PDF(Pubmed)
Abstract：
Endogenous antimicrobial peptides (AMPs) play a key role in the host defense against pathogens. AMPs attack pathogens preferentially at the site of entry to prevent invasive infection. Mycobacterium tuberculosis (Mtb) enters its host via the airways. AMPs released into the airways are therefore likely candidates to contribute to the clearance of Mtb immediately after infection. Since lysozyme is detectable in airway secretions, we evaluated its antimicrobial activity against Mtb. We demonstrate that lysozyme inhibits the growth of extracellular Mtb, including isoniazid-resistant strains. Lysozyme also inhibited the growth of non-tuberculous mycobacteria. Even though lysozyme entered Mtb-infected human macrophages and co-localized with the pathogen we did not observe antimicrobial activity. This observation was unlikely related to the large size of lysozyme (14.74 kDa) because a smaller lysozyme-derived peptide also co-localized with Mtb without affecting the viability. To evaluate whether the activity of lysozyme against extracellular Mtb could be relevant in vivo, we incubated Mtb with fractions of human serum and screened for antimicrobial activity. After several rounds of sub-fractionation, we identified a highly active fraction-component as lysozyme by mass spectrometry. In summary, our results identify lysozyme as an antimycobacterial protein that is detectable as an active compound in human serum. Our results demonstrate that the activity of AMPs against extracellular bacilli does not predict efficacy against intracellular pathogens despite co-localization within the macrophage. Ongoing experiments are designed to unravel peptide modifications that occur in the intracellular space and interfere with the deleterious activity of lysozyme in the extracellular environment.
摘要：
内源性抗菌肽（AMP）在宿主对病原体的防御中起着关键作用。AMP优先在进入部位攻击病原体以防止侵入性感染。结核分枝杆菌(Mtb)通过气道进入其宿主。因此释放到气道中的AMP很可能是在感染后立即清除Mtb的候选者。由于溶菌酶在气道分泌物中可以检测到，我们评估了其对Mtb的抗菌活性。我们证明溶菌酶抑制细胞外Mtb的生长，包括异烟肼抗性菌株。溶菌酶还抑制非结核分枝杆菌的生长。即使溶菌酶进入Mtb感染的人巨噬细胞并与病原体共定位，我们也没有观察到抗菌活性。该观察结果不太可能与大尺寸的溶菌酶(14.74kDa)相关,因为较小的溶菌酶衍生肽也与Mtb共定位而不影响生存力。为了评估溶菌酶抗细胞外Mtb的活性是否在体内相关，我们将Mtb与人血清级分孵育，并筛选抗菌活性。经过几轮细分，我们通过质谱鉴定了一种高活性组分为溶菌酶。总之,我们的研究结果将溶菌酶鉴定为一种在人血清中可检测为活性化合物的抗分枝杆菌蛋白.我们的结果表明，尽管在巨噬细胞内共定位，但针对细胞外杆菌的AMP活性并不能预测针对细胞内病原体的功效。正在进行的实验旨在解开发生在细胞内空间中并干扰溶菌酶在细胞外环境中的有害活性的肽修饰。
