Woldehiwet Z, Horrocks B K, Scaife H, Ross G, Munderloh U G, Bown K, Edwards S W, Hart C A
Department of Veterinary Pathology, University of Liverpool, PO Box 147, Liverpool, L69 3BX, UK.
J Comp Pathol. 2002 Aug-Oct;127(2-3):142-9. doi: 10.1053/jcpa.2002.0574.
Ehrlichia phagocytophila (previously known as Cytoecetes phagocytophila) which causes tick-borne fever (TBF) in sheep and pasture fever in cattle in the UK and mainland Europe is transmitted by the temperate hard tick Ixodes ricinus. The disease in sheep is characterized by fever, leucopenia and immunosuppression. Studies on the pathogenesis and other aspects of the disease have been hampered because the organism has not been cultivated in continuous or primary cell culture systems. This paper describes the first successful cultivation of a European isolate of E. phagocytophila in two continuous cell lines, IDE8 and ISE6, derived from the temperate hard tick Ixodes scapularis. Once adapted to tick cell cultures the organism was serially sub-cultured in new cells by transferring small portions of infected cell suspension every 2 to 3 weeks. The identity of the organism was confirmed by polymerase chain reaction (PCR), with primers specific to the granulocytic ehrlichiae. Sequence analysis of the PCR products amplified from infected tick cells were shown to be identical with those amplified from the blood of sheep infected with the same strain of E. phagocytophila. A susceptible sheep inoculated with a third passage of the tick cell-adapted E. phagocytophila reacted with fever and rickettsiaemia 5 days later, thus satisfying Koch's postulates.
嗜吞噬细胞埃立克体（以前称为嗜吞噬细胞细胞内埃立克体）在英国和欧洲大陆可导致绵羊的蜱传发热（TBF）和牛的牧场热，由温带硬蜱蓖麻硬蜱传播。绵羊的这种疾病的特征为发热、白细胞减少和免疫抑制。由于该病原体尚未在连续或原代细胞培养系统中培养，因此对该疾病的发病机制和其他方面的研究受到了阻碍。本文描述了一株欧洲嗜吞噬细胞埃立克体分离株在源自温带硬蜱肩突硬蜱的两种连续细胞系IDE8和ISE6中的首次成功培养。一旦适应蜱细胞培养，该病原体通过每2至3周转移一小部分感染细胞悬液在新细胞中进行连续传代培养。通过聚合酶链反应（PCR），使用粒细胞埃立克体特异性引物，确认了该病原体的身份。从感染蜱细胞中扩增的PCR产物的序列分析显示与从感染相同嗜吞噬细胞埃立克体菌株的绵羊血液中扩增的产物相同。一只接种了经蜱细胞适应的嗜吞噬细胞埃立克体第三代传代培养物的易感绵羊在5天后出现发热和立克次体血症反应，从而满足了科赫法则。
