Expansion of memory Vd2 T cells following SARS-CoV-2 vaccination revealed by temporal single-cell transcriptomics
?d T cells provide rapid cellular immunity against pathogens. Here, we conducted matched single-cell RNA-sequencing and ?d-TCR-sequencing to delineate the molecular changes in ?d T cells during a longitudinal study following mRNA SARS-CoV-2 vaccination. While the first dose of vaccine primes Vd2 T cells, it is the second administration that significantly boosts their immune response. Specifically, the second vaccination uncovers memory features of Vd2 T cells, shaped by the induction of AP-1 family transcription factors and characterized by a convergent central memory signature, clonal expansion, and an enhanced effector potential. This temporally distinct effector response of Vd2 T cells was also confirmed in vitro upon stimulation with SARS-CoV-2 spike-peptides. Indeed, the second challenge triggers a significantly higher production of IFN? by Vd2 T cells. Collectively, our findings suggest that mRNA SARS-CoV-2 vaccination might benefit from the establishment of long-lasting central memory Vd2 T cells to confer protection against SARS-CoV-2 infection. Overall design: Peripheral blood mononuclear cells were isolated from buffy coats of 6 healthy volunteers (3 males and 3 females, age range 25-50 years old) with two doses of mRNA COVID-19 (BNT162b2)–vaccine without previous SARS-CoV-2 infection. PB were longitudinally collecteded for each healthy donor 1 day before the first dose (P0; n=6), 3 days after the first vaccine dose (P1; n=6), 17 days after the first dose (P2; n=5), 3 days after the second dose (P3; n=6), and 3 months following the boost (P4; n=5). PB were analyzed using paired single-cell RNA-seq and ?d TCR-seq technics.