Frontiers in Immunology (Jan 2020)

Tetramer-Based Enrichment of Preexisting Anti-AAV8 CD8+ T Cells in Human Donors Allows the Detection of a TEMRA Subpopulation

  • Céline Vandamme,
  • Rebecca Xicluna,
  • Leslie Hesnard,
  • Marie Devaux,
  • Nicolas Jaulin,
  • Mickaël Guilbaud,
  • Johanne Le Duff,
  • Célia Couzinié,
  • Philippe Moullier,
  • Xavier Saulquin,
  • Oumeya Adjali

DOI
https://doi.org/10.3389/fimmu.2019.03110
Journal volume & issue
Vol. 10

Abstract

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Pre-existing immunity to AAV capsid may compromise the safety and efficiency of rAAV-mediated gene transfer in patients. Anti-capsid cytotoxic immune responses have proven to be a challenge to characterize because of the scarcity of circulating AAV-specific CD8+ T lymphocytes which can seldom be detected with conventional flow cytometry or ELISpot assays. Here, we used fluorescent MHC class I tetramers combined with magnetic enrichment to detect and phenotype AAV8-specific CD8+ T cells in human PBMCs without prior amplification. We showed that all healthy individuals tested carried a pool of AAV8-specific CD8+ T cells with a CD45RA+ CCR7− terminally-differentiated effector memory cell (TEMRA) fraction. Ex vivo frequencies of total AAV-specific CD8+ T cells were not predictive of IFNγ ELISpot responses but interestingly we evidenced a correlation between the proportion of TEMRA cells and IFNγ ELISpot positive responses. TEMRA cells may then play a role in recombinant AAV-mediated cytotoxicity in patients with preexisting immunity. Overall, our results encourage the development of new methods combining increased detection sensitivity of AAV-specific T cells and their poly-functional assessment to better characterize and monitor AAV capsid-specific cellular immune responses in the perspective of rAAV-mediated clinical trials.

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