Fereig Ragab M, Abdelbaky Hanan H, Ihara Fumiaki, Nishikawa Yoshifumi
National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan; Research Center for Global Agromedicine, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan; Department of Animal Medicine, Faculty of Veterinary Medicine, South Valley University, Qena City, Qena 83523, Egypt.
National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan.
Acta Trop. 2018 Sep;185:349-356. doi: 10.1016/j.actatropica.2018.06.019. Epub 2018 Jun 19.
Cryptosporidium parvum is a major cause of diarrhea among human and calves, resulting in severe health hazards and drastic economic losses, respectively. Although C. parvum infection leads to high morbidity and mortality in immunocompromised patients and bovine calves, this infection remains a neglected disease. Currently available diagnostic tests for C. parvum are primarily based on detection of oocysts, DNA, or secreted antigens in fecal specimens. Demonstration of specific antibodies with a rapid immunochromatographic test (ICT) will be advantageous not only in providing a simple, rapid, accurate, and affordable tool but also in surveillance because of the ability to recognize recent and past infections. Herein, we developed two ICTs using the diagnostic antigen CpP23 and immunodominant antigen CpGP15 to detect C. parvum-specific antibodies in cattle sera. Because of unavailability of a reference test for antibody detection, evaluation and validation of our developed ICTs were conducted using reference cattle samples and unknown field cattle sera. Serum samples were simultaneously tested by a previously validated enzyme-linked immunosorbent assay (ELISA) using the same antigens (CpGP15 and CpP23). ICTs showed substantial ability to discriminate between positive and negative control cattle sera for both CpGP15 and CpP23. Even against field sera, high sensitivity, specificity, and agreement rates were recorded for ICTs compared with the previously validated ELISA with the same antigens (CpGP15 = 78.78%, 100%, and 85.11%; CpP23 = 80%, 100%, and 80.56%, respectively). Moreover, a high correlation was observed between the test band intensity of ICTs and optical density of ELISA, particularly in the case of CpP23-specific IgM. To our knowledge, this study represents the first development of ICTs that can detect C. parvum-specific antibodies. Our tests will contribute greatly to C. parvum infection control in cattle by providing a method for on-site diagnosis of early and latent infections.
微小隐孢子虫是人类和犊牛腹泻的主要病因，分别导致严重的健康危害和巨大的经济损失。尽管微小隐孢子虫感染在免疫功能低下的患者和犊牛中会导致高发病率和死亡率，但这种感染仍然是一种被忽视的疾病。目前可用的微小隐孢子虫诊断测试主要基于粪便标本中卵囊、DNA或分泌抗原的检测。用快速免疫层析试验（ICT）检测特异性抗体不仅将提供一种简单、快速、准确且经济实惠的工具，而且由于能够识别近期和既往感染，在监测方面也具有优势。在此，我们使用诊断抗原CpP23和免疫显性抗原CpGP15开发了两种ICT，以检测牛血清中的微小隐孢子虫特异性抗体。由于缺乏用于抗体检测的参考测试，我们使用参考牛样本和未知的田间牛血清对开发的ICT进行评估和验证。血清样本同时通过使用相同抗原（CpGP15和CpP23）的先前验证的酶联免疫吸附测定（ELISA）进行检测。对于CpGP15和CpP23，ICT均显示出区分阳性和阴性对照牛血清的强大能力。即使针对田间血清，与使用相同抗原的先前验证的ELISA相比，ICT也具有较高的敏感性、特异性和符合率（CpGP15分别为78.78%、100%和85.11%；CpP23分别为80%、100%和80.56%）。此外，观察到ICT的测试带强度与ELISA的光密度之间具有高度相关性，特别是在CpP23特异性IgM的情况下。据我们所知，本研究代表了首次开发能够检测微小隐孢子虫特异性抗体的ICT。我们的测试将通过提供一种现场诊断早期和潜伏感染的方法，极大地有助于控制牛的微小隐孢子虫感染。
