Bordetella evolution: lipid A and Toll-like receptor 4

The evolution of Bordetella pertussis and Bordetella parapertussis from Bordetella bronchiseptica involved changes in host range and pathogenicity. Recent data suggest that the human-adapted Bordetella modified their interaction with host immune systems to effect these changes and that decreased stimulation of Toll-like receptor 4 (TLR4) by lipid A is central to this. We discuss Bordetella lipid A structure and genetics within the context of evolution and host immunity.