CD8+ T-cell memory induced by successive SARS-CoV-2 mRNA vaccinations is characterized by clonal replenishment [Tetramer TCR-seq]

mRNA vaccines against the Spike glycoprotein of severe acute respiratory syndrome type 2 coronavirus (SARS-CoV-2) elicit strong T-cell responses. However, it is unknown whether the repertoire of memory T cell clones changes between primary and secondary vaccinations. Here, we analyzed the kinetic profile of Spike-reactive T-cell clones before the first dose, one week after the first and second dose, and four weeks after the second dose of the BNT162b mRNA vaccine. Interestingly, a new set of Spike-reactive CD8+ T cell clones exhibited the greatest expansion following secondary vaccination and replaced the clones that had responded to the primary vaccination. Single-cell mRNA/protein/TCR analysis revealed that the first-responder clones exhibited a terminally differentiated phenotype, whereas second-responder clones exhibited an actively proliferating phenotype. These results show that Spike-reactive T cell responses induced by repetitive mRNA vaccination are augmented and maintained by replacement with newly-generated clones with proliferative potential. TCRseq was performed on Spike-specific CD8+ T cells determined by peptide-HLA tetramer assay on PBMC after Pfizer-BNT162b2 mRNA vaccination.

针对严重急性呼吸综合征冠状病毒2型（SARS-CoV-2）刺突糖蛋白的信使RNA（mRNA）疫苗可诱导强烈的T细胞应答。然而，目前尚不明确记忆T细胞克隆库在初次免疫接种与二次免疫接种之间是否会发生改变。本研究针对BNT162b mRNA疫苗，分析了首剂接种前、首剂接种后1周、第二剂接种后1周，以及第二剂接种后4周时，刺突蛋白反应性T细胞克隆的动力学特征。有趣的是，在二次免疫接种后，一组全新的刺突蛋白反应性CD8+ T细胞克隆出现了最为显著的扩增，并取代了初次免疫应答时的克隆群。单细胞mRNA/蛋白质/T细胞受体（TCR）分析结果显示，初次应答克隆群呈现终末分化表型，而二次应答克隆群则表现出活跃增殖的表型。上述结果表明，反复接种mRNA疫苗所诱导的刺突蛋白反应性T细胞应答，可通过替换为具有增殖潜能的新生克隆而得到增强并维持。本研究针对接种辉瑞-BNT162b2 mRNA疫苗的受试者，通过肽-HLA四聚体检测从其外周血单个核细胞（PBMC）中鉴定出刺突蛋白特异性CD8+ T细胞，并对这些细胞开展了T细胞受体测序（TCRseq）。