The emergence of the novel human coronavirus SARS-CoV-2 in Wuhan, China has caused a worldwide epidemic of respiratory disease (COVID-19). Vaccines and targeted therapeutics for treatment of this ...disease are currently lacking. Here we report a human monoclonal antibody that neutralizes SARS-CoV-2 (and SARS-CoV) in cell culture. This cross-neutralizing antibody targets a communal epitope on these viruses and may offer potential for prevention and treatment of COVID-19.
The coronavirus spike glycoprotein, located on the virion surface, is the key mediator of cell entry and the focus for development of protective antibodies and vaccines. Structural studies show ...exposed sites on the spike trimer that might be targeted by antibodies with cross-species specificity. Here we isolated two human monoclonal antibodies from immunized humanized mice that display a remarkable cross-reactivity against distinct spike proteins of betacoronaviruses including SARS-CoV, SARS-CoV-2, MERS-CoV and the endemic human coronavirus HCoV-OC43. Both cross-reactive antibodies target the stem helix in the spike S2 fusion subunit which, in the prefusion conformation of trimeric spike, forms a surface exposed membrane-proximal helical bundle. Both antibodies block MERS-CoV infection in cells and provide protection to mice from lethal MERS-CoV challenge in prophylactic and/or therapeutic models. Our work highlights an immunogenic and vulnerable site on the betacoronavirus spike protein enabling elicitation of antibodies with unusual binding breadth.
Human coronavirus OC43 is a globally circulating common cold virus sustained by recurrent reinfections. How it persists in the population and defies existing herd immunity is unknown. Here we focus ...on viral glycoprotein S, the target for neutralizing antibodies, and provide an in-depth analysis of its antigenic structure. Neutralizing antibodies are directed to the sialoglycan-receptor binding site in S1
domain, but, remarkably, also to S1
. The latter block infection yet do not prevent sialoglycan binding. While two distinct neutralizing S1
epitopes are readily accessible in the prefusion S trimer, other sites are occluded such that their accessibility must be subject to conformational changes in S during cell-entry. While non-neutralizing antibodies were broadly reactive against a collection of natural OC43 variants, neutralizing antibodies generally displayed restricted binding breadth. Our data provide a structure-based understanding of protective immunity and adaptive evolution for this endemic coronavirus which emerged in humans long before SARS-CoV-2.
Abstract Porcine deltacoronavirus (PDCoV) is an emerging enteric pathogen that has recently been detected in humans. Despite this zoonotic concern, the antigenic structure of PDCoV remains unknown. ...The virus relies on its spike (S) protein for cell entry, making it a prime target for neutralizing antibodies. Here, we generate and characterize a set of neutralizing antibodies targeting the S protein, shedding light on PDCoV S interdomain crosstalk and its vulnerable sites. Among the four identified antibodies, one targets the S1A domain, causing local and long-range conformational changes, resulting in partial exposure of the S1B domain. The other antibodies bind the S1B domain, disrupting binding to aminopeptidase N (APN), the entry receptor for PDCoV. Notably, the epitopes of these S1B-targeting antibodies are concealed in the prefusion S trimer conformation, highlighting the necessity for conformational changes for effective antibody binding. The binding footprint of one S1B binder entirely overlaps with APN-interacting residues and thus targets a highly conserved epitope. These findings provide structural insights into the humoral immune response against the PDCoV S protein, potentially guiding vaccine and therapeutic development for this zoonotic pathogen.
Senescence, the irreversible cell cycle arrest of damaged cells, is accompanied by a deleterious pro-inflammatory senescence-associated secretory phenotype (SASP). Senescence and the SASP are major ...factors in aging, cancer, and degenerative diseases, and interfere with the expansion of adult cells in vitro, yet little is known about how to counteract their induction and deleterious effects. Paracrine signals are increasingly recognized as important senescence triggers and understanding their regulation and mode of action may provide novel opportunities to reduce senescence-induced inflammation and improve cell-based therapies. Here, we show that the signalling protein WNT3A counteracts the induction of paracrine senescence in cultured human adult mesenchymal stem cells (MSCs). We find that entry into senescence in a small subpopulation of MSCs triggers a secretome that causes a feed-forward signalling cascade that with increasing speed induces healthy cells into senescence. WNT signals interrupt this cascade by repressing cytokines that mediate this induction of senescence. Inhibition of those mediators by interference with NF-κB or interleukin 6 signalling reduced paracrine senescence in absence of WNT3A and promoted the expansion of MSCs. Our work reveals how WNT signals can antagonize senescence and has relevance not only for expansion of adult cells but can also provide new insights into senescence-associated inflammatory and degenerative diseases.
The Middle-East respiratory syndrome coronavirus (MERS-CoV) is a zoonotic virus that causes severe and often fatal respiratory disease in humans. Efforts to develop antibody-based therapies have ...focused on neutralizing antibodies that target the receptor binding domain of the viral spike protein thereby blocking receptor binding. Here, we developed a set of human monoclonal antibodies that target functionally distinct domains of the MERS-CoV spike protein. These antibodies belong to six distinct epitope groups and interfere with the three critical entry functions of the MERS-CoV spike protein: sialic acid binding, receptor binding and membrane fusion. Passive immunization with potently as well as with poorly neutralizing antibodies protected mice from lethal MERS-CoV challenge. Collectively, these antibodies offer new ways to gain humoral protection in humans against the emerging MERS-CoV by targeting different spike protein epitopes and functions.
Monoclonal antibodies are an increasingly important tool for prophylaxis and treatment of acute virus infections like SARS-CoV-2 infection. However, their use is often restricted due to the time ...required for development, variable yields and high production costs, as well as the need for adaptation to newly emerging virus variants. Here we use the genetically modified filamentous fungus expression system Thermothelomyces heterothallica (C1), which has a naturally high biosynthesis capacity for secretory enzymes and other proteins, to produce a human monoclonal IgG1 antibody (HuMab 87G7) that neutralises the SARS-CoV-2 variants of concern (VOCs) Alpha, Beta, Gamma, Delta, and Omicron. Both the mammalian cell and C1 produced HuMab 87G7 broadly neutralise SARS-CoV-2 VOCs in vitro and also provide protection against VOC Omicron in hamsters. The C1 produced HuMab 87G7 is also able to protect against the Delta VOC in non-human primates. In summary, these findings show that the C1 expression system is a promising technology platform for the development of HuMabs in preventive and therapeutic medicine.
Objective Mesothelin (MSLN) is an attractive target for anticancer therapeutics and bioimaging reagents that utilize antibodies. This study was aimed at developing a novel human anti-MSLN ...single-domain antibody that exclusively binds to the membrane-attached MSLN using transgenic mice generating human heavy-chain-only antibodies (HCAbs) and exploring the resulting HCAbs as imaging tools. Methods We introduced a doxycycline-inducible human MSLN gene in genetically modified mice expressing human HCAbs. This new method of non-invasive immunization by antigen induction results in MSLN antigen production in its native conformation on the cell surface. Screening of 2,000 HCAbs from the resulting immune library yielded numerous binders, from which we chose 19G6 as the lead antibody. This antibody was 111 Indium radiolabeled and tested in a xenotransplantation tumor model with OVCAR-3 cells. Results The 19G6 antibody shows nanomolar affinity toward membrane-bound MSLN and does not recognize soluble MSLN. The human MSLN-positive tumors were visualized in an in vivo mouse model. The non-labeled antibody prevented binding when provided in excess, showing tumor specificity. Conclusion 19G6 with a human Fc is a promising tumor-cell tracer in vivo . This HCAb can also be engineered into a smaller and shorter-lived tracer (only the VH domain) or combined with other target-binding domains to form multispecific modalities for tumor immunotherapy.
The ongoing evolution of SARS-CoV-2 has resulted in the emergence of Omicron, which displays notable immune escape potential through mutations at key antigenic sites on the spike protein. Many of ...these mutations localize to the spike protein ACE2 receptor binding domain, annulling the neutralizing activity of therapeutic antibodies that were effective against other variants of concern (VOCs) earlier in the pandemic. Here, we identified a receptor-blocking human monoclonal antibody, 87G7, that retained potent in vitro neutralizing activity against SARS-CoV-2 variants including the Alpha, Beta, Gamma, Delta, and Omicron (BA.1/BA.2) VOCs. Using cryo-electron microscopy and site-directed mutagenesis experiments, we showed that 87G7 targets a patch of hydrophobic residues in the ACE2-binding site that are highly conserved in SARS-CoV-2 variants, explaining its broad neutralization capacity. 87G7 protected mice and hamsters prophylactically against challenge with all current SARS-CoV-2 VOCs and showed therapeutic activity against SARS-CoV-2 challenge in both animal models. Our findings demonstrate that 87G7 holds promise as a prophylactic or therapeutic agent for COVID-19 that is more resilient to SARS-CoV-2 antigenic diversity.
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