Department of Pediatrics, University of California San Diego, La Jolla, CA 92093-0687, USA.
J Innate Immun. 2009;1(5):494-506. doi: 10.1159/000225955. Epub 2009 Jun 18.
Bacillus anthracis is a National Institute of Allergy and Infectious Diseases Category A priority pathogen and the causative agent of the deadly disease anthrax. We applied a transposon mutagenesis system to screen for novel chromosomally encoded B. anthracis virulence factors. This approach identified ClpX, the regulatory ATPase subunit of the ClpXP protease, as essential for both the hemolytic and proteolytic phenotypes surrounding colonies of B. anthracis grown on blood or casein agar media, respectively. Deletion of clpX attenuated lethality of B. anthracis Sterne in murine subcutaneous and inhalation infection models, and markedly reduced in vivo survival of the fully virulent B. anthracis Ames upon intraperitoneal challenge in guinea pigs. The extracellular proteolytic activity dependent upon ClpX function was linked to degradation of cathelicidin antimicrobial peptides, a front-line effector of innate host defense. B. anthracis lacking ClpX were rapidly killed by cathelicidin and alpha-defensin antimicrobial peptides and lysozyme in vitro. In turn, mice lacking cathelicidin proved hyper-susceptible to lethal infection with wild-type B. anthracis Sterne, confirming cathelicidin to be a critical element of innate defense against the pathogen. We conclude that ClpX is an important factor allowing B. anthracis to subvert host immune clearance mechanisms, and thus represents a novel therapeutic target for prevention or therapy of anthrax, a foremost biodefense concern.
炭疽芽孢杆菌是美国国立过敏和传染病研究所 A 类优先病原体，也是致命疾病炭疽的病原体。我们应用转座子诱变系统筛选新型染色体编码的炭疽杆菌毒力因子。这种方法确定了 ClpX，即 ClpXP 蛋白酶的调节 ATP 酶亚基，分别是血液或酪蛋白琼脂培养基上生长的炭疽杆菌菌落周围溶血和蛋白水解表型所必需的。clpX 的缺失削弱了炭疽杆菌 Sterne 在小鼠皮下和吸入感染模型中的致死性，并且在豚鼠的腹腔内挑战中，完全毒力的炭疽杆菌 Ames 的体内存活率显著降低。依赖于 ClpX 功能的细胞外蛋白水解活性与抗菌肽 cathelicidin 的降解有关，这是先天宿主防御的一线效应因子。缺乏 ClpX 的炭疽杆菌在体外会迅速被抗菌肽 cathelicidin 和 alpha-防御素以及溶菌酶杀死。反过来，缺乏抗菌肽 cathelicidin 的小鼠对野生型炭疽杆菌 Sterne 的致死性感染表现出高度易感性，证实抗菌肽 cathelicidin 是抵抗病原体的先天防御的关键因素。我们得出结论，ClpX 是炭疽杆菌颠覆宿主免疫清除机制的重要因素，因此代表了预防或治疗炭疽的新的治疗靶点，炭疽是首要的生物防御关注点。
