Evaluation of a new vaccine based on pDNA and recombinant protein against Helicobacter pylori

Dissertação para obtenção do Grau de Mestre em Genética Molecular e BiomedicinaHelicobacter pylori is a bacterium capable of surviving and infecting a healthy human stomach and it is estimated that infect more than a half of world population. Despite of being almost always asymptomatic, in some cases, the infection can evolve to several gastric disease as chronic gastritis, peptic ulcers, gastric cancer and MALT lymphoma. Vaccination against H. pylori is a promising option due to emerging problems of antibiotics treatment. It is thought that oral immunization could be a good approach for a more effective protection against infections by H. pylori, creating a first line of defense in mucosal surfaces. Chitosan nanoparticles are a suitable vehicle for oral vaccines delivery due to its immunogenic and mucoadhesive properties, protecting the DNA and allowing high levels of transfected cells. Thus, this work aims to evaluate a new pDNA- and recombinant protein-based vaccine, with multi epitopes of different H. pylori antigens. Following production and purification of plasmid DNA and recombinant proteins, vaccines were formulated for oral and intramuscular administration with the antigens encapsulated with chitosan nanoparticles. The type of immune response induced and the effectiveness of protective immunity elicited were assessed by ELISA, through analysis of specific IgGs, mucosal SIgA and cytokines levels produced by immunized BALB/C mice. When give by the intramuscular route, the formulated pDNA and recombinant protein-based vaccines efficiently stimulated the production of specific IgG2a and IgG1, which is supported by cytokines levels, revealing a better and balanced systemic immune response than oral immunizations. Nevertheless as expected, oral immunizations with either pDNA vaccines or recombinant protein revealed high levels of SIgA, showing to be effective in gastric mucosal immunization for a more protective immune response, contrasting with intramuscular immunizations which did not induce SIgA. The immunization results showed that both pDNA and recombinant proteins vaccines encapsulated with chitosan nanoparticles are good candidates for the development of a future vaccine to prophylactic and therapeutic use to improve the eradication of H. pylori infections.Fundação da Ciência e Tecnologia - (PTDC/BIO/69242/2006); FEDER - (PEst-OE/SAU/UI4013/2011