Production of a Pan-specific Antivenom against Elapid Snakes and Development of In Vitro Assays to Assess the Potency of Pan-specific Antivenoms.
Development of Broad Spectrum Pan-specific Antivenoms against Venomous Snakes of Asia and Africa
Snakebite envenomation is a serious medical problem in many tropical developing countries and was considered by WHO as a neglected tropical disease. Antivenom (AV), the rational and most effective treatment modality, is either unaffordable and/or unavailable in many affected countries. Moreover, each AV is specific to only one (monospecific) or a few (polyspecific) snake venoms. This demands that each country to prepare AV against its local snake venoms, which is often not feasible. The production of a pan–specific antiserum effective against major medically important elapids in Asia was studied. The strategy was to use toxin fractions (TFs) of the venoms in place of crude venoms in order to reduce the number of antigens the immunized horses were exposed to. This enabled inclusion of a greater variety of elapid venoms in the immunogen mix, thus exposing the horse immune system to a diverse repertoire of toxin epitopes, giving rise to antiserum with wide paraspecificity against elapid venoms. The antivenom prepared from this antiserum was expected to be pan–specific and effective in treating envenomations by most elapids in many Asian countries. Due to economies of scale, the antivenom could be produced inexpensively and save many lives. This simple strategy and procedure could be readily adapted for the production of pan–specific antisera against elapids of other continents.
Figure 5. Horse Immunization
Figure 6. Multi–dose Injector
This study was published in PLoS Neglected Tropical Diseases under the title “A Simple and Novel Strategy for the Production of a Pan–specific Antiserum against Elapid Snakes of Asia” in 2016 and was submitted for petty patent in Thailand (number 1703002063).
Development of In Vitro Assays Based on Nicotinic Acetylcholine Receptor Binding to Assess the Potency of Pan-specific Antivenom Against Elapid Snakes
One of the hurdles in antivenom development is the in vivo assay of antivenom potency which is expensive, giving variable results and killing many animals. A novel in vitro assay was developed involving the specific binding of the postsynaptic neurotoxins (PSNTs) of elapid snakes with purified Torpedo californica nicotinic acetylcholine receptor (nAChR). The horse serum containing IgG against snake venom was incubated with PSNTs. The Ag–Ab complexs were removed from the solution. The remaining free PSNTs were incubated with nAChR before adding to the PSNT of Naja kaothia (NK3) coated ELISA plates. The potency of an antivenom was determined by the ability of its antibody to bind and neutralize the PSNT, thus preventing it from binding to nAChR. The assays gave excellent correlation (R2 = 0.9809; p < 0.0001) with the corresponding in vivo assay using mice. This in vitro assay should be useful in reducing or partially replacing the in vivo assays used to test antivenoms against N. kaouthia and other elapid venoms.
This study was published in the journal Scientific Reports under the title “A novel in vitro potency assay of antisera against Thai Naja kaouthia based on nicotinic acetylcholine receptor binding”. The assay has also been submitted for Thailand patent No. 1701003769 under title of “Procedure for in vitro assay of antiserum potency against Elapid snakes”.