Neutralizing Nanobodies against Venoms from Naja haje Species Captured in North Africa

Abstract

Snakebite envenoming (SBE) remains a severely neglected public health issue, particularly affecting tropical and subtropical regions, with Africa experiencing an estimated 435,000 to 580,000 snakebites annually, leading to high morbidity and mortality rates, especially across Africa and Asia. Recognized as a Neglected Tropical Disease, SBE management is further complicated by the inadequate efficacy of current antivenom treatments. Of particular concern are cobras (Naja sp.), whose neurotoxins can induce rapid fatal respiratory paralysis. In this study, we investigate the potential of nanobodies as a promising next-generation of immunotherapeutics against cobra venoms. Through a dual strategy of the characterization of venom toxic fractions from cobras captured for the first time in Algeria and Tunisia biotopes, coupled with in vitro assays to evaluate their interactions with acetylcholine receptors, and subsequent immunization of dromedaries to produce specific nanobodies, we identified two lethal fractions, F5 and F6, from each venom, and selected five nanobodies with significant binding and neutralizing of 3DL50 (0.74 mg/kg). The combination of these nanobodies demonstrated a synergistic effect, reaching 100% neutralizing efficacy of 2DL50 lethal venom fraction (0.88 mg/kg) doses in mice. Additionally, our findings highlighted the complex mechanism of cobra venom action through the lethal synergism among its major toxins.