Mosser Elise M, Rest Richard F
Department of Microbiology and Immunology, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, USA.
BMC Microbiol. 2006 Jun 21;6:56. doi: 10.1186/1471-2180-6-56.
Bacillus anthracis is an animal and human pathogen whose virulence is characterized by lethal and edema toxin, as well as a poly-glutamic acid capsule. In addition to these well characterized toxins, B. anthracis secretes several proteases and phospholipases, and a newly described toxin of the cholesterol-dependent cytolysin (CDC) family, Anthrolysin O (ALO).
In the present studies we show that recombinant ALO (rALO) or native ALO, secreted by viable B. anthracis, is lethal to human primary polymorphonuclear leukocytes (PMNs), monocytes, monocyte-derived macrophages (MDMs), lymphocytes, THP-1 monocytic human cell line and ME-180, Detroit 562, and A549 epithelial cells by trypan blue exclusion or lactate dehydrogenase (LDH) release viability assays. ALO cytotoxicity is dose and time dependent and susceptibility to ALO-mediated lysis differs between cell types. In addition, the viability of monocytes and hMDMs was assayed in the presence of vegetative Sterne strains 7702 (ALO+), UT231 (ALO-), and a complemented strain expressing ALO, UT231 (pUTE544), and was dependent upon the expression of ALO. Cytotoxicity of rALO is seen as low as 0.070 nM in the absence of serum. All direct cytotoxic activity is inhibited by the addition of cholesterol or serum concentration as low as 10%.
The lethality of rALO and native ALO on human monocytes, neutrophils, macrophages and lymphocytes supports the idea that ALO may represent a previously unidentified virulence factor of B. anthracis. The study of other factors produced by B. anthracis, along with the major anthrax toxins, will lead to a better understanding of this bacterium's pathogenesis, as well as provide information for the development of antitoxin vaccines for treating and preventing anthrax.
炭疽芽孢杆菌是一种人畜共患病原体，其毒力特征表现为致死毒素、水肿毒素以及聚谷氨酸荚膜。除了这些特征明确的毒素外，炭疽芽孢杆菌还分泌多种蛋白酶和磷脂酶，以及一种新发现的属于胆固醇依赖性细胞溶素（CDC）家族的毒素——炭疽溶血素O（ALO）。
在本研究中，我们发现重组ALO（rALO）或由活的炭疽芽孢杆菌分泌的天然ALO，通过台盼蓝排斥试验或乳酸脱氢酶（LDH）释放活力测定法，对人原代多形核白细胞（PMN）、单核细胞、单核细胞衍生的巨噬细胞（MDM）、淋巴细胞、THP-1单核细胞人细胞系以及ME-180、底特律562和A549上皮细胞具有致死性。ALO的细胞毒性具有剂量和时间依赖性，并且不同细胞类型对ALO介导的裂解的敏感性不同。此外，在营养型Sterne菌株7702（ALO+）、UT231（ALO-）以及表达ALO的互补菌株UT231（pUTE544）存在的情况下，测定了单核细胞和人MDM的活力，其活力取决于ALO的表达。在无血清条件下，rALO的细胞毒性低至0.070 nM时即可观察到。添加胆固醇或低至10%的血清浓度可抑制所有直接细胞毒性活性。
rALO和天然ALO对人单核细胞、中性粒细胞、巨噬细胞和淋巴细胞的致死性支持了ALO可能是炭疽芽孢杆菌一种先前未被识别的毒力因子的观点。对炭疽芽孢杆菌产生的其他因子以及主要炭疽毒素的研究，将有助于更好地理解该细菌的发病机制，并为开发用于治疗和预防炭疽的抗毒素疫苗提供信息。
