Brucella induces STING-mediated Guanylate-Binding Protein expression and Unfolded Protein Response: Balancing Bacterial Elimination, Inflammation and Disease

1 Summary 2 Brucellosis is one of the world’s most frequent zoonotic diseases with over 500,000 3 new human infections every year. Human brucellosis in Brazil represents an additional 4 economic burden due to health care costs and has a major social impact due to 5 decreased productivity and quality of life and occasionally incapacitation or death. 6 Brucella abortus strain 19 vaccine is the principal vaccine used to prevent transmission 7 of brucellosis from cattle to humans worldwide and in Brazil and it is not a select agent. 8 The mechanisms that mediate protection by strain 19 are poorly understood. Host 9 mechanisms of innate immunity induced by the vaccine that control infection remain 10 obscure. Additionally, the vaccine contains several properties that are inhibitory to host 11 immunity. We have demonstrated that B. abortus, bacterial DNA and LPS leads to 12 inflammasome activation via STING/GBP (guanylate-binding protein) axis that limits 13 Brucella replication. In contrast, B. abortus induces the Unfolded Protein Response 14 (UPR) that favors Brucella survival in the host. Therefore, our long-term goal is to 15 resolve the black box of how Brucella activates innate immune components that 16 results in host resistance versus bacterial subversion of the immune response. 17 Based on these compelling preliminary data, we propose to test the central hypothesis 18 that Brucella abortus strain 19 activates protective innate immune mediators via 19 STING/GBP pathway and triggers the UPR to secure intracellular replication. Our 20 specific aims are: 1) To define which STING-mediated guanylated-binding proteins 21 (GBPs) are important to release bacterial DNA and LPS into host cells to activate 22 inflammasome receptors; 2) To determine whether the Unfolded Protein 23 Response (UPR) induced by Brucella regulates macrophage polarization to 24 facilitate bacterial persistence; 3) To determine whether the transcription factor 25 HIF-1α-dependent metabolic changes in macrophages induced by Brucella affect 26 inflammasome activation and bacterial clearance. We believe that our approach will 27 shed light on the mechanisms of immunity and/or pathogenesis of this important 28 human and animal pathogen. Finally, the investigators on this proposal have a strong 29 track record in brucellosis research and a unique combination of key expertise in 30 microbiology, innate immunity and cell biology.