A role for TLR4-environment interactions effected through high GATA3/T-bet ratios in severe RSV bronchiolitis

SERRA ME; ACOSTA, PL; CABALLERO M; GIBBONS L; SALIM M; RODRIGUEZ A; REYNALDI A; GARCIA A; BADO D; BUCHOLTZ U; COVIELLO S; BATALLE, JP; DELGADO MF; MONSALVO AC; NEWCOMB D; BELLABARBA M; FEROLLA FM; LOPEZ MF; LIBSTER RP; SCALZO PM; WIMMENAUER, V; BERESTEIN A; SINIAWASKI S; BAILE C; DERICCO A; PELLEGRINI M; IGARZA I; REPETTO H; GUDAPATI P; POLACK NR; ALTHABE F; SHI M; BOOTHBY M; WEINBERG C; PEEBLES RS; SHEPHERD BE; KLEEBERGER SR; POLACK FP

Nashville

Simposio; Pediatrics Infectous diseases retreat 2011; 2011

Vanderbilt University

Background Respiratory sincitial virus (RSV) bronchiolitis in infants may present with varying severity. However the mechanisms by which generated this difference are not well understood. Patients who have the same risk factors but different severity of the disease indicate that genetic and environmental factors could play a relevant role in pathogenesis. Differential immune response is also offered as a hypothesis that answers to the cause of the disease phenotypes. Tool-like receptor 4 (TLR4) are pattern recognition receptors (PRR), located on the cell surface of leukocytes and interact with the RSV F protein activating these cells for the production of inflammatory mediators. Two single nucleotide polymorphisms (SNPs) in TLR4 which encode substitutions (Asp299Gly and Thr399Ile) in the ectodomain and produced a union with lower affinity for the ligands have been associated with LPS-hyporesponsive phenotype. Objective We prospectively studied infants with bronchiolitis from three geographical regions of Buenos Aires to test the hypothesis that interaction of TLR4 SNPs with environmental LPS modulates RSV disease severity. Methods A prospective case-control study was conducted in Buenos Aires, Argentina between 2003 and 2006 with previously healthy full term infants younger than one year of age. Participating hospitals cared for infants in the Center, West, and South of the city. Initial diagnosis of RSV infection was performed by direct immunofluorescent assay (Light Biodiagnostic). Assessment of LPS environmental levels: Samples from cradle and bed sheets from the bedroom of randomly selected 120 participating infants were collected in fiberglass filters. LPS was assessed by LAL test. Genotyping: DNA was isolated from whole blood samples using the Gentra Puregene kit (Gentra Systems, Minneapolis, MN). TLR4 Asp299Gly and Ile399Thr mutations were assessed by allelic discrimination with preoptimized assays from Applied Biosystems (Applied Biosystems). Cytokine determination: IL-6 and IL-8 levels were measured in nasal aspirates using a microbead array (Becton Dickinson). GATA3, T-bet and TLR4 mRNA expression were assessed in nasal aspirates of 120 randomly selected subjects from all study groups by real time PCR (Applied Biosystems, Foster City, CA). Results We show in 768 infants with bronchiolitis ? 418 caused by RSV- that RSV-disease severity is determined by an interaction of TLR4 genotype with amount of environmental lipopolysaccharide(LPS), and effected through GATA3/T-bet ratios>1. Changes in TLR4 genotype are associated with relevant alterations in TLR4 function (IL-6 and IL-8 production). We describe an association between TLR4 genotype and environmental conditions that effect through a Th2 transcription bias to modulate RSV disease severity. High GATA3/T-bet ratios are associated with severe RSV bronchiolitis. Conclusions Infants with RSV bronchiolitis are exposed to different levels of environmental LPS. TLR4 Asp299Gly and Thr399Ile alleles modulate IL-6 and IL-8 in vivo in RSV-infected infants. The interaction between TLR4 genotype and the environment is associated with severity of RSV bronchiolitis. RSV-mediated inflammation in the lungs is determined by environmental exposures. The TLR4-environment interaction modulates GATA3/T-bet ratios affecting RSV disease severity.