Early Anti-SARS-CoV-2 Immunoglobulin G Response May Be Associated with Disease Severity in Patients with COVID-19.

ABSTRACT

Most coronavirus disease 2019 (COVID-19) cases are mild or asymptomatic, and a substantial minority of patients have severe or critical diseases. There are several reports on the potential risk factors of severe disease, but few reports have reported a relationship between antibody titer and severity in Japan. Antibody-dependent enhancement affects disease progression. We evaluated the IgG responses in COVID-19 patients at our tertiary hospital. The IgG index was the measure of interest. We assigned 1.4 as the cutoff value for a positive result based on the specifications by the manufacturer and observed that patients could be categorized into two groups the early elevation of IgG and late elevation of IgG (IgG elevated in the first 7 days ± 2 days or more than 10 days after symptom onset) groups. The former comprised early IgG responders (n = 7) and the latter comprised late IgG responders (n = 14), and they were compared. The C-reactive protein and D-dimer concentrations were significantly higher in the early IgG responders on admission (HD 0). The respiratory rate was also higher. The lymphocytes were significantly fewer on day 7 of hospitalization (HD 7). These results suggest that early production of anti-severe acute respiratory syndrome coronavirus 2 IgG may be associated with clinical indicators of severity.