Oral Immunization for Anti-snake Venom Production in Equine Animals
Author(s): Zameer Ahmed, Omar Bagasra, Sambreen Zameer, Shahana U. Kazmi and Muhammad R. Khanani, Shaheen Sharafat
The immunization process of current commercial manufacturing of anti-snake venom (ASV), uses injections of bentonite, complete Freund’s adjuvant, or incomplete Freund’s adjuvant, mixed with low doses of the snake venom in horses (but rarely in other large mammals), which frequently cause serious adverse effects in host animals. At the site of injection, horses may develop painful swelling, granuloma, abscess, scar, or systemic neurological and hematological defects, low antibody response, or death due to anaphylactic shock.
We sought to investigate a novel alternate immunization strategy with oral administration of snake venom with adjuvants. We utilized M5904 mineral oil emulsion as an adjuvant that was mixed with sub-lethal doses (LD) of the snake venoms. Our preliminary experiments were initiated in March 2011 and the present data culminated in March 2018. In our initial experiments which were carried out in inbred mice, the LD100 was 10.36 ug/25 grams of mice for Naja. oxins and 10.0 ug/25 gram of Naja. karachians. We extrapolated the sub-LD dose to horses by cutting the LD100 in mice to 20%. This dose did not cause any apparent pathology in horses and therefore, we adopted that dose for the equine.
The antibody titers were measured in vitro by quantitative ELISA and in vivo by neutralization assay in mice. This method resulted in the development of high titer neutralization by the ASV antibodies, without any significant side effects in equine experimental models, against venoms of two cobra species namely Naja oxiana and Naja karachians. The results showed that three oral dosage schedules produced highly significant (P<0.001) neutralizing antibodies with persistent yield of immunoglobulin for 6-months of observation. This novel technique of oral administration of snake venoms will be useful for commercial ASV production of potent antibodies at a significantly reduced cost and without any significant adverse effects on equine health.