Concentration of IgG against the Spike Receptor-Binding Domain predicts the viral neutralization activity of convalescent plasma and serum against SARS-CoV-2

SARS-CoV-2 is the virus responsible for the Covid-19 pandemic, due to its rapid propagation and the initial lack of vaccines or appropriate treatments. Nowadays, despite different vaccines available, the main treatments are palliative, focused on supplemental oxygen and anti-inflammatory therapy. Passive immunization could be an effective and economic treatment once standarized. It consists of the transfer of pathogen-specific antibodies to patients whose immune system has not originated a response yet. The donors’ antibodies neutralize and attenuate pathogen replication. Besides, an antibody against the Receptor-Binding Domain of Spike (RBD) would block the interaction of the virus with ACE2 and its entry in the cell. Here, an in-house RBG IgG ELISA test has been validated using a cohort of more than 320 samples of convalescent plasma and serum and adapted to quantify the concentration of plasma RBD IgG and its correlation with the SARS-CoV-2 neutralizing activity in vitro.