Viruses (Feb 2022)

Strong SARS-CoV-2 N-Specific CD8<sup>+</sup> T Immunity Induced by Engineered Extracellular Vesicles Associates with Protection from Lethal Infection in Mice

  • Flavia Ferrantelli,
  • Chiara Chiozzini,
  • Francesco Manfredi,
  • Patrizia Leone,
  • Massimo Spada,
  • Antonio Di Virgilio,
  • Andrea Giovannelli,
  • Massimo Sanchez,
  • Andrea Cara,
  • Zuleika Michelini,
  • Maurizio Federico

DOI
https://doi.org/10.3390/v14020329
Journal volume & issue
Vol. 14, no. 2
p. 329

Abstract

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SARS-CoV-2-specific CD8+ T cell immunity is expected to counteract viral variants in both efficient and durable ways. We recently described a way to induce a potent SARS-CoV-2 CD8+ T immune response through the generation of engineered extracellular vesicles (EVs) emerging from muscle cells. This method relies on intramuscular injection of DNA vectors expressing different SARS-CoV-2 antigens fused at their N-terminus with the Nefmut protein, i.e., a very efficient EV-anchoring protein. However, quality, tissue distribution, and efficacy of these SARS-CoV-2-specific CD8+ T cells remained uninvestigated. To fill the gaps, antigen-specific CD8+ T lymphocytes induced by the immunization through the Nefmut-based method were characterized in terms of their polyfunctionality and localization at lung airways, i.e., the primary targets of SARS-CoV-2 infection. We found that injection of vectors expressing Nefmut/S1 and Nefmut/N generated polyfunctional CD8+ T lymphocytes in both spleens and bronchoalveolar lavage fluids (BALFs). When immunized mice were infected with 4.4 lethal doses of 50% of SARS-CoV-2, all S1-immunized mice succumbed, whereas those developing the highest percentages of N-specific CD8+ T lymphocytes resisted the lethal challenge. We also provide evidence that the N-specific immunization coupled with the development of antigen-specific CD8+ T-resident memory cells in lungs, supporting the idea that the Nefmut-based immunization can confer a long-lasting, lung-specific immune memory. In view of the limitations of current anti-SARS-CoV-2 vaccines in terms of antibody waning and efficiency against variants, our CD8+ T cell-based platform could be considered for a new combination prophylactic strategy.

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