Akira I
Department of Parasitology, Gifu University School of Medicine, Japan.
Southeast Asian J Trop Med Public Health. 1997;28 Suppl 1:117-24.
An international collaborative study on echinococcosis has been carried out for the establishment of a simple means for differential serodiagnosis of alveolar echinococcosis (AE) from other parasitic diseases including cystic echinococcosis (CE). The main candidate epitope is Em18 (previously undescribed epitope of a low molecular weight protein of 18.5 kDa). Evaluation of the usefulness of Em18 is introduced in this review paper. Serum samples showing antibody response against Em18 are exclusively from AE. The predominant IgG subclass recognizing Em18 is IgG4 or IgG1 or IgG4 + IgG1 but never IgG2. There are good correlations between (1) the antibody response against Em18 and the presence of active lesions and (2) the antibody response against Em18 and the Em2-ELISA values. Em18 is, therefore, expected to be reasonably reliable and useful for differentiation of active AE from inactive AE. A new ELISA system using a partially purified Em18 enriched fraction (PP-Em 18/16-ELISA) has been evaluated for serodiagnosis of AE compared with Em2plus-ELISA. A total of 194 serum samples were examined: 127 sera from AE (79) and CE (48) in China where both AE and CE are endemic, 21 sera from CE in Australia where CE only exists, 28 sera from cysticercosis (21), paragonimiasis (5) or sparganasis (2) in Korea where no indigenous AE nor CE exists and 11 normal sera. Antibody levels by PP-Em18/16-ELISA were much higher in AE than in CE and it was also true for commercially available Em2plus-ELISA. Some of CE from China showed exceptionally higher levels of antibody in comparison with those of CE from Australia. It is suggested that these strongly positive cases of CE from China may have been exposed to both species of Echinococcus. Although most of sera from paragonimiasis showed high antibody levels by Emplus-ELISA, they were negative by PP-Em18/16-ELISA. Therefore, PP-Em18/16-ELISA is expected to be more reliable for differentiation of AE from CE and others especially in Asian countries where paragonimiasis is still not rare. Antibody responses in rodents naturally infected with E. multilocularis: Serum samples from the wild vole, Clethrionomys rufocanus bedfordiae, infected with E. multilocularis showed similar antibody responses as in AE patients, whereas those from Norway rats, Rattus norvegicus, showed almost none. The latter rodents were simultaneously infected with Taenia taeniaeformis but showed no antibody response against T. taeniaeformis either. Therefore, we speculate that Norway rats may only be infected with E. multilocularis under some immunosuppressed conditions or genetic unresponsiveness. It is stressed that Em18 is highly specific to E. multilocularis, and antibody response against Em18 is reasonably reliable for differentiation of AE from other helminthic infections by Western blot and ELISA in humans and may be useful for detection of domestic animals contaminated with E. multilocularis in the endemic area.
开展了一项关于棘球蚴病的国际合作研究，旨在建立一种简单的方法，用于肺泡型棘球蚴病（AE）与包括囊型棘球蚴病（CE）在内的其他寄生虫病的鉴别血清学诊断。主要候选表位是Em18（一种先前未描述的18.5 kDa低分子量蛋白的表位）。本文综述介绍了对Em18实用性的评估。显示出针对Em18抗体反应的血清样本仅来自AE患者。识别Em18的主要IgG亚类是IgG4或IgG1或IgG4 + IgG1，但从未是IgG2。（1）针对Em18的抗体反应与活动性病变的存在之间，以及（2）针对Em18的抗体反应与Em2-ELISA值之间存在良好的相关性。因此，Em18有望在区分活动性AE与非活动性AE方面具有合理的可靠性和实用性。与Em2plus-ELISA相比，已对一种使用部分纯化的富含Em18组分的新ELISA系统（PP-Em 18/16-ELISA）进行了AE血清学诊断评估。共检测了194份血清样本：来自中国（AE和CE均为地方病流行区）的127份血清，其中AE患者血清79份，CE患者血清48份；来自澳大利亚（仅存在CE）的21份CE患者血清；来自韩国（不存在本地AE和CE）的28份囊尾蚴病（21份）、肺吸虫病（5份）或裂头蚴病（2份）患者血清；以及11份正常血清。PP-Em18/16-ELISA检测的AE患者抗体水平远高于CE患者，市售的Em2plus-ELISA检测结果也是如此。与来自澳大利亚的CE患者相比，中国的一些CE患者血清显示出异常高的抗体水平。提示中国这些CE强阳性病例可能同时感染了两种棘球绦虫。虽然大多数肺吸虫病患者血清通过Emplus-ELISA显示高抗体水平，但通过PP-Em18/16-ELISA检测为阴性。因此，PP-Em18/16-ELISA有望在区分AE与CE及其他疾病方面更可靠，尤其是在肺吸虫病仍不罕见的亚洲国家。自然感染多房棘球绦虫的啮齿动物的抗体反应：感染多房棘球绦虫的野生田鼠（棕背䶄贝氏亚种）血清样本显示出与AE患者相似的抗体反应，而来自挪威大鼠的血清样本几乎没有抗体反应。后一种啮齿动物同时感染了泡状带绦虫，但对泡状带绦虫也没有抗体反应。因此，我们推测挪威大鼠可能仅在某些免疫抑制条件下或遗传无反应性时才会感染多房棘球绦虫。需要强调的是，Em18对多房棘球绦虫具有高度特异性，通过免疫印迹法和ELISA检测，针对Em18的抗体反应在区分人类AE与其他蠕虫感染方面具有合理的可靠性，并且可能有助于检测地方病流行区感染多房棘球绦虫的家畜。
