Program in Vector-Borne Diseases, Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, 99164-7040, USA.
USDA-ARS-Animal Diseases Research Unit, Pullman, WA, 99164-6630, USA.
Parasit Vectors. 2021 Dec 24;14(1):616. doi: 10.1186/s13071-021-05120-7.
Vector-borne diseases pose an increasing threat to global food security. Vaccines, diagnostic tests, and therapeutics are urgently needed for tick-borne diseases that affect livestock. However, the inability to obtain significant quantities of pathogen stages derived from ticks has hindered research. In vitro methods to isolate pathogens from infected tick vectors are paramount to advance transcriptomic, proteomic, and biochemical characterizations of tick-borne pathogens.
Nymphs of Rhipicephalus appendiculatus were infected with Theileria parva by feeding on a calf during an acute infection. Isolation of sporozoites was accomplished by feeding infected adult ticks on an in vitro tick feeding system. Sporozoite viability was tested using in vitro bovine lymphocytes.
We isolated infectious T. parva sporozoites secreted into an in vitro tick feeding system. Infected adult R. appendiculatus ticks attached to and successfully fed on silicone membranes in the in vitro tick feeding system. Bovine blood in the receptacle was replaced with cell-free medium and the ticks were allowed to feed for 3 h to collect secreted T. parva sporozoites. Secreted sporozoites infected in vitro bovine lymphocytes, demonstrating that isolated sporozoites remained viable and infectious.
This work is the first to report the isolation of mature infectious T. parva sporozoites using an in vitro tick feeding system, which represents a significant step towards the development of a more efficient control strategy for T. parva. Isolation of infectious tick-stage parasites will facilitate the examination of the vector-pathogen interface, thereby accelerating the development of next-generation vaccines and treatment interventions for tick-borne pathogens.
虫媒病对全球粮食安全构成的威胁日益增加。受感染牲畜的蜱传疾病急需疫苗、诊断测试和疗法。然而，由于无法获得大量源自蜱的病原体阶段，研究受到阻碍。从受感染的蜱传病媒介中分离病原体的体外方法对于推进蜱传病原体的转录组学、蛋白质组学和生物化学特性研究至关重要。
通过在急性感染期间让小牛被感染的 Rhipicephalus appendiculatus 若虫叮咬，使这些若虫感染 Theileria parva。通过在体外蜱喂养系统上喂养感染的成年蜱来分离孢子虫。使用体外牛淋巴细胞测试孢子虫活力。
我们从体外蜱喂养系统中分离出了具有感染性的 T. parva 孢子虫。附着在体外蜱喂养系统的硅树脂膜上并成功进食的感染成年 R. appendiculatus 蜱。在容纳器中的牛血被无细胞培养基取代，然后让蜱进食 3 小时以收集分泌的 T. parva 孢子虫。分泌的孢子虫感染体外牛淋巴细胞，表明分离的孢子虫仍然具有活力和感染性。
这项工作首次报告了使用体外蜱喂养系统分离成熟的具有感染性的 T. parva 孢子虫，这是朝着开发更有效的 T. parva 控制策略迈出的重要一步。分离具有感染性的蜱阶段寄生虫将有助于检查媒介-病原体界面，从而加速蜱传病原体的下一代疫苗和治疗干预措施的开发。
