RESUMO
BACKGROUND: Streptococcus suis (SS) is a major swine pathogen and a serious zoonotic pathogen causing septicemia and meningitis in piglets and humans. Using an immunoproteomic approach, we previously brought evidence that ornithine carbamoytransferase (OCT) may represent a vaccine candidate to protect against S. suis biofilm-related and acute infections. METHOD: In this study, the gene encoding OCT was cloned into the expression vector pET-28a and the recombinant protein was expressed in Escherichia coli BL21. The immunogenicity and protective efficacy of the SS OCT was further investigated in a mouse model. RESULTS: The protein was found to be expressed in vivo and elicited high antibody titers following SS infections in mice. An animal challenge experiment with SS showed that 62.5% of mice immunized with the OCT protein were protected. Using an in vitro competitive adherence inhibition assay of adherence, evidence was obtained that OCT could significantly reduce the number of SS cells adhered to porcine kidney PK-15 cells. The bacterial levels recovered in mice of the OCT immunized group were significantly decreased in some organs, compared with the control group. CONCLUSION: In summary, our results suggest that the recombinant SS OCT protein, which is involved in bacterial adherence, may efficiently stimulate an immune response conferring protection against SS infections. It may therefore be considered as a potential vaccine candidate, although further studies are necessary to evaluate their use in swine.
Assuntos
Aderência Bacteriana/fisiologia , Ornitina Carbamoiltransferase/imunologia , Ornitina Carbamoiltransferase/isolamento & purificação , Infecções Estreptocócicas/imunologia , Streptococcus suis/enzimologia , Animais , Anticorpos Antibacterianos/sangue , Antígenos de Bactérias/genética , Antígenos de Bactérias/imunologia , Proteínas de Bactérias/genética , Vacinas Bacterianas/imunologia , Biofilmes , Modelos Animais de Doenças , Escherichia coli/genética , Imunização , Camundongos , Ornitina/metabolismo , Ornitina Carbamoiltransferase/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Infecções Estreptocócicas/microbiologia , Infecções Estreptocócicas/prevenção & controle , Streptococcus suis/genética , Streptococcus suis/imunologiaRESUMO
Adjuvants play an important role in the formulation of effective and appropriate vaccines. A series of synthetic bursin and bursin-like peptides was heterologously expressed in Escherichia coli. The use of bursin as an adjuvant enhanced the specific immune responses of mice immunized with a recombinant Japanese encephalitis virus E-binding domain (JEV E-BD) fusion protein. The effect was determined in the form of protective anti-JEV E titers, antibodies (IgG1 and IgG2a), spleen cell lymphocyte proliferation, the levels of interferon-gamma and interleukin-4 cytokines, and the T-lymphocyte sub-type composition. The IgG2a titer and interferon-gamma level suggested that the E-BD protein potentiates the Th1 immune response. These responses were changed when the immunogen was combined with one of the synthetic peptides as adjuvant. JEV-neutralization assay results show that the presence of bursin significantly enhance the JEV-neutralizing titer. We conclude that bursin as an adjuvant is a potent enhancer of immune response in mice immunized with the JEV subunit vaccine, and represents a promising adjuvant for vaccination.