Cytokino-amplification by respiratory syncytial virus infection in human nasal epithelial cells

Objectives: Respiratory syncytial virus (RSV) is an important cause of upper respiratory infections and is known to play a causal role in the pathogenesis of rhinitis, sinusitis, acute otitis media, and pneumonia. RSV appears to prime the respiratory tract to secondary inciting events, such as bacterial or antigen challenges. To study the proinflammatory priming effects of RSV infection, cytokine expression was measured in well-differentiated human nasal epithelial cells (WD-NE) after RSV infection alone or after subsequent tumor necrosis factor (TNF)-alpha stimulation. Study Design: In vitro investigation. Methods. Human nasal epithelial cells were obtained from surgical specimens and allowed to differentiate in air-liquid interface cultures until ciliation and mucus production were evident. Two experimental paradigms were used. First, accumulation of cytokines in the media was measured by real-time, quantitative reverse-transcriptase polymerase chain reaction (RTPCR) and enzyme-linked immunosorbent assay after RSV infection alone. In the second set of experiments, cytokines were also measured after TNF-alpha stimulation in both RSV-infected and uninfected cultures. Results: RSV infection of WD-NE resulted in significant accumulations of interleukin (IL)-6, IL-8, and RANTES when compared with findings in control samples. Real-time, quantitative RT-PCR demonstrated significant increases in IL-8 gene expression following RSV infection when compared to controls. Secondary TNF-a stimulation following well-established (i.e., 72 h) RSV infection induced marked increases in IL-6, IL-8, and RANTES when compared with both RSV infection alone and TNF-a stimulation alone. Conclusions: These findings suggest that RSV infection primes nasal epithelial cells to secondary proinflammatory challenge, resulting in a hyperimmune response. RSV-induced priming of a hyperimmune response may be important in the pathogenesis of sinusitis, acute otitis media, and pneumonia. Key Words: Respiratory syncytial virus, RSV, nasal epithelium, IL-6, IL-8, RANTES, TNF-alpha.