Background

Coronavirus disease 2019 (COVID-19) pandemic caused by infection with severe acute respiratory syndrome – coronavirus-2 (SARS-CoV-2) continues to affect many countries and large populations. Serologic assays for antibody detection aid patient diagnosis and seroepidemiologic investigations.

Methods

An indirect IgG ELISA was developed indigenously using β-propiolactone (BPL) inactivated SARS-CoV-2. This assay was used for screening 200 healthy donor sera collected prior to COVID-19 emergence (2017–2019), 185 serum/plasma samples of confirmed COVID-19 patients (n = 137) and 57 samples of viral RNA positive asymptomatic contacts (n = 51). The IgG response was studied in relation to duration and severity of illness.

Results

The ELISA demonstrated 97 % specificity and IgG detection in >50 %, 80 %, 93.8 % and 100 % of the patients respectively during the first, second, third and fourth week of illness. IgG detection rate was higher in patients with severe disease (SD, 90.9 %) than those with mild disease (MD, 68.8 %) during the second week of illness (P = 0.027). IgG seropositivity among asymptomatic contacts was 64.7 %. IgG ELISA absorbance values were higher in SD than MD patients during the first 2 weeks of illness (P < 0.05). No significant difference was observed between the absorbance values of asymptomatic subjects and MD patients (P = 0.94).

Conclusion

The BPL inactivated virus-based ELISA could detect IgG antibodies early and in a significant proportion of COVID-19 patients suggesting its potential utility as a supplement to the currently used viral RNA detection tests in patient diagnosis and contact screening algorithms.

中文翻译：

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β-丙内酯灭活，基于全病毒的间接ELISA法在印度COVID-19患者中抗SARS-CoV-2 IgG抗体反应

背景

由严重急性呼吸系统综合症感染引起的2019年冠状病毒病（COVID-19）大流行–冠状病毒2（SARS-CoV-2）继续影响许多国家和人口。用于抗体检测的血清学检测有助于患者诊断和血清流行病学研究。

方法

使用β-丙内酯（BPL）灭活的SARS-CoV-2在本地开发了间接IgG ELISA。该检测方法用于筛查COVID-19出现之前（2017-2019年）收集的200份健康供体血清，确诊的COVID-19患者的185份血清/血浆样本（n = 137）和57份病毒RNA阳性无症状接触样本（n = 51）。研究了与疾病的持续时间和严重程度有关的IgG反应。

结果

ELISA在患病的第一周，第二周，第三周和第四周分别对> 50％，80％，93.8％和100％的患者显示出97％的特异性和IgG检测。在疾病的第二周，重症患者（SD，90.9％）的IgG检出率高于轻症患者（MD，68.8％）（P  = 0.027）。无症状接触者的IgG血清阳性率为64.7％。在疾病的前两周，SD患者的IgG ELISA吸光度值高于MD患者（P  <0.05）。无症状受试者和MD患者的吸光度值之间未观察到显着差异（P  = 0.94）。

结论

BPL灭活的基于病毒的ELISA可以及早和大量COVID-19患者中检测IgG抗体，表明其潜在用途可作为对患者诊断和接触筛选算法中当前使用的病毒RNA检测测试的补充。