Analysis of Antiviral Response in Human Epithelial Cells Infected with Hepatitis E Virus

Abstract

Hepatitis E virus (HEV) is a major cause of enterically transmitted acute hepatitis in developing nations and occurs in sporadic and epidemic forms. The disease may become severe with high mortality (20%) among pregnant women. Due to lack of efficient cell culture system and small animal model, early molecular events of HEV infection are not yet known. In the present study, human lung epithelial cells, A549, were infected with HEV to monitor expression levels of genes/proteins in antiviral pathways. Both live and UV inactivated virus elicited robust induction of inflammatory cytokines/chemokines such as IL-6, IL-8, TNF-α, and RANTES within 12 h of infection. Cells exposed to soluble capsid protein showed no induction suggesting the capsid structure and not the protein being detected as the pathogen pattern by cells. A delayed up-regulation of type I interferon genes only by the live virus at 48 h post HEV infection indicated the need of virus replication. However, absence of secreted interferons till 96 h suggested possible involvement of post-transcriptional regulation of type I IFN expression. HEV infected cells showed activation of both NF-κB and IRF3 transcription factors when seen at protein levels; however, reporter gene assays showed predominant expression via NF-κB promoter as compared to IRF3 promoter. Knockdown experiments done using siRNAs showed involvement of MyD88 and TRIF adaptors in generating antiviral response thus indicating role of TLR2, TLR4 and TLR3 in sensing viral molecules. MAVS knockdown surprisingly enhanced only proinflammatory cytokines and not type I IFNs. This suggested that HEV not only down-regulates RIG-I helicase like receptor mediated IFN induction but also employs MAVS in curtailing host inflammatory response. Our findings uncover an early cellular response in HEV infection and associated molecular mechanisms suggesting the potential role of inflammatory response triggered by HEV infection in host immune response and pathogenesis.

TLR2/MyD88/NF-κB signalling pathway regulates IL-8 production in porcine alveolar macrophages infected with porcine circovirus 2

“…TLR2 expression is upregulated in response to human immunodeficiency virus (HIV)-1, which in turn influences the inflammatory response during the infection (Hernandez et al, 2012). In addition, a hepatitis E virus-induced inflammatory response via TLR2, TLR3 and TLR4 results in robust induction of inflammatory cytokines and chemokines, including IL-8 (Devhare et al, 2013).…”

Maternal and fetal outcome in pregnancy with hepatitis E virus infection

“…4 Devhare et al studied the immune response to HEV infection and observed early cellular response in HEV infection and associated molecular mechanisms suggesting the potential role of the inflammatory response triggered by HEV infection in host immune response and pathogenesis. 29 Tripathy et al found that elevated IL-1 α and sIL-2 receptors α (sIL-2R α) level in the blood are pivotal in the pathogenesis of HEV. They also demonstrated involvement of innate immune response at the site of infection.…”

Hepatitis E virus (HEV)-1 harbouring HEV-4 non-structural protein (ORF1) replicates in transfected porcine kidney cells

“…We have previously infected several cell lines of human origin such as HepG2, PLC/PRF/5, Huh7, S10-3, Caco2 and A549 with genotype 1 virus purified from human stool samples to see their permissiveness (Devhare et al, 2013) and noticed that HepG2/C3A cells become positive for negative strand 8 h post-infection and IFA positive on the 6th day. HepG2/C3A cells have been successfully used by other researchers for HEV infectivity studies (Emerson et al, 2010;Feagins et al, 2011).…”