Contribution of individual toxin components to virulence of Bacillus anthracis

Abstract

Three proteins, protective antigen (PA), lethal factor (LF), and edema factor (EF; a calmodulin-dependent adenylate cyclase), compose the lethal (PA+LF) and edema (PA+EF) toxins secreted by Bacillus anthracis. Mutant strains, each deficient in the production of one toxin component, were constructed, and their virulence was then studied. A kanamycin resistance cassette was inserted in each cya (encoding EF) and lef(encoding LF) gene, and the constructs were separately introduced into B. anthracis Sterne on a mobilizable shuttle plasmid. An EF-strain and an LF-strain were then isolated after homologous recombination with the resident toxin-encoding plasmid, pXO1. Spores from these mutants and from a previously constructed PA-mutant were used to inoculate mice, and the lethality and local edema formation were monitored. LF-or PA-mutants were not lethal even at high inocula, whereas the EF-mutant induced lethal infections. This indicates that LF in combination with PA is a key virulence factor required for lethality. Skin edema formation was observed with the LF-mutant, which produces only the combination of PA and EF. However, EF-and LFmutants were significantly less efficient at inducing, respectively, lethality and edema than was the parental Sterne strain. These results suggest that the three toxin components might act synergistically in vivo to cause lethality and edema formation.

The biological role of the enigmatic C3larvinAB toxin of the honey bee pathogenic bacterium Paenibacillus larvae

“…4A, region highlighted in magenta). This domain is usually characteristic for the B subunits of binary AB toxins, like C. botulinum C2 toxin component-II (Kimura et al, 1998), C. difficile binary toxin B (cdtB) (Stubbs et al, 2000), C. perfringens iota toxin (Perelle et al, 1993), and B. anthracis anthrax toxin PA component (Welkos et al, 1988;Pezard et al, 1991), but it has also been identified in Plx2B (Fünfhaus et al, 2013), the B subunit belonging to the C3-like toxin Plx2A of P. larvae ERIC I (Fünfhaus et al, 2013;Ebeling et al, 2017). In addition, we detected a 124-residue carbohydrate binding domain of the CBM_4_9 superfamily (acc.…”

Contribution of toxins to the pathogenesis of inhalational anthrax

“…Intradermal injections of PA + EF (or oedema toxin, ET) induce oedema in the skin (Stanley and Smith, 1961), and may also be lethal. The role of toxins in strain virulence in vivo has been demonstrated by gene deletion, showing a synergic effect of EF and LF (Pezard et al, 1991). Crystal structures have been obtained for all three components of these toxins (Petosa et al, 1997;Pannifer et al, 2001;Drum et al, 2002).…”

Transcriptome dysregulation by anthrax lethal toxin plays a key role in induction of human endothelial cell cytotoxicity

“…EF produces an increase in the intracellular level of cyclic-AMP through its calcium/calmodulin-dependent adenylate cyclase activity (Moayeri and Leppla, 2004). Deletion of EF or LF leads to a 10-and 1000-fold attenuation of bacterial virulence respectively (Pezard et al, 1991).…”