Vyasamneni and Kohler et al. developed a novel strategy for identifying and characterizing antigen-specific CD4+ T cells. Heterodimeric, placeholder peptide-loaded proteins for 48 MHC-II alleles were produced, soluble HLA-DM was used to promote on-demand epitope loading, and a fluorescence polarization assay was developed to determine relative epitope binding affinity. Antigen-specific CD4+ T cells were identified by staining with fluorescent, combinatorially coded pMHCII tetramers and were characterized by flow cytometry and sequencing. This system effectively characterized antigen-specific CD4+ T cells related to COVID-19 and neoantigen vaccine-treated cancers.
Contributed by Lauren Hitchings
ABSTRACT: CD4+ T cells are critical to the immune system and perform multiple functions; therefore, their identification and characterization are crucial to better understanding the immune system in both health and disease states. However, current methods rarely preserve their ex vivo phenotype, thus limiting our understanding of their in vivo functions. Here we introduce a flexible, rapid, and robust platform for ex vivo CD4+ T cell identification. By combining MHCII allele purification, allele-independent peptide loading, and multiplexed flow cytometry technologies, we can enable high-throughput personalized CD4+ T cell identification, immunophenotyping, and sorting. Using this platform in combination with single-cell sorting and multimodal analyses, we identified and characterized antigen-specific CD4+ T cells relevant to COVID-19 and cancer neoantigen immunotherapy. Overall, our platform can be used to detect and characterize CD4+ T cells across multiple diseases, with potential to guide CD4+ T cell epitope design for any disease-specific immunization strategy.