Multidimensional scaling analysis identifies pathological and prognostically relevant profiles of circulating T-cells in chronic lymphocytic leukemia

CD20+ T cells in monoclonal B cell lymphocytosis and chronic lymphocytic leukemia: frequency, phenotype and association with disease progression

Introduction

In monoclonal B cell lymphocytosis (MBL) and chronic lymphocytic leukemia (CLL), the expansion of malignant B cells disrupts the normal homeostasis and interactions between B cells and T cells, leading to immune dysregulation. CD20+ T cells are a subpopulation of T cells that appear to be involved in autoimmune diseases and cancer.

Methods

Here, we quantified and phenotypically characterized CD20+ T cells from MBL subjects and CLL patients using flow cytometry and correlated our findings with the B-cell receptor mutational status and other features of the disease.

Results and discussion

CD20+ T cells were more represented within the CD8+ T cell compartment and they showed a predominant memory Tc1 phenotype. CD20+ T cells were less represented in MBL and CLL patients vs healthy controls, particularly among those with unmutated IGVH gene. The expansion of malignant B cells was accompanied by phenotypic and functional changes in CD20+ T cells, including an increase in follicular helper CD4+ CD20+ T cells and CD20+ Tc1 cells, in addition to the expansion of the TCR Vβ 5.1 in CD4+ CD20+ T cells in CLL.

In chronic lymphocytic leukemia, activation of the thrombopoietin receptor promotes T-cell inhibitory properties, contributing to immunosuppression

In chronic lymphocytic leukemia (CLL), the immune system is skewed towards a suppressive milieu. Levels of thrombopoietin (TPO), promoting cellular immune regulatory activity in immune thrombocytopenic purpura, were shown to be elevated in CLL patients. This study explored TPO as a potential immunomodulator, supporting CLL progression. We evaluated CLL cell-induced expression of TPO receptor (TPO-R) on T-cells and effects of its activation on T-cell responses. CLL cell involvement in TPO generation was also assessed. Baseline TPO-R expression on CD4 + T-cells was found to be higher in CLL patients than in healthy controls (HC). Exposure of HC-T-cells to B-cells, especially to CLL-B-cells stimulated with B-cell activating molecules, resulted in enhanced TPO-R expression on T-cells. CLL-T-cell stimulation with TPO reduced their proliferation and expanded the regulatory T-cell (Treg) population. At baseline, phosphorylation of STAT5, known to impact the Treg phenotype, was elevated in CLL-T-cells relative to those of HC. Exposure to TPO further enhanced STAT5 phosphorylation in CLL-T-cells, possibly driving the observed Treg expansion. The CLL immune milieu is involved in promotion of inhibitory features in T-cells through increased TPO-R levels and TPO-induced intracellular signaling. TPO and its signaling pathway could potentially support immunosuppression in CLL, and may emerge as novel therapeutic targets.

A comprehensive assessment of lymphocyte subsets, their prognostic significance, and changes after first‐line therapy administration in patients with chronic lymphocytic leukemia

BACKGROUND

In chronic lymphocytic leukemia (CLL), changes in the peripheral blood lymphocyte subsets play an important role in disease progression and infectious complications. The impact of chemoimmunotherapy (CIT) on these changes has not been extensively studied METHODS: We used multi-color flow cytometry, to prospectively measure absolute and relative numbers of CD4⁺ and CD8⁺ T-cells and their subsets in 45 patients with indolent untreated CLL, 86 patients indicated for first-line treatment, and 34 healthy controls. In 55 patients, we analyzed the impact of CIT RESULTS: CLL patients had a significant increase in most cell populations in comparison to controls. Progression of CLL was characterized by significantly elevated counts with the exception of a lower percentage of naïve T-cells. After treatment, the percentage of naïve T-cells further decreased at the expense of effector memory T-cells (TEM). In patients with indolent CLL, higher percentages of naïve CD4⁺ (p = 0.0026) and naïve CD8⁺ (p = 0.023) T-cells were associated with a longer time to first treatment (TTFT). The elevation of CD4⁺ central memory T-cells (TCM) (p = 0.27) and TEM (p = 0.003) counts and a higher percentage of CD4⁺ TEM (p = 0.0047), were linked with shorter TTFT. In treated patients, increased regulatory T-cells count was associated with shorter time to next treatment (TTNT) (p = 0.042), while higher CD4⁺ TCM count with shorter TTNT (p = 0.035) and shorter overall survival (p = 0.041).

CONCLUSION

Our results indicate that naïve cell depletion and CD4⁺ TCM and TEM increases are detrimental to CLL patients' prognosis.

Effects of ibrutinib on T-cell immunity in patients with chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL), a highly heterogeneous B-cell malignancy, is characterized by tumor microenvironment disorder and T-cell immune dysfunction, which play a major role in the proliferation and survival of CLL cells. Ibrutinib is the first irreversible inhibitor of Bruton’s tyrosine kinase (BTK). In addition to targeting B-cell receptor (BCR) signaling to kill tumor cells, increasing evidence has suggested that ibrutinib regulates the tumor microenvironment and T-cell immunity in a direct and indirect manner. For example, ibrutinib not only reverses the tumor microenvironment by blocking cytokine networks and toll-like receptor signaling but also regulates T cells in number, subset distribution, T-cell receptor (TCR) repertoire and immune function by inhibiting interleukin-2 inducible T-cell kinase (ITK) and reducing the expression of inhibitory receptors, and so on. In this review, we summarize the current evidence for the effects of ibrutinib on the tumor microenvironment and cellular immunity of patients with CLL, particularly for the behavior and function of T cells, explore its potential mechanisms, and provide a basis for the clinical benefits of long-term ibrutinib treatment and combined therapy based on T-cell-based immunotherapies.

Impact of Immune Parameters and Immune Dysfunctions on the Prognosis of Patients with Chronic Lymphocytic Leukemia

Simple Summary

In chronic lymphocytic leukemia (CLL), immune alterations—affecting both the innate and adaptive immunity—are very common. As a clinical consequence, patients with CLL frequently present with autoimmune phenomena, increased risk of infections and second malignancies. The aim of this review article is to present available data on CLL-associated alterations of immune parameters that correlate with known prognostic markers and with clinical outcome. Also, data on the impact of immune-related clinical manifestations on the prognosis of patients with CLL will be discussed.

Abstract

Chronic lymphocytic leukemia (CLL) is characterized by a wide spectrum of immune alterations, affecting both the innate and adaptive immunity. These immune dysfunctions strongly impact the immune surveillance, facilitate tumor progression and eventually affect the disease course. Quantitative and functional alterations involving conventional T cells, γδ T cells, regulatory T cells, NK and NKT cells, and myeloid cells, together with hypogammaglobulinemia, aberrations in the complement pathways and altered cytokine signature have been reported in patients with CLL. Some of these immune parameters have been shown to associate with other CLL-related characteristics with a known prognostic relevance or to correlate with disease prognosis. Also, in CLL, the complex immune response dysfunctions eventually translate in clinical manifestations, including autoimmune phenomena, increased risk of infections and second malignancies. These clinical issues are overall the most common complications that affect the course and management of CLL, and they also may impact overall disease prognosis.

Targeting CD38 is lethal to Breg-like chronic lymphocytic leukemia cells and Tregs, but restores CD8+ T-cell responses

Patients with chronic lymphocytic leukemia (CLL) are characterized by monoclonal expansion of CD5+CD23+CD27+CD19+κ/λ+ B lymphocytes and are clinically noted to have profound immune suppression. In these patients, it has been recently shown that a subset of B cells possesses regulatory functions and secretes high levels of interleukin 10 (IL-10). Our investigation identified that CLL cells with a CD19+CD24+CD38hi immunophenotype (B regulatory cell [Breg]-like CLL cells) produce high amounts of IL-10 and transforming growth factor β (TGF-β) and are capable of transforming naive T helper cells into CD4+CD25+FoxP3+ T regulatory cells (Tregs) in an IL-10/TGF-β-dependent manner. A strong correlation between the percentage of CD38+ CLL cells and Tregs was observed. CD38hi Tregs comprised more than 50% of Tregs in peripheral blood mononuclear cells (PBMCs) in patients with CLL. Anti-CD38 targeting agents resulted in lethality of both Breg-like CLL and Treg cells via apoptosis. Ex vivo, use of anti-CD38 monoclonal antibody (mAb) therapy was associated with a reduction in IL-10 and CLL patient-derived Tregs, but an increase in interferon-γ and proliferation of cytotoxic CD8+ T cells with an activated phenotype, which showed an improved ability to lyse patient-autologous CLL cells. Finally, effects of anti-CD38 mAb therapy were validated in a CLL-patient-derived xenograft model in vivo, which showed decreased percentage of Bregs, Tregs, and PD1+CD38hiCD8+ T cells, but increased Th17 and CD8+ T cells (vs vehicle). Altogether, our results demonstrate that targeting CD38 in CLL can modulate the tumor microenvironment; skewing T-cell populations from an immunosuppressive to immune-reactive milieu, thus promoting immune reconstitution for enhanced anti-CLL response.

Altered T Follicular Helper Cell Subsets and Function in Chronic Lymphocytic Leukemia

Follicular helper T cells (T_FH) have specialized properties in promoting normal B cell activation but their role in chronic lymphocytic leukemia (CLL) is unknown. We find that T_FH cells are elevated in CLL patients and are phenotypically abnormal, expressing higher levels of PD-1, TIGIT, CD40L, IFNγ and IL-21, and exhibiting abnormal composition of T_FH1, T_FH2 and T_FH17 subsets. Frequencies of CD4-positive T cells expressing T_FH1 markers and IL-21 were positively correlated with patient lymphocyte counts and RAI stage, suggesting that accumulation of abnormal T_FH cells is concomitant with expansion of the leukemic B cell clone. Treatment with ibrutinib led to normalization of T_FH frequencies and phenotype. T_FH cells identified in CLL bone marrow display elevated expression of several functional markers compared to blood T_FH cells. CLL T cell-B cell co-culture experiments revealed a correlation of patient T_FH frequencies with functional ability of their CD4-positive T cells to promote CLL proliferation. Conversely, CLL cells can preferentially activate the T_FH cell subset in co-culture. Together our results indicate that CLL development is associated with expansion of abnormal T_FH populations that produce elevated levels of cytokines and costimulatory molecules which may help support CLL proliferation.

Reduced expansion of CD94/NKG2C+ NK cells in chronic lymphocytic leukemia and CLL-like monoclonal B-cell lymphocytosis is not related to increased human cytomegalovirus seronegativity or NKG2C deletions

INTRODUCTION

Dysregulated NK cell-mediated immune responses contribute to tumor evasion in chronic lymphocytic leukemia (CLL), although the NK cell compartment in CLL-like monoclonal B-cell lymphocytosis (MBL) is poorly understood. In healthy individuals, human cytomegalovirus (HCMV) induces the expansion of NK cells expressing high levels of CD94/NKG2C NK cell receptor (NKR) specific for HLA-E.

METHODS

We analyzed the expression of NKG2A, NKG2C, ILT2, KIR, CD161, and CD57 in 24 MBL and 37 CLL. NKG2C was genotyped in these patients and in 81 additional MBL/CLL, while NKG2C gene expression was assessed in 26 cases. In 8 CLL patients with increased lymphocytosis (≥20 × 10⁹ /L), tumor HLA-E and HLA-G expression was evaluated.

RESULTS

NKR distribution did not significantly differ between MBL and CLL patients, although they exhibited reduced NKG2C⁺ NK cells compared with a non-CLL group (4.6% vs 12.2%, P = .012). HCMV⁺ patients showed increased percentages of NKG2C⁺ NK cells compared with HCMV^- (7.3% vs 2.9%, P = .176). Frequencies of NKG2C deletions in MBL/CLL were similar to those of the general population. Low/undetectable NKG2C expression was found among NKG2C^+/- (45%) and NKG2C^+/+ (12%) patients. CLL cases with increased lymphocytosis displayed especially reduced NKG2C expression (1.8% vs 8.1%, P = .029) and tumor cells with high HLA-E (>98%) and variable HLA-G expression (12.4%, range: 0.5-56.4). CLL patients with low NKG2C expression (<7%) showed shorter time to first treatment (P = .037).

CONCLUSION

Reduced percentages of CD94/NKG2C⁺ NK cells were observed in CLL and MBL patients independently of HCMV serostatus and NKG2C zygosity, particularly in CLL patients with increased lymphocytosis, which could potentially be related to the exposure to tumor cells.

Chronic lymphocytic leukemia-like monoclonal B-cell lymphocytosis exhibits an increased inflammatory signature that is reduced in early-stage chronic lymphocytic leukemia

Several studies in chronic lymphocytic leukemia (CLL) patients have reported impaired immune cell functions, which contribute to tumor evasion and disease progression. However, studies on CLL-like monoclonal B-cell lymphocytosis (MBL) are scarce. In the study described here, we characterized the immune environment in 62 individuals with clinical MBL, 56 patients with early-stage CLL, and 31 healthy controls. Gene expression arrays and quantitative reverse transcription polymerase chain reaction were performed on RNA from CD4⁺ peripheral blood cells; serum cytokines were measured with immunoassays; and HLA-DR expression on circulating monocytes, as well as the percentages of Th1, cytotoxic, exhausted, and effector CD4⁺ T cells, were evaluated by flow cytometry. In addition, cell cultures of clonal B cells and CD14-enriched or -depleted cell fractions were performed. Strikingly, MBL and early-stage CLL differed in pro-inflammatory signatures. An increased inflammatory drive orchestrated mainly by monocytes was identified in MBL, which exhibited enhanced phagocytosis, pattern recognition receptors, interleukin-8 (IL8), HMGB1, and acute response signaling pathways and increased pro-inflammatory cytokines (in particular IL8, interferon γ [IFNγ], and tumor necrosis factor α). This inflammatory signature was diminished in early-stage CLL (reduced IL8 and IFNγ levels, IL8 signaling pathway, and monocytic HLA-DR expression compared with MBL), especially in those patients with mutations in IGHV genes. Additionally, CD4⁺ T cells of MBL and early-stage CLL exhibited a similar upregulation of Th1 and cytotoxic genes and expanded CXCR3⁺ and perforin⁺ CD4⁺ T cells, as well as PD1⁺ CD4⁺ T cells, compared with controls. Cell culture assays disclosed tumor-supporting effects of monocytes similarly observed in MBL and early-stage CLL. These novel findings reveal differences in the inflammatory environment between MBL and CLL, highlighting an active role for antigen stimulation in the very early stages of the disease, potentially related to malignant B-cell transformation.

Prognostic models for newly-diagnosed chronic lymphocytic leukaemia in adults: a systematic review and meta-analysis

BACKGROUND

Chronic lymphocytic leukaemia (CLL) is the most common cancer of the lymphatic system in Western countries. Several clinical and biological factors for CLL have been identified. However, it remains unclear which of the available prognostic models combining those factors can be used in clinical practice to predict long-term outcome in people newly-diagnosed with CLL.

OBJECTIVES

To identify, describe and appraise all prognostic models developed to predict overall survival (OS), progression-free survival (PFS) or treatment-free survival (TFS) in newly-diagnosed (previously untreated) adults with CLL, and meta-analyse their predictive performances.

SEARCH METHODS

We searched MEDLINE (from January 1950 to June 2019 via Ovid), Embase (from 1974 to June 2019) and registries of ongoing trials (to 5 March 2020) for development and validation studies of prognostic models for untreated adults with CLL. In addition, we screened the reference lists and citation indices of included studies.

SELECTION CRITERIA

We included all prognostic models developed for CLL which predict OS, PFS, or TFS, provided they combined prognostic factors known before treatment initiation, and any studies that tested the performance of these models in individuals other than the ones included in model development (i.e. 'external model validation studies'). We included studies of adults with confirmed B-cell CLL who had not received treatment prior to the start of the study. We did not restrict the search based on study design.

DATA COLLECTION AND ANALYSIS

We developed a data extraction form to collect information based on the Checklist for Critical Appraisal and Data Extraction for Systematic Reviews of Prediction Modelling Studies (CHARMS). Independent pairs of review authors screened references, extracted data and assessed risk of bias according to the Prediction model Risk Of Bias ASsessment Tool (PROBAST). For models that were externally validated at least three times, we aimed to perform a quantitative meta-analysis of their predictive performance, notably their calibration (proportion of people predicted to experience the outcome who do so) and discrimination (ability to differentiate between people with and without the event) using a random-effects model. When a model categorised individuals into risk categories, we pooled outcome frequencies per risk group (low, intermediate, high and very high). We did not apply GRADE as guidance is not yet available for reviews of prognostic models.

MAIN RESULTS

From 52 eligible studies, we identified 12 externally validated models: six were developed for OS, one for PFS and five for TFS. In general, reporting of the studies was poor, especially predictive performance measures for calibration and discrimination; but also basic information, such as eligibility criteria and the recruitment period of participants was often missing. We rated almost all studies at high or unclear risk of bias according to PROBAST. Overall, the applicability of the models and their validation studies was low or unclear; the most common reasons were inappropriate handling of missing data and serious reporting deficiencies concerning eligibility criteria, recruitment period, observation time and prediction performance measures. We report the results for three models predicting OS, which had available data from more than three external validation studies: CLL International Prognostic Index (CLL-IPI) This score includes five prognostic factors: age, clinical stage, IgHV mutational status, B2-microglobulin and TP53 status. Calibration: for the low-, intermediate- and high-risk groups, the pooled five-year survival per risk group from validation studies corresponded to the frequencies observed in the model development study. In the very high-risk group, predicted survival from CLL-IPI was lower than observed from external validation studies. Discrimination: the pooled c-statistic of seven external validation studies (3307 participants, 917 events) was 0.72 (95% confidence interval (CI) 0.67 to 0.77). The 95% prediction interval (PI) of this model for the c-statistic, which describes the expected interval for the model's discriminative ability in a new external validation study, ranged from 0.59 to 0.83. Barcelona-Brno score Aimed at simplifying the CLL-IPI, this score includes three prognostic factors: IgHV mutational status, del(17p) and del(11q). Calibration: for the low- and intermediate-risk group, the pooled survival per risk group corresponded to the frequencies observed in the model development study, although the score seems to overestimate survival for the high-risk group. Discrimination: the pooled c-statistic of four external validation studies (1755 participants, 416 events) was 0.64 (95% CI 0.60 to 0.67); 95% PI 0.59 to 0.68. MDACC 2007 index score The authors presented two versions of this model including six prognostic factors to predict OS: age, B2-microglobulin, absolute lymphocyte count, gender, clinical stage and number of nodal groups. Only one validation study was available for the more comprehensive version of the model, a formula with a nomogram, while seven studies (5127 participants, 994 events) validated the simplified version of the model, the index score. Calibration: for the low- and intermediate-risk groups, the pooled survival per risk group corresponded to the frequencies observed in the model development study, although the score seems to overestimate survival for the high-risk group. Discrimination: the pooled c-statistic of the seven external validation studies for the index score was 0.65 (95% CI 0.60 to 0.70); 95% PI 0.51 to 0.77.

AUTHORS' CONCLUSIONS

Despite the large number of published studies of prognostic models for OS, PFS or TFS for newly-diagnosed, untreated adults with CLL, only a minority of these (N = 12) have been externally validated for their respective primary outcome. Three models have undergone sufficient external validation to enable meta-analysis of the model's ability to predict survival outcomes. Lack of reporting prevented us from summarising calibration as recommended. Of the three models, the CLL-IPI shows the best discrimination, despite overestimation. However, performance of the models may change for individuals with CLL who receive improved treatment options, as the models included in this review were tested mostly on retrospective cohorts receiving a traditional treatment regimen. In conclusion, this review shows a clear need to improve the conducting and reporting of both prognostic model development and external validation studies. For prognostic models to be used as tools in clinical practice, the development of the models (and their subsequent validation studies) should adapt to include the latest therapy options to accurately predict performance. Adaptations should be timely.

Prognostic role of CD4 T-cell depletion after frontline fludarabine, cyclophosphamide and rituximab in chronic lymphocytic leukaemia

BACKGROUND

Eradication of minimal residual disease (MRD), at the end of Fludarabine-Cyclophosphamide-Rituximab (FCR) treatment, is a validated surrogate marker for progression-free and overall survival in chronic lymphocytic leukaemia. But such deep responses are also associated with severe immuno-depletion, leading to infections and the development of secondary cancers.

METHODS

We assessed, blood MRD and normal immune cell levels at the end of treatment, in 162 first-line FCR patients, and analysed survival and adverse event.

RESULTS

Multivariate Landmark analysis 3 months after FCR completion identified unmutated IGHV status (HR, 2.03, p = 0.043), the level of MRD reached (intermediate versus low, HR, 2.43, p = 0.002; high versus low, HR, 4.56, p = 0.002) and CD4 > 200/mm3 (HR, 3.30, p <  0.001) as factors independently associated with progression-free survival (PFS); neither CD8 nor NK counts were associated with PFS. The CD4 count was associated with PFS irrespective of IGHV mutational status, but only in patients with detectable MRD (HR, 3.51, p = 0.0004, whereas it had no prognostic impact in MRD < 10- 4 patients: p = 0.6998). We next used a competitive risk model to investigate whether immune cell subsets could be associated with the risk of infection and found no association between CD4, CD8 and NK cells and infection.

CONCLUSIONS

Consolidation/maintenance trials based on detectable MRD after FCR should investigate CD4 T-cell numbers both as a selection and a response criterion, and consolidation treatments should target B-cell/T-cell interactions.

Chronic lymphocytic leukaemia: the role of T cells in a B cell disease

Chronic lymphocytic leukaemia (CLL) has long been thought to be an immunosuppressive disease and abnormalities in T-cell subset distribution and function have been observed in many studies. However, the role of T cells (if any) in disease progression remains unclear and has not been directly studied. This has changed with the advent of new therapies, such as chimeric antigen receptor-T cells, which actively use retargeted patient-derived T cells as "living drugs" for CLL. However complete responses are relatively low (~26%) and recent studies have suggested the differentiation status of patient T cells before therapy may influence efficacy. Non-chemotherapeutic drugs, such as idelalisib and ibrutinib, also have an impact on T cell populations in CLL patients. This review will highlight what is known about T cells in CLL during disease progression and after treatment, and discuss the prospects of using T cells as predictive biomarkers for immune status and response to therapy.

Multiparametric analysis of CD8+ T cell compartment phenotype in chronic lymphocytic leukemia reveals a signature associated with progression toward therapy

CD8⁺ T cells are frontline defenders against cancer and primary targets of current immunotherapies. In CLL, specific functional alterations have been described in circulating CD8⁺ T cells, yet a global view of the CD8⁺ T cell compartment phenotype and of its real impact on disease progression is presently elusive. We developed a multidimensional statistical analysis of CD8⁺ T cell phenotypic marker expression based on whole blood multi-color flow-cytometry. The analysis comprises both unsupervised statistics (hClust and PCA) and supervised classification methods (Random forest, Adaboost algorithm, Decision tree learning and logistic regression) and allows to cluster patients by comparing multiple phenotypic markers expressed by CD8⁺ T cells.

Our results reveal a global CD8⁺ T cell phenotypic signature in CLL patients that is significantly modified when compared to healthy donors. We also uncover a CD8⁺ T cell signature characteristic of patients evolving toward therapy within 6 months after phenotyping. The unbiased, not predetermined and multimodal approach highlights a prominent role of the memory compartment in the prognostic signature. The analysis also reveals that imbalance of the central/effector memory compartment in CD8⁺ T cells can occur irrespectively of the elapsed time after diagnosis.

Taken together our results indicate that, in CLL patients, CD8⁺ T cell phenotype is imprinted by disease clinical progression and reveal that CD8⁺ T cell memory compartment alteration is not only a hallmark of CLL disease but also a signature of disease evolution toward the need for therapy.

Improving CLL Vγ9Vδ2-T-cell fitness for cellular therapy by ex vivo activation and ibrutinib

The efficacy of autologous (αβ) T-cell-based treatment strategies in chronic lymphocytic leukemia (CLL) has been modest. The Vγ9Vδ2-T cell subset consists of cytotoxic T lymphocytes with potent antilymphoma activity via a major histocompatibility complex-independent mechanism. We studied whether Vγ9Vδ2-T cells can be exploited as autologous effector lymphocytes in CLL. Healthy control Vγ9Vδ2-T cells were activated by and had potent cytolytic activity against CLL cells. However, CLL-derived Vγ9Vδ2-T cells proved dysfunctional with respect to effector cytokine production and degranulation, despite an increased frequency of the effector-type subset. Consequently, cytotoxicity against malignant B cells was hampered. A comparable dysfunctional phenotype was observed in healthy Vγ9Vδ2-T cells after coculture with CLL cells, indicating a leukemia-induced mechanism. Gene-expression profiling implicated alterations in synapse formation as a conceivable contributor to compromised Vγ9Vδ2-T-cell function in CLL patients. Dysfunction of Vγ9Vδ2-T cells was fully reversible upon activation with autologous monocyte-derived dendritic cells (moDCs). moDC activation resulted in efficient expansion and predominantly yielded Vγ9Vδ2-T cells with a memory phenotype. Furthermore, ibrutinib treatment promoted an antitumor T helper 1 (T_H1) phenotype in Vγ9Vδ2-T cells, and we demonstrated binding of ibrutinib to IL-2-inducible kinase (ITK) in Vγ9Vδ2-T cells. Taken together, CLL-mediated dysfunction of autologous Vγ9Vδ2-T cells is fully reversible, resulting in potent cytotoxicity toward CLL cells. Our data support the potential use of Vγ9Vδ2-T cells as effector T cells in CLL immunotherapy and favor further exploration of combining Vγ9Vδ2-T-cell-based therapy with ibrutinib.

Restricted T cell receptor repertoire in CLL-like monoclonal B cell lymphocytosis and early stage CLL

Analysis of the T cell receptor (TR) repertoire of chronic lymphocytic leukemia-like monoclonal B cell lymphocytosis (CLL-like MBL) and early stage CLL is relevant for understanding the dynamic interaction of expanded B cell clones with bystander T cells. Here we profiled the T cell receptor β chain (TRB) repertoire of the CD4⁺ and CD8⁺ T cell fractions from 16 CLL-like MBL and 13 untreated, Binet stage A/Rai stage 0 CLL patients using subcloning analysis followed by Sanger sequencing. The T cell subpopulations of both MBL and early stage CLL harbored restricted TRB gene repertoire, with CD4⁺ T cell clonal expansions whose frequency followed the numerical increase of clonal B cells. Longitudinal analysis in MBL cases revealed clonal persistence, alluding to persistent antigen stimulation. In addition, the identification of shared clonotypes among different MBL/early stage CLL cases pointed towards selection of the T cell clones by common antigenic elements. T cell clonotypes previously described in viral infections and immune disorders were also detected. Altogether, our findings evidence that antigen-mediated TR restriction occurs early in clonal evolution leading to CLL and may further increase together with B cell clonal expansion, possibly suggesting that the T cell selecting antigens are tumor-related.

Dynamic changes of the normal B lymphocyte repertoire in CLL in response to ibrutinib or FCR chemo-immunotherapy

Using next-generation immunoglobulin (IGH) sequencing and flow cytometry, we characterized the composition, diversity and dynamics of non-malignant B cells in patients undergoing treatment with the Bruton tyrosine kinase (BTK) inhibitor ibrutinib or chemo-immunotherapy with fludarabine, cyclophosphamide, and rituximab (FCR). During ibrutinib therapy, non-malignant B cell numbers declined, but patients maintained stable IGH diversity and constant fractions of IGH-mutated B cells. This indicates partial preservation of antigen-experienced B cells during ibrutinib therapy, but impaired replenishment of the normal B cell pool with naïve B cells. In contrast, after FCR we noted a recovery of normal B cells with a marked predominance of B cells with unmutated IGH. This pattern is compatible with a deletion of pre-existing antigen-experienced B cells followed by repertoire renewal with antigen-naïve B cells. These opposite patterns in B cell dynamics may result in different responses towards neoantigens versus recall antigens, which need to be further defined.

Regulatory T Cells and Their Prognostic Relevance in Hematologic Malignancies

Regulatory T cells (Tregs) have a fundamental function in monitoring the immune homeostasis in healthy individuals. In cancer and, in particular, in hematological malignancies, Tregs exert a major immunosuppressive activity, thus playing a critical role in tumor cell growth, proliferation, and survival. Here, we summarize published data on the prognostic significance of Tregs in hematological malignancies and show that they are highly conflicting. The heterogeneity of the experimental approaches that were used explains-at least in part-the discordant results reported by different groups that have investigated the role of Tregs in cancer. In fact, different tissues have been studied (i.e., peripheral blood, bone marrow, and lymph node), applying different methods (i.e., flow cytometry versus immunohistochemistry, whole blood versus isolated peripheral blood mononuclear cells versus depletion of CD25⁺ cells, various panels of monoclonal antibodies, techniques of fixation and permeabilization, and gating strategies). This is of relevance in order to stress the need to apply standardized approaches in the study of Tregs in hematological malignancies and in cancer in general.

Invariant NKT cells contribute to chronic lymphocytic leukemia surveillance and prognosis

iNKT cells control CLL progression in both mice and patients and this inversely correlates with CD1d expression by leukemia cells. Human iNKT cells indirectly hinder CLL survival by restraining proleukemia monocyte-derived nurse-like cells.

T-cell diversification reflects antigen selection in the blood of patients on immune checkpoint inhibition and may be exploited as liquid biopsy biomarker

Cancer immunotherapy with antibodies targeting immune checkpoints, such as programmed cell death protein 1 (PD-1), shows encouraging results, but reliable biomarkers predicting response to this costly and potentially toxic treatment approach are still lacking. To explore an immune signature predictive for response, we performed liquid biopsy immunoprofiling in 18 cancer patients undergoing PD-1 inhibition before and shortly after initiation of treatment by multicolor flow cytometry and next-generation T- and B-cell immunosequencing (TCRß/IGH). Findings were correlated with clinical outcomes. We found almost complete saturation of surface PD-1 on all T-cell subsets after the first dose of the antibody. Both T- and B-cell compartments quantitatively expanded during treatment. These expansions were mainly driven by an increase in the activated T-cell compartments, as well as of naïve B- and plasma cells. Deep immunosequencing revealed a clear diversification pattern of the clonal T-cell space indicative of antigenic selection in 47% of patients, while the remaining patients showed stable repertoires. 43% of the patients with a diversification pattern showed disease control in response to the PD-1 inhibitor. No disease stabilizations were observed without clonal T-cell space diversification. Our data show for the first time a clear impact of PD-1 targeting not only on circulating T-cells, but also on B-lineage cells, shedding light on the complexity of the anti-tumor immune response. Liquid biopsy T-cell next-generation immunosequencing should be prospectively evaluated as part of a composite response prediction biomarker panel in the context of clinical studies.

Improving therapy of chronic lymphocytic leukemia with chimeric antigen receptor T cells

Adoptive cell immunotherapy for the treatment of chronic lymphocytic leukemia (CLL) has heralded a new era of synthetic biology. The infusion of genetically engineered, autologous chimeric antigen receptor (CAR) T cells directed against CD19 expressed by normal and malignant B cells represents a novel approach to cancer therapy. The results of recent clinical trials of CAR T cells in relapsed and refractory CLL have demonstrated long-term disease-free remissions, underscoring the power of harnessing and redirecting the immune system against cancer. This review will briefly summarize T-cell therapies in development for CLL disease. We discuss the role of T-cell function and phenotype, T-cell culture optimization, CAR design, and approaches to potentiate the survival and anti-tumor effects of infused lymphocytes. Future efforts will focus on improving the efficacy of CAR T cells for the treatment of CLL and incorporating adoptive cell immunotherapy into standard medical management of CLL.

The skewed balance between Tregs and Th17 in chronic lymphocytic leukemia

While Tregs maintain self-tolerance and inhibit antitumor responses, T helper (Th)17 cells may enhance inflammatory and antitumor responses. The balance between these two important T-cell subsets has been skewed in many immunopathologic conditions such as autoimmune and cancer diseases. B-cell chronic lymphocytic leukemia (CLL) is the most common form of leukemia in the western world and is characterized with monoclonal expansion of B lymphocytes. There is evidence which implies that the progression of CLL is associated with expansion of Treg and downregulation of Th17 cells. In this review, we will discuss about immunobiology of Treg and Th17 cells and their role in immunopathogenesis of CLL as well as their reciprocal changes during disease progression.

Mechanisms of PD-L1/PD-1-mediated CD8 T-cell dysfunction in the context of aging-related immune defects in the Eµ-TCL1 CLL mouse model

T-cell defects, immune suppression, and poor antitumor immune responses are hallmarks of chronic lymphocytic leukemia (CLL), and PD-1/PD-L1 inhibitory signaling has emerged as a major immunosuppressive mechanism. However, the effect of different microenvironments and the confounding influence of aging are poorly understood. The current study uses the Eμ-TCL1 mouse model, which replicates human T-cell defects, as a preclinical platform to longitudinally examine patterns of T-cell dysfunction alongside developing CLL and in different microenvironments, with a focus on PD-1/PD-L1 interactions. The development of CLL was significantly associated with changes in T-cell phenotype across all organs and function. Although partly mirrored in aging wild-type mice, CLL-specific T-cell changes were identified. Murine CLL cells highly expressed PD-L1 and PD-L2 in all organs, with high PD-L1 expression in the spleen. CD3(+)CD8(+) T cells from leukemic and aging healthy mice highly expressed PD-1, identifying aging as a confounder, but adoptive transfer experiments demonstrated CLL-specific PD-1 induction. Direct comparisons of PD-1 expression and function between aging CLL mice and controls identified PD-1(+) T cells in CLL as a heterogeneous population with variable effector function. This is highly relevant for therapeutic targeting of CD8(+) T cells, showing the potential of reprogramming and selective subset expansion to restore antitumor immunity.