Characterization of human CD4+EOMES+GzmK+ T-cell subsets unveils an uncoupling of suppressive functions from IL-10-producing capacities

Human CD4+EOMES+ T cells are heterogeneous and contain Th1-cells, Tr1-cells, and CD4+CTL. Tr1- cells and non-classical EOMES+ Th1-cells displayed, respectively, anti- and pro-inflammatory cytokine profiles, but both expressed granzyme-K, produced IFN-γ, and suppressed T-cell proliferation. Diffusion map suggested a progressive CD4+T-cell differentiation from naïve to cytotoxic cells and identified EOMES+Th1-cells as putative Tr1-cell precursors (pre-Tr1).

SARS-COV-2 specific t-cells in patients with thyroid disorders related to COVID-19 are enriched in the thyroid and acquire a tissue-resident memory phenotype

BACKGROUND

SARS-CoV-2 infections have been associated with the onset of thyroid disorders like classic subacute thyroiditis (SAT) or atypical SAT upon severe COVID disease (COV-A-SAT). Little is known about thyroid anti-viral immune responses.

OBJECTIVES

To define the role of T-cells in COV-A-SAT.

METHODS

T-cells from COV-A-SAT patients were analyzed by multi-dimensional flow cytometry, UMAP and DiffusionMap dimensionality reduction and FlowSOM clustering. T-cells from COVID-naïve healthy donors, patients with autoimmune thyroiditis (ATD) and with SAT following COVID vaccination were analyzed as controls. T-cells were analyzed four and eight months post-infection in peripheral blood and in thyroid specimen obtained by ultrasound-guided fine needle aspiration. SARS-COV2-specific T-cells were identified by cytokine production induced by SARS-COV2-derived peptides and with COVID peptide-loaded HLA multimers after HLA haplotyping.

RESULTS

COV-A-SAT was associated with HLA-DRB1*13 and HLA-B*57. COV-A-SAT patients contained activated Th1- and cytotoxic CD4+ and CD8+ effector cells four months post-infection, which acquired a quiescent memory phenotype after eight months. Anti-SARS-CoV-2-specific T-cell responses were readily detectable in peripheral blood four months post-infection, but were reduced after eight months. CD4+ and CD8+ tissue-resident memory cells (TRM) were present in the thyroid, and circulating CXCR3+T-cells identified as their putative precursors. SARS-CoV-2-specific T-cells were enriched in the thyroid, and acquired a TRM phenotype eight months post-infection.

CONCLUSIONS

The association of COV-A-SAT with specific HLA haplotypes suggests a genetic predisposition and a key role for T-cells. COV-A-SAT is characterized by a prolonged systemic anti-viral effector T-cell response and the late generation of COVID-specific TRM in the thyroid target tissue.

DGK α and ζ Activities Control TH1 and TH17 Cell Differentiation

CD4⁺ T helper (T_H) cells are critical for protective adaptive immunity against pathogens, and they also contribute to the pathogenesis of autoimmune diseases. How T_H differentiation is regulated by the TCR's downstream signaling is still poorly understood. We describe here that diacylglycerol kinases (DGKs), which are enzymes that convert diacylglycerol (DAG) to phosphatidic acid, exert differential effects on T_H cell differentiation in a DGK dosage-dependent manner. A deficiency of either DGKα or ζ selectively impaired T_H1 differentiation without obviously affecting T_H2 and T_H17 differentiation. However, simultaneous ablation of both DGKα and ζ promoted T_H1 and T_H17 differentiation in vitro and in vivo, leading to exacerbated airway inflammation. Furthermore, we demonstrate that dysregulation of T_H17 differentiation of DGKα and ζ double-deficient CD4⁺ T cells was, at least in part, caused by increased mTOR complex 1/S6K1 signaling.

Killer-like receptors and GPR56 progressive expression defines cytokine production of human CD4+ memory T cells

All memory T cells mount an accelerated response on antigen reencounter, but significant functional heterogeneity is present within the respective memory T-cell subsets as defined by CCR7 and CD45RA expression, thereby warranting further stratification. Here we show that several surface markers, including KLRB1, KLRG1, GPR56, and KLRF1, help define low, high, or exhausted cytokine producers within human peripheral and intrahepatic CD4⁺ memory T-cell populations. Highest simultaneous production of TNF and IFN-γ is observed in KLRB1⁺KLRG1⁺GPR56⁺ CD4 T cells. By contrast, KLRF1 expression is associated with T-cell exhaustion and reduced TNF/IFN-γ production. Lastly, TCRβ repertoire analysis and in vitro differentiation support a regulated, progressive expression for these markers during CD4⁺ memory T-cell differentiation. Our results thus help refine the classification of human memory T cells to provide insights on inflammatory disease progression and immunotherapy development.

Despite the current human CD4 memory T cell stratification by CD45RA/CCR7, functional heterogeneities still exist within the respective subsets. Here the authors show that several surface markers, including KLRB1, KLRG1, GPR56 and KLRF1, help to further refine the subsetting of human CD4 memory T cells and provide insights for their differentiation.

Phenotype and specificity of T cells in primary human cytomegalovirus infection during pregnancy: IL-7Rpos long-term memory phenotype is associated with protection from vertical transmission

Congenital human cytomegalovirus (HCMV) infection is the major cause of birth defects and a precise definition of the HCMV-specific T-cell response in primary infection may help define reliable correlates of immune protection during pregnancy. In this study, a high throughput method was used to define the frequency of CD4⁺ and CD8⁺ T cells specific for four HCMV proteins in the naïve compartment of seronegative subjects and the effector/memory compartments of subjects with primary/remote HCMV infection. The naïve repertoire displayed comparable frequencies of T cells that were reactive with HCMV structural (pp65, gB and the pentamer gHgLpUL128L) and non-structural (IE-1) proteins. Whereas, following natural infection, the majority of effector/memory CD4⁺ and CD8⁺ T cells recognized either gB or IE-1, respectively, and pp65. The pattern of T cell reactivity was comparable at early and late stages of infection and in pregnant women with primary HCMV infection transmitting or not transmitting the virus to the fetus. At an early stage of primary infection, about 50% of HCMV-reactive CD4⁺ T cells were long-term IL-7R^pos memory cells, while 6–12 months later, the frequency of these cells increased to 70%, approaching 100% in remote infections. In contrast, only 10–20% of HCMV-specific CD8⁺ T cells were long-term memory cells up to 12 months after infection onset, thereafter increasing to 70% in remote infections. Interestingly, a significantly higher frequency of HCMV-specific CD4⁺ T cells with a long-term IL-7R^pos memory phenotype was observed in non-transmitting compared to transmitting women. These findings indicate that immunodominance in HCMV infection is not predetermined in the naïve compartment, but is the result of virus-host interactions and suggest that prompt control of HCMV infection in pregnancy is associated with the rapid development of long-term IL-7R^pos memory HCMV-specific CD4⁺ T cells and a low risk of virus transmission to the fetus.

Thy-1 stimulation of mouse T cells induces a delayed T cell receptor-like signal that results in Ca2+‑independent cytotoxicity

Antibody-mediated crosslinking of Thy-1 [also known as cluster of differentiation (CD)90], results in a T cell receptor (TcR)‑like signal; however, the impact of Thy‑1 stimulation in comparison to TcR stimulation on T cell activation and effector function has yet to be fully elucidated. In the present study, the outcome of Thy‑1‑ and TcR‑induced stimulation of T cells was investigated in mice, using fragment crystalizable (Fc) receptor‑bound antibodies and costimulatory signals provided by syngeneic lipopolysaccharide‑matured bone marrow‑derived dendritic cells. Compared with TcR signaling, Thy‑1 signaling initiated a less robust proliferative response in T cells, as determined by tritiated‑thymidine incorporation. In addition, enzyme‑linked immunosorbent assays revealed that interleukin‑2 production was reduced, and the expression of CD25 and cyclin D3 was weaker in Thy‑1‑stimulated cells, as determined by western blotting; however, the expression of cyclin‑dependent kinase 6 was similar to that in TcR‑induced T cells. Furthermore, western blotting demonstrated that the phosphorylation of ζ-chain‑associated protein kinase 70 and extracellular signal‑regulated kinase 1/2 was delayed following Thy‑1 stimulation. DNA fragmentation assays revealed that cytotoxic effector function was also slower to develop in Thy‑1‑stimulated T cells, required more time to be effective and was largely Ca2+‑independent; these findings suggested that Fas ligand rather than granule‑associated perforin was involved in T cell effector function. In conclusion, the present results suggested that Thy‑1 signaling may contribute to the regulation of T cell homeostasis and the development of non‑specific T cell‑mediated cytotoxicity. However, further studies are required to elucidate the exact physiological roles of TcR‑like signals that result from Thy‑1 crosslinking and to investigate the molecular mechanisms that are involved.

Increased IL-15 Production and Accumulation of Highly Differentiated CD8+ Effector/Memory T Cells in the Bone Marrow of Persons with Cytomegalovirus

Cytomegalovirus (CMV) has been described as a contributor to immunosenescence, thus exacerbating age-related diseases. In persons with latent CMV infection, the CD8⁺ T cell compartment is irreversibly changed, leading to the accumulation of highly differentiated virus-specific CD8⁺ T cells in the peripheral blood. The bone marrow (BM) has been shown to play a major role in the long-term survival of antigen-experienced T cells. Effector CD8⁺ T cells are preferentially maintained by the cytokine IL-15, the expression of which increases in old age. However, the impact of CMV on the phenotype of effector CD8⁺ T cells and on the production of T cell survival molecules in the BM is not yet known. We now show, using BM samples obtained from persons who underwent hip replacement surgery because of osteoarthrosis, that senescent CD8⁺ T_EMRA cells with a bright expression of CD45RA and a high responsiveness to IL-15 accumulate in the BM of CMV-infected persons. A negative correlation was found between CMV antibody (Ab) titers in the serum and the expression of CD28 and IL-7Rα in CD8⁺ [Formula: see text] cells. Increased IL-15 mRNA levels were observed in the BM of CMV⁺ compared to CMV^- persons, being particularly high in old seropositive individuals. In summary, our results indicate that a BM environment rich in IL-15 may play an important role in the maintenance of highly differentiated CD8⁺ T cells generated after CMV infection.

A transcriptome-based model of central memory CD4 T cell death in HIV infection

BACKGROUND

Human central memory CD4 T cells are characterized by their capacity of proliferation and differentiation into effector memory CD4 T cells. Homeostasis of central memory CD4 T cells is considered a key factor sustaining the asymptomatic stage of Human Immunodeficiency Virus type 1 (HIV-1) infection, while progression to acquired immunodeficiency syndrome is imputed to central memory CD4 T cells homeostatic failure. We investigated if central memory CD4 T cells from patients with HIV-1 infection have a gene expression profile impeding proliferation and survival, despite their activated state.

METHODS

Using gene expression microarrays, we analyzed mRNA expression patterns in naive, central memory, and effector memory CD4 T cells from healthy controls, and naive and central memory CD4 T cells from patients with HIV-1 infection. Differentially expressed genes, defined by Log₂ Fold Change (FC) ≥ |0.5| and Log (odds) > 0, were used in pathway enrichment analyses.

RESULTS

Central memory CD4 T cells from patients and controls showed comparable expression of differentiation-related genes, ruling out an effector-like differentiation of central memory CD4 T cells in HIV infection. However, 210 genes were differentially expressed in central memory CD4 T cells from patients compared with those from controls. Expression of 75 of these genes was validated by semi quantitative RT-PCR, and independently reproduced enrichment results from this gene expression signature. The results of functional enrichment analysis indicated movement to cell cycle phases G1 and S (increased CCNE1, MKI67, IL12RB2, ADAM9, decreased FGF9, etc.), but also arrest in G2/M (increased CHK1, RBBP8, KIF11, etc.). Unexpectedly, the results also suggested decreased apoptosis (increased CSTA, NFKBIA, decreased RNASEL, etc.). Results also suggested increased IL-1β, IFN-γ, TNF, and RANTES (CCR5) activity upstream of the central memory CD4 T cells signature, consistent with the demonstrated milieu in HIV infection.

CONCLUSIONS

Our findings support a model where progressive loss of central memory CD4 T cells in chronic HIV-1 infection is driven by increased cell cycle entry followed by mitotic arrest, leading to a non-apoptotic death pathway without actual proliferation, possibly contributing to increased turnover.

IL-10 promotes homeostatic proliferation of human CD8(+) memory T cells and, when produced by CD1c(+) DCs, shapes naive CD8(+) T-cell priming

IL-10 is an anti-inflammatory cytokine that inhibits maturation and cytokine production of dendritic cells (DCs). Although mature DCs have the unique capacity to prime CD8(+) CTL, IL-10 can promote CTL responses. To understand these paradoxic findings, we analyzed the role of IL-10 produced by human APC subsets in T-cell responses. IL-10 production was restricted to CD1c(+) DCs and CD14(+) monocytes. Interestingly, it was differentially regulated, since R848 induced IL-10 in DCs, but inhibited IL-10 in monocytes. Autocrine IL-10 had only a weak inhibitory effect on DC maturation, cytokine production, and CTL priming with high-affinity peptides. Nevertheless, it completely blocked cross-priming and priming with low-affinity peptides of a self/tumor-antigen. IL-10 also inhibited CD1c(+) DC-induced CD4(+) T-cell priming and enhanced Foxp3 induction, but was insufficient to induce T-cell IL-10 production. CD1c(+) DC-derived IL-10 had also no effect on DC-induced secondary expansions of memory CTL. However, IL-15-driven, TCR-independent proliferation of memory CTL was enhanced by IL-10. We conclude that DC-derived IL-10 selects high-affinity CTL upon priming. Moreover, IL-10 preserves established CTL memory by enhancing IL-15-dependent homeostatic proliferation. These combined effects on CTL priming and memory maintenance provide a plausible mechanism how IL-10 promotes CTL responses in humans.

Signal Strength and Metabolic Requirements Control Cytokine-Induced Th17 Differentiation of Uncommitted Human T Cells

IL-17 production defines Th17 cells, which orchestrate immune responses and autoimmune diseases. Human Th17 cells can be efficiently generated with appropriate cytokines from precommitted precursors, but the requirements of uncommitted T cells are still ill defined. In standard human Th17 cultures, IL-17 production was restricted to CCR6(+)CD45RA(+) T cells, which expressed CD95 and produced IL-17 ex vivo, identifying them as Th17 memory stem cells. Uncommitted naive CD4(+) T cells upregulated CCR6, RORC2, and IL-23R expression with Th17-promoting cytokines but in addition required sustained TCR stimulation, late mammalian target of rapamycin (mTOR) activity, and HIF-1α to produce IL-17. However, in standard high-density cultures, nutrients like glucose and amino acids became progressively limiting, and mTOR activity was consequently not sustained, despite ongoing TCR stimulation and T cell proliferation. Sustained, nutrient-dependent mTOR activity also induced spontaneous IL-22 and IFN-γ production, but these cytokines had also unique metabolic requirements. Thus, glucose promoted IL-12-independent Th1 differentiation, whereas aromatic amino acid-derived AHR ligands were selectively required for IL-22 production. The identification of Th17 memory stem cells and the stimulation requirements for induced human Th17/22 differentiation have important implications for T cell biology and for therapies targeting the mTOR pathway.

Effector CD8+ T-cell Engraftment and Antitumor Immunity in Lymphodepleted Hosts Is IL7Rα Dependent

Adoptive cellular therapy, in which activated tumor-reactive T cells are transferred into lymphodepleted recipients, is a promising cancer treatment option. Activation of T cells decreases IL7 responsiveness; therefore, IL15 is generally considered the main driver of effector T-cell responses in this setting. However, we found in lymphodepleted mice that CD8(+) T cells activated with IL12 showed enhanced engraftment that was initially dependent on host IL7, but not IL15. Mechanistically, enhanced IL7 responsiveness was conferred by elevated IL7Rα expression, which was critical for antitumor immunity. Elevated IL7Rα expression was achievable without IL12, as polyclonal CD8(+) T cells activated with high T-cell receptor (TCR) stimulation depended on T-cell IL7Rα expression and host IL7 for maximal engraftment. Finally, IL12 conditioning during the activation of human CD8(+) T cells, including TCR-modified T cells generated using a clinically relevant protocol, led to enhanced IL7Rα expression. Our results demonstrate the importance of the donor IL7Rα/host IL7 axis for effector CD8(+) T-cell engraftment and suggest novel strategies to improve adoptive cellular therapy as a cancer treatment.

CD4+ T cell STAT3 phosphorylation precedes acute GVHD, and subsequent Th17 tissue invasion correlates with GVHD severity and therapeutic response

Th17 cells contribute to severe GVHD in murine bone marrow transplantation. Targeted deletion of the RORγt transcription factor or blockade of the JAK2-STAT3 axis suppresses IL-17 production and alloreactivity by Th17 cells. Here, we show that pSTAT3 Y705 is increased significantly in CD4(+) T cells among human recipients of allogeneic HCT before the onset of Grade II-IV acute GVHD. Examination of target-organ tissues at the time of GVHD diagnosis indicates that the amount of RORγt + Th17 cells is significantly higher in severe GVHD. Greater accumulation of tissue-resident Th17 cells also correlates with the use of MTX- compared with Rapa-based GVHD prophylaxis, as well as a poor therapeutic response to glucocorticoids. RORγt is optimally suppressed by concurrent neutralization of TORC1 with Rapa and inhibition of STAT3 activation with S3I-201, supporting that mTOR- and STAT3-dependent pathways converge upon RORγt gene expression. Rapa-resistant T cell proliferation can be totally inhibited by STAT3 blockade during initial allosensitization. We conclude that STAT3 signaling and resultant Th17 tissue accumulation are closely associated with acute GVHD onset, severity, and treatment outcome. Future studies are needed to validate the association of STAT3 activity in acute GVHD. Novel GVHD prevention strategies that incorporate dual STAT3 and mTOR inhibition merit investigation.

Cytomegalovirus-specific responses of CD38⁺ memory T cells are skewed towards IFN-γ and dissociated from CD154 in HIV-1 infection

OBJECTIVE

Despite the strong correlation of T-cell CD38 expression with HIV disease progression, evidence linking CD38 expression and dysfunction at the single cell level is scant. Since CD38⁺ memory CD4⁺ T cells, especially those from HIV-infected persons, fail to induce CD154 (CD40L) while responding to a superantigen with interferon (IFN)-γ or interleukin (IL)-2, we aimed to determine if recall responses to cytomegalovirus (CMV) were similarly affected in the CD38⁺ memory CD4⁺ T-cell subpopulation.

DESIGN AND METHODS

Peripheral blood mononuclear cells from HIV+ patients and healthy controls were incubated 14 h with CMV antigens, the superantigen Staphylococcus aureus enterotoxin B or medium, and labeled for identification of central memory (T(CM)) and effector memory (T(EM)) CD4⁺ T cells, and for the intracellular detection of induced CD154, IFN-γ and/or IL-2 by flow cytometry.

RESULTS

Compared with CD38⁻ cells, CD38⁺ T(CM) cells from patients had less CD40L induction after CMV stimulation, and increased IFN-γ response. Patients' CD38⁺ T(EM) cells showed a lower IL-2 response, and tended to have a greater IFN-γ response, in which CD154 induction frequently failed. CMV-specific responses of patients' CD38⁺ T(CM) and T(EM) cells were dominated by IFN-γ, and almost all IL-2⁺ cells co-expressed IFN-γ. IL-2 responses to the polyclonal activator S. aureus enterotoxin B were also significantly less frequent among CD38⁺ T(CM) and T(EM) cells than in CD38⁻ cells.

CONCLUSION

Patients' CD38⁺ memory CD4⁺T-cell responses to CMV favor the effector cytokine IFN-γ over IL-2, in the context of deficient CD154 induction, which may limit co-stimulation, proliferation and survival.

Human CD4(+) effector T lymphocytes generated upon TCR engagement with self-peptides respond defectively to IL-7 in their transition to memory cells

The peripheral repertoire of CD4(+) T lymphocytes contains autoreactive cells that remain tolerant through several mechanisms. However, nonspecific CD4(+) T cells can be activated in physiological conditions as in the course of an ongoing immune response, and their outcome is not yet fully understood. Here, we investigate the fate of human naive CD4(+) lymphocytes activated by dendritic cells (DCs) presenting endogenous self-peptides in comparison with lymphocytes involved in alloresponses. We generated memory cells (Tmem) from primary effectors activated with mature autologous DCs plus interleukin (IL)-2 (Tmauto), simulating the circumstances of an active immune response, or allogeneic DCs (Tmallo). Tmem were generated from effector cells that were rested in the absence of antigenic stimuli, with or without IL-7. Tmem were less activated than effectors (demonstrated by CD25 downregulation) particularly with IL-7, suggesting that this cytokine may favour the transition to quiescence. Tmauto and Tmallo showed an effector memory phenotype, and responded similarly to polyclonal and antigen-specific stimuli. Biochemically, IL-7-treated Tmallo were closely related to conventional memory lymphocytes based on Erk-1/2 activation, whereas Tmauto were more similar to effectors. Autologous effectors exhibited lower responses to IL-7 than allogeneic cells, which were reflected in their reduced proliferation and higher cell death. This was not related to IL-7 receptor expression but rather to signalling deficiencies, according to STAT5 activation These results suggest that ineffective responses to IL-7 could impair the transition to memory cells of naive CD4(+) T lymphocytes recognizing self-peptides in the setting of strong costimulation.

Plasma levels of IL-7 and IL-15 after reduced intensity conditioned allo-SCT and relationship to acute GVHD

To assess the impact of homeostatic expansion on the occurrence of acute GVHD after reduced intensity conditioning (RIC) transplantation, systemic levels of IL-7 and IL-15 and expression of their specific receptor chains were prospectively investigated in 45 fully HLA-matched allograft recipients. IL-7 and IL-15 levels peaked at four- to fivefold over pre-conditioning values. IL-7 levels were inversely correlated to absolute T-cell counts. Peak IL-15 levels positively correlated to concurrent CRP levels, but normalized earlier than IL-7. These results indicate that the kinetic course of IL-7 depends mainly on initiation of T-cell recovery, while IL-15 depends more on peri-transplant inflammation after RIC. Longer duration of the rise in IL-7 levels was associated with preservation of a normal CD4/CD8 ratio. In all, 16 (35%) patients developed grade 2-4 acute GVHD at a median of 42 days post graft, preceded by higher IL-7 levels and more downregulation of IL-7 receptor α chain on CD4(+) T cells than in patients without acute GVHD, suggesting enhanced homeostatic expansion. In multivariate analysis, IL-7 level measured on day +30 was the foremost predictive factor for grade 2-4 acute GVHD (P=0.002). Measurement of IL-7 level after RIC transplantation might help predict risk of subsequent acute GvHD.

Epitope density influences CD8+ memory T cell differentiation

Background

The generation of long-lived memory T cells is critical for successful vaccination but the factors controlling their differentiation are still poorly defined. We tested the hypothesis that the strength of T cell receptor (TCR) signaling contributed to memory CD8⁺ T cell generation.

Methodology/Principal Findings

We manipulated the density of antigenic epitope presented by dendritic cells to mouse naïve CD8⁺ T cells, without varying TCR affinity. Our results show that a two-fold decrease in antigen dose selectively affects memory CD8⁺ T cell generation without influencing T cell expansion and acquisition of effector functions. Moreover, we show that low antigen dose alters the duration of the interaction between T cells and dendritic cells and finely tunes the expression level of the transcription factors Eomes and Bcl6. Furthermore, we demonstrate that priming with higher epitope density results in a 2-fold decrease in the expression of Neuron-derived orphan nuclear receptor 1 (Nor-1) and this correlates with a lower level of conversion of Bcl-2 into a pro-apoptotic molecule and an increased number of memory T cells.

Conclusions

Our results show that the amount of antigen encountered by naïve CD8⁺ T cells following immunization with dendritic cells does not influence the generation of functional effector CD8⁺ T cells but rather the number of CD8⁺ memory T cells that persist in the host. Our data support a model where antigenic epitope density sensed by CD8⁺ T cells at priming influences memory generation by modulating Bcl6, Eomes and Nor-1 expression.

Low-strength T-cell activation promotes Th17 responses

We show that the strength of T-cell stimulation determines the capability of human CD4(+) T cells to become interleukin-17 (IL-17) producers. CD4(+) T cells received either high- (THi) or low (TLo)-strength stimulation via anti-CD3/CD28 beads or dendritic cells pulsed with superantigen in the presence of pro-Th17 cytokines IL-1β, transforming growth factor β, and IL-23. We found that TLo, but not THi, stimulation profoundly promoted Th17 responses by enhancing both the relative proportion and total number of Th17 cells. Titration of anti-CD3 revealed that low TCR signaling promoted Th17 cells, but only in the presence of anti-CD28. Impaired IL-17 production in THi cells could not be explained by high levels of Foxp3 or transforming growth factor β-latency-associated peptide expressed by THi cells. Nuclear factor of activated T cells was translocated to the nucleus in both THi and TLo cells, but only bound to the proximal region of the IL-17 promoter in TLo cells. The addition of a Ca(2+) ionophore under TLo conditions reversed the pro-Th17 effect, suggesting that high Ca(2+) signaling impairs Th17 development. Although our data do not distinguish between priming of naive T cells versus expansion/differentiation of memory T cells, our results clearly establish an important role for the strength of T-cell activation in regulating Th17 responses.

Plasma levels of IL-7 and IL-15 in the first month after myeloablative BMT are predictive biomarkers of both acute GVHD and relapse

T-cell reconstitution after allo-SCT initially depends on homeostatic peripheral expansion of donor T cells, the level of which may promote the differentiation of alloreactive and tumor-reactive effectors. IL-7 and IL-15 exert their effect as key homeostatic cytokines. We prospectively investigated plasma levels of IL-7 and IL-15 in a homogeneous group of 40 patients in CR of their hematologic malignancy undergoing myeloablative, fully (10/10) HLA-matched BMT. IL-7 and IL-15 proceeded along similar kinetic courses, peaking at wide ranges (3.8-30.2 and 14.3-66 pg/ml, respectively) on day +14 when all patients were profoundly lymphopenic. Occurrence and grade of subsequent acute GVHD were significantly associated with heightened day +14 IL-7 and IL-15 levels. Association of peak IL-7 level to grade 2-4 acute GVHD was confirmed by Cox multivariate analysis (hazard ratio (HR)=5.38; P=0.022). Malignancy relapse was significantly associated with reduced day +14 levels of IL-15 (Cox multivariate analysis: HR=0.93; P=0.035). Plasma IL-7 and IL-15 levels in the early post transplantation period are therefore biomarkers that can help predict subsequent development of acute GVHD and malignancy relapse.

Memories that last forever: strategies for optimizing vaccine T-cell memory

For acute self-limiting infections a vaccine is successful if it elicits memory at least as good as the natural experience; however, for persistent and chronic infections such as HIV, hepatitis C virus (HCV), human papillomavirus (HPV), and human herpes viruses, this paradigm is not applicable. At best, during persistent virus infection the person must be able to maintain the integrity of the immune system in equilibrium with controlling replicating virus. New vaccine strategies are required that elicit both potent high-avidity CD8(+) T-cell effector/memory and central memory responses that can clear the nidus of initial virus-infected cells at mucosal surfaces to prevent mucosal transmission or significantly curtail development of disease. The objective of an HIV-1 T-cell vaccine is to generate functional CD8(+) effector memory cells at mucosal portals of virus entry to prevent viral transmission. In addition, long-lived CD8(+) and CD4(+) central memory cells circulating through secondary lymphoid organs and resident in bone marrow, respectively, are needed to provide a concerted second wave of defense that can contain virus at mucosal surfaces and prevent systemic dissemination. Further understanding of factors which can influence long-lived effector and central memory cell differentiation will significantly contribute to development of effective T-cell vaccines. In this review we will focus on discussing mechanisms involved in T-cell memory and provide promising new approaches toward expanding current vaccine strategies to enhance antiviral memory.

Identification and characterization of IL-10/IFN-gamma-producing effector-like T cells with regulatory function in human blood

Two subsets of natural and adaptive regulatory T (T reg) cells have been described, but the identity of adaptive type 1 regulatory (Tr1)–like cells in humans is unclear. We analyzed a subset of human blood CD4⁺ T cells—CD45RA⁻CD25⁻interleukin (IL)-7 receptor (R)⁻ cells—that rapidly secreted high levels of IL-10 together with interferon γ, but produced little IL-2. These IL-7R⁻ T cells were rare, anergic, and largely Foxp3⁻. They expressed low levels of Bcl-2 but high levels of Ki-67 and ICOS, suggesting that they have been recently activated in vivo. Consistently, they responded selectively to persistent foreign and self-antigens under steady-state conditions. Unlike natural CD25⁺ T reg cells, IL-7R⁻ cells suppressed naive and memory T cell proliferation in an IL-10–dependent fashion, and they required strong T cell receptor stimulation for suppression. To our knowledge, this is the first report that identifies Tr1-like cells in human blood. These IL-10–secreting cells have characteristics of chronically activated Th1 effector cells and are distinct from CD25⁺ T reg cells.

The central memory CD4+ T cell population generated during Leishmania major infection requires IL-12 to produce IFN-gamma

Central memory CD4(+) T cells provide a pool of lymph node-homing, Ag-experienced cells that are capable of responding rapidly after a secondary infection. We have previously described a population of central memory CD4(+) T cells in Leishmania major-infected mice that were capable of mediating immunity to a secondary infection. In this study, we show that the Leishmania-specific central memory CD4(+) T cells require IL-12 to produce IFN-gamma, demonstrating that this population needs additional signals to develop into Th1 cells. In contrast, effector cells isolated from immune mice produced IFN-gamma in vitro or in vivo in the absence of IL-12. In addition, we found that when central memory CD4(+) T cells were adoptively transferred into IL-12-deficient hosts, many of the cells became IL-4 producers. These studies indicate that the central memory CD4(+) T cell population generated during L. major infection is capable of developing into either Th1 or Th2 effectors. Thus, continued IL-12 production may be required to ensure the development of Th1 cells from this central memory T cell pool, a finding that has direct relevance to the design of vaccines dependent upon central memory CD4(+) T cells.

Heterogeneous memory T cells in antiviral immunity and immunopathology

Memory T cells are generated following an initial viral infection, and have the potential for mediating robust protective immunity to viral re-challenge due to their rapid and enhanced functional responses. In recent years, it has become clear that the memory T cell response to most viruses is remarkably diverse in phenotype, function, and tissue distribution, and can undergo dynamic changes during its long-term maintenance in vivo. However, the role of this variegation and compartmentalizationof memory T cells in protective immunity to viruses remains unclear. In this review,we discuss the diverse features of memory T cells that can delineate different subsets, the characteristics of memory T cells thus far identified to promote protective immune responses, and how the heterogeneous nature of memory T cells may also promote immunopathology during antiviral responses. We propose that given the profound heterogeneity of memory T cells, regulation of memory T cells during secondary responses could focus the response to participation of specific subsets,and/or inhibit memory T-cell subsets and functions that can lead to immunopathology.

Phase I study of bortezomib with weekly paclitaxel in patients with advanced solid tumours

BACKGROUND

The combination of a proteasome inhibitor with a taxane has potential clinical synergism that prompted a clinical test.

PATIENTS AND METHODS

The maximum tolerated dose (MTD) and recommended dose (RD) of intravenous (i.v.) Bortezomib (B) (days 1, 4, 8, 11) and i.v. Paclitaxel (PTX) (days 1, 8) every 3 weeks was evaluated in patients with advanced solid tumours. The RD was tested in patients with breast, ovarian and prostate cancer. At the RD, microarray analysis of transcriptional profiles was carried out before and after the first dosing in peripheral blood mononuclear cells (PBMC).

RESULTS

Thirty-one patients were enrolled and 22 were treated at the RD that corresponded to B 1.3mg/m(2) and PTX 100mg/m(2). The main toxicity was cumulative peripheral neuropathy (76% of patients; grade 3-4 in 9%) that required treatment discontinuation in six patients, followed by diarrhoea (55%) and fatigue (41%). Nine partial responses (30%) were observed (three breast cancer, four ovary, two prostate patients). Significant (p<0.05) and consistent changes (>70% of patients) in transcriptome were observed.

CONCLUSIONS

The incidence of peripheral neuropathy and the anti-tumour activity comparable to that of single-agent PTX do not support further development of this regimen.

Fine-tuning CD4+ central memory T cell heterogeneity by strength of stimulation

The memory T cell pool serves as a relatively long-lived heterogeneous repository of antigen-experienced T cells that "remember" previous encounters with antigen. While heterogeneity in the memory T cell pool is now well established, signals regulating the generation of this memory T cell heterogeneity are not fully understood. Two articles in this issue of the European Journal of Immunology highlight the importance of the strength of antigenic stimulation in regulating the generation of phenotypically and functionally distinct CD4(+) T cell memory subsets. New insights are also provided into key molecular players that likely mediate differences in homeostatic and secondary expansion between the memory subsets.