UMR BIPAR, INRA, ANSES, Ecole Nationale Vétérinaire d'Alfort, Université Paris-Est, Maisons-Alfort, 94700, France.
Institute for Insect Biotechnology, Justus Liebig University of Giessen, Heinrich-Buff-Ring 26-32, 35392, Giessen, Germany; LOEWE Centre for Translational Biodiversity Genomics (LOEWE-TBG), Senckenberganlage 25, 60325, Frankfurt, Germany.
Ticks Tick Borne Dis. 2019 Oct;10(6):101269. doi: 10.1016/j.ttbdis.2019.101269. Epub 2019 Aug 16.
Tick innate immunity involves humoral and cellular responses. Among the humoral effector molecules in ticks are the defensins which are a family of small peptides with a conserved γ-core motif that is crucial for their antimicrobial activity. Defensin families have been identified in several hard and soft tick species. However, little is known about the presence and antimicrobial activity of defensins from the Australian paralysis tick Ixodes holocyclus. In this study the I. holocyclus transcriptome was searched for the presence of defensins. Unique and non-redundant defensin sequences were identified and designated as holosins 1 - 5. The antimicrobial activity of holosins 2 and 3 and of the predicted γ-cores of holosins 1-4 (HoloTickCores 1-4), was assessed using Gram-negative and Gram-positive bacteria as well as the fungus Fusarium graminearum and the yeast Candida albicans. All holosins had molecular features that are conserved in other tick defensins. Furthermore holosins 2 and 3 were very active against the Gram-positive bacteria Staphylococcus aureus and Listeria grayi. Holosins 2 and 3 were also active against F. graminearum and C. albicans and 5 μM of peptide abrogate the growth of these microorganisms. The activity of the synthetic γ-cores was lower than that of the mature defensins apart from HoloTickCore 2 which had activity comparable to mature holosin 2 against the Gram-negative bacterium Escherichia coli. This study reveals the presence of a multigene defensin family in I. holocyclus with wide antimicrobial activity.
蜱固有免疫涉及体液和细胞反应。在蜱的体液效应分子中，防御素是一类具有保守γ-核心基序的小肽，对其抗菌活性至关重要。已经在几种硬蜱和软蜱物种中鉴定出防御素家族。然而，关于澳大利亚麻痹蜱 Ixodes holocyclus 防御素的存在和抗菌活性知之甚少。在这项研究中，搜索了 I. holocyclus 转录组中防御素的存在情况。鉴定出独特且非冗余的防御素序列，并将其命名为 holosins 1-5。评估了 holosins 2 和 3 以及 holosins 1-4 的预测γ-核心（HoloTickCores 1-4）的抗菌活性，使用革兰氏阴性和革兰氏阳性细菌以及真菌禾谷镰刀菌和酵母白色念珠菌进行了评估。所有 holosins 都具有在其他蜱防御素中保守的分子特征。此外，holosins 2 和 3 对革兰氏阳性菌金黄色葡萄球菌和 Listeria grayi 非常有效。holosins 2 和 3 对禾谷镰刀菌和白色念珠菌也有效，5 μM 的肽可阻止这些微生物的生长。除了 HoloTickCore 2 外，合成的γ-核心的活性低于成熟防御素，HoloTickCore 2 对革兰氏阴性菌大肠杆菌的活性与成熟 holosin 2 相当。这项研究揭示了 I. holocyclus 中存在具有广泛抗菌活性的多基因防御素家族。
