Quantitative Priming with Inactivated Pertussis Toxoid Vaccine in the Aerosol Challenge Model

Abstract
Serum antibodies to pertussis toxin (PT) have been shown to be protective against severe pertussis disease, although a specific level of anti-PT antibody that correlates with protection has not been demonstrated. Current animal models such as the intracerebral challenge model have significant limitations in correlating protection to a specific level of anti-PT antibody. This study examines the protective effects of priming with tetranitromethane-inactivated pertussis toxoid (PTx) vaccine in the aerosol challenge model and whether a measurable response to a priming dose of PTx is enough to initiate a protective secondary response when challenged with infection. The correlation of priming with markers of illness such as leukocytosis, weight loss, bacterial proliferation, and mortality after established infection with Bordetella pertussis was explored. BALB/c mice were immunized with PTx vaccine on day 6 of life and then challenged with B. pertussis using the aerosol challenge model. Data were analyzed according to the primary immunologic response, differentiating responders (anti-PT immunoglobulin G [IgG] ≥1 μg/ml) from nonresponders (anti-PT IgG B. pertussis in the lungs following aerosol challenge than the nonprimed group. This protection correlated with levels of anti-PT antibody in serum present on the day of aerosol challenge.

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