Plasma collected from 175 COVID-19 recovered patients with mild symptoms were 32 screened using a safe and sensitive pseudotyped-lentiviral-vector-based neutralization 33 assay. Spike-binding antibody in plasma were determined by ELISA using RBD, S1, 34 and S2 proteins of SARS-CoV-2. The levels and the time course of SARS-CoV-2-35 specific NAbs and the spike-binding antibodies were monitored at the same time.
38 SARS-CoV-2 NAbs were unable to cross-reactive with SARS-CoV virus. SARS-CoV-39 2-specific NAbs were detected in patients from day 10-15 after the onset of the disease 40 and remained thereafter. The titers of NAb among these patients correlated with the 41 spike-binding antibodies targeting S1, RBD, and S2 regions. The titers of NAbs were 42 variable in different patients. Elderly and middle-age patients had significantly higher 43 plasma NAb titers (P<0.0001) and spike-binding antibodies (P=0.0003) than young 44 patients. Notably, among these patients, there were ten patients whose NAb titers were 45 under the detectable level of our assay (ID50: < 40); while in contrast, two patients, 46 showed very high titers of NAb, with ID50 :15989 and 21567 respectively. The NAb 47 titers were positive correlated with plasma CRP levels but negative correlated with the 48 lymphocyte counts of patients at the time of admission, indicating an association 49 between humoral response and cellular immune response.
Interpretation 52 The variations of SARS-CoV-2 specific NAbs in recovered COVID-19 patients may 53 raise the concern about the role of NAbs on disease progression. The correlation of 54 NAb titers with age, lymphocyte counts, and blood CRP levels suggested that the 55 interplay between virus and host immune response in coronavirus infections should be 56 further explored for the development of effective vaccine against SARS-CoV-2 virus. 57 Furthermore, titration of NAb is helpful prior to the use of convalescent plasma for 58 prevention or treatment
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