Allergic encephalomyelitis in rats - toxicity assay for pertussis vaccines.

Levine produced encephalitis in Lewis rats after injection of pertussis vaccine together with spinal cord tissue of guinea-pigs. This animal model was used as an assay for the possible side-effects of pertussis vaccines prepared from whole bacteria or with extracted antigens. Wistar and Lewis rats were injected with a mixture of guinea-pig spinal cord and cFA together with vaccines into the pad of each hind food. During a period of 25 days, the rats were observed for paralysis, ataxia, and death. Wistar rats were not found to be sensitive enough. Lewis rats were high susceptible in this model; they developed a high rate of allergic encephalopathy. DPT-vaccines prepared with soluble antigens showed a reduced neurotoxic activity. The results were compared with the histamine-sensitizing assay and the mouse weight-gain test. In these assays similar results were found. The proposed animal assay is recommended in the preclinical testing of pertussis vaccines.