Background. The contribution that genetic polymorphisms of Toll-like receptor (TLR) 4 and of CD14 - both of which recognize respiratory syncytial virus (RSV) in the innate immune response - make to RSV bronchiolitis in the Japanese population has not yet been clarified. Methods. This study genotyped 2 TLR4 mutations, Asp299Gly and Thr399Ile, and 2 single-nucleotide polymorphisms (SNPs) of CD14, -550 C/T and -159 C/T, in 54 children with RSV bronchiolitis and in 203 control subjects. CD14 SNPs and the serum level of soluble CD14 (sCD14) also were examined in 67 cord-blood specimens and in serum samples from 73 6-year-old children. Results. No TLR4 mutations were found. The frequencies of both the CC genotype and the C allele of CD14 -550 C/T were significantly higher in children with RSV bronchiolitis than in the control subjects. The serum level of sCD14 was significantly higher in children with the CC genotype of CD14 -550 C/T than in those with the CT and TT genotypes. Conclusions. CD14 -550 C/T, which is related to the serum level of sCD14, is associated with the development of RSV bronchiolitis in the Japanese population. This study's results indicate that, in different ethnic groups, different genetic factors contribute to the development of RSV bronchiolitis.
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