Distinct roles for IL-2 and IL-15 in the differentiation and survival of CD8+ effector and memory T cells

Optimizing CAR-T cell Culture: Differential effects of IL-2, IL-12, and IL-21 on CAR-T cells

BACKGROUND

Chimeric antigen receptor (CAR)-T therapy has demonstrated sustained clinical remission in numerous hematologic malignancies and has expanded to encompass solid tumors and autoimmune diseases. While progress is being made in establishing optimal culture conditions for CAR-T cells, the identification of the most effective cytokine for promoting their persistence in vitro remains elusive.

METHODS

Here, we employed scRNA-seq (single-cell RNA sequencing) analysis to investigate the potential alterations in biological processes within CAR-T cells following exposure to cytokines (IL-2, IL-12, and IL-21) and antigens. Transcriptomic changes in diverse CAR-T groups were compared following various treatments, with a focus on epigenetic modifications, metabolic shifts, cellular senescence, and exhaustion.

RESULTS

Our study reveals that CAR-T cells treated with antigen, IL-2, and IL-12 exhibit signs of exhaustion and senescence, whereas those treated with IL-21 do not display these characteristics. The activities of glycolysis and epigenetic changes were significantly increased by treatments with antigens, IL-2, and IL-12, while IL-21 treatment maintained the oxidative phosphorylation (OXPHOS) of CAR-T cells.

CONCLUSIONS

Our findings suggest that IL-21 may play a role in preventing senescence and could be utilized in combination with other strategies, such as IL-2 and IL-12, for CAR-T culture.

A nationwide study on immunosenescence biomarkers profile in older adults: ELSI-Brazil

Immunosenescence is a phenomenon caused by changes in the immune system, and part of these changes involves an increase in circulating immunological biomarkers, a process known as "Inflammaging." Inflammaging can be associated with many diseases related to older people. As the older population continues to grow, understanding changes in the immune system becomes essential. While prior studies assessing these alterations have been conducted in countries with Caucasian populations, this investigation marks a pioneering effort. The object of the study is to describe for the first time that the distribution of cytokines, chemokines, and growth factors serum levels, assessed by Luminex platform, has been examined in a Brazilian population-based study of older adult females and males by age. Blood samples from 2111 participants (≥50 years old) were analyzed at the baseline (2015/2016) of the ELSI-Brazil study. The exploratory variables considered in the study were age, sex, educational level, residence area, geographic region, alcohol and smoking consumption, physical activity, and self-reported medical diagnoses of hypertension, diabetes, asthma, arthritis, and cancer. The association between serum biomarker levels and age was assessed by a quantile regression model adjusted in the total population and stratified by sex. The significance level considered in the analysis was 0.05. The mean age of the participants was 62.9 years, with a slight majority of female (52.7 %). Differences were found between the sexes in the median circulating levels of the CCL11, CXCL10, and FGF biomarkers. Eight biomarkers showed significant associations with age, including the pro-inflammatory CXCL10, TNF-α, IL-6, IL-17, and IL-2; and type 2/regulatory CCL11 and IL-4, showing positive associations, and anti-inflammatory IL-1Ra showing a negative association. The results suggest similar associations between the sexes, revealing an inflammatory profile characterized by types 1 and 2. Remarkably, these findings reinforce the concept of the Inflammaging process in Brazilian population. These findings add novel insights to about the immunosenescence aspects in middle-income countries and help define biomarkers capable of monitoring inflammation in older adults.

Extracellular domains of CARs reprogramme T cell metabolism without antigen stimulation

Metabolism is an indispensable part of T cell proliferation, activation and exhaustion, yet the metabolism of chimeric antigen receptor (CAR)-T cells remains incompletely understood. CARs are composed of extracellular domains-often single-chain variable fragments (scFvs)-that determine ligand specificity and intracellular domains that trigger signalling following antigen binding. Here, we show that CARs differing only in the scFv variously reprogramme T cell metabolism. Even without exposure to antigens, some CARs increase proliferation and nutrient uptake in T cells. Using stable isotope tracers and mass spectrometry, we observed basal metabolic fluxes through glycolysis doubling and amino acid uptake overtaking anaplerosis in CAR-T cells harbouring a rituximab scFv, unlike other similar anti-CD20 scFvs. Disparate rituximab and 14G2a-based anti-GD2 CAR-T cells are similarly hypermetabolic and channel excess nutrients to nitrogen overflow metabolism. Modest overflow metabolism of CAR-T cells and metabolic compatibility between cancer cells and CAR-T cells are identified as features of efficacious CAR-T cell therapy.

Facts and Hopes on Chimeric Cytokine Agents for Cancer Immunotherapy

Cytokines are key mediators of immune responses that can modulate the antitumor activity of immune cells. Cytokines have been explored as a promising cancer immunotherapy. However, there are several challenges to cytokine therapy, especially a lack of tumor targeting, resulting in high toxicity and limited efficacy. To overcome these limitations, novel approaches have been developed to engineer cytokines with improved properties, such as chimeric cytokines. Chimeric cytokines are fusion proteins that combine different cytokine domains or link cytokines to antibodies (immunocytokines) or other molecules that can target specific receptors or cells. Chimeric cytokines can enhance the selectivity and stability of cytokines, leading to reduced toxicity and improved efficacy. In this review, we focus on two promising cytokines, IL2 and IL15, and summarize the current advances and challenges of chimeric cytokine design and application for cancer immunotherapy. Most of the current approaches focus on increasing the potency of cytokines, but another important goal is to reduce toxicity. Cytokine engineering is promising for cancer immunotherapy as it can enhance tumor targeting while minimizing adverse effects.

FKBP4 correlates with CD8+ T cells and lymphatic metastases in oral squamous cell carcinoma

OBJECTIVES

To identify the engagement of CD8+ T cells in the lymph node metastasis (LNM) of oral squamous cell carcinoma (OSCC) and significant CD8+ T cell-related genes regulating the LNM.

SUBJECTS AND METHODS

Tumor samples of primary OSCC patients were obtained (n = 71). CD8 expression in LNM- and LNM+ tumors were identified using tissue microarray (TMA)-based immunohistochemistry (IHC) and compared using the Mann-Whitney U test. The LNM status, as well as the metagene expression of CD8+ T cells of OSCC patients, were obtained from The Cancer Genome Atlas (TCGA) database. Metagenes related to LNM were screened using logistic regression analyses and further identified using TMA-based IHC.

RESULTS

CD8 was significantly positively associated with LNM (p < 0.05). Furthermore, tumors with higher expression of FKBP4 had significantly higher LNM rate (HR: 1.63; 95% CI: 1.08 ~ 2.53; p < 0.05), which was also proven using TMA-based IHC analysis.

CONCLUSION

CD8+ T cells might engage in the lymphatic metastases of OSCC. Among CD8+ T cell-related genes, FKBP4 could be a promising biomarker to predict the risk of LNM of OSCC.

OCA-B/Pou2af1 is sufficient to promote CD4+ T cell memory and prospectively identifies memory precursors

The molecular mechanisms leading to the establishment of immunological memory are inadequately understood, limiting the development of effective vaccines and durable antitumor immune therapies. Here, we show that ectopic OCA-B expression is sufficient to improve antiviral memory recall responses, while having minimal effects on primary effector responses. At peak viral response, short-lived effector T cell populations are expanded but show increased Gadd45b and Socs2 expression, while memory precursor effector cells show increased expression of Bcl2, Il7r, and Tcf7 on a per-cell basis. Using an OCA-B mCherry reporter mouse line, we observe high OCA-B expression in CD4+ central memory T cells. We show that early in viral infection, endogenously elevated OCA-B expression prospectively identifies memory precursor cells with increased survival capability and memory recall potential. Cumulatively, the results demonstrate that OCA-B is both necessary and sufficient to promote CD4 T cell memory in vivo and can be used to prospectively identify memory precursor cells.

Stat5 opposes the transcription factor Tox and rewires exhausted CD8+ T cells toward durable effector-like states during chronic antigen exposure

Rewiring exhausted CD8+ T (Tex) cells toward functional states remains a therapeutic challenge. Tex cells are epigenetically programmed by the transcription factor Tox. However, epigenetic remodeling occurs as Tex cells transition from progenitor (Texprog) to intermediate (Texint) and terminal (Texterm) subsets, suggesting development flexibility. We examined epigenetic transitions between Tex cell subsets and revealed a reciprocally antagonistic circuit between Stat5a and Tox. Stat5 directed Texint cell formation and re-instigated partial effector biology during this Texprog-to-Texint cell transition. Constitutive Stat5a activity antagonized Tox and rewired CD8+ T cells from exhaustion to a durable effector and/or natural killer (NK)-like state with superior anti-tumor potential. Temporal induction of Stat5 activity in Tex cells using an orthogonal IL-2:IL2Rβ-pair fostered Texint cell accumulation, particularly upon PD-L1 blockade. Re-engaging Stat5 also partially reprogrammed the epigenetic landscape of exhaustion and restored polyfunctionality. These data highlight therapeutic opportunities of manipulating the IL-2-Stat5 axis to rewire Tex cells toward more durably protective states.

Regulation of Dendritic Cell Functions by Vitamins as Promising Therapeutic Strategy for Immune System Disorders

A functional immune system is crucial for a healthy life, protecting from infections, tumors, or autoimmune disorders; these are accomplished by the interaction between various immune cells. Nourishment, particularly micronutrients, are very important components in the immune system balance, therefore this review emphasizes the vitamins (D, E, A, C) and Dendritic cells' subsets due to vitamins' roles in immune processes, especially on dendritic cells' functions, maturation, and cytokine production. Current studies reveal significant benefits related to vitamins, including vitamin E, which can contribute to the control of dendritic cells' function and maturation. Furthermore, vitamin D plays an immunoregulatory and anti-inflammatory role in the immune system. Metabolite of vitamin A which is called retinoic acid leads to T cells' differentiation to T helper 1 or T helper 17, so low levels of this vitamin exacerbate the menace of infectious diseases, and vitamin C has anti-oxidant effects on dendritic cells and modulate their activation and differentiation program. Additionally, the correlation between the amount of vitamin and the occurrence or progression of allergic diseases and autoimmunity disorders is discussed according to the results of previous studies.

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.

Proinflammatory IFNγ Is Produced by but Not Required for the Generation of Eomes+ Thymic Innate CD8 T Cells

Innate CD8 T cells are proinflammatory effector T cells that achieve functional maturation in the thymus prior to their export into and maturation in peripheral tissues. Innate CD8 T cells produce the Th1 cytokine IFNγ but depend on the Th2 cytokine IL-4 for their generation. Thus, innate CD8 T cells can permute the intrathymic cytokine milieu by consuming a Th2 cytokine but driving a Th1 cytokine response. The cellular source of IL-4 is the NKT2 subset of invariant NKT (iNKT) cells. Consequently, NKT2 deficiency results in the lack of innate CD8 T cells. Whether NKT2 is the only iNKT subset and whether IL-4 is the only cytokine required for innate CD8 T cell generation, however, remains unclear. Here, we employed a mouse model of NKT1 deficiency, which is achieved by overexpression of the cytokine receptor IL-2Rβ, and assessed the role of other iNKT subsets and cytokines in innate CD8 T cell differentiation. Because IL-2Rβ-transgenic mice failed to generate both NKT1 and innate CD8 T cells, we postulated an in vivo requirement for IFNγ-producing NKT1 cells for innate CD8 T cell development. In-depth analyses of IL-2Rβ-transgenic mice and IFNγ-deficient mice, however, demonstrated that neither NKT1 nor IFNγ was required to induce Eomes or to drive innate CD8 T cell generation. Instead, in vivo administration of recombinant IL-4 sufficed to restore the development of innate CD8 T cells in NKT1-deficient mice, affirming that intrathymic IL-4, and not IFNγ, is the limiting factor and key regulator of innate CD8 T cell generation in the thymus.

Blocking of oestrogen signals improves anti-tumour effect regardless of oestrogen receptor alpha expression in cancer cells

BACKGROUND

Anti-oestrogenic therapy has been used for breast cancer patients with oestrogen susceptibility cancer cells. However, little has been known about its potential role for immune cell biology within TME, particularly in cancer patients without oestrogen sensitivity of tumour cells. Therefore, we aimed to study the effect of oestrogen on immunity within TME.

METHODS

Using a clinical dataset, immune cells of humans and mice, female mice with and without ovaries, and several murine ERα-negative cancer cell lines, we evaluated the effect of oestrogen on immunity in TME.

RESULTS

Clinical data analysis suggested oestrogen's suppressive efficacy against CTLs. Additionally, in vitro and in vivo experiments revealed intra-tumoural CTLs' direct repressive action by oestrogen in both mice and humans; blockade of oestrogen signals cancelled its immunosuppression resulting in tumour growth reduction in vivo. Most notably, immunotherapy (immune checkpoint inhibitor; ICI) combined with anti-oestrogenic therapy exhibited a dramatic anti-tumour effect.

CONCLUSIONS

This study provides novel insights into how oestrogen contributes to tumour progression and a therapeutic rationale for blocking oestrogen signalling to boost the anti-tumour effect of ICI, regardless of tumour cells' ERα expression.

Intratumoral dendritic cell-CD4+ T helper cell niches enable CD8+ T cell differentiation following PD-1 blockade in hepatocellular carcinoma

Despite no apparent defects in T cell priming and recruitment to tumors, a large subset of T cell rich tumors fail to respond to immune checkpoint blockade (ICB). We leveraged a neoadjuvant anti-PD-1 trial in patients with hepatocellular carcinoma (HCC), as well as additional samples collected from patients treated off-label, to explore correlates of response to ICB within T cell-rich tumors. We show that ICB response correlated with the clonal expansion of intratumoral CXCL13+CH25H+IL-21+PD-1+CD4+ T helper cells ("CXCL13+ TH") and Granzyme K+ PD-1+ effector-like CD8+ T cells, whereas terminally exhausted CD39hiTOXhiPD-1hiCD8+ T cells dominated in nonresponders. CD4+ and CD8+ T cell clones that expanded post-treatment were found in pretreatment biopsies. Notably, PD-1+TCF-1+ (Progenitor-exhausted) CD8+ T cells shared clones mainly with effector-like cells in responders or terminally exhausted cells in nonresponders, suggesting that local CD8+ T cell differentiation occurs upon ICB. We found that these Progenitor CD8+ T cells interact with CXCL13+ TH within cellular triads around dendritic cells enriched in maturation and regulatory molecules, or "mregDC". These results suggest that discrete intratumoral niches that include mregDC and CXCL13+ TH control the differentiation of tumor-specific Progenitor exhasuted CD8+ T cells following ICB.

The Interrelation between Interleukin-2 and Schizophrenia

Interleukin-2 (IL-2) is a growth factor that regulates T-cell autocrine secretion and has long been considered to be closely related to immune response. With the advance in neuroinflammation theory and immunology research on schizophrenia, it is interesting and meaningful to discuss the possible role of IL-2 in schizophrenia. Here, we reviewed a series of studies published from the 1990s and found that IL-2 was closely associated with schizophrenia. For example, IL-2 is responsible for mediating toxic reactions, which are the causes of schizophrenia symptoms in patients, and such symptoms resolve after discontinuation of the drug. In addition, we focused on the changes of IL-2 in the onset, progression and treatment of schizophrenia and the possible mechanisms by which IL-2 affects schizophrenia. Our review suggests that IL-2 is associated with schizophrenia and plays a role in its pathogenesis, and progression IL-2 and sIL-2R could serve as potential biomarkers of schizophrenia.

cBAF complex components and MYC cooperate early in CD8+ T cell fate

The identification of mechanisms to promote memory T (Tmem) cells has important implications for vaccination and anti-cancer immunotherapy1-4. Using a CRISPR-based screen for negative regulators of Tmem cell generation in vivo5, here we identify multiple components of the mammalian canonical BRG1/BRM-associated factor (cBAF)6,7. Several components of the cBAF complex are essential for the differentiation of activated CD8+ T cells into T effector (Teff) cells, and their loss promotes Tmem cell formation in vivo. During the first division of activated CD8+ T cells, cBAF and MYC8 frequently co-assort asymmetrically to the two daughter cells. Daughter cells with high MYC and high cBAF display a cell fate trajectory towards Teff cells, whereas those with low MYC and low cBAF preferentially differentiate towards Tmem cells. The cBAF complex and MYC physically interact to establish the chromatin landscape in activated CD8+ T cells. Treatment of naive CD8+ T cells with a putative cBAF inhibitor during the first 48 h of activation, before the generation of chimeric antigen receptor T (CAR-T) cells, markedly improves efficacy in a mouse solid tumour model. Our results establish cBAF as a negative determinant of Tmem cell fate and suggest that manipulation of cBAF early in T cell differentiation can improve cancer immunotherapy.

Autocrine and paracrine IL-2 signals collaborate to regulate distinct phases of CD8 T cell memory

Differential interleukin-2 (IL-2) signaling and production are associated with disparate effector and memory fates. Whether the IL-2 signals perceived by CD8 T cells come from autocrine or paracrine sources, the timing of IL-2 signaling and their differential impact on CD8 T cell responses remain unclear. Using distinct models of germline and conditional IL-2 ablation in post-thymic CD8 T cells, this study shows that paracrine IL-2 is sufficient to drive optimal primary expansion, effector and memory differentiation, and metabolic function. In contrast, autocrine IL-2 is uniquely required during primary expansion to program robust secondary expansion potential in memory-fated cells. This study further shows that IL-2 production by antigen-specific CD8 T cells is largely independent of CD4 licensing of dendritic cells (DCs) in inflammatory infections with robust DC activation. These findings bear implications for immunizations and adoptive T cell immunotherapies, where effector and memory functions may be commandeered through IL-2 programming.

Intrinsic IL-2 production by effector CD8 T cells affects IL-2 signaling and promotes fate decisions, stemness, and protection

Here, we show that the capacity to manufacture IL-2 identifies constituents of the expanded CD8 T cell effector pool that display stem-like features, preferentially survive, rapidly attain memory traits, resist exhaustion, and control chronic viral challenges. The cell-intrinsic synthesis of IL-2 by CD8 T cells attenuates the ability to receive IL-2-dependent STAT5 signals, thereby limiting terminal effector formation, endowing the IL-2-producing effector subset with superior protective powers. In contrast, the non-IL-2-producing effector cells respond to IL-2 signals and gain effector traits at the expense of memory formation. Despite having distinct properties during the effector phase, IL-2-producing and nonproducing CD8 T cells appear to converge transcriptionally as memory matures to form populations with equal recall abilities. Therefore, the potential to produce IL-2 during the effector, but not memory stage, is a consequential feature that dictates the protective capabilities of the response.

A Novel Anti-B7-H3 × Anti-CD3 Bispecific Antibody with Potent Antitumor Activity

B7-H3 plays an important role in tumor apoptosis, proliferation, adhesion, angiogenesis, invasion, migration, and evasion of immune surveillance. It is overexpressed in various human solid tumor tissues. In patients, B7-H3 overexpression correlates with advanced stages, poor clinical outcomes, and resistance to therapy. The roles of B7-H3 in tumor progression make it a potential candidate for targeted therapy. Here, we generated a mouse anti-human B7-H3 antibody and demonstrated its binding activity via Tongji University Suzhou Instituteprotein-based and cell-based assays. We then developed a novel format anti-B7-H3 × anti-CD3 bispecific antibody based on the antibody-binding fragment of the anti-B7-H3 antibody and single-chain variable fragment structure of anti-CD3 antibody (OKT3) and demonstrated that this bispecific antibody mediated potent cytotoxic activities against various B7-H3-positive tumor cell lines in vitro by improving T cell activation and proliferation. This bispecific antibody also demonstrated potent antitumor activity in humanized mice xenograft models. These results revealed that the novel anti-B7-H3 × anti-CD3 bispecific antibody has the potential to be employed in treatment of B7-H3-positive solid tumors.

Prosurvival IL-7-Stimulated Weak Strength of mTORC1-S6K Controls T Cell Memory via Transcriptional FOXO1-TCF1-Id3 and Metabolic AMPKα1-ULK1-ATG7 Pathways

CD8⁺ memory T (T_M) cells play a critical role in immune defense against infection. Two common γ-chain family cytokines, IL-2 and IL-7, although triggering the same mTORC1-S6K pathway, distinctly induce effector T (T_E) cells and T_M cells, respectively, but the underlying mechanism(s) remains elusive. In this study, we generated IL-7R-/and AMPKα1-knockout (KO)/OTI mice. By using genetic and pharmaceutical tools, we demonstrate that IL-7 deficiency represses expression of FOXO1, TCF1, p-AMPKα1 (T₁₇₂), and p-ULK1 (S₅₅₅) and abolishes T cell memory differentiation in IL-7R KO T cells after Listeria monocytogenesis rLmOVA infection. IL-2- and IL-7-stimulated strong and weak S6K (IL-2/S6K^strong and IL-7/S6K^weak) signals control short-lived IL-7R^-CD62L^-KLRG1⁺ T_E and long-term IL-7R⁺CD62L⁺KLRG1^- T_M cell formations, respectively. To assess underlying molecular pathway(s), we performed flow cytometry, Western blotting, confocal microscopy, and Seahorse assay analyses by using the IL-7/S6K^weak-stimulated T_M (IL-7/T_M) and the control IL-2/S6K^strong-stimulated T_E (IL-2/T_E) cells. We determine that the IL-7/S6K^weak signal activates transcriptional FOXO1, TCF1, and Id3 and metabolic p-AMPKα1, p-ULK1, and ATG7 molecules in IL-7/T_M cells. IL-7/T_M cells upregulate IL-7R and CD62L, promote mitochondria biogenesis and fatty acid oxidation metabolism, and show long-term cell survival and functional recall responses. Interestingly, AMPKα1 deficiency abolishes the AMPKα1 but maintains the FOXO1 pathway and induces a metabolic switch from fatty acid oxidation to glycolysis in AMPKα1 KO IL-7/T_M cells, leading to loss of cell survival and recall responses. Taken together, our data demonstrate that IL-7-stimulated weak strength of mTORC1-S6K signaling controls T cell memory via activation of transcriptional FOXO1-TCF1-Id3 and metabolic AMPKα1-ULK1-ATG7 pathways. This (to our knowledge) novel finding provides a new mechanism for a distinct IL-2/IL-7 stimulation model in T cell memory and greatly impacts vaccine development.

Immune response against toxoplasmosis-some recent updates RH: Toxoplasma gondii immune response

AIMS

Cytokines, soluble mediators of immunity, are key factors of the innate and adaptive immune system. They are secreted from and interact with various types of immune cells to manipulate host body's immune cell physiology for a counter-attack on the foreign body. A study was designed to explore the mechanism of Toxoplasma gondii (T. gondii) resistance from host immune response.

METHODS AND RESULTS

The published data on aspect of host (murine and human) immune response against T. gondii was taken from Google scholar and PubMed. Most relevant literature was included in this study. The basic mechanism of immune response starts from the interactions of antigens with host immune cells to trigger the production of cytokines (pro-inflammatory and anti-inflammatory) which then act by forming a cytokinome (network of cytokine). Their secretory equilibrium is essential for endowing resistance to the host against infectious diseases, particularly toxoplasmosis. A narrow balance lying between Th1, Th2, and Th17 cytokines (as demonstrated until now) is essential for the development of resistance against T. gondii as well as for the survival of host. Excessive production of pro-inflammatory cytokines leads to tissue damage resulting in the production of anti-inflammatory cytokines which enhances the proliferation of Toxoplasma. Stress and other infectious diseases (human immunodeficiency virus (HIV)) that weaken the host immunity particularly the cellular component, make the host susceptible to toxoplasmosis especially in pregnant women.

CONCLUSION

The current review findings state that in vitro harvesting of IL12 from DCs, Np and MΦ upon exposure with T. gondii might be a source for therapeutic use in toxoplasmosis. Current review also suggests that therapeutic interventions leading to up-regulation/supplementation of SOCS-3, IL12, and IFNγ to the infected host could be a solution to sterile immunity against T. gondii infection. This would be of interest particularly in patients passing through immunosuppression owing to any reason like the ones receiving anti-cancer therapy, the ones undergoing immunosuppressive therapy for graft/transplantation, the ones suffering from immunodeficiency virus (HIV) or having AIDS. Another imortant suggestion is to launch the efforts for a vaccine based on GRA6Nt or other similar antigens of T. gondii as a probable tool to destroy tissue cysts.

Spatial determinates of effector and memory CD8+ T cell fates

The lymph node plays a critical role in mounting an adaptive immune response to infection, clearance of foreign pathogens, and cancer immunosurveillance. Within this complex structure, intranodal migration is vital for CD8⁺ T cell activation and differentiation. Combining tissue clearing and volumetric light sheet fluorescent microscopy of intact lymph nodes has allowed us to explore the spatial regulation of T cell fates. This has determined that short-lived effector (T_SLEC ) are imprinted in peripheral lymph node interfollicular regions, due to CXCR3 migration. In contrast, stem-like memory cell (T_SCM ) differentiation is determined in the T cell paracortex. Here, we detail the inflammatory and chemokine regulators of spatially restricted T cell differentiation, with a focus on how to promote T_SCM . We propose a default pathway for T_SCM differentiation due to CCR7-directed segregation of precursors away from the inflammatory effector niche. Although volumetric imaging has revealed the consequences of intranodal migration, we still lack knowledge of how this is orchestrated within a complex chemokine environment. Toward this goal, we highlight the potential of combining microfluidic chambers with pre-determined complexity and subcellular resolution microscopy.

Alloantigen-activated (AAA) CD4+ T cells reinvigorate host endogenous T cell immunity to eliminate pre-established tumors in mice

BACKGROUND

Cancer vaccines that induce endogenous antitumor immunity represent an ideal strategy to overcome intractable cancers. However, doing this against a pre-established cancer using autologous immune cells has proven to be challenging. "Allogeneic effects" refers to the induction of an endogenous immune response upon adoptive transfer of allogeneic lymphocytes without utilizing hematopoietic stem cell transplantation. While allogeneic lymphocytes have a potent ability to activate host immunity as a cell adjuvant, novel strategies that can activate endogenous antitumor activity in cancer patients remain an unmet need. In this study, we established a new method to destroy pre-developed tumors and confer potent antitumor immunity in mice using alloantigen-activated CD4⁺ (named AAA-CD4⁺) T cells.

METHODS

AAA-CD4⁺ T cells were generated from CD4⁺ T cells isolated from BALB/c mice in cultures with dendritic cells (DCs) induced from C57BL/6 (B6) mice. In this culture, allogeneic CD4⁺ T cells that recognize and react to B6 mouse-derived alloantigens are preferentially activated. These AAA-CD4⁺ T cells were directly injected into the pre-established melanoma in B6 mice to assess their ability to elicit antitumor immunity in vivo.

RESULTS

Upon intratumoral injection, these AAA-CD4⁺ T cells underwent a dramatic expansion in the tumor and secreted high levels of IFN-γ and IL-2. This was accompanied by markedly increased infiltration of host-derived CD8⁺ T cells, CD4⁺ T cells, natural killer (NK) cells, DCs, and type-1 like macrophages. Selective depletion of host CD8⁺ T cells, rather than NK cells, abrogated this therapeutic effect. Thus, intratumoral administration of AAA-CD4⁺ T cells results in a robust endogenous CD8⁺ T cell response that destroys pre-established melanoma. This locally induced antitumor immunity elicited systemic protection to eliminate tumors at distal sites, persisted over 6 months in vivo, and protected the animals from tumor re-challenge. Notably, the injected AAA-CD4⁺ T cells disappeared within 7 days and caused no adverse reactions.

CONCLUSIONS

Our findings indicate that AAA-CD4⁺ T cells reinvigorate endogenous cytotoxic T cells to eradicate pre-established melanoma and induce long-term protective antitumor immunity. This approach can be immediately applied to patients with advanced melanoma and may have broad implications in the treatment of other types of solid tumors.

Co-Ordination of Mucosal B Cell and CD8 T Cell Memory by Tissue-Resident CD4 Helper T Cells

Adaptive cellular immunity plays a major role in clearing microbial invasion of mucosal tissues in mammals. Following the clearance of primary pathogens, memory lymphocytes are established both systemically and locally at pathogen entry sites. Recently, resident memory CD8 T and B cells (T_RM and B_RM respectively), which are parked mainly in non-lymphoid mucosal tissues, were characterized and demonstrated to be essential for protection against secondary microbial invasion. Here we reviewed the current understanding of the cellular and molecular cues regulating CD8 T_RM and B_RM development, maintenance and function. We focused particularly on elucidating the role of a novel tissue-resident helper T (T_RH) cell population in assisting T_RM and B_RM responses in the respiratory mucosa following viral infection. Finally, we argue that the promotion of T_RH responses by future mucosal vaccines would be key to the development of successful universal influenza or coronavirus vaccines, providing long-lasting immunity against a broad spectrum of viral strains.

Triple-modality therapy maximizes antitumor immune responses in a mouse model of mesothelioma

Malignant pleural mesothelioma (MPM) is an intractable disease with an extremely poor prognosis. Our clinical protocol for MPM of subablative radiotherapy (RT) followed by radical surgery achieved better survival compared to other multimodal treatments, but local relapse and metastasis remain a problem. This subablative RT elicits an antitumoral immune response that is limited by the immunosuppressive microenvironment generated by regulatory T (T_reg) cells. The antitumor effect of immunotherapy to simultaneously modulate the immune activation and the immune suppression after subablative RT has not been investigated in MPM. Herein, we demonstrated a rationale to combine interleukin-15 (IL-15) superagonist (IL-15SA) and glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR) agonist (DTA-1) with subablative RT in mesothelioma. IL-15SA boosted the systemic expansion of specific antitumoral memory CD8⁺ T cells that were induced by RT in mice. Their effect, however, was limited by the up-regulation and activation of T_reg cells in the radiated tumor microenvironment. Hence, selective depletion of intratumoral T_reg cells through DTA-1 enhanced the benefit of subablative RT in combination with IL-15SA. The addition of surgical resection of the radiated tumor in combination with IL-15SA and DTA-1 maximized the benefit of RT and was accompanied by a reproducible abscopal response in a concomitant tumor model. These data support the development of clinical trials in MPM to test such treatment options for patients with locally advanced or metastatic tumors.

Cancer immunotherapy: A comprehensive appraisal of its modes of application

Conventional cancer treatments such as chemotherapy and radiation therapy have reached their therapeutic potential, leaving a gap for developing more effective cancer therapeutics. Cancer cells evade the immune system using various mechanisms of immune tolerance, underlying the potential impact of immunotherapy in the treatment of cancer. Immunotherapy includes several approaches such as activating the immune system in a cytokine-dependent manner, manipulating the feedback mechanisms involved in the immune response, enhancing the immune response via lymphocyte expansion and using cancer vaccines to elicit long-lasting, robust responses. These techniques can be used as monotherapies or combination therapies. The present review describes the immune-based mechanisms involved in tumor cell proliferation and maintenance and the rationale underlying various treatment methods. In addition, the present review provides insight into the potential of immunotherapy used alone or in combination with various types of therapeutics.

Developing a JAK Inhibitor for Targeted Local Delivery: Ruxolitinib Cream

Named after the two-faced Roman god of doorways, Janus kinases (JAKs) represent a class of tyrosine kinases. The JAK signaling pathway is pivotal for the downstream signaling of inflammatory cytokines, including interleukins, interferons, and multiple growth factors. This article provides an overview of the JAK pathway and signaling, its significance in immune-mediated dermatologic diseases and the development of a targeted, localized option of a selective JAK inhibitor, ruxolitinib cream. In the early 1990s, various discovery and clinical development programs were initiated to explore pharmaceutical inhibition of the JAK-STAT pathway. Incyte Corporation launched a strategy to identify molecules suitable for both topical as well as oral delivery. Ruxolitinib was designed as a molecule with low nanomolar potency selective for JAK1 and 2 enzymes, but without significant inhibition of non-JAK kinases, as well as physicochemical properties for both topical and oral administration. An oil-in-water emulsified ruxolitinib cream formulation was developed for topical application and was studied in multiple immune-mediated dermatologic diseases including psoriasis, alopecia areata, atopic dermatitis and vitiligo. Ruxolitinib cream represents a novel, JAK1/2 selective therapy that can be delivered directly to the skin to treat a number of cytokine-driven, inflammatory dermatoses.

Differential Effects of IL2Rα and IL15Rα over the Stability of the Common Beta-Gamma Signaling Subunits of the IL2 and IL15 Receptors

Interleukin (IL) 2 and IL15 are two members of the common gamma chain cytokine family, involved in the regulation of the T cell differentiation process. Both molecules use a specific alpha subunit, IL2Rα and IL15Rα, and share the same beta and gamma chains signaling receptors. The presence of the specific alpha subunit modulates the T cell ability to compete for both soluble cytokines while the beta and gamma subunits are responsible for the signal transduction. Recent experimental results point out that the specific alpha subunits modulate the capacity of IL2 and IL15 to induce the differentiation of stimulated T cells. In other membrane receptors, the outcome of the signal transduction has been associated with the strength of the interaction of the signaling subunits. Here, we investigate how IL2Rα and IL15Rα modulate the stability of their signaling complexes by combining molecular dynamics simulations and free energy calculations. Our simulations predict that IL2Rα binding destabilizes the β-γ_c interaction mediated by IL2, while IL15Rα has the opposite effect. These results explain the ability of IL2Rα and IL15Rα to modulate the signaling outcome and suggest new strategies for the development of better CD8⁺ T cell differentiation protocols for adoptive cell transfer (ACT).

Runx proteins and transcriptional mechanisms that govern memory CD8 T cell development

Adaptive immunity to intracellular pathogens and tumors is mediated by antigen-experienced CD8 T cells. Individual naive CD8 T cells have the potential to differentiate into a diverse array of antigen-experienced subsets that exhibit distinct effector functions, life spans, anatomic positioning, and potential for regenerating an entirely new immune response during iterative pathogenic exposures. The developmental process by which activated naive cells undergo diversification involves regulation of chromatin structure and transcription but is not entirely understood. This review examines how alterations in chromatin structure, transcription factor binding, extracellular signals, and single-cell gene expression explain the differential development of distinct effector (T_EFF ) and memory (T_MEM ) CD8 T cell subsets. Special emphasis is placed on how Runx proteins function with additional transcription factors to pioneer changes in chromatin accessibility and drive transcriptional programs that establish the core attributes of cytotoxic T lymphocytes, subdivide circulating and non-circulating T_MEM cell subsets, and govern terminal differentiation. The discussion integrates the roles of specific cytokine signals, transcriptional circuits and how regulation of individual nucleosomes and RNA polymerase II activity can contribute to the process of differentiation. A model that integrates many of these features is discussed to conceptualize how activated CD8 T cells arrive at their fates.

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.

Single-Dose Anti-PD-L1/IL-15 Fusion Protein KD033 Generates Synergistic Antitumor Immunity with Robust Tumor-Immune Gene Signatures and Memory Responses

Immunocytokines hold great potential as anticancer agents, as they use a specific antitumor antibody to deliver an immune-activating cytokine directly to the immunosuppressive tumor microenvironment (TME). We have developed a novel immunocytokine (KD033) composed of a fully human, high-affinity antiprogrammed death-ligand 1 (PD-L1) linked to the sushi-domain of the human IL-15/IL-15 receptor alpha (IL-15/IL-15Rα) complex. A murine PD-L1 cross-reactive KD033 surrogate (srKD033) and a nontargeting antibody (ntKD033) were also developed to investigate mechanism of action in murine tumor models. Efficacy analyses showed a robust antitumor effect of single-dose srKD033 in several diverse syngeneic murine tumor models. In a CT26 murine colon tumor model, single-dose srKD033 produced durable antitumor immunity as evidenced by resistance to subsequent tumor rechallenges. Mice responding to srKD033 treatment showed increased retention of PD-L1/IL-15 in the TME which likely facilitated prolonged IL-15-induced expansion of cytotoxic cells. Importantly, target-based PD-L1/IL-15 delivery via srKD033 was well-tolerated and induced significant antitumor activity in murine carcinoma models that are non- or minimally responsive to IL-15 or anti-PD-L1/PD-1 monotherapy.

Divergent Role for STAT5 in the Adaptive Responses of Natural Killer Cells

Natural killer (NK) cells are innate lymphocytes with the capacity to elicit adaptive features, including clonal expansion and immunological memory. Because signal transducer and activator of transcription 5 (STAT5) is essential for NK cell development, the roles of this transcription factor and its upstream cytokines interleukin-2 (IL-2) and IL-15 during infection have not been carefully investigated. In this study, we investigate how STAT5 regulates transcription during viral infection. We demonstrate that STAT5 is induced in NK cells by IL-12 and STAT4 early after infection and that partial STAT5 deficiency results in a defective capacity of NK cells to generate long-lived memory cells. Furthermore, we find a functional dichotomy of IL-2 and IL-15 signaling outputs during viral infection, whereby both cytokines drive clonal expansion, but only IL-15 is required for memory NK cell survival. We thus highlight a role for STAT5 signaling in promoting an optimal anti-viral NK cell response.

Wiedemann et al. demonstrate that Stat5a and Stat5b are induced by IL-12 and STAT4 signaling in NK cells following MCMV infection. They further provide evidence that the cytokines IL-2 and IL-15 upstream of STAT5 differentially promote the early and late stages of the adaptive NK cell response to MCMV infection.

Influenza sequelae: from immune modulation to persistent alveolitis

Acute influenza virus infections are a global public health concern accounting for millions of illnesses worldwide ranging from mild to severe with, at time, severe complications. Once an individual is infected, the immune system is triggered in response to the pathogen. This immune response can be beneficial ultimately leading to the clearance of the viral infection and establishment of immune memory mechanisms. However, it can be detrimental by increasing susceptibility to secondary bacterial infections and resulting in permanent changes to the lung architecture, in the form of fibrotic sequelae. Here, we review influenza associated bacterial super-infection, the formation of T-cell memory, and persistent lung injury resulting from influenza infection.

Memory CD8+ T cell responses to cancer

Long-lived memory CD8+ T cells play important roles in tumor immunity. Studies over the past two decades have identified four subsets of memory CD8+ T cells - central, effector, stem-like, and tissue resident memory - that either circulate through blood, lymphoid and peripheral organs, or reside in tissues where cancers develop. In this article, we will review studies from both pre-clinical mouse models and human patients to summarize the phenotype, distribution and unique features of each memory subset, and highlight specific roles of each subset in anti-tumor immunity. Moreover, we will discuss how stem-cell like and resident memory CD8+ T cell subsets relate to exhausted tumor-infiltrating lymphocytes (TIL) populations. These studies reveal how memory CD8+ T cell subsets together orchestrate durable immunity to cancer.

Common gamma chain cytokines and CD8 T cells in cancer

Overcoming exhaustion-associated dysfunctions and generating antigen-specific CD8 T cells with the ability to persist in the host and mediate effective long-term anti-tumor immunity is the final aim of cancer immunotherapy. To achieve this goal, immuno-modulatory properties of the common gamma-chain (γ_c) family of cytokines, that includes IL-2, IL-7, IL-15 and IL-21, have been used to fine-tune and/or complement current immunotherapeutic protocols. These agents potentiate CD8 T cell expansion and functions particularly in the context of immune checkpoint (IC) blockade, shape their differentiation, improve their persistence in vivo and alternatively, influence distinct aspects of the T cell exhaustion program. Despite these properties, the intrinsic impact of cytokines on CD8 T cell exhaustion has remained largely unexplored impeding optimal therapeutic use of these agents. In this review, we will discuss current knowledge regarding the influence of relevant γ_c cytokines on CD8 T cell differentiation and function based on clinical data and preclinical studies in murine models of cancer and chronic viral infection. We will restate the place of these agents in current immunotherapeutic regimens such as IC checkpoint blockade and adoptive cell therapy. Finally, we will discuss how γ_c cytokine signaling pathways regulate T cell immunity during cancer and whether targeting these pathways may sustain an effective and durable T cell response in patients.

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

IL-15 is a member of the common gamma chain family of cytokines and plays important roles in regulating several aspects of innate and adaptive immunity. Besides its established role in controlling homeostatic proliferation and survival of memory CD8⁺ T cells and natural killer cells, recent findings demonstrate that inflammatory IL-15 can also stimulate a variety of effector functions, such as enhanced cytotoxicity, entry into the cell cycle, and trafficking into non-lymphoid tissues. Here, we discuss how IL-15 is critical in regulating many functions of memory CD8⁺ T cells and how these processes act collectively to ensure optimal protective cellular immunity against re-infections.

JAK/STAT Cytokine Signaling at the Crossroad of NK Cell Development and Maturation

Natural Killer (NK) cells are cytotoxic lymphocytes of the innate immune system and play a critical role in anti-viral and anti-tumor responses. NK cells develop in the bone marrow from hematopoietic stem cells (HSCs) that differentiate through common lymphoid progenitors (CLPs) to NK lineage-restricted progenitors (NKPs). The orchestrated action of multiple cytokines is crucial for NK cell development and maturation. Many of these cytokines such as IL-2, IL-7, IL-12, IL-15, IL-21, IL-27, and interferons (IFNs) signal via the Janus Kinase / Signal Transducer and Activator of Transcription (JAK/STAT) pathway. We here review the current knowledge about these cytokines and the downstream signaling involved in the development and maturation of conventional NK cells and their close relatives, innate lymphoid cells type 1 (ILC1). We further discuss the role of suppressor of cytokine signaling (SOCS) proteins in NK cells and highlight their potential for therapeutic application.

Contaminated feed-borne Bacillus cereus aggravates respiratory distress post avian influenza virus H9N2 infection by inducing pneumonia

Avian influenza virus subtype H9N2 is identified in chickens with respiratory disease while Bacillus cereus (B. cereus) has been frequently isolated from chicken feed in China. However, the roles of co-infection with these two pathogens remain unclear. In the present study, SPF chicks were intragastrically administered with 10⁸ CFU/mL of B. cereus for 7 days and then inoculated intranasally with 100 EID₅₀ of H9N2 three days later. Alternatively, chickens were initially inoculated with H9N2 and then with B. cereus for one week. Post administration, typical respiratory distress persisted for 5 days in both co-infection groups. Gizzard erosions developed in the groups B. cereus/H9N2 and B. cereus group on 7^th day while in group H9N2/B. cereus on 14^th day. More importantly, both air-sac lesions and lung damage increased significantly in the co-infection group. Significant inflammatory changes were observed in the B. cereus group from day 7 to day 21. Moreover, higher loads of H9N2 virus were found in the co-infected groups than in the H9N2 group. Newcastle Disease Virus (NDV) specific antibodies were decreased significantly in the H9N2/B. cereus group compared to the B. cereus and the B. cereus/H9N2 groups. Nonspecific IgA titers were reduced significantly in the B. cereus group and the H9N2/B. cereus group compared to the control group. In addition to this, lower lymphocyte proliferation was found in the con-infection groups and the H9N2 group. Hence, feed-borne B. cereus contamination potentially exacerbates gizzard ulceration and aggravates H9N2-induced respiratory distress by inhibiting antibody-mediated immunity and pathogen clearance. Thus controlling the B. cereus contamination in poultry feed is immediately needed.

Cytokine-Mediated Regulation of CD8 T-Cell Responses During Acute and Chronic Viral Infection

The common γ-chain cytokines, interleukin (IL)-2, IL-7, and IL-15, regulate critical aspects of antiviral CD8 T-cell responses. During acute infections, IL-2 controls expansion and differentiation of antiviral CD8 T cells, whereas IL-7 and IL-15 are key cytokines to maintain memory CD8 T cells long term in an antigen-independent manner. On the other hand, during chronic infections, in which T-cell exhaustion is established, precise roles of these cytokines in regulation of antiviral CD8 T-cell responses are not well defined. Nonetheless, administration of IL-2, IL-7, or IL-15 can increase function of exhausted CD8 T cells, and thus can be an attractive therapeutic approach. A new subset of stem-cell-like CD8 T cells, which provides a proliferative burst after programmed cell death (PD)-1 therapy, has been recently described during chronic viral infection. Further understanding of cytokine-mediated regulation of this CD8 T-cell subset will improve cytokine therapies to treat chronic infections and cancer in combination with immune checkpoint inhibitors.

Regulation of Effector and Memory CD8 T Cell Differentiation by IL-2-A Balancing Act

Interleukin-2 (IL-2) regulates key aspects of CD8 T cell biology–signaling through distinct pathways IL-2 triggers critical metabolic and transcriptional changes that lead to a spectrum of physiological outcomes such as cell survival, proliferation, and effector differentiation. In addition to driving effector differentiation, IL-2 signals are also critical for formation of long-lived CD8 T cell memory. This review discusses a model of rheostatic control of CD8 T cell effector and memory differentiation by IL-2, wherein the timing, duration, dose, and source of IL-2 signals are considered in fine-tuning the balance of key transcriptional regulators of cell fate.

CD122 signaling in CD8+ memory T cells drives costimulation-independent rejection

Interrupting T cell costimulatory signals as a strategy to control undesired immune responses, such as occur in autoimmunity or transplantation, has the potential to alleviate many of the unwanted side effects associated with current immunosuppressive therapies. Belatacept, a high-affinity version of CTLA4-Ig that blocks ligand ligation to CD28, has been approved for use in kidney transplant recipients. Despite the long-term benefits associated with its use, such as improved renal function and lower cardiovascular risk, a subset of patients treated with belatacept experience elevated rates of acute T cell-mediated rejection, tempering enthusiasm for its use. Here we demonstrate that costimulation-independent T cell alloreactivity relies on signaling through CD122, the shared IL-2 and IL-15 receptor β-chain. Combined costimulatory and CD122 blockade improved survival of transplanted tissue in mice and nonhuman primates by controlling proliferation and effector function of CD8+ T cells. The high-affinity IL-2 receptor was dispensable for memory CD8+ T cell responses, whereas signaling through CD122 as a component of the high-affinity IL-15 receptor was critical for costimulation-independent memory CD8+ T cell recall, distinguishing specific roles for IL-2 and IL-15 in T cell activation. These studies outline a novel approach for clinical optimization of costimulatory blockade strategies in transplantation by targeting CD122.

Induction of CD4 T cell memory by local cellular collectivity

Cell differentiation is directed by signals driving progenitors into specialized cell types. This process can involve collective decision-making, when differentiating cells determine their lineage choice by interacting with each other. We used live-cell imaging in microwell arrays to study collective processes affecting differentiation of naïve CD4+ T cells into memory precursors. We found that differentiation of precursor memory T cells sharply increases above a threshold number of locally interacting cells. These homotypic interactions involve the cytokines interleukin-2 (IL-2) and IL-6, which affect memory differentiation orthogonal to their effect on proliferation and survival. Mathematical modeling suggests that the differentiation rate is continuously modulated by the instantaneous number of locally interacting cells. This cellular collectivity can prioritize allocation of immune memory to stronger responses.

Epigenetic Maintenance of Acquired Gene Expression Programs during Memory CD8 T Cell Homeostasis

Memory CD8 T cells have a unique ability to provide lifelong immunity against pathogens containing their cognate epitope. Because of their ability to provide lifelong protection, the generation of memory T cells is now a major focus for current vaccination or adoptive cell therapy approaches to treat chronic viral infections and cancer. It is now clear that maintenance of memory CD8 T cells occurs through a process of antigen-independent homeostatic proliferation, which is regulated in part by the gamma chain cytokines IL-7 and IL-15. Here, we will describe the role of these cytokines in the survival and self-renewal of memory CD8 T cells. Further, we will describe the role of epigenetics in the maintenance of acquired functions among memory CD8 T cells during homeostatic proliferation.

CD4+ T Cell Help Confers a Cytotoxic T Cell Effector Program Including Coinhibitory Receptor Downregulation and Increased Tissue Invasiveness

CD4⁺ T cells optimize the cytotoxic T cell (CTL) response in magnitude and quality, by unknown molecular mechanisms. We here present the transcriptomic changes in CTLs resulting from CD4⁺ T cell help after anti-cancer vaccination or virus infection. The gene expression signatures revealed that CD4⁺ T cell help during priming optimized CTLs in expression of cytotoxic effector molecules and many other functions that ensured efficacy of CTLs throughout their life cycle. Key features included downregulation of PD-1 and other coinhibitory receptors that impede CTL activity, and increased motility and migration capacities. "Helped" CTLs acquired chemokine receptors that helped them reach their tumor target tissue and metalloprotease activity that enabled them to invade into tumor tissue. A very large part of the "help" program was instilled in CD8⁺ T cells via CD27 costimulation. The help program thus enhances specific CTL effector functions in response to vaccination or a virus infection.

TCF1+ hepatitis C virus-specific CD8+ T cells are maintained after cessation of chronic antigen stimulation

Differentiation and fate of virus-specific CD8⁺ T cells after cessation of chronic antigen stimulation is unclear. Here we show that a TCF1⁺CD127⁺PD1⁺ hepatitis C virus (HCV)-specific CD8⁺ T-cell subset exists in chronically infected patients with phenotypic features of T-cell exhaustion and memory, both before and after treatment with direct acting antiviral (DAA) agents. This subset is maintained during, and for a long duration after, HCV elimination. After antigen re-challenge the less differentiated TCF1⁺CD127⁺PD1⁺ population expands, which is accompanied by emergence of terminally exhausted TCF1-CD127-PD1^hi HCV-specific CD8⁺ T cells. These results suggest the TCF1⁺CD127⁺PD1⁺ HCV-specific CD8⁺ T-cell subset has memory-like characteristics, including antigen-independent survival and recall proliferation. We thus provide evidence for the establishment of memory-like virus-specific CD8⁺ T cells in a clinically relevant setting of chronic viral infection and we uncover their fate after cessation of chronic antigen stimulation, implicating a potential strategy for antiviral immunotherapy.

IL-15-deficient mice develop enhanced allergic responses to airway allergen exposure

BACKGROUND

Interleukin-15 is a pleiotropic cytokine that is critical for the development and survival of multiple haematopoietic lineages. Mice lacking IL-15 have selective defects in populations of several pro-allergic immune cells including natural killer (NK) cells, NKT cells, and memory CD8+ T cells. We therefore hypothesized that IL-15-/- mice will have reduced inflammatory responses during the development of allergic airway disease (AAD).

OBJECTIVE

To determine whether IL-15-/- mice have attenuated allergic responses in a mouse model of AAD.

METHODS

C57BL/6 wild-type (WT) and IL-15-/- mice were sensitized and challenged with ovalbumin (OVA), and the development of AAD was ascertained by examining changes in airway inflammatory responses, Th2 responses, and lung histopathology.

RESULTS

Here, we report that IL-15-/- mice developed enhanced allergic responses in an OVA-induced model of AAD. In the absence of IL-15, OVA-challenged mice exhibited enhanced bronchial eosinophilic inflammation, elevated IL-13 production, and severe lung histopathology in comparison with WT mice. In addition, increased numbers of CD4+ T and B cells in the spleens and bronchoalveolar lavage (BAL) were also observed. Examination of OVA-challenged IL-15Rα-/- animals revealed a similar phenotype resulting in enhanced airway eosinophilia compared to WT mice. Adoptive transfer of splenic CD8+ T cells from OVA-sensitized WT mice suppressed the enhancement of eosinophilia in IL-15-/- animals to levels observed in WT mice, but had no further effects.

CONCLUSION AND CLINICAL RELEVANCE

These data demonstrate that mice with an endogenous IL-15 deficiency are susceptible to the development of severe, enhanced Th2-mediated AAD, which can be regulated by CD8+ T cells. Furthermore, the development of disease as well as allergen-specific Th2 responses occurs despite deficiencies in several IL-15-dependent cell types including NK, NKT, and γδ T cells, suggesting that these cells or their subsets are dispensable for the induction of AAD in IL-15-deficient mice.

Akt signaling is critical for memory CD8+ T-cell development and tumor immune surveillance

Memory CD8+ T cells confer long-term immunity against tumors, and anticancer vaccines therefore should maximize their generation. Multiple memory CD8+ T-cell subsets with distinct functional and homing characteristics exist, but the signaling pathways that regulate their development are ill defined. Here we examined the role of the serine/threonine kinase Akt in the generation of protective immunity by CD8+ T cells. Akt is known to be activated by the T-cell antigen receptor and the cytokine IL-2, but its role in T-cell immunity in vivo has not been explored. Using CD8+ T cells from pdk1K465E/K465E knockin mice, we found that decreased Akt activity inhibited the survival of T cells during the effector-to-memory cell transition and abolished their differentiation into C-X-C chemokine receptor 3 (CXCR3)loCD43lo effector-like memory cells. Consequently, antitumor immunity by CD8+ T cells that display defective Akt signaling was substantially diminished during the memory phase. Reduced memory T-cell survival and altered memory cell differentiation were associated with up-regulation of the proapoptotic protein Bim and the T-box transcription factor eomesodermin, respectively. These findings suggest an important role for effector-like memory CD8+ T cells in tumor immune surveillance and identify Akt as a key signaling node in the development of protective memory CD8+ T-cell responses.

A phase I study of intratumoral ipilimumab and interleukin-2 in patients with advanced melanoma

PURPOSE

Intratumoral interleukin-2 (IL-2) is effective but does not generate systemic immunity. Intravenous ipilimumab produces durable clinical response in a minority of patients, with potentially severe toxicities. Circulating anti-tumor T cells activated by ipilimumab may differ greatly from tumor-infiltrating lymphocytes activated by intratumoral ipilimumab in phenotypes and functionality. The objective of this study was to primarily assess the safety of intratumoral ipilimumab/IL-2 combination and to obtain data on clinical efficacy.

RESULTS

There was no dose limiting toxicity. While local response of injected lesions was observed in 67% patients (95% CI, 40%-93%), an abscopal response was seen in 89% (95% CI, 68%-100%). The overall response rate and clinical benefit rate by immune-related response criteria (irRC) was 40% (95% CI, 10%-70%) and 50% (95% CI, 19%-81%), respectively. Enhanced systemic immune response was observed in most patients and correlated with clinical responses.

EXPERIMENTAL DESIGN

Twelve patients with unresectable stages III/IV melanoma were enrolled. A standard 3+3 design was employed to assess highest tolerable intratumoral dose of ipilimumab and IL-2 based on toxicity during the first three weeks. Escalated doses of ipilimumab was injected into only one lesion weekly for eight weeks in cohorts of three patients. A fixed dose of IL-2 was injected three times a week into the same lesion for two weeks, followed by two times a week for six weeks.

CONCLUSIONS

Intratumoral injection with the combination of ipilimumab/IL-2 is well tolerated and generates responses in both injected and non-injected lesions in the majority of patients.

IL2Rβ-dependent signals drive terminal exhaustion and suppress memory development during chronic viral infection

Exhaustion of CD8(+) T cells severely impedes the adaptive immune response to chronic viral infections. Despite major advances in our understanding of the molecular regulation of exhaustion, the cytokines that directly control this process during chronicity remain unknown. We demonstrate a direct impact of IL-2 and IL-15, two common gamma-chain-dependent cytokines, on CD8(+) T-cell exhaustion. Common to both cytokine receptors, the IL-2 receptor β (IL2Rβ) chain is selectively maintained on CD8(+) T cells during chronic lymphocytic choriomeningitis virus and hepatitis C virus infections. Its expression correlates with exhaustion severity and identifies terminally exhausted CD8(+) T cells both in mice and humans. Genetic ablation of the IL2Rβ chain on CD8(+) T cells restrains inhibitory receptor induction, in particular 2B4 and Tim-3; precludes terminal differentiation of highly defective PD-1(hi) effectors; and rescues memory T-cell development and responsiveness to IL-7-dependent signals. Together, we ascribe a previously unexpected role to IL-2 and IL-15 as instigators of CD8(+) T-cell exhaustion during chronic viral infection.

Promoting Immune Regulation in Type 1 Diabetes Using Low-Dose Interleukin-2

Dysregulation of the immune system contributes to the breakdown of immune regulation, leading to autoimmune diseases, such as type 1 diabetes (T1D). Current therapies for T1D include daily insulin, due to pancreatic β-cell destruction to maintain blood glucose levels, suppressive immunotherapy to decrease the symptoms associated with autoimmunity, and islet transplantation. Genetic risks for T1D have been linked to IL-2 and IL-2R signaling pathways that lead to the breakdown of self-tolerance mechanisms, primarily through altered regulatory T cell (Treg) function and homeostasis. In attempt to correct such deficits, therapeutic administration of IL-2 at low doses has gained attention due to the capacity to boost Tregs without the unwanted stimulation of effector T cells. Preclinical and clinical studies utilizing low-dose IL-2 have shown promising results to expand Tregs due to their high selective sensitivity to respond to IL-2. These results suggest that low-dose IL-2 therapy represents a new class of immunotherapy for T1D by promoting immune regulation rather than broadly suppressing unwanted and beneficial immune responses.