COVID-19 diagnosis and study of serum SARS-CoV-2 specific IgA, IgM and IgG by a quantitative and sensitive immunoassay

Huan Ma; Weihong Zeng; Hongliang He; Dan Zhao; Yunru Yang; Dehua Jiang; Peigen Zhou; Yingjie Qi; Weihuang He; Changcheng Zhao; Ruting Yi; Xiaofang Wang; Bo Wang; Yuanhong Xu; Yun Yang; Arnaud John Kombe Kombe; Chengchao Ding; Jiajia Xie; Yong Gao; Linzhao Cheng; Yajuan Li; Xiaoling Ma; Tengchuan Jin

Interpretation 79 Our immunoassay of measuring SARS-CoV-2 specific antibodies IgA, IgM, and IgG in serum provides 80 a better serological testing with improved sensitivity and specificity. Data of IgA, IgM, and IgG responses 81 in blood of COVID-19 patients may provide novel insight for the monitoring and treatments of COVID-82 a sensitivity below 70%. 9-13 Therefore, there is an urgent need for more reliable and rapid diagnostic 126 methods to screen SARS-CoV-2 infected people including those who do not have overt symptoms. A 127 serological test of virus-induced antibody production has unique advantages in clinical diagnostics, 128 especially for identifying people who acquired immunity against pathogens without noticeable 129 symptoms. 14 When the virus invades host, the body produces large amounts of immunoglobulin (Ig) by 130 the immune system and released into blood, among them, IgG, IgM, and IgA isotypes. 15 It has been 131 widely believed that IgM is the first antibody to be transiently synthesized in response to the virus 132 invasion. 15 IgG is a major class of immunoglobulins found in the blood, comprising 75% of total serum 133 immunoglobulins and has long-term immunity and immunological memory. 15, 16 Therefore, a 134 combination of IgM and IgG has been used in various serological tests for detecting infection of SARS-