Control of memory CD8+ T cell longevity and effector functions by IL-15

IFN-α/β/IFN-γ/IL-15 pathways identify GBP1-expressing tumors with an immune-responsive phenotype

Immunotherapy is widely used in cancer treatment; however, only a subset of patients responds well to it. Significant efforts have been made to identify patients who will benefit from immunotherapy. Successful anti-tumor immunity depends on an intact cancer-immunity cycle, especially long-lasting CD8+ T-cell responses. Interferon (IFN)-α/β/IFN-γ/interleukin (IL)-15 pathways have been reported to be involved in the development of CD8+ T cells. And these pathways may predict responses to immunotherapy. Herein, we aimed to analyze multiple public databases to investigate whether IFN-α/β/IFN-γ/IL-15 pathways could be used to predict the response to immunotherapy. Results showed that IFN-α/β/IFN-γ/IL-15 pathways could efficiently predict immunotherapy response, and guanylate-binding protein 1 (GBP1) could represent the IFN-α/β/IFN-γ/IL-15 pathways. In public and private cohorts, we further demonstrated that GBP1 could efficiently predict the response to immunotherapy. Functionally, GBP1 was mainly expressed in macrophages and strongly correlated with chemokines involved in T-cell migration. Therefore, our study comprehensively investigated the potential role of GBP1 in immunotherapy, which could serve as a novel biomarker for immunotherapy and a target for drug development.

Characterization of tumoricidal activities mediated by a novel immune cell regimen composing interferon-producing killer dendritic cells and tumor-specific cytotoxic T lymphocytes

BACKGROUND

Although immune cell therapy has long been used for treating solid cancer, its efficacy remains limited. Interferon (IFN)-producing killer dendritic cells (IKDCs) exhibit cytotoxicity and present antigens to relevant cells; thus, they can selectively induce tumor-associated antigen (TAA)-specific CD8 T cells and may be useful in cancer treatment. Various protocols have been used to amplify human IKDCs from peripheral sources, but the complexity of the process has prevented their widespread clinical application. Additionally, the induction of TAA-specific CD8 T cells through the adoptive transfer of IKDCs to immunocompromised patients with cancer may be insufficient. Therefore, we developed a method for generating an immune cell-based regimen, Phyduxon-T, comprising a human IKDC counterpart (Phyduxon) and expanded TAA-specific CD8 T cells.

METHODS

Peripheral blood mononuclear cells from ovarian cancer patients were cultured with human interleukin (hIL)-15, hIL-12, and hIL-18 to generate Phyduxon-T. Then, its phenotype, cytotoxicity, and antigen-presenting function were evaluated through flow cytometry using specific monoclonal antibodies.

RESULTS

Phyduxon exhibited the characteristics of both natural killer and dendritic cells. This regimen also exhibited cytotoxicity against primary ovarian cancer cells and presented TAAs, thereby inducing TAA-specific CD8 T cells, as evidenced by the expression of 4-1BB and IFN-γ. Notably, the Phyduxon-T manufacturing protocol effectively expanded IFN-γ-producing 4-1BB+ TAA-specific CD8 T cells from peripheral sources; these cells exhibited cytotoxic activities against ovarian cancer cells.

CONCLUSIONS

Phyduxon-T, which is a combination of natural killer cells, dendritic cells, and TAA-specific CD8 T cells, may enhance the efficacy of cancer immunotherapy.

Memory T cells: promising biomarkers for evaluating protection and vaccine efficacy against leishmaniasis

Understanding the immune response to Leishmania infection and identifying biomarkers that correlate with protection are crucial for developing effective vaccines. One intriguing aspect of Leishmania infection is the persistence of parasites, even after apparent lesion healing. Various host cells, including dendritic cells, fibroblasts, and Langerhans cells, may serve as safe sites for latent infection. Memory T cells, especially tissue-resident memory T cells (TRM), play a crucial role in concomitant immunity against cutaneous Leishmania infections. These TRM cells are long-lasting and can protect against reinfection in the absence of persistent parasites. CD4+ TRM cells, in particular, have been implicated in protection against Leishmania infections. These cells are characterized by their ability to reside in the skin and rapidly respond to secondary infections by producing cytokines such as IFN-γ, which activates macrophages to kill parasites. The induction of CD4+ TRM cells has shown promise in experimental immunization, leading to protection against Leishmania challenge infections. Identifying biomarkers of protection is a critical step in vaccine development and CD4+ TRM cells hold potential as biomarkers, as their presence and functions may correlate with protection. While recent studies have shown that Leishmania-specific memory CD4+ T-cell subsets are present in individuals with a history of cutaneous leishmaniasis, further studies are needed to characterize CD4+ TRM cell populations. Overall, this review highlights the importance of memory T cells, particularly skin-resident CD4+ TRM cells, as promising targets for developing effective vaccines against leishmaniasis and as biomarkers of immune protection to assess the efficacy of candidate vaccines against human leishmaniasis.

Signalling mechanisms driving homeostatic and inflammatory effects of interleukin-15 on tissue lymphocytes

There is an intriguing dichotomy in the function of cytokine interleukin-15-at low levels, it is required for the homeostasis of the immune system, yet when it is upregulated in response to pathogenic infections or in autoimmunity, IL-15 drives inflammation. IL-15 associates with the IL-15Rα within both myeloid and non-haematopoietic cells, where IL-15Rα trans-presents IL-15 in a membrane-bound form to neighboring cells. Alongside homeostatic maintenance of select lymphocyte populations such as NK cells and tissue-resident T cells, when upregulated, IL-15 also promotes inflammatory outcomes by driving effector function and cytotoxicity in NK cells and T cells. As chronic over-expression of IL-15 can lead to autoimmunity, IL-15 expression is tightly regulated. Thus, blocking dysregulated IL-15 and its downstream signalling pathways are avenues for immunotherapy. In this review we discuss the molecular pathways involved in IL-15 signalling and how these pathways contribute to both homeostatic and inflammatory functions in IL-15-dependent mature lymphoid populations, focusing on innate, and innate-like lymphocytes in tissues.

IL-15 boosts activated HBV core-specific CD8+ progenitor cells via metabolic rebalancing in persistent HBV infection

A rebalance between energy supply and demand in HBV-specific-CD8+ activated progenitor (AP) cells could restore the functionality of proliferative progeny (PP) in e-antigen(Ag)-negative chronic hepatitis B (CHBe(-)). We observed that quiescent progenitor (QP [TCF1+/FSClow]) HBVcore-specific-CD8+ cells displayed a memory-like phenotype. Following Ag-encounter, the generated AP [TCF1+/FSChigh] subset maintained the PD1+/CD127+ phenotype and gave rise to proliferative progeny (PP [ TCF1-/FSChigh]). In AP cells, IL-15 compared to IL2 decreased the initial mTORC1 boost, but maintained its activation longer linked to a catabolic profile that correlated with enhanced PP effector abilities. In nucleos(t)ide analogue (NUC)-treated CHBe(-), AP subset showed an anabolic phenotype associated with a dysfunctional PP pool. In CHBe(-) cases with low probability of HBVcore-specific-CD8+ cell on-NUC-treatment restoration, according to a clinical predictive model, IL-15/anti-PD-L1 treatment re-established their reactivity. Therefore, IL-15 could improve AP pool energy balance by decreasing intensity but extending T cell activation and by inducing a more catabolic metabolism.

Antigen-presenting B cells promote TCF-1+ PD1- stem-like CD8+ T-cell proliferation in glioblastoma

Understanding the spatial relationship and functional interaction of immune cells in glioblastoma (GBM) is critical for developing new therapeutics that overcome the highly immunosuppressive tumor microenvironment. Our study showed that B and T cells form clusters within the GBM microenvironment within a 15-μm radius, suggesting that B and T cells could form immune synapses within the GBM. However, GBM-infiltrating B cells suppress the activation of CD8+ T cells. To overcome this immunosuppression, we leveraged B-cell functions by activating them with CD40 agonism, IFNγ, and BAFF to generate a potent antigen-presenting B cells named BVax. BVax had improved antigen cross-presentation potential compared to naïve B cells and were primed to use the IL15-IL15Ra mechanism to enhance T cell activation. Compared to naïve B cells, BVax could improve CD8 T cell activation and proliferation. Compared to dendritic cells (DCs), which are the current gold standard professional antigen-presenting cell, BVax promoted highly proliferative T cells in-vitro that had a stem-like memory T cell phenotype characterized by CD62L+CD44- expression, high TCF-1 expression, and low PD-1 and granzyme B expression. Adoptive transfer of BVax-activated CD8+ T cells into tumor-bearing brains led to T cell reactivation with higher TCF-1 expression and elevated granzyme B production compared to DC-activated CD8+ T cells. Adoptive transfer of BVax into an irradiated immunocompetent tumor-bearing host promoted more CD8+ T cell proliferation than adoptive transfer of DCs. Moreover, highly proliferative CD8+ T cells in the BVax group had less PD-1 expression than those highly proliferative CD8+ T cells in the DC group. The findings of this study suggest that BVax and DC could generate distinctive CD8+ T cells, which potentially serve multiple purposes in cellular vaccine development.

Cytotoxic CD4 development requires CD4 effectors to concurrently recognize local antigen and encounter type I IFN-induced IL-15

Cytotoxic CD4 T cell effectors (ThCTLs) kill virus-infected major histocompatibility complex (MHC) class II+ cells, contributing to viral clearance. We identify key factors by which influenza A virus infection drives non-cytotoxic CD4 effectors to differentiate into lung tissue-resident ThCTL effectors. We find that CD4 effectors must again recognize cognate antigen on antigen-presenting cells (APCs) within the lungs. Both dendritic cells and B cells are sufficient as APCs, but CD28 co-stimulation is not needed. Optimal generation of ThCTLs requires signals induced by the ongoing infection independent of antigen presentation. Infection-elicited type I interferon (IFN) induces interleukin-15 (IL-15), which, in turn, supports CD4 effector differentiation into ThCTLs. We suggest that these multiple spatial, temporal, and cellular requirements prevent excessive lung ThCTL responses when virus is already cleared but ensure their development when infection persists. This supports a model where continuing infection drives the development of multiple, more differentiated subsets of CD4 effectors by distinct pathways.

Single cell and spatial sequencing define processes by which keratinocytes and fibroblasts amplify inflammatory responses in psoriasis

The immunopathogenesis of psoriasis, a common chronic inflammatory disease of the skin, is incompletely understood. Here we demonstrate, using a combination of single cell and spatial RNA sequencing, IL-36 dependent amplification of IL-17A and TNF inflammatory responses in the absence of neutrophil proteases, which primarily occur within the supraspinous layer of the psoriatic epidermis. We further show that a subset of SFRP2+ fibroblasts in psoriasis contribute to amplification of the immune network through transition to a pro-inflammatory state. The SFRP2+ fibroblast communication network involves production of CCL13, CCL19 and CXCL12, connected by ligand-receptor interactions to other spatially proximate cell types: CCR2+ myeloid cells, CCR7+ LAMP3+ dendritic cells, and CXCR4 expressed on both CD8+ Tc17 cells and keratinocytes, respectively. The SFRP2+ fibroblasts also express cathepsin S, further amplifying inflammatory responses by activating IL-36G in keratinocytes. These data provide an in-depth view of psoriasis pathogenesis, which expands our understanding of the critical cellular participants to include inflammatory fibroblasts and their cellular interactions.

Research progress of interleukin-15 in cancer immunotherapy

Interleukin-15 (IL-15) is a cytokine that belongs to the interleukin-2 (IL-2) family and is essential for the development, proliferation, and activation of immune cells, including natural killer (NK) cells, T cells and B cells. Recent studies have revealed that interleukin-15 also plays a critical role in cancer immunotherapy. Interleukin-15 agonist molecules have shown that interleukin-15 agonists are effective in inhibiting tumor growth and preventing metastasis, and some are undergoing clinical trials. In this review, we will summarize the recent progress in interleukin-15 research over the past 5 years, highlighting its potential applications in cancer immunotherapy and the progress of interleukin-15 agonist development.

The case for the therapeutic use of mechanistic/mammalian target of rapamycin (mTOR) inhibitors in xenotransplantation

The mechanistic/mammalian target of rapamycin (mTOR) is one of the systems that are necessary to maintain cell homeostasis, such as survival, proliferation, and differentiation. mTOR inhibitors (mTOR-Is) are utilized as immunosuppressants and anti-cancer drugs. In organ allotransplantation, current regimens infrequently include an mTOR-I, which are positioned more commonly as alternative immunosuppressants. In clinical allotransplantation, long-term efficacy has been established, but there is a significant incidence of adverse events, for example, inhibition of wound healing, buccal ulceration, anemia, hyperglycemia, dyslipidemia, and thrombocytopenia, some of which are dose-dependent. mTOR-Is have properties that may be especially beneficial in xenotransplantation. These include suppression of T cell proliferation, increases in the number of T regulatory cells, inhibition of pig graft growth, and anti-inflammatory, anti-viral, and anti-cancer effects. We here review the potential benefits and risks of mTOR-Is in xenotransplantation and suggest that the benefits exceed the adverse effects.

TCR-signals downstream adversely correlate with the survival signals of memory CD8+ T cells under homeostasis

The significance of self-peptide-MHC-I/TCR (SMT) interaction in the survival of CD8⁺ T cells during naïve- and developmental-stages is well documented. However, the same for the memory stage is contentious. Previous studies have attempted to address the issue using MHC-I or TCR deficient systems, but inconsistent findings with memory CD8⁺ T cells of different TCR specificities have complicated the interpretation. Differential presence and/or processing of TCR-signals downstream in memory CD8⁺ T cells of different TCR specificities could be thought of as a reason. In this study, we examined the TCR-signals downstream in memory CD8⁺ T cells and compared them to the presence of survival-related signals (Annexin-V, Bcl-2, and Ki-67). We categorically tracked foreign antigen-experienced memory CD8⁺ T (TM) cells generated after Plasmodium pre-erythrocytic-stage malaria infection in C57BL/6 mice. Interestingly, we found that memory CD8⁺ T cells had more TCR-signals downstream than naive cells. We reasoned and attributed the increased expression of cell adhesion molecules to the enhanced TCR-signaling. TCR-signals downstream correlate more closely with survival signals in naive CD8⁺ T cells than with death signals in TM cells. Further investigation using antigen-specific CD8⁺ T cells and diverse infection systems would aid in conceptualizing the findings.

Manipulation of metabolic pathways to promote stem-like and memory T cell phenotypes for immunotherapy

Utilizing the immune system's capacity to recognize and kill tumor cells has revolutionized cancer therapy in recent decades. Phenotypic study of antitumor T cells supports the principle that superior tumor control is achieved by cells with more long-lived memory or stem-like properties as compared to terminally differentiated effector cells. In this Mini-Review, we explore recent advances in profiling the different metabolic programs that both generate and define subsets of memory T cells. We additionally discuss new experimental approaches that aim to maximize the durability and sustained antitumor response associated with memory T cells within the unique immunosuppressive conditions of the tumor microenvironment, such as engineered attempts to overcome hypoxia-induced changes in mitochondrial function, the inhibitory effects of tumor metabolites, and exploitation of more recently-defined metabolic pathways controlling T cell memory fate such as glycogen metabolism.

IL-21, Inflammatory Cytokines and Hyperpolarized CD8+ T Cells Are Central Players in Lupus Immune Pathology

Systemic lupus erythematous (SLE) is a chronic autoimmune disorder, broadly characterized by systemic inflammation along with heterogeneous clinical manifestations, severe morbidity, moribund organ failure and eventual mortality. In our study, SLE patients displayed a higher percentage of activated, inflamed and hyper-polarized CD8⁺ T cells, dysregulated CD8⁺ T cell differentiation, significantly elevated serum inflammatory cytokines and higher accumulation of cellular ROS when compared to healthy controls. Importantly, these hyper-inflammatory/hyper-polarized CD8⁺ T cells responded better to an antioxidant than to an oxidant. Terminally differentiated Tc1 cells also showed plasticity upon oxidant/antioxidant treatment, but that was in contrast to the SLE CD8⁺ T cell response. Our studies suggest that the differential phenotype and redox response of SLE CD8⁺ T cells and Tc1 cells could be attributed to their cytokine environs during their respective differentiation and eventual activation environs. The polarization of Tc1 cells with IL-21 drove hyper-cytotoxicity without hyper-polarisation suggesting that the SLE inflammatory cytokine environment could drive the extreme aberrancy in SLE CD8⁺ T cells.

Regulation of CD8 T cell by B-cells: A narrative review

Activation of CD4 T cells by B cells has been extensively studied, but B cell-regulated priming, proliferation, and survival of CD8 T cells remains controversial. B cells express high levels of MHC class I molecules and can potentially act as antigen-presenting cells (APCs) for CD8 T cells. Several in vivo studies in mice and humans demonstrate the role of B cells as modulators of CD8 T cell function in the context of viral infections, autoimmune diseases, cancer and allograft rejection. In addition, B-cell depletion therapies can lead to impaired CD8 T-cell responses. In this review, we attempt to answer 2 important questions: 1. the role of B cell antigen presentation and cytokine production in the regulation of CD8 T cell survival and cell fate determination, and 2. The role of B cells in the formation and maintenance of CD8 T cell memory.

Analysis of causes for poor persistence of CAR-T cell therapy in vivo

Chimeric antigen receptor T-cell (CAR-T-cell) therapy has been well researched to date because of its ability to target malignant tumor cells. The most common CAR-T cells are CD19 CAR-T cells, which play a large role in B-cell leukemia treatment. However, most CAR-T cells are associated with relapse after clinical treatment, so the quality and persistence of CAR-T cells need to be improved. With continuous optimization, there have been four generations of CARs and each generation of CARs has better quality and durability than the previous generation. In addition, it is important to increase the proportion of memory cells in CAR-T cells. Studies have shown that an immunosuppressive tumor microenvironment (TME) can lead to dysfunction of CAR-T cells, resulting in decreased cell proliferation and poor persistence. Thus, overcoming the challenges of immunosuppressive molecules and targeting cytokines in the TME can also improve CAR-T cell persistence. In this paper, we explored how to improve the durability of CAR-T cell therapy by improving the structure of CARs, increasing the proportion of memory CAR-T cells and improving the TME.

Soluble factors from TLR4- or TCR-activated cells contribute to stability of the resting phenotype and increase the expression of CXCR4 of human memory CD4 T cells

It has been proposed that cytokines can induce activation of resting T cells in an antigen-independent manner. However, experimental conditions have included the use of fetal serum and nanogram concentrations of added cytokines. To evaluate the effect of cytokines and chemokines generated by activated immune cells on the phenotypic profile of human memory CD4 T cells, the cells were cultured in FBS-free conditions in the presence of IL-15 and 5% of hAB serum and incubated with conditioned medium (CM) obtained from PBMC activated through the TCR using anti-CD3/CD28/CD2 antibodies (TCR-CM) or through TLR4 using bacterial LPS (TLR4-CM). Cytokines and chemokines present in the CMs were evaluated by ProcartaPlex immunoassay. Cell viability, proliferation, and surface markers were determined by flow cytometry on day 2, 5, and 8 of culture. Cell viability was maintained by TLR4-CM plus IL-15 for 8 days but decreased in the presence of the TCR-CM plus IL-15. In combination with IL-15, the TLR4-CM, but not the TCR-CM, maintained the expression of CD3 and CD4 stable. Both conditions stabilized the expression of CD45RO and CCR5. Thus, the TLR4-CM better supported the viability and stability of the memory phenotype. None of the CMs induced proliferation or expression of activation markers; however, they induced an increased expression of CXCR4. This study indicates that resting memory CD4 T cells are not activated by, but may be sensitive to soluble factors produced by antigen or PAMP-stimulated cells, which may contribute to their homeostasis and favor the CXCR4 expression.

IL-15 induced bystander activation of CD8+ T cells may mediate endothelium injury through NKG2D in Hantaan virus infection

Introduction

Hantaan virus (HTNV) can cause endothelium injury in hemorrhagic fever with renal syndrome (HFRS) patients. Bystander activation of CD8+ T cells by virus infection has been shown that was involved in host injury, but it is unclear during HTNV infection. This project aimed to study the effect of bystander-activated CD8+ T cell responses in HTNV infection.

Methods

The in vitro infection model was established to imitate the injury of endothelium in HFRS patients. Flow cytometry was performed to detect the expression of markers of tetramer+ CD8+ T cells and human umbilical vein endothelial cells (HUVECs). The levels of interleukin-15 (IL-15) in serum and supermanant were detected using ELISA kit. The expression of MICA of HUVECs was respectively determined by flow cytometry and western blot. The cytotoxicity of CD8+ T cells was assessed through the cytotoxicity assay and antibody blocking assay.

Results

EBV or CMV-specific CD8+ T cells were bystander activated after HTNV infection in HFRS patients. HTNV-infected HUVECs in vitro could produce high levels of IL-15, which was positively correlated with disease severity and the expression of NKG2D on bystander-activated CD8+ T cells. Moreover, the elevated IL-15 could induce activation of CD122 (IL-15Rβ)+NKG2D+ EBV/CMV-specific CD8+ T cells. The expression of IL-15Rα and ligand for NKG2D were upregulated on HTNV-infected HUVECs. Bystander-activated CD8+ T cells could exert cytotoxicity effects against HTNV-infected HUVECs, which could be enhanced by IL-15 stimulation and blocked by NKG2D antibody.

Discussion

IL-15 induced bystander activation of CD8+ T cells through NKG2D, which may mediate endothelium injury during HTNV infection in HFRS patients.

A great disturbance in the force: IL-2 receptor defects disrupt immune homeostasis

PURPOSE OF REVIEW

The current review highlights how inborn errors of immunity (IEI) due to IL-2 receptor (IL-2R) subunit defects may result in children presenting with a wide variety of infectious and inflammatory presentations beyond typical X-linked severe combined immune deficiency (X-SCID) associated with IL-2Rγ.

RECENT FINDINGS

Newborn screening has made diagnosis of typical SCID presenting with severe infections less common. Instead, infants are typically diagnosed in the first days of life when they appear healthy. Although earlier diagnosis has improved clinical outcomes for X-SCID, atypical SCID or other IEI not detected on newborn screening may present with more limited infectious presentations and/or profound immune dysregulation. Early management to prevent/control infections and reduce inflammatory complications is important for optimal outcomes of definitive therapies. Hematopoietic stem cell transplant (HSCT) is curative for IL-2Rα, IL-2Rβ, and IL-2Rγ defects, but gene therapy may yield comparable results for X-SCID.

SUMMARY

Defects in IL-2R subunits present with infectious and inflammatory phenotypes that should raise clinician's concern for IEI. Immunophenotyping may support the suspicion for diagnosis, but ultimately genetic studies will confirm the diagnosis and enable family counseling. Management of infectious and inflammatory complications will determine the success of gene therapy or HSCT.

Effector Memory-Expressing CD45RA (TEMRA) CD8+ T Cells from Kidney Transplant Recipients Exhibit Enhanced Purinergic P2X4 Receptor-Dependent Proinflammatory and Migratory Responses

BACKGROUND

The mechanisms regulating CD8+ T cell migration to nonlymphoid tissue during inflammation have not been fully elucidated, and the migratory properties of effector memory CD8+ T cells that re-express CD45RA (TEMRA CD8+ T cells) remain unclear, despite their roles in autoimmune diseases and allotransplant rejection.

METHODS

We used single-cell proteomic profiling and functional testing of CD8+ T cell subsets to characterize their effector functions and migratory properties in healthy volunteers and kidney transplant recipients with stable or humoral rejection.

RESULTS

We showed that humoral rejection of a kidney allograft is associated with an accumulation of cytolytic TEMRA CD8+ T cells in blood and kidney graft biopsies. TEMRA CD8+ T cells from kidney transplant recipients exhibited enhanced migratory properties compared with effector memory (EM) CD8+ T cells, with enhanced adhesion to activated endothelium and transmigration in response to the chemokine CXCL12. CXCL12 directly triggers a purinergic P2×4 receptor-dependent proinflammatory response of TEMRA CD8+ T cells from transplant recipients. The stimulation with IL-15 promotes the CXCL12-induced migration of TEMRA and EM CD8+ T cells and promotes the generation of functional PSGL1, which interacts with the cell adhesion molecule P-selectin and adhesion of these cells to activated endothelium. Although disruption of the interaction between functional PSGL1 and P-selectin prevents the adhesion and transmigration of both TEMRA and EM CD8+ T cells, targeting VLA-4 or LFA-1 (integrins involved in T cell migration) specifically inhibited the migration of TEMRA CD8+ T cells from kidney transplant recipients.

CONCLUSIONS

Our findings highlight the active role of TEMRA CD8+ T cells in humoral transplant rejection and suggest that kidney transplant recipients may benefit from therapeutics targeting these cells.

P2X7 purinergic receptor plays a critical role in maintaining T-cell homeostasis and preventing lupus pathogenesis

The severe lymphoproliferative and lupus diseases developed by MRL/lpr mice depend on interactions between the Fas^lpr mutation and MRL genetic background. Thus, the Fas^lpr mutation causes limited disease in C57BL/6 mice. We previously found that accumulating B220⁺ CD4^–CD8^– double negative (DN) T cells in MRL/lpr mice show defective P2X7 receptor ( P2X7)-induced cellular functions, suggesting that P2X7 contributes to T-cell homeostasis, along with Fas. Therefore, we generated a B6/lpr mouse strain (called B6/lpr-p2x7KO) carrying homozygous P2X7 knockout alleles. B6/lpr-p2x7KO mice accumulated high numbers of FasL-expressing B220⁺ DN T cells of CD45RB^highCD44^high effector/memory CD8⁺ T-cell origin and developed severe lupus, characterized by leukocyte infiltration into the tissues, high levels of IgG anti-dsDNA and rheumatoid factor autoantibodies, and marked cytokine network dysregulation. B6/lpr-p2x7KO mice also exhibited a considerably reduced lifespan. P2X7 is therefore a novel regulator of T-cell homeostasis, of which cooperation with Fas is critical to prevent lymphoaccumulation and autoimmunity.

Current Vaccine Platforms in Enhancing T-Cell Response

The induction of T cell-mediated immunity is crucial in vaccine development. The most effective vaccine is likely to employ both cellular and humoral immune responses. The efficacy of a vaccine depends on T cells activated by antigen-presenting cells. T cells also play a critical role in the duration and cross-reactivity of vaccines. Moreover, pre-existing T-cell immunity is associated with a decreased severity of infectious diseases. Many technical and delivery platforms have been designed to induce T cell-mediated vaccine immunity. The immunogenicity of vaccines is enhanced by controlling the kinetics and targeted delivery. Viral vectors are attractive tools that enable the intracellular expression of foreign antigens and induce robust immunity. However, it is necessary to select an appropriate viral vector considering the existing anti-vector immunity that impairs vaccine efficacy. mRNA vaccines have the advantage of rapid and low-cost manufacturing and have been approved for clinical use as COVID-19 vaccines for the first time. mRNA modification and nanomaterial encapsulation can help address mRNA instability and translation efficacy. This review summarizes the T cell responses of vaccines against various infectious diseases based on vaccine technologies and delivery platforms and discusses the future directions of these cutting-edge platforms.

VSIG4/CRIg directly regulates early CD8+ T cell activation through its counter-receptor in a narrow window

T-cell responses are fine-tuned by positive and negative co-signal molecules expressed on immune cells and adjacent tissues. VSIG4 is a newly identified member of the B7 family of ligands, which negatively regulates innate inflammatory and CD4⁺ T cell-mediated responses. However, little is known about the direct effects of VSIG4, which are exerted through an unidentified counter-receptor on CD8⁺ T cells. We investigated the binding of the VSIG4-Ig fusion protein during CD8⁺ T cell activation, and the functional involvement of VSIG4 pathway, using VSIG4-Ig and VSIG4-transfectants. VSIG4-Ig binding to CD8⁺ T cells was temporally observed in the CD44^high phenotype during initial activation. VSIG4-Ig binding was observed earlier than the induction of PD-1, LAG3, and TIM-3, which are immune checkpoint receptors for exhausted CD8⁺ T cells. Immobilized VSIG4-Ig inhibited anti-CD3/CD28 mAb-induced CD8⁺ T cell activation, as indicated by proliferation and IFN-γ production, similar to the downregulation of T-bet and Eomesodermin transcription factors. VSIG4 on FcγR⁺ P815 or specific antigen-presenting E.G7 cells inhibited the generation of effector CD8⁺ T cells, as indicated by proliferation, IFN-γ and TNF-α expression, and granule degradation, compared to parental cells. However, the window for the regulatory function of VSIG4 was narrow and dependent on the strength of TCR (and CD28)-mediated signals. Our results suggested that VSIG4 directly delivers co-inhibitory signals via an as-yet unidentified counter-receptor on activated CD8⁺ T cells. VSIG4-mediated CD8⁺ T cell tolerance might contribute to the steady-state maintenance of homeostasis.

Regulatory CD8+ T cells suppress disease

A subset of CD8⁺ T cells regulate chronic inflammation by killing pathogenic CD4⁺ T cells.

Protein phosphatase 2A catalytic subunit β suppresses PMA/ionomycin-induced T-cell activation by negatively regulating PI3K/Akt signaling

The precise regulation of the T-cell activation process is critical for overall immune homeostasis. Although protein phosphatase 2A (PP2A) is required for T-cell development and function, the role of PPP2CB, which is the catalytic subunit β isoform of PP2A, remains unknown. In the present study, using a T cell-specific knockout mouse of PPP2CB (PPP2CB^fl/fl Lck-Cre⁺ ), we demonstrated that PPP2CB was dispensable for T-cell development in the thymus and peripheral lymphoid organs. Furthermore, PPP2CB deletion did not affect T-cell receptor (TCR)-induced T-cell activation or cytokine-induced T-cell responses; however, it specifically enhanced phorbol myristate acetate (PMA) plus ionomycin-induced T-cell activation with increased cellular proliferation, elevated CD69 and CD25 expression, and enhanced cytokine production (inteferon-γ, interleukin-2 and tumor necrosis factor). Mechanistic analyses suggested that the PPP2CB deletion enhanced activation of the phosphoinositide 3-kinase/Akt signaling pathway and Ca²⁺ flux following stimulation with PMA plus ionomycin. Moreover, the specific PI3K inhibitor rescued the augmented cell activation in PPP2CB-deficient T cells. Using mass spectrometry-based phospho-peptide analysis, we identified potential substrates of PPP2CB during PMA plus ionomycin-induced T-cell activation. Collectively, our study provides evidence of the specific role of PPP2CB in controlling PMA plus ionomycin-induced T-cell activation.

GII.P16-GII.2 Recombinant Norovirus VLPs Polarize Macrophages Into the M1 Phenotype for Th1 Immune Responses

Norovirus (NoV) is a zoonotic virus that causes diarrhea in humans and animals. Outbreaks in nosocomial settings occur annually worldwide, endangering public health and causing serious social and economic burdens. The latter quarter of 2016 witnessed the emergence of the GII.P16-GII.2 recombinant norovirus throughout Asia. This genotype exhibits strong infectivity and replication characteristics, proposing its potential to initiate a pandemic. There is no vaccine against GII.P16-GII.2 recombinant norovirus, so it is necessary to design a preventive vaccine. In this study, GII.P16-GII.2 type norovirus virus-like particles (VLPs) were constructed using the baculovirus expression system and used to conduct immunizations in mice. After immunization of mice, mice were induced to produce memory T cells and specific antibodies, indicating that the VLPs induced specific cellular and humoral immune responses. Further experiments were then initiated to understand the underlying mechanisms involved in antigen presentation. Towards this, we established co-cultures between dendritic cells (DCs) or macrophages (Mø) and naïve CD4+T cells and simulated the antigen presentation process by incubation with VLPs. Thereafter, we detected changes in cell surface molecules, cytokines and related proteins. The results indicated that VLPs effectively promoted the phenotypic maturation of Mø but not DCs, as indicated by significant changes in the expression of MHC-II, costimulatory factors and related cytokines in Mø. Moreover, we found VLPs caused Mø to polarize to the M1 type and release inflammatory cytokines, thereby inducing naïve CD4+ T cells to perform Th1 immune responses. Therefore, this study reveals the mechanism of antigen presentation involving GII.P16-GII.2 recombinant norovirus VLPs, providing a theoretical basis for both understanding responses to norovirus infection as well as opportunities for vaccine development.

Delivery of IL-2 to the T Cell Surface Through Phosphatidylserine Permits Robust Expansion of CD8 T Cells

The phospholipid phosphatidylserine (PS) is naturally maintained on the cytoplasmic side of the plasma membrane. Independent of apoptosis, PS is redistributed to the surface of CD8 T cells in response to TCR-mediated activation. Annexin V (AnnV) is a protein known to bind PS with high affinity and has been effectively utilized to anchor antigen to the surface of CD8 T cells. To expand these studies, we aimed to exploit TCR activation driven PS exposure as a target to deliver cytokine, namely interleukin-2 (IL-2), to the surface of CD8 T cells. This was accomplished using a novel chimeric fusion protein of annexin V and interleukin 2 (AnnV-IL2). In vitro analysis revealed that AnnV-IL2 is able to specifically bind PS on the T cell surface following TCR stimulation. Consequently, AnnV-IL2 proved to be significantly more effective at enhancing T cell activation compared to recombinant IL-2. In vivo, AnnV-IL2 promotes robust expansion of antigen-specific cells capable of interferon gamma (IFNγ) production when administered following peptide vaccination. Importantly, upon antigen rechallenge, AnnV-IL2 treatment mice demonstrated a stronger secondary expansion, indicating durability of AnnV-IL2 mediated responses. Our data supports the use of AnnV-IL2 to modulate antigen-specific T cell immunity and demonstrates that the PS-AnnV axis is a feasible mechanism to target diverse cargo to CD8 T cells.

CD127+ CD94+ innate lymphoid cells expressing granulysin and perforin are expanded in patients with Crohn's disease

Phenotypic definition of helper ILC1 and NK cells is problematic due to overlapping markers. Recently we showed the identification of cytotoxic ILC3s characterized by expression of CD94. Here we analyse CD127+ ILCs and NK cells in intestinal lamina propria from healthy donors and Crohn's disease patients and identify two populations of CD127+CD94+ ILCs, designated population A and B, that can be distinguished on the expression of CD117, CD18 and cytotoxic molecules. Population B expresses granulysin, a cytotoxic molecule linked to bacterial lysis and/or chemotaxis of monocytes. Granulysin protein is secreted by population B cells upon stimulation with IL-15. Activation of population B in the presence of TGF-β strongly reduces the expression of cytotoxic effector molecules of population B. Strikingly, samples from individuals that suffer from active Crohn's disease display enhanced frequencies of granulysin-expressing effector CD127+CD94+ ILCs in comparison to controls. Thus this study identifies group 1 ILC populations which accumulate in inflamed intestinal tissue of Crohn's disease patients and may play a role in the pathology of the disease.

Signals for antigen-independent differentiation of memory CD8+ T cells

Conventional CD8+ memory T cells develop upon stimulation with foreign antigen and provide increased protection upon re-challenge. Over the past two decades, new subsets of CD8+ T cells have been identified that acquire memory features independently of antigen exposure. These antigen-inexperienced memory T cells (TAIM) are described under several names including innate memory, virtual memory, and memory phenotype. TAIM cells exhibit characteristics of conventional or true memory cells, including antigen-specific responses. In addition, they show responsiveness to innate stimuli and have been suggested to provide additional levels of protection toward infections and cancer. Here, we discuss the current understanding of TAIM cells, focusing on extrinsic and intrinsic molecular conditions that favor their development, their molecular definitions and immunological properties, as well as their transcriptional and epigenetic regulation.

Protective heterologous T cell immunity in COVID-19 induced by the trivalent MMR and Tdap vaccine antigens

BACKGROUND

T cells control viral infection, promote vaccine durability, and in coronavirus disease 2019 (COVID-19) associate with mild disease. We investigated whether prior measles-mumps-rubella (MMR) or tetanus-diphtheria-pertussis (Tdap) vaccination elicits cross-reactive T cells that mitigate COVID-19.

METHODS

Antigen-presenting cells (APC) loaded ex vivo with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), MMR, or Tdap antigens and autologous T cells from COVID-19-convalescent participants, uninfected individuals, and COVID-19 mRNA-vaccinated donors were co-cultured. T cell activation and phenotype were detected by interferon-γ (IFN-γ) enzyme-linked immunospot (ELISpot) assays and flow cytometry. ELISAs (enzyme-linked immunosorbant assays) and validation studies identified the APC-derived cytokine(s) driving T cell activation. TCR clonotyping and single-cell RNA sequencing (scRNA-seq) identified cross-reactive T cells and their transcriptional profile. A propensity-weighted analysis of COVID-19 patients estimated the effects of MMR and Tdap vaccination on COVID-19 outcomes.

FINDINGS

High correlation was observed between T cell responses to SARS-CoV-2 (spike-S1 and nucleocapsid) and MMR and Tdap proteins in COVID-19-convalescent and -vaccinated individuals. The overlapping T cell population contained an effector memory T cell subset (effector memory re-expressing CD45RA on T cells [TEMRA]) implicated in protective, anti-viral immunity, and their detection required APC-derived IL-15, known to sensitize T cells to activation. Cross-reactive TCR repertoires detected in antigen-experienced T cells recognizing SARS-CoV-2, MMR, and Tdap epitopes had TEMRA features. Indices of disease severity were reduced in MMR- or Tdap-vaccinated individuals by 32%-38% and 20%-23%, respectively, among COVID-19 patients.

CONCLUSIONS

Tdap and MMR memory T cells reactivated by SARS-CoV-2 may provide protection against severe COVID-19.

FUNDING

This study was supported by a National Institutes of Health (R01HL065095, R01AI152522, R01NS097719) donation from Barbara and Amos Hostetter and the Chleck Foundation.

A novel mechanism of lung cancer inhibition by methionine enkephalin through remodeling the immune status of the tumor microenvironment

This study examined the antitumor effect of methionine enkephalin (MENK) against lung cancer in vivo and in vitro and explored the underlying mechanisms. Changes in the immune status of the tumor microenvironment (TME) in response to MENK administration were examined in mice. MENK significantly inhibited the proliferation of lung cancer cells in vivo and in vitro by regulating the Wnt/β-catenin pathway and causing cell cycle arrest at the G0/G1 phase. Knockdown of opioid growth factor receptor abolished the effect of MENK on lung cancer cells. The immune status of the TME of mice differed between the MENK and control groups. MENK increased the infiltration of M1-type macrophages, natural killer cells, CD8+ T cells, CD4+ T cells, and dendritic cells into the TME, and decreased the proportion of myeloid inhibitory cells and M2-type macrophages. Immunohistochemical analysis of the expression of cytokines in the TME showed that MENK upregulated IL-15, IL-21, IFN-γ, and granzyme B and downregulated IL-10 and TGF-β1 in mice. Taken together, these finding indicate that MENK may be a potential agent for lung cancer treatment in the future, especially for overcoming immune escape and immune resistance.

Protective heterologous T cell immunity in COVID-19 induced by MMR and Tdap vaccine antigens

T cells are critical for control of viral infection and effective vaccination. We investigated whether prior Measles-Mumps-Rubella (MMR) or Tetanus-Diphtheria-pertussis (Tdap) vaccination elicit cross-reactive T cells that mitigate COVID-19. Using co-cultures of antigen presenting cells (APC) loaded with antigens and autologous T cells, we found a high correlation between responses to SARS-CoV-2 (Spike-S1 and Nucleocapsid) and MMR and Tdap vaccine proteins in both SARS-CoV-2 infected individuals and individuals immunized with mRNA-based SARS-CoV-2 vaccines. The overlapping T cell population contained effector memory T cells (TEMRA) previously implicated in anti-viral immunity and their activation required APC-derived IL-15. TCR- and scRNA-sequencing detected cross-reactive clones with TEMRA features among the cells recognizing SARS-CoV-2, MMR and Tdap epitopes. A propensity-weighted analysis of 73,582 COVID-19 patients revealed that severe disease outcomes (hospitalization and transfer to intensive care unit or death) were reduced in MMR or Tdap vaccinated individuals by 38-32% and 23-20% respectively. In summary, SARS-CoV-2 re-activates memory T cells generated by Tdap and MMR vaccines, which may reduce disease severity.

Cellular Immune Phenotypes and Worsening Scores of Frailty-Associated Parameters Over an 18-Month Period in the Very Old

Frailty has been related to inflammaging and certain immune parameters. In previous analyses of participants older than 80 years of age in the longitudinal BELFRAIL cohort study, the main focus was on T-cell phenotypes and the association with cytomegalovirus (CMV) serostatus and survival, finding that a CD4:CD8 ratio greater than 5 was associated with frailty, impaired activities of daily living (ADLs), and mortality (but only in women). Here, we phenotyped peripheral blood immune cells via multicolor flow cytometry and correlated these with the dynamics of changes in ADL, geriatric depression score, Mini-Mental State Examination, and Short Physical Performance Battery from baseline values over 18 months follow-up. We found that higher frequencies of B cells and late-differentiated CD8+ T cells at 18 months from baseline were associated with ADL impairment that had worsened over the preceding 18 months. There were no significant associations with monocyte, dendritic cell, or natural killer (NK) cell phenotypes. No associations with the Geriatric Depression Scale, the Mini-Mental State Examination, or the Short Physical Performance Battery were found. Thus, while these results do not establish causality, they suggest that certain adaptive immune, but not innate immune, parameters are associated with a worsened ADL in the very old.

Transcription Factors Associated With IL-15 Cytokine Signaling During NK Cell Development

Natural killer (NK) cells are lymphocytes primarily involved in innate immunity and possess important functional properties in anti-viral and anti-tumor responses; thus, these cells have broad potential for clinical utilization. NK cells originate from hematopoietic stem cells (HSCs) through the following two independent and continuous processes: early commitment from HSCs to IL-15-responsive NK cell progenitors (NKPs) and subsequent differentiation into mature NK cells in response to IL-15. IL-15 is the most important cytokine for NK cell development, is produced by both hematopoietic and nonhematopoietic cells, and functions through a distinct delivery process termed transpresentation. Upon being transpresented to NK cells, IL-15 contributes to NK cell development via the activation of several downstream signaling pathways, including the Ras-MEK-MAPK, JAK-STAT5, and PI3K-ATK-mTOR pathways. Nonetheless, the exact role of IL-15 in NK cell development has not been discussed in a consecutive and comprehensive manner. Here, we review current knowledge about the indispensable role of IL-15 in NK cell development and address which cells produce IL-15 to support NK cell development and when IL-15 exerts its function during multiple developmental stages. Specifically, we highlight how IL-15 supports NK cell development by elucidating the distinct transpresentation of IL-15 to NK cells and revealing the downstream target of IL-15 signaling during NK cell development.

Gamma-Chain Receptor Cytokines & PD-1 Manipulation to Restore HCV-Specific CD8+ T Cell Response during Chronic Hepatitis C

Hepatitis C virus (HCV)-specific CD8⁺ T cell response is essential in natural HCV infection control, but it becomes exhausted during persistent infection. Nowadays, chronic HCV infection can be resolved by direct acting anti-viral treatment, but there are still some non-responders that could benefit from CD8⁺ T cell response restoration. To become fully reactive, T cell needs the complete release of T cell receptor (TCR) signalling but, during exhaustion this is blocked by the PD-1 effect on CD28 triggering. The T cell pool sensitive to PD-1 modulation is the progenitor subset but not the terminally differentiated effector population. Nevertheless, the blockade of PD-1/PD-L1 checkpoint cannot be always enough to restore this pool. This is due to the HCV ability to impair other co-stimulatory mechanisms and metabolic pathways and to induce a pro-apoptotic state besides the TCR signalling impairment. In this sense, gamma-chain receptor cytokines involved in memory generation and maintenance, such as low-level IL-2, IL-7, IL-15, and IL-21, might carry out a positive effect on metabolic reprogramming, apoptosis blockade and restoration of co-stimulatory signalling. This review sheds light on the role of combinatory immunotherapeutic strategies to restore a reactive anti-HCV T cell response based on the mixture of PD-1 blocking plus IL-2/IL-7/IL-15/IL-21 treatment.

Effect of Various Exercise Regimens on Selected Exercise-Induced Cytokines in Healthy People

Different forms of physical activity—endurance, resistance or dynamic power—stimulate cytokine release from various tissues to the bloodstream. Receptors for exercise-induced cytokines are present in muscle tissue, adipose tissue, liver, brain, bones, cardiovascular system, immune system, pancreas, and skin. They have autocrine, paracrine and endocrine activities. Many of them regulate the myocyte growth and differentiation necessary for muscle hypertrophy and myogenesis. They also modify energy homeostasis, lipid, carbohydrate, and protein metabolism, regulate inflammation and exchange information (crosstalk) between remote organs. So far, interleukin 6 and irisin have been the best studied exercise-induced cytokines. However, many more can be grouped into myokines, hepatokines and adipomyokines. This review focuses on the less known exercise-induced cytokines such as myostatin, follistatin, decorin, brain-derived neurotrophic factor, fibroblast growth factor 21 and interleukin 15, and their relation to various forms of exercise, i.e., acute vs. chronic, regular training in healthy people.

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.