Desenvolvimento de vacina contra botulismo tipo D utilizando como adjuvantes micropartículas e hidrogel de quitosana.

Abstract

Botulism is often a fatal poisoning caused by botulinum neurotoxin. In Brazil it is one of the main causes of mortality in production systems of beef and milk. The disease is caused by botulinum toxin type C and D produced by Clostridium botulinum present in decomposed organic matter from plant or animal. The occurrence of the disease is associated with bone chewing due to nutritional deficiency, and with ingestion of contaminated or poorly maintained food. The diagnosis is clinical, and the treatment is impractical due to unavailability of serum. Prevention through vaccination, removal of animal carcasses from the pasture field and better conservation of water and food are recommended. The vaccination is annual, and primed animals should receive a booster dose within four weeks. This vaccination program requires a better management, what results in economic damage due to weight loss, and a decreased adherence to vaccination. In a search for a single dose vaccine through a system of sustained release of antigen, this study has developed two vaccines based on microparticles and hydrogels of chitosan. In order to obtain a desirable profile of immune response, chitosan has been previously characterized and selected, and the toxin was partially purified and detoxified. The process of obtaining microparticles containing type D botulinum toxin was standardized through the study of critical process parameters. The formulated vaccines were evaluated in comparison with the conventional vaccine containing aluminum hydroxide through testing efficacy in guinea pigs, and measurement of antibody titer by type D botulinum antitoxin through neutralization in mice. The results have showed that the chitosan-based formulations enable the production of viable vaccines which are capable of stimulating a more intense and protective immune response for a longer period after a single dose. The profiles of specific antibody formation in serum suggest that chitosan-based formulations behave as systems for prolonged release of antigens.