Evolution of Specific Antibody Response of Horses Immunized with Naja Naja Oxiana Snake Venom

An indirect ELISA for potency assessment of Naja naja oxiana horse antivenom was developed, with the aim of monitoring of antivenom immunoglobulin levels to replace the well-established conventional in vivo neutralization assay. According to this purpose, blood sera were taken during immunization schedule of the nineteen horses used in snake antivenom manufacture at the Razi Vaccine and Serum Research Institute. In addition, a group of fifteen batches of monovalent and polyvalent anti-snake venom plasma was examined by both in vitro and in vivo assays. ELISA is based on the horse anti-Naja antibodies recognizing toxic fractions mixture, the main antigen that induces neutralizing antibody against Naja naja oxiana venom. Consistent results were found between the ELISA optical densities and corresponding neutralization potency values, demonstrating that the in vitro assay as well as in vivo assay can be used to estimate neutralizing antibody activity of the sera. It was found that venom antibodies reached a maximum level about 3rd week after immunization. The major advantage of designed ELISA is its ability to correctly separate poor or non-responder horses during initial steps of immunization which venom antibodies are very low in sera and antivenom estimation is difficult by in vivo neutralization test.