Huan Ma, W. Zeng, Hongliang He, Dan Zhao, Yunru Yang, De-hua Jiang, P. Zhou, Yingjie Qi, W. He, Changcheng Zhao, Ruting Yi, Xiaofang Wang, B. Wang, Yuanhong Xu, Yun Yang, Arnaud John Kombe Kombe, Chengchao Ding, J. Xie, Yong Gao, L. Cheng, Yajuan Li, Xiaoling Ma, T. Jin
medRxiv, 2020
Background The current pandemic of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has caused a great loss in lives and economy. Detecting viral RNAs on nasopharyngeal and throat swabs is the standard approach for SARS-CoV-2 diagnosis with variable success. Currently, there are only a few studies describing the serological diagnostic methods that involve the detection of SARS-CoV-2-specific IgM and IgG. Here, we aimed to develop a more quantitative and sensitive serological test for COVID-19 diagnosis, monitoring and clinical investigation, based on the detection of antigen-specific IgA as well as IgM and IgG in blood in response to SARS-CoV-2 infection. Methods In this investigation, we report the development of a set of validated diagnostic kits for detecting serum IgA, IgM, and IgG specific to SARS-CoV-2 nucleocapsid protein (NP) and receptor-binding domain (RBD) of the spike protein by chemi-luminescence immuno-analysis. The kits were tested with a cohort of 216 sera from 87 laboratory-confirmed COVID-19 patients, and 483 sera from SARS-CoV-2 negative or healthy individuals as negative controls. A standard receiver operating characteristic (ROC) analysis was conducted to evaluate the diagnostic accuracy. Using the kits, serum levels of IgA, IgM, and IgG were analyzed, in response to SARS-CoV-2 infection and COVID-19 pathogenesis. Findings The diagnostic kits based on the RBD antigen outperformed those based on the NP. RBD-specific IgA, IgM, and IgG detection kits showed sensitivities of 98.6%, 96.8%, and 96.8%, and specificities of 98.1%, 92.3%, and 99.8%, respectively. In addition, using purified RBD-specific immunoglobulins from a serum pool of COVID-19 patients as standards, the serum concentrations of RBD-specific IgA, IgM, and IgG proteins were determined. The concentrations varied widely among different patients. Median concentration of IgA and IgM reached peaks at 16-20 days after illness onset at 8.84 μg/mL and 7.25 μg/mL, respectively, while median concentration of IgG peaked during 21-25 days after illness onset at 16.47 μg/mL. Furthermore, the serum IgA level positively correlates with COVID-19 severity. Interpretation Our immunoassay of measuring SARS-CoV-2 specific antibodies IgA, IgM, and IgG in serum provides a better serological testing with improved sensitivity and specificity. Data of IgA, IgM, and IgG responses in blood of COVID-19 patients may provide novel insight for the monitoring and treatments of COVID-19. The kits are also suitable for epidemiological studies and vaccine validations.
Cited by 32 publications.
Field of study: Medicine