Targeted Silencing of Anthrax Toxin Receptors Protects against Anthrax Toxins [RNA]

April 17th, 2014 by Arevalo, M. T., Navarro, A., Arico, C. D., Li, J., Alkhatib, O., Chen, S., Diaz-Arevalo, D., Zeng, M.

Anthrax spores can be aerosolized and dispersed as a bioweapon. Current post-exposure treatments are inadequate at later stages of infection when high levels of anthrax toxins are present. Anthrax toxins enter cells via two identified anthrax toxin receptors: tumor endothelial marker 8 (TEM8) and capillary morphogenesis protein 2 (CMG2). We hypothesized that host cells would be protected from anthrax toxins if anthrax toxin receptor expression was effectively silenced using RNA interference technology (RNAi). Thus, anthrax toxin receptors in mouse and human macrophages were silenced using targeted siRNAs or blocked with specific antibody prior to challenge with anthrax lethal toxin. Viability assays were used to assess protection in macrophages treated with specific siRNA or antibody as compared to untreated cells. Silencing CMG2 using targeted siRNAs provided almost complete protection against anthrax lethal toxin-induced cytotoxicity and death in murine and human macrophages. The same results were obtained by pre-binding cells with specific antibody prior to treatment with anthrax lethal toxin. In addition, TEM8-targeted siRNAs also offered significant protection against lethal toxin in human macrophage-like cells. Furthermore, silencing CMG2, TEM8, or both receptors in combination was also protective against MEK2 cleavage by LeTx or adenylyl cyclase activity by EdTx in human kidney cells. Thus, anthrax toxin receptor-targeted RNAi has the potential to be developed as a life-saving, post-exposure therapy against anthrax.