Immunological Prognostic Factors in Multiple Myeloma.

Multiple myeloma (MM) is a plasma cell neoplasm characterized by an abnormal proliferation of clonal, terminally differentiated B lymphocytes. Current approaches for the treatment of MM focus on developing new diagnostic techniques; however, the search for prognostic markers is also crucial. This enables the classification of patients into risk groups and, thus, the selection of the most optimal treatment method. Particular attention should be paid to the possible use of immune factors, as the immune system plays a key role in the formation and course of MM. In this review, we focus on characterizing the components of the immune system that are of prognostic value in MM patients, in order to facilitate the development of new diagnostic and therapeutic directions.

Hypogelsolinemia in Patients Diagnosed with Acute Myeloid Leukemia at Initial Stage of Sepsis.

BACKGROUND Gelsolin (GSN) is an actin-binding and PIP2/Ca²âº-regulated protein found in the cytoplasm and blood plasma. Hypogelsolinemia occurs in a wide range of traumatic injuries and inflammatory reactions. We hypothesize that blood GSN levels will be altered in patients diagnosed with acute myeloid leukemia (AML) that develop sepsis, and assessment of GSN concentration will be a useful marker to determine their clinical outcome. To achieve this task, we evaluated the plasma gelsolin concentration in blood samples collected from patients diagnosed with acute myeloid leukemia (AML) at initial stages of sepsis. MATERIAL AND METHODS To assess if AML patients might be at risk of sepsis, a SOFA score was determined. Plasma gelsolin concentration was evaluated using an immunoblotting technique. RESULTS We found that GSN concentration in the blood of the AML group with developing sepsis was significantly lower (32±41 µg/ml; p<0.05) compared to the AML group (65±35 µg/ml) and control group (176±37 µg/ml; p<0.001). Additionally, low gelsolin concentration in the blood of AML patients developing sepsis was associated with a high SOFA score. A decrease of GSN concentration in the blood of AML subjects with developing sepsis suggests that GSN level in blood reflects not only chronic inflammation stage associated with leukemia, but that GSN depletion also manifests the inflammation associated with sepsis development. CONCLUSIONS The results presented here suggest the possible utility of GSN evaluation for diagnostic purposes. Overall, these data support the that reversing plasma GSN deficiency might be a possible new strategy in sepsis treatment.

Unexpected profile of sphingolipid contents in blood and bone marrow plasma collected from patients diagnosed with acute myeloid leukemia.

BACKGROUND: Impaired apoptotic pathways in leukemic cells enable them to grow in an uncontrolled way. Moreover, aberrations in the apoptotic pathways are the main factor of leukemic cells drug resistance. METHODS: To assess the presence of potential abnormalities that might promote dysfunction of leukemic cells growth, HPLC system was used to determine sphingosine (SFO), sphinganine (SFA), sphingosine-1-phosphate (S1P) and ceramide (CER) concentration in the blood collected from patients diagnose with acute myeloblastic leukemia (AML; n = 49) and compare to values of control (healthily) group (n = 51). Additionally, in AML group concentration of SFO, SFA, S1P and CER was determined in bone marrow plasma and compared to respective values in blood plasma. The concentration of S1P and CER binding protein - plasma gelsolin (GSN) was also assessed in collected samples using immunoblotting assay. RESULTS: We observed that in AML patients the average SFO, SFA and CER concentration in blood plasma was significantly higher (p < 0.001) compare to control group, when blood plasma S1P concentration was significantly lower (p < 0.001). At the same time the CER/S1P ratio in AML patient (44.5 ± 19.4) was about 54% higher compare to control group (20.9 ± 13.1). Interestingly the average concentration of S1P in blood plasma (196 ± 13 pmol/ml) was higher compare to its concentration in plasma collected from bone marrow (154 ± 21 pmol/ml). CONCLUSIONS: We hypothesize that changes in profile of sphingolipids concentration and some of their binding protein partners such as GSN in extracellular environment of blood and bone marrow cells in leukemic patients can be targeted to develop new AML treatment method(s).

Assessment of the influence of peripheral blood mononuclear cell stimulation with Streptococcus pneumoniae polysaccharides on expression of selected Toll-like receptors, activation markers and Fas antigen in patients with chronic lymphocytic leukemia.

INTRODUCTION: Since 2012, both the 13-valent pneumococcal conjugate vaccine (PCV13) and the 23-valent pneumococcal polysaccharide vaccine (PPV23) have been recommended for pneumococcal infection prevention in patients with chronic lymphocytic leukemia (CLL). Available literature data indicate that leukemic cells may respond to the presence of pathogens through specific Toll-like receptors (TLR). OBJECTIVES: The aim of the study was to assess the effect of in vitro PPV23 stimulation of peripheral blood mononuclear cells (PBMCs) on expression of TLR-2, TLR-4, CD25, CD69, and CD95 on the surface of CD3+ T cells and CD19+ B cells in CLL patients. METHODS: A total of 30 previously untreated patients with CLL, stage 0 according to the Rai classification, were included in the study. PBMCs obtained from each patient were cultured with and without PPV23 antigens. After 24-, 48-, and 72 h cultures, the viable cells underwent labeling with fluorochrome-conjugated monoclonal antibodies, and were analyzed using a flow cytometer. RESULTS: Between 24 h and 72 h (p=0.002) stimulation with PPV23 and between 48 h and 72 h (p=0.034) stimulation with PPV23 the frequencies of CD3+TLR-2+ cells were diminished. Increase of the value of the percentage of CD19+CD69+ cells was observed after 24 h (p=0.003), 48 h (p=0.025) and 72 h (p=0.012) of stimulation with PPV23. Stimulation with PPV23 led to an increase of the percentage of CD19+CD95+ cells after 24 h (p=0.003), 48 h (p=0.015), and 72 h (p=0.006). CONCLUSIONS: We found that both T and B cells respond to antigens of PPV23 by inducing TLR-dependent pathways, lymphocyte activation and CD95 expression.

Assessment of peripheral blood and bone marrow T, NK, NKT and dendritic cells in patients with multiple myeloma.

Symptoms of multiple myeloma (MM) include bone destruction with pathological fractures, kidney failure and frequent infections, which are the major causes of patient mortality. In our recent research, we demonstrated that the degree of dendritic cell (DC) subpopulation deficit could be related to MM progression, which in consequence may contribute to the MM-related impairment of the immune responses. In the present study, we determined by flow cytometry the frequencies of CD4+ and CD8+ T cells, NK, and NKT-like cells as well as their correlation with myeloid and lymphoid populations of DCs in patients with MM. The study involved 50 patients diagnosed with MM at the Department of Hematology in the Holycross Cancer Center in Kielce. The research samples were collected after the MM diagnosis and before the initiation of anticancer therapy. The obtained results revealed the relations between the percentages of DC subpopulations and lymphocyte subsets, especially the activated ones, in the peripheral blood (PB) and bone marrow (BM). The described role of DCs in the process of the immunological response, either adaptive or innate, leads us to conclude that the decrease of the number or percentage of these cells may have a negative impact on the process of activation of effector cells and, consequently, on the effectiveness of a response to foreign as well as neoplastic antigens in patients with MM.

Loeffler's endomyocarditis: from cardiac arrest to complete recovery.

Hypereosinophilic syndromes are rare diseases; however, cardiac involvement is frequently seen. When diagnosed promptly, the prognosis is relatively good; however, a final diagnosis is made by ruling out many conditions leading to secondary eosinophilia. We present a case of Loeffler's endomyocarditis primarily misdiagnosed as an acute coronary syndrome, complicated by low output heart failure and cardiac arrest. After hypereosinophilic syndrome was confirmed and treatment with prednisone initiated, the patient responded well to therapy, and her further recovery was complete and uneventful.

The frequency of myeloid and lymphoid dendritic cells in multiple myeloma patients is inversely correlated with disease progression.

Multiple myeloma (MM) is a neoplastic disease characterized by proliferation and prolonged survival of clonal plasma cells, most frequently occurring in the bone marrow, but also in other tissues. Dendritic cells (DCs) are a heterogeneous population of leukocytes defined as professional antigen presenting cells playing a key role in anticancer immunity. The purpose of this study was to evaluate subpopulations of myeloid and lymphoid DCs in the peripheral blood (PB) and bone marrow (BM) of patients with MM in the different clinical stages of MM and in correlation with known prognostic factors. The study involved 50 patients diagnosed with MM before the initiation of anticancer therapy and 25 individuals belonging to the control group. The mean percentage of myeloid and lymphoid DCs was determined using flow cytometry. In the present study, we demonstrated a significant reduction in the percentages of both myeloid and lymphoid DCs in MM patients, more pronounced in those with the worse prognosis as determined by the high levels of ß2 microglobulin. Accordingly, a marked decrease in the proportions of both myeloid and lymphoid DCs in the BM of patients with advanced clinical stage (III) compared to earlier stages (I+II) was also found. Our results suggest that the degree of DC subpopulations deficit could be related to the MM progression, which in consequence may contribute to the MM-related impairment of the immune responses.

Epstein-Barr virus-associated lymphoproliferative disorders.

The Epstein-Barr virus (EBV) is one of the most common human viruses, infecting more than 90% of the world's adult population. In some individuals the interplay between EBV replication, latency and immune control can be disrupted and evokes prolonged proliferation of EBV-infected lymphocytes and their malignant transformation. Since its discovery as the first human tumor virus, EBV has been implicated in the development of a wide range of human cancers. The evidence for an association with EBV is the strongest for Burkitt's lymphoma, NK/T cell lymphoma, nasopharyngeal carcinoma, Hodgkin's lymphoma and for malignant lymphomas in immune incompetent patients. Additionally, certain epithelial cell tumors, such as gastric carcinoma and breast carcinoma, have been defined as EBV related. However, the virus may be encountered in other types of malignancies. The oncogenic potential of EBV is related to its ability to infect and transform B lymphocytes into continuously growing lymphoblastoid cell lines. EBV encodes a series of products mimicking several growth, transcription and anti-apoptotic factors, to usurp control of the pathways that regulate diverse homeostatic cellular functions. However, the exact mechanism by which EBV promotes oncogenesis remains unclear. The focus of this review is to summarize the current knowledge of oncogenic potential of the Epstein-Barr virus and its role in the pathogenesis of EBV-associated lymphoproliferative disorders.

Immune Checkpoint Pathway Expression in Lymphocyte Subpopulations in Patients with Common Variable Immunodeficiency and Chronic Lymphocytic Leukemia.

This study aims to gain a deeper understanding of chronic lymphocytic leukemia (CLL) and common variable immunodeficiency (CVID) by studying immune cells and specific immune checkpoint signaling pathways. The analysis of the percentage of selected immune points and their ligands (PD-1/PD-L1, CTLA-4/CD86, and CD200R/CD200) on peripheral blood lymphocyte subpopulations was performed using flow cytometry, and additional analyses determining the serum concentration of the above-mentioned molecules were performed using enzyme immunoassay tests. The obtained results indicate several significant changes in the percentage of almost all tested molecules on selected subpopulations of T and B lymphocytes in both CVID and CLL patients in relation to healthy volunteers and between the disease subunits themselves. The results obtained were also supported by the analysis of the serum concentration of soluble molecules tested. By uncovering valuable insights, we hope to enhance our comprehension and management of these conditions, considering both immunodeficiencies and hematological malignancies. Understanding the role of these signaling pathways in disease development and progression may lead to the development of modern, personalized diagnostic and therapeutic strategies. Ultimately, this knowledge may enable the monitoring of the immune system in patients with CVID and CLL, paving the way for improved patient care in the future.

Exploring the Significance of Immune Checkpoints and EBV Reactivation in Antibody Deficiencies with Near-Normal Immunoglobulin Levels or Hyperimmunoglobulinemia.

This study delves into the intricate landscape of primary immunodeficiencies, with a particular focus on antibody deficiencies characterized by near-normal immunoglobulin levels or hyperimmunoglobulinemia. Contrary to the conventional focus on genetic dysregulation, these studies investigate the key roles of immune checkpoints, such as PD-1/PD-L1, CTLA-4/CD86, and CD200R/CD200, on selected subpopulations of T and B lymphocytes and their serum concentrations of soluble forms in patients recruited for the studies in healthy volunteers. In addition, the studies also show the role of Epstein-Barr virus (EBV) reactivation and interactions with tested pathways of immune checkpoints involved in the immunopathogenesis of this disease. By examining the context of antibody deficiencies, this study sheds light on the nuanced interplay of factors beyond genetics, particularly the immune dysregulations that occur in the course of this type of disease and the potential role of EBV reactivation, which affects the clinical presentation of patients and may contribute to the development of cancer in the future, especially related to hematological malignancies.

Could Immune Checkpoint Disorders and EBV Reactivation Be Connected in the Development of Hematological Malignancies in Immunodeficient Patients?

Primary immunodeficiencies (PIDs) and secondary immunodeficiencies (SIDs) are characterized by compromised immune function, rendering individuals susceptible to infections and potentially influencing cancer development. Epstein-Barr virus (EBV), a widespread herpesvirus, has been linked to cancer, particularly in those with weakened immune systems. This study aims to compare selected immune parameters, focusing on immune checkpoint molecules (PD-1/PD-L1, CTLA-4/CD86, CD200R/CD200), and EBV reactivation in patients with chronic lymphocytic leukemia (CLL, a representative of SIDs) and common variable immunodeficiency (CVID, a representative of PIDs). We performed a correlation analysis involving patients diagnosed with CLL, CVID, and a healthy control group. EBV reactivation was assessed using specific antibody serology and viral load quantification. Peripheral blood morphology, biochemistry, and immunophenotyping were performed, with emphasis on T and B lymphocytes expressing immune checkpoints and their serum concentrations. Our findings revealed elevated EBV reactivation markers in both CLL and CVID patients compared with healthy controls, indicating increased viral activity in immunodeficient individuals. Furthermore, immune checkpoint expression analysis demonstrated significantly altered percentages of T and B lymphocytes expressing PD-1/PD-L1, CTLA-4/CD86, and CD200R/CD200 in CLL and CVID patients. This suggests a potential interplay between immune checkpoint dysregulation and EBV reactivation in the context of immunodeficiency. In conclusion, our study underscores the intricate relationship between immune dysfunction, EBV reactivation, and immune checkpoint modulation in the context of immunodeficiency-associated cancers. The altered expression of immune checkpoints, along with heightened EBV reactivation, suggests a potential mechanism for immune evasion and tumor progression. These findings provide insights into the complex interactions that contribute to cancer development in immunocompromised individuals, shedding light on potential therapeutic targets for improved management and treatment outcomes. Further investigations are warranted to elucidate the underlying mechanisms and to explore potential interventions to mitigate cancer risk in these patient populations.

Physiology, Diagnosis and Treatment of Cardiac Light Chain Amyloidosis.

AL (light-chain) amyloidosis is a systemic disease in which amyloid fibers are formed from kappa or lambda immunoglobulin light chains, or fragments thereof, produced by a neoplastic clone of plasmocytes. The produced protein is deposited in tissues and organs in the form of extracellular deposits, which leads to impairment of their functions and, consequently, to death. Despite the development of research on pathogenesis and therapy, the mortality rate of patients with late diagnosed amyloidosis is 30%. The diagnosis is delayed due to the complex clinical picture and the slow progression of the disease. This is the type of amyloidosis that most often contributes to cardiac lesions and causes cardiac amyloidosis (CA). Early diagnosis and correct identification of the type of amyloid plays a crucial role in the planning and effectiveness of therapy. In addition to standard histological studies based on Congo red staining, diagnostics are enriched by tests to determine the degree of cardiac involvement. In this paper, we discuss current diagnostic methods used in cardiac light chain amyloidosis and the latest therapies that contribute to an improved patient prognosis.

Expression of CTLA-4 and CD86 Antigens and Epstein-Barr Virus Reactivation in Chronic Lymphocytic Leukemia-Any Link with Known Prognostic Factors?

Infection with Epstein-Barr virus (EBV) worsens the prognosis in chronic lymphocytic leukemia (CLL), but the underlying mechanisms are not yet established. We intended to assess whether EBV affects the course of CLL by the deregulation of the CTLA-4/CD86 signaling pathway. We used polymerase chain reaction to measure the load of EBV DNA in the blood of 110 newly diagnosed patients with CLL. The expression of CTLA-4 and CD86 antigen on lymphocytes was assessed with flow cytometry. Additionally, CTLA-4 and CD86 serum concentrations were measured through enzyme-linked immunosorbent assays. Fifty-four percent of the patients had detectable EBV DNA [EBV(+)]. In EBV(+) patients the CTLA-4 and CD86 serum concentrations and their expressions on investigated cell populations were significantly higher than in EBV(-) patients. EBV load correlated positively with unfavorable prognostic markers of CLL and the expression of CTLA-4 on CD3+ lymphocytes (r = 0.5339; p = 0.027) and CD86 on CD19+ cells (r = 0.6950; p < 0.001). During a median follow-up period of 32 months EBV(+) patients were more likely to require treatment or have lymphocyte doubling (p < 0.001). Among EBV(+) but not EBV(-) patients, increased expressions of CTLA-4 lymphocytes were associated with elevated risks of progression. We propose that EBV coinfection may worsen prognosis in CLL patients, partly due to EBV-induced up-regulation of CTLA-4 expression.

Collection of umbilical cord blood and the risk of complications in postpartum women after natural labour in the context of the possibility of umbilical cord stem cells usage in clinical practice.

OBJECTIVES: Comparison of changes in peripheral blood venous morphology and the frequency of select complications in patients who underwent umbilical cord blood collection during the third stage of labour by in the utero method compared to patients who did not undergo this procedure. Presentation of current therapeutic possibilities of cord blood stem cells. MATERIAL AND METHODS: The study involved 248 patients who had a vaginal delivery and had umbilical cord blood taken by in utero method during the third stage of labour. The control group consisted of the first 400 patients who gave vaginal delivery starting in 2019. Each patient had a venous peripheral blood count taken before delivery and 18 hours after delivery. Changes in the results of laboratory tests and the occurrence of adverse outcomes, such as postpartum curettage, postpartum haemorrhage and manual removal of placenta, in the 3rd and 4th stage delivery periods, were analysed. RESULTS: In the blood donor group there were significantly lower haemoglobin (11.32 g/L vs 11.61 g/L, p = 0.004) and haematocrit (32.83% vs 33.82% p = 0.001) concentrations after delivery. Umbilical cord donors had a greater difference in haemoglobin (postpartum minus prepartum) (-1.4 g/L vs -0.9 g/L, p = 000), and haematocrit (-4.05% vs -2.5% , p = 0.000). The study group had a higher percentage of patients with postpartum anaemia (haemoglobin concentration < 10 g/L) (15.9% vs 10.64%, p = 0.05), but the result were borderline significant. The groups did not differ in terms of the percentage of postpartum curettage, PPH, manual removal of placenta, percentage of severe anaemia (Hb < 7g/L) or transfusion requirement. CONCLUSION: Collection of umbilical cord blood during the 3rd stage of labour using the in utero method is associated with a statistically significant increase of blood loss and a higher probability of postpartum anaemia. The observed changes are minor and may have little clinical significance in otherwise healthy patients.

Toll-like Receptor 2 as a Marker Molecule of Advanced Ovarian Cancer.

Ovarian cancer is a global problem that affects women of all ages. Due to the lack of effective screening tests and the usually asymptomatic course of the disease in the early stages, the diagnosis is too late, with the result that less than half of the patients diagnosed with ovarian cancer (OC) survive more than five years after their diagnosis. In this study, we examined the expression of TLR2 in the peripheral blood of 50 previously untreated patients with newly diagnosed OC at various stages of the disease using flow cytometry. The studies aimed at demonstrating the usefulness of TLR2 as a biomarker in the advanced stage of ovarian cancer. In this study, we showed that TLR2 expression levels were significantly higher in women with more advanced OC than in women in the control group. Our research sheds light on the prognostic potential of TLR2 in developing new diagnostic approaches and thus in increasing survival in patients with confirmed ovarian cancer.

Paving the Way toward Successful Multiple Myeloma Treatment: Chimeric Antigen Receptor T-Cell Therapy.

Despite the significant progress of modern anticancer therapies, multiple myeloma (MM) is still incurable for the majority of patients. Following almost three decades of development, chimeric antigen receptor (CAR) T-cell therapy now has the opportunity to revolutionize the treatment landscape and meet the unmet clinical need. However, there are still several major hurdles to overcome. Here we discuss the recent advances of CAR T-cell therapy for MM with an emphasis on future directions and possible risks. Currently, CAR T-cell therapy for MM is at the first stage of clinical studies, and most studies have focused on CAR T cells targeting B cell maturation antigen (BCMA), but other antigens such as cluster of differentiation 138 (CD138, syndecan-1) are also being evaluated. Although this therapy is associated with side effects, such as cytokine release syndrome and neurotoxicity, and relapses have been observed, the benefit-risk balance and huge potential drive the ongoing clinical progress. To fulfill the promise of recent clinical trial success and maximize the potential of CAR T, future efforts should focus on the reduction of side effects, novel targeted antigens, combinatorial uses of different types of CAR T, and development of CAR T cells targeting more than one antigen.

CAR-T Cell Therapy-An Overview of Targets in Gastric Cancer.

Gastric cancer (GC) is one of the most commonly diagnosed malignancies and, unfortunately, still has a high mortality rate. Recent research points to CAR-T immunotherapy as a promising treatment for this disease. Using genetically engineered T cells designed to target a previously selected antigen, researchers are able to harness the natural anti-tumor activity of T cells. For therapy to be successful, however, it is essential to choose antigens that are present on tumor cells but not on healthy cells. In this review, we present an overview of the most important targets for CAR-T therapy in the context of GC, including their biologic function and therapeutic application. A number of clinical studies point to the following as important markers in GC: human epidermal growth factor receptor 2, carcinoembryonic antigen, mucin 1, epithelial cell adhesion molecule, claudin 18.2, mesothelin, natural-killer receptor group 2 member D, and folate receptor 1. Although these markers have been met with some success, the search for new and improved targets continues. Key among these novel biomarkers are the B7H6 ligand, actin-related protein 2/3 (ARP 2/3), neuropilin-1 (NRP-1), desmocollin 2 (DSC2), anion exchanger 1 (AF1), and cancer-related antigens CA-72-4 and CA-19-9.

Chronic Lymphocytic Leukemia-Induced Humoral Immunosuppression: A Systematic Review.

Secondary immunodeficiency is observed in all patients with chronic lymphocytic leukemia (CLL) in varying degrees. The aim of the study was to review the available literature data on patients with CLL, with particular regard to the pathogenesis of the disease and the impact of humoral immunity deficiency on the clinical and therapeutic approach. A systematic literature review was carried out by two independent authors who searched PubMed databases for studies published up to January 2020. Additionally, Google Scholar was used to evaluate search results and support manual research. The search resulted in 240 articles eligible for analysis. After all criteria and filters were applied, 22 studies were finally applied to the analysis. The data analysis showed that the clinical heterogeneity of CLL patients correlates with the diversity of molecular abnormalities determining the clinical picture of the disease, the analysis of which enables setting therapeutic targets. Additionally, in improving the therapeutic method, it is worth introducing supportive therapies with the use of vaccines, antibiotics and/or immunoglobins. Moreover, humoral immunodeficiency in CLL has a strong influence on the risk of infection in patients for whom infections are a major cause of morbidity and mortality.

Cereblon (CRBN) gene polymorphisms predict clinical response and progression-free survival in relapsed/refractory multiple myeloma patients treated with lenalidomide: a pharmacogenetic study from the IMMEnSE consortium.

Cereblon (CRBN) is crucial for antiproliferative and immunomodulatory properties of immunomodulatory drugs. The objective of this study was to verify whether germline single nucleotide polymorphisms (SNPs) in the CRBN gene may influence response to lenalidomide in multiple myeloma (MM). Fourteen tagging SNPs covering the genetic variability in the CRBN gene region were genotyped in 167 Polish patients with refractory/relapsed MM treated with lenalidomide-based regimens. We found that carriers of minor alleles of two studied CRBN SNPs rs1714327G > C (OR = 0.26; 95% CI = 0.1-0.67; p = .0055, Bonferroni corrected p = .033) and rs1705814T > C (OR = 0.22; 95% CI = 0.07-0.65; p = .0063, Bonferroni corrected p = .037) were significantly associated with lower probability of achievement at least partial remission while treated with lenalidomide-based regimens, using the dominant inheritance model. Moreover, one of these SNPs, namely rs1705814T > C, was correlated with shorter progression-free survival (HR = 2.49; 95%CI = 1.31-4.74, p = .0054, Bonferroni corrected p = .033). It is suggested that selected germline CRBN allelic variants (rs1714327G > C and rs1705814T > C) affect lenalidomide efficacy in patients with relapsed/refractory MM.

Programmed cell death 1 expression and Epstein-Barr virus infection in chronic lymphocytic leukaemia: a prospective cohort study.

PURPOSE: Infection with Epstein-Bar virus (EBV) is associated with an unfavourable prognosis in chronic lymphocytic leukaemia (CLL), but the underlying mechanisms remain unknown. We aimed to establish whether EBV worsens the course of CLL by up-regulating the programmed cell death 1 expression. PATIENTS AND METHODS: Using polymerase chain reaction, we measured EBV DNA in the blood of 110 newly diagnosed, treatment-naïve patients with CLL. We used flow cytometry to measure the expression of programmed cell death protein 1 (PD-1) and programmed cell death protein 1 ligand (PD-L1) on CD4+, CD8+, and CD19+ cells. Additionally, PD-1 and PD-L1 serum concentrations were measured using enzyme-linked immunosorbent assays. We related the expressions of PD-1 and PD-L1 to EBV DNA load and clinical outcomes. RESULTS: Fifty-nine (54%) patients had detectable EBV DNA [EBV(+)], and these patients had more advanced disease at baseline than the rest. PD-1 and PD-L1 serum concentrations and their expressions on all cell populations were higher in EBV(+) than EBV(-) patients. EBV load correlated positively with unfavourable clinical markers of CLL and the expression of PD-1 and PD-L1 on CD4+ and CD8+ cells (rho =0.42-0.75; p<0.001). EBV(+) patients had increased risks of treatment initiation and lymphocyte doubling during a median follow-up period of 32 months (p<0.001). Among EBV(+), but not EBV(-), patients, higher expressions of PD-1 and PD-L1 on CD4+ and CD8+ cells were associated with higher risks of treatment initiation and lymphocyte doubling (p≤0.020). CONCLUSION: EBV-induced up-regulation of PD-1-PD-L1 expression is associated with worse outcomes in CLL.