A single-cell approach to engineer CD8+ T cells targeting cytomegalovirus

Pathogen-specific T Cells: Targeting Old Enemies and New Invaders in Transplantation and Beyond

Adoptive immunotherapy with virus-specific cytotoxic T cells (VSTs) has evolved over the last three decades as a strategy to rapidly restore virus-specific immunity to prevent or treat viral diseases after solid organ or allogeneic hematopoietic cell-transplantation (allo-HCT). Since the early proof-of-principle studies demonstrating that seropositive donor-derived T cells, specific for the commonest pathogens post transplantation, namely cytomegalovirus or Epstein-Barr virus (EBV) and generated by time- and labor-intensive protocols, could effectively control viral infections, major breakthroughs have then streamlined the manufacturing process of pathogen-specific T cells (pSTs), broadened the breadth of target recognition to even include novel emerging pathogens and enabled off-the-shelf administration or pathogen-naive donor pST production. We herein review the journey of evolution of adoptive immunotherapy with nonengineered, natural pSTs against infections and virus-associated malignancies in the transplant setting and briefly touch upon recent achievements using pSTs outside this context.

Single-Cell Transcriptomics Reveals Killing Mechanisms of Antitumor Cytotoxic CD4+ TCR-T Cells

T cell receptor-engineered T cells (TCR-Ts) have emerged as potent cancer immunotherapies. While most research focused on classical cytotoxic CD8⁺ T cells, the application of CD4⁺ T cells in adoptive T cell therapy has gained much interest recently. However, the cytotoxic mechanisms of CD4⁺ TCR-Ts have not been fully revealed. In this study, we obtained an MHC class I-restricted MART-1_27-35-specific TCR sequence based on the single-cell V(D)J sequencing technology, and constructed MART-1_27-35-specific CD4⁺ TCR-Ts and CD8⁺ TCR-Ts. The antitumor effects of CD4⁺ TCR-Ts were comparable to those of CD8⁺ TCR-Ts in vitro and in vivo. To delineate the killing mechanisms of cytotoxic CD4⁺ TCR-Ts, we performed single-cell RNA sequencing and found that classical granule-dependent and independent cytolytic pathways were commonly used in CD4⁺ and CD8⁺ TCR-Ts, while high expression of LTA and various costimulatory receptors were unique features for cytotoxic CD4⁺ TCR-Ts. Further signaling pathway analysis revealed that transcription factors Runx3 and Blimp1/Tbx21 were crucial for the development and killing function of cytotoxic CD4⁺ T cells. Taken together, we report the antitumor effects and multifaceted killing mechanisms of CD4⁺ TCR-Ts, and also indicate that MHC class I-restricted CD4⁺ TCR-Ts could serve as potential adoptive T cell therapies.

Endothelial cell heterogeneity and microglia regulons revealed by a pig cell landscape at single-cell level

Pigs are valuable large animal models for biomedical and genetic research, but insights into the tissue- and cell-type-specific transcriptome and heterogeneity remain limited. By leveraging single-cell RNA sequencing, we generate a multiple-organ single-cell transcriptomic map containing over 200,000 pig cells from 20 tissues/organs. We comprehensively characterize the heterogeneity of cells in tissues and identify 234 cell clusters, representing 58 major cell types. In-depth integrative analysis of endothelial cells reveals a high degree of heterogeneity. We identify several functionally distinct endothelial cell phenotypes, including an endothelial to mesenchymal transition subtype in adipose tissues. Intercellular communication analysis predicts tissue- and cell type-specific crosstalk between endothelial cells and other cell types through the VEGF, PDGF, TGF-β, and BMP pathways. Regulon analysis of single-cell transcriptome of microglia in pig and 12 other species further identifies MEF2C as an evolutionally conserved regulon in the microglia. Our work describes the landscape of single-cell transcriptomes within diverse pig organs and identifies the heterogeneity of endothelial cells and evolutionally conserved regulon in microglia.