University of South Bohemia, Faculty of Science, České Buděovice, Czech Republic.
Parasit Vectors. 2011 Apr 19;4:63. doi: 10.1186/1756-3305-4-63.
The immune system of ticks is stimulated to produce many pharmacologically active molecules during feeding and especially during pathogen invasion. The family of cationic peptides - defensins - represents a specific group of antimicrobial compounds with six conserved cysteine residues in a molecule.
Two isoforms of the defensin gene (def1 and def2) were identified in the European tick Ixodes ricinus. Expression of both genes was induced in different tick organs by a blood feeding or pathogen injection. We have tested the ability of synthetic peptides def1 and def2 to inhibit the growth or directly kill several pathogens. The antimicrobial activities (expressed as minimal inhibition concentration and minimal bactericidal concentration values) against Gram positive bacteria were confirmed, while Gram negative bacteria, yeast, Tick Borne Encephalitis and West Nile Viruses were shown to be insensitive. In addition to antimicrobial activities, the hemolysis effect of def1 and def2 on human erythrocytes was also established.
Although there is nothing known about the realistic concentration of defensins in I. ricinus tick body, these results suggest that defensins play an important role in defence against different pathogens. Moreover this is a first report of a one amino acid substitution in a defensins molecule and its impact on antimicrobial activity.
在进食过程中，尤其是在病原体入侵时，蜱的免疫系统会受到刺激，产生许多具有药理活性的分子。阳离子肽家族 - 防御素 - 是一类具有分子中六个保守半胱氨酸残基的特定抗菌化合物。
在欧洲蜱 Ixodes ricinus 中鉴定出防御素基因（def1 和 def2）的两种同工型。通过血液摄取或病原体注射，两种基因在不同的蜱器官中均被诱导表达。我们已经测试了合成肽 def1 和 def2 抑制几种病原体生长或直接杀死它们的能力。对革兰氏阳性菌的抗菌活性（以最小抑制浓度和最小杀菌浓度值表示）得到了证实，而革兰氏阴性菌、酵母、蜱传脑炎病毒和西尼罗河病毒则显示出不敏感。除了抗菌活性外，还确定了 def1 和 def2 对人红细胞的溶血作用。
尽管尚不清楚防御素在 I. ricinus 蜱体中的实际浓度，但这些结果表明防御素在防御各种病原体方面发挥着重要作用。此外，这是首次报道防御素分子中的一个氨基酸取代及其对抗菌活性的影响。
