In this project we will study the capacity for single nucleotide polymorphisms (SNP) in TLR4 gene to induce varying levels of inflammatory chemokine and cytokine production.

Infection with RSV is the most common cause of respiratory tract illnesses (LRIs) in the first 3 years of life. There are significant social and health care costs associated with RSV-LRIs. More than 3% of US children are hospitalized each year due to RSV and 500 die annually. Several longitudinal studies have also suggested that children who have RSV-LRIs are at substantially increased risk of developing asthma in the first 3 years after infection and bronchial hyperresponsiveness (BHR) many years after the primary infection. Mechanisms involved in RSV disease are not well understood. Recent reports suggest that RSV may initiate the innate immune response through the pattern recognition receptor, Toll like receptor-4 (TLR4). In this project we will study the capacity for single nucleotide polymorphisms (SNP) in TLR4 gene to induce varying levels of inflammatory chemokine and cytokine production. It has been suggested that such a mechanism may result in altered immune responses to RSV infection and different clinical outcomes. This research has direct application to improving our understanding of bronchiolitis in early childhood, particularly those factors that influence severity of the disease, and may have implications for possible therapy of patients with bronchiolitis in the future.

Inclusion Criteria:

1. Parental or sibling history of asthma.
2. Child must be less than 24 months of age.
3. Presence of viral upper or lower respiratory tract symptoms.

Exclusion Criteria:

1. History of recurrent wheezing requiring systemic corticosteroids.
2. Prior history of lung disease.
3. Birth < 36 weeks gestation.
4. Immunodeficiency
5. Treatment with ribavirin, systemic or inhaled corticosteroids during the RSV infection.
6. Congenital heart disease.
7. No history of parental or sibling asthma.
8. Less than 48 hour or more than 5 day duration of viral URI symptoms since the peak symptoms from RSV would be expected to occur from 2-5 days into course of infection.

Children who present with viral upper respiratory infections or bronchiolitis to their primary care physician. Upon consent, children willl have cheek samples for genotyping and nasal secretion samples to determine RSV infection.

Subject withdraw before blood draw on second visit and small numbers recruited lead to small numbers of subjects analyzed.