Parasitología Animal, Instituto de Recursos Naturales y Agrobiología de Salamanca (IRNASA, CSIC), Cordel de Merinas, 40-52, 37008, Salamanca, Spain.
Biotechvana, Scientific Park, University of Valencia, Calle Catedrático José Beltrán 2, Paterna, 46980, Valencia, Spain.
Parasit Vectors. 2021 Mar 20;14(1):170. doi: 10.1186/s13071-021-04671-z.
The argasid tick Ornithodoros erraticus is the main vector of tick-borne human relapsing fever (TBRF) and African swine fever (ASF) in the Mediterranean Basin. Tick salivary proteins secreted to the host at the feeding interface play critical roles for tick feeding and may contribute to host infection by tick-borne pathogens; accordingly, these proteins represent interesting antigen targets for the development of vaccines aimed at the control and prevention of tick infestations and tick-borne diseases.
To identify these proteins, the transcriptome of the salivary glands of O. erraticus was de novo assembled and the salivary gene expression dynamics assessed throughout the trophogonic cycle using Illumina sequencing. The genes differentially upregulated after feeding were selected and discussed as potential antigen candidates for tick vaccines.
Transcriptome assembly resulted in 22,007 transcripts and 18,961 annotated transcripts, which represent 86.15% of annotation success. Most salivary gene expression took place during the first 7 days after feeding (2088 upregulated transcripts), while only a few genes (122 upregulated transcripts) were differentially expressed from day 7 post-feeding onwards. The protein families more abundantly overrepresented after feeding were lipocalins, acid and basic tail proteins, proteases (particularly metalloproteases), protease inhibitors, secreted phospholipases A2, 5'-nucleotidases/apyrases and heme-binding vitellogenin-like proteins. All of them are functionally related to blood ingestion and regulation of host defensive responses, so they can be interesting candidate protective antigens for vaccines.
The O. erraticus sialotranscriptome contains thousands of protein coding sequences-many of them belonging to large conserved multigene protein families-and shows a complexity and functional redundancy similar to those observed in the sialomes of other argasid and ixodid tick species. This high functional redundancy emphasises the need for developing multiantigenic tick vaccines to reach full protection. This research provides a set of promising candidate antigens for the development of vaccines for the control of O. erraticus infestations and prevention of tick-borne diseases of public and veterinary health relevance, such as TBRF and ASF. Additionally, this transcriptome constitutes a valuable reference database for proteomics studies of the saliva and salivary glands of O. erraticus.
鳞皮扇头蜱 Ornithodoros erraticus 是地中海盆地蜱传回归热（TBRF）和非洲猪瘟（ASF）的主要传播媒介。蜱在吸血过程中分泌到宿主的唾液蛋白在蜱的吸血和可能导致宿主感染蜱传病原体中发挥关键作用；因此，这些蛋白质代表了针对控制和预防蜱类滋生和蜱传疾病的疫苗开发的有趣的抗原靶标。
为了鉴定这些蛋白质，我们从头组装了鳞皮扇头蜱唾液腺的转录组，并使用 Illumina 测序评估了整个营养周期中的唾液基因表达动态。选择在喂食后上调的基因，并将其作为潜在的蜱疫苗抗原候选物进行讨论。
转录组组装得到 22007 个转录本和 18961 个注释转录本，这代表了 86.15%的注释成功率。大多数唾液基因表达发生在喂食后 7 天内（2088 个上调转录本），而只有少数基因（122 个上调转录本）从喂食后第 7 天开始差异表达。喂食后丰度更高的蛋白家族有脂质运载蛋白、酸碱性尾部蛋白、蛋白酶（特别是金属蛋白酶）、蛋白酶抑制剂、分泌型磷脂酶 A2、5'-核苷酸酶/ apyrases 和血红素结合卵黄原蛋白样蛋白。所有这些都与血液摄入和宿主防御反应的调节有关，因此它们可能是疫苗的有趣候选保护性抗原。
鳞皮扇头蜱唾液转录组包含数千个蛋白质编码序列-其中许多属于大的保守多基因蛋白家族-并且显示出与其他鳞皮扇头蜱和硬蜱唾液体相似的复杂性和功能冗余性。这种高功能冗余强调了开发多抗原性蜱疫苗以达到完全保护的必要性。本研究为开发控制鳞皮扇头蜱滋生和预防公共卫生和兽医卫生相关的蜱传疾病（如 TBRF 和 ASF）的疫苗提供了一组有前途的候选抗原。此外，该转录组构成了鳞皮扇头蜱唾液和唾液腺蛋白质组学研究的宝贵参考数据库。
