BACKGROUND: Epithelial cytokines including IL-25, IL-33 and thymic stromal lymphopoietin (TLSP) are recently established as drivers of type 2 chronic inflammatory diseases such as chronic rhinosinusitis with nasal polyps (CRSwNP). Here, we further confirmed the increased expression of IL-25 in CRSwNP and investigated potential contributors of IL-25 in CRSwNP epithelium. METHODS: Sixty CRSwNP, 25 CRSsNP and 15 healthy control tissues were examined for IL-25 expression and for the accompanying type 2 inflammatory cytokines. We then tested different respiratory virus infections on human nasal epithelial cells (hNECs) for their ability to trigger IL-25 expression. In addition, we subjected hNECs generated from CRSwNP tissues to pretreatment with recombinant interferon-alpha (IFN-α) prior to viral infection to evaluate IFN effects on IL-25 induction. RESULTS: We confirmed that significantly enhanced levels of IL-25 were observed in CRSwNP tissues, and that IL-25 expression correlated with type 2 inflammatory cytokine expression. In vitro, we observed significantly elevated IL-25 in hNECs infected with influenza A virus as early as 24 hours post-infection (hpi), regardless of tissue origin, and IL-25 correlated positively with viral load. While other respiratory viruses exhibited increasing trends of IL-25, these were not significant at the time-points tested. IFN-α treatment of CRSwNP epithelium was found to exert bimodal effects, ie IFN-α treatment alone induced moderate IL-25 expression, whereas IFN-α pretreatment of hNECs before influenza infection significantly diminished IL-25 induction by active influenza virus infection. CONCLUSION: We have authenticated the observation of elevated IL-25 in CRSwNP, which is correlated with type 2 inflammatory cytokines. Notably, we identified influenza virus infection as a potential contributor of IL-25 in both control and CRSwNP epithelium during active infection. This IL-25 induction can be abated by IFN-α pretreatment which ameliorated active influenza infection. TRIAL REGISTRATION: Chictr.org.cn ChiCTR-BON-16010179, Registered 18 December 2016, http://www.chictr.org.cn/showproj.aspx?proj=17331. The authors agree on the sharing of deidentified participant data where it pertains to request directly related to the data in this article when contacted (Haiyu Hong; honghy@mail.sysu.edu.cn).
Induction of IL-25 Expression in Human Nasal Polyp Epithelium by Influenza Virus Infection is Abated by Interferon-Alpha Pretreatment