The main therapeutic intervention for snakebite envenomation relies on the century-old approach of injecting victims with animal-derived polyclonal antiserum. Animal immunisation generates high affinity antibodies and undoubtedly saves lives but the use of immune antiserum has a number of limitations around consistency, redundancy and immunogenicity. Recombinant antibody technology will allow the capture, sequencing and characterisation of the monoclonal antibody repertoire arising from immunisation. Furthermore, the resulting high affinity antibodies will be made more human-like by fusing animal-derived variable domains with human constant domains (chimeric antibodies). This project will generate phage display libraries from horses and llamas immunised with venoms of 4 sub-saharan African snakes represented in the co-applicants antivenom EchiTab-Plus_ICP. We will generate antibody panels by phage selection, screening and sequencing. This resolution of the immune repertoire to a complex venom into its monoclonal components essentially transforms the problem into one of deconvolution. Affinity capture-mass spectrometry will be used to identify the target of thousands of individual antibodies based on their distinct mass-defined target. Following triage based on binding profiles, antibodies to individual targets will be expressed as chimeric antibodies and validated using in vitro and in vivo animal models of envenomation towards generation of life-saving, chimeric antibody cocktails.

Animal-derived antivenoms are the mainstay in the therapy of snakebite envenoming. There is an urgent need to develop knowledge-based protocols for the immunization of horses, as this key aspect of production has lacked research and innovation. This project is aimed at developing protocols for the management of horses used for immunization with venoms in a pilot farm. The following aspects will be investigated: (1) Evaluation of feeding protocols; (2) veterinary care and management aimed at minimizing the deleterious effects of venoms; (3) selection of the most appropriate adjuvants for immunization and development of new immunization schemes for generating high antibody titers; (4) design of bleeding protocols providing a high yield of plasma while not affecting the overall condition of horses. The project is also aimed at selecting the best combination of venoms from African snakes in order to generate a polyspecific antivenom of wide neutralizing coverage, as well as to device ways to improve the antibody titers against poorly immunogenic low molecular mass neurotoxins from snake venoms. In order to apply the principle of 3Rs (Replacement, Reduction and Refinement) in the assessment of antivenom potency, in vitro tests will be evaluated for their correlation with in vivo toxicity assays.