Abstract：
The recent COVID-19 pandemic disclosed a critical shortage of diagnostic kits worldwide, emphasizing the urgency of utilizing all resources available for the development and production of diagnostic tests. Different heterologous protein expression systems can be employed for antigen production. This study assessed novel SARS-CoV-2 proteins produced by a transient expression system in Nicotiana benthamiana utilizing an infectious clone vector based on pepper ringspot virus (PepRSV). These proteins included the truncated S1-N protein (spike protein N-terminus residues 12-316) and antigen N (nucleocapsid residues 37-402). Two other distinct SARS-CoV-2 antigens expressed in Escherichia coli were evaluated: QCoV9 chimeric antigen protein (spike protein residues 449-711 and nucleocapsid protein residues 160-406) and QCoV7 truncated antigen (nucleocapsid residues 37-402). ELISAs using the four antigens individually and the same panel of samples were performed for the detection of anti-SARS-CoV-2 IgG antibodies. Sensitivity was evaluated using 816 samples from 351 COVID-19 patients hospitalized between 5 and 65 days after symptoms onset; specificity was tested using 195 samples collected before 2018, from domiciliary contacts of leprosy patients. Our findings demonstrated consistent test sensitivity, ranging from 85 % to 88 % with specificity of 97.5 %, regardless of the SARS-CoV2 antigen and the expression system used for production. Our results highlight the potential of plant expression systems as useful alternative platforms to produce recombinant antigens and for the development of diagnostic tests, particularly in resource-constrained settings.
摘要：
最近的COVID-19大流行揭示了全球诊断试剂盒的严重短缺，强调迫切需要利用所有可用资源来开发和生产诊断测试。不同的异源蛋白表达系统可用于抗原生产。这项研究评估了利用基于胡椒环斑病毒（PepRSV）的感染性克隆载体在本氏烟草中通过瞬时表达系统产生的新型SARS-CoV-2蛋白。这些蛋白包括截短的S1-N蛋白(刺突蛋白N末端残基12-316)和抗原N(核衣壳残基37-402)。评估了在大肠杆菌中表达的其他两种不同的SARS-CoV-2抗原：QCoV9嵌合抗原蛋白（刺突蛋白残基449-711和核衣壳蛋白残基160-406）和QCoV7截短的抗原（核衣壳残基37-402）。分别使用四种抗原和同一组样品进行ELISA以检测抗SARS-CoV-2IgG抗体。使用症状发作后5至65天住院的351名COVID-19患者的816份样本评估敏感性；使用2018年之前收集的195份样本，从麻风病人的家庭接触者中测试特异性。我们的研究结果表明了一致的测试灵敏度，范围从85%到88%，特异性为97.5%，无论SARS-CoV2抗原和用于生产的表达系统如何。我们的结果强调了植物表达系统作为产生重组抗原和开发诊断测试的有用替代平台的潜力。特别是在资源受限的环境中。
