SP-A1, SP-A2 and SP-D gene polymorphisms in severe acute respiratory syncytial infection in Chilean infants.

Respiratory syncytial virus (RSV) is the principal pathogen that causes acute lower respiratory tract infection (ALRI) in infants. Severe RSV-ALRI has been associated with the host genetic susceptibility. To assess whether severe RSV disease in infants is associated with certain single nucleotide polymorphism (SNP) into the gene of SP-A1, SP-A2 and SP-D, a prospective study was performed among blood donors and RSV-infected infants aged <or=6 months, considering their severity, according to a strict scoring system. Allele and genotype frequencies were compared using χ(2)-test. Association studies and haplotype analysis were tested by using Armitagës trend test and Unphased 3.0 program. A total of 118 RSV-infected infants and 104 blood donors were enrolled into the study; 59 infants had a severe respiratory disease, 34 children developed a moderate illness and 25 had a mild disease. There was no difference in the allelic and genotypic frequencies of SP-A1, but intragenic haplotypes showed significant differences among infected infants and blood donors (p=0.0021). 1A(0) variant of SP-A2 was the most frequent allele in all groups. Thr(11) allele of SP-D is significantly higher in RSV infants (p=0.028), as given by its higher frequency in severe disease (p=0.046). Heterozygous Thr(11)/Met(11) was significantly more common in infected infants (p=0.037), because it has higher frequency in critically ill children (p=0.017). Thr(160) allele was significantly higher in severe infants compared with blood donors (p=0.046) and infants with mild disease (p=0.018). Thr(11)-Thr(160)-Ser(270) haplotype was significantly more common in RSV-infants, due to severe (p=0.00000034) and moderate disease (p=0.000009). Differences were also found among severe and mild disease (p=0.026). Differences found with other authors, indicate the need for local studies to identify genetic biomarkers of severity.