Defining T cell receptor repertoires using nanovial-based binding and functional screening.

The ability to selectively bind to antigenic peptides and secrete effector molecules can define rare and low-affinity populations of cells with therapeutic potential in emerging T cell receptor (TCR) immunotherapies. We leverage cavity-containing hydrogel microparticles, called nanovials, each coated with peptide-major histocompatibility complex (pMHC) monomers to isolate antigen-reactive T cells. T cells are captured and activated by pMHCs inducing the secretion of effector molecules including IFN-γ and granzyme B that are accumulated on nanovials, allowing sorting based on both binding and function. The TCRs of sorted cells on nanovials are sequenced, recovering paired αß-chains using microfluidic emulsion-based single-cell sequencing. By labeling nanovials having different pMHCs with unique oligonucleotide-barcodes and secretions with oligo-barcoded detection antibodies, we could accurately link TCR sequences to specific targets and rank each TCR based on the corresponding cell's secretion level. Using the technique, we identified an expanded repertoire of functional TCRs targeting viral antigens with high specificity and found rare TCRs with activity against cancer-specific splicing-enhanced epitopes.

Vortexing-generated high throughput single-cell droplets for facile analysis of multiplexed microRNA dynamic secretion.

Discriminating secretory phenotypes provides a direct, intact, and dynamic way to evaluate the heterogeneity in cell states and activation, which is significant for dissecting non-genetic heterogeneity for human health studies and disease diagnostics. In particular, secreted microRNAs, soluble signaling molecules released by various cells, are increasingly recognized as a critical mediator for cell-cell communication and the circulating biomarkers for disease diagnosis. However, single-cell analysis of secreted miRNAs is still lacking due to the limited available tools. Herein, we realized three-plexed miRNA secretion analysis over four time points from single cells encapsulated in picoliter droplets with extreme simplicity, coupling vortexing-generated single-cell droplets with multiplexed molecular beacons. Notably, our platform only requires pipetting and vortexing steps to finish the assay setup within 5 min with minimal training, and customized software was developed for automatic data quantification. Applying the platform to human cancer cell lines and primary cells revealed previously undifferentiated heterogeneity and paracrine signaling underlying miRNA secretion. This platform can be used to dissect secretion heterogeneity and cell-cell interactions and has the potential to become a widely used tool in biomedical research.