Keshavarz Behnam, Wiencek Joesph R, Workman Lisa J, Straesser Matthew D, Muehling Lyndsey M, Canderan Glenda, Drago Fabrizio, Bonham Catherine A, Sturek Jeffrey M, Ramani Chintan, McNamara Coleen A, Woodfolk Judith A, Kadl Alexandra, Platts-Mills Thomas A E, Wilson Jeffrey M
medRxiv. 2020 Nov 12:2020.11.09.20228411. doi: 10.1101/2020.11.09.20228411.
Detailed understanding of the immune response to SARS-CoV-2, the cause of coronavirus disease 2019 (COVID-19), has been hampered by a lack of quantitative antibody assays.
To develop a quantitative assay for IgG to SARS-CoV-2 proteins that could readily be implemented in clinical and research laboratories.
The biotin-streptavidin technique was used to conjugate SARS-CoV-2 spike receptor-binding-domain (RBD) or nucleocapsid protein to the solid-phase of the ImmunoCAP resin. Plasma and serum samples from patients with COVID-19 (n=51) and samples from donors banked prior to the emergence of COVID-19 (n=109) were used in the assay. SARS-CoV-2 IgG levels were followed longitudinally in a subset of samples and were related to total IgG and IgG to reference antigens using an ImmunoCAP 250 platform.
Performance characteristics demonstrated 100% sensitivity and 99% specificity at a cut-off level of 2.5 µg/mL for both SARS-CoV-2 proteins. Among 36 patients evaluated in a post-hospital follow-up clinic, median levels of IgG to spike-RBD and nucleocapsid were 34.7 µg/mL (IQR 18-52) and 24.5 µg/mL (IQR 9-59), respectively. Among 17 patients with longitudinal samples there was a wide variation in the magnitude of IgG responses, but generally the response to spike-RBD and to nucleocapsid occurred in parallel, with peak levels approaching 100 µg/mL, or 1% of total IgG.
We have described a quantitative assay to measure IgG to SARS-CoV-2 that could be used in clinical and research laboratories and implemented at scale. The assay can easily be adapted to measure IgG to novel antigens, has good performance characteristics and a read-out in standardized units.
由于缺乏定量抗体检测方法，对严重急性呼吸综合征冠状病毒2（SARS-CoV-2，2019冠状病毒病（COVID-19）的病原体）免疫反应的详细了解受到了阻碍。
开发一种针对SARS-CoV-2蛋白的IgG定量检测方法，该方法可在临床和研究实验室中轻松实施。
采用生物素-链霉亲和素技术将SARS-CoV-2刺突受体结合域（RBD）或核衣壳蛋白偶联到免疫捕获树脂的固相上。该检测使用了COVID-19患者的血浆和血清样本（n=51）以及COVID-19出现之前储存的供体样本（n=109）。在一部分样本中纵向跟踪SARS-CoV-2 IgG水平，并使用免疫捕获250平台将其与总IgG以及针对参考抗原的IgG相关联。
对于两种SARS-CoV-2蛋白，在截断水平为2.5 µg/mL时，性能特征显示灵敏度为100%，特异性为99%。在一家医院后随访诊所评估的36名患者中，针对刺突-RBD和核衣壳的IgG中位水平分别为34.7 µg/mL（四分位间距18-52）和24.5 µg/mL（四分位间距9-59）。在17名有纵向样本的患者中，IgG反应幅度差异很大，但一般来说，对刺突-RBD和核衣壳的反应是平行发生的，峰值水平接近100 µg/mL，或占总IgG的1%。
我们描述了一种用于测量针对SARS-CoV-2的IgG的定量检测方法，该方法可用于临床和研究实验室并大规模实施。该检测方法可轻松适用于测量针对新抗原的IgG，具有良好的性能特征且以标准化单位读出结果。
