Early Detection of Congenital Chagas Disease

描述（申请人提供）：克氏锥虫新增感染病例中有26%是通过母婴传播，随着病媒和献血控制的改善，先天性感染的比例将会增加。在拉丁美洲，估计有800万人终生感染克鲁兹锥虫。大约5%的克氏锥虫感染妇女在出生时、出生后不久或以后生育的受感染婴儿有临床表现的恰加斯病的风险。以实验室为基础的筛查对于发现先天性感染至关重要，早期发现对于最有效的治疗至关重要。在高患病率地区，一种有希望的方法可能是普遍的新生儿筛查，因为这是对一些遗传和代谢疾病的常规筛查。然而，目前还没有足够敏感、特异性和逻辑上可行的检测方法来诊断生命早期的先天性克氏锥虫感染，而且目前拉丁美洲的项目完成率很低。整个拉丁美洲目前的先天性克氏锥虫诊断标准依赖于浓缩脐带血显微镜检查，然后在9个月时进行血清学检查。在我们之前在玻利维亚的研究中，我们发现传播率为6.5%（10/154名受感染母亲的婴儿）。然而，没有一个感染婴儿的脐带血在显微镜下被检测到，在前30天收集的3个额外样本中，只有40%的样本在显微镜下被检测到（一个比常规程序所能维持的密集得多的采样计划）。由于医院缺乏床位，妇女往往在分娩后12-18小时内出院，使后续工作复杂化。目前的快速产前筛查只有90%的敏感性，假阴性结果的母亲很少带婴儿回来随访。我们发现，PCR阳性的妇女比PCR阴性的血清阳性妇女更容易传播克鲁氏锥虫，感染婴儿的母亲有更高的寄生虫载量。PCR在出生时检测到89%的感染婴儿，在30天内检测到100%。尽管付出了巨大的努力，但只有58%的高危婴儿完成了9个月的随访。我们估计，目前的筛查计划漏掉了一半以上的感染婴儿。本申请的目的是开发和评估新技术（环介导的等温扩增，抗原检测测定和增强的IgM测定，用于Shed急性期抗原抗体），最终目的是开发一种快速的，即时护理的形式来测试新生儿。此外，我们将评估产前聚合酶链反应和克鲁兹锥虫特异性免疫反应的使用，以确定传播风险最高的妇女，以确保对其婴儿进行更深入的随访。

DESCRIPTION (provided by applicant): Twenty-six percent of new Trypanosoma cruzi infections occur through mother-to-child transmission, and as vector and blood donation control improve, the proportion attributable to congenital infection will grow. An estimated 8 million persons have lifelong T. cruzi infection in Latin America. Approximately 5% of T. cruzi infected women give birth to infected infants at risk of clinically manifest Chagas disease at birth, shortly after birth or later in life. Laboratory-based screening is essential to detect congenital infection, and early detection is important to the most effective treatment. In high-prevalence areas, one promising approach may be universal newborn screening, as is routine for some genetic and metabolic disorders. However, there is no sufficiently sensitive, specific and logistically feasible test to diagnose congenital T. cruzi infection early in life, and current Latin American programs have low completion rates. The current standard for congenital T. cruzi diagnosis throughout Latin America relies on microscopy of concentrated cord blood, followed by serology at 9 months. In our previous study in Bolivia, we found a transmission rate of 6.5% (10/154 infants of infected mothers). However, none of the infected infants were detected by microscopy in cord blood, and only 40% were detected by microscopy in any of the 3 additional specimens collected in the first 30 days (a much more intensive sampling schedule than routine programs can sustain). Because hospitals lack beds, women are often discharged within 12-18 hours of delivery, complicating follow-up efforts. Prenatal screening with current rapid tests had only 90% sensitivity, and mothers with false-negative results seldom brought infants back for follow- up. We found that PCR-positive women were significantly more likely to transmit T. cruzi than seropositive women with negative PCR, and mothers of infected infants had significantly higher parasite loads. PCR detected 89% of infected infants at birth and100% by 30 days. Despite intensive efforts, only 58% of at-risk infants completed 9-month follow-up. We estimate that current screening programs miss more than half of all infected infants. The aim of this application is to develop and evaluate novel techniques (Loop Mediated Isothermal Amplification, antigen detections assays and enhanced IgM assay for antibodies to Shed Acute Phase Antigens), with the ultimate aim of developing a rapid, point-of-care format to test neonates. In addition we will assess the use of prenatal PCR and T. cruzi-specific immune responses to identify the women with the highest risk of transmission, in order to ensure more intensive follow-up of their infants.