Walker David H, Ismail Nahed, Olano Juan P, McBride Jere W, Yu Xue-Jie, Feng Hui-Min
Department of Pathology, University of Texas Medical Branch, World Health OrganizationCollaborating Center for Tropical Diseases, UTMB Center for Biodefense and EmergingInfectious Diseases, Galveston, Texas 77555-0609,
Trans Am Clin Climatol Assoc. 2004;115:375-82; discussion 382-4.
Ehrlichia chaffeensis are small, obligately intracellular, endosomal bacteria with tropism for macrophages. Persistent infection in reservoir white-tailed deer is transmitted by lone star ticks. Flu-like illness can progress to severe multisystem disease with toxic shock-like syndrome, meningitis, or ARDS. The case-fatality rate is 2.7%. Leukopenia and thrombocytopenia are diagnostically useful. Granulomas are associated with control of the infection. Ehrlichial proteins and glycoproteins have been sequenced and expressed for diagnostic serology and vaccine development. Mouse models (mild disease and persistent infection with E. muris and fatal monocytotropic ehrlichiosis with a Japanese tick isolate) revealed that CD4 and CD8 T type 1 lymphocyte responses, IFN-gamma, TNF-alpha, and antibodies play roles in protective immunity, while a weak CD4 T-helper response, overproduction of TNF-alpha, and very high IL-10 are associated with toxic shock-like mortality. Protection against fatal ehrlichiosis was achieved by prior infection with low virulence E. muris. Acute clinical diagnosis is difficult except by PCR. Response to doxycycline is dramatic.
查菲埃立克体是一种小型的、专性细胞内寄生的、存在于内体中的细菌，对巨噬细胞具有嗜性。储存宿主白尾鹿的持续性感染通过孤星蜱传播。流感样疾病可进展为伴有中毒性休克样综合征、脑膜炎或急性呼吸窘迫综合征的严重多系统疾病。病死率为2.7%。白细胞减少和血小板减少在诊断上有帮助。肉芽肿与感染的控制有关。埃立克体蛋白和糖蛋白已被测序并表达，用于诊断血清学和疫苗开发。小鼠模型（轻度疾病和感染鼠埃立克体的持续性感染以及感染日本蜱分离株的致命单核细胞增多性埃立克体病）显示，CD4和CD8 T1型淋巴细胞反应、干扰素-γ、肿瘤坏死因子-α和抗体在保护性免疫中发挥作用，而较弱的CD4 T辅助反应、肿瘤坏死因子-α的过度产生和非常高的白细胞介素-10与中毒性休克样死亡率有关。通过预先感染低毒力的鼠埃立克体可实现对致命性埃立克体病的保护。除了通过聚合酶链反应外，急性临床诊断很困难。对多西环素的反应显著。
