Oral Presentation 8th Australasian Virology Society Meeting and 11th Annual Meeting of the Australian Centre for Hepatitis & HIV Virology Meeting 2015

Identifying T cell epitopes in the HCV Envelope protein using a reverse genomics approach (#53)

Amy Prosser 1 , Silvana Gaudieri 1 2 3 , Rama Gangula 2 , Spyros Kalams 2 , Cody Chastain 2 , Abha Chopra 1 , Andrew Lucas 4 , Uta Eule 1 , Margaret Hellard 5 , Heidi Drummer 5 , Michaela Lucas 1 6 7
  1. Institute for Immunology and Infectious Diseases, Murdoch University, Murdoch, WA, Australia
  2. Division of Infectious Diseases, Department of Medicine, Vanderbilt University, Nashville, Tennessee, U.S.A
  3. School of Anatomy, Physiology and Human Biology, University of Western Australia, Nedlands, WA, Australia
  4. Institute for Respiratory Health, Nedlands, WA, Australia
  5. Burnet Institute, Melbourne, VIC, Australia
  6. School of Medicine and Pharmacology, University of Western Australia, , Nedlands, WA, Australia
  7. School of Pathology and Laboratory Medicine, University of Western Australia, Nedlands, WA, Australia


Introduction: A prophylactic vaccine for Hepatitis C (HCV) remains a clinical need. The Delta3 HCV vaccine candidate is derived from HCV envelope 2 (E2) and elicits genotype (GT) cross-reactive neutralising antibody responses. However, very little is known about the capacity of E2 to elicit GT-specific CD4 and CD8 T cell responses. Using a genetic-based approach, (Gaudieri et al J Virol 2006; Rauch et al Hepatology 2009) we identified HLA Class I and II-associated viral polymorphisms that represent amino-acid variations selected by HLA-restricted T-cell pressure and have been shown to mark in vivo T-cell targets (Pfafferott et al PlosOne 2015).
Methods: E2 sequence from subjects chronically infected with HCV GT1, GT2 and GT3 was obtained. HLA typing of these subjects was available or performed. HLA-associated E2 viral polymorphisms for HLA class I and II were identified and web-based peptide binding prediction programs were used to predict putative T cell epitopes. These potential epitopes are currently being confirmed using IFNgamma ELISpot assays.
Results: Using this approach we have obtained E2 sequences and HLA typing in over 300 subjects. The majority of HCV sequences obtained were for GT1a and GT3a (>100 each), reflecting the GT distribution in the Australian population. Further sequencing for GT1b and GT2 is ongoing. Identification and confirmation of novel E2 epitopes within the HCV genome for GT1a and GT3a by IFNgamma ELISpot is currently underway and results from this analysis will be presented.
Conclusion: Predicting T cell targets based on HLA associated viral polymorphisms is an alternative to mapping T cell responses using overlapping viral peptides and is tailored to the circulating HCV strain seen within a population. Identification of the E2 epitopes will allow for the development of tools to measure T cell responses in subjects vaccinated with the E2 based Delta 3 vaccine in future studies.