Fatal Pertussis in the Neonatal Mouse Model Is Associated with Pertussis Toxin-Mediated Pathology beyond the Airways

In infants, Bordetella pertussis can cause severe disease, manifested as pronounced leukocytosis, pulmonary hypertension, and even death. The exact cause of death remains unknown, and no effective therapies for treating fulminant pertussis exist. In this study, a neonatal mouse model of critical pertussis is characterized, and a central role for pertussis toxin (PT) is described. PT promoted colonization, leukocytosis, T cell phenotypic changes, systemic pathology, and death in neonatal but not adult mice. Surprisingly, PT inhibited lung inflammatory pathology in neonates, a result which contrasts dramatically with observed PT-promoted pathology in adult mice. Infection with a PT-deficient strain induced severe pulmonary inflammation but not mortality in neonatal mice, suggesting that death in these mice was not associated with impaired lung function. Dissemination of infection beyond the lungs was also detected in neonatal mice, which may contribute to the observed systemic effects of PT. We propose that it is the systemic activity of pertussis toxin and not pulmonary pathology that promotes mortality in critical pertussis. In addition, we observed transmission of infection between neonatal mice, the first report of B. pertussis transmission in mice. This model will be a valuable tool to investigate causes of pertussis pathogenesis and identify potential therapies for critical pertussis.