Porter E M, van Dam E, Valore E V, Ganz T
Department of Medicine, UCLA School of Medicine, Los Angeles, California 90095, USA.
Infect Immun. 1997 Jun;65(6):2396-401. doi: 10.1128/iai.65.6.2396-2401.1997.
Defensins are antibiotic peptides expressed in human and animal myeloid and epithelial cells. Due to the limited availability of natural peptides, the properties of human epithelial defensins have not been studied. We assayed the microbicidal activity of recombinant human intestinal defensin 5 (rHD-5) in the presence of salt (O to 150 mM NaCl) with varied pH (pH 5.5 to pH 8.5) and trypsin (25 and 250 microg/ml). rHD-5 exhibits microbicidal activity against Listeria monocytogenes, Escherichia coli, and Candida albicans. In contrast to cryptdins, the mouse intestinal defensins, rHD-5 is active against both mouse-virulent wild-type Salmonella typhimurium and its isogenic, mouse-avirulent phoP mutant. In the presence of salt, rHD-5 activity was reduced, and at 100 mM NaCl, activity against S. typhimurium was abolished. However, at all salt concentrations tested, rHD-5 remained bactericidal to L. monocytogenes. Activity against L. monocytogenes was not pH dependent but was diminished at pH 5.5 against wild-type S. typhimurium. This acid-induced resistance may have been mediated by the virulence gene regulator phoP, since the phoP mutant was equally sensitive at pH 5.5 and pH 7.4. In the presence of trypsin, rHD-5 was partially cleaved, but even then, rHD-5 at 100 microg/ml decreased the number of CFU of wild-type S. typhimurium by more than 99%. The persistence of microbicidal activity of rHD-5 under these conditions supports the notion that naturally occurring human intestinal defensin is an effective arm of mucosal host defense.
防御素是在人和动物的骨髓细胞和上皮细胞中表达的抗菌肽。由于天然肽的可得性有限，人类上皮防御素的特性尚未得到研究。我们检测了重组人肠道防御素5（rHD - 5）在不同pH值（pH 5.5至pH 8.5）和不同浓度胰蛋白酶（25和250微克/毫升）以及不同盐浓度（0至150 mM NaCl）存在时的杀菌活性。rHD - 5对单核细胞增生李斯特菌、大肠杆菌和白色念珠菌具有杀菌活性。与小鼠肠道防御素隐窝蛋白不同，rHD - 5对小鼠致病性野生型鼠伤寒沙门氏菌及其同源的小鼠无毒力phoP突变体均有活性。在有盐存在的情况下，rHD - 5的活性降低，在100 mM NaCl时，对鼠伤寒沙门氏菌的活性消失。然而，在所有测试的盐浓度下，rHD - 5对单核细胞增生李斯特菌仍具有杀菌作用。对单核细胞增生李斯特菌的活性不依赖于pH值，但在pH 5.5时对野生型鼠伤寒沙门氏菌的活性减弱。这种酸诱导的抗性可能是由毒力基因调节因子phoP介导的，因为phoP突变体在pH 从5.5至pH时的敏感性相同。在有胰蛋白酶存在的情况下，rHD - 5被部分切割，但即便如此，100微克/毫升的rHD - 5仍使野生型鼠伤寒沙门氏菌的菌落形成单位数量减少了99%以上。在这些条件下rHD - 5杀菌活性的持续存在支持了这样一种观点，即天然存在的人类肠道防御素是黏膜宿主防御的有效武器。
