Immunological aspects of scorpion toxins: current status and perspectives

Significant progress has been made in immunological studies of scorpion toxins and several formats of antibodies directed against scorpion toxins have been reported. Some of these are commonly used in a specific treatment against envenoming; others are primarily used for immuno-biochemical characterizations. The preparation protocol of the antibody or its fragments can be substantially different from one laboratory to another, which complicates a direct comparison of the potency of the antivenom. The use of immune sera, the total immunoglobulin fraction or Fab and Fab'2 fragments as the therapeutic agent is widespread. A number of monoclonal antibodies have also been reported and used for engineering of Fv, ScFv or Fab fragments. Recently, a novel antibody format - known as nanobodies - derived from HCAbs of camelids and selected after phage display shows great potential to provide a more efficient therapy against scorpion envenoming. Subsequent bispecific derivatives have been designed and their pharmacokinetics have been studied. Distinct advantages and disadvantages have been attributed to these equine, murine or camelid antibodies and their derived fragments. Some fragments are easily amenable into next generation therapeutics after proper manufacturing and provide an ensured availability of the product to the medical community. Through examples, we will show how the comparison of the serotherapeutic effectiveness is compromised due to the absence of standardization, on the preparation of immunogens, production processes and / or nature of the products. We will report on recent advances in the field.