Background/Objectives: Potency testing of clinical-grade lentiviral vectors (LVVs) is critical to support a drug's commercial approval. Careful consideration should be paid to the development of a suitable potency test during the drug's clinical development. We aimed to develop an affordable, quantitative test for our CAR19-LVV, based on a measure of transgene's functional activity. Methods: Several indicators of functional activity of CAR19-LVV were explored in a co-culture setting of CAR-transduced Jurkat cells and CD19-expressing target cells. The selected assay was further developed and subjected to validation. Assay's adaptability to other CAR-encoding LVV and autologous CAR-T cell products was also investigated. Results: Measure of CD69 expression on the membrane of Jurkat-CAR-expressing cells is a specific indicator of CAR functionality. Quantification of CD69 in terms of mean fluorescence intensity (MFI), coupled with an intra-assay standard curve calibration, allows for a quantitative assay with high precision, specificity, robustness, linearity and accuracy. The assay has also shown optimal performance for a CARBCMA-LVV product. Importantly, we show that in primary T cells, CD69 expression reflects CAR-T cell cytotoxicity. After adaptation, we have applied a CD69-based potency test, with simultaneous measurement of CAR-T cell cytotoxicity, to autologous CAR-T cell products, demonstrating the assay's specificity also in this context. Conclusions: We developed a validated, in vitro cell-based potency test, using a quantitative flow-cytometry method, for our CAR19-LVV. The assay is based on the detection of T-cell activation upon CAR binding to antigen, which is a measure of transgene functionality. The assay was easily adapted to another CAR-encoding LVV, targeting a different molecule. Furthermore, the same assay principle can be applied in the context of autologous CAR-T cell products. The quantitative CD69 potency assay shows reduced variability among autologous products compared to the IFNγ assay and allows for simultaneous evaluation of traditional semi-quantitative cytotoxicity, thereby directly evaluating the drug's mechanism of action (MoA) in the same assay.

IFNγ-secreting T cells are central for the maintenance of immune surveillance within the central nervous system (CNS). It was previously reported in healthy donors that the T-cell environment in the CNS induces distinct signatures related to cytotoxic capacity, CNS trafficking, tissue adaptation, and lipid homeostasis. These findings suggested that the CNS milieu consisting predominantly of lipids mediated the metabolic conditions leading to IFNγ-secreting brain CD4 T cells. Here, we demonstrate that the supplementation of CD4+CD45RO+CXCR3+ cells with cholesterol modulates their function and increases IFNG expression. The heightened IFNG expression was mediated by the activation of the serum/glucocorticoid-regulated kinase (SGK1). Inhibition of SGK1 by a specific enzymatic inhibitor significantly reduces the expression of IFNG Our results confirm the crucial role of lipids in maintaining T-cell homeostasis and demonstrate a putative role of environmental factors to induce effector responses in CD4+ effector/memory cells. These findings offer potential avenues for further research targeting lipid pathways to modulate inflammatory conditions.
© 2024 Hanin et al.

Chronic and aberrant nucleic acid sensing causes type I IFN-driven autoimmune diseases, designated type I interferonopathies. We found a significant reduction of regulatory T cells (Tregs) in patients with type I interferonopathies caused by mutations in ADAR1 or IFIH1 (encoding MDA5). We analyzed the underlying mechanisms using murine models and found that Treg-specific deletion of Adar1 caused peripheral Treg loss and scurfy-like lethal autoimmune disorders. Similarly, knock-in mice with Treg-specific expression of an MDA5 gain-of-function mutant caused apoptosis of peripheral Tregs and severe autoimmunity. Moreover, the impact of ADAR1 deficiency on Tregs is multifaceted, involving both MDA5 and PKR sensing. Together, our results highlight the dysregulation of Treg homeostasis by intrinsic aberrant RNA sensing as a potential determinant for type I interferonopathies.

Chimeric antigen receptor (CAR)-T cell immunotherapy is approved in the treatment of hematological malignancies, but remains far from satisfactory in solid tumor treatment due to inadequate intra-tumor CAR-T cell infiltration. Herein, an injectable supramolecular hydrogel system, based on self-assembly between cationic polymer mPEG-PCL-PEI (PPP) conjugated with T cell targeting anti-CD3e f(ab')2 fragment and α-cyclodextrin (α-CD), is designed to load plasmid CAR (pCAR) with a T cell specific CD2 promoter, which successfully achieves in situ fabrication and effective accumulation of CAR-T cells at the tumor site in humanized mice models. More importantly, due to this tumor microenvironment reprogramming, secretion of cellular inflammatory cytokines (interleukin-2 (IL-2), tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ)) or tumor killer protein granzyme B is significantly promoted, which reverses the immunosuppressive microenvironment and significantly enhances the intra-tumor CAR-T cells and cytotoxic T cells infiltration. To the best of the current knowledge, this is a pioneer report of using injectable supramolecular hydrogel for in situ reprogramming CAR-T cells, which might be beneficial for solid tumor CAR-T immunotherapy.
© 2023 Wiley-VCH GmbH.

Glucose limitation and increased lactic acid levels are consequences of the elevated glycolytic activity of tumor cells, and constitute a metabolic barrier for the function of tumor infiltrating effector immune cells. The immune-suppressive functions of regulatory T cells (Tregs) are unobstructed in lactic-acid rich environments. However, the impact of lactic acid on the induction of Tregs remains unknown. We observed increased TGFβ-mediated induction of Forkhead box P3+ (FoxP3+ ) cells in the presence of extracellular lactic acid, in a glycolysis-independent, acidity-dependent manner. These CD4+ FoxP3+ cells expressed Treg-associated markers, including increased expression of CD39, and were capable of exerting suppressive functions. Corroborating these results in vivo, we observed that neutralizing the tumor pH by systemic administration of sodium bicarbonate (NaBi) decreased Treg abundance. We conclude that acidity augments Treg induction and propose that therapeutic targeting of acidity in the tumor microenvironment (TME) might reduce Treg-mediated immune suppression within tumors.
© 2023 Wiley-VCH GmbH.