Long-term antibody responses and neutralizing activities following SARS-CoV-2 infections have not yet been elucidated. We quantified immunoglobulin M (IgM) and G (IgG) antibodies recognizing the SARS-CoV-2 receptor-binding domain (RBD) of the spike (S) or the nucleocapsid (N) protein, and neutralizing antibodies during a period of six months following COVID-19 disease onset in 349 symptomatic COVID-19 patients, which were among the first world-wide being infected. The positivity rate and magnitude of IgM-S and IgG-N responses increased rapidly. High levels of IgM-S/N and IgG-S/N at 2-3 weeks after disease onset were associated with virus control and IgG-S titers correlated closely with the capacity to neutralize SARS-CoV-2. While specific IgM-S/N became undetectable 12 weeks after disease onset in most patients, IgG-S/N titers showed an intermediate contraction phase, but stabilized at relatively high levels over the six months observation period. At late time points the positivity rates for binding and neutralizing SARS-CoV-2-specific antibodies was still over 70%. Taken together, our data indicate sustained humoral immunity in recovered patients who suffer from symptomatic COVID-19, suggesting prolonged immunity.
Competing Interest Statement
The authors have declared no competing interest.
This work is supported by the National Science and Technology Major Project for Infectious Diseases of China (2018ZX10302206, 2018ZX10723203, and 2017ZX10304402-002-005);the Fundamental Research Funds for the Central Universities (2020kfyXGYJ016, 2020kfyXGYJ028, and 2020kfyXGYJ046); the Tongji-Rongcheng Center for Biomedicine, Huazhong University of Science and Technology, the Medical Faculty of the University of Duisburg-Essen, and Stiftung Universitatsmedizin Essen, University Hospital Essen, Germany.
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