Analysis of camelid IgG for antivenom development: Serological responses of venom-immunised camels to prepare either monospecific or polyspecific antivenoms for West Africa.

Snake envenoming is a significant cause of mortality and morbidity in sub-Saharan Africa. The only effective treatment, antivenom, has been in short supply since the 1990s. Whilst the humanitarian response by some antivenom producers has significantly improved the situation, strategies to ensure the long term stability of antivenom supply are still necessary. We are investigating whether the potential safety and logistic advantages of camel IgG antivenom can be exploited to improve antivenom provision in many countries where snakebite is endemic. This study assessed the IgG titre, specificity and avidity of camels immunised with either individual venom or a mixture of venoms from the three most medically important snakes of West Africa, the saw-scale viper (Echis ocellatus), the puff adder (Bitis arietans) and the spitting cobra (Naja nigricollis). Seven of the eight immunised camels generated IgG titres and avidities comparable to, or exceeding, that of commercial equine and ovine antivenoms that are highly effective in envenomed patients. In this, the first of a series of reports on the potential utility of camelid IgG antivenom, we describe an immunisation protocol that induced potent, sustained serological response of very high antibody avidity. These attributes suggest, from an immunological perspective, that camel IgG antivenoms should be as efficacious as current equine and ovine antivenoms.