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Snakebite envenoming continues to claim many lives across the globe, necessitating the development of improved therapies. To this end, human monoclonal antibodies may possess advantages over current plasma-derived antivenoms by offering superior safety and improved neutralization capacity. However, as new antivenom products may need to be polyvalent, i.e., target multiple different snake species, without dramatically increasing dose or cost of manufacture, such monoclonal antibodies need to be broadly-neutralizing. Here, we report the establishment of a pipeline for the discovery of high affinity broadly-neutralizing human monoclonal antibodies. We further demonstrate its utility by discovering an antibody that can prevent lethality induced by N. kaouthia whole venom at an unprecedented low molar ratio of one antibody per toxin, and which also prolongs survival of mice injected with Dendroaspis polylepis or Ophiophagus hannah whole venoms.

The monocled cobra (Naja kaouthia) is one of the most feared snakes in Southeast Asia. It is a highly dangerous species with a potent venom deriving its toxicity predominantly from abundant long-chain α-neurotoxins. The only specific treatment for snakebite envenoming is antivenom, which is based on animal-derived polyclonal antibodies. Despite the lifesaving importance of these medicines over the past 120 years, and their ongoing role in combating snakebite disease, major limitations in safety, supply consistency, and efficacy creates a need for a new generation of improved treatments based on modern biotechnological techniques. Here, we describe the initial discovery and subsequent optimization of a recombinant human monoclonal immunoglobin G (IgG) antibody against α-cobratoxin using phage display technology. Affinity maturation of the parental antibody by light chain-shuffling resulted in an 8-fold increase in affinity, translating to a significant increase in in vitro neutralization potency and in vivo efficacy. While the parental antibody prolonged survival of mice challenged with purified α-cobratoxin, the optimized antibody prevented lethality when incubated with N. kaouthia whole venom prior to intravenous injection. This study is the first to demonstrate neutralization of whole snake venom by a single recombinant monoclonal antibody. Importantly, this suggests that for venoms whose toxicity relies on a single predominant toxin group, such as that of N. kaouthia, as little as one monoclonal antibody may be sufficient to prevent lethality, thus providing a tantalizing prospect of bringing recombinant antivenoms based on human monoclonal or oligoclonal antibodies to the clinic.One Sentence SummaryA recombinant human monoclonal immunoglobulin G antibody, discovered and optimized using in vitro methods, was demonstrated to neutralize the lethal effect of whole venom from the monocled cobra in mice via abrogation of α-neurotoxin-mediated neurotoxicity.

Passive immunization using monoclonal antibodies will play a vital role in the fight against COVID-19. The recent emergence of viral variants with reduced sensitivity to some current antibodies and vaccines highlights the importance of broad cross-reactivity. This study describes deep-mining of the antibody repertoires of hospitalized COVID-19 patients using phage display technology and B cell receptor (BCR) repertoire sequencing to isolate neutralizing antibodies and gain insights into the early antibody response. This comprehensive discovery approach has yielded a panel of potent neutralizing antibodies which bind distinct viral epitopes including epitopes conserved in SARS-CoV-1. Structural determination of a non-ACE2 receptor blocking antibody reveals a previously undescribed binding epitope, which is unlikely to be affected by the mutations in any of the recently reported major viral variants including B.1.1.7 (from the UK), B.1.351 (from South Africa) and B.1.1.28 (from Brazil). Finally, by combining sequences of the RBD binding and neutralizing antibodies with the B cell receptor repertoire sequencing, we also describe a highly convergent early antibody response. Similar IgM-derived sequences occur within this study group and also within patient responses described by multiple independent studies published previously.

We thank the authors for their commentary1 on our article which was recently published in the Annals of Rheumatic Diseases .2 Cutolo et al write an extended discussion of the study, in which we describe the development of therapeutic monoclonal antibodies that block the pro-inflammatory activity of the fibrinogen-like globe (FBG) domain of tenascin-C, and the efficacy of these antibodies in preventing disease progression in preclinical models of rheumatoid arthritis (RA). The commentary includes a detailed summary of the autoantibody response to a citrullinated epitope (cTNC5) within the FBG domain of tenascin-C which arises very early during the development of RA, and which can also be detected in around one in five people at risk of developing RA. As highlighted by the authors, the questions around how the response …

The two elapids, the black mamba (Dendroaspis polylepis) and the monocled cobra (Naja kaouthia) are notorious for their bite, which each year causes a substantial share of the severe envenomings that occur in sub Saharan Africa and Southeast Asia, respectively. Through a combined toxicovenomics and the phage display selection approach, monoclonal fully human IgGs were discovered and assessed for their ability to neutralize medically relevant toxins from the aforementioned snakes in vivo. The discovered monoclonal human IgGs were expressed in mammalian Expi-293 cells and tested in CD-1 mice using two different routes of administration. Initially, IgGs were incubated for 30 min at 37°C together with their target toxins in different molar ratios (mol toxin: mol IgG of 1:3 to 1:8) and then administered either intracerebroventricularly (i.c.v.) (dendrotoxins) using a toxin dose of 0.5 μg or intravenously (i.v.) (α-cobratoxin) using a toxin dose of 4 μg to evaluate the neutralization potential of the IgGs. The survival of mice administered with lethal doses of elapid toxins was substantially prolonged by the monoclonal human IgGs. Hence, we report the discovery of monoclonal fully human IgGs that are able to neutralize snake toxins in vivo. Additionally, one of the tested human IgGs was able to prolong survival both against its cognate toxin (α-cobratoxin) and against whole venom from N. kaouthia. This demonstrates the applicability of the Toxicity Score for identifying medically relevant toxins in a venom and that α-cobratoxin is one of the key toxic components of N. kaouthia venom.

The growth and motility factor Hepatocyte Growth Factor/Scatter Factor (HGF/SF) and its receptor, the product of the MET proto-oncogene, promote invasion and metastasis of tumor cells and have been considered potential targets for cancer therapy. We generated a new Met-blocking antibody which binds outside the ligand-binding site, and determined the crystal structure of the Fab in complex with its target, which identifies the binding site as the Met Ig1 domain. The antibody, 107_A07, inhibited HGF/SF-induced cell migration and proliferation in vitro and inhibited growth of tumor xenografts in vivo. In biochemical assays, 107_A07 competes with both HGF/SF and its truncated splice variant NK1 for MET binding, despite the location of the antibody epitope on a domain (Ig1) not reported to bind NK1 or HGF/SF. Overlay of the Fab-MET crystal structure with the InternalinB-MET crystal structure shows that the 107_A07 Fab comes into close proximity with the HGF/SF-binding SEMA domain when MET is in the “compact”, InternalinB-bound conformation, but not when MET is in the “open” conformation. These findings provide further support for the importance of the “compact” conformation of the MET extracellular domain, and the relevance of this conformation to HGF/SF binding and signaling.

Despite the wealth of commercially available antibodies to human proteins, research is often hindered by their inconsistent validation, their poor performance and the inadequate coverage of the proteome. These issues could be addressed by systematic, genome-wide efforts to generate and validate renewable protein binders. We report a multicenter study to assess the potential of hybridoma and phage-display technologies in a coordinated large-scale antibody generation and validation effort. We produced over 1,000 antibodies targeting 20 SH2 domain proteins and evaluated them for potency and specificity by enzyme-linked immunosorbent assay (ELISA), protein microarray and surface plasmon resonance (SPR). We also tested selected antibodies in immunoprecipitation, immunoblotting and immunofluorescence assays. Our results show that high-affinity, high-specificity renewable antibodies generated by different technologies can be produced quickly and efficiently. We believe that this work serves as a foundation and template for future larger-scale studies to create renewable protein binders.

Snakebite envenoming is a major cause of death and morbidity in tropical parts of the world. Current therapies are based on animal-­derived antisera that are associated with a high degree of immunogenicity, high cost, and batch-to-batch variation. Here, we report the results of our ongoing efforts of developing the world’s first fully recombinant antivenom based on human IgGs targeting the key toxins from the notorious black mamba (Dendroaspis polylepis).