Toxins Secreted by Bacillus Anthracis

Edema Toxin (EdTx) and Lethal Toxin (LeTx) are two toxins with immunomodulatory activity that are produced by A anthracis, the cause of the disease anthrax. Both toxins are composed of a heptameric complex of protective antigen (PA) bound to either edema factor (EF) or lethal factor (LF). The heptameric complex of PA is responsible for receptor binding and cellular entry, whereas toxicity is associated with both EF, a calmodulin-dependent adenylate cyclase that induces increases in cytosolic cAMP and LF, a metalloprotease that cleaves mitogen-activated protein kinase kinases (MAPKK).  

Many studies have shown that LeTx harbours a potent immunomodulatory capacity. LeTx induces apoptosis of murine macrophages and human monocytes however, they may need to be activated before this occurs. Additionally, LeTx inhibits chemotaxis and the expression of pro-inflammatory cytokines and chemokines in stimulated macrophages, by preventing nuclear factor (NF)-kB and interferon regulatory factor (IRF)-3 activation, and diminishes their T-cell 

Pathogen-Derived Immunomodulatory Molecules, edited by Padraic G. Fallon. 

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