Pitfalls to avoid when using phage display for snake toxins

Revolutionizing snakebite care with novel antivenoms: Breakthroughs and barriers

Snakebite envenoming (SBE) is a global public health concern, primarily due to the lack of effective antivenom for treating snakebites inflicted by medically significant venomous snakes prevalent across various geographic locations. The rising demand for safe, cost-effective, and potent snakebite treatments highlights the urgent need to develop alternative therapeutics targeting relevant toxins. This development could provide promising discoveries to create novel recombinant solutions, leveraging human monoclonal antibodies, synthetic peptides and nanobodies. Such technologies as recombinant DNA, peptide and epitope mapping phage display etc) have the potential to exceed the traditional use of equine polyclonal antibodies, which have long been used in antivenom production. Recombinant antivenom can be engineered to target certain toxins that play a critical role in snakebite pathology. This approach has the potential to produce antivenom with improved efficacy and safety profiles. However, there are limitations and challenges associated with these emerging technologies. Therefore, identifying the limitations is critical for overcoming the associated challenges and optimizing the development of recombinant antivenoms. This review is aimed at presenting a thorough overview of diverse technologies used in the development of recombinant antivenom, emphasizing their limitations and offering insights into prospects for advancing recombinant antivenoms.

Recombinant human scFv antibody fragments against phospholipase A2 from Naja naja and Echis carinatus snake venoms: In vivo neutralization and mechanistic insights

Snake envenomation results in a range of clinical sequelae, and widely used animal-based conventional antivenoms exhibit several limitations including the adverse immunological effects in human snake bite victims. Therefore, human monoclonal anti-snake venom antibodies or fragments can be an alternate therapy for overcoming the existing limitations. We developed venom-neutralizing humanized scFv antibodies and analyzed biochemical mechanisms associated with the inhibition of toxicity. Tomlinson I and J human scFv antibody libraries were screened against Naja naja and Echis carinatus venoms, and seven unique scFv antibodies were obtained. Further, specific toxins of snake venom interacting with each of these scFvs were identified, and phospholipase A2 (PLA2) was found to be prominently captured by the phage-anchored scFv antibodies. Our study indicated PLA2 to be one of the abundant toxins in Naja naja and Echis carinatus venom samples. The scFvs binding to PLA2 were used to perform in vivo survival assay using the mouse model and in vitro toxin inhibition assays. scFv N194, which binds to acidic PLA2, protected 50% of mice treated with Naja naja venom. Significant prolongation of survival time and 16% survival were observed in Echis carinatus venom-challenged mice treated with scFv E113 and scFv E10, respectively. However, a combination comprised of an equal amount of two scFvs, E113 and E10, both interacting with basic PLA2, exhibited synergistically enhanced survival of 33% in Echis carinatus venom-challenged mice. No such synergistically enhanced survival was observed in the case of combinatorial treatment with anti-Naja naja scFvs, N194, and N248. These scFvs demonstrated partial inhibition of venom-induced myotoxicity, and E113 also inhibited hemolysis by 50%, which corroborates the enhanced survival during combinatorial treatment in Echis carinatus venom-challenged mice.

Gigavalent Display of Proteins on Monodisperse Polyacrylamide Hydrogels as a Versatile Modular Platform for Functional Assays and Protein Engineering

The assembly of robust, modular biological components into complex functional systems is central to synthetic biology. Here, we apply modular "plug and play" design principles to a solid-phase protein display system that facilitates protein purification and functional assays. Specifically, we capture proteins on polyacrylamide hydrogel display beads (PHD beads) made in microfluidic droplet generators. These monodisperse PHD beads are decorated with predefined amounts of anchors, methacrylate-PEG-benzylguanine (BG) and methacrylate-PEG-chloroalkane (CA), that react covalently with SNAP-/Halo-tag fusion proteins, respectively, in a specific, orthogonal, and stable fashion. Anchors, and thus proteins, are distributed throughout the entire bead volume, allowing attachment of ∼10⁹ protein molecules per bead (⌀ 20 μm) -a higher density than achievable with commercial surface-modified beads. We showcase a diverse array of protein modules that enable the secondary capture of proteins, either noncovalently (IgG and SUMO-tag) or covalently (SpyCatcher, SpyTag, SnpCatcher, and SnpTag), in mono- and multivalent display formats. Solid-phase protein binding and enzymatic assays are carried out, and incorporating the photocleavable protein PhoCl enables the controlled release of modules via visible-light irradiation for functional assays in solution. We utilize photocleavage for valency engineering of an anti-TRAIL-R1 scFv, enhancing its apoptosis-inducing potency ∼50-fold through pentamerization.

Recombinant antibodies against Iranian cobra venom as a new emerging therapy by phage display technology

Background:

The production of antivenom from immunized animals is an established treatment for snakebites; however, antibody phage display technology may have the capacity to delivery results more quickly and with a better match to local need. Naja oxiana, the Iranian cobra, is a medically important species, responsible for a significant number of deaths annually. This study was designed as proof of principle to determine whether recombinant antibodies with the capacity to neutralize cobra venom could be isolated by phage display.

Methods:

Toxic fractions from cobra venom were prepared by chromatography and used as targets in phage display to isolate recombinant antibodies from a human scFv library. Candidate antibodies were expressed in E. coli HB2151 and purified by IMAC chromatography. The selected clones were analyzed in in vivo and in vitro experiments.

Results:

Venom toxicity was contained in two fractions. Around a hundred phage clones were isolated against each fraction, those showing the best promise were G12F3 and G1F4. While all chosen clones showed low but detectable neutralizing effect against Naja oxiana venom, clone G12F3 could inhibit PLA₂ activity.

Conclusion:

Therefore, phage display is believed to have a good potential as an approach to the development of snake antivenom.

Identification of cross-reactive human single-chain variable fragments against phospholipases A2 from Lachesis muta and Bothrops spp venoms

Bushmasters (Lachesis spp) and lancehead vipers (Bothrops spp) are two of the most dangerous snakes found in Latin America. Victims of envenoming by these snakes require urgent administration of antivenom. Here, we report the identification of a small set of broadly neutralizing human monoclonal single-chain variable fragment (scFv) antibodies targeting key phospholipases A₂ from Lachesis and Bothrops spp using phage display technology and demonstrate their in vitro efficacy using a hemolysis assay.

Unity Makes Strength: Exploring Intraspecies and Interspecies Toxin Synergism between Phospholipases A2 and Cytotoxins

Toxin synergism is a complex biochemical phenomenon, where different animal venom proteins interact either directly or indirectly to potentiate toxicity to a level that is above the sum of the toxicities of the individual toxins. This provides the animals possessing venoms with synergistically enhanced toxicity with a metabolic advantage, since less venom is needed to inflict potent toxic effects in prey and predators. Among the toxins that are known for interacting synergistically are cytotoxins from snake venoms, phospholipases A₂ from snake and bee venoms, and melittin from bee venom. These toxins may derive a synergistically enhanced toxicity via formation of toxin complexes by hetero-oligomerization. Using a human keratinocyte assay mimicking human epidermis in vitro, we demonstrate and quantify the level of synergistically enhanced toxicity for 12 cytotoxin/melittin-PLA₂ combinations using toxins from elapids, vipers, and bees. Moreover, by utilizing an interaction-based assay and by including a wealth of information obtained via a thorough literature review, we speculate and propose a mechanistic model for how toxin synergism in relation to cytotoxicity may be mediated by cytotoxin/melittin and PLA₂ complex formation.

In vivo neutralization of dendrotoxin-mediated neurotoxicity of black mamba venom by oligoclonal human IgG antibodies

The black mamba (Dendroaspis polylepis) is one of the most feared snake species of the African savanna. It has a potent, fast-acting neurotoxic venom comprised of dendrotoxins and α-neurotoxins associated with high fatality in untreated victims. Current antivenoms are both scarce on the African continent and present a number of drawbacks as they are derived from the plasma of hyper-immunized large mammals. Here, we describe the development of an experimental recombinant antivenom by a combined toxicovenomics and phage display approach. The recombinant antivenom is based on a cocktail of fully human immunoglobulin G (IgG) monoclonal antibodies capable of neutralizing dendrotoxin-mediated neurotoxicity of black mamba whole venom in a rodent model. Our results show the potential use of fully human monoclonal IgGs against animal toxins and the first use of oligoclonal human IgG mixtures against experimental snakebite envenoming.

Current anti-venoms against black mamba (Dendroaspis polylepis) bites are animal-derived and associated with several limitations. Here, Laustsen and colleagues develop an experimental recombinant anti-venom based on oligoclonal human IgG antibodies and establish its potential protective value in neutralizing dendrotoxin-mediated neurotoxicity using venom challenge in vivo models.

Basics of Antibody Phage Display Technology

Antibody discovery has become increasingly important in almost all areas of modern medicine. Different antibody discovery approaches exist, but one that has gained increasing interest in the field of toxinology and antivenom research is phage display technology. In this review, the lifecycle of the M13 phage and the basics of phage display technology are presented together with important factors influencing the success rates of phage display experiments. Moreover, the pros and cons of different antigen display methods and the use of naïve versus immunized phage display antibody libraries is discussed, and selected examples from the field of antivenom research are highlighted. This review thus provides in-depth knowledge on the principles and use of phage display technology with a special focus on discovery of antibodies that target animal toxins.

Discovery of human scFvs that cross-neutralize the toxic effects of B. jararacussu and C. d. terrificus venoms

Accidents involving venomous snakes are a public health problem worldwide, causing a large number of deaths per year. In Brazil, the majority of accidents are caused by the Bothrops and Crotalus genera, which are responsible for approximately 80% of severe envenoming cases. The cross-neutralization of snake venoms by antibodies is an important issue for development of more effective treatments. Our group has previously reported the construction of human monoclonal antibody fragments towards Bothrops jararacussu and Crotalus durissus terrificus' venoms. This study aimed to select human single-chain variable fragments (scFvs) that recognize both bothropic and crotalic crude venoms following venoms neutralizing capacity in vitro and in vivo. The cross-reactivity of Cro-Bothrumabs were demonstrated by ELISA and in vitro and in vivo experiments showed that a combination of scFvs neutralizes in vitro toxic activities (e.g. indirect hemolysis and plasma-clotting) of crotalic and bothropic venoms as well as prolonged survival time of envenomed animals. Our results may contribute to the development of the first human polyvalent antivenom against Bothrops jararacussu and Crotalus durissus terrificus venoms, overcoming some undesirable effects caused by conventional serotherapy.