RSV infection of the airway epithelial cell line BEAS-2B stimulate NK cells

Background: RSV infects and replicates in airway epithelial cells which then initiate an immune response. NK cell antiviral properties include both killing virally infected cells and cytokine production acting as an important early source of IFN-γ and TNF-α. How they are activated in human RSV disease is poorly understood. Key NK cell activating and stimulating cytokines include IL-15, the IL-15/IL-15Rα complex, IL-18 and IL-12. Expression of IL-12, IL-18 and IL-15Rα have not previously been studied in RSV infection. Aim: To investigate RSV-induced NK activating cytokines from BEAS-2B cells and how these then influence NK cells in co-culture. Methods: BEAS-2B were infected with RSV A2 at MOI 1 for 24h. NK cells were negatively isolated from healthy adult PBMCs and added to BEAS-2B cells for a further 24h. RNA analysis was performed for IL-15, IFN-γ and TNF-α. Immunofluorescence was used to visualise IL-15 and IL-15Rα in BEAS-2B cells and CD56 and IFN-γ in NK cells. Results: RSV induced IL-15 and IL-15Rα mRNA, had no effect on IL-12 mRNA and reduces IL-18 mRNA at 48h in BEAS-2B cells. IL-15 and IL-15Rα were localised in the Golgi apparatus in non-infected and infected BEAS-2B cells. RSV infected BEAS-2B cells induce NK cell-derived IFN-γ and TNF-α mRNA. Conclusions: Co-localisation of IL-15 and IL-15Rα suggests RSV induces IL-15/IL-15Rα complex formation within the Golgi apparatus or during vesicle transportation. RSV infected BEAS-2B cells stimulated NK cells to express IFN-γ and TNF-α and this suggests airway epithelial cells alone can activate NK cells. Further work will explore the finer details of communication between infected epithelial cells and how NK cell activation may influence the immune response.