Influential factor and trend of specific IgG antibody titer in coronavirus disease 2019 convalescents.

Wu, Chenggao; Liu, Wei; Li, Guoliang; Zhang, Zhanglin; Xiao, Kun; LE, Aiping

OBJECTIVES To explore the influential factors and titer trend of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) specific IgG antibody in convalescent patients with coronavirus disease 2019 (COVID-19), and to provide theoretical basis for the feasibility of clinical treatment of convalescent plasma. METHODS Colloidal gold immunochromatography assay was used to detect the SARS-CoV-2 specific IgG antibody and its titer in 113 convalescent patients with COVID-19 who were followed up from February 19, 2020 to April 6, 2020. The basic characteristics and treatment factors of patients in the high titer group (antibody titer≥1꞉160, n=22) and the low titer group (antibody titer <1꞉160, n=91) were analyzed. The IgG antibody titer in the high titer group was continuously monitored and the trend of titer was analyzed. RESULTS The difference in the clinical type of COVID-19, onset time, first admission C-reactive protein, absolute value of lymphocyte, absolute value of CD19+CD3- lymphocytes, and the treatment of glucocorticoid were not statistically significant between the patients in the high titer group and the low titer group (all P>0.05). The male patients in the high titer group were more than those in the low titer group (P<0.05). The titer of SARS-CoV-2 specific IgG antibody in the high titer group decreased to less than 1꞉160 28 d after discharge. CONCLUSIONS Male COVID-19 patients might be more likely to produce high titer SARS-CoV-2 specific IgG antibodies than female. The peak level of SARS-CoV-2 specific IgG antibody in convalescent patients is maintained for a short period. Using plasma from convalescent COVID-19 patients for treatment should be within 28 d after discharge.