Abstract：
Cholesterol is a molecule vital for tick physiology, but ticks cannot synthesize it and rely on dietary cholesterol. Therefore, tick proteins involved in cholesterol absorption and transport, such as the Niemann-Pick type C1 domain-containing (NPC1) proteins, are promising targets for anti-tick vaccine development. The aim of this study was to assess the structure, function, and protective efficacy of the NPC1 orthologues identified previously in the midgut transcriptomes of argasid ticks Ornithodoros erraticus and Ornithodoros moubata. For this purpose, their corresponding cDNA coding sequences were cloned and sequenced, their secondary and 3D structures were predicted, and their function was evaluated through RNAi-mediated gene knockdown and in vitro feeding on blood supplemented with ezetimibe, which inhibits cholesterol binding by NPC1 proteins. Subsequently, the protective efficacy of a recombinant form of NPC1 from O. moubata (rOmNPC1) was tested in a rabbit vaccine trial. While inhibiting cholesterol absorption with ezetimibe resulted in up to 77 % mortality in adult O. moubata, NPC1 gene knockdown and vaccination with rOmNPC1 decreased female reproductive performance in terms of the number and fertility of laid eggs. This study presents the initial molecular and functional insights into NPC1 proteins in soft ticks and supports the hypothesis that disrupting cholesterol metabolism diminishes tick viability and reproduction, rendering Niemann-Pick type C1 domain-containing proteins promising targets for drugs or vaccines.
摘要：
胆固醇是一种对蜱生理至关重要的分子，但是壁虱不能合成它，依赖于饮食中的胆固醇。因此,蜱蛋白参与胆固醇的吸收和运输，例如Niemann-Pick型含C1结构域（NPC1）蛋白，是抗蜱疫苗开发的有希望的目标。这项研究的目的是评估结构，函数,和先前在板岩壁虱Ornithodoroserratic和Ornithodorosmoubata的中肠转录组中鉴定的NPC1直系同源物的保护效力。为此,它们相应的cDNA编码序列被克隆和测序，预测了它们的次级和3D结构，并通过RNAi介导的基因敲除和补充依泽替米贝的血液体外喂养来评估其功能，通过NPC1蛋白抑制胆固醇结合。随后，在兔疫苗试验中测试了来自O.moubata的重组形式的NPC1（rOmNPC1）的保护功效。虽然用依泽替米贝抑制胆固醇吸收导致成人O.moubata高达77%的死亡率，NPC1基因敲除和rOmNPC1疫苗接种在产卵数量和繁殖力方面降低了雌性繁殖性能。这项研究提出了对软蜱中NPC1蛋白的初步分子和功能见解，并支持破坏胆固醇代谢会降低蜱活力和繁殖的假设。提供Niemann-Pick型含C1结构域的蛋白质，有望成为药物或疫苗的靶标。
