Study on the expression levels of antibodies against SARS-CoV-2 at different period of disease and its related factors in 192 cases of COVID-19 patients
Background: In 2020 the current outbreak of Coronavirus Disease 2019(COVID-19) has constituted a global pandemic. But the question about the immune mechanism of patients with COVID-19 is unclear and cause particular concern to the world. Here, we launched a follow-up analysis of antibodies against SARS-CoV-2 of 192 COVID-19 patients, aiming to depict a kinetics profile of antibodies against SARS-CoV-2 and explore the related factors of antibodies expression against SARS-CoV-2 in COVID-19 patient. Methods: A total of 192 COVID-19 patients enrolled in the designated hospital of Guangzhou , Guangzhou Eighth People's Hospital, from January to February 2020 were selected as the study cohort. A cohort of 130 COVID-19 suspects who had been excluded from SARS-CoV-2 infected by negative RT-PCR result and 209 healthy people were enrolled in this study. Detection of IgM and IgG against SARS-CoV-2 were performed by Chemiluminescence immunoassay in different groups . Results: It has been found that the seroconversion time of IgM against SARS-CoV-2 in most patients was 5-10 days after the symptoms onset , and then rose rapidly, reaching a peak around 2 to 3 weeks, and the median peak concentration was 2.705 AU / mL. The peak of IgM maintained within one week, and then enters the descending channel. IgG seroconverted later than or synchronously with IgM, reaching peaks around 3 to 4 weeks.The median peak concentration was 33.998AU / ml,which was higher than that of IgM . IgM titers begins to gradually decrease after reaching the peak in the 4th week, after the 8th week, a majority of IgM in patient's serum started to turn negative. On the contrary, titers of IgG began to decline slightly after the fifth week, and more than 90% of results of patients were positive after 8 weeks. Additionally, the concentration of antibodies positively correlated with the severity of the disease and the duration of virus exist in host. Conclusion: We depict a kinetics profile of antibodies against SARS-CoV-2 in COVID-19 patients and found out that the levels of antibodies were related to the disease severity,age, gender and virus clearance or continuous proliferation of COVID-19 patients.