Wei Zhengyu, Schnupf Pamela, Poussin Mathilde A, Zenewicz Lauren A, Shen Hao, Goldfine Howard
Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, 19104-6076, USA.
Infect Immun. 2005 Oct;73(10):6639-46. doi: 10.1128/IAI.73.10.6639-6646.2005.
Two virulence factors of Listeria monocytogenes, listeriolysin O (LLO) and phosphatidylinositol-specific phospholipase C (PI-PLC), mediate escape of this pathogen from the phagocytic vacuole of macrophages, thereby allowing the bacterium access to the host cell cytosol for growth and spread to neighboring cells. We characterized their orthologs from Bacillus anthracis by expressing them in L. monocytogenes and characterizing their contribution to bacterial intracellular growth and cell-to-cell spread. We generated a series of L. monocytogenes strains expressing B. anthracis anthrolysin O (ALO) and PI-PLC in place of LLO and L. monocytogenes PI-PLC, respectively. We found that ALO was active at both acidic and neutral pH and could functionally replace LLO in mediating escape from a primary vacuole; however, ALO exerted a toxic effect on the host cell by damaging the plasma membrane. B. anthracis PI-PLC, unlike the L. monocytogenes ortholog, had high activity on glycosylphosphatidylinositol-anchored proteins. L. monocytogenes expressing B. anthracis PI-PLC showed significantly decreased efficiencies of escape from a phagosome and in cell-to-cell spread. We further compared the level of cytotoxicity to host cells by using mutant strains expressing ALO in combination either with L. monocytogenes PI-PLC or with B. anthracis PI-PLC. The results demonstrated that the mutant strain expressing the combination of ALO and B. anthracis PI-PLC caused less damage to host cells than the strain expressing ALO and L. monocytogenes PI-PLC. The present study indicates that LLO and L. monocytogenes PI-PLC has adapted for L. monocytogenes intracellular growth and virulence and suggests that ALO and B. anthracis PI-PLC may have a role in B. anthracis pathogenesis.
单核细胞增生李斯特菌的两种毒力因子，李斯特菌溶血素O（LLO）和磷脂酰肌醇特异性磷脂酶C（PI-PLC），介导该病原体从巨噬细胞的吞噬泡中逃逸，从而使细菌能够进入宿主细胞胞质溶胶进行生长并扩散到邻近细胞。我们通过在单核细胞增生李斯特菌中表达炭疽芽孢杆菌的同源物并表征它们对细菌细胞内生长和细胞间传播的贡献，对其进行了表征。我们分别构建了一系列单核细胞增生李斯特菌菌株，这些菌株表达炭疽芽孢杆菌溶血素O（ALO）和PI-PLC，以替代LLO和单核细胞增生李斯特菌PI-PLC。我们发现ALO在酸性和中性pH下均有活性，并且在介导从初级液泡中逃逸方面可以功能性替代LLO；然而，ALO通过损伤质膜对宿主细胞产生毒性作用。与单核细胞增生李斯特菌同源物不同，炭疽芽孢杆菌PI-PLC对糖基磷脂酰肌醇锚定蛋白具有高活性。表达炭疽芽孢杆菌PI-PLC的单核细胞增生李斯特菌从吞噬体逃逸和细胞间传播的效率显著降低。我们进一步使用表达ALO的突变菌株与单核细胞增生李斯特菌PI-PLC或炭疽芽孢杆菌PI-PLC组合，比较了对宿主细胞的细胞毒性水平。结果表明，表达ALO和炭疽芽孢杆菌PI-PLC组合的突变菌株对宿主细胞造成的损伤小于表达ALO和单核细胞增生李斯特菌PI-PLC的菌株。本研究表明，LLO和单核细胞增生李斯特菌PI-PLC已适应单核细胞增生李斯特菌的细胞内生长和毒力，并表明ALO和炭疽芽孢杆菌PI-PLC可能在炭疽芽孢杆菌的致病过程中起作用。
