Highly pathogenic avian influenza H5N1 virus delays apoptotic responses via activation of STAT3.

Kenrie P Y Hui,Chris K P Mok,John M Nicholls,Kit M Yuen,J S Malik Peiris,Renee W Y Chan,Michael C W Chan,Man Chun Cheung,Hung Sing Li

doi:10.1038/srep28593

Abstract

Highly pathogenic avian influenza (HPAI) H5N1 virus continues to pose pandemic threat, but there is a lack of understanding of its pathogenesis. We compared the apoptotic responses triggered by HPAI H5N1 and low pathogenic H1N1 viruses using physiologically relevant respiratory epithelial cells. We demonstrated that H5N1 viruses delayed apoptosis in primary human bronchial and alveolar epithelial cells (AECs) compared to H1N1 virus. Both caspase-8 and -9 were activated by H5N1 and H1N1 viruses in AECs, while H5N1 differentially up-regulated TRAIL. H5N1-induced apoptosis was reduced by TRAIL receptor silencing. More importantly, STAT3 knock-down increased apoptosis by H5N1 infection suggesting that H5N1 virus delays apoptosis through activation of STAT3. Taken together, we demonstrate that STAT3 is involved in H5N1-delayed apoptosis compared to H1N1. Since delay in apoptosis prolongs the duration of virus replication and production of pro-inflammatory cytokines and TRAIL from H5N1-infected cells, which contribute to orchestrate cytokine storm and tissue damage, our results suggest that STAT3 may play a previously unsuspected role in H5N1 pathogenesis.

Highlights

Pathogenic avian influenza (HPAI) H5N1 viruses continue to transmit zoonotically with mortality around 53% and pose a pandemic threat[1,2]
HBECs and alveolar epithelial cells (AECs) were infected with influenza A viruses (H1N1/54, H5N1/483, H5N1/1203, H9N2/G1) at a multiplicity of infection of 2 (MOI = 2) so as to ensure most of the cells were infected in synchrony
Necrosis was reported in highly pathogenic influenza virus infected lung in humans[32], in mice[33], and in vitro in differentiated bronchial epithelial cell line[15,34]

Summary

Introduction

Pathogenic avian influenza (HPAI) H5N1 viruses continue to transmit zoonotically with mortality around 53% and pose a pandemic threat[1,2]. There are reports of the differential expression of apoptosis-related genes induced by H1N1 and H5N1 viruses in human lung epithelial cells and in mice[23,24]. Results Infection and replication of influenza A virus in human bronchial (HBECs) and alveolar epithelial cells (AECs).

Results

Conclusion