A Combined Strategy to Improve the Development of a Coral Antivenom Against Micrurus spp.

Abstract

Accidents involving <i>Micrurus</i> snakes are not the most common ones but are noteworthy due to their severity. Victims envenomed by <i>Micrurus</i> snakes are at high risk of death and therefore must be treated with coral antivenom. In Brazil, the immunization mixture used to fabricate coral antivenom contains <i>Micrurus frontalis</i> and <i>Micrurus corallinus</i> venoms, which are difficult to be obtained in adequate amounts. Different approaches to solve the venom limitation problem have been attempted, including the use of synthetic and recombinant antigens as substitutes. The present work proposes a combined immunization protocol, using priming doses of <i>M. frontalis</i> venom and booster doses of synthetic B-cell epitopes derived from <i>M. corallinus</i> toxins (four three-finger toxins-3FTX; and one phospholipase A₂-PLA₂) to obtain coral antivenom in a rabbit model. Immunized animals elicited a humoral response against both <i>M. frontalis</i> and <i>M. corallinus</i> venoms, as detected by sera reactivity in ELISA and Western Blot. Relevant cross-reactivity of the obtained sera with other <i>Micrurus</i> species (<i>Micrurus altirostris, Micrurus lemniscatus, Micrurus spixii, Micrurus surinamensis)</i> venoms was also observed. The elicited antibodies were able to neutralize PLA₂ activity of both <i>M. frontalis</i> and <i>M. corallinus</i> venoms. <i>In vivo</i>, immunized rabbit sera completely protected mice from a challenge with 1.5 median lethal dose (LD₅₀) of <i>M. corallinus</i> venom and 50% of mice challenged with 1.5 LD₅₀ of <i>M. frontalis</i> venom. These results show that this combined protocol may be a suitable alternative to reduce the amount of venom used in coral antivenom production in Brazil.