Poster Presentation The Australasian Society for Immunology 2017 Annual Scientific Meeting

High affinity single TCR clone drives a terminally differentiated poly-functional cytotoxic T cell response against viral infection contributing to viral clearance (#312)

Auda Eltahla 1 2 , Elizabeth Keoshkerian 1 2 , Curtis CC Cai 1 2 , Kristof Wing 1 2 , Mehdi Rasoli Pirozyan 1 2 , Katherine Kedzierska 3 , Oanh Nguyen 3 , Stephanie Gras 4 , Slivana Gaudieri 5 , Rowena Bull 1 2 , Dirk Busch 6 , Andrew Lloyd 1 , Fabio Luciani 1 2
  1. VISP, Kirby Institute for Infection and Immunity, Sydney, NSW, Australia
  2. University of New South Wales, Sydney, NSW, Australia
  3. Doherty Institute, University of Melbourne, Melbourne, NSW, Australia
  4. Monash University, Melbourne, NSW, Australia
  5. University of Western Australia, Perth, WA, Australia
  6. Technische Universität Munich, , Munich, Germany

Background

Cytotoxic T cells play a pivotal role in protection from viral infection. Better understanding of the heterogeneous phenotypes of T cell subsets evolving during an immune response is timely needed for development of T cell based vaccines that can provide long-term immune protection. We have developed a new approach to identify and link at the single-cell level the functional phenotype, gene expression profile, TCR affinity for the cognate antigen and T cell receptor (TCRαβ) (1).

Results

We studied Ag-specific CD8+ (Ag-)T cell responses longitudinally during acute hepatitis C virus infection until two years post-clearance by single cell sorting tetramer positive populations specific for two autologous HLA-I restricted epitopes (HLA-B*07:02 GPRLGVRAT (GPR) and HLA-A*01:01 ATDALMTGF (ATD). Single cell (sc)RNA-seq combined with index sorting and full length TCRαβ reconstruction showed that the immune response targeting GPR was characterised by a mono-clonal TCRαβ, high IFN-γ production, and a gene profile consistent with a polyclonal response (IFNγ, PRF, GZMA, M, K, TNFα,). Ag-T cells during viremic phase showed simultaneous presence of CD38+HLA-DR+ cells, and memory precursor cells (CD127hi-KLRG1lo). Reversible tetramer staining was utilized to measure the Koff rate, revealing unprecedented high-affinity for the cognate antigen (8.1x10-4 sec-1). The second response (ATD) was associated with lower IFNγ production, highly diverse TCR repertoire, and with reduced affinity for the cognate antigen. Distinct gene signatures characterised these two Ag-T cell responses during acute phase of infection, while the gene expression profile of memory cells 2 years post clearance was similar between the two epitopes.

Discussion

This work shows for the first time in human infection an association between TCR affinity and the differentiation status of Ag-T cells. High-affinity TCR was found to be associated to a rapid onset of a poly-functional and differentiated response, which is likely to significantly contribute to viral clearance

  1. Eltahla et al. Linking the T cell receptor to the single cell transcriptome in Ag-specific human T cells. Immun. Cell Biology 2016 doi:10.1038/icb.2016.16.