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| Author(s): |
Luciane Benedita Duarte Pivetta
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia |
| Defense date: | 2011-02-28 |
| Examining board members: |
Marcelo Brocchi;
Gonçalo Amarante Guimarães Pereira;
Maria Elisabete Sbrogio de Almeida
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| Advisor: | Marcelo Brocchi |
| Abstract | |
Pathogenic Salmonella enterica serovars are the cause of a global health problem that ranges gastroenteritis to lethal systemic disease. Attenuated strains of Salmonella enterica are promising as live vaccines because they are orally administrated and capable of inducing a mucosal and systemic immune response in the host. Besides, they can act as multifactorial vaccines delivering antigens from other diseases. In this work, attenuated strains of Salmonella enterica were produced and the attenuation of the virulence and the induction of an immunologic response were evaluated in the murine model of salmonellosis. The recombinant strains were constructed using the ?Red system of homologous recombination deleting one or more genes with pleiotropic effects on Salmonella virulence. After that, a PCR to confirm the deletion of the target gene was made and the strains were transduced with bacteriophage P22 to avoid problems with lipopolysaccharide's integrity. Phenotypic characterization as the in vitro growth curve of the strains, the resistance to ROI and RNI species and the ability of survival inside J774 macrophages cultures were performed. The attenuation of the strains was evaluated in vivo trough oral and intraperitoneal inoculations of the strains into BALB/c/AnUnib mice and the median lethal dose was also established. Many levels of attenuation were reached and among the developed strains, the double mutant strain for the genes hupA and hupB was the one with the best results. In the protection and challenge assays, 100% of the animal vaccinated with two doses of the 'delta'hupA'delta'hupB strain survived to the challenge with lethal doses of the wild type strain. For this strain it was also verified the capacity of colonization into blood, peyer's patches and spleen as well as the production of IgG and IgA antibodies. In the developmente of a live vaccine it is ideal to have a strain that is attenuated but still capable of inducing an immune response in the host. Reaching this balance is a challenge and the deletion of virulence genes in Salmonella entails different levels of attenuation although they are closely related. A future prospect is the improvement of these attenuated strains with the insertion of controlled expression systems and heterologous antigens, creating a multifactorial vaccine (AU) | |
| FAPESP's process: | 09/02905-5 - Development and characterization of attenuated Salmonella enterica strains: Evaluation of the immunogenicity and the protective potential. |
| Grantee: | Luciane Benedita Duarte Pivetta |
| Support Opportunities: | Scholarships in Brazil - Master |