The BTLA-HVEM axis restricts CAR T cell efficacy in cancer.

The efficacy of T cell-based immunotherapies is limited by immunosuppressive pressures in the tumor microenvironment. Here we show a predominant role for the interaction between BTLA on effector T cells and HVEM (TNFRSF14) on immunosuppressive tumor microenvironment cells, namely regulatory T cells. High BTLA expression in chimeric antigen receptor (CAR) T cells correlated with poor clinical response to treatment. Therefore, we deleted BTLA in CAR T cells and show improved tumor control and persistence in models of lymphoma and solid malignancies. Mechanistically, BTLA inhibits CAR T cells via recruitment of tyrosine phosphatases SHP-1 and SHP-2, upon trans engagement with HVEM. BTLA knockout thus promotes CAR signaling and subsequently enhances effector function. Overall, these data indicate that the BTLA-HVEM axis is a crucial immune checkpoint in CAR T cell immunotherapy and warrants the use of strategies to overcome this barrier.

Immunologic predictors of vaccine responsiveness in patients with lymphoma and CLL.

Patients with B-cell lymphomas have altered cellular components of vaccine responses due to malignancy and therapy, and the optimal timing of vaccination relative to therapy remains unknown. SARS-CoV-2 vaccines created an opportunity for new insights in vaccine timing because patients were challenged with a novel antigen across multiple phases of treatment. We studied serologic mRNA vaccine response in retrospective and prospective cohorts with lymphoma and CLL, paired with clinical and research immune parameters. Reduced serologic response was observed more frequently during active therapies, but non-response was also common within observation and post-treatment groups. Total IgA and IgM correlated with successful vaccine response. In individuals treated with CART-19, non-response was associated with reduced B and T follicular helper cells. Predictors of vaccine response varied by disease and therapeutic group, and therefore further studies of immune health during and after cancer therapies are needed to allow individualized vaccine timing.

Antigen presentation, autoantibody production, and therapeutic targets in autoimmune liver disease.

The liver is an important immunological organ that controls systemic tolerance. The liver harbors professional and unconventional antigen-presenting cells that are crucial for tolerance induction and maintenance. Orchestrating the immune response in homeostasis depends on a healthy and well-toned immunological liver microenvironment, which is maintained by the crosstalk of liver-resident antigen-presenting cells and intrahepatic and liver-infiltrating leukocytes. In response to pathogens or autoantigens, tolerance is disrupted by unknown mechanisms. Intrahepatic parenchymal and nonparenchymal cells exhibit unique antigen-presenting properties. The presentation of microbial and endogenous lipid-, metabolite- and peptide-derived antigens from the gut via conventional and nonconventional mechanisms can educate intrahepatic immune cells and elicit effector responses or tolerance. Perturbation of this balance results in autoimmune liver diseases, such as autoimmune hepatitis, primary biliary cholangitis, and primary sclerosing cholangitis. Although the exact etiologies of these autoimmune liver diseases are unknown, it is thought that the disruption of tolerance towards self-antigens and microbial metabolites and lipids, as well as alterations in bile acid composition, may result in changes in effector cell activation and polarization and may reduce or impair protective anti-inflammatory regulatory T and B cell responses. Additionally, the canonical and noncanonical transmission of antigens and antigen:MHC complexes via trogocytosis or extracellular vesicles between different (non) immune cells in the liver may play a role in the induction of hepatic inflammation and tolerance. Here, we summarize emerging aspects of antigen presentation, autoantibody production, and the application of novel therapeutic approaches in the characterization and treatment of autoimmune liver diseases.

Improved Functionality of Exhausted Intrahepatic CXCR5+ CD8+ T Cells Contributes to Chronic Antigen Clearance Upon Immunomodulation.

Chronic hepatotropic viral infections are characterized by exhausted CD8+ T cells in the presence of cognate antigen in the liver. The impairment of T cell response limits the control of chronic hepatotropic viruses. Immune-modulatory strategies are attractive options to re-invigorate exhausted T cells. However, in hepatotropic viral infections, the knowledge about immune-modulatory effects on the in-situ regulation of exhausted intrahepatic CD8+ T cells is limited. In this study, we elucidated the functional heterogeneity in the pool of exhausted CD8+ T cells in the liver of mice expressing the model antigen Ova in a fraction of hepatocytes. We found a subpopulation of intrahepatic CXCR5+ Ova-specific CD8+ T cells, which are profoundly cytotoxic, exhibiting efficient metabolic functions as well as improved memory recall and self-maintenance. The intrahepatic Ova-specific CXCR5+ CD8+ T cells are possibly tissue resident cells, which may rely largely on OXPHOS and glycolysis to fuel their cellular processes. Importantly, host conditioning with CpG oligonucleotide reinvigorates and promotes exhausted T cell expansion, facilitating complete antigen eradication. The CpG oligonucleotide-mediated reinvigoration may support resident memory T cell formation and the maintenance of CXCR5+ Ova-specific CD8+ T cells in the liver. These findings suggest that CpG oligodinucleotide may preferentially target CXCR5+ CD8+ T cells for expansion to facilitate the revival of exhausted T cells. Thus, therapeutic strategies aiming to expand CXCR5+ CD8+ T cells might provide a novel approach against chronic liver infection.