Coronaviruses (CoVs) are enveloped, single positive-strand RNA viruses belonging to the large subfamily Coronavirinae, which can infect mammals and several other animals.The continued spread of coronavirus disease 2019 (COVID-19) has prompted widespread concern around the world, and the World Health Organization (WHO), on 11 March 2020, declared COVID-19 a pandemic. Studies on severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) showed that virus-specific antibodies were detectable in 80-100% of patients at 2 weeks after symptom onset. Currently, the antibody responses against SARS-CoV-2 remain poorly understood and the clinical utility of serological testing is unclear Little is known about the kinetics, tissue distribution, cross-reactivity and neutralization antibody response in COVID-19 patients .
The seropositivity rate of both IgM and IgG responses after onset and recovery of disease, and in the context of both N protein and S protein has not been clarified. The kinetics of antibody responses in critical cases or ICU patients has not been reported, and no studies have suggested whether antibody response is associated with disease prognosis
