The development of new diagnostic assays become a priority for managing COVID-19. To this aim, we presented here an in-house ELISA based on the production of two major recombinant and high-quality antigens from SARS-CoV-2. Full-length N and S-RBD fragment proteins fused to mouse IgG2a-Fc were produced in the CHO cell line. Secreted recombinant proteins were easily purified with standard Protein A chromatography and were used in an in-house ELISA to detect anti-N and anti-RBD IgGs in the plasma of COVID-19 RTPCR-positive patients. High reactivity against recombinant antigens was readily detected in all positive plasma samples, whereas no recognition was observed with control healthy subject's plasmas. Remarkably, unpurified recombinant N protein obtained from cell culture supernatant was also suitable for the monitoring by ELISA of IgG levels in positive patients. This work provides an early prospection for low price but high-quality serological kit development.

新诊断方法的开发成为管理COVID-19的优先事项。为此，我们在此介绍了一种基于SARS-CoV-2生产两种主要重组和高质量抗原的内部ELISA。在CHO细胞系中产生了与小鼠IgG2a-Fc融合的全长N和S-RBD片段蛋白。分泌的重组蛋白很容易通过标准Protein A色谱法纯化，并用于内部ELISA中，以检测COVID-19 RTPCR阳性患者血浆中的抗N和抗RBD IgG。在所有阳性血浆样品中都容易检测到针对重组抗原的高反应性，而对照健康受试者的血浆中未观察到识别。值得注意的是 从细胞培养上清液中获得的未纯化重组N蛋白也适用于通过ELISA监测阳性患者的IgG水平。这项工作为低价但高质量的血清学试剂盒的开发提供了早期的希望。