Bacillus anthracis’ lethal toxin induces broad transcriptional responses in human peripheral monocytes

Abstract

BackgroundAnthrax lethal toxin (LT), produced by the Gram-positive bacterium Bacillus anthracis, is a highly effective zinc dependent metalloprotease that cleaves the N-terminus of mitogen-activated protein kinase kinases (MAPKK or MEKs) and is known to play a role in impairing the host immune system during an inhalation anthrax infection. Here, we present the transcriptional responses of LT treated human monocytes in order to further elucidate the mechanisms of LT inhibition on the host immune system.ResultsWestern Blot analysis demonstrated cleavage of endogenous MEK1 and MEK3 when human monocytes were treated with 500 ng/mL LT for four hours, proving their susceptibility to anthrax lethal toxin. Furthermore, staining with annexin V and propidium iodide revealed that LT treatment did not induce human peripheral monocyte apoptosis or necrosis. Using Affymetrix Human Genome U133 Plus 2.0 Arrays, we identified over 820 probe sets differentially regulated after LT treatment at the p <0.001 significance level, interrupting the normal transduction of over 60 known pathways. As expected, the MAPKK signaling pathway was most drastically affected by LT, but numerous genes outside the well-recognized pathways were also influenced by LT including the IL-18 signaling pathway, Toll-like receptor pathway and the IFN alpha signaling pathway. Multiple genes involved in actin regulation, signal transduction, transcriptional regulation and cytokine signaling were identified after treatment with anthrax LT.ConclusionWe conclude LT directly targets human peripheral monocytes and causes multiple aberrant gene responses that would be expected to be associated with defects in human monocyte’s normal signaling transduction pathways and function. This study provides further insights into the mechanisms associated with the host immune system collapse during an anthrax infection, and suggests that anthrax LT may have additional downstream targets outside the well-known MAPK pathway.

Genomic Copy Number Variants: Evidence for Association with Antibody Response to Anthrax Vaccine Adsorbed

“…NSF gene has been associated with Parkinson’s disease [39]. In one study ARL17 , ADP-ribosylation factor-like 17 was one of the genes reported to be differentially regulated in the human monocytes after treatment with anthrax lethal toxin (LT) [40]. ARL17 is localized to the Golgi apparatus and is thought to be involved in modulation of vesicle budding and is known to be an activator of cholera toxin catalytic subunit, an ADP-ribosyltransferase [41].…”

A Biologically-Based Computational Approach to Drug Repurposing for Anthrax Infection

“…For each dataset, we used the differentially expressed genes published by authors (HAM-LT-ET by Dozmorov et al [79] and PBMC exposed to LT by Chauncey et al [80]) and reported in the GEO (Gene Expression Omnibus; ).…”

The Impact of “Omic” and Imaging Technologies on Assessing the Host Immune Response to Biodefence Agents

“…This information has largely been obtained from in vitro infection experiments. Primary cells taken from naïve human volunteers [8][9][10][11][12][13][14][15] or continuous cell lines [16][17][18][19][20][21][22] have been infected and incubated with a pathogen for different time periods (ranging from 1 to 48 hours) and host gene signatures generated ( Table 1). Microarray studies performed in this way provide insights into the cellular response following infection with, for instance, Monkeypox virus.…”

“…DNA microarray analysis has been used to improve our understanding of the host response following exposure to the bacterium [18], spores [9], edema toxin [17], and lethal toxin [8] of Bacillus anthracis, the causative agent of anthrax. Studies on human peripheral monocytes revealed that anthrax lethal toxin targets multiple normal immuneregulatory pathways that would be expected to protect the host against anthrax infection.…”

“…Studies on human peripheral monocytes revealed that anthrax lethal toxin targets multiple normal immuneregulatory pathways that would be expected to protect the host against anthrax infection. They hypothesised that the increase in RGS14 levels and decrease in CCR5, along with IL-1R2, impairs monocyte function and facilitates bacterial survival [8].…”