Instituto de Salud Carlos III, Centro Nacional de Microbiología, Majadahonda, Madrid, Spain.
Instituto de Recursos Naturales y Agrobiología de Salamanca (IRNASA-CSIC), Salamanca, Spain.
PLoS Negl Trop Dis. 2018 Sep 6;12(9):e0006741. doi: 10.1371/journal.pntd.0006741. eCollection 2018 Sep.
Cystic echinococcosis (CE) is one of the most widespread helminthic zoonoses and is caused by the tapeworm Echinococcus granulosus complex. CE diagnosis and monitoring primarily rely on imaging techniques, complemented by serology. This is usually approached by the detection of IgG antibodies against hydatid fluid (HF), but the use of this heterogeneous antigenic mixture results in a variable percentage of false positive and negative results, and has shown to be useless for follow-up due to the long persistence of anti-HF antibodies in cured patients. To improve test performances and standardization, a number of recombinant antigens mainly derived from HF have been described, among them the B2t and 2B2t antigens. The performance of these antigens in the diagnosis and follow up of patients with CE has been so far evaluated on a limited number of samples. Here, we evaluated the performances of tests based on B2t and 2B2t recombinant antigens compared to HF in IgG-ELISA and immunochromatography (IC) for the diagnosis and follow-up of patients with CE in a retrospective cohort study. A total of 721 serum samples were collected: 587 from 253 patients with CE diagnosed by ultrasonography (US), 42 from patients with alveolar echinococcosis and 92 from healthy donors from Salamanca (Spain). The highest overall sensitivity was obtained with HF in ELISA (85.5%), followed by IC containing HF and 2B2t-HF (83.0% and 78.2%, respectively). The lowest sensitivity was obtained with B2t and 2B2t in ELISA (51.8%). The highest specificity was obtained with IC containing 2B2t-HF (100%), and the lowest with HF-ELISA (78.0%). The lowest cross-reactivity with sera from patients with alveolar echinococcosis was detected with the recombinant antigens in ELISA (9.5% - 16.7%) and the highest with the HF-IC (64.3%). The results of B2t and 2B2t-ELISA were influenced by cyst stage, as classified by US according to the WHO-Informal Working Group on Echinococcosis (WHO-IWGE), with low sensitivity for inactive (CE4 and CE5) cysts, and by the drug treatment, with higher sensitivity in patients after drug treatment compared with patients not subjected to drug treatment. The two recombinant antigens in ELISA provided promising results for monitoring patients in follow-up, although their use is limited to patients with positive serology against them at the beginning of the follow-up. Potential biological reasons behind the low sensitivity of the recombinant antigens and possible strategies to enhance the performance of CE serology are discussed.
包虫病 (CE) 是最广泛流行的寄生虫病之一，由带绦虫细粒棘球蚴复合物引起。CE 的诊断和监测主要依赖于影像学技术，并辅以血清学检查。通常通过检测针对包虫液 (HF) 的 IgG 抗体来进行，但由于 HF 这种异质抗原混合物的使用，导致假阳性和假阴性结果的比例存在差异，并且由于在治愈的患者中抗-HF 抗体持续存在，因此对于随访没有任何作用。为了提高检测性能和标准化，已经描述了许多主要源自 HF 的重组抗原，其中包括 B2t 和 2B2t 抗原。迄今为止，这些抗原在 CE 患者的诊断和随访中的性能已经在有限数量的样本中进行了评估。在这里，我们在一项回顾性队列研究中评估了基于 B2t 和 2B2t 重组抗原的 IgG-ELISA 和免疫层析 (IC) 检测在 CE 患者诊断和随访中的性能，与 HF 进行了比较。共收集了 721 份血清样本：587 份来自 253 例经超声 (US) 诊断为 CE 的患者，42 份来自泡型包虫病患者，92 份来自西班牙萨拉曼卡的健康供体。在 ELISA 中，HF 获得了最高的总敏感性 (85.5%)，其次是包含 HF 和 2B2t-HF 的 IC (83.0%和 78.2%)。在 ELISA 中，B2t 和 2B2t 的敏感性最低 (51.8%)。包含 2B2t-HF 的 IC 获得了最高的特异性 (100%)，而 HF-ELISA 的特异性最低 (78.0%)。在 ELISA 中，重组抗原与泡型包虫病患者的血清交叉反应性最低 (9.5%-16.7%)，HF-IC 的交叉反应性最高 (64.3%)。B2t 和 2B2t-ELISA 的结果受到根据世界卫生组织非正式工作组 (WHO-IWGE) 按 US 分类的囊肿阶段的影响，对无活性 (CE4 和 CE5) 囊肿的敏感性较低，并且受到药物治疗的影响，与未接受药物治疗的患者相比，药物治疗后的患者敏感性更高。ELISA 中的两种重组抗原为监测随访中的患者提供了有希望的结果，尽管它们的使用仅限于在随访开始时对它们具有阳性血清学反应的患者。讨论了重组抗原敏感性低的潜在生物学原因以及增强包虫病血清学检测性能的可能策略。
