RESUMEN
Respiratory syncytial virus (RSV) is the major respiratory tract pathogen in infancy. Host-related differences in susceptibility to severe RSV infection suggest that genetic factors may play a role. In this study, a candidate-gene approach was used to study whether the surfactant protein D (SP-D) gene polymorphism associates with severe RSV infection. DNA samples from 84 infants hospitalized for the treatment of RSV bronchiolitis and 93 healthy controls were analyzed. The controls were matched with the cases on the basis of sex, hospital district, date of birth (+/-2 wk) and gestational age at birth (+/-2 wk). Three biallelic SP-D gene polymorphisms were genotyped. Significant differences were observed in the SP-D allele frequencies for amino acid 11 between the RSV infants and their matched controls. The frequency of the allele coding for Met 11 (p = 0.033) was increased in the severe RSV group. The frequency of the homozygous genotype Met/Met for amino acid 11 was increased in the RSV group relative to the controls, whereas the heterozygous genotype tended to be less frequent among the RSV cases than in the matched controls. Conditional logistic regression analysis was used to study whether the confounders, i.e. smoking and number of children in the family, influence the association between the homozygous SP-D genotype for methionine 11 and the risk of RSV bronchiolitis. The results further confirmed this association (p = 0.028). To our knowledge, the present report provides the first evidence of a specific gene associated with susceptibility to severe RSV infection.