Abstract:
Background. The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in a pandemic of coronavirus disease 2019 (COVID-19). Antibody testing is essential to identify persons exposed to the virus and potentially predicting immunity.
Methods. 183 COVID-19 patients (68 mechanically ventilated) and 41 controls were tested for plasma IgG, IgA and IgM against the SARS-CoV-2 S1, S2, receptor binding domain (RBD) and N proteins using the MILLIPLEX® SARS-CoV-2 Antigen Panels. Plasma cytokines were measured using the MILLIPLEX® MAP Human Cytokine/Chemokine/Growth Factor Panel A.
Results. COVID-19 positive patients had high levels of IgG, IgA and IgM anti-SARS-CoV-2 antibodies against viral proteins. Sensitivity of anti-S1 IgG increased from 60% to 93% one week after symptom onset. S1-IgG and S1-IgA had specificities of 98%. Ventilated COVID-19 patients had higher antibody levels than the COVID-19 patients who were not ventilated. IgG antibody levels against S1 protein had the strongest correlation to days from symptom onset. There were no statistically significant differences in antibodies based on age. We found that patients with the highest IgG levels had the lowest viral load. Finally, there was a correlation of high plasma IL-10 with low anti-SARS-CoV-2 IgG.
Conclusions. Anti-SARS-CoV-2 antibody levels increased within days after symptom onset, achieving >90% sensitivity and specificity within one week, and were highest in patients who were ventilated. Antibody levels were inversely associated with viral load but did not differ by age. The correlation of high IL-10 with low antibody response suggests a potentially suppressive
role of this cytokine in the humoral immune response.
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