The rapid spread of SARS-CoV-2 has a significant impact on global health, travel and economy. Therefore, preventative and therapeutic measures are urgently needed. Here, we isolated monoclonal antibodies from three convalescent COVID-19 patients using a SARS-CoV-2 stabilized prefusion spike protein. These antibodies had low levels of somatic hypermutation and showed a strong enrichment in VH1-69, VH3-30-3 and VH1-24 gene usage. A subset of the antibodies were able to potently inhibit authentic SARS-CoV-2 infection as low as 0.007 μg/mL. Competition and electron microscopy studies illustrate that the SARS-CoV-2 spike protein contains multiple distinct antigenic sites, including several receptor-binding domain (RBD) epitopes as well as non-RBD epitopes. In addition to providing guidance for vaccine design, the antibodies described here are promising candidates for COVID-19 treatment and prevention.

The rapid spread of SARS-CoV-2 has a significant impact on global health, travel and economy. Therefore, preventative and therapeutic measures are urgently needed. Here, we isolated neutralizing antibodies from convalescent COVID-19 patients using a SARS-CoV-2 stabilized prefusion spike protein. Several of these antibodies were able to potently inhibit live SARS-CoV-2 infection at concentrations as low as 0.007 µg/mL, making them the most potent human SARS-CoV-2 antibodies described to date. Mapping studies revealed that the SARS-CoV-2 spike protein contained multiple distinct antigenic sites, including several receptorbinding domain (RBD) epitopes as well as previously undefined non-RBD epitopes. In addition to providing guidance for vaccine design, these mAbs are promising candidates for treatment and prevention of COVID-19.

Highlights d X-ray and EM structures of cross-neutralizing antibody COVA1-16 with SARS-CoV-2 RBD d COVA1-16 binding to SARS-CoV-2 RBD is dominated by CDR H3 d COVA1-16 binds to a highly conserved non-RBS epitope but still competes with ACE2 d IgG avidity is the key for the cross-neutralization activity of COVA1-16

Most antibodies isolated from COVID-19 patients are specific to SARS-CoV-2. COVA1-16 is a relatively rare antibody that also cross-neutralizes SARS-CoV. Here we determined a crystal structure of COVA1-16 Fab with the SARS-CoV-2 RBD, and a negative-stain EM reconstruction with the spike glycoprotein trimer, to elucidate the structural basis of its cross-reactivity. COVA1-16 binds a highly conserved epitope on the SARS-CoV-2 RBD, mainly through a long CDR H3, and competes with ACE2 binding due to steric hindrance rather than epitope overlap. COVA1-16 binds to a flexible up conformation of the RBD on the spike and relies on antibody avidity for neutralization. These findings, along with structural and functional rationale for the epitope conservation, provide a blueprint for development of more universal SARS-like coronavirus vaccines and therapies.

Highlights d Two-component protein nanoparticles display multiple copies of the SARS-CoV-2 spike d Spike protein nanoparticles enhance cognate B cell activation in vitro d Vaccination induces potent neutralization in mice, rabbits, and cynomolgus macaques d Vaccination protects macaques against a high-dose SARS-CoV-2 challenge

34The induction of broad and potent immunity by vaccines is the key focus of research efforts 35 aimed at protecting against HIV-1 infection. Soluble native-like HIV-1 envelope glycoproteins 36 have shown promise as vaccine candidates as they can induce potent autologous neutralizing 37 responses in rabbits and non-human primates. In this study, monoclonal antibodies were isolated 38 and characterized from rhesus macaques immunized with the BG505 SOSIP.664 trimer to better 39 understand vaccine-induced antibody responses. Our studies reveal a diverse landscape of 40 antibodies recognizing immunodominant strain-specific epitopes and non-neutralizing neo-41 epitopes. Additionally, we isolated a subset of mAbs against an epitope cluster at the gp120-gp41 42 interface that recognize the highly conserved fusion peptide and the glycan at position 88 and 43 have characteristics akin to several human-derived broadly neutralizing antibodies. 44 (nucleotide level) was 6.4% (range: 2.1%-10.2%) with an average HC complementarity-126 determining region 3 (CDR-H3) length of 15 amino acids (aa) (range: 7-23) ( Table S2). The rh1987 127 KC mAbs utilized HC variable genes from the IGHV3 and IGHV4 families and predominantly used 128 KC V genes from the IGKV1 family (Table S2). All of the rh1987 KC mAbs had a CDR-L3 length of 9 129 aa and their average KC SHM (nucleotide level) was 4.7% (range: 2.6%-6.0%) (Table S2). A single 130 clonal family with 4 members (RM19A) was detected among rh1987 KC mAbs with members 131 isolated from both week 22 and week 25 samples (Table S2). The rh1987 LC mAbs used HC V 132 genes from the IGHV1, IGHV3 and IGHV4 families and LC V genes mainly from the IGLV2 gene 133 family ( Table S2). The rh1987 LC mAbs had an average CDR-L3 length of 10 aa (range: 9-11) with 134 an average LC SHM (nucleotide level) of 3.8% (range: 0.9%-10.6%) (Table S2). Two clonal families 135

The induction of broad and potent immunity by vaccines is the key focus of research efforts aimed at protecting against HIV-1 infection. Soluble native-like HIV-1 envelope glycoproteins have shown promise as vaccine candidates as they can induce potent autologous neutralizing responses in rabbits and non-human primates. In this study, monoclonal antibodies were isolated and characterized from rhesus macaques immunized with the BG505 SOSIP.664 trimer to better understand vaccine-induced antibody responses. Our studies reveal a diverse landscape of antibodies recognizing immunodominant strain-specific epitopes and non-neutralizing neo-epitopes. Additionally, we isolated a subset of mAbs against an epitope cluster at the gp120-gp41 interface that recognize the highly conserved fusion peptide and the glycan at position 88 and have characteristics akin to several humanderived broadly neutralizing antibodies.

Highlights d Two-component protein nanoparticles display multiple copies of the SARS-CoV-2 spike d Spike protein nanoparticles enhance cognate B cell activation in vitro d Vaccination induces potent neutralization in mice, rabbits, and cynomolgus macaques d Vaccination protects macaques against a high-dose SARS-CoV-2 challenge