Proinflammatory cytokine responses induced by influenza A (H5N1) viruses in primary human alveolar and bronchial epithelial cells

Mcw Chan,Ht Long,Wh Chui,Jsm Peiris,Yo Chan,Rwy Chan,Cy Cheung,Llm Poon,Jm Nicholls,Sw Tsao,Y Guan

doi:10.1186/1465-9921-6-135

Abstract

BackgroundFatal human respiratory disease associated with influenza A subtype H5N1 has been documented in Hong Kong, and more recently in Vietnam, Thailand and Cambodia. We previously demonstrated that patients with H5N1 disease had unusually high serum levels of IP-10 (interferon-gamma-inducible protein-10). Furthermore, when compared with human influenza virus subtype H1N1, the H5N1 viruses in 1997 (A/Hong Kong/483/97) (H5N1/97) were more potent inducers of pro-inflammatory cytokines (e.g. tumor necrosis factor-a) and chemokines (e.g. IP-10) from primary human macrophages in vitro, which suggests that cytokines dysregulation may play a role in pathogenesis of H5N1 disease. Since respiratory epithelial cells are the primary target cell for replication of influenza viruses, it is pertinent to investigate the cytokine induction profile of H5N1 viruses in these cells.MethodsWe used quantitative RT-PCR and ELISA to compare the profile of cytokine and chemokine gene expression induced by H5N1 viruses A/HK/483/97 (H5N1/97), A/Vietnam/1194/04 and A/Vietnam/3046/04 (both H5N1/04) with that of human H1N1 virus in human primary alveolar and bronchial epithelial cells in vitro.ResultsWe demonstrated that in comparison to human H1N1 viruses, H5N1/97 and H5N1/04 viruses were more potent inducers of IP-10, interferon beta, RANTES (regulated on activation, normal T cell expressed and secreted) and interleukin 6 (IL-6) in primary human alveolar and bronchial epithelial cells in vitro. Recent H5N1 viruses from Vietnam (H5N1/04) appeared to be even more potent at inducing IP-10 than H5N1/97 virus.ConclusionThe H5N1/97 and H5N1/04 subtype influenza A viruses are more potent inducers of proinflammatory cytokines and chemokines in primary human respiratory epithelial cells than subtype H1N1 virus. We suggest that this hyper-induction of cytokines may be relevant to the pathogenesis of human H5N1 disease.

Highlights

Fatal human respiratory disease associated with influenza A subtype H5N1 has been documented in Hong Kong, and more recently in Vietnam, Thailand and Cambodia
Viruses An influenza virus isolated from a patient with fatal influenza A H5N1 disease in Hong Kong in 1997, A/Hong Kong/483/97 (H5N1/97), viruses from patients with H5N1 disease in Vietnam in 2004, A/Vietnam/1194/04 and A/Vietnam/3046/04 and a human H1N1 virus A/Hong Kong/54/98 (H1N1) were studied
IFnifgeuctrieon4of human type II pneumocytes with human influenza viruses Infection of human type II pneumocytes with human influenza viruses. (A) Purified alveolar epithelial cells were fixed and analyzed by immunofluorescent staining specific for influenza virus nucleoprotein (×150). (B) The influenza M-gene mRNA profiles were assayed after infection

Summary

Introduction

Fatal human respiratory disease associated with influenza A subtype H5N1 has been documented in Hong Kong, and more recently in Vietnam, Thailand and Cambodia. While human-tohuman transmission of the H5N1 subtype influenza virus appears to be inefficient so far, the disease has exceptional severity in those affected with reported mortality rates ranging from 33% in Hong Kong in 1997 to 55% in Thailand and Vietnam in 2004. The reasons for this unusual severity of human disease have remained unclear. The syndromes of acute respiratory distress and multiple organ dysfunction as well as haemophagocytosis have previously been associated with cytokine dysregulation [10,11]

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