A
severe acute respiratory syndrome (SARS)-like coronavirus (SARS-CoV-2) has recently caused a
pandemic COVID-19 disease that infected more than 25.6 million and killed 852,000 people worldwide. Like the SARS-CoV, SARS-CoV-2 also employs a receptor-binding motif (RBM) of its envelope spike
protein for binding the host
angiotensin-converting enzyme 2 (ACE2) to gain viral entry. Currently, extensive efforts are being made to produce
vaccines against a surface fragment of a SARS-CoV-2, such as the spike
protein, in order to boost protective antibody responses. It was previously unknown how spike
protein-targeting
antibodies would affect
innate inflammatory responses to
SARS-CoV-2 infections. Here we generated a highly purified
recombinant protein corresponding to the RBM of SARS-CoV-2, and used it to screen for cross-reactive
monoclonal antibodies (mAbs). We found two RBM-binding mAbs that competitively inhibited its interaction with human ACE2, and specifically blocked the RBM-induced
GM-CSF secretion in both human monocyte and murine macrophage cultures. Our findings have suggested a possible strategy to prevent SARS-CoV-2-elicited "
cytokine storm", and provided a potentially useful criteria for future assessment of innate immune-modulating properties of various
SARS-CoV-2 vaccines.
ONE SENTENCE SUMMARY: