Antivenom production in the alpaca (Vicugna pacos): Monovalent and polyvalent antivenom neutralisation of lethal and procoagulant toxins in Australian elapid venoms

Alpaca (Vicugna pacos), like all other members of the camelid family, produce a unique heavy chain only IgG subclass. This form of IgG has been proposed as having superior neutralising properties and improved safety as compared with conventional mammalian IgG-based immunotherapeutics. The objective of this study was to investigate the potential of alpaca antibodies to neutralise the lethal and procoagulant properties of several Australian elapid snake venoms. Various experimental antivenoms were produced by immunisation of alpaca (Vicugna pacos) with combinations of five Australian elapid snake venoms: tiger snake (Notechis scutatus), eastern brown snake (Pseudonaja textilis), Papuan taipan (Oxyuranus scutellatus canni), mulga snake (Pseudechis australis) and common death adder (Acanthophis antarcticus). Venoms were emulsified in Freund's Incomplete Adjuvant and alpaca repeatedly immunised. Having previously shown that such alpaca produce persistent venom-specific antibody responses with minimal physiological impact on the animal, the current report demonstrates that polyvalent alpaca antivenom neutralises the lethal effects of three elapid venoms (tiger, brown and Papuan taipan venoms). Such lethality neutralisation was, however, of generally lower potency, but of the same order of magnitude, when compared with bioCSL monovalent antivenoms (brown, tiger and taipan antivenoms). By contrast, the monovalent alpaca tiger and brown snake antivenom were found to be superior to the equivalent bioCSL monovalent antivenoms when considering the neutralisation of the procoagulant effects of the respective immunising venoms. The bioCSL polyvalent antivenom also less potent, when compared with the alpaca taipan monovalent antivenom, against Papuan taipan venom procoagulant neutralisation. These findings support the potential of camelid immunoglobulin for the development of novel elapid specific antivenoms.