specimen fixation. This consisted of a periodate-lysine-paraformaldehyde (2%) fixative in a phosphate buffer followed by embedding in LR White. Affinity-purified toxin was used to produce a monospecific polyclonal antibody. The reaction sites were visualized with a colloidal gold-tagged reporter antibody. The leukotoxin was found to be localized either in the cell envelope and/or in membranous vesicles on the outer surface of the bacterial cell. These results support previous observations indicating the same location.