Effect of hyperreactivity to endotoxin on the toxicity of pertussis vaccine and pertussis toxin in mice

In mice, greatly enhanced susceptibility to the lethal toxicity of whole-cell pertussis vaccine (PV) was produced by agents known to induce hypersusceptibility to endotoxin (LPS). The decreases in LD50 were 100-fold, 125-fold and 16-fold with galactosamine (GalN), actinomycin D (AcD) and lead acetate (PbAc) respectively and the animals died within 1-2 days. However, these decreases were less than those observed with extracted E. coli LPS, the LD50 of which was reduced approximately 500-fold, 800-fold and 50-fold respectively by these agents. In control mice, without drugs, the main lethal factor in the PV used here seemed to be pertussis toxin (PT), since deaths occurred at 3-5 days after injection, and heating the vaccine at 80 degrees C for 30 min raised the LD50 from 4 to greater than 6 single human doses (SHD) per mouse. In GalN and PbAc-treated mice, the toxicity of PV can be explained by its LPS content in view of the failure of heating at 80 degrees C to reduce toxicity. However, in AcD-treated mice, the 80 degrees C heated vaccine was threefold less toxic than the unheated material, suggesting a contribution of PT to vaccine toxicity in these animals. Indeed the toxicity of PT was increased by AcD. The possible bearing of these observations on children who appear to show serious adverse reactions to PV is discussed. Two acellular vaccines were devoid of lethal toxicity in either normal mice or in mice treated with any of the three drugs.