The effects of laboratory animal diets on the potency tests of bacterial vaccines

Comparative studies of the responses elicited by mice fed on PCD and FFG diets to a number of bacterial vaccines have shown a significant reduction in the immune response to tetanus toxoid but not to Clostridium septicum toxoid and increased resistance to challenge with E. coli and syngeneic tumour cells but not to Pasteurella multocida. These differences cannot readily be explained in terms of differences between the identifiable constituents of the diets and illustrte the dangers of vaccine potency tests that require an absolute level of response to the material under test.