Pezard C, Berche P, Mock M
Unité des Antigènes Bactériens URA 557, CNRS), Institut Pasteur, Paris, France.
Infect Immun. 1991 Oct;59(10):3472-7. doi: 10.1128/iai.59.10.3472-3477.1991.
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 LF- mutants 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.
三种蛋白质，保护性抗原（PA）、致死因子（LF）和水肿因子（EF；一种钙调蛋白依赖性腺苷酸环化酶），构成了炭疽芽孢杆菌分泌的致死毒素（PA + LF）和水肿毒素（PA + EF）。构建了每种毒素成分产生缺陷的突变菌株，然后研究它们的毒力。在每个编码EF的cya基因和编码LF的lef基因中插入卡那霉素抗性盒，并将构建体分别通过可移动穿梭质粒导入炭疽芽孢杆菌Sterne株。在与常驻毒素编码质粒pXO1进行同源重组后，分离出EF缺陷株和LF缺陷株。用这些突变体以及先前构建的PA缺陷突变体的孢子接种小鼠，并监测致死率和局部水肿形成情况。LF缺陷或PA缺陷突变体即使在高接种量下也不具有致死性，而EF缺陷突变体可引发致死性感染。这表明LF与PA结合是致死性所需的关键毒力因子。在仅产生PA和EF组合的LF缺陷突变体中观察到皮肤水肿形成。然而，EF缺陷和LF缺陷突变体在诱导致死率和水肿方面分别比亲本Sterne菌株的效率显著降低。这些结果表明，三种毒素成分可能在体内协同作用导致致死率和水肿形成。
