Viral Specific Factors Contribute to Clinical Respiratory Syncytial Virus Disease Severity Differences in Infants

Copyright: © 2015 Thompson TM, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Background: There is a wide range of severity of respiratory syncytial viral (RSV) disease in previously healthy infants. Host factors have been well demonstrated to contribute to disease severity differences. However the possibility of disease severity differences being produced by factors intrinsic to the virus itself has rarely been studied. Methods: Low-passage isolates of RSV collected prospectively from infants with different degrees of RSV disease severity were evaluated in vitro, holding host factors constant, so as to assess whether isolates induced phenotypically different cytokine/chemokine concentrations in a human lung epithelial cell line. Sixty-seven RSV isolates from previously healthy infants (38 hospitalized for acute RSV infection (severe disease) and 29 never requiring hospitalization (mild disease)) were inoculated into A549, lung epithelial cells at precisely controlled, low multiplicity of infection to mimic natural infection. Cultures were evaluated at 48 hours, 60 hours, and 72 hours to evaluate area under the curve (AUC) cytokine/chemokine induction. Results: Cells infected with isolates from severely ill infants produced higher mean concentrations of all cytokine