Demyelination Lesions Do Not Correlate with Clinical Manifestations by Bordetella pertussis Toxin Concentrations

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system, characterized as an inflammatory demyelinating disease. Given the need for improvements in MS treatment, many studies are mainly conducted through preclinical models such as experimental allergic encephalomyelitis (EAE). This study analyzes the relationships between histopathological and clinical score findings at EAE. Twenty-three female Rattus norvegicus Lewis rats from 6 to 8 weeks were induced to EAE. Nineteen rats underwent EAE induction distributed in six groups to establish the evolution of clinical signs, and four animals were in the control group. Bordetella pertussis toxin (PTX) doses were 200, 250, 300, 350 and 400 ng. The clinical scores of the animals were analyzed daily, from seven to 24 days after induction. The brains and spinal cords were collected for histopathological analyses. The results demonstrated that the dose of 250 ng of PTX induced a higher clinical score and reduction in weight. All induced groups demonstrated leukocyte infiltration, activation of microglia and astrocytes, and demyelinated plaques in the brains in histopathology. It was concluded that the dose of 250 ng and 350 ng of PTX were the best choices to trigger the brain and spinal cord demyelination lesions and did not correlate with clinical scores.