Activation and differentiation of cognate T cells by a dextran-based antigen-presenting system for cancer immunotherapy.

Immunotherapeutic modulation of antigen-specific T-cell responses instead of the whole repertoire helps avoid immune-related adverse events. We have developed an artificial antigen-presenting system (aAPS) where multiple copies of a multimeric peptide-MHC class I complex presenting a murine class I MHC restricted ovalbumin-derived peptide (signal 1), along with a costimulatory ligand (signal 2) are chemically conjugated to a dextran backbone. Cognate naive CD8+ T cells, when treated with this aAPS underwent significant expansion and showed an activated phenotype. Furthermore, elevated expression of effector cytokines led to the differentiation of these cells to cytotoxic T lymphocytes which resulted in target cell lysis, indicative of the functional efficacy of the aAPS. CD8+ T cells with decreased proliferative potential due to repeated antigenic stimulation could also be re-expanded by the developed aAPS. Thus, the developed aAPS warrants further engineering for future application as a rapidly customizable personalized immunotherapeutic agent, incorporating patient-specific MHC-restricted tumor antigens and different costimulatory signals to modulate both naive and antigen-experienced but exhausted tumor-specific T cells in cancer.

Peptide-MHC complexes: dressing up to manipulate T cells against autoimmunity and cancer.

Antigen-specificity of T cells provides important clues to the pathogenesis of T cell-mediated autoimmune diseases and immune-evasion strategies of tumors. Identification of T cell clones involved in autoimmunity or cancer is achieved with soluble peptide-MHC (pMHC) complex multimers. Importantly, these complexes can also be used to manipulate disease-relevant T cells to restore homeostasis of T cell-mediated immune response. While auto-antigen-specific T cells can be deleted or anergized by T cell receptor engagement with cognate pMHC complexes in the absence of costimulation, integration of these complexes in artificial antigen-presenting systems can activate tumor antigen-specific T cells. Here the authors discuss the advancements in pMHC-complex-mediated immunotherapeutic strategies in autoimmunity and cancer and identify the lacunae in these strategies that need to be addressed to facilitate clinical implementation.

Structural Insights into N-terminal IgV Domain of BTNL2, a T Cell Inhibitory Molecule, Suggests a Non-canonical Binding Interface for Its Putative Receptors.

T cell costimulation is mediated by the interaction of a number of receptors and ligands present on the surface of the T cell and antigen-presenting cell, respectively. Stimulatory or inhibitory signals from these receptor-ligand interactions work in tandem to preserve immune homeostasis. BTNL2 is a type-1 membrane protein that provides inhibitory signal to T cells and plays an important role in several inflammatory and autoimmune diseases. Therefore, manipulation of the molecular interaction of BTNL2 with its putative receptor could provide strategies to restore immune homeostasis in these diseases. Hence, it is imperative to study the structural characteristics of this molecule, which will provide important insights into its function as well. In this study, the membrane-distal ectodomain of murine BTNL2 was expressed in bacteria as inclusion bodies, refolded in vitro and purified for functional and structural characterization. The domain is monomeric in solution as demonstrated by size-exclusion chromatography and analytical ultracentrifugation, and also binds to its putative receptor on naïve B cells and activated T cell subsets. Importantly, for the first time, we report the structure of BTNL2 as determined by solution NMR spectroscopy and also the picosecond-nanosecond timescale backbone dynamics of this domain. The N-terminal ectodomain of BTNL2, which was able to inhibit T cell function as well, exhibits distinctive structural features. The N-terminal ectodomain of BTNL2 has a significantly reduced surface area in the front sheet due to the non-canonical conformation of the CC' loop, which provides important insights into the recognition of its presently unknown binding partner.