title: Exposure to HIV-1-encoded Toll-like receptor 8 ligands enhances monocyte response to microbial encoded Toll-like receptor 2/4 ligands.
abstract: BACKGROUND
  Chronic HIV-1 infection is characterized by high levels of persistent immune activation. Both HIV-1-encoded Toll-like receptor 7/8 (TLR7/8) ligands and TLR ligands encoded by products of microbial translocation have been implicated in inducing and sustaining immune activation in infected individuals, but the consequences of simultaneous exposure to different TLR ligands are not well understood.
  
  
  OBJECTIVE
  To examine the impact of preexposure of monocytes to HIV-1-encoded TLR8 ligands on their ability to respond to subsequent stimulation with microbial TLR2/4 ligands.
  
  
  METHODS
  Stable monocytic cell lines (THP-1-Blue-CD14 cells) or primary monocytes were stimulated with ligands for TLR2, TLR4, and TLR8, including chemically inactivated HIV-1, alone, or in sequential combinations. Responses by THP-1 cells to TLR stimulation were quantified using Quanti-Blue colometric assay, and TLR-induced tumor necrosis factor-alpha production of primary monocytes was quantified by intracellular cytokine staining using flow cytometry.
  
  
  RESULTS
  The exposure of monocytes to HIV-1 or HIV-1-derived TLR8 ligands sensitized these cells for TLR4 stimulation, resulting in a significantly higher response to lipopolysaccharide compared to cells that were not prestimulated with TLR8 ligands or HIV-1.
  
  
  CONCLUSIONS
  TLR crosstalk can enhance the pro-inflammatory monocytes response to products of microbial translocation and might play an important role in the modulation of immune function in HIV-1 infection.
authors.affiliation: HIV Pathogenesis Programme, Doris Duke Medical Research Institute and KwaZulu-Natal Research Institute for TB and HIV, Nelson R. Mandela Medical School, University of KwaZulu-Natal, Durban, South Africa.
authors.forename: Marianne W
authors.initials: MW
authors.lastname: Mureith
authors.forename: J Judy
authors.initials: JJ
authors.lastname: Chang
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Lifson
authors.forename: Thumbi
authors.initials: T
authors.lastname: Ndung'u
authors.forename: Marcus
authors.initials: M
authors.lastname: Altfeld
mesh_terms: D002460:Cell Line; D002478:Cells, Cultured; D018450:Disease Progression; D005260:Female; D005434:Flow Cytometry; D015658:HIV Infections / Q000276:immunology* / Q000378:metabolism / Q000821:virology; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D008024:Ligands; D008213:Lymphocyte Activation / Q000276:immunology*; D008297:Male; D009000:Monocytes; D012367:RNA, Viral; D051200:Toll-Like Receptor 8 / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology* / Q000378:metabolism; D019562:Viral Load
chemical_list: D008024:Ligands; D012367:RNA, Viral; D051200:Toll-Like Receptor 8; D014409:Tumor Necrosis Factor-alpha