Genetic association study for RSV bronchiolitis in infancy at the 5q31 cytokine cluster

BACKGROUND

The pathophysiological basis of severe respiratory syncytial virus (RSV) bronchiolitis in infancy is poorly understood and has hindered vaccine development. Studies implicate the cell-mediated immune response in the pathogenesis of the disease. A recent twin study estimated a heritable contribution of 22% to RSV bronchiolitis. Genetic epidemiology provides a new approach to identifying important immune determinants of disease severity.

METHODS

A comprehensive high-density gene-region association study for severe RSV bronchiolitis in infancy at 5q31 across 11 genes including the Th2-cytokine cluster was performed. A haplotype tagging approach was used to analyse genetic variation at 113 single nucleotide polymorphisms (SNPs) in 780 independent cases and 1045 controls. The study had sufficient power to detect small effects, perform extensive haplotype analysis and analyse both a principal phenotype and a refined age-limited phenotype enriched for first-exposure RSV infection.

RESULTS

SNP associations were found at IL4 and a highly significant risk haplotype was identified across IL13 CNS-1 and IL4 (odds ratio 1.69, p<0.0001), present in both case-control and family-based analyses. All associations were strongest for a phenotype limited to <6 months of age, implicating this locus in primary RSV disease. The same risk haplotype has previously been shown to be associated with increased IL13 expression.

CONCLUSIONS

A haplotype at IL13-1L4, which is associated with increased IL13 production, confers an increased risk of severe primary RSV bronchiolitis in early infancy. This study, together with previous studies implicating the same locus in atopic sensitisation, suggests that primary RSV bronchiolitis and atopy share a genetic contribution at the IL13-IL4 locus.

Growth of long-term survivors of liver transplantation

OBJECTIVE

To assess growth in survivors of liver transplantation.

STUDY DESIGN

Growth was studied in 105 children up to seven years after liver transplantation.

RESULTS

At transplantation, mean height standard deviation score (zH) was -1.22 but 19% of patients were severely growth retarded (height below 0.4th centile). Growth and pubertal retardation were seen in the first six months after liver transplantation. Significant catch up in growth and puberty continued for more than five years. At five years, mean zH was -0.95 and at seven years -0.84. The mean zH of patients at final height was -0.55. zH at six months was predicted by zH and bilirubin at the time of transplantation and prednisolone dose at six months. At four years, zH was predicted by zH at the time of transplantation and the cumulative prednisolone dose. There was no association between zH and age at transplantation, sex, or diagnosis, although those with biliary atresia and those undergoing transplantation under 2 years of age showed more initial growth delay and subsequent catch up. Average age at menarche was 14.2 years.

CONCLUSIONS

The mean height of the group to have reached final height after liver transplantation was on the 27th centile. Those transplanted earlier in childhood are likely to achieve more normal final heights. High steroid dose, poor liver function, and retransplantation are associated with poorer height outcomes. Persisting severe short stature is largely confined to children with severely retarded growth at the time of transplantation. Transient delay in puberty and menarche occur early after transplantation, although appropriate pubertal progress is resumed after two to three years.