Poster Presentation 8th Australasian Vaccines & Immunotherapeutics Development Meeting 2020

TCR repertoire and transcriptome differs between optimal HLA-A*02:01- and high-risk HLA-A*24:02-restricted CD8+ T cell immunity against influenza A virus (#206)

So Young Chang 1 , Luca Hensen 1 , Carolien E Van de Sandt 1 , Simone Rizzetto 2 , Fabio Luciani 2 , Thi HO Nguyen 1 , Marios Koutsakos 1 , Katherine Kedzierska 1
  1. Department of Microbiology and Immunology, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Parkville, Victoria, Australia
  2. School of Medical Sciences and The Kirby Institute, UNSW, Sydney, New South Wales, Australia

Influenza viruses circulate annually and cause significant morbidity and mortality during seasonal epidemics. CD8+ T cells provide broad protective immunity against influenza viruses. The quality of CD8+ T cell response against viral infections and its protective capacity can be influenced by Major histocompatibility complex (MHC) class I polymorphisms, binding affinity of T cell receptor (TCR)/peptide-MHC-I complex, functional avidity, and the nature of the TCRαβ repertoire. Here, we assessed at the single cell level, the TCRαβ repertoire and transcriptome of CD8+ T cells against an influenza-specific HLA-A*24:02-PB1498-505 (A24/PB1498) epitope, restricted by a human leukocyte antigen (HLA) allele frequently found in Indigenous Australians and associated with severe influenza disease during the pH1N1 outbreak. Using ex-vivo peptide-HLA tetramer-associated magnetic enrichment (TAME), single-cell multiplex-nested RT-PCR for paired TCRαβ repertoires, and TCRdist analysis of PBMCs from HLA-A*24:02 healthy donors, we assessed the quality of A24/PB1498+CD8+ T cells compared to the HLA-*02:01-M158 epitope, which is the most well-defined and immunodominant human influenza epitope restricted to the most common HLA-allele in Caucasians. We found that the TCRαβ repertoire of A24/PB1498+CD8+ T cells was biased in usage of TRBV9 (42.5%) with variable TRAV segment usage and highly diverse TCRαβ clonotypes. To further understand global qualitative differences between optimal A2/M158 and high-risk A24/PB1498 epitopes, we performed single-cell mRNA sequencing of peptide-HLA tetramer-specific CD8+ T cells  ex vivo and showed that gene expression levels of cytotoxic molecules such as granzyme A, granzyme B and CCL5 were lower in A24/PB1498+CD8+ T cells than in A2/M158+CD8+ T cells. Overall, our findings provide new insights into the mortality-associated HLA-A*24:02 allomorph and suggest strategies to develop universal T cell-mediated vaccines and immunotherapies.