Immunological methods to detect SARS-CoV-2 seroconversion in humans are important to track COVID-19 cases and the humoral response to SARS-CoV-2 infections and immunization to future vaccines. The aim of this work was to develop a simple chromogenic magnetic bead-based immunoassay which allows rapid, inexpensive, and quantitative detection of human antibodies against SARS-CoV-2 in serum, plasma, or blood. Recombinant 6xHis-tagged SARS-CoV-2 Nucleocapsid protein was mobilized on the surface of Ni²⁺ magnetic beads and challenged with serum or blood samples obtained from controls or COVID-19 cases. The beads were washed, incubated with anti-human IgG-HPR conjugate, and immersed into a solution containing a chromogenic HPR substrate. Bead transfer and homogenization between solutions was aided by a simple low-cost device. The method was validated by two independent laboratories, and the performance to detect SARS-CoV-2 seroconversion in humans was in the same range as obtained using the gold standard immunoassays ELISA and Luminex, though requiring only a fraction of consumables, instrumentation, time to deliver results, and volume of sample. Furthermore, the results obtained with the method described can be visually interpreted without compromising accuracy as demonstrated by validation at a point-of-care unit. The magnetic bead immunoassay throughput can be customized on demand and is readily adapted to be used with any other 6xHis tagged protein or peptide as antigen to track other diseases.

中文翻译：

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基于磁珠的免疫分析可以快速、廉价地定量检测人类 SARS-CoV-2 抗体

检测人类 SARS-CoV-2 血清转化的免疫学方法对于追踪 COVID-19 病例以及对 SARS-CoV-2 感染的体液反应以及未来疫苗的免疫非常重要。这项工作的目的是开发一种简单的基于显色磁珠的免疫测定法，可以快速、廉价且定量地检测血清、血浆或血液中针对 SARS-CoV-2 的人类抗体。^{重组 6xHis 标记的 SARS-CoV-2 核衣壳蛋白被动员到 Ni 2+}磁珠表面，并用从对照或 COVID-19 病例获得的血清或血液样本进行攻击。洗涤珠子，与抗人 IgG-HPR 缀合物一起孵育，然后浸入含有显色 HPR 底物的溶液中。溶液之间的珠子转移和均质化由简单的低成本设备辅助。该方法经过两个独立实验室的验证，检测人类 SARS-CoV-2 血清转化的性能与使用金标准免疫测定 ELISA 和 Luminex 获得的性能范围相同，但只需要一小部分消耗品、仪器和时间。提供结果和样品量。此外，使用所述方法获得的结果可以直观地解释，而不会影响准确性，如在护理点验证所证明的那样。磁珠免疫测定通量可根据需求定制，并且易于与任何其他 6xHis 标记蛋白或肽一起用作抗原来追踪其他疾病。