Characterization of the Specificity, Functionality, and Durability of Host T‐Cell Responses Against the Full‐Length Hepatitis E Virus

Background and aims: The interplay between host anti-viral immunity and immunopathology during Hepatitis E virus (HEV) infection determines important clinical outcomes. We characterised the specificity, functionality and durability of host T-cell responses against the full-length HEV virus and assessed a novel “Quantiferon” assay for the rapid diagnosis of HEV infection. Methods: 89 volunteers were recruited from Oxford, Truro (UK) and Toulouse (France) including 44 immune-competent patients with acute HEV infection, 18 HEV exposed immunosuppressed organ-transplant recipients (8 with chronic HEV), and 27 healthy volunteers. A genotype 3a peptide library (616 overlapping peptides spanning ORF1-3) was used in IFN-γ T-cell ELISpot assays. CD4+/CD8+ T-cell subsets and polyfunctionality were defined using ICCS and SPICE analysis. Quantification of IFN-γ used whole-blood stimulation with recombinant HEV-capsid protein in the QuantiFERON® kit. Results: HEV specific T-cell responses were detected in 41/44 immune-competent HEV exposed volunteers (median magnitude 397 SFU/106 PBMCs), most frequently targeting ORF2. High-magnitude, polyfunctional CD4 and CD8+ T-cells were detected during acute disease and maintained to 12 years, but these declined over time with CD8+ responses becoming more monofunctional. Low-level responses were detectable in immunosuppressed patients. 23 novel HEV CD4+ and CD8+ T-cell targets were mapped predominantly to conserved genomic regions. Quantiferon testing demonstrated an inverse correlation between IFN-γ production and the time from clinical presentation, providing 100% specificity, 71% sensitivity, (AUROC of 0.86) for HEV exposure at 0.3IU/ml. Conclusion: Robust HEV specific T-cell responses generated during acute disease predominantly target ORF2, but decline in magnitude and polyfunctionality over time. Defining HEV T-cell targets will be important for the investigation of HEV associated autoimmune disease. This article is protected by copyright. All rights reserved.