Inhalational anthrax disease pathogenesis and progression, from initial mucosal interactions to organ system functional genomic response

This research involves the investigation into anthrax pathogenesis from the initial exposure to lung epithelial surfaces, to the functional genomics of the initial monocyte-type or monocyte-derived cellular response, to the functional genomics of the organ level response during the first 3 days of pathogenesis. Bacillus anthracis Sterne strain was cured of the pXO1 plasmid containing the genes for lethal toxin, so that both pXO1+ and pXO1- strains could be investigated side-by-side to evaluate the role of toxin and pXO1- modulated components during anthrax pathogensis. Human epithelial monolayers generated over permeable inserts showed increased permeability in response to both pXO1- and pXO1+ strains, and soluble virulence factors such as proteases. However, no increase in permeability was observed upon challenge with lethal toxin. Additionally, monolayers containing stable monocytes showed increased permeability and bacterial invasion than with just epithelial cells alone. Monocytes challenged with both strains showed similar inflammatory transcriptional responses, while differing in key apoptotic and cell cycle responses. Induction of key mediators was also similar, but for Sterne challenged monocytes, appeared higher for the key mediators TNF-alpha and Nf-kappaB. Apoptotic pathways appear to be repressed upon challenge by toxigenic strains, compared to challenge by non-toxigenic strains. In mice, spleen, liver, and lung genomic expression was evaluated in response to pXO1+ strain challenge. Interestingly, apoptotic response is similarly suppressed in liver, while not so much in the lung and spleen. However, overall gene expression shows an initial high response in the lung, while spleen is more delayed, and liver response is greatest at day 3, when the most damage is observed histopathologically. In addition, key innate and adaptive immune modulators are up and down-regulated in certain organs but not in others. These results indicate important roles in initial immune responses at the sites of alveolar infection by monocyte-derived cells, while indicating differences in apoptotic regulation in monocytes and organ systems.