To study the transcriptional profile of patients with acute RSV or Influenza infection,children of median age 2.4 months (range 1.5-8.6) hospitalized with acute RSV and influenza virus infection were offered study enrollment after microbiologic confirmation of the diagnosis. Blood samples were collected from them within 42-72 hours of hospitalization. We excluded children with suspected or proven polymicrobial infections, with underlying chronic medical conditions (i.e congenital heart disease, renal insufficiency), with immunodeficiency, or those who received systemic steroids or other immunomodulatory therapies. The RSV cohort consisted of 51 patients with median age of 2 months (range 1.5-3.9) and the influenza cohort had 28 patients with median age of 5.5 months (range 1.4-21). Control samples were obtained from healthy children undergoing elective surgical procedures or at outpatient clinic visits. To exclude viral co-infections we performed nasopharyngeal viral cultures of all subjects. We recruited 10 control patients for the RSV cohort with median age of 6.7 months (range 5-10), and 12 control patients for the influenza cohort with median age of18.5 months (range 10.5-26).

We used microarrays to obtain the transcriptional profile of PBMCs from patients with acute RSV or Influenza infection and compared these signatures with the transcriptional profile of primary airway epithelial cells infected with RSV or Influenza.