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A third vaccination with a single T cell epitope confers protection in a murine model of SARS-CoV-2 infection.

ABSTRACT: Understanding the mechanisms and impact of booster vaccinations are essential in the design and delivery of vaccination programs. Here we show that a three dose regimen of a synthetic peptide vaccine elicits an accruing CD8⁺ T cell response against one SARS-CoV-2 Spike epitope. We see protection against lethal SARS-CoV-2 infection in the K18-hACE2 transgenic mouse model in the absence of neutralizing antibodies, but two dose approaches are insufficient to confer protection. The third vaccine dose of the single T cell epitope peptide results in superior generation of effector-memory T cells and tissue-resident memory T cells, and these tertiary vaccine-specific CD8⁺ T cells are characterized by enhanced polyfunctional cytokine production. Moreover, fate mapping shows that a substantial fraction of the tertiary CD8⁺ effector-memory T cells develop from re-migrated tissue-resident memory T cells. Thus, repeated booster vaccinations quantitatively and qualitatively improve the CD8⁺ T cell response leading to protection against otherwise lethal SARS-CoV-2 infection.

SUBMITTER: Pardieck IN

PROVIDER: S-EPMC9267705 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:SARS-CoV-2 mRNA vaccines, including Pfizer/Biontech BNT162b2, were shown to be effective for COVID-19 prevention, eliciting both robust antibody responses in naive individuals and boosting pre-existing antibody levels in SARS-CoV-2-recovered individuals. However, the magnitude, repertoire, and phenotype of epitope-specific T cell responses to this vaccine, and the effect of vaccination on pre-existing T cell memory in SARS-CoV-2 convalescent patients, are still poorly understood. Thus, in this study we compared epitope-specific T cells elicited after natural SARS-CoV-2 infection, and vaccination of both naive and recovered individuals. We collected peripheral blood mononuclear cells before and after BNT162b2 vaccination and used pools of 18 DNA-barcoded MHC-class I multimers, combined with scRNAseq and scTCRseq, to characterize T cell responses to several immunodominant epitopes, including a spike-derived epitope cross-reactive to common cold coronaviruses. Comparing responses after infection or vaccination, we found that T cells responding to spike-derived epitopes show similar magnitudes of response, memory phenotypes, TCR repertoire diversity, and αβTCR sequence motifs, demonstrating the potency of this vaccination platform. Importantly, in COVID-19-recovered individuals receiving the vaccine, pre-existing spike-specific memory cells showed both clonal expansion and a phenotypic shift towards more differentiated CCR7-CD45RA+ effector cells. In-depth analysis of T cell receptor repertoires demonstrates that both vaccination and infection elicit largely identical repertoires as measured by dominant TCR motifs and receptor breadth, indicating that BNT162b2 vaccination largely recapitulates T cell generation by infection for all critical parameters. Thus, BNT162b2 vaccination elicits potent spike-specific T cell responses in naive individuals and also triggers the recall T cell response in previously infected individuals, further boosting spike-specific responses but altering their differentiation state. Overall, our study demonstrates the potential of mRNA vaccines to induce, maintain, and shape T cell memory through vaccination and revaccination.

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A third vaccination with a single T cell epitope confers protection in a murine model of SARS-CoV-2 infection.

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