Humoral response to SARS‐CoV‐2 and seasonal coronaviruses in COVID‐19 patients

We used enzyme‐linked immunoassay methods to measure the prevalence and the levels of antibody responses to the nucleocapsid (N) protein of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) and four seasonal human coronaviruses (HCoV‐OC43, HCoV‐HKU1, HCoV 229E, and HCoV‐NL63) in a cohort of 115 convalescent plasma donors infected with SARS‐CoV‐2 (1–61 days after symptom onset) compared to antibody levels in 114 individuals with no evidence of a recent infection with SARS‐CoV‐2. In the humoral response to the four seasonal coronaviruses, only HCoV‐HKU1‐ and HCoV‐229E‐assays showed slightly elevated antibody levels in the COVID group compared to the control group. While in the COVID‐group the levels of SARS‐CoV‐2 antibodies correlated significantly with disease severity, no association was found in the levels of antibodies against the seasonal coronaviruses. The most striking result in both groups was that the levels of antibodies against all tested coronaviruses, including the new SARS‐CoV‐2 showed a highly significant correlation with each other. There seems to be an individual predisposition to a weaker or stronger humoral immune response against all known seasonal human coronaviruses including the new SARS‐CoV‐2, which could lead to a definition of low and high responders against human coronaviruses with potential impact on the assessment of postinfection antibody levels and protection.