Severe Acute Respiratory Syndrome Coronavirus 2−Specific Antibody Responses in Coronavirus Disease Patients

TLDR

SARS‑CoV‑2 emerged as a global pandemic, and while molecular diagnostics were rapidly developed, reliable serologic assays are still lacking and are urgently needed for contact tracing, reservoir identification, and epidemiologic studies. The authors aimed to develop serologic assays to detect SARS‑CoV‑2 neutralizing, spike‑protein–specific, and nucleocapsid‑specific antibodies. They validated these assays using serum from PCR‑confirmed SARS‑CoV‑2 patients, individuals with other coronaviruses or respiratory infections, testing various antigens in in‑house and commercial ELISAs. Most PCR‑confirmed patients seroconverted within two weeks, commercial S1 IgG/IgA ELISAs showed lower specificity and variable sensitivity—IgA being more sensitive—making the validated assays useful for diagnostics, seroepidemiology, and vaccine evaluation.

Abstract

Abstract A new coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has recently emerged to cause a human pandemic. Although molecular diagnostic tests were rapidly developed, serologic assays are still lacking, yet urgently needed. Validated serologic assays are needed for contact tracing, identifying the viral reservoir, and epidemiologic studies. We developed serologic assays for detection of SARS-CoV-2 neutralizing, spike protein–specific, and nucleocapsid-specific antibodies. Using serum samples from patients with PCR-confirmed SARS-CoV-2 infections, other coronaviruses, or other respiratory pathogenic infections, we validated and tested various antigens in different in-house and commercial ELISAs. We demonstrated that most PCR-confirmed SARS-CoV-2–infected persons seroconverted by 2 weeks after disease onset. We found that commercial S1 IgG or IgA ELISAs were of lower specificity, and sensitivity varied between the 2 assays; the IgA ELISA showed higher sensitivity. Overall, the validated assays described can be instrumental for detection of SARS-CoV-2–specific antibodies for diagnostic, seroepidemiologic, and vaccine evaluation studies.