Application of flow cytometric in situ hybridization assay to Epstein-Barr virus-associated T/natural killer cell lymphoproliferative diseases

Epstein-Barr virus-driven lymphoproliferation in inborn errors of immunity: a diagnostic and therapeutic challenge

INTRODUCTION

Inborn errors of immunity (IEI) are a group of genetically heterogeneous disorders with a wide-ranging clinical phenotype, varying from increased predisposition to infections to dysregulation of the immune system, including autoimmune phenomena, autoinflammatory disorders, lymphoproliferation, and malignancy. Lymphoproliferative disorder (LPD) in IEI refers to the nodal or extra-nodal and persistent or recurrent clonal or non-clonal proliferation of lymphoid cells in the clinical context of an inherited immunodeficiency or immune dysregulation. The Epstein-Barr virus (EBV) plays a significant role in the etiopathogenesis of LPD in IEIs. In patients with specific IEIs, lack of immune surveillance can lead to an uninhibited proliferation of EBV-infected cells that may result in chronic active EBV infection, hemophagocytic lymphohistiocytosis, and LPD, particularly lymphomas.

AREAS COVERED

We intend to discuss the pathogenesis, diagnosis, and treatment modalities directed toward EBV-associated LPD in patients with distinct IEIs.

EXPERT OPINION

EBV-driven lymphoproliferation in IEIs presents a diagnostic and therapeutic problem that necessitates a comprehensive understanding of host-pathogen interactions, immune dysregulation, and personalized treatment approaches. A multidisciplinary approach involving immunologists, hematologists, infectious disease specialists, and geneticists is paramount to addressing the diagnostic and therapeutic challenges posed by this intriguing yet formidable clinical entity.

Highly sensitive detection of Epstein-Barr virus-infected cells by EBER flow FISH

When Epstein-Barr virus (EBV) infection is suspected, identification of infected cells is important to understand the pathogenesis, determinine the treatment strategy, and predict the prognosis. We used the PrimeFlow™ RNA Assay Kit with a probe to detect EBV-encoded small RNAs (EBERs) and multiple surface markers, to identify EBV-infected cells by flow cytometry. We analyzed a total of 24 patients [11 with chronic active EBV disease (CAEBV), 3 with hydroa vacciniforme lymphoproliferative disorder, 2 with X-linked lymphoproliferative disease type 1 (XLP1), 2 with EBV-associated hemophagocytic lymphohistiocytosis, and 6 with posttransplant lymphoproliferative disorder (PTLD)]. We compared infected cells using conventional quantitative PCR methods and confirmed that infected cell types were identical in most patients. Patients with CAEBV had widespread infection in T and NK cells, but a small amount of B cells were also infected, and infection in patients with XLP1 and PTLD was not limited to B cells. EBV-associated diseases are believed to be complex pathologies caused by EBV infecting a variety of cells other than B cells. We also demonstrated that infected cells were positive for HLA-DR in patients with CAEBV. EBER flow FISH can identify EBV-infected cells with high sensitivity and is useful for elucidating the pathogenesis.

Single-Cell Transcriptomic Analysis of Epstein-Barr Virus-Associated Hemophagocytic Lymphohistiocytosis

Epstein-Barr virus (EBV) infection can lead to infectious mononucleosis (EBV-IM) and, more rarely, EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH), which is characterized by a life-threatening hyperinflammatory cytokine storm with immune dysregulation. Interferon-gamma (IFNγ) has been identified as a critical mediator for primary HLH; however, the detailed role of IFNγ and other cytokines in EBV-HLH is not fully understood. In this study, we used single-cell RNA sequencing to characterize the immune landscape of EBV-HLH and compared it with EBV-IM. Three pediatric patients with EBV-HLH with different backgrounds, one with X-linked lymphoproliferative syndrome type 1 (XLP1), two with chronic active EBV disease (CAEBV), and two patients with EBV-IM were enrolled. The TUBA1B + STMN1 + CD8 + T cell cluster, a responsive proliferating cluster with rich mRNA detection, was explicitly observed in EBV-IM, and the upregulation of SH2D1A-the gene responsible for XLP1-was localized in this cluster. This proliferative cluster was scarcely observed in EBV-HLH cases. In EBV-HLH cases with CAEBV, upregulation of LAG3 was observed in EBV-infected cells, which may be associated with an impaired response by CD8 + T cells. Additionally, genes involved in type I interferon (IFN) signaling were commonly upregulated in each cell fraction of EBV-HLH, and activation of type II IFN signaling was observed in CD4 + T cells, natural killer cells, and monocytes but not in CD8 + T cells in EBV-HLH. In conclusion, impaired responsive proliferation of CD8 + T cells and upregulation of type I IFN signaling were commonly observed in EBV-HLH cases, regardless of the patients' background, indicating the key features of EBV-HLH.

Updated guidelines for chronic active Epstein-Barr virus disease

Chronic active Epstein-Barr virus disease (CAEBV), formerly named chronic active Epstein-Barr virus infection, is characterized by systemic inflammation and clonal proliferation of Epstein-Barr virus (EBV)-infected T or NK cells. As CAEBV is a potentially life-threatening illness, appropriate diagnosis and therapeutic interventions are necessary for favorable clinical outcomes. Substantial evidence regarding the pathogenesis and treatment of CAEBV has been accumulated since previous guidelines for the diagnosis of CAEBV were proposed. To reflect this evidence, we updated the guidelines for the diagnosis and treatment of CAEBV to improve clinical management of the disease. The details of the updated guidelines are presented in this report. Diagnosis of CAEBV now requires confirmation of a high copy number of EBV genome and EBV-infected T or NK cells. An EBV DNA load ≥ 10,000 IU/mL in whole blood is proposed as the diagnostic cutoff value for CAEBV in this updated guideline. A standard treatment approach for CAEBV has not been established, and hematopoietic stem cell transplantation (HSCT) is considered the only curative treatment. Chemotherapy can be administered to control disease activity before HSCT.

Coexpression of natural killer cell antigens by T-cell large granular lymphocytes in hydroa vacciniforme lymphoproliferative disorder and the involvement of Vδ1 + epithelial-type γδT cells

Hydroa vacciniforme lymphoproliferative disorder (HV-LPD) is a cutaneous variant of chronic active Epstein-Barr virus disease. We examined the coexpression of T- and natural killer (NK)-cell antigens in five patients with classic HV (cHV) and five with systemic HV (sHV). T-cell receptor (TCR) repertoire analysis was performed with high‑throughput sequencing. All five cHV patients had increased γδT cells (> 5%), whereas five sHV patients showed γδT- and αβT-cell dominance in two patients each, and a mixture of abnormal γδT and αβT cells in one. Circulating CD3 + T cells expressed CD16/CD56 at 7.8-42.3% and 1.1-9.7% in sHV and cHV, respectively. The percentage of CD16/CD56 + T cells was higher in the large granular lymphocyte or atypical T-cell fractions in sHV, but no TCR Vα24 invariant chain characteristic of NKT cells was detected. Considerable numbers of CD3 + cells expressing CD56 were observed in sHV skin infiltrates. Of the circulating γδT cells tested, TCR Vδ1 + cells characteristic of the epithelial type of γδT cells were dominant in two sHV cases. Thus, atypical αβT and γδT cells in HV-LPD can express NK-cell antigens, such as CD16 and CD56, and Vδ1 + epithelial-type γδT cells are a major cell type in some HV-LPD cases.

Lymphoproliferation in Inborn Errors of Immunity: The Eye Does Not See What the Mind Does Not Know

Inborn errors of immunity (IEIs) are a group of heterogeneous disorders characterized by a broad clinical spectrum of recurrent infections and immune dysregulation including autoimmunity and lymphoproliferation (LP). LP in the context of IEI may be the presenting feature of underlying immune disorder or may develop during the disease course. However, the correct diagnosis of LP in IEI as benign or malignant often poses a diagnostic dilemma due to the non-specific clinical features and overlapping morphological and immunophenotypic features which make it difficult to treat. There are morphological clues to LP associated with certain IEIs. A combination of ancillary techniques including EBV-associated markers, flow cytometry, and molecular assays may prove useful in establishing a correct diagnosis in an appropriate clinical setting. The present review attempts to provide comprehensive insight into benign and malignant LP, especially the pathogenesis, histological clues, diagnostic strategies, and treatment options in patients with IEIs.

A Double-Blind, Placebo-Controlled, Crossover Study of Magnesium Supplementation in Patients with XMEN Disease

X-linked MAGT1 deficiency with increased susceptibility to Epstein-Barr virus (EBV) infection and N-linked glycosylation defect (XMEN) disease is an inborn error of immunity caused by loss-of-function mutations in the magnesium transporter 1 (MAGT1) gene. The original studies of XMEN patients focused on impaired magnesium regulation, leading to decreased EBV-cytotoxicity and the loss of surface expression of the activating receptor "natural killer group 2D" (NKG2D) on CD8+ T cells and NK cells. In vitro studies showed that supraphysiological supplementation of magnesium rescued these defects. Observational studies in 2 patients suggested oral magnesium supplementation could decrease EBV viremia. Hence, we performed a randomized, double-blind, placebo-controlled, crossover study in 2 parts. In part 1, patients received either oral magnesium L-threonate (MLT) or placebo for 12 weeks followed by 12 weeks of the other treatment. Part 2 began with 3 days of high-dose intravenous (IV) magnesium sulfate (MgSO4) followed by open-label MLT for 24 weeks. One EBV-infected and 3 EBV-naïve patients completed part 1. One EBV-naïve patient was removed from part 2 of the study due to asymptomatic elevation of liver enzymes during IV MgSO4. No change in EBV or NKG2D status was observed. In vitro magnesium supplementation experiments in cells from 14 XMEN patients failed to significantly rescue NKG2D expression and the clinical trial was stopped. Although small, this study indicates magnesium supplementation is unlikely to be an effective therapeutic option in XMEN disease.

Flow-FISH as a Tool for Studying Bacteria, Fungi and Viruses

Many techniques are currently in use to study microbes. These can be aimed at detecting, identifying, and characterizing bacterial, fungal, and viral species. One technique that is suitable for high-throughput analysis is flow cytometry-based fluorescence in situ hybridization, or Flow-FISH. This technique employs (fluorescently labeled) probes directed against DNA or (m)RNA, for instance targeting a gene or microorganism of interest and provides information on a single-cell level. Furthermore, by combining Flow-FISH with antibody-based protein detection, proteins of interest can be measured simultaneously with genetic material. Additionally, depending on the type of Flow-FISH assay, Flow-FISH can also be multiplexed, allowing for the simultaneous measurement of multiple gene targets and/or microorganisms. Together, this allows for, e.g., single-cell gene expression analysis or identification of (sub)strains in mixed cultures. Flow-FISH has been used in mammalian cells but has also been extensively employed to study diverse microbial species. Here, the use of Flow-FISH for studying microorganisms is reviewed. Specifically, the detection of (intracellular) pathogens, studying microorganism biology and disease pathogenesis, and identification of bacterial, fungal, and viral strains in mixed cultures is discussed, with a particular focus on the viruses EBV, HIV-1, and SARS-CoV-2.

T Cell-Epstein-Barr Virus-Associated Hemophagocytic Lymphohistiocytosis (HLH) Occurs in Non-Asians and Is Associated with a T Cell Activation State that Is Comparable to Primary HLH

Purpose

T cell-Epstein-Barr virus–associated hemophagocytic lymphohistiocytosis (T cell-EBV-HLH) is prevalent in East Asia and has poor prognosis. Understanding of this disease is limited, and literature regarding prevalence in North America is scarce. Herein, we summarize our experience.

Methods

A retrospective analysis of T cell-EBV-HLH patients admitted to Children’s Healthcare of Atlanta (GA, USA) from 2010 to 2020 was conducted. Additional immune studies were completed in a subset of patients.

Results

We report 15 patients (10 months–19 years of age) diagnosed with T cell-EBV-HLH. Nine patients were Hispanic, and the majority did not have primary HLH (p-HLH) gene defects. Soluble interleukin-2 receptor levels in T cell-EBV-HLH were significantly higher than other forms of secondary-HLH but comparable to p-HLH, and it correlated with disease severity at presentation. Natural killer cell function was decreased in most patients despite a negative workup for p-HLH. Depending on disease severity, initial therapy included dexamethasone or dexamethasone and etoposide. Refractory patients were managed with blended regimens that included one or more of the following therapies: combination chemotherapy, alemtuzumab, emapalumab, and nivolumab. Rituximab did not appreciably decrease EBV viremia in most patients. Non-critically ill patients responded well to immunosuppressive therapy and are long-term survivors without undergoing allogeneic hematopoietic stem cell transplantation (HSCT). Alemtuzumab resulted in inflammation flare in two of the three patients. Three patients underwent allogeneic HSCT, with disease relapse noted in one. At a median follow-up of 3 years, 10 of the 15 patients are alive.

Conclusion

T cell-EBV-HLH occurs in the USA among the non-Asian populations, especially in those who are Hispanic.

Rapid identification and characterization of infected cells in blood during chronic active Epstein-Barr virus infection

Epstein-Barr virus (EBV) preferentially infects epithelial cells and B lymphocytes and sometimes T and NK lymphocytes. Persistence of EBV-infected cells results in severe lymphoproliferative disorders (LPDs). Diagnosis of EBV-driven T or NK cell LPD and chronic active EBV diseases (CAEBV) is difficult, often requiring biopsies. Herein, we report a flow-FISH cytometry assay that detects cells expressing EBV-encoded small RNAs (EBERs), allowing rapid identification of EBV-infected cells among PBMCs. EBV-infected B, T, and/or NK cells were detectable in various LPD conditions. Diagnosis of CAEBV in 22 patients of Caucasian and African origins was established. All exhibited circulating EBV-infected T and/or NK cells, highlighting that CAEBV is not restricted to native American and Asian populations. Proportions of EBV-infected cells correlated with blood EBV loads. We showed that EBV-infected T cells had an effector memory activated phenotype, whereas EBV-infected B cells expressed plasma cell differentiation markers. Thus, this method achieves accurate and unambiguous diagnoses of different forms of EBV-driven LPD and represents a powerful tool to study their pathophysiological mechanisms.

Patients With Natural Killer (NK) Cell Chronic Active Epstein-Barr Virus Have Immature NK Cells and Hyperactivation of PI3K/Akt/mTOR and STAT1 Pathways

BACKGROUND

Chronic active Epstein-Barr virus (CAEBV) presents with high levels of viral genomes in blood and tissue infiltration with Epstein-Barr virus (EBV)-positive lymphocytes. The pathogenesis of CAEBV is poorly understood.

METHODS

We evaluated 2 patients with natural killer (NK) cell CAEBV and studied their NK cell phenotype and signaling pathways in cells.

RESULTS

Both patients had increased numbers of NK cells, EBV predominantly in NK cells, and immature NK cells in the blood. Both patients had increased phosphorylation of Akt, S6, and STAT1 in NK cells, and increased total STAT1. Treatment of 1 patient with sirolimus reduced phosphorylation of S6 in T and B cells, but not in NK cells and did not reduce levels of NK cells or EBV DNA in the blood. Treatment of both patients' cells with JAK inhibitors in vitro reduced phosphorylated STAT1 to normal. Patients with T- or B-cell CAEBV had increased phosphorylation of Akt and S6 in NK cells, but no increase in total STAT1.

CONCLUSIONS

The increase in phosphorylated Akt, S6, and STAT1, as well as immature NK cells describe a new phenotype for NK cell CAEBV. The reduction of STAT1 phosphorylation in their NK cells with JAK inhibitors suggests a novel approach to therapy.

Determination of Epstein-Barr Virus-Infected Lymphocyte Cell Types in Peripheral Blood Mononuclear Cells as a Valuable Diagnostic Tool in Hematological Diseases

Background

High loads of Epstein-Barr virus (EBV) in peripheral blood mononuclear cells (PBMCs) can be indicative of a broad spectrum of diseases, ranging from asymptomatic infection to fatal cancers.

Methods

We retrospectively investigated the EBV-infected cell types in PBMCs among 291 patients. Based on EBV-infected cell types, the clinical features and prognoses of 93 patients with EBV-associated (EBV⁺) T/natural killer (NK)–cell lymphoproliferative diseases (LPDs) T/NK-LPDs) were investigated over a 5-year period.

Results

Although B-cell-type infection was found in immunocompromised patients and patients with asymptomatic high EBV carriage, infectious mononucleosis, EBV⁺ B-cell LPDs and B-cell lymphomas, T-cell, NK-cell or multiple-cell-type infection in immunocompetent hosts were highly suggestive of EBV⁺ T/NK-LPDs, EBV⁺ T/NK-cell lymphomas, and aggressive NK-cell leukemia. Patients with non–B-cell infection had a poorer prognosis than those with B-cell-type infection. In our cohort, 79.6% of patients with EBV⁺ T/NK-LPDs were >18 years old, and NK cells were identified as EBV-infected cell type in 54.8%. Nearly half of patients with EBV⁺ T/NK-LPDs had genetic defects associated with immunodeficiency. However, hemophagocytic lymphohistiocytosis, and not genetic defects, was the only parameter correlated with poor prognosis of EBV⁺ T/NK-LPDs.

Conclusions

Determination of EBV-infected cell types among PBMCs is a valuable tool for the differential diagnosis of EBV⁺ hematological diseases.

In this study, determination of Epstein-Barr virus-infected cell types in peripheral blood mononuclear cells of 291 patients with high Epstein-Barr virus loads were retrospectively investigated, which indicate it is a valuable tool for Epstein-Barr virus-associated hematological diseases.

An Efficient and Simple Method to Establish NK and T Cell Lines from Patients with Chronic Active Epstein-Barr Virus Infection

A number of methods have been described to establish NK/T cell lines from patients with lymphoma or lymphoproliferative syndrome. These methods employed feeder cells, purified NK or T cells with as much as 10 mL of blood, or a high-dose of IL-2. This study presents a new method with a powerful and simple strategy to establish NK and T cell lines by culturing the peripheral blood mononuclear cells (PBMC) with the addition of recombinant human IL-2 (rhIL-2), and uses as little as 2 mL of whole blood. The cells can proliferate quickly in two weeks and be maintained for more than 3 months. With this method, 7 NK or T cell lines have been established with a high success rate. This method is simple, reliable, and applicable to establishing cell lines from more cases of CAEBV or NK/T cell lymphoma.

Clinicopathological categorization of Epstein-Barr virus-positive T/NK-cell lymphoproliferative disease: an analysis of 42 cases with an emphasis on prognostic implications

Epstein-Barr virus-positive T/NK-cell lymphoproliferative diseases (EBV-T/NK-LPDs) include several overlapping EBV-related conditions with variably aggressive courses. For prognostic categorization, we retrospectively analyzed 42 EBV-T/NK-LPD cases. Male (79% [33/42]), young (≤40 years; 83% [35/42]) patients and T-cell lineage (81% [34/42]; CD8/CD4 = 1.8) were predominant. Clinicopathologically, three systemic and one cutaneous category were developed: hemophagocytic lymphohistiocytosis (HLH; 26% [11/42]), chronic active EBV infection (CAEBV; 31% [13/42]), systemic unclassifiable disease (24% [10/42]), and hydroa vacciniforme/hydroa vacciniforme-like lymphoma (HV/HVL; 19% [8/42]). Prognostically, cutaneous disease (HV/HVL) was better than systemic disease (p = 0.014; median, 285 vs. 10 months). In systemic diseases, HLH was worst (p = 0.002; 3[HLH] vs. 4[unclassifiable] vs. not reached [CAEBV]). Univariate survival analysis (n = 42) revealed cytopenia (≥one lineage; p < 0.001), onset age (>40 years; p = 0.001), T-cell lineage (p = 0.041), hemophagocytic histiocytes (p = 0.031), elevated lactate dehydrogenase (p = 0.020), and liver dysfunction (p = 0.023) predicted shorter survival. In multivariate analysis, T-cell lineage (p = 0.025 [HR =11.3]) and cytopenia (p = 0.028 [HR =5.4]) were independent prognostic factors. Therefore, EBV-T/NK-LPD could be classified into four prognostic categories.

Flow Cytometric Characterization of Antigen-Specific T Cells Based on RNA and Its Advantages in Detecting Infections and Immunological Disorders

Fluorescence in situ hybridization coupled with flow cytometry (FISH-Flow) is a highly quantitative, high-throughput platform allowing precise quantification of total mRNA transcripts in single cells. In undiagnosed infections posing a significant health burden worldwide, such as latent tuberculosis or asymptomatic recurrent malaria, an important challenge is to develop accurate diagnostic tools. Antigen-specific T cells create a persistent memory to pathogens, making them useful for diagnosis of infection. Stimulation of memory response initiates T-cell transitions between functional states. Numerous studies have shown that changes in protein levels lag real-time T-cell transitions. However, analysis at the single-cell transcriptional level can determine the differences. FISH-Flow is a powerful tool with which to study the functional states of T-cell subsets and to identify the gene expression profiles of antigen-specific T cells during disease progression. Advances in instrumentation, fluorophores, and FISH methodologies will broaden and deepen the use of FISH-Flow, changing the immunological field by allowing determination of functional immune signatures at the mRNA level and the development of new diagnostic tools.

Epstein-Barr virus type 2 latently infects T cells, inducing an atypical activation characterized by expression of lymphotactic cytokines

Epstein-Barr virus (EBV) is a well-established B-cell-tropic virus associated with various lymphoproliferative diseases of both B-cell and non-B-cell origin. EBV is associated with a number of T-cell lymphomas; however, in vitro studies utilizing prototypical EBV type 1 (EBV-1) laboratory strains have generally failed to readily infect mature T cells in culture. The difficulties in performing in vitro T-cell experiments have left questions regarding the role of EBV in the pathogenesis of EBV-positive T-cell lymphoproliferative diseases largely unresolved. We report here that the EBV type 2 (EBV-2) strain displays a unique cell tropism for T cells. In remarkable contrast to EBV-1, EBV-2 readily infects primary T cells in vitro, demonstrating a propensity for CD8(+) T cells. EBV-2 infection of purified T cells results in expression of latency genes and ultimately leads to T-cell activation, substantial proliferation, and profound alteration of cytokine expression. The pattern of cytokine production is strikingly skewed toward chemokines with roles in lymphocyte migration, demonstrating that EBV-2 has the ability to modulate normal T-cell processes. Collectively, these novel findings identify a previously unknown cell population potentially utilized by EBV-2 to establish latency and lay the foundation for further studies to elucidate the role of EBV in the pathogenesis of T-cell lymphoproliferative diseases.

IMPORTANCE

The ability of EBV to infect T cells is made apparent by its association with a variety of T-cell lymphoproliferative disorders. However, studies to elucidate the pathogenic role of EBV in these diseases have been limited by the inability to conduct in vitro T-cell infection experiments. Here, we report that EBV-2 isolates, compromised in the capacity to immortalize B cells, infect CD3(+) T cells ex vivo and propose a working model of EBV-2 persistence where alteration of T-cell functions resulting from EBV-2 infection enhances the establishment of latency in B cells. If indeed EBV-2 utilizes T cells to establish a persistent infection, this could provide one mechanism for the association of EBV with T-cell lymphomas. The novel finding that EBV-2 infects T cells in culture will provide a model to understand the role EBV plays in the development of T-cell lymphomas.

Systemic lymphoma arising from hydroa vacciniforme-like lymphoma: report of two cases with review of literature

Hydroa vacciniforme-like lymphoma (HVLL) is an extremely rare lymphoma described in children that occurs mainly in Asia and Latin American countries. It is an Epstein-Barr virus (EBV)-positive lymphoproliferative disease (LPD) characterized by a monoclonal proliferation of T or NK cells. In this study, we report the clinical and pathological features of two Chinese patients with HVLL showed T-cell phenotype expressing CD4. The two patients generally presented with similar clinical histories of waxing and waning ulcerative blistering lesions for ten years or more until progression to systemic lymphoma. One patient died two months after progression and another is alive with disease. In the two cases, persistence infection of EBV may be attributed to the disease progression, and systemic lymphoma arising from HVLL behaves in an aggressive fashion and is predisposing to chemotherapeutic agent resistance.

Anti-CCR4 monoclonal antibody mogamulizumab for the treatment of EBV-associated T- and NK-cell lymphoproliferative diseases

PURPOSE

Epstein-Barr virus (EBV) infects not only B cells but also T cells and natural killer (NK) cells, and T- and NK-cell lymphoproliferative diseases (T/NK-LPD) that are refractory to conventional chemotherapies may develop. To identify a molecular-targeted therapy for EBV-associated T/NK-LPDs, we investigated whether CC chemokine receptor 4 (CCR4) was expressed on EBV-infected T and/or NK cells and whether a humanized anti-CCR4 monoclonal antibody, mogamulizumab, was effective.

EXPERIMENTAL DESIGN

CCR4 expression was examined in various cell lines. In vitro, the effects of mogamulizumab on cell lines were evaluated in the presence of peripheral blood mononuclear cells from volunteers. In vivo, the effects of mogamulizumab were evaluated using a murine xenograft model. CCR4 expression was examined on EBV-infected cells from patients with EBV-associated T/NK-LPDs. Ex vivo, the effects of mogamulizumab were evaluated using patient lymphocytes.

RESULTS

CCR4 expression was confirmed in most EBV-positive T and NK cell lines. Mogamulizumab induced antibody-dependent cellular cytotoxicity (ADCC) activity against CCR4-positive cell lines, and inhibited the growth of EBV-positive NK-cell lymphomas in a murine xenograft model. Furthermore, CCR4 was expressed on EBV-infected cells in 8 of 17 patients with EBV-associated T/NK-LPDs. Interestingly, CCR4 was positive in 5 of 5 patients with hydroa vacciniforme, a photodermatosis caused by the clonal expansion of EBV-infected γδT cells. EBV-positive γδT cells were obtained from a patient with hydroa vacciniforme and subjected to an antibody-dependent cell-mediated cytotoxicity (ADCC) assay. The γδT cells that were positive for CCR4 were killed by mogamulizumab via ADCC.

CONCLUSIONS

These results indicate that mogamulizumab may be a therapeutic option against EBV-associated T/NK-LPDs.

Current research on chronic active Epstein-Barr virus infection in Japan

Epstein-Barr virus (EBV) infection is usually asymptomatic and persists lifelong. Although EBV-infected B cells have the potential for unlimited proliferation, they are effectively removed by the virus-specific cytotoxic T cells, and EBV-associated lymphoproliferative disease develops only in immunocompromised hosts. Rarely, however, individuals without apparent immunodeficiency develop chronic EBV infection with persistent infectious mononucleosis-like symptoms. These patients have high EBV-DNA load in the peripheral blood and systemic clonal expansion of EBV-infected T cells or natural killer (NK) cells. Their prognosis is poor with life-threatening complications including hemophagocytic lymphohistiocytosis, organ failure, and malignant lymphomas. The term "chronic active EBV infection" (CAEBV) is now generally used for this disease. The geographical distribution of CAEBV is markedly uneven and most cases have been reported from Japan and other East Asian countries. Here we summarize the current understanding of CAEBV and describe the recent progress of CAEBV research in Japan.

A probable identical Epstein-Barr virus clone-positive composite lymphoma with aggressive natural killer-cell leukemia and cytotoxic T-cell lymphoma

The patient was a 52-year old woman with a history of mosquito-bite hypersensitivity since childhood. In July 2011, she developed pyrexia, headaches, and nausea, and Epstein-Barr virus (EBV)-positive aggressive natural killer leukemia (ANKL) was diagnosed on the basis of both a peripheral blood and bone marrow examination. An inguinal lymph node biopsy, on the other hand, revealed EBV-positive cytotoxic T-cell lymphoma plus the presence of a small number of EBV-positive ANKL cells, and a diagnosis of EBV-positive composite lymphoma was made. Both the cytotoxic T-cell lymphoma and ANKL exhibited EBV terminal repeat (Southern blot analysis) monoclonal patterns, and they were almost the same size, approximately 9.0 kb. If it was the identical EBV clone, it is possible that EBV infected progenitor cells common to both NK cells and T cells, that the progenitor cells then differentiated into NK cells and T cells, a chronic active Epstein-Barr virus infection developed, and neoplastic transformation occurred. If it was not the identical EBV clone, fairly similar EBVs must have infected NK cells and T cells separately, and they then underwent neoplastic transformation. Because the mechanism by which EBV infects NK cells or T cells is still unknown, we concluded that this case is also important from the standpoint of elucidating it. We are currently in the process of conducting gene analyses to determine whether the fairly similar EBVs that infected the ANKL and cytotoxic T-cell lymphoma are the identical clone.

Epstein-Barr virus-associated lymphoid malignancies: the expanding spectrum of hematopoietic neoplasms

Ubiquitous Epstein-Barr virus (EBV) infects not only B cells but also T and NK cells, and is associated with various lymphoid malignancies. The spectrum of EBV-associated lymphoid malignancies is expanding from Burkitt lymphoma to the newly defined systemic EBV+ T cell lymphoproliferative disease of childhood and hydroa vacciniforme-like lymphoma. However, some EBV-associated malignancies are not defined well and overlap other diseases. Furthermore, the role of EBV in tumorigenesis of lymphoid malignancies is still not clear. Further studies are necessary to clarify the pathogenesis of EBV-associated lymphoid malignancies for a better classification of each disease and for the establishment of effective treatment.