Control of homeostasis of CD8+ memory T cells by opposing cytokines

IL-15/IL-15Rα-secreting bioengineered adipocytes reactivate NK/CD8+ T cells in ovarian and colon cancer ascites

Malignant ascites (MA) presents a complex clinical challenge, linked inextricably to poor prognosis, chemoresistance, and metastasis of peritoneal carcinomatosis (PC). However, standard therapeutic approaches for managing or preventing MA secondary to PC remain unavailable. Here we display that a bioengineered adipocyte, encapsulating long-chain fatty acids and concurrently secreting IL-15 and IL-15 receptor α (IL-15Rα), markedly extends the half-life and bioactivity of IL-15. The bioengineered adipocyte consists of an IL-15-P2A-IL-15Rα-T2A-mCherry cDNA sequence stable transfected 3T3-F442A preadipocyte cell line and dcosahexaenoic acid (DHA) are simultaneously encapsulated in the lipid droplets of mature adipocytes, which release it into the MA upon tumor cell-triggered lipolysis. We demonstrate that the bioengineered adipocytes led to specific expansion and activation of NK/CD8+ T cells response to the IL-15/IL-15Rα complex in MA, thereby reversing immuno-suppressive phenotype of ascitic immune cells and enabling them to recognize and attack cancer cells. This synergistic therapeutic strategy exhibits therapeutical manipulation of the ascitic immune cells, restores normal immune functioning, and suppresses cancer cell metastasis and tumor growth in ovarian cancer and colon cancer, all while minimizing systemic adverse effects.

T1-T2 Interplay in the Complex Immune Landscape of Severe Asthma

Asthma is orchestrated by an aberrant immune response involving a complex interplay between multiple inflammatory cell types. An increase in Th2 cells in the asthmatic airway is a hallmark of asthma, and biologics blocking their effector functions have been life-changing for many severe asthma patients who poorly respond to immunosuppression by corticosteroids. However, studies in the past decade have highlighted not only other cell types that also produce Th2 cytokines boosting the Type 2/T2 phenotype but also a heightened IFN-γ response, primarily from T cells, referred to as a Type 1/T1 immune response. Data derived from studies of immune cells in the airways and mouse models of severe asthma suggest a role of IFN-γ in corticosteroid resistance, airway hyperreactivity, and also airway remodeling via effects on other cell types including mast cells, eosinophils, airway epithelial cells, and airway smooth muscle cells. The simultaneous presence of T1 and T2 immune responses is detectable in the sickest of asthma patients in whom corticosteroids suppress the T2 but not the T1 response. This article has reviewed our current understanding of the complex T1-T2 interplay in severe asthma highlighting mediators that impact both arms which may be targeted alone or in combination for disease alleviation.

Reconfiguring the immune system to target cancer: Therapies based on T cells, cytokines, and vaccines

Over the years, extensive research has been dedicated to performing in-depth analysis of cancer to uncover the intricate details of its nature - including the types of cancer, causative agents, stimulators of disease progression, factors contributing to poor prognosis, and efficient therapies to restrict the metastatic aggressiveness. This chapter highlights the mechanisms through which different arms of the host immune system - namely cytokines, lymphocytes, antigen-presenting cells (APCs) -can be mobilized to eradicate cancer. Most malignant tumors are either poorly immunogenic, or are harbored in a highly immuno-suppressive microenvironment. This is why reinforcing the host's anti-tumor defenses, through infusion of pro-inflammatory cytokines, tumor antigen-loaded APCs, and anti-tumor cytotoxic cells has emerged as a viable treatment option against cancer. The chapter also highlights the ongoing preclinical and clinical studies in different malignancies and the outcome of various therapies. Although these methods are not foolproof, and antigen escape variants can still evade or develop resistance to customized therapies, they achieve disease stabilization in several cases when conventional treatments fail. In many instances, combination therapies involving cytokines, T cells, and vaccinations prove more effective than monotherapies. The limitations of the current therapies are also discussed, along with ongoing modifications aimed at improving efficacy.

Leveraging long-acting IL-15 agonists for intratumoral delivery and enhanced antimetastatic activity

Introduction

IL-15 agonists hold promise as immunotherapeutics due to their ability to induce the proliferation and expansion of cytotoxic immune cells including natural killer (NK) and CD8+ T cells. However, they generally have short half-lives that necessitate frequent administration to achieve efficacy. To address this limitation, we have developed a half-life extension technology using hydrogel microspheres (MS). Here, the therapeutic is tethered to MSs by a releasable linker with pre-programed cleavage rates. We previously showed the MS conjugate of single-chain IL-15, MS~IL-15, effectively increased the half-life of IL-15 to approximately 1 week and enhanced the pharmacodynamics. We sought to determine whether the same would be true with a MS conjugate of the IL-15 agonist, receptor-linker IL-15 (RLI).

Methods

We prepared a long acting MS conjugate of RLI, MS~RLI. The pharmacokinetics and pharmacodynamics of MS~RLI were measured in C57BL/6J mice and compared to MS~IL-15. The antitumor efficacy of MS~RLI was measured when delivered subcutaneously or intratumorally in the CT26 tumor model and intratumorally in the orthotopic EO771 tumor model.

Results

MS~RLI exhibited a half-life of 30 h, longer than most IL-15 agonists but shorter than MS~IL-15. The shorter than expected half-life of MS~RLI was shown to be due to target-mediated-disposition caused by an IL-15 induced cytokine sink. MS~RLI resulted in very potent stimulation of NK and CD44hiCD8+ T cells, but also caused significant injection-site toxicity that may preclude subcutaneous administration. We thus pivoted our efforts toward studying the MS~RLI for long-acting intra-tumoral therapy, where some degree of necrosis might be beneficial. When delivered intra- tumorally, both MS~IL-15 and MS~RLI had modest anti-tumor efficacy, but high anti- metastatic activity.

Conclusion

Intra-tumoral MS~RLI and MS~RLI combined with systemic treatment with other agents could provide beneficial antitumor and anti-metastatic effects without the toxic effects of systemic IL-15 agonists. Our findings demonstrate that intra-tumorally administered long-acting IL-15 agonists counter two criticisms of loco-regional therapy: the necessity for frequent injections and the challenge of managing metastases.

Astragalus polysaccharide enhances antitumoral effects of chimeric antigen receptor- engineered (CAR) T cells by increasing CD122+CXCR3+PD-1- memory T cells

Chimeric antigen receptor-engineered T (CAR-T) cell therapy of cancer has been a hotspot and promising. However, due to rapid exhaustion, CAR-T cells are less effective in solid tumors than in hematological ones. CD122+CXCR3+ memory T cells are characterized with longevity, self-renewal and great antitumoral capacity. Thus, it's compelling to induce memory CAR-T cells to enhance their efficacy on solid tumors. Astragalus polysaccharide (APS) has reportedly exhibited antitumoral effects. However, it's unclear if APS has an impact on CD8+ memory T cell generation or persistence. Using two human cancer cell lines, here we found that APS significantly improved the persistence of GPC3-targeted CAR-T cells and enhanced their suppression of tumor growth in both Huh7 and HepG2 xenograft models of hepatocellular carcinoma. APS increased CD122+/CXCR3+ memory T cells, but decreased their PD-1+ subset within CD8+ CAR-T cells in tumor-bearing mice, while these effects of APS were also confirmed with in vitro experiments. Moreover, APS augmented the expression of chemokines CXCL9/CXCL10 by the tumor in vivo and in vitro. It also enhanced the proliferation and chemotaxis/migration of CAR-T cells in vitro. Finally, APS promoted the phosphorylation of STAT5 in CD8+ CAR-T cells, whereas inhibition of STAT5 activation reversed these in vitro effects of APS. Therefore, APS enhanced the antitumoral effects of CD8+ CAR-T cells by promoting formation/persistence of CD122+/CXCR3+/PD-1- memory T cells and their migration to the tumor.

IL-15/IL-15Rα-Fc-Fusion Protein XmAb24306 Potentiates Activity of CD3 Bispecific Antibodies through Enhancing T-Cell Expansion

An insufficient quantity of functional T cells is a likely factor limiting the clinical activity of T-cell bispecific antibodies, especially in solid tumor indications. We hypothesized that XmAb24306 (efbalropendekin alfa), a lymphoproliferative interleukin (IL)-15/IL-15 receptor α (IL-15Rα) Fc-fusion protein, may potentiate the activity of T-cell dependent (TDB) antibodies. The activation of human peripheral T cells by cevostamab, an anti-FcRH5/CD3 TDB, or anti-HER2/CD3 TDB resulted in the upregulation of the IL-2/15Rβ (CD122) receptor subunit in nearly all CD8+ and majority of CD4+ T cells, suggesting that TDB treatment may sensitize T cells to IL-15. XmAb24306 enhanced T-cell bispecific antibody-induced CD8+ and CD4+ T-cell proliferation and expansion. In vitro combination of XmAb24306 with cevostamab or anti-HER2/CD3 TDB resulted in significant enhancement of tumor cell killing, which was reversed when T-cell numbers were normalized, suggesting that T-cell expansion is the main mechanism of the observed benefit. Pretreatment of immunocompetent mice with a mouse-reactive surrogate of XmAb24306 (mIL-15-Fc) resulted in a significant increase of T cells in the blood, spleen, and tumors and converted transient anti-HER2/CD3 TDB responses to complete durable responses. In summary, our results support the hypothesis that the number of tumor-infiltrating T cells is rate limiting for the activity of solid tumor-targeting TDBs. Upregulation of CD122 by TDB treatment and the observed synergy with XmAb24306 and T-cell bispecific antibodies support clinical evaluation of this novel immunotherapy combination.

PPARβ/δ-orchestrated metabolic reprogramming supports the formation and maintenance of memory CD8+ T cells

The formation of memory T cells is a fundamental feature of adaptative immunity, allowing the establishment of long-term protection against pathogens. Although emerging evidence suggests that metabolic reprogramming is crucial for memory T cell differentiation and survival, the underlying mechanisms that drive metabolic rewiring in memory T cells remain unclear. Here, we found that up-regulation of the nuclear receptor peroxisome proliferator-activated receptor β/δ (PPARβ/δ) instructs the metabolic reprogramming that occurs during the establishment of central memory CD8+ T cells. PPARβ/δ-regulated changes included suppression of aerobic glycolysis and enhancement of oxidative metabolism and fatty acid oxidation. Mechanistically, exposure to interleukin-15 and expression of T cell factor 1 facilitated activation of the PPARβ/δ pathway, counteracting apoptosis induced by antigen clearance and metabolic stress. Together, our findings indicate that PPARβ/δ is a master metabolic regulator orchestrating a metabolic switch that may be favorable for T cell longevity.

The ATP-exporting channel Pannexin 1 promotes CD8+ T cell effector and memory responses

Sensing of extracellular ATP (eATP) controls CD8+ T cell function. Their accumulation can occur through export by specialized molecules, such as the release channel Pannexin 1 (Panx1). Whether Panx1 controls CD8+ T cell immune responses in vivo, however, has not been previously addressed. Here, we report that T-cell-specific Panx1 is needed for CD8+ T cell responses to viral infections and cancer. We found that CD8-specific Panx1 promotes both effector and memory CD8+ T cell responses. Panx1 favors initial effector CD8+ T cell activation through extracellular ATP (eATP) export and subsequent P2RX4 activation, which helps promote full effector differentiation through extracellular lactate accumulation and its subsequent recycling. In contrast, Panx1 promotes memory CD8+ T cell survival primarily through ATP export and subsequent P2RX7 engagement, leading to improved mitochondrial metabolism. In summary, Panx1-mediated eATP export regulates effector and memory CD8+ T cells through distinct purinergic receptors and different metabolic and signaling pathways.

The ATP-exporting channel Pannexin-1 promotes CD8+ T cell effector and memory responses

Sensing of extracellular ATP (eATP) controls CD8+ T cell function. Their accumulation can occur through export by specialized molecules, such as the release channel Pannexin-1 (Panx1). Whether Panx1 controls CD8+ T cell immune responses in vivo, however, has not been previously addressed. Here, we report that T cell-specific Panx1 is needed for CD8+ T cell responses to viral infections and cancer. We found that CD8-specific Panx1 promotes both effector and memory CD8+ T cell responses. Panx1 favors initial effector CD8+ T cell activation through extracellular ATP (eATP) export and subsequent P2RX4 activation, which helps promote full effector differentiation through extracellular lactate accumulation and its subsequent recycling. In contrast, Panx1 promotes memory CD8+ T cell survival primarily through ATP export and subsequent P2RX7 engagement, leading to improved mitochondrial metabolism. In summary, Panx1-mediated eATP export regulates effector and memory CD8+ T cells through distinct purinergic receptors and different metabolic and signaling pathways.

Self-sufficient primary natural killer cells engineered to express T cell receptors and interleukin-15 exhibit improved effector function and persistence

Background

NK cells can be genetically engineered to express a transgenic T-cell receptor (TCR). This approach offers an alternative strategy to target heterogenous tumors, as NK:TCR cells can eradicate both tumor cells with high expression of HLA class I and antigen of interest or HLA class I negative tumors. Expansion and survival of NK cells relies on the presence of IL-15. Therefore, autonomous production of IL-15 by NK:TCR cells might improve functional persistence of NK cells. Here we present an optimized NK:TCR product harnessed with a construct encoding for soluble IL-15 (NK:TCR/IL-15), to support their proliferation, persistence and cytotoxic capabilities.

Methods

Expression of tumor-specific TCRs in peripheral blood derived NK-cells was achieved following retroviral transduction. NK:TCR/IL-15 cells were compared with NK:TCR cells for autonomous cytokine production, proliferation and survival. NK:BOB1-TCR/IL-15 cells, expressing a HLA-B*07:02-restricted TCR against BOB1, a B-cell lineage specific transcription factor highly expressed in all B-cell malignancies, were compared with control NK:BOB1-TCR and NK:CMV-TCR/IL-15 cells for effector function against TCR antigen positive malignant B-cell lines in vitro and in vivo.

Results

Viral incorporation of the interleukin-15 gene into engineered NK:TCR cells was feasible and high expression of the TCR was maintained, resulting in pure NK:TCR/IL-15 cell products generated from peripheral blood of multiple donors. Self-sufficient secretion of IL-15 by NK:TCR cells enables engineered NK cells to proliferate in vitro without addition of extra cytokines. NK:TCR/IL-15 demonstrated a marked enhancement of TCR-mediated cytotoxicity as well as enhanced NK-mediated cytotoxicity resulting in improved persistence and performance of NK:BOB1-TCR/IL-15 cells in an orthotopic multiple myeloma mouse model. However, in contrast to prolonged anti-tumor reactivity by NK:BOB1-TCR/IL-15, we observed in one of the experiments an accumulation of NK:BOB1-TCR/IL-15 cells in several organs of treated mice, leading to unexpected death 30 days post-NK infusion.

Conclusion

This study showed that NK:TCR/IL-15 cells secrete low levels of IL-15 and can proliferate in an environment lacking cytokines. Repeated in vitro and in vivo experiments confirmed the effectiveness and target specificity of our product, in which addition of IL-15 supports TCR- and NK-mediated cytotoxicity.

CD8+ T cells in fetal membranes display a unique phenotype, and their activation is involved in the pathophysiology of spontaneous preterm birth

Preterm labor/birth is the leading cause of perinatal mortality and morbidity worldwide. Previous studies demonstrated that T cells were crucial for maintaining maternal-fetal immune tolerance during the first trimester of pregnancy; however, their phenotypes and functions in labor and delivery remain largely unknown. We recruited three cohorts of women at delivery for T-cell immunophenotyping in the placentas, fetal membranes, umbilical cord blood, and maternal peripheral blood. Our data showed a differential enrichment of T cells during the third trimester of human pregnancy, with CD4+ T cells being more observable within the umbilical cord blood, whereas CD8+ T cells became relatively more abundant in fetal membranes. CD4+ and CD8+ T cells derived from fetal membranes were dominated by effector memory T cells and exhibited extensive expression of activation markers but decreased expression of homing receptor. In comparison with term births, fetal membrane CD8+ T cells, especially the central memory subset, were significantly increased in frequency and showed more profound activation in spontaneous preterm birth patients. Finally, using an allogeneic mouse model, we found that T-cell-activation-induced preterm birth could be alleviated by the depletion of CD8+ T but not CD4+ T cells in vivo. Collectively, we showed that CD8+ T cells in fetal membranes displayed a unique phenotype, and their activation was involved in the pathophysiology of spontaneous preterm birth, which provides novel insights into the immune mechanisms of preterm birth and potential targets for the prevention of this syndrome. © 2023 The Pathological Society of Great Britain and Ireland.

Novel immunotherapeutic options for BCG-unresponsive high-risk non-muscle-invasive bladder cancer

BACKGROUND

High-risk non-muscle-invasive bladder cancer (HR-NMIBC) presents a challenge to many physicians due to its ability to resist Bacillus Calmette-Guérin (BCG) intravesical therapy and the substantial rate of progression into muscle-invasive bladder cancer (MIBC). Patients who are BCG-unresponsive have worse prognosis and thus require further management including radical cystectomy (RC), which significantly impacts quality of life. Moreover, the ongoing worldwide shortage of BCG warrants the need for policies that prioritize drug use and utilize alternative treatment strategies. Hence, there is a significant unmet need for bladder preserving therapy in this subset of patients.

METHODS

To address this issue, we searched the relevant literature in PUBMED for articles published from 2019 through May of 2023 using appropriate keywords. All clinical trials of patients with HR-NMIBC treated with immune-related agents were retrieved from clinicaltrials.gov.

FINDINGS AND FUTURE PERSPECTIVES

Exploratory treatments for BCG-Unresponsive HR-NMIBC included immune checkpoint inhibitors (ICI), oncolytic viral therapy, cytokine agonists, and other immunomodulators targeting TLR, EpCaM, FGFR, MetAP2, and IDO1. Some combination therapies have been found to work synergistically and are preferred therapeutically over monotherapy. Three drugs-pembrolizumab, valrubicin, and most recently, nadofaragene firadenovec-vncg-have been FDA approved for the treatment of BCG-unresponsive NMIBC in patients who are ineligible for or decline RC. However, all explored treatment options tend to postpone RC rather than provide long-term disease control. Additional combination strategies need to be studied to enhance the effects of immunotherapy. Despite the challenges faced in finding effective therapies, many potential treatments are currently under investigation. Addressing the landscape of biomarkers, mechanisms of progression, BCG resistance, and trial design challenges in HR-NMIBC is essential for the discovery of new targets and the development of effective treatments.

Group 1 metabotropic glutamate receptor expression defines a T cell memory population during chronic Toxoplasma infection that enhances IFN-gamma and perforin production in the CNS

Within the brain, a pro-inflammatory response is essential to prevent clinical disease due to Toxoplasma gondii reactivation. Infection in the immunocompromised leads to lethal Toxoplasmic encephalitis while in the immunocompetent, there is persistent low-grade inflammation which is devoid of clinical symptoms. This signifies that there is a well-balanced and regulated inflammatory response to T. gondii in the brain. T cells are the dominant immune cells that prevent clinical disease, and this is mediated through the secretion of effector molecules such as perforins and IFN-γ. The presence of cognate antigen, the expression of survival cytokines, and the alteration of the epigenetic landscape drive the development of memory T cells. However, specific extrinsic signals that promote the formation and maintenance of memory T cells within tissue are poorly understood. During chronic infection, there is an increase in extracellular glutamate that, due to its function as an excitatory neurotransmitter, is normally tightly controlled in the CNS. Here we demonstrate that CD8+ T cells from the T. gondii-infected brain parenchyma are enriched for metabotropic glutamate receptors (mGluR's). Characterization studies determined that mGluR+ expression by CD8+ T cells defines a distinct memory population at the transcriptional and protein level. Finally, using receptor antagonists and agonists we demonstrate mGluR signaling is required for optimal CD8+ T cell production of the effector cytokine IFNγ. This work suggests that glutamate is an important environmental signal of inflammation that promotes T cell function. Understanding glutamate's influence on T cells in the brain can provide insights into the mechanisms that govern protective immunity against CNS-infiltrating pathogens and neuroinflammation.

Contribution of viral and bacterial infections to senescence and immunosenescence

Cellular senescence is a key biological process characterized by irreversible cell cycle arrest. The accumulation of senescent cells creates a pro-inflammatory environment that can negatively affect tissue functions and may promote the development of aging-related diseases. Typical biomarkers related to senescence include senescence-associated β-galactosidase activity, histone H2A.X phosphorylation at serine139 (γH2A.X), and senescence-associated heterochromatin foci (SAHF) with heterochromatin protein 1γ (HP-1γ protein) Moreover, immune cells undergoing senescence, which is known as immunosenescence, can affect innate and adaptative immune functions and may elicit detrimental effects over the host's susceptibility to infectious diseases. Although associations between senescence and pathogens have been reported, clear links between both, and the related molecular mechanisms involved remain to be determined. Furthermore, it remains to be determined whether infections effectively induce senescence, the impact of senescence and immunosenescence over infections, or if both events coincidently share common molecular markers, such as γH2A.X and p53. Here, we review and discuss the most recent reports that describe cellular hallmarks and biomarkers related to senescence in immune and non-immune cells in the context of infections, seeking to better understand their relationships. Related literature was searched in Pubmed and Google Scholar databases with search terms related to the sections and subsections of this review.

Modulation of T cell function and survival by the tumor microenvironment

Cancer immunotherapy is shifting paradigms in cancer care. T cells are an indispensable component of an effective antitumor immunity and durable clinical responses. However, the complexity of the tumor microenvironment (TME), which consists of a wide range of cells that exert positive and negative effects on T cell function and survival, makes achieving robust and durable T cell responses difficult. Additionally, tumor biology, structural and architectural features, intratumoral nutrients and soluble factors, and metabolism impact the quality of the T cell response. We discuss the factors and interactions that modulate T cell function and survive in the TME that affect the overall quality of the antitumor immune response.

Targeting of chimeric antigen receptor T cell metabolism to improve therapeutic outcomes

Genetically engineered chimeric antigen receptor (CAR) T cells can cure patients with cancers that are refractory to standard therapeutic approaches. To date, adoptive cell therapies have been less effective against solid tumors, largely due to impaired homing and function of immune cells within the immunosuppressive tumor microenvironment (TME). Cellular metabolism plays a key role in T cell function and survival and is amenable to manipulation. This manuscript provides an overview of known aspects of CAR T metabolism and describes potential approaches to manipulate metabolic features of CAR T to yield better anti-tumor responses. Distinct T cell phenotypes that are linked to cellular metabolism profiles are associated with improved anti-tumor responses. Several steps within the CAR T manufacture process are amenable to interventions that can generate and maintain favorable intracellular metabolism phenotypes. For example, co-stimulatory signaling is executed through metabolic rewiring. Use of metabolic regulators during CAR T expansion or systemically in the patient following adoptive transfer are described as potential approaches to generate and maintain metabolic states that can confer improved in vivo T cell function and persistence. Cytokine and nutrient selection during the expansion process can be tailored to yield CAR T products with more favorable metabolic features. In summary, improved understanding of CAR T cellular metabolism and its manipulations have the potential to guide the development of more effective adoptive cell therapies.

IL-15 synergizes with CD40 agonist antibodies to induce durable immunity against bladder cancer

CD40 is a central co-stimulatory receptor implicated in the development of productive anti-tumor immune responses across multiple cancers, including bladder cancer. Despite strong preclinical rationale, systemic administration of therapeutic agonistic antibodies targeting the CD40 pathway have demonstrated dose limiting toxicities with minimal clinical activity to date, emphasizing an important need for optimized CD40-targeted approaches, including rational combination therapy strategies. Here, we describe an important role for the endogenous IL-15 pathway in contributing to the therapeutic activity of CD40 agonism in orthotopic bladder tumors, with upregulation of trans-presented IL-15/IL-15Rα surface complexes, particularly by cross-presenting cDC1s, and associated enrichment of activated CD8 T cells within the bladder tumor microenvironment. In bladder cancer patient samples, we identify DCs as the primary source of IL-15, however, they lack high levels of IL-15Rα at baseline. Using humanized immunocompetent orthotopic bladder tumor models, we demonstrate the ability to therapeutically augment this interaction through combined treatment with anti-CD40 agonist antibodies and exogenous IL-15, including the fully-human Fc-optimized antibody 2141-V11 currently in clinical development for the treatment of bladder cancer. Combination therapy enhances the crosstalk between Batf3-dependent cDC1s and CD8 T cells, driving robust primary anti-tumor activity and further stimulating long-term systemic anti-tumor memory responses associated with circulating memory-phenotype T and NK cell populations. Collectively, these data reveal an important role for IL-15 in mediating anti-tumor CD40 agonist responses in bladder cancer and provide key proof-of-concept for combined use of Fc-optimized anti-CD40 agonist antibodies and agents targeting the IL-15 pathway. These data support expansion of ongoing clinical studies evaluating anti-CD40 agonist antibodies and IL-15-based approaches to evaluate combinations of these promising therapeutics for the treatment of patients with bladder cancer.

A novel anti-PD-L1/IL-15 immunocytokine overcomes resistance to PD-L1 blockade and elicits potent antitumor immunity

Despite the demonstrated immense potential of immune checkpoint inhibitors in various types of cancers, only a minority of patients respond to these therapies. Immunocytokines designed to deliver an immune-activating cytokine directly to the immunosuppressive tumor microenvironment (TME) and block the immune checkpoint simultaneously may provide a strategic advantage over the combination of two single agents. To increase the response rate to checkpoint blockade, in this study, we developed a novel immunocytokine (LH01) composed of the antibody against programmed death-ligand 1 (PD-L1) fused to interleukin (IL)-15 receptor alpha-sushi domain/IL-15 complex. We demonstrate that LH01 efficiently binds mouse or human PD-L1 and maintains IL-15 stimulatory activity. In syngeneic mouse models, LH01 showed improved antitumor efficacy and safety versus anti-PD-L1 plus LH02 (Fc-sushi-IL15) combination and overcame resistance to anti-PD-L1 treatment. Mechanistically, the dual anti-immunosuppressive function of LH01 activated both the innate and adaptive immune responses and induced a favorable and immunostimulatory TME. Furthermore, combination therapy with LH01 and bevacizumab exerts synergistic antitumor effects in an HT29 colorectal xenograft model. Collectively, our results provide supporting evidence that fusion of anti-PD-L1 and IL-15 might be a potent strategy to treat patients with cold tumors or resistance to checkpoint blockade.

Regulatory T-cell-derived interleukin-15 shapes cytotoxic T cell memory

It is well known that regulatory T-cells (Tregs) are required to prevent autoimmunity, but they may also have some less-well understood immune-stimulatory effects. In particular, in CD8⁺ T-cell responses Tregs select high-affinity clones upon priming and promote memory by inhibiting inflammation-dependent generation of short-lived effector cells. In the current issue of the European Journal of Immunology [Eur. J. Immunol. 2023. 53: 2149400], Madi et al. report the surprising finding that human and murine FOXP3⁺ Tregs are a physiologically relevant source of IL-15, a homeostatic cytokine that promotes antigen-independent maintenance of CD8⁺ memory T-cells. In mice that lack IL-15 selectively in FOXP3⁺ Tregs the authors show that the composition of the CD8⁺ T-cell memory pool is altered in the absence of Treg-derived IL-15, since a subset of terminally effector memory cells is drastically reduced. Otherwise Treg-derived IL-15 is dispensable for antiviral immune responses and the generation of anti-viral CD8⁺ memory T-cells. These findings add to our understanding of the multifaceted role of Tregs in immune responses, and how IL-15 derived from different cellular sources maintains anti-viral T-cell memory.

Regulatory T cell-derived interleukin-15 promotes the diversity of immunological memory

While the immunosuppressive function of regulatory T (Treg) cells has been extensively studied, their immune-supportive roles have been less well investigated. Using a lymphocytic choriomeningitis virus (LCMV) Armstrong infection mouse model, we found that Treg cell-derived interleukin (IL)-15 is required for long-term maintenance of the KLRG1⁺ IL-7Rα^- CD62L^- terminal effector memory CD8⁺ T (tTEM) cell subset, but dispensable for the suppressive function of Treg cells themselves. In contrast, deletion of Il15 from other sources, including myeloid cells and muscles, did not affect the composition of the memory CD8⁺ T cell pool. Our findings identify Treg cells as an essential IL-15 source maintaining tTEM cells and suggest that Treg cells promote the diversity of immunological memory.

The application of Interleukin-2 family cytokines in tumor immunotherapy research

The Interleukin-2 Family contains six kinds of cytokines, namely IL-2, IL-15, IL-4, IL-7, IL-9, and IL-21, all of which share a common γ chain. Many cytokines of the IL-2 family have been reported to be a driving force in immune cells activation. Therefore, researchers have tried various methods to study the anti-tumor effect of cytokines for a long time. However, due to the short half-life, poor stability, easy to lead to inflammatory storms and narrow safety treatment window of cytokines, this field has been tepid. In recent years, with the rapid development of protein engineering technology, some engineered cytokines have a significant effect in tumor immunotherapy, showing an irresistible trend of development. In this review, we will discuss the current researches of the IL-2 family and mainly focus on the application and achievements of engineered cytokines in tumor immunotherapy.

STAT3 gain-of-function mutations connect leukemia with autoimmune disease by pathological NKG2Dhi CD8+ T cell dysregulation and accumulation

The association between cancer and autoimmune disease is unexplained, exemplified by T cell large granular lymphocytic leukemia (T-LGL) where gain-of-function (GOF) somatic STAT3 mutations correlate with co-existing autoimmunity. To investigate whether these mutations are the cause or consequence of CD8⁺ T cell clonal expansions and autoimmunity, we analyzed patients and mice with germline STAT3 GOF mutations. STAT3 GOF mutations drove the accumulation of effector CD8⁺ T cell clones highly expressing NKG2D, the receptor for stress-induced MHC-class-I-related molecules. This subset also expressed genes for granzymes, perforin, interferon-γ, and Ccl5/Rantes and required NKG2D and the IL-15/IL-2 receptor IL2RB for maximal accumulation. Leukocyte-restricted STAT3 GOF was sufficient and CD8⁺ T cells were essential for lethal pathology in mice. These results demonstrate that STAT3 GOF mutations cause effector CD8⁺ T cell oligoclonal accumulation and that these rogue cells contribute to autoimmune pathology, supporting the hypothesis that somatic mutations in leukemia/lymphoma driver genes contribute to autoimmune disease.

Anti‐thymocyte globulin‐mediated immunosenescent alterations of T cells in kidney transplant patients

Objectives

Kidney transplant (KT) is the most effective treatment for end‐stage renal disease. The immunosuppressant anti‐thymocyte globulin (ATG) has been applied for induction therapy to reduce the risk of acute transplant rejection for patients at high immunological risk. Despite its putative role in replicative stress during immune reconstitution, the effects of ATG on T‐cell immunosenescent changes remain to be understood.

Methods

Phenotypic and functional features of senescent T cells were examined by flow cytometry in 116 healthy controls (HC) and 95 KT patients for comparative analysis according to ATG treatment and CMV reactivation. The TCR repertoire was analysed in peripheral blood mononuclear cells (PBMCs) of KT patients.

Results

T cells of KT patients treated with ATG (ATG⁺) show typical immunosenescent features, accumulation of CD28⁻, CD85j⁺ or CD57⁺ T cells, and imbalance of functional T‐cell subsets, compared with untreated KT patients (ATG⁻). Plasma IL‐15 and CMV‐IgG levels were higher in KT patients than in HCs, and the IL‐15 level positively correlated with the frequency of CD28⁻ T cells in KT patients. ATG⁺ patients had a higher prevalence of CMV reactivation, which is associated with an increased frequency of CD28⁻ T cells. As a result, ATG⁺ patients had expanded CMV‐specific T cells and decreased TCR diversity. However, proliferation, cytokine‐producing capacity and polyfunctionality of T cells were preserved in ATG⁺ patients.

Conclusion

Our findings suggest that ATG treatment contributes to the accumulation of senescent T cells, which may have lifelong clinical implications in KT patients. Thus, these patients require long‐term and comprehensive immune monitoring.

Responsiveness to interleukin-15 therapy is shared between tissue-resident and circulating memory CD8+ T cell subsets

Interleukin-15 (IL-15) is often considered a central regulator of memory CD8⁺ T cells, based primarily on studies of recirculating subsets. However, recent work identified IL-15-independent CD8⁺ T cell memory populations, including tissue-resident memory CD8⁺ T cells (T_RM) in some nonlymphoid tissues (NLTs). Whether this reflects the existence of IL-15-insensitive memory CD8⁺ T cells is unclear. We report that IL-15 complexes (IL-15c) stimulate rapid proliferation and expansion of both tissue-resident and circulating memory CD8⁺ T cell subsets across lymphoid and nonlymphoid tissues with varying magnitude by tissue and memory subset, in some sites correlating with differing levels of the IL-2Rβ. This was conserved for memory CD8⁺ T cells recognizing distinct antigens and elicited by different pathogens. Following IL-15c-induced expansion, divided cells contracted to baseline numbers and only slowly returned to basal proliferation, suggesting a mechanism to transiently amplify memory populations. Through parabiosis, we showed that IL-15c drive local proliferation of T_RM, with a degree of recruitment of circulating cells to some NLTs. Hence, irrespective of homeostatic IL-15 dependence, IL-15 sensitivity is a defining feature of memory CD8⁺ T cell populations, with therapeutic potential for expansion of T_RM and other memory subsets in an antigen-agnostic and temporally controlled fashion.

Targeting inflammation and immune activation to improve CTLA4-Ig-based modulation of transplant rejection

For the last few decades, Calcineurin inhibitors (CNI)-based therapy has been the pillar of immunosuppression for prevention of organ transplant rejection. However, despite exerting effective control of acute rejection in the first year post-transplant, prolonged CNI use is associated with significant side effects and is not well suited for long term allograft survival. The implementation of Costimulation Blockade (CoB) therapies, based on the interruption of T cell costimulatory signals as strategy to control allo-responses, has proven potential for better management of transplant recipients compared to CNI-based therapies. The use of the biologic cytotoxic T-lymphocyte associated protein 4 (CTLA4)-Ig is the most successful approach to date in this arena. Following evaluation of the BENEFIT trials, Belatacept, a high-affinity version of CTLA4-Ig, has been FDA approved for use in kidney transplant recipients. Despite its benefits, the use of CTLA4-Ig as a monotherapy has proved to be insufficient to induce long-term allograft acceptance in several settings. Multiple studies have demonstrated that events that induce an acute inflammatory response with the consequent release of proinflammatory cytokines, and an abundance of allograft-reactive memory cells in the recipient, can prevent the induction of or break established immunomodulation induced with CoB regimens. This review highlights advances in our understanding of the factors and mechanisms that limit CoB regimens efficacy. We also discuss recent successes in experimentally designing complementary therapies that favor CTLA4-Ig effect, affording a better control of transplant rejection and supporting their clinical applicability.

Molecular characterization and expression analysis of interleukin-15 (IL-15) genes in orange-spotted grouper (Epinephelus coioides) in response to Vibrio harveyi challenge

As a member of the γc family, interleukin 15 plays an important function in the immune response. In this study, we cloned an IL15 from Epinephelus coioides (named Ec-IL15). The open reading frame of Ec-IL15 is 528 bp, encoding 175 amino acids. Sequence alignment analysis showed that EcIL-15 has a conserved Pfam: IL15 domain and four cysteine residues. Subcellular localization studies have shown that Ec-IL15 is distributed in whole cells. In healthy groupers, Ec-IL15 was expressed in all 11 tissues tested and the highest in liver. After ConA, PHA, LPS and poly I:C stimulation, Ec-IL15 expression of HKLs was significantly upregulated. After V. harveyi infection, the expression of Ec-IL15 in 9 tissues was significantly upregulated and peaked within 48 h. In addition, recombinant Ec-IL15 protein can not only stimulate HKLs proliferation and cytokine expression, but also has the potential as an immune enhancer.

Effect of cellular aging on memory T-cell homeostasis

The fact that T-cell numbers remain relatively stable throughout life, and that T-cell proliferation rates increase during lymphopenia, has led to the consensus that T-cell numbers are regulated in a density-dependent manner. Competition for resources among memory T cells has been proposed to underlie this ‘homeostatic’ regulation. We first review how two classic models of resource competition affect the T-cell receptor (TCR) diversity of the memory T-cell pool. First, ‘global’ competition for cytokines leads to a skewed repertoire that tends to be dominated by the very first immune response. Second, additional ‘cognate’ competition for specific antigens results in a very diverse and stable memory T-cell pool, allowing every antigen to be remembered, which we therefore define as the ‘gold-standard’. Because there is limited evidence that memory T cells of the same specificity compete more strongly with each other than with memory T cells of different specificities, i.e., for ‘cognate’ competition, we investigate whether cellular aging could account for a similar level of TCR diversity. We define cellular aging as a declining cellular fitness due to reduced proliferation. We find that the gradual erosion of previous T-cell memories due to cellular aging allows for better establishment of novel memories and for a much higher level of TCR diversity compared to global competition. A small continual source (either from stem-cell-like memory T-cells or from naive T-cells due to repeated antigen exposure) improves the diversity of the memory T-cell pool, but remarkably, only in the cellular aging model. We further show that the presence of a source keeps the inflation of chronic memory responses in check by maintaining the immune memories to non-chronic antigens. We conclude that cellular aging along with a small source provides a novel and immunologically realistic mechanism to achieve and maintain the ‘gold-standard’ level of TCR diversity in the memory T-cell pool.

Lymphopenia and Mechanisms of T-Cell Regeneration

Chronic lymphopenia, in particular, T-lymphocyte deficiency, increases the risk of death from cancer, cardiovascular and respiratory diseases and serves as a risk factor for a severe course and poor outcome of infectious diseases such as COVID-19. The regeneration of T-lymphocytes is a complex multilevel process, many questions of which still remain unanswered. The present review considers two main pathways of increasing the T-cell number in lymphopenia: production in the thymus and homeostatic proliferation in the periphery. Literature data on the signals that regulate each pathway are summarized. Their contribution to the quantitative and qualitative restoration of the immune cell pool is analyzed. The features of CD4⁺ and CD8⁺ T-lymphocytes’ regeneration are considered.

Adoptive tumor infiltrating lymphocyte transfer as personalized immunotherapy

Cancer is a leading cause of death worldwide and, despite new targeted therapies and immunotherapies, a large group of patients fail to respond to therapy or progress after initial response, which brings the need for additional treatment options. Manipulating the immune system using a variety of approaches has been explored for the past years with successful results. Sustained progress has been made to understand the T cell-mediated anti-tumor responses counteracting the tumorigenesis process. The T-lymphocyte pool, especially its capacity for antigen-directed cytotoxicity, has become a central focus for engaging the immune system in defeating cancer. The adoptive cell transfer of autologous tumor-infiltrating lymphocytes has been used in humans for over 30 years to treat metastatic melanoma. In this review, we provide a brief history of ACT-TIL and discuss the current state of ACT-TIL clinical development in solid tumors. We also discuss how key advances in understanding genetic intratumor heterogeneity, to accurately identify neoantigens, and new strategies designed to overcome T-cell exhaustion and tumor immunosuppression have improved the efficacy of the TIL-therapy infusion. Characteristics of the TIL products will be discussed, as well as new strategies, including the selective expansion of specific fractions from the cell product or the genetic manipulation of T cells for improving the in-vivo survival and functionality. In summary, this review outlines the potential of ACT-TIL as a personalized approach for epithelial tumors and continued discoveries are making it increasingly more effective against other types of cancers.

Tumor-infiltrating lymphocyte therapy for lung cancer and its future paradigms

INTRODUCTION

Lung cancer is the leading cause of cancer death, with an estimated 1.8 million deaths contributing to this cancer in 2020. Despite advances in treatment options and various approaches being attempted, the survival rate remains low.

AREAS COVERED

In this review, we aim to provide an overview of the efficacy of tumor-infiltrating lymphocyte (TIL) therapy for lung cancer based on existing clinical trials. We also discuss the current challenges and future landscape of this treatment modality.

EXPERT OPINION

Lung cancer can be a suitable candidate for TIL therapy due to its high mutational burden. Specifically, it has shown promising results for non-small cell lung cancer resistant to immune checkpoint inhibitors. Still, there are many restrictions associated with the ex vivo expansion and delivery of TILs, limiting their availability. For this reason, applying TIL for the treatment of lung cancer has not been extensively investigated yet and only a few clinical trials have shown favorable results of TIL therapy in patients with lung cancer. Thus, facilitating this costly, labor-intensive and time-consuming process is of utmost importance to increase the number of performed studies and to detect eligible patients who could benefit most from this treatment modality.

Metabolic dynamics instructs CD8 + T cell differentiation and functions

Cytotoxic CD8⁺ T cells are a key element of the adaptative immune system to protect the organism against infections and malignant cells. During their activation and response, T cells undergo different metabolic pathways to support their energetic needs according to their localization and function. However, it has also been recently appreciated that this metabolic reprogramming also directly supports T‐cell lineage differentiation. Accordingly, metabolic deficiencies and prolonged stress exposure can impact T‐cell differentiation and skew them into an exhausted state. Here, we review how metabolism defines CD8⁺ T‐cell differentiation and function. Moreover, we cover the principal metabolic dysregulation that promotes the exhausted phenotype under tumor or chronic virus conditions. Finally, we summarize recent strategies to reprogram impaired metabolic pathways to promote CD8⁺ T‐cell effector function and survival.

In vivo availability of the cytokine IL-7 constrains the survival and homeostasis of peripheral iNKT cells

Understanding the homeostatic mechanism of invariant natural killer T (iNKT) cells is a critical issue in iNKT cell biology. Because interleukin (IL)-15 is required for the thymic generation of iNKT cells, IL-15 has also been considered necessary for the homeostasis of peripheral iNKT cells. Here, we delineated the in vivo cytokine requirement for iNKT cells, and we came to the surprising conclusion that IL-7, not IL-15, is the homeostatic cytokine for iNKT cells. Employing a series of experimental mouse models where the availability of IL-7 or IL-15 was manipulated in peripheral tissues, either by genetic tools or by adult thymectomy and cytokine pump installation, we demonstrate that the abundance of IL-7, and not IL-15, limits the size of the peripheral iNKT cell pool. These results redefine the cytokine requirement for iNKT cells and indicate competition for IL-7 between iNKT and conventional αβ T cells.

Functional roles of cytokines in infectious disease associated colorectal carcinogenesis

Infection processes induce various soluble factors that are carcinogens in humans; therefore, research into the soluble factors of chronic disease released from cells that have been infected with parasites is warranted. Parasitic infections in host cells release high levels of IFNγ. Studies have hypothesised that parasitosis-associated carcinogenesis might be analogous to colorectal cancers developed from inflammatory bowel diseases, whereby various cytokines and chemokines are secreted during chronic inflammation. IL-18 and IL-21 are other factors that might be involved in the development of colorectal cancer in schistosomiasis patients and patients with other infections. IL-21 has profound effects on tumour growth and immunosurveillance of colitis-associated tumourigenesis, thereby emphasising its involvement in the pathogenesis of colorectal cancer. The prominent role of IL-21 in antitumour effects greatly depends on the enhanced cytolytic activity of NK cells and the pathogenic role of IL-21, which is often associated with enhanced risks of cancer and chronic inflammatory processes. As IL-15 is also related to chronic disease, it is believed to also play a role in the antitumour effect of colorectal carcinogenesis. IL-15 generates and maintains long-term CD8⁺ T cell immunity against T. gondii to control the infection of intracellular pathogens. The lack of IL-15 in mice contributes to the downregulation of the IFNγ-producing CD4⁺ T cell response against acute T. gondii infection. IL-15 induces hyperplasia and supports the progressive growth of colon cancer via multiple functions. The limited role of IL-15 in the development of NK and CD8⁺ T cells suggests that there may be other cytokines compensating for the loss of the IL-15 gene.

Somatic Reversion of a Novel IL2RG Mutation Resulting in Atypical X-Linked Combined Immunodeficiency

Mutations of the IL2RG gene, which encodes for the interleukin-2 receptor common gamma chain (γ_C, CD132), can lead to X-linked severe combined immunodeficiency (X-SCID) associated with a T⁻B⁺NK⁻ phenotype as a result of dysfunctional γ_C-JAK3-STAT5 signaling. Lately, hypomorphic mutations of the IL2RG gene have been described causing atypical SCID with a milder phenotype. Here, we report three brothers with low-normal lymphocyte counts and susceptibility to recurrent respiratory infections and cutaneous warts. The clinical presentation combined with dysgammaglobulinemia suspected an inherited immunity disorder, which has been proven by Next Generation Sequencing as a novel c.458T > C; p.Ile153Thr IL2RG missense-mutation. Subsequent functional characterization revealed impaired T-cell proliferation, low TREC levels and a skewed TCR Vβ repertoire in all three patients. Interestingly, investigation of various subpopulations showed normal expression of CD132 but with partially impaired STAT5 phosphorylation compared to healthy controls. Additionally, we performed precise genetic analysis of subpopulations revealing spontaneous somatic reversion, predominately in lymphoid derived CD3⁺, CD4⁺ and CD8⁺ T cells. Our data demonstrate that the atypical SCID phenotype noticed in these three brothers is due to the combination of hypomorphic IL-2RG function and somatic reversion.

Bidirectional communication between neural and immune systems

The immune and nervous systems share many features, including receptor and ligand expression, enabling efficient communication between the two. Accumulating evidence suggests that the communication is bidirectional, with the neural system regulating immune cell functions and vice versa. Steroid hormones from the hypothalamus-pituitary-adrenal gland axis are examples of systemic regulators for this communication. Neural reflexes describe regional regulation mechanisms that are a historically new concept that helps to explain how the neural and body systems including immune system communicate. Several recently identified neural reflexes, including the inflammatory reflex and gateway reflex, significantly impact the activation status of the immune system and are associated with inflammatory diseases and disorders. Either pro-inflammatory or anti-inflammatory effects can be elicited by these neural reflexes. On the other hand, the activities of immune cells during inflammation, for example the secretion of inflammatory mediators, can affect the functions of neuronal systems via neural reflexes and modulate biological outputs via specific neural pathways. In this review article, we discuss recent advances in the understanding of bidirectional neuro-immune interactions, with a particular focus on neural reflexes.

Re-Programming Autoreactive T Cells Into T-Regulatory Type 1 Cells for the Treatment of Autoimmunity

Systemic delivery of peptide-major histocompatibility complex (pMHC) class II-based nanomedicines can re-program cognate autoantigen-experienced CD4+ T cells into disease-suppressing T-regulatory type 1 (TR1)-like cells. In turn, these TR1-like cells trigger the formation of complex regulatory cell networks that can effectively suppress organ-specific autoimmunity without impairing normal immunity. In this review, we summarize our current understanding of the transcriptional, phenotypic and functional make up of TR1-like cells as described in the literature. The true identity and direct precursors of these cells remain unclear, in particular whether TR1-like cells comprise a single terminally-differentiated lymphocyte population with distinct transcriptional and epigenetic features, or a collection of phenotypically different subsets sharing key regulatory properties. We propose that detailed transcriptional and epigenetic characterization of homogeneous pools of TR1-like cells will unravel this conundrum.

Cancer immunotherapy from biology to nanomedicine

With the significant drawbacks of conventional cancer chemotherapeutics, cancer immunotherapy has demonstrated the ability to eradicate cancer cells and circumvent multidrug resistance (MDR) with fewer side effects than traditional cytotoxic therapies. Various immunotherapeutic agents have been investigated for that purpose including checkpoint inhibitors, cytokines, monoclonal antibodies and cancer vaccines. All these agents aid immune cells to recognize and engage tumor cells by acting on tumor-specific pathways, antigens or cellular targets. However, immunotherapeutics are still associated with some concerns such as off-target side effects and poor pharmacokinetics. Nanomedicine may resolve some limitations of current immunotherapeutics such as localizing delivery, controlling release and enhancing the pharmacokinetic profile. Herein, we discuss recent advances of immunotherapeutic agents with respect to their development and biological mechanisms of action, along with the advantages that nanomedicine strategies lend to immunotherapeutics by possibly improving therapeutic outcomes and minimizing side effects.

IL-15 superagonist RLI has potent immunostimulatory properties on NK cells: implications for antimetastatic treatment

Background

As the immune system is compromised in patients with cancer, therapeutic strategies to stimulate immunity appear promising, to avoid relapse and increase long-term overall survival. Interleukin-15 (IL-15) has similar properties to IL-2, but does not cause activation-induced cell death nor activation and proliferation of regulatory T cells (Treg), which makes it a serious candidate for anticancer immunotherapy. However, IL-15 has a short half-life and high doses are needed to achieve responses. Designed to enhance its activity, receptor-linker-IL-15 (RLI) (SO-C101) is a fusion molecule of human IL-15 covalently linked to the human IL-15Rα sushi+ domain currently assessed in a phase I/Ib clinical trial on patients with advanced/metastatic solid cancer.

Methods

We investigated the antimetastatic activity of RLI in a 4T1 mouse mammary carcinoma that spontaneously metastasizes and evaluated its immunomodulatory role in the metastatic lung microenvironment. We further characterized the proliferation, maturation and cytotoxic functions of natural killer (NK) cells in tumor-free mice treated with RLI. Finally, we explored the effect of RLI on human NK cells from healthy donors and patients with non-small cell lung cancer (NSCLC).

Results

RLI treatment displayed antimetastatic properties in the 4T1 mouse model. By characterizing the lung microenvironment, we observed that RLI restored the balance between NK cells and neutrophils (CD11b⁺ Ly6G^high Ly6C^low) that massively infiltrate lungs of 4T1-tumor bearing mice. In addition, the ratio between NK cells and Treg was strongly increased by RLI treatment. Further pharmacodynamic studies in tumor-free mice revealed superior proliferative and cytotoxic functions on NK cells after RLI treatment compared with IL-15 alone. Characterization of the maturation stage of NK cells demonstrated that RLI favored accumulation of CD11b⁺ CD27^high KLRG1⁺ mature NK cells. Finally, RLI demonstrated potent immunostimulatory properties on human NK cells by inducing proliferation and activation of NK cells from healthy donors and enhancing cytotoxic responses to NKp30 crosslinking in NK cells from patients with NSCLC.

Conclusions

Collectively, our work demonstrates superior activity of RLI compared with rhIL-15 in modulating and activating NK cells and provides additional evidences for a therapeutic strategy using RLI as antimetastatic molecule.

The CD8+ T Cell Noncytotoxic Antiviral Responses

The CD8+ T cell noncytotoxic antiviral response (CNAR) was discovered during studies of asymptomatic HIV-infected subjects more than 30 years ago. In contrast to CD8+ T cell cytotoxic lymphocyte (CTL) activity, CNAR suppresses HIV replication without target cell killing. This activity has characteristics of innate immunity: it acts on all retroviruses and thus is neither epitope specific nor HLA restricted. The HIV-associated CNAR does not affect other virus families. It is mediated, at least in part, by a CD8+ T cell antiviral factor (CAF) that blocks HIV transcription. A variety of assays used to measure CNAR/CAF and the effects on other retrovirus infections are described. Notably, CD8+ T cell noncytotoxic antiviral responses have now been observed with other virus families but are mediated by different cytokines. Characterizing the protein structure of CAF has been challenging despite many biologic, immunologic, and molecular studies. It represents a low-abundance protein that may be identified by future next-generation sequencing approaches. Since CNAR/CAF is a natural noncytotoxic activity, it could provide promising strategies for HIV/AIDS therapy, cure, and prevention.

Human CD8 T-stem cell memory subsets phenotypic and functional characterization are defined by expression of CD122 or CXCR3

Long-lived T-memory stem cells (T_SCM ) are key to both naturally occurring and vaccine-conferred protection against infection. These cells are characterized by the CD45RA⁺ CCR7⁺ CD95⁺ phenotype. Significant heterogeneity within the T_SCM population is recognized, but distinguishing surface markers and functional characterization of potential subsets are lacking. Human CD8 T_SCM subsets were identified in healthy subjects who had been previously exposed to CMV or Influenza (Flu) virus in flow cytometry by expression of CD122 or CXCR3, and then characterized in proliferation, multipotency, self-renewal, and intracellular cytokine production (TNF-α, IL-2, IFN-γ), together with transcriptomic profiles. The T_SCM CD122^hi -expressing subset (versus CD122^lo ) demonstrated greater proliferation, greater multipotency, and enhanced polyfunctionality with higher frequencies of triple positive (TNF-α, IL-2, IFN-γ) cytokine-producing cells upon exposure to recall antigen. The T_SCM CXCR3^lo subpopulation also had increased proliferation and polyfunctional cytokine production. Transcriptomic analysis further showed that the T_SCM CD122^hi population had increased expression of activation and homing molecules, such as Ccr6, Cxcr6, Il12rb, and Il18rap, and downregulated cell proliferation inhibitors, S100A8 and S100A9. These data reveal that the T_SCM CD122^hi phenotype is associated with increased proliferation, enhanced multipotency and polyfunctionality with an activated memory-cell like transcriptional profile, and hence, may be favored for induction by immunization and for adoptive immunotherapy.

The Roles of Immunoregulatory Networks in Severe Drug Hypersensitivity

The immunomodulatory effects of regulatory T cells (Tregs) and co-signaling receptors have gained much attention, as they help balance immunogenic and immunotolerant responses that may be disrupted in autoimmune and infectious diseases. Drug hypersensitivity has a myriad of manifestations, which ranges from the mild maculopapular exanthema to the severe Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug reaction with eosinophilia and systemic symptoms/drug-induced hypersensitivity syndrome (DRESS/DIHS). While studies have identified high-risk human leukocyte antigen (HLA) allotypes, the presence of the HLA allotype at risk is not sufficient to elicit drug hypersensitivity. Recent studies have suggested that insufficient regulation by Tregs may play a role in severe hypersensitivity reactions. Furthermore, immune checkpoint inhibitors, such as anti-CTLA-4 or anti-PD-1, in cancer treatment also induce hypersensitivity reactions including SJS/TEN and DRESS/DIHS. Taken together, mechanisms involving both Tregs as well as coinhibitory and costimulatory receptors may be crucial in the pathogenesis of drug hypersensitivity. In this review, we summarize the currently implicated roles of co-signaling receptors and Tregs in delayed-type drug hypersensitivity in the hope of identifying potential pharmacologic targets.

Regulatory T Cells: Concept, Classification, Phenotype, and Biological Characteristics

Regulatory T cells (Treg) play an indispensable role in maintaining the body's immune nonresponse to self-antigens and suppressing the body's unwarranted and potentially harmful immune responses. Their absence, reduction, dysfunction, transformation, and instability can lead to numerous autoimmune diseases. There are several distinct subtypes of the Treg cells, although they share certain biological characteristics and have unique phenotypes with different regulatory functions, as well as mechanistic abilities. In this book chapter, we introduce the latest advances in Treg cell subtypes pertaining to classification, phenotype, biological characteristics, and mechanisms. We also highlight the relationship between Treg cells and various diseases, including autoimmune, infectious, as well as tumors and organ transplants.

Biological effects of IL-15 on immune cells and its potential for the treatment of cancer

Interleukin-15 (IL-15) has recently emerged as a novel immunomodulatory cytokine in cancer immunotherapy. IL-15 has the potential to reject and destroy cancer cells in the tumor microenvironment by expanding and activating natural killer (NK), natural killer T (NKT), and memory (m) CD8+T cells. Due to the feasible outcomes obtained from preclinical studies and phase 1/2 clinical trials, IL-15-based therapy, including chimeric antigen receptor (CAR) T cell or CAR NK cell infusion following in vitro expansion in the presence of IL-15, used in combination with checkpoint inhibitors and other therapy may extend to clinical practice in the future. It is also important to understand the biological characteristics of IL-15 to ensure the maximal benefit of therapeutic strategies. Here, we summarize the current development of IL-15 in the following areas: anti-tumor mechanisms in the tumor microenvironment, advances in IL-15-based therapy itself or in combination with other methods, including biological agents, monoclonal antibodies, and adoptive immunotherapy.

Therapy of Established Tumors with Rationally Designed Multiple Agents Targeting Diverse Immune-Tumor Interactions: Engage, Expand, Enable

Immunotherapy of immunologically cold solid tumors may require multiple agents to engage immune effector cells, expand effector populations and activities, and enable immune responses in the tumor microenvironment (TME). To target these distinct phenomena, we strategically chose five clinical-stage immuno-oncology agents, namely, (i) a tumor antigen-targeting adenovirus-based vaccine (Ad-CEA) and an IL15 superagonist (N-803) to activate tumor-specific T cells, (ii) OX40 and GITR agonists to expand and enhance the activated effector populations, and (iii) an IDO inhibitor (IDOi) to enable effector-cell activity in the TME. Flow cytometry, T-cell receptor (TCR) sequencing, and RNA-sequencing (RNA-seq) analyses showed that in the CEA-transgenic murine colon carcinoma (MC38-CEA) tumor model, Ad-CEA + N-803 combination therapy resulted in immune-mediated antitumor effects and promoted the expression of costimulatory molecules on immune subsets, OX40 and GITR, and the inhibitory molecule IDO. Treatment with Ad-CEA + N-803 + OX40 + GITR + IDOi, termed the pentatherapy regimen, resulted in the greatest inhibition of tumor growth and protection from tumor rechallenge without toxicity. Monotherapy with any of the agents had little to no antitumor activity, whereas combining two, three, or four agents had minimal antitumor effects. Immune analyses demonstrated that the pentatherapy combination induced CD4⁺ and CD8⁺ T-cell activity in the periphery and tumor, and antitumor activity associated with decreased regulatory T-cell (Treg) immunosuppression in the TME. The pentatherapy combination also inhibited tumor growth and metastatic formation in 4T1 and LL2-CEA murine tumor models. This study provides the rationale for the combination of multimodal immunotherapy agents to engage, enhance, and enable adaptive antitumor immunity.

Fusion Cytokines IL-7-Linker-IL-15 Promote Mycobacterium Tuberculosis Subunit Vaccine to Induce Central Memory like T Cell-Mediated Immunity

Tuberculosis (TB), caused by Mycobacterium tuberculosis (M. tuberculosis), is among the most serious infectious diseases worldwide. Adjuvanted protein subunit vaccines have been demonstrated as a kind of promising novel vaccine. This study proposed to investigate whether cytokines interliukine-7 (IL-7) and interliukine-15 (IL-15) help TB subunit vaccines induce long-term cell-mediated immune responses, which are required for vaccination against TB. In this study, mice were immunized with the M. tuberculosis protein subunit vaccines combined with adnovirus-mediated cytokines IL-7, IL-15, IL-7-IL-15, and IL-7-Linker-IL-15 at 0, 2, and 4 weeks, respectively. Twenty weeks after the last immunization, the long-term immune responses, especially the central memory-like T cells (T_CM like cell)-mediated immune responses, were determined with the methods of cultured IFN-γ-ELISPOT, expanded secondary immune responses, cell proliferation, and protective efficacy against Mycobacterium bovis Bacilli Calmette-Guerin (BCG) challenge, etc. The results showed that the group of vaccine + rAd-IL-7-Linker-IL-15 induced a stronger long-term antigen-specific T_CM like cells-mediated immune responses and had higher protective efficacy against BCG challenge than the vaccine + rAd-vector control group, the vaccine + rAd-IL-7 and the vaccine + rAd-IL-15 groups. This study indicated that rAd-IL-7-Linker-IL-15 improved the TB subunit vaccine’s efficacy by augmenting T_CM like cells and provided long-term protective efficacy against Mycobacteria.

To Remember or to Forget: The Role of Good and Bad Memories in Adoptive T Cell Therapy for Tumors

The generation of immunological memory is a hallmark of adaptive immunity by which the immune system "remembers" a previous encounter with an antigen expressed by pathogens, tumors, or normal tissues; and, upon secondary encounters, mounts faster and more effective recall responses. The establishment of T cell memory is influenced by both cell-intrinsic and cell-extrinsic factors, including genetic, epigenetic and environmental triggers. Our current knowledge of the mechanisms involved in memory T cell differentiation has instructed new opportunities to engineer T cells with enhanced anti-tumor activity. The development of adoptive T cell therapy has emerged as a powerful approach to cure a subset of patients with advanced cancers. Efficacy of this approach often requires long-term persistence of transferred T cell products, which can vary according to their origin and manufacturing conditions. Host preconditioning and post-transfer supporting strategies have shown to promote their engraftment and survival by limiting the competition with a hostile tumor microenvironment and between pre-existing immune cell subsets. Although in the general view pre-existing memory can confer a selective advantage to adoptive T cell therapy, here we propose that also "bad memories"-in the form of antigen-experienced T cell subsets-co-evolve with consequences on newly transferred lymphocytes. In this review, we will first provide an overview of selected features of memory T cell subsets and, then, discuss their putative implications for adoptive T cell therapy.

Podoplanin as an Attractive Target of CAR T Cell Therapy

To date, various kinds of cancer immunotherapy methods have been developed, but T cell immunotherapy is one of the most promising strategies. In general, T cell receptor (TCR) or chimeric antigen receptor (CAR) is used to modify the antigen specificity of T cells. CARs possess an underlying potential with treatment efficacy to treat a broad range of cancer patients compared with TCRs. Although a variety of CAR molecules have been developed so far, the clinical application for solid tumors is limited partly due to its adverse effect known as “on-target off-tumor toxicity”. Therefore, it is very important for CAR T cell therapy to target specific antigens exclusively expressed by malignant cells. Here, we review the application of T cell immunotherapy using specific antigen receptor molecules and discuss the possibility of the clinical application of podoplanin-targeted CAR derived from a cancer-specific monoclonal antibody (CasMab).

Coexpression of IL7 and CCL21 Increases Efficacy of CAR-T Cells in Solid Tumors without Requiring Preconditioned Lymphodepletion

PURPOSE

T-cell recruitment, survival, and proliferation are the important limitations to chimeric antigen receptor (CAR) T cells therapy in the treatment of solid tumors. In this study, we engineered CAR-T cells to coexpress cytokines IL7 and CCL21 (7 × 21 CAR-T), a cytokine combination in order to improve proliferation and chemotaxis of CAR-T cells.

EXPERIMENTAL DESIGN

CLDN18.2-specific second-generation CAR-T cells coexpressing cytokines were prepared using retroviral vector transduction. The proliferation and migration of genetically engineered CAR-T cells were evaluated in vitro. The antitumor activities of genetically engineered CAR-T cells were evaluated against multiple solid tumors in C57BL/6 mice in vivo.

RESULTS

In vitro, the proliferation and chemotaxis of 7 × 21 CAR-T cells are significantly improved when compared with those of the conventional CAR-T cells. In vivo, 7 × 21 CAR-T cells revealed superior therapeutic effects to either conventional CAR-T cells or 7 × 19 CAR-T cells which coexpress IL7 and CCL19 as previously reported in three different solid tumors without cyclophosphamide precondition. Interestingly, 7 × 21 CAR-T cells could also suppress the tumor growth with heterogeneous antigen expression and even induce tumor complete remission. Mechanistically, IL7 and CCL21 significantly improved survival and infiltration of CAR-T cells and dendritic cells in tumor. In addition, CCL21 also inhibited the tumor angiogenesis as proved by IHC.

CONCLUSIONS

Coexpression of IL7 and CCL21 could boost CAR-T cells' antitumor activity, and 7 × 21 CAR-T cells may be served as a promising therapy strategy for solid tumors.

Treatment of mice with S4B6 IL-2 complex prevents lethal toxoplasmosis via IL-12- and IL-18-dependent interferon-gamma production by non-CD4 immune cells

Toxoplasmic encephalitis is an AIDS-defining condition. The decline of IFN-γ-producing CD4⁺ T cells in AIDS is a major contributing factor in reactivation of quiescent Toxoplasma gondii to an actively replicating stage of infection. Hence, it is important to characterize CD4-independent mechanisms that constrain acute T. gondii infection. We investigated the in vivo regulation of IFN-γ production by CD8⁺ T cells, DN T cells and NK cells in response to acute T. gondii infection. Our data show that processing of IFN-γ by these non-CD4 cells is dependent on both IL-12 and IL-18 and the secretion of bioactive IL-18 in response to T. gondii requires the sensing of viable parasites by multiple redundant inflammasome sensors in multiple hematopoietic cell types. Importantly, our results show that expansion of CD8⁺ T cells, DN T cells and NK cell by S4B6 IL-2 complex pre-treatment increases survival rates of mice infected with T. gondii and this is dependent on IL-12, IL-18 and IFN-γ. Increased survival is accompanied by reduced pathology but is independent of expansion of T_Reg cells or parasite burden. This provides evidence for a protective role of IL2C-mediated expansion of non-CD4 cells and may represent a promising lead to adjunct therapy for acute toxoplasmosis.

The Roles of CCR7 for the Homing of Memory CD8+ T Cells into Their Survival Niches

Memory CD8+ T cells in the immune system are responsible for the removal of external Ags for a long period of time to protect against re-infection. Naïve to memory CD8+ T cell differentiation and memory CD8+ T cell maintenance require many different factors including local environmental factors. Thus, it has been suggested that the migration of memory CD8+ T cells into specific microenvironments alters their longevity and functions. In this review, we have summarized the subsets of memory CD8+ T cells based on their migratory capacities and described the niche hypothesis for their survival. In addition, the basic roles of CCR7 in conjunction with the migration of memory CD8+ T cells and recent understandings of their survival niches have been introduced. Finally, the applications of altering CCR7 signaling have been discussed.