Systemic immunostimulation induces glucocorticoid-mediated thymic involution succeeded by rebound hyperplasia which is impaired in aged recipients.

The thymus is the central organ involved with T-cell development and the production of naïve T cells. During normal aging, the thymus undergoes marked involution, reducing naïve T-cell output and resulting in a predominance of long-lived memory T cells in the periphery. Outside of aging, systemic stress responses that induce corticosteroids (CS), or other insults such as radiation exposure, induce thymocyte apoptosis, resulting in a transient acute thymic involution with subsequent recovery occurring after cessation of the stimulus. Despite the increasing utilization of immunostimulatory regimens in cancer, effects on the thymus and naïve T cell output have not been well characterized. Using both mouse and human systems, the thymic effects of systemic immunostimulatory regimens, such as high dose IL-2 (HD IL-2) with or without agonistic anti-CD40 mAbs and acute primary viral infection, were investigated. These regimens produced a marked acute thymic involution in mice, which correlated with elevated serum glucocorticoid levels and a diminishment of naïve T cells in the periphery. This effect was transient and followed with a rapid thymic "rebound" effect, in which an even greater quantity of thymocytes was observed compared to controls. Similar results were observed in humans, as patients receiving HD IL-2 treatment for cancer demonstrated significantly increased cortisol levels, accompanied by decreased peripheral blood naïve T cells and reduced T-cell receptor excision circles (TRECs), a marker indicative of recent thymic emigrants. Mice adrenalectomized prior to receiving immunotherapy or viral infection demonstrated protection from this glucocorticoid-mediated thymic involution, despite experiencing a substantially higher inflammatory cytokine response and increased immunopathology. Investigation into the effects of immunostimulation on middle aged (7-12 months) and advance aged (22-24 months) mice, which had already undergone significant thymic involution and had a diminished naïve T cell population in the periphery at baseline, revealed that even further involution was incurred. Thymic rebound hyperplasia, however, only occurred in young and middle-aged recipients, while advance aged not only lacked this rebound hyperplasia, but were entirely absent of any indication of thymic restoration. This coincided with prolonged deficits in naïve T cell numbers in advanced aged recipients, further skewing the already memory dominant T cell pool. These results demonstrate that, in both mice and humans, systemic immunostimulatory cancer therapies, as well as immune challenges like subacute viral infections, have the potential to induce profound, but transient, glucocorticoid-mediated thymic involution and substantially reduced thymic output, resulting in the reduction of peripheral naive T cells. This can then be followed by a marked rebound effect with naïve T cell restoration, events that were shown not to occur in advanced-aged mice.

Dynamic chromatin architecture identifies new autoimmune-associated enhancers for IL2 and novel genes regulating CD4+ T cell activation.

Genome-wide association studies (GWAS) have identified hundreds of genetic signals associated with autoimmune disease. The majority of these signals are located in non-coding regions and likely impact cis-regulatory elements (cRE). Because cRE function is dynamic across cell types and states, profiling the epigenetic status of cRE across physiological processes is necessary to characterize the molecular mechanisms by which autoimmune variants contribute to disease risk. We localized risk variants from 15 autoimmune GWAS to cRE active during TCR-CD28 co-stimulation of naïve human CD4+ T cells. To characterize how dynamic changes in gene expression correlate with cRE activity, we measured transcript levels, chromatin accessibility, and promoter-cRE contacts across three phases of naive CD4+ T cell activation using RNA-seq, ATAC-seq, and HiC. We identified ~1200 protein-coding genes physically connected to accessible disease-associated variants at 423 GWAS signals, at least one-third of which are dynamically regulated by activation. From these maps, we functionally validated a novel stretch of evolutionarily conserved intergenic enhancers whose activity is required for activation-induced IL2 gene expression in human and mouse, and is influenced by autoimmune-associated genetic variation. The set of genes implicated by this approach are enriched for genes controlling CD4+ T cell function and genes involved in human inborn errors of immunity, and we pharmacologically validated eight implicated genes as novel regulators of T cell activation. These studies directly show how autoimmune variants and the genes they regulate influence processes involved in CD4+ T cell proliferation and activation.

Novel engineered IL-2 Nemvaleukin alfa combined with PD1 checkpoint blockade enhances the systemic anti-tumor responses of radiation therapy.

BACKGROUND: Combining interleukin-2 (IL-2) with radiotherapy (RT) and immune checkpoint blockade (ICB) has emerged as a promising approach to address ICB resistance. However, conventional IL-2 cytokine therapy faces constraints owing to its brief half-life and adverse effects. RDB 1462, the mouse ortholog of Nemvaleukin alfa, is an engineered IL-2 with an intermediate affinity that selectively stimulates antitumor CD8 T and NK cells while limiting regulatory T cell expansion. This study aimed to evaluate the antitumor activity and mechanism of action of the combination of RDB 1462, RT, and anti-PD1 in mouse tumor models. METHODS: Two bilateral lung adenocarcinoma murine models were established using 344SQ-Parental and 344SQ anti-PD1-resistant cell lines. Primary tumors were treated with RT, and secondary tumors were observed for evidence of abscopal effects. We performed immune phenotyping by flow cytometry, analyzed 770 immune-related genes using NanoString, and performed T cell receptor (TCR) repertoire analysis. Serum pro-inflammatory cytokine markers were analyzed by 23-plex kit. RESULTS: Compared to native IL-2 (RDB 1475), RDB 1462 demonstrated superior systemic antitumoral responses, attributable, at least in part, to augmented levels of CD4 and CD8 T cells with the latter. Our findings reveal substantial reductions in primary and secondary tumor volumes compared to monotherapy controls, with some variability observed among different dosing schedules of RDB 1462 combined with RT. Blood and tumor tissue-based flow cytometric phenotyping reveals an increase in effector memory CD8 and CD4 T cells and a decrease in immunosuppressive cells accompanied by a significant increase in IL-2, IFN-γ, and GM-CSF levels in the combination group. Transcriptomic profiling and TCR sequencing reveal favorable gene expression and T cell repertoire patterns with the dual combination. Furthermore, integrating anti-PD1 therapy with RT and RDB 1462 further reduced primary and secondary tumor volumes, prolonged survival, and decreased lung metastasis. Observations of immune cell profiles indicated that RT with escalating doses of RDB 1462 significantly reduced tumor growth and increased tumor-specific immune cell populations. CONCLUSION: The addition of Nemvaleukin therapy may enhance responses to RT alone and in combination with anti-PD1.

IL-2 delivery to CD8+ T cells during infection requires MRTF/SRF-dependent gene expression and cytoskeletal dynamics.

Paracrine IL-2 signalling drives the CD8 + T cell expansion and differentiation that allow protection against viral infections, but the underlying molecular events are incompletely understood. Here we show that the transcription factor SRF, a master regulator of cytoskeletal gene expression, is required for effective IL-2 signalling during L. monocytogenes infection. Acting cell-autonomously with its actin-regulated cofactors MRTF-A and MRTF-B, SRF is dispensible for initial TCR-mediated CD8+ T cell proliferation, but is required for sustained IL-2 dependent CD8+ effector T cell expansion, and persistence of memory cells. Following TCR activation, Mrtfab-null CD8+ T cells produce IL-2 normally, but homotypic clustering is impaired both in vitro and in vivo. Expression of cytoskeletal structural and regulatory genes, most notably actins, is defective in Mrtfab-null CD8+ T cells. Activation-induced cell clustering in vitro requires F-actin assembly, and Mrtfab-null cell clusters are small, contain less F-actin, and defective in IL-2 retention. Clustering of Mrtfab-null cells can be partially restored by exogenous actin expression. IL-2 mediated CD8+ T cell proliferation during infection thus depends on the control of cytoskeletal dynamics and actin gene expression by MRTF-SRF signalling.

Phase I Study of Simlukafusp Alfa (FAP-IL2v) with or without Atezolizumab in Japanese Patients with Advanced Solid Tumors.

PURPOSE: The aim of the study was to evaluate the safety/tolerability and pharmacokinetics of simlukafusp alfa (FAP-IL2v), an immunocytokine containing an anti-fibroblast activation protein-α (FAP) antibody and an IL2 variant, administered alone or with the PDL1 inhibitor atezolizumab, in Japanese patients with advanced solid tumors. PATIENTS AND METHODS: In this phase 1, open-label, dose-escalation study, patients received i.v. FAP-IL2v at 10 or 15/20 mg alone or 10 mg when combined with i.v. atezolizumab. The primary objectives were identification of dose-limiting toxicities (DLT), recommended dose, and maximum tolerated dose, and evaluation of the safety/tolerability and pharmacokinetics of FAP-IL2v alone and combined with atezolizumab. RESULTS: All 11 patients experienced adverse events (AE) during FAP-IL2v treatment. Although most AEs were of mild severity, four treatment-related AEs led to study treatment discontinuation in two patients: one with infusion-related reaction, hypotension, and capillary leak syndrome, and the other with increased aspartate aminotransferase. No AE-related deaths occurred. One DLT (grade 3 hypotension) occurred in a patient receiving FAP-IL2v 15/20 mg alone. The recommended dose and maximum tolerated dose could not be determined. The pharmacokinetics of FAP-IL2v remained similar with or without atezolizumab. The study was terminated early as FAP-IL2v development was discontinued because of portfolio prioritization (not for efficacy/safety reasons). CONCLUSIONS: This study describes the safety/tolerability of FAP-IL2v 10 mg alone and in combination with atezolizumab in Japanese patients with advanced solid tumors; one DLT (hypotension) occurred with FAP-IL2v 15/20 mg. However, dose escalation of FAP-IL2v was not conducted because of early study termination. SIGNIFICANCE: This phase I study assessed the safety/tolerability and PK of simlukafusp alfa alone or combined with atezolizumab in Japanese patients with advanced solid tumors. No notable differences in PK were noted with the combination versus simlukafusp alfa alone; however, high-dose simlukafusp alfa treatment was associated with recombinant IL2-related toxicity, despite the drug's FAP targeting and IL2Rßγ-biased IL2 variant design.

Nanoparticles loaded with IL-2 and TGF-ß promote transplantation tolerance to alloantigen.

We have previously reported that nanoparticles (NPs) loaded with IL-2 and TGF-ß and targeted to T cells induced polyclonal T regulatory cells (Tregs) that protected mice from graft-versus-host disease (GvHD). Here, we evaluated whether administration of these NPs during alloantigen immunization could prevent allograft rejection by converting immunogenic responses to tolerogenic ones. Using C57BL/6 mice and BALB/c mice as either donors or recipients of allogeneic splenocytes, we found that treatment with the tolerogenic NPs in both strains of mice resulted in a marked inhibition of mixed lymphocyte reaction (MLR) to donor cell alloantigen but not to third-party control mouse cells after transfer of the allogeneic cells. The decreased alloreactivity associated with a four- to fivefold increase in the number of CD4+ and CD8+ T regulatory cells (Tregs) and the acquisition of a tolerogenic phenotype by recipient dendritic cells (DCs) in NP-treated mice. As allogeneic cells persisted in NP-treated mice, these findings suggest that tolerogenic NPs can induce alloantigen-specific Tregs and tolerogenic DCs promoting tolerogenic responses to alloantigen. By inhibiting reactivity to allotransplant, this approach could help reduce the need for immune suppression for the maintenance of allografts.

The role of interleukin-2 in graft-versus-host disease pathogenesis, prevention and therapy.

Graft-versus-host disease (GVHD) is a significant complication following allogeneic hematopoietic cell transplantation (allo-HCT), posing substantial risks to patient survival. In the late follow-up phase of transplanted patients, GVHD is also a major cause of morbidity and disability, mostly due to low response to first-line steroids and the lack of effective standard therapies in the second line. This review provides a description of GVHD pathogenesis, with a focus on the central role of Interleukin-2 (IL-2). IL-2 is one of the critical mediators in the complex pathogenesis of GVHD, contributing to the intricate balance between regulatory T cells (Tregs) and effector T cells (Teffs). Due to this pivotal role, several studies investigate the potential of IL-2 as a therapeutic option for GVHD management. We discuss the outcomes of low-dose IL-2 therapies and their impact on Treg proliferation and steroid dependency reduction. Additionally, the effects of combining IL-2 with other treatments, such as extracorporeal photopheresis (ECP) and Treg-enriched lymphocyte infusions, are highlighted. Novel approaches, including modified IL-2 complexes and IL-2 receptor blockade, are explored for their potential in selectively enhancing Treg function and limiting Teff activation. The evolving understanding of IL-2's pivotal role in immune regulation presents promising prospects for applying treatment and prevention strategies for GVHD.

Development of bioassay platforms for biopharmaceuticals using Jurkat-CAR cells by AICD.

The assessment of bioactivity for therapeutic antibody release assay poses challenges, particularly when targeting immune checkpoints. An in vitro bioassay platform was developed using the chimeric antigen receptor on Jurkat cells (Jurkat-CAR) to analyze antibodies targeting immune checkpoints, such as CD47/SIRPα, VEGF/VEGFR1, PD-1/PD-L1, and CD70/CD27. For CD47/SIRPα, the platform involved a Jurkat-CAR cell line expressing the chimeric SIRPα receptor (CarSIRPα). CarSIRPα was created by sequentially fusing the SIRPα extracellular region with the CD8α hinge region, the transmembrane (TM) and intracellular (IC) domains of CD28, and the intracellular signaling domain of CD3ζ. The resulting Jurkat-CarSIRPα cells can undergo "activation-induced cell death (AICD)" upon incubation with purified or cellular CD47, as evidenced by the upregulation of CD69, IL-2, and IFN-γ. Similar results also appeared in Jurkat CarVEGFR1, Jurkat CarPD1 and Jurkat CARCD27 cells. These cells are perfectly utilized for the bioactivity analysis of therapeutic antibody. Our study indicates that the established in vitro assay platform based on Jurkat-CAR has been confirmed repeatedly and has shown robust reproducibility; thus, this platform can be used for screening or for release assays of given antibody drugs targeting immune checkpoints.

The immunomodulatory effects of cannabidiol on Hsp70-activated NK cells and tumor target cells.

BACKGROUND: Cannabidiol (CBD), the major non-psychoactive component of cannabis, exhibits anti-inflammatory properties, but less is known about the immunomodulatory potential of CBD on activated natural killer (NK) cells and/or their targets. Many tumor cells present heat shock protein 70 (Hsp70) on their cell surface in a tumor-specific manner and although a membrane Hsp70 (mHsp70) positive phenotype serves as a target for Hsp70-activated NK cells, a high mHsp70 expression is associated with tumor aggressiveness. This study investigated the immuno-modulatory potential of CBD on NK cells stimulated with TKD Hsp70 peptide and IL-2 (TKD+IL-2) and also on HCT116 p53wt and HCT116 p53-/- colorectal cancer cells exhibiting high and low basal levels of mHsp70 expression. RESULTS: Apart from an increase in the density of NTB-A and a reduced expression of LAMP-1, the expression of all other activatory NK cell receptors including NKp30, NKG2D and CD69 which are significantly up-regulated after stimulation with TKD+IL-2 remained unaffected after a co-treatment with CBD. However, the release of major pro-inflammatory cytokines by NK cells such as interferon-γ (IFN-γ) and the effector molecule granzyme B (GrzB) was significantly reduced upon CBD treatment. With respect to the tumor target cells, CBD significantly reduced the elevated expression of mHsp70 but had no effect on the low basal mHsp70 expression. Expression of other NK cell ligands such as MICA and MICB remained unaffected, and the NK cell ligands ULBP and B7-H6 were not expressed on these target cells. Consistent with the reduced mHsp70 expression, treatment of both effector and target cells with CBD reduced the killing of high mHsp70 expressing tumor cells by TKD+IL-2+CBD pre-treated NK cells but had no effect on the killing of low mHsp70 expressing tumor cells. Concomitantly, CBD treatment reduced the TKD+IL-2 induced increased release of IFN-γ, IL-4, TNF-α and GrzB, but CBD had no effect on the release of IFN-α when NK cells were co-incubated with tumor target cells. CONCLUSION: Cannabidiol (CBD) may potentially diminish the anti-tumor effectiveness of TKD+IL-2 activated natural killer (NK) cells.

Interleukin-2 immunotherapy reveals human regulatory T cell subsets with distinct functional and tissue-homing characteristics.

Due to its stimulatory potential for immunomodulatory CD4+ regulatory T (Treg) cells, low-dose interleukin-2 (IL-2) immunotherapy has gained considerable attention for the treatment of autoimmune diseases. In this investigator-initiated single-arm non-placebo-controlled phase-2 clinical trial of low-dose IL-2 immunotherapy in systemic lupus erythematosus (SLE) patients, we generated a comprehensive atlas of in vivo human immune responses to low-dose IL-2. We performed an in-depth study of circulating and cutaneous immune cells by imaging mass cytometry, high-parameter flow cytometry, transcriptomics, and targeted serum proteomics. Low-dose IL-2 stimulated various circulating immune cells, including Treg cells with a skin-homing phenotype that appeared in the skin of SLE patients in close interaction with endothelial cells. Analysis of surface proteins and transcriptomes revealed different IL-2-driven Treg cell activation programs, including gut-homing CD38+, skin-homing HLA-DR+, and highly proliferative inflammation-homing CD38+ HLA-DR+ Treg cells. Collectively, these data define the distinct human Treg cell subsets that are responsive to IL-2 immunotherapy.

Dissecting the mediating role of inflammatory factors in the interaction between metabolites and sepsis: insights from bidirectional Mendelian randomization.

Sepsis, a life-threatening condition, involves complex interactions among metabolic alterations, inflammatory mediators, and host responses. This study utilized a bidirectional Mendelian randomization approach to investigate the causal relationships between 1400 metabolites and sepsis, and the mediating role of inflammatory factors. We identified 36 metabolites significantly associated with sepsis (p < 0.05), with AXIN1, FGF-19, FGF-23, IL-4, and OSM showing an inverse association, suggesting a protective role, while IL-2 exhibited a positive correlation, indicating a potential risk factor. Among these metabolites, Piperine and 9-Hydroxystearate demonstrated particularly interesting protective effects against sepsis. Piperine's protective effect was mediated through its interaction with AXIN1, contributing to a 16.296% reduction in sepsis risk. This suggests a potential pathway where Piperine influences sepsis outcomes by modulating AXIN1 levels. 9-Hydroxystearate also exhibited a protective role against sepsis, mediated through its positive association with FGF-19 and negative association with IL-2, contributing 9.436% and 12.565%, respectively, to its protective effect. Experimental validation confirmed significantly elevated IL-2 levels and reduced FGF-19, AXIN1, piperine, and 9-hydroxyoctadecanoic acid levels in sepsis patients compared to healthy controls. Piperine levels positively correlated with AXIN1, while 9-hydroxyoctadecanoic acid levels negatively correlated with IL-2 and positively correlated with FGF-19, supporting the Mendelian randomization findings. Our findings provide insights into the molecular mechanisms of sepsis, highlighting the unique roles and contributions of specific metabolites and their interactions with inflammatory mediators. This study enhances our understanding of sepsis pathophysiology and opens avenues for targeted therapeutic interventions and biomarker development for sepsis management. However, further research is essential to validate these pathways across diverse populations and fully explore the roles of these metabolites in sepsis.

Engineered cytokine/antibody fusion proteins improve IL-2 delivery to pro-inflammatory cells and promote antitumor activity.

Progress in cytokine engineering is driving therapeutic translation by overcoming these proteins' limitations as drugs. The IL-2 cytokine is a promising immune stimulant for cancer treatment but is limited by its concurrent activation of both pro-inflammatory immune effector cells and antiinflammatory regulatory T cells, toxicity at high doses, and short serum half-life. One approach to improve the selectivity, safety, and longevity of IL-2 is complexing with anti-IL-2 antibodies that bias the cytokine toward immune effector cell activation. Although this strategy shows potential in preclinical models, clinical translation of a cytokine/antibody complex is complicated by challenges in formulating a multiprotein drug and concerns regarding complex stability. Here, we introduced a versatile approach to designing intramolecularly assembled single-agent fusion proteins (immunocytokines, ICs) comprising IL-2 and a biasing anti-IL-2 antibody that directs the cytokine toward immune effector cells. We optimized IC construction and engineered the cytokine/antibody affinity to improve immune bias. We demonstrated that our IC preferentially activates and expands immune effector cells, leading to superior antitumor activity compared with natural IL-2, both alone and combined with immune checkpoint inhibitors. Moreover, therapeutic efficacy was observed without inducing toxicity. This work presents a roadmap for the design and translation of cytokine/antibody fusion proteins.

Establishment of a protocol for rapidly expanding Epstein-Barr-virus-specific cytotoxic T cells with enhanced cytotoxicity.

BACKGROUND: Lytic Epstein-Barr virus (EBV) infection plays a major role in the pathogenesis of nasopharyngeal carcinoma (NPC). For patients with recurrent or metastatic NPC and resistant to conventional therapies, adoptive cell therapy using EBV-specific cytotoxic T cells (EBV-CTLs) is a promising option. However, the long production period (around 3 to 4 weeks) and low EBV-CTL purity (approximately 40% of total CD8 T cells) in the cell product limits the application of EBV-CTLs in clinics. Thus, this study aimed to establish a protocol for the rapid production of EBV-CTLs. METHODS: By culturing peripheral blood mononuclear cells (PBMCs) from EBV-seropositive donors with EBV-specific peptides and interleukin (IL)-2, IL-15, and interferon α (IFN-α) for 9 days, we identified that IL-15 can enhance IL-2-mediated CTL activation and significantly increase the yield of CTLs. RESULTS: When IFN-α was used in IL-2/IL-15-mediated CTL production from days 0 to 6, the productivity of EBV-CTLs and EBV-specific cytotoxicity significantly were reinforced relative to EBV-CTLs from IL-2/IL-15 treatment. Additionally, IFN-α-induced production improvement of virus-specific CTLs was not only the case for EBV-CTLs but also for cytomegalovirus-specific CTLs. CONCLUSION: We established a novel protocol to rapidly expand highly pure EBV-CTLs from PBMCs, which can produce EBV-CTLs in 9 days and does not require feeder cells during cultivation.

Lymphotoxin limits Foxp3+ regulatory T cell development from Foxp3lo precursors via IL-4 signaling.

Regulatory T cells (Treg) are critical players of immune tolerance that develop in the thymus via two distinct developmental pathways involving CD25+Foxp3- and CD25-Foxp3lo precursors. However, the mechanisms regulating the recently identified Foxp3lo precursor pathway remain unclear. Here, we find that the membrane-bound lymphotoxin α1ß2 (LTα1ß2) heterocomplex is upregulated during Treg development upon TCR/CD28 and IL-2 stimulation. We show that Lta expression limits the maturational development of Treg from Foxp3lo precursors by regulating their proliferation, survival, and metabolic profile. Transgenic reporter mice and transcriptomic analyses further reveal that medullary thymic epithelial cells (mTEC) constitute an unexpected source of IL-4. We demonstrate that LTα1ß2-lymphotoxin ß receptor-mediated interactions with mTEC limit Treg development by down-regulating IL-4 expression in mTEC. Collectively, our findings identify the lymphotoxin axis as the first inhibitory checkpoint of thymic Treg development that fine-tunes the Foxp3lo Treg precursor pathway by limiting IL-4 availability.

Development of a highly sensitive platform for protein-protein interaction detection and regulation of T cell function.

We developed a highly sensitive assay for detecting protein-protein interaction using chimeric receptors comprising two molecules of interest in the extracellular domain and interferon alpha and beta receptor subunit 1 or 2 (IFNAR1/2) in the intracellular domain. This intracellular IFNAR1/2 reconstitution system (IFNARRS) proved markedly more sensitive than the NanoBiT system, currently considered one of the best detection systems for protein interaction. Employing chimeric receptors with extracellular domains from the IFNγ or IL-2 receptor and the intracellular domains of IFNAR1/2, the IFNARRS system effectively identifies low IFNγ or IL-2 levels. Cells stably expressing these chimeric receptors responded to IFNγ secreted by activated T cells following various stimuli, including a specific peptide-antigen. The activation signals were further enhanced by the expression of relevant genes, such as costimulators, via IFN-stimulated response elements in the promoters. Besides IFNγ or IL-2, the IFNARRS system demonstrated the capability to detect other cytokines by using the corresponding extracellular domains from these target cytokine receptors.

IL-2 based cancer immunotherapies: an evolving paradigm.

Discovered over 4 decades ago in the supernatants of activated T cells, interleukin-2 (IL-2) is a potent pleiotropic cytokine involved in the regulation of immune responses. It is required for effector T cell expansion and differentiation as well as for peripheral tolerance induced by regulatory T cells. High-dose IL-2 treatment was the first FDA-approved immunotherapy for renal cell carcinoma and melanoma, achieving single agent complete and durable responses, albeit only in a small proportion of patients. The therapeutic potential of wild type IL-2 is clinically limited by its short half-life and severe vascular toxicity. Moreover, the activation of regulatory T cells and the terminal differentiation of effector T cells on IL-2 pose additional restrictions. To overcome the toxicity of IL-2 in order to realize its full potential for patients, several novel engineering strategies are being developed and IL-2 based immunotherapy for cancer has emerged as a burgeoning field of clinical and experimental research. In addition, combination of IL-2 with PD-1/L1 pathway blockade shows vastly improved anti-tumor efficacy over either monotherapy in preclinical tumor models. In this review we discuss the biological characteristics of IL-2 and its receptors, as well as its efficacy and treatment limiting toxicities in cancer patients. We also explore the efforts aimed at developing novel and safer IL-2 therapies to harness the full therapeutic potential of this cytokine.

Effect of pseudorabies virus infection on NMDA receptor expression in mice and its role in immunosuppression.

Pseudorabies virus (PRV), an α-herpesvirus, induces immunosuppression and can lead to severe neurological diseases. N-methyl-D-aspartate receptor (NMDAR), an important excitatory nerve receptor in the central nervous system, is linked to various nervous system pathologies. The link between NMDAR and PRV-induced neurological diseases has not been studied. In vivo studies revealed that PRV infection triggers a reduction in hippocampal NMDAR expression, mediated by inflammatory processes. Extensive hippocampal neuronal degeneration was found in mice on the 6th day by hematoxylin-eosin staining, which was strongly correlated with increased NMDAR protein expression. In vitro studies utilizing the CCK-8 assay demonstrated that treatment with an NMDAR antagonist significantly heightened the cytotoxic effects of PRV on T lymphocytes. Notably, NMDAR inhibition did not affect the replication ability of PRV. However, it facilitated the accumulation of pro-inflammatory cytokines in PRV-infected T cells and enhanced the transcription of the CD25 gene through the secretion of interleukin-2 (IL-2), consequently exacerbating immunosuppression. In this study, we found that NMDAR has functional activity in T lymphocytes and is crucial for the inflammatory and immune responses triggered by PRV infection. These discoveries highlight the significant role of NMDAR in PRV-induced neurological disease pathogenesis.