Ticks are hematophagous ectoparasites and cause a major public health threat worldwide. Development of anti-tick vaccines is regarded to be an optimal alternative for tick control. AV422, a unique protein in ticks, is secreted into hosts during blood-feeding, but its roles are not confirmed in Haemaphysalis flava ticks. We retrieved a gene fragment encoding AV422 from a transcriptome dataset of H. flava, and based on it, we reconstructed the full length of AV422 from H. flava (Hf-AV422) by rapid amplification of cDNA ends. Expression profiles of Hf-AV422 in whole ticks and organs of different engorgement levels were determined by qPCR. Then its opening reading frame (ORF) was expressed in Escherichia coli strain BL21 (DE3). The prothrombin time (PT), activated partial thromboplastin time (APTT) and thrombin time (TT) assays were conducted to test anticoagulant activities of the purified recombinant protein (rHf-AV422). The full length of AV422 was 1152 bp. Hf-AV422 showed to be conserved as indicated by multiple sequence alignment. Expression of Hf-AV422 was significantly higher in salivary glands and cuticles than in ovaries. Its expression in whole ticks decreased during engorgement with the highest levels in 1/4 engorged ticks. rHf-AV422 prolonged PT, APTT and TT when incubated with rabbit plasma. Our data demonstrated that Hf-AV422 is a conserved salivary protein with anticoagulant activity. Further studies are needed to test in detail its functional properties to ensure it an adequate antigen candidate for the development of broad-spectrum vaccines against ticks.

蜱虫是一种吸血性外寄生虫，对全世界的公共卫生构成重大威胁。开发抗蜱疫苗被认为是控制蜱的最佳选择。AV422 是蜱中一种独特的蛋白质，在吸血过程中分泌到宿主中，但其作用尚未在黄血蜱中得到证实。我们从H. flava的转录组数据集中检索了编码 AV422 的基因片段，并在此基础上，我们通过 cDNA 末端的快速扩增从H. flava ( Hf-AV422 )重建了 AV422 的全长。通过qPCR确定Hf-AV422在不同充血水平的整个蜱和器官中的表达谱。然后它的开放阅读框（ORF）表达为大肠杆菌菌株 BL21 (DE3)。进行凝血酶原时间 (PT)、活化部分凝血活酶时间 (APTT) 和凝血酶时间 (TT) 测定以测试纯化重组蛋白 (rHf-AV422) 的抗凝活性。AV422 的全长为 1152 bp。多序列比对表明 Hf-AV422 是保守的。Hf-AV422的表达唾液腺和角质层中的显着高于卵巢。它在整个蜱中的表达在充血期间降低，在 1/4 充血的蜱中表达水平最高。当与兔血浆一起孵育时，rHf-AV422 延长了 PT、APTT 和 TT。我们的数据表明 Hf-AV422 是一种具有抗凝活性的保守唾液蛋白。需要进一步的研究来详细测试其功能特性，以确保它是开发针对蜱的广谱疫苗的足够抗原候选物。