Background: The clinical manifestations of Hepatitis E virus (HEV) range from self-limiting acute viral hepatitis (AVH) to acute liver failure (ALF). The varied clinical course is thought to be immune-mediated. Toll-like receptors (TLRs) play a central role in sensing and initiating innate antiviral-response and downstream signaling of TLRs modulates cytokine production, thereby playing an important role in determining the disease course.
Objectives: The present study was designed to elucidate the role of TLRs and cytokine production in the immunopathogenesis of HEV.
Study design: Peripheral blood mono-nuclear cells were separated from 50 AVH-HEV, 30 ALF-HEV patients and 50 healthy-controls. One-part of the PBMC was processed for RNA-extraction another pulsed with HEV-ORF2-peptide. Gene-expression levels of TLR (2-4, 7, and 8) were checked using semi-quantitative Real-time-PCR. Cytokine levels were analyzed using Cytokine-Bead-Array. TLR3-silencing experiments were performed and post-silencing cytokine levels were estimated.
Results: TLR3 gene-expression in AVH was significantly higher than ALF (202.4±36.36 Vs 13.71±5.01; p<0.0001). Higher amount of both anti-and pro-inflammatory cytokines; IFNγ, TNF-α, IL10 and TGF-β were detected in the PBMC culture-supernatant of AVH Vs ALF (p<0.0001, p=0.0008, p=0.0002, p<0.0001 respectively). Post-silencing TLR3, significant decrease in IFNγ level was observed in the PBMC culture-supernatant (4.08±1.06 Vs 23.20±12.51; p=N0.0213).
Conclusions: TLR3 and IFNγ were found to play an important role in HEV disease pathogenesis. Patients capable of expressing high levels of TLR 3 and robust IFNγ response are able to limit the disease and recover uneventfully; while the patients with lower expression of TLR3 and IFNγ progress to ALF.
Keywords: Cytokine; HEV-ORF2 peptide; Hepatitis E virus; Peripheral blood mono-nuclear cell; Toll like receptor.
Copyright © 2015. Published by Elsevier B.V.