A general pHLA-CD80 scaffold fusion protein to promote efficient antigen-specific T cell-based immunotherapy

Inadequate antigen-specific T cells activation hampers immunotherapy due to complex antigen presentation. In addition, therapeutic in vivo T cell expansion is constrained by slow expansion rates and limited functionality. Herein, we introduce a model fusion protein termed antigen-presenting cell-mimic fusion protein (APC-mimic), designed to greatly mimicking the natural antigen presentation pattern of antigen-presenting cells and directly expand T cells both in vitro and in vivo. The APC-mimic comprises the cognate peptide-human leukocyte antigen (pHLA) complex and the co-stimulatory marker CD80, which are natural ligands on APCs. Following a single stimulation, APC-mimic leads to an approximately 400-fold increase in the polyclonal expansion of antigen-specific T cells compared with the untreated group in vitro without the requirement for specialized antigen-presenting cells. Through the combination of single-cell TCR sequencing (scTCR-seq) and single-cell RNA sequencing (scRNA-seq), we identify an approximately 600-fold monoclonal expansion clonotype among these polyclonal clonotypes. It also exhibits suitability for in vivo applications confirmed in the OT-1 mouse model. Furthermore, T cells expanded by APC-mimic effectively inhibits tumor growth in adoptive cell transfer (ACT) murine models. These findings pave the way for the versatile APC-mimic platform for personalized therapeutics, enabling direct expansion of polyfunctional antigen-specific T cell subsets in vitro and in vivo.