Ellen Janine Kim

Cancer immunotherapies rely on tumor-specific T cells, which arise endogenously in most patients with cancer, but can be low frequency and poorly functional. Methods to specifically identify, expand, and manipulate tumor-specific T cells at the rare frequencies found in peripheral blood would enable new immunotherapeutic strategies. Here, we demonstrate an approach to virally transduce polyclonal tumor-reactive T cells across any MHC haplotype and in the absence of knowing the cognate antigen. By generating lentiviral vectors that selectively transduce cells expressing 4-1BB (CD137), a marker of T cell activation, we can transduce antigen-specific T cells with user-defined genetic cargoes that can selectively expand and track individual clonotypes via single-cell sequencing. Anti-4-1BB lentiviruses (4-1BB LVs) encoding therapeutic cargoes can also enhance antigen-specific T cells to extend survival in a xenograft model of human melanoma and transduce tumor-infiltrating T cells from patients with ovarian cancer. Overall, the 4-1BB LV platform targets antigen-specific T cells in a manner agnostic to both the antigen and presenting MHC, with potential applications in adoptive cell therapy manufacturing and TCR identification. One Sentence Summary: Engineered lentiviral vectors targeting 4-1BB selectively activate, expand, and transduce antigen-specific T cells with immunomodulatory cargo.

Tumor-infiltrating lymphocyte (TIL) therapy has demonstrated that endogenous T cells can be harnessed to initiate effective antitumor responses. Despite clinical promise, current TIL production protocols involve weeks-long ex vivo expansions that can affect treatment efficacy. Therefore, additional tools are needed to engineer TILs to have increased potency while mitigating manufacturing challenges. Here, we present a strategy for pseudotyping retroviruses with peptide–major histocompatibility complexes (pMHCs) for antigen-specific gene delivery to CD8 T cells and validate therapeutic impact in immunocompetent mouse models. We demonstrate that pMHC-targeted viruses specifically deliver function-enhancing cargos while simultaneously activating and expanding antitumor T cells. This targeting precision enables in vivo engineering of tumor-specific T cells, resulting in improved overall survival in B16F10-bearing mice. Together, we have established that pMHC-targeted viruses are efficient vectors for reprogramming and expanding tumor-specific T cells directly in vivo, with the potential to substantially streamline engineered cell therapy production.

Summary: T cell receptors (TCRs) mediate antigen recognition in adaptive immunity, yet large-scale mapping of TCR-antigen interactions remains a major challenge. Current approaches to synthesize and functionally screen TCRs remain technically complex and limited in throughput. We introduce a modular strategy, TCRAFT, to rapidly construct tens of thousands of TCRs for <$1 each while maintaining TCRα-β pairing with >99% accuracy. We integrate this approach with a high-throughput antigen discovery platform to enable library-on-library TCR-antigen screening. We reconstruct and screen 3,808 TCRs from vitiligo lesions, linking TCR specificity to transcriptional phenotypes for antigen-reactive T cells. To demonstrate scalability, we synthesize and screen 30,810 TCRs from donors with pancreatic ductal adenocarcinoma to capture antigen-specific TCRs. This workflow reduces the cost and complexity of large-scale TCR screening, enabling the expansion of the known landscape of antigen-specific TCRs in vitiligo with a method that can be readily extended to other immunological applications.