Interfering effect of diphtheria-tetanus-acellular pertussis combined (DTaP) vaccines on the bacterial endotoxin test.

We evaluated applicability of the endotoxin test to DTaP vaccines. Although no DTaP vaccine batches showed immediate interference with the activating activity of spiked endotoxin on the clotting of Limulus amaebocyte lysate (LAL), a gradually progressing interference depending on the time after spiking was seen for some of the batches. The interfering DTaP vaccine batches, however, showed no significant effect onin vitro TNF-alpha induction in RAW264.7 cells and pyrogenicity in rabbits of spiked endotoxin. Aluminium hydroxide gel in the vaccines was suggested to be one of the causes of the interference. Accordingly, a careful evaluation of the interfering effect was assumed crucial for the effective application of the endotoxin test to check residual biological activity of endotoxin in DTaP vaccines.