title: Role of human Toll-like receptors in naturally occurring influenza A infections.
abstract: BACKGROUND
  We investigated the roles of Toll-like receptors (TLRs) in naturally occurring influenza.
  
  
  METHODS
  A prospective, case - control study was conducted. Adults hospitalized with virologically confirmed influenza A infections (onset <48 hours, before treatment) were compared with age-/gender-matched controls. TLRs (2, 3, 4, 7, 8, 9) expression in monocytes and dendritic cells (DCs - total, myeloid, plasmacytoid) was quantitated using flow cytometry. Gene expression of RLRs (RIG-1, MDA-5) was evaluated using real-time PCR. Concomitant signaling molecules expression, plasma cytokine/chemokine concentrations, and respiratory tract viral loads were measured. PBMCs were cultured and stimulated ex vivo with TLR-specific ligands for cytokine responses.
  
  
  RESULTS
  Forty two patients with influenza (24 A/H3N2, 18 A/H1N1pdm09) and 20 controls were studied. Patients' mean age was 68 ± 16 years; 81% had respiratory/cardiovascular complications. There were increased cellular expressions of TLR9, TLR8, TLR3, and TLR7 during influenza; TLR2 and TLR4 were suppressed. Results were similar for both virus strains. Higher TLR expression levels at presentation significantly correlated with lower viral loads (Spearman's rho: -0.46 to -0.69 for TLR9, TLR8, and TLR3; P-values <0.05). Multivariate regression models (adjusted for age, comorbidity, disease severity, time from onset) confirmed their independent associations. Increased signaling molecules (phospho-MAPKs, IκB) and inflammatory cytokines (IL-6, sTNFR-1, CCL2/MCP-1; CXCL10/IP-10, IFN-γ) correlated with increased TLR expression. RLRs were upregulated simultaneously. PBMCs of patients with influenza showed significant, dynamic changes in their cytokine responses upon TLR stimulation, compared with controls.
  
  
  CONCLUSIONS
  Our results suggest that TLRs play an important role in early, innate viral inhibition in naturally occurring influenza. Inflammatory cytokine responses are concomitantly induced. These findings support investigation of TLR targeting as a novel intervention approach for prophylaxis against influenza.
authors.affiliation: Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, China. leelsn@cuhk.edu.hk
authors.forename: Nelson
authors.initials: N
authors.lastname: Lee
authors.forename: Chun Kwok
authors.initials: CK
authors.lastname: Wong
authors.forename: David S C
authors.initials: DS
authors.lastname: Hui
authors.forename: Sharon K W
authors.initials: SK
authors.lastname: Lee
authors.forename: Rity Y K
authors.initials: RY
authors.lastname: Wong
authors.forename: Karry L K
authors.initials: KL
authors.lastname: Ngai
authors.forename: Martin C W
authors.initials: MC
authors.lastname: Chan
authors.forename: Yi Jun
authors.initials: YJ
authors.lastname: Chu
authors.forename: Amy W Y
authors.initials: AW
authors.lastname: Ho
authors.forename: Grace C Y
authors.initials: GC
authors.lastname: Lui
authors.forename: Bonnie C K
authors.initials: BC
authors.lastname: Wong
authors.forename: Sunny H
authors.initials: SH
authors.lastname: Wong
authors.forename: Shea Ping
authors.initials: SP
authors.lastname: Yip
authors.forename: Paul K S
authors.initials: PK
authors.lastname: Chan
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D016207:Cytokines / Q000235:genetics / Q000276:immunology; D003713:Dendritic Cells / Q000276:immunology; D005260:Female; D006760:Hospitalization; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000302:isolation & purification*; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics / Q000302:isolation & purification*; D007251:Influenza, Human / Q000235:genetics / Q000276:immunology* / Q000821:virology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D051193:Toll-Like Receptors / Q000235:genetics / Q000276:immunology*
chemical_list: D016207:Cytokines; D051193:Toll-Like Receptors
keywords: Influenza; Toll-like receptors
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