A polygeneric immunogen composed of 22 venoms from sub-Saharan African snakes to expand the neutralization scope of the EchiTAb-plus-ICP antivenom

Abstract

Recent research suggests that a polygeneric immunogen made from the venoms of the most medically important viperid and elapid snakes in sub-Saharan Africa could elicit a broader antibody response in horses compared to the current EchiTAb-plus-ICP antivenom, especially against neurotoxic elapid venoms. To test this, 25 horses that have been regularly immunized to produce this antivenom were reimmunized with an immunogen containing 22 venoms from various snake species from the genera Bitis, Echis, Dendroaspis, and both spitting and non-spitting Naja. The plasma collected from these horses was processed using the caprylic acid method to produce an industrial-scale freeze-dried antivenom. The anti-lethal neutralization scope of this new formulation was then compared to that of EchiTAb-plus-ICP which is designed to target the venoms of Bitis arietans, Echis ocellatus, Naja nigricollis, and Dendroaspis polylepis. The results indicated that adding more venoms to the immunogen did not significantly enhance the neutralization of the lethal effect of viperid venoms (except for Bitis nasicornis) or of venoms of spitting cobras (except for Naja katiensis). However, incorporating additional venoms from non-spitting neurotoxic Naja spp. and Dendroaspis spp. improved the neutralization scope of EchiTAb-plus-ICP against these neurotoxic venoms. The antivenom generated showed a wider anti-lethal neutralizing scope, as compared to the standard EchiTAb-plus-ICP antivenom and constitutes a good candidate to be tested in clinical trials in sub-Saharan Africa.