Sierrallana Hospital, Barrio de Ganzo s/n, Torrelavega, Spain.
Cukurova Univeristy, Department of Parasitology, Sarıçam/Adana, Turkey.
PLoS Negl Trop Dis. 2020 Nov 30;14(11):e0008892. doi: 10.1371/journal.pntd.0008892. eCollection 2020 Nov.
Cystic echinococcosis (CE) is a neglected zoonotic disease caused by Echinococcus granulosus sensu lato. Diagnosis and monitoring of CE rely primarily on imaging while serology is used as a confirmatory test. However, imaging is not always conclusive and currently available serological assays have suboptimal sensitivity and specificity, lack standardization, and are not useful for patients´ follow-up. Seroassays for CE are usually based on hydatid fluid (HF), a complex, variable antigenic mixture, and cross-reactivity exists especially with alveolar echinococcosis. Recombinant proteins based on immunogenic antigens most abundant in HF, such as AgB1, AgB2 and Ag5, have been used to overcome these limitations. None of them so far showed potential to replace HF; however, their performance have been largely tested on a limited number of samples, and comparison of different antigens using the same cohort has been rarely performed. The combination of several immunogenic epitopes in a single recombinant protein could enhance test sensitivity. For the diagnosis and follow-up of patients with CE, we compared the performance of the crude HF, previously described recombinant 2B2t antigen, and GST-tagged version of 2B2t, and novel designed recombinants (GST-Ag5t and the GST-DIPOL chimera containing AgB1, AgBB2 and Ag5 epitopes) by IgG-ELISA format. Samples belong to a retrospective cohort of 253 well-characterized patients with CE, previously described for the evaluation of the 2B2t antigen, 92 patients with alveolar echinococcosis, and 82 healthy donors. The reference standard for CE diagnosis was the presence of a CE lesion as diagnosed by ultrasonography. The highest sensitivity was obtained with HF [86.7%, 95% confidence interval (CI): 81.2-91.0], followed by GST-2B2t (70.0%, 95% CI: 63.1-76.2), 2B2t (65.5%, 95% CI: 58.5-72.0), GST-Ag5t (64.5%, 95% CI: 57.5-71.1) and GST-DIPOL (63.1%, 95% CI: 56.0-69.7). The GST-2B2t had the best specificity (95.8%, 95% CI: 88.3-99.1) and the lowest cross-reactivity (38.7%, 95% CI: 27.6-50.6). Good response to treatment also correlated to negative test results in the GST-2B2t ELISA. While none of the tested recombinant antigen appears suitable to replace HF for the diagnosis of CE, GST-2B2t should be further explored as a confirmation test, based on its high specificity and low cross-reactivity, and for the follow-up after treatment in those patients with positive serology for this antigen.
囊性包虫病 (CE) 是一种被忽视的人畜共患疾病，由细粒棘球绦虫亚种引起。CE 的诊断和监测主要依赖于影像学，而血清学检测则作为确认性检测。然而，影像学并不总是具有结论性，目前可用的血清学检测方法敏感性和特异性不佳，缺乏标准化，并且对患者的随访没有帮助。CE 的血清学检测通常基于包虫液（HF），这是一种复杂的、可变的抗原混合物，特别是与泡型包虫病存在交叉反应。基于 HF 中最丰富的免疫原性抗原的重组蛋白，如 AgB1、AgB2 和 Ag5，已被用于克服这些限制。到目前为止，它们都没有显示出取代 HF 的潜力；然而，它们的性能在很大程度上是在有限数量的样本上进行测试的，并且很少使用相同的队列比较不同的抗原。在单个重组蛋白中组合多个免疫原性表位可能会提高检测的敏感性。为了诊断和随访 CE 患者，我们比较了粗 HF、先前描述的重组 2B2t 抗原和 GST 标记的 2B2t 版本，以及新设计的重组蛋白（GST-Ag5t 和包含 AgB1、AgBB2 和 Ag5 表位的 GST-DIPOL 嵌合体）的性能，方法是使用 IgG-ELISA 格式。这些样本来自一个经过充分描述的 253 名 CE 患者的回顾性队列，之前已经评估过 2B2t 抗原，92 名泡型包虫病患者和 82 名健康供体。CE 诊断的参考标准是超声诊断的 CE 病变存在。HF 的敏感性最高 [86.7%，95%置信区间（CI）：81.2-91.0]，其次是 GST-2B2t（70.0%，95%CI：63.1-76.2），2B2t（65.5%，95%CI：58.5-72.0），GST-Ag5t（64.5%，95%CI：57.5-71.1）和 GST-DIPOL（63.1%，95%CI：56.0-69.7）。GST-2B2t 具有最佳的特异性（95.8%，95%CI：88.3-99.1）和最低的交叉反应性（38.7%，95%CI：27.6-50.6）。治疗反应良好也与 GST-2B2t ELISA 检测结果阴性相关。虽然没有一种测试的重组抗原似乎适合取代 HF 来诊断 CE，但基于其高特异性和低交叉反应性，GST-2B2t 应该进一步探索作为确认性检测，以及用于那些对此抗原呈血清学阳性的患者的治疗后随访。
