Bacillus anthracis spore-host interactions

by Swiecki, Melissa K.

The use of Bacillus anthracis as a bioweapon depends on the dispersal of its spores into the environment, entrance into the body, spore uptake by human host cells, germination of the spores in the host and the pathological consequences of the virulence factors produced by the vegetative cells. Prior to 2001, very little was known about the mechanisms of spore entry into the host, including targeting cell types at airway, digestive and skin surfaces, potential spore receptors on these cells and spore encounters with cellular and humoral elements of the innate and adaptive immune systems. To this end, we have developed and characterized multiple antibodies that recognize B. anthracis spores, specifically the exosporium. These mAbs have proved to be valuable tools in analyzing the structure and function of this outermost layer of the spore. We have also identified Mac-1 and CD14 as receptors on professional phagocytes that bind to the immunodominant exosporium collagenlike glycoprotein BclA and facilitate spore uptake. Although remarkable strides have been made to understand the exosporium and its role in virulence during these past few years, much remains to be learned about spore-host interactions and ways to improve current vaccine and therapeutic strategies. ii