Potently neutralizing human antibodies that block SARS-CoV-2 receptor binding and protect animals

Abstract

The COVID-19 pandemic is a major threat to global health for which there are only 50 limited medical countermeasures, and we lack a thorough understanding of mechanisms of 51 humoral immunity 1,2 . From a panel of monoclonal antibodies (mAbs) targeting the spike 52 (S) glycoprotein isolated from the B cells of infected subjects, we identified several mAbs 53 that exhibited potent neutralizing activity with IC50 values as low as 0.9 or 15 ng/mL in 54 pseudovirus or wild-type (wt) SARS-CoV-2 neutralization tests, respectively. The most 55 potent mAbs fully block the receptor-binding domain of S (SRBD) from interacting with 56 human ACE2. Competition-binding, structural, and functional studies allowed clustering 57 of the mAbs into defined classes recognizing distinct epitopes within major antigenic sites 58 on the SRBD. Electron microscopy studies revealed that these mAbs recognize distinct 59 conformational states of trimeric S protein. Potent neutralizing mAbs recognizing unique 60 sites, COV2-2196 and COV2-2130, bound simultaneously to S and synergistically 61 neutralized authentic SARS-CoV-2 virus. In two murine models of SARS-CoV-2 infection, 62 passive transfer of either COV2-2916 or COV2-2130 alone or a combination of both mAbs 63 protected mice from severe weight loss and reduced viral burden and inflammation in the 64 lung. These results identify protective epitopes on the SRBD and provide a structure-based 65 framework for rational vaccine design and the selection of robust immunotherapeutic 66 cocktails. 67 68 The S protein of SARS-CoV-2 is the molecular determinant of viral attachment, fusion, and 69 entry into host cells 3 . The cryo-EM structure of a prefusion-stabilized trimeric S protein 70 ectodomain (S2Pecto) for SARS-CoV-2 reveals similar features to that of the SARS-CoV S 71 protein 4 . This type I integral membrane protein and class I fusion protein possesses an N-72

mRNA induced expression of human angiotensin-converting enzyme 2 in mice for the study of the adaptive immune response to severe acute respiratory syndrome coronavirus 2

“…To examine the antibody response directed against SARS-CoV-2, we performed an indirect ELISA against the receptor binding domain (RBD) of the SARS-CoV-2 spike protein, a target of the neutralizing antibody response in both mice and humans [16,[45][46][47]. To quantify the anti-RBD antibody response, we compared the polyclonal sera from naïve Ifnar1 -/mice, to that of the SARS-CoV-2 infected Ifnar1 -/mice transfected with either the hACE2 or GFP mRNA ( Figure 2B).…”

Escape from neutralizing antibodies by SARS-CoV-2 spike protein variants

“…Recent studies have shown that related, potently neutralizing monoclonal antibodies that recognize the SARS-CoV-2 receptor binding domain (RBD) are often elicited in SARS-CoV-2 infection (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). These antibodies have great potential to be clinically impactful in the treatment and prevention of SARS-CoV-2 infection.…”

Epitope-resolved profiling of the SARS-CoV-2 antibody response identifies cross-reactivity with an endemic human CoV

“…This likely accounts for the imperfect correlation between the titers of S-binding antibodies and viral neutralization activity across individuals (Robbiani et al, 2020). Due to its interaction with the host entry receptor (the angiotensin converting enzyme 2 -ACE2), the RBD of S represents the predominant target of vaccination and monoclonal antibody development strategies, and a growing number of antibodies against this domain have been described (Chi et al, 2020;Hansen et al, 2020;Robbiani et al, 2020;Zost et al, 2020). However, the RBD is one of the less conserved regions of the CoV proteome and antibodies against epitopes outside of the RBD have also been shown to have neutralizing activity (Chi et al, 2020;Poh et al, 2020): these may act in various ways, including by preventing important protease cleavage events and/or conformational changes required for successful entry into cells.…”