Evaluation of endotoxin content of diphtheria-tetanus-acellular pertussis combined (DTaP) vaccines that interfere with the bacterial endotoxin test.

Applicability of the endotoxin test to diphtheria-tetanus-acellular pertussis combined (DTaP) vaccines was examined. We found some DTaP vaccines that strongly interfered with Limulus amoebocyte lysate (LAL) activity of endotoxin without affecting lethal activity of endotoxin in D-galactosamine-treated mice. LAL activity that was interfered in such vaccines increased apparently after the treatment with phosphate buffer at 4 degrees C for a week. The DTaP vaccines that interfered with the endotoxin test showed no significant effect on endotoxin activity in inducing tumor necrosis factor-alpha (TNF-alpha) in rabbit peripheral blood. The in vitro TNF-alpha induction assay was, therefore, suggested to be an appropriate assay method for the quantitative detection of the endotoxin activity in DTaP vaccines.