Development and characterization of a new carrier for vaccine delivery based on calcium-alginate nanoparticles: Safe immunoprotective approach against scorpion envenoming

To enhance humoral defense against diseases, vaccine formulation is routinely prepared to improve immune response. Studies in nanomaterials as a carrier of vaccine delivery are promising and interesting. In this study, attenuated Androctonus australis hector (Aah) venom and its toxic fraction were encapsulated into different formulations inside calcium–alginate nanoparticles (Ca–Alg Nps), and used as a vaccine delivery system against scorpion envenomation. Ca–Alg Nps were prepared by ionic gelation and characterized. An immunization schedule was undertaken in rabbits in order to study how Aah venom entrapped in Ca–Alg Nps might induce protective immunity. Results showed the influence of different parameters on the suitable nanoparticle formation. They also showed no toxicity of free Ca–Alg Nps and a different inflammatory profile depending on the nanovaccine formulations. More interestingly, evaluation of specific IgG titer and IgG1/IgG2a isotype balance revealed a protective effect with the nanoparticles encapsulating the attenuated antigens. Challenge up to 6 LD 50 of native venom, allowed to an important immunoprotection of all immunized rabbits, with no recorded death. Taken together and with respect to the properties of nanoparticles and high immunogenicity, calcium–alginate nanoparticles could be considered as a new promising adjuvant system and a vaccine delivery against scorpion envenomation.