RESUMO
The virB locus, which encodes the type IV secretion system, is a major component of virulence in Brucella. A non-polar virB10 mutant and a virB11 deletion mutant were constructed in Brucella canis. In the mouse model, both mutants were cleared at day 21 post-infection, indicating reduced virulence in mice. After challenging with wild-type B. canis, the amounts of CFU recovered at day 15 were significantly lower in the group previously vaccinated with the virB10 mutant. Levels of IgG1, IgG2a, IgG2b, and IgM, the induction of the cytokines IL-2, IL-4, IL-10, and the production of IFN-γ were measured in lymphocyte cultures. All strains elicited similar levels of different antibody isotype profiles, and no significant differences were detected (P < 0.05). The wild-type strain induced a rapid and strong INF-γ response at 24 h, while both mutants induced mild INF-γ responses at 24 h, which remained constant over the course of sampling. Our results suggest that the virB mutants elicit a protective immunity and may be considered as candidates for studies to be conducted in dogs against canine brucellosis.
Assuntos
Vacina contra Brucelose/imunologia , Brucella canis/imunologia , Brucelose/prevenção & controle , Fatores de Virulência/genética , Animais , Anticorpos Antibacterianos/sangue , Vacina contra Brucelose/administração & dosagem , Vacina contra Brucelose/genética , Brucella canis/genética , Brucelose/imunologia , Citocinas/metabolismo , Modelos Animais de Doenças , Feminino , Imunoglobulina G/sangue , Imunoglobulina M/sangue , Interferon gama/metabolismo , Leucócitos Mononucleares/imunologia , Camundongos , Camundongos Endogâmicos BALB C , Vacinas Atenuadas/administração & dosagem , Vacinas Atenuadas/genética , Vacinas Atenuadas/imunologiaRESUMO
The aim of this study was to evaluate the effect of 3 Brucella ovis subcellular protein fractions: Outer membrane (OMP), inner membrane (IMP), and cytoplasm (CP), on cellular immune response by in vitro production of interleukin (IL)-2, IL-4, and interferon (IFN)-gamma. Each fraction was inoculated 3 times into Balb/c mice, primary cultures of mice spleen cells were done, and these were then stimulated with the fractions. Culture supernatants were collected at 24, 48, 72, 96, and 120 h postinoculation. Cytokine concentration was measured by Duoset-enzyme-linked immunosorbent assay (ELISA). The OMP fraction induced highest cellular immune response of 1000 pg/mL of IL-2 at 24 h, which decreased to < 100 pg/mL by 96 h. The IL-2 response for the IMP fraction was low at 24 h, but exceeded that of the OMP fraction at 72, 96, and 120 h. The CP showed a poor IL response. Regarding the IFN-gamma production, OMP and IMP induced a high response at 120 h. These results open the possibility for the use of B. ovis outer and inner membrane proteins as a subcellular vaccine.
