title: TLR4 polymorphisms mediate impaired responses to respiratory syncytial virus and lipopolysaccharide.
abstract: Severe bronchiolitis following respiratory syncytial virus (RSV) infection occurs in only a small subset of infected infants and the basis for variations in disease severity is not understood. Innate immune responses to RSV are mediated by TLR-4, and the (299)Gly and (399)Ile alleles of the TLR4 gene have been linked epidemiologically with increased severity of RSV disease in children. We hypothesized that cellular immune responses to RSV mediated by these variant forms of the receptor are defective relative to responses mediated via the common form of the receptor. Human bronchial epithelial cells were transfected with TLR4 constructs encoding the common TLR4 gene sequence ((299)Asp/(399)Thr), or the (299)Gly or (399)Ile alleles, and cytokine responses to in vitro RSV challenge were analyzed in the different transfected cells. Follow-up studies compared RSV-induced responses in PBMC from children expressing these same TLR4 genotypes. Human bronchial epithelial expressing (299)Gly or (399)Ile displayed normal levels of intracellular TLR4 but failed to efficiently translocate the receptor to the cell surface. This was associated with reduced NF-kappaB signaling post-TLR4 engagement, reduced production of IFNs, IL-8, IL-10, IL-12p35, IL-18, and CCL8, and the absence of acute-phase TNF-alpha. These findings were mirrored by blunted PBMC responses to RSV in children expressing the same TLR4 variants. Compromised first-line defense against RSV at the airway-epithelial surface of children expressing these TLR4 variants may thus confer increased susceptibility to severe infections with this virus.
authors.affiliation: Division of Cell Biology, Telethon Institute for Child Health Research, Centre for Child Health Research, University of Western Australia, West Perth, WA 6872, Australia.
authors.forename: Meri K
authors.initials: MK
authors.lastname: Tulic
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Hurrelbrink
authors.forename: Cecilia M
authors.initials: CM
authors.lastname: Prêle
authors.forename: Ingrid A
authors.initials: IA
authors.lastname: Laing
authors.forename: John W
authors.initials: JW
authors.lastname: Upham
authors.forename: Peter
authors.initials: P
authors.lastname: Le Souef
authors.forename: Peter D
authors.initials: PD
authors.lastname: Sly
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Holt
mesh_terms: D001980:Bronchi / Q000276:immunology / Q000528:radiation effects / Q000821:virology; D002460:Cell Line; D002462:Cell Membrane / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D002648:Child; D015967:Gene Expression Regulation, Viral / Q000276:immunology / Q000528:radiation effects; D005998:Glycine / Q000235:genetics; D006801:Humans; D007424:Intracellular Fluid / Q000276:immunology / Q000378:metabolism; D007532:Isoleucine / Q000235:genetics; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors / Q000276:immunology* / Q000378:metabolism*; D009000:Monocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D011110:Polymorphism, Genetic / Q000276:immunology*; D021381:Protein Transport / Q000235:genetics / Q000276:immunology; D020545:Respiratory Mucosa / Q000166:cytology / Q000276:immunology / Q000528:radiation effects / Q000821:virology; D012136:Respiratory Syncytial Viruses / Q000276:immunology* / Q000528:radiation effects; D051197:Toll-Like Receptor 4 / Q000235:genetics* / Q000502:physiology; D014162:Transfection; D014466:Ultraviolet Rays
chemical_list: D008070:Lipopolysaccharides; D051197:Toll-Like Receptor 4; D007532:Isoleucine; D005998:Glycine