How whooping cough evades the immune system to infect vaccinated hosts

Since the 1950s, young children in industrialized countries have been vaccinated against Bordetella pertussis, one of the principal bacteria that causes whooping cough.

However, recent surveys indicate that many vaccinated people nevertheless become infected with B. pertussis and develop a mild form of the disease that often goes undiagnosed. Such carriers poses a significant risk to unvaccinated children, who can develop much more severe symptoms.

In the December 2005 issue of The Journal of Clinical Investigation, Eric Harvill and coworkers demonstrate how B. pertussis manages to evade the immune system to infect vaccinated individuals.

They discovered that in mice, a toxin produced by B. pertussis inhibits recruitment of neutrophil cells (which engulf and lyse the bacteria) to the site of infection, thus giving the bacteria time to spread through the lungs. This occurs even in individuals that have encountered the bacteria before, enabling the disease to persist in vaccinated populations.

These findings suggest that for vaccination against whooping cough to be effective, it needs to generate a long-lasting antibody response to pertussis toxin, not just to proteins on the bacterial cell surface.