Department of Parasitology and Mycology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.
Students Scientific Research Center, Tehran University of Medical Sciences, Tehran, Iran.
J Clin Microbiol. 2020 Aug 24;58(9). doi: 10.1128/JCM.00505-20.
Risk of mother-to-child transmission of during pregnancy is much greater in women who are exposed to primary infection (toxoplasmosis) after conception compared to those who were exposed to the infection before conception. Therefore, laboratory tests that help classify recent primary toxoplasmosis are important tools for the management of pregnant women suspected to have exposure. Detection of IgM (Toxo IgM) is a sensitive indicator of primary toxoplasmosis, but the indicator specificity is low because sometimes natural IgM antibodies react with antigens in the absence of the infection. Furthermore, Toxo IgM sometimes persists in blood serum for several months or years following the primary infection. In recent decades, Toxo IgG avidity assay has been used as a standard diagnostic technique for a better estimation of the infection acquisition time and identification of the primary infection during pregnancy. Avidity is described as the aggregate strength; by which, a mixture of polyclonal IgG molecules reacts with multiple epitopes of the proteins. This parameter matures gradually within 6 months of the primary infection. A high Toxo IgG avidity index allows a recent infection (less than 4 months) to be excluded, whereas a low Toxo IgG avidity index indicates a probable recent infection with no exclusions of the older infections. This minireview is based on various aspects of IgG avidity testing, including (i) description of avidity and basic methods used in primary studies on IgG avidity and primary infections; (ii) importance of IgG avidity testing in pregnancy; (iii) result summary of the major studies on the use of IgG avidity assay in pregnancy; (iv) brief explanation of the IgG avidity values in newborns; (v) result summary of the major studies on IgG avidity and PCR; (vi) discussion of commercially available IgG avidity assays, including newer automated assays; and (vii) current issues and controversies in diagnosis of primary infections in pregnancy.
孕妇在妊娠期间感染 的母婴传播风险，相较于妊娠前感染的孕妇，妊娠后初次感染（弓形虫病）的风险要高得多。因此，有助于分类近期初次弓形虫病的实验室检测对于疑似接触过 的孕妇的管理非常重要。检测 IgM（Toxo IgM）是初次弓形虫病的敏感指标，但该指标的特异性较低，因为有时在没有感染的情况下，天然 IgM 抗体与 抗原发生反应。此外，初次感染后，Toxo IgM 有时会在血清中持续数月或数年。近几十年来，Toxo IgG 亲和力检测已被用作标准诊断技术，以便更好地估计感染获得时间并识别妊娠期间的初次感染。亲和力被描述为聚合强度，即多克隆 IgG 分子与蛋白质的多个表位反应的总和。该参数在初次感染后 6 个月内逐渐成熟。高 Toxo IgG 亲和力指数可排除近期感染（小于 4 个月），而低 Toxo IgG 亲和力指数则表明可能存在近期感染，不排除较旧的感染。本综述基于 IgG 亲和力检测的各个方面，包括：（i）亲和力的描述以及初次研究中用于 IgG 亲和力和初次感染的基本方法；（ii）IgG 亲和力检测在妊娠中的重要性；（iii）关于在妊娠中使用 Toxo IgG 亲和力检测的主要研究的结果总结；（iv）新生儿中 IgG 亲和力值的简要说明；（v）关于 IgG 亲和力和 PCR 的主要研究的结果总结；（vi）商业上可用的 IgG 亲和力检测方法的讨论，包括更新的自动化检测方法；以及（vii）妊娠期间初次感染诊断的当前问题和争议。
