title: Bioinformatic design of venom toxin-specific antivenom to improve the treatment of snakebite in Africa
Creators: name: Rengifo Ibanez, Maria Camila
Publisher: name: University of Liverpool Repository
Year: 2014

description: Antivenom is the only effective treatment against the systemic effects of snakebite and is currently developed by a century-old immunisation protocol that aims to generate IgGs capable of binding and neutralizing most (if not all) of the venom toxins. However, snake venoms comprise more than a hundred proteins and peptides that exhibit a significant diversity in terms of isoform complexity, toxicity and immunogenicity. Therefore, antivenom doesn’t take into account the representation of venom toxins and contains therapeutically redundant IgGs to non-toxic venom components, and a lack of high titre IgGs to highly toxic, but weakly immunogenic components. The usual consequence of the century old immunisation protocol is the need to administer large volumes to achieve venom-neutralisation in an envenomed patient, which greatly increases the risk of antivenom-induced adverse effects and reduces its affordability. The Alistair Reid Venom Research Unit has pioneered a new approach using the rationale of generating venom toxin‐specific antibodies on the basis that an antivenom that only targets the most pathogenic toxin groups would be predicted to overcome these issues by improving the clinical efficacy of the treatment. Based upon preliminary work illustrating extensive cross‐specific and cross‐generic reactivity of a toxin‐specific antibodies generated against some of the most pathogenic toxin groups of venoms from medically-important species, the overarching aim of the work described in this thesis was to extended this toxin-specific antivenom approach with a view to ultimately generating a therapy against all the African species of the Echis genus. In order to overcome the high isoform diversity known for most of the pathologically-important venom toxin groups, we conducted a bioinformatic interrogation of the venom gland transcriptomes of Echis ocellatus, Echis pyramidum leakeyi and Echis coloratus for five major target toxin groups: Phospholipases A2 (PLA2), Serine proteases (SP) C-type lectins (CTLs), Metalloproteinases (SVMPs) and Disintegrins that identified epitopes on the basis of i) sequence conservation, ii) antigenicity, (iii) surface exposure and (iv) coverage across the EST data. Resultant sequences were synthesised as epitope-strings and subsequently delivered as DNA and recombinant proteins immunogens that in a proteic form successfully generated antibodies capable of binding to a number of reduced venom proteins in a cross-reactive manner, suggesting the presence of specific and generic shared epitopes of importance. The results obtained in this study helped identifying key elements of the toxin-specific approach for the design of antivenoms and highlighted the need to elucidate several aspects of the molecular interaction of the raised antibodies against the target venom proteins, in order to have an accurate approach to their binding in a native state. In addition, the study successfully approached venom glycosylation, and aspect that hasn’t been studied in detail and came apparent during the progress of the toxin specific antivenom gave light in the future stages of its development.