RESUMO
Brucella abortus is a facultative intracellular bacterium that causes brucellosis, a prevalent zoonosis that leads to abortion and infertility in cattle, and undulant fever, debilitating arthritis, endocarditis, and meningitis in humans. Signaling pathways triggered by B. abortus involves stimulator of IFN genes (STING), which leads to production of type I IFNs. In this study, we evaluated the pathway linking the unfolded protein response (UPR) and the endoplasmic reticulum-resident transmembrane molecule STING, during B. abortus infection. We demonstrated that B. abortus infection induces the expression of the UPR target gene BiP and XBP1 in murine macrophages through a STING-dependent pathway. Additionally, we also observed that STING activation was dependent on the bacterial second messenger cyclic dimeric GMP. Furthermore, the Brucella-induced UPR is crucial for induction of multiple molecules linked to type I IFN signaling pathway, such as IFN-ß, IFN regulatory factor 1, and guanylate-binding proteins. Furthermore, IFN-ß is also important for the UPR induction during B. abortus infection. Indeed, IFN-ß shows a synergistic effect in inducing the IRE1 axis of the UPR. In addition, priming cells with IFN-ß favors B. abortus survival in macrophages. Moreover, Brucella-induced UPR facilitates bacterial replication in vitro and in vivo. Finally, these results suggest that B. abortus-induced UPR is triggered by bacterial cyclic dimeric GMP, in a STING-dependent manner, and that this response supports bacterial replication. In summary, association of STING and IFN-ß signaling pathways with Brucella-induced UPR unravels a novel link between innate immunity and endoplasmic reticulum stress that is crucial for bacterial infection outcome.
Assuntos
Brucella abortus/fisiologia , Brucelose/imunologia , Interações Hospedeiro-Patógeno/imunologia , Proteínas de Membrana/imunologia , Nucleotídeos Cíclicos/imunologia , Resposta a Proteínas não Dobradas/imunologia , Animais , Brucelose/genética , Interações Hospedeiro-Patógeno/genética , Humanos , Proteínas de Membrana/genética , Camundongos , Camundongos Knockout , Nucleotídeos Cíclicos/genética , Transdução de Sinais/genética , Transdução de Sinais/imunologiaRESUMO
Immunity against microbes depends on recognition of pathogen-associated molecular patterns by innate receptors. Signaling pathways triggered by Brucella abortus DNA involves TLR9, AIM2, and stimulator of IFN genes (STING). In this study, we observed by microarray analysis that several type I IFN-associated genes, such as IFN-ß and guanylate-binding proteins (GBPs), are downregulated in STING knockout (KO) macrophages infected with Brucella or transfected with DNA. Additionally, we determined that STING and cyclic GMP-AMP synthase (cGAS) are important to engage the type I IFN pathway, but only STING is required to induce IL-1ß secretion, caspase-1 activation, and GBP2 and GBP3 expression. Furthermore, we determined that STING but not cGAS is critical for host protection against Brucella infection in macrophages and in vivo. This study provides evidence of a cGAS-independent mechanism of STING-mediated protection against an intracellular bacterial infection. Additionally, infected IFN regulatory factor-1 and IFNAR KO macrophages had reduced GBP2 and GBP3 expression and these cells were more permissive to Brucella replication compared with wild-type control macrophages. Because GBPs are critical to target vacuolar bacteria, we determined whether GBP2 and GBPchr3 affect Brucella control in vivo. GBPchr3 but not GBP2 KO mice were more susceptible to bacterial infection, and small interfering RNA treated-macrophages showed reduction in IL-1ß secretion and caspase-1 activation. Finally, we also demonstrated that Brucella DNA colocalizes with AIM2, and AIM2 KO mice are less resistant to B. abortus infection. In conclusion, these findings suggest that the STING-dependent type I IFN pathway is critical for the GBP-mediated release of Brucella DNA into the cytosol and subsequent activation of AIM2.
Assuntos
Brucella abortus/imunologia , Brucelose/imunologia , Brucelose/metabolismo , Proteínas de Ligação ao GTP/metabolismo , Inflamassomos/metabolismo , Proteínas de Membrana/metabolismo , Transdução de Sinais , Animais , Brucella abortus/genética , Brucelose/genética , Brucelose/microbiologia , GMP Cíclico/análogos & derivados , GMP Cíclico/metabolismo , Citocinas/metabolismo , Proteínas de Ligação ao GTP/genética , Expressão Gênica , Perfilação da Expressão Gênica , Granuloma/metabolismo , Granuloma/microbiologia , Granuloma/patologia , Interações Hospedeiro-Patógeno/genética , Interações Hospedeiro-Patógeno/imunologia , Imunidade Inata , Mediadores da Inflamação , Fator Regulador 3 de Interferon/metabolismo , Interferon Tipo I/genética , Interferon Tipo I/metabolismo , Macrófagos/imunologia , Macrófagos/metabolismo , Proteínas de Membrana/genética , Camundongos , Camundongos Knockout , Modelos Biológicos , NF-kappa B/metabolismoRESUMO
After 200 years of practice, vaccinology has proved to be very effective in preventing infectious diseases. However, several human and animal pathogens exist for which vaccines need to be improved or simply have not yet been discovered. The era of molecular genetic has given a new breath for vaccine development with the achievement of the "Third Generation of Vaccines": the DNA vaccine. In this article, we reviewed strategies that have been used to improve and modulate the immune response induced by DNA vaccines, using as a model the intracellular bacterial pathogen Brucella abortus. First, we described different approaches used to isolate and to identify genes that encode potential immunogens. Secondly, we reported the use of cytokine genes and genetic adjuvants that could improve the immunogenicity of target genes. And finally, we discussed the "Expression Library Immunization"-(ELI) strategy and the recent results obtained against Brucella abortus infection.