To the Editor: Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is one of the greatest modem public health crises. COVID-19-specific treatments, while being studied, are not yet readily available. We examined whether commercial prepandemic intravenous immunoglobulin (IVIG) contains cross-reactive antibodies that could bind and neutralize SARS-CoV-2. The receptor-binding domain (RBD), contained within the SI subunit of the coronavirus spike protein, mediates viral entry by binding to the angiotensin-converting enzyme 2 receptor on host cells. The spike protein, including the RBD, is a known target for neutralizing antibodies in natural infection, and shares some epitopes with S proteins from common, circulating strains of human coronaviruses. We took 82 samples from 4 different brands manufactured in the United States and Europe (OctaPharma, Hoboken, NJ; Grifols, Barcelona, Spain and Durham, NC; CSL, Bern, Switzerland) and tested them for SARS-CoV-2 RBD binding using a standard ELISA. We found that all samples demonstrated the presence of cross-reactive antibodies above the negative controls; however, binding activity varied between individual lots and among brands (Fig 1, A).
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