Increased levels of active pertussis toxin may aid a pertussis vaccine to pass the mouse body weight gain test.

The mouse weight gain test was evaluated for its value in toxicity testing for pertussis vaccines. When the reference whole cell pertussis vaccine was tested at dilutions of 1 in 1 and 1 in 16, the mice which received the 1 in 1 dilution achieved the greatest weight gain by the seventh day of injection, although they experienced a more significant weight loss during the first 24 hours than both the normal control mice or those that received the 1 in 16 dilution. A commercial diphtheria-tetanus-acellular pertussis vaccine with an increased level of pertussis toxin activity significantly accelerated the weight gain of mice. The effect was lost by heating the vaccine at 80 degrees C for 2 hours. A 1 micrograms dose of endotoxin induced a significant weight loss in mice during the first 24 hours of injection followed by weight gain at the same rate as that of the normal control. Pertussis toxin accelerated the weight gain of mice at a dose of 2 micrograms to a level exceeding that of the normal control mice throughout the observation period of 11 days. Pertussis toxin, when inoculated with endotoxin, showed a marked effect of helping mice to recover quickly from the endotoxin-induced initial weight loss to the level of those receiving only pertussis toxin. The effect of pertussis toxin on the acceleration of the weight gain of mice showed the possibility of inappropriate interpretation of the test results. It suggests, therefore, the necessity for separate quantitative tests for controlling the vaccine's toxicities.