Department of Medicine, Michael G. DeGroote School of Medicine, McMaster University, Hamilton, ON L8N 3Z5, Canada.
McMaster Centre for Transfusion Research, McMaster University, Hamilton, ON L8N 3Z5, Canada.
Viruses. 2021 Apr 16;13(4):697. doi: 10.3390/v13040697.
Coronavirus Disease 2019 (COVID-19) is a global pandemic caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While detection of SARS-CoV-2 by polymerase chain reaction with reverse transcription (RT-PCR) is currently used to diagnose acute COVID-19 infection, serological assays are needed to study the humoral immune response to SARS-CoV-2. Anti-SARS-CoV-2 immunoglobulin (Ig)G/A/M antibodies against spike (S) protein and its receptor-binding domain (RBD) were characterized in recovered subjects who were RT-PCR-positive ( = 153) and RT-PCR-negative ( = 55) using an enzyme-linked immunosorbent assay (ELISA). These antibodies were also further assessed for their ability to neutralize live SARS-CoV-2 virus. Anti-SARS-CoV-2 antibodies were detected in 90.9% of resolved subjects up to 180 days post-symptom onset. Anti-S protein and anti-RBD IgG titers correlated (r = 0.5157 and r = 0.6010, respectively) with viral neutralization. Of the RT-PCR-positive subjects, 22 (14.3%) did not have anti-SARS-CoV-2 antibodies; and of those, 17 had RT-PCR cycle threshold (Ct) values > 27. These high Ct values raise the possibility that these indeterminate results are from individuals who were not infected or had mild infection that failed to elicit an antibody response. This study highlights the importance of serological surveys to determine population-level immunity based on infection numbers as determined by RT-PCR.
新型冠状病毒病（COVID-19）是由新型严重急性呼吸系统综合征冠状病毒 2（SARS-CoV-2）引起的全球大流行疾病。聚合酶链反应（PCR）联合逆转录检测目前用于诊断急性 COVID-19 感染，但需要血清学检测来研究针对 SARS-CoV-2 的体液免疫反应。本研究采用酶联免疫吸附试验（ELISA）检测恢复期患者（PCR 阳性患者 = 153 例，PCR 阴性患者 = 55 例）血清中针对 S 蛋白及其受体结合域（RBD）的抗 SARS-CoV-2 免疫球蛋白（Ig）G/A/M 抗体。进一步评估了这些抗体中和活 SARS-CoV-2 病毒的能力。在发病后 180 天内，90.9%的症状缓解患者可检测到抗 SARS-CoV-2 抗体。抗 S 蛋白 IgG 和抗 RBD IgG 滴度与病毒中和能力相关（r = 0.5157 和 r = 0.6010）。在 PCR 阳性患者中，有 22 例（14.3%）未检测到抗 SARS-CoV-2 抗体，其中 17 例的 RT-PCR 循环阈值（Ct）值> 27。这些高 Ct 值提示这些不确定结果可能来自未感染或感染较轻未能产生抗体反应的个体。本研究强调了血清学调查的重要性，该调查可根据 RT-PCR 确定的感染人数确定人群水平的免疫情况。
