Division of Infectious Diseases, Department of Medicine, Faculty of Medicine, Thai Red Cross Emerging Infectious Diseases Clinical Centre, King Chulalongkorn Memorial Hospital, Chulalongkorn University, Bangkok, Thailand.
Thai Red Cross Emerging Infectious Diseases Health Science Centre World Health Organization Collaborating Centre for Research and Training on Viral Zoonoses, King Chulalongkorn Memorial Hospital, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
PLoS One. 2021 Feb 12;16(2):e0246864. doi: 10.1371/journal.pone.0246864. eCollection 2021.
The presence of neutralizing antibodies (NAbs) is an indicator of protective immunity for most viral infections. A newly developed surrogate viral neutralization assay (sVNT) offers the ability to detect total receptor binding domain-targeting NAbs in an isotype-independent manner, increasing the test sensitivity. Thus, specimens with low IgM/ IgG antibody levels showed strong neutralization activity in sVNT.
This study aimed to measure the %inhibition of NAbs measured by sVNT in PCR-confirmed COVID-19 patients. The sensitivity of sVNT for the diagnosis of SARS-CoV-2 infection and its kinetics were determined.
Ninety-seven patients with PCR-confirmed SARS-CoV-2 infection were included in this study. Majority of the patients were 21-40 years old (67%) and 63% had mild symptoms. The sensitivity of sVNT for the diagnosis of SARS-CoV-2 infection was 99% (95% confidence interval (CI) 94.4-100%) and the specificity was 100% (95% CI 98.3-100%). The negative predictive value of sVNT from the samples collected before and after 7 days of symptom onset was 99.5% (95% CI 97.4-100%) and 100% (95% CI 93.8-100%), respectively. The level of inhibition at days 8-14 were significantly higher than days 0-7 (p<0.001). The median %inhibition values by severity of COVID-19 symptoms were 79.9% (interquartile range (IQR) 49.7-91.8%); 89.0% (IQR 71.2-92.4%); and 86.6% (IQR 69.5-92.8%), for mild, moderate and severe/critical symptoms respectively. The median level of sVNT %inhibition of severe was significantly higher than the mild group (p = 0.05).
The sVNT is a practical and robust serological test for SARS-CoV-2 infection and does not require specialized biosafety containment. It can be used clinically to aid diagnosis in both early and late infection especially in cases when the real-time RT-PCR results in weakly negative or weakly positive, and to determine the protective immune response from SARS-CoV-2 infection in patients.
中和抗体（NAb）的存在是大多数病毒感染保护性免疫的指标。新开发的替代病毒中和测定法（sVNT）能够以非免疫球蛋白依赖性方式检测靶向受体结合域的总 NAb，从而提高了检测的灵敏度。因此，在 sVNT 中，IgM/IgG 抗体水平较低的标本显示出强烈的中和活性。
本研究旨在测量通过 sVNT 测量的 NAb 的抑制率在经 PCR 确诊的 COVID-19 患者中。确定了 sVNT 对 SARS-CoV-2 感染的诊断敏感性及其动力学。
本研究纳入了 97 例经 PCR 确诊的 SARS-CoV-2 感染患者。大多数患者年龄在 21-40 岁（67%），63%的症状较轻。sVNT 对 SARS-CoV-2 感染的诊断敏感性为 99%（95%置信区间（CI）94.4-100%），特异性为 100%（95%CI 98.3-100%）。症状出现后 7 天内采集的样本的 sVNT 阴性预测值分别为 99.5%（95%CI 97.4-100%）和 100%（95%CI 93.8-100%）。第 8-14 天的抑制水平明显高于第 0-7 天（p<0.001）。根据 COVID-19 症状严重程度的中位数抑制率分别为 79.9%（四分位距（IQR）49.7-91.8%）；89.0%（IQR 71.2-92.4%）；86.6%（IQR 69.5-92.8%），分别为轻度、中度和重度/危重症。严重组的 sVNT 抑制率中位数明显高于轻度组（p = 0.05）。
sVNT 是一种实用且强大的 SARS-CoV-2 感染血清学检测方法，不需要专门的生物安全控制。它可以在临床上用于辅助早期和晚期感染的诊断，尤其是在实时 RT-PCR 结果呈弱阳性或弱阳性的情况下，以及确定 SARS-CoV-2 感染患者的保护性免疫反应。
