Nontypeable Haemophilus Influenzae DNA Stimulates Type I Interferon Mediated By STING-TBK1-IRF3 Signaling Pathway

Objective: To investigate the role of NTHI-DNA in immunity during infection with NTHI and the mechanisms that NTHI-DNA stimulating I-IFN.Background:NTHI,a gram-negative coccobacillus,commonly colonizes the upper respiratory tract in healthy people.However,substantial numbers of COPD patients are colonized by NTHI in their lower airways,some of which could invade host epithelial cells through cytoskeletal rearrangement and endocytosis mediated by lipid raft or a receptor.Intracellular NTHI is able to evade high concentration of antibiotics,which is the main reason for the protracted course of disease.In several infection models,bacterial DNA acted as PAMPs sensed by a serious of DNA sensors and induced the production of proinflammatory cytokines via STING-TBK1-IRF3 pathway.Methods and Results:1.Using antibiotic protection assay(APA)to examine the immunity induced by internalized NTHI;Detecting the expression of IFN-? and CXCL10 stimulated by DNA isolated from NTHI,which further confirmed NTHI-DNA participated in immune response during NTHI infection.2.The expression of cGAS and IFI16 was up-regulated after detecting the common DNA sensors in cells infected with NTHI;Knockdowning cGAS could inhibit the expression of I-IFN stimulated by internalized NTHI and NTHI-DNA.3.There was a significant difference between MEFWT cells and MEFSTING-/-cells in response to NTHI-DNA;NTHI-DNA could induce the expression of p-TBK1 and promote the production of p-IRF3 in nucleus.Over-expression of STING/TBK1/IRF3 in HEK293 T cells stimulated the production of IFN-? and(or)CXCL10 mediated by NTHI-DNA.Results above indicated that NTHI-DNA activated IFN-? and CXCL10 through a STING-TBK1-IRF3 cascade.Conclusions: Taken together,our study pointed that NTHI-DNA could elicit a strong production of I-IFN and CXCL10 via STING-TBK1-IRF3 pathway during NTHI infection.The present research might be helpful to further investigate the internalized bacteria and find solutions to control NTHI infection.An effective prevention and treatment would reduce morbidity,cost of health care and use of antibiotic.