Late-onset severe chronic active EBV in a patient for five years with mutations in STXBP2 (MUNC18-2) and PRF1 (perforin 1)

Epstein-Barr virus-associated lymphomas decoded

Epstein-Barr virus (EBV)-associated lymphomas cover a range of histological B- and T-cell non-Hodgkin and Hodgkin lymphoma subtypes. The role of EBV on B-cell malignant pathogenesis and its impact on the tumour microenvironment are intriguing but incompletely understood. Both the International Consensus Classification (ICC) and 5th Edition of the World Health Organization (WHO-HAEM5) proposals give prominence to the distinct clinical, prognostic, genetic and tumour microenvironmental features of EBV in lymphoproliferative disorders. There have been major advances in our biological understanding, in how to harness features of EBV and its host immune response for targeted therapy, and in using EBV as a method to monitor disease response. In this article, we showcase the latest developments and how they may be integrated to stimulate new and innovative approaches for further lines of investigation and therapy.

Epstein-Barr virus-associated B-cell lymphoproliferative disorder meeting the definition of CAEBV B cell disease: a case report

BACKGROUND

Chronic active Epstein-Barr virus infection (CAEBV) is a systemic EBV-positive lymphoproliferative disorder (EBV-LPD) considered to be associated with a genetic immunological abnormality, although its cause is still unclear. EBV is usually detected in T cells or NK cells in CAEBV patients with only a few cases involving B cells described in East Asia, which may be due to differences in genetic and environmental factors.

CASE DESCRIPTION

A 16-year-old boy who seemed to be diagnosed as CAEBV of B cell type was studied. The patient had IM-like symptoms persisting for more than 3 months, high levels of EBV DNA in the PB, and positive EBER in situ hybridization in B cells. In addition, to exclude underlying genetic disorders, we performed next-generation sequencing (NGS) and whole-exome sequencing (WES), which identified the missense mutation in PIK3CD (E1021K), ADA (S85L) and CD3D (Q140K) in the patient while no same genetic mutation was detected in his parents and sister. However, there is no diagnosis of CAEBV of B cell type in the most recent World Health Organization classification of tumors of hematopoietic and lymphoid tissues, therefore we finally diagnosed this patient as EBV-B-LPD.

CONCLUSIONS

This study shows a rare case of a patient meeting the definition of CAEBV B-cell disease in East Asia. Meanwhile, the case indicates that the missense mutation and the disease are related.

Natural killer cell responses to human oncogenic γ-herpesvirus infections

The two γ-herpesviruses Epstein Barr virus (EBV) and Kaposi sarcoma associated herpesvirus (KSHV) are each associated with more than 1% of all tumors in humans. While EBV establishes persistent infection in nearly all adult individuals, KSHV benefits from this widespread EBV prevalence for its own persistence. Interestingly, EBV infection expands early differentiated NKG2A⁺KIR^- NK cells that protect against lytic EBV infection, while KSHV co-infection drives accumulation of poorly functional CD56^-CD16⁺ NK cells. Thus persistent γ-herpesvirus infections are sculptors of human NK cell repertoires and the respectively stimulated NK cell subsets should be considered for immunotherapies of EBV and KSHV associated malignancies.

Co-Stimulatory Molecules during Immune Control of Epstein Barr Virus Infection

The Epstein Barr virus (EBV) is one of the prominent human tumor viruses, and it is efficiently immune-controlled in most virus carriers. Cytotoxic lymphocytes strongly expand during symptomatic primary EBV infection and in preclinical in vivo models of this tumor virus infection. In these models and patients with primary immunodeficiencies, antibody blockade or deficiencies in certain molecular pathways lead to EBV-associated pathologies. In addition to T, NK, and NKT cell development, as well as their cytotoxic machinery, a set of co-stimulatory and co-inhibitory molecules was found to be required for EBV-specific immune control. The role of CD27/CD70, 4-1BB, SLAMs, NKG2D, CD16A/CD2, CTLA-4, and PD-1 will be discussed in this review. Some of these have just been recently identified as crucial for EBV-specific immune control, and for others, their important functions during protection were characterized in in vivo models of EBV infection and its immune control. These insights into the phenotype of cytotoxic lymphocytes that mediate the near-perfect immune control of EBV-associated malignancies might also guide immunotherapies against other tumors in the future.

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.

Immune Escape by Non-coding RNAs of the Epstein Barr Virus

Epstein Barr virus (EBV) is one of the most successful pathogens of humans, persistently colonizing more than 95% of the adult human population. At the same time EBV encodes oncogenes that can readily transform human B cells in culture and threaten healthy virus carriers with lymphomagenesis. Cytotoxic lymphocytes have been identified in experimental models and by primary immunodeficiencies as the main protective immune compartments controlling EBV. EBV has reached a stalemate with these cytotoxic T and innate lymphocytes to ensure persistence in most infected humans. Recent evidence suggests that the non-coding RNAs of the virus contribute to viral immune escape to prevent immune eradication. This knowledge might be used in the future to attenuate EBV for vaccine development against this human tumor virus that was discovered more than 55 years ago.

Natural Killer Cell Responses during Human γ-Herpesvirus Infections

Herpesviruses are main sculptors of natural killer (NK) cell repertoires. While the β-herpesvirus human cytomegalovirus (CMV) drives the accumulation of adaptive NKG2C-positive NK cells, the human γ-herpesvirus Epstein–Barr virus (EBV) expands early differentiated NKG2A-positive NK cells. While adaptive NK cells support adaptive immunity by antibody-dependent cellular cytotoxicity, NKG2A-positive NK cells seem to preferentially target lytic EBV replicating B cells. The importance of this restriction of EBV replication during γ-herpesvirus pathogenesis will be discussed. Furthermore, the modification of EBV-driven NK cell expansion by coinfections, including by the other human γ-herpesvirus Kaposi sarcoma-associated herpesvirus (KSHV), will be summarized.

Inherited Genetic Susceptibility to Nonimmunosuppressed Epstein-Barr Virus-associated T/NK-cell Lymphoproliferative Diseases in Chinese Patients

Epstein-Barr virus (EBV) T/NK-cell lymphoproliferative diseases are characterized by clonal expansion of EBV-infected T or NK cells, including chronic active EBV infection of T/NK-cell type (CAEBV+T/NK), EBV-associated hemophagocytic lymphohistiocytosis (EBV+HLH), extranodal NK/T-cell lymphoma of nasal type (ENKTL), and aggressive NK-cell leukemia (ANKL). However, the role of inherited genetic variants to EBV+T/NK-LPDs susceptibility is still unknown. A total of 171 nonimmunosuppressed patients with EBV+T/NK-LPDs and 104 healthy donors were retrospectively collected and a targeted sequencing study covering 15 genes associated with lymphocyte cytotoxicity was performed. The 94 gene variants, mostly located in UNC13D, LYST, ITK, and PRF1 genes were detected, and mutations covered 28/50 (56.00%) of CAEBV-T/NK, 31/51 (60.78%) of EBV+HLH, 13/28 (46.42%) of ENKTL, and 13/48 (27.09%) of ANKL. Most mutations represented monoallelic and missense. Three-year overall survival rate of patients with CAEBV-T/NK and EBV+HLH was significantly lower in patients with germline mutations than in those without germline mutations (P=0.0284, P=0.0137). Our study provided novel insights into understanding a spectrum of nonimmunosuppressed EBV+T/NK-LPDs with respect to genetic defects associated with lymphocyte cytotoxicity and reminded us that the gene sequencing may be an auxiliary test for diagnosis and risk stratification of EBV+T/NK-LPDs.

Germline Compound Heterozygous Variants Identified in the STXBP2 Gene Leading to a Familial Hemophagocytic Lymphohistiocytosis Type 5: A Case Report

Familial hemophagocytic lymphohistiocytosis (FHL) is a rare, potentially fatal autosomal-recessive immunodeficiency, and STXBP2 mutations have been associated with FHL type 5 (FHL-5). Here, we report a case of a 2-year-old boy who presented with recurrent fever, hepatosplenomegaly, pancytopenia, hyperferritinemia, and hypofibrinogenemia since 4 months of age. His genetic analysis revealed a compound heterozygosity of the STXBP2 gene with a described pathogenic mutation, c.1247-1G>C (splicing acceptor site), harbored by his father and a likely pathogenic variant of uncertain significance (VUS), c.704G>A (p.Arg235Gln), harbored by his mother. He was diagnosed as compound heterozygous for FHL-5 and was treated with the HLH-2004 protocol. Since treatment, this patient has been in remission, and he is being evaluated for a hematopoietic stem cell transplantation (HSCT).

Vaccination against the Epstein-Barr virus

Epstein-Barr virus (EBV) was the first human tumor virus being discovered and remains to date the only human pathogen that can transform cells in vitro. 55 years of EBV research have now brought us to the brink of an EBV vaccine. For this purpose, recombinant viral vectors and their heterologous prime-boost vaccinations, EBV-derived virus-like particles and viral envelope glycoprotein formulations are explored and are discussed in this review. Even so, cell-mediated immune control by cytotoxic lymphocytes protects healthy virus carriers from EBV-associated malignancies, antibodies might be able to prevent symptomatic primary infection, the most likely EBV-associated pathology against which EBV vaccines will be initially tested. Thus, the variety of EBV vaccines reflects the sophisticated life cycle of this human tumor virus and only vaccination in humans will finally be able to reveal the efficacy of these candidates. Nevertheless, the recently renewed efforts to develop an EBV vaccine and the long history of safe adoptive T cell transfer to treat EBV-associated malignancies suggest that this oncogenic γ-herpesvirus can be targeted by immunotherapies. Such vaccination should ideally implement the very same immune control that protects healthy EBV carriers.

Chronic Active Epstein-Barr Virus Infection: Is It Immunodeficiency, Malignancy, or Both?

Simple Summary

Chronic active Epstein–Barr virus (EBV) infection (CAEBV) is a rare syndrome of unknown etiology characterized by prolonged infectious mononucleosis-like symptoms and proliferation of EBV-infected T and/or natural killer cells. CAEBV has been primarily reported in East Asia and Latin America, suggesting a genetic predisposition in its pathogenesis. The clinical course of CAEBV is heterogeneous ranging from an indolent and occasionally self-limiting disease to an aggressive and fatal condition, but its prognosis is generally poor. This heterogeneous clinical picture does not suggest a simple etiology for the syndrome. Clinicopathological investigations of CAEBV suggest that it has aspects of both malignant neoplasm and immunodeficiency. This article summarizes the latest findings on CAEBV and discusses critical unsolved questions regarding its pathogenesis and disease concept.

Abstract

Chronic active Epstein–Barr virus (EBV) infection (CAEBV) is a rare syndrome characterized by prolonged infectious mononucleosis-like symptoms and elevated peripheral blood EBV DNA load in apparently immunocompetent persons. CAEBV has been primarily reported in East Asia and Latin America, suggesting a genetic predisposition in its pathogenesis. In most cases of CAEBV, EBV induces proliferation of its unusual host cells, T or natural killer (NK) cells. The clinical course of CAEBV is heterogeneous; some patients show an indolent course, remaining in a stable condition for years, whereas others show an aggressive course with a fatal outcome due to hemophagocytic lymphohistiocytosis, multiple organ failure, or progression to leukemia/lymphoma. The pathogenesis of CAEBV is unclear and clinicopathological investigations suggest that it has aspects of both malignant neoplasm and immunodeficiency. Recent genetic analyses of both viral and host genomes in CAEBV patients have led to discoveries that are improving our understanding of the nature of this syndrome. This article summarizes the latest findings on CAEBV and discusses critical unsolved questions regarding its pathogenesis and disease concept.

Co-Occurrence of Familial Hemophagocytic Lymphohistiocytosis Type 2 and Chronic Active Epstein-Barr Virus in Adulthood

We report, to the best of our best knowledge, the oldest individual to ever be diagnosed with Familial Hemophagocytic Lymphohistiocytosis (FHL) Type 2 from homozygous c.1349C>T (p.T450M) missense variants in the PRF1 gene. This rare case advanced in complexity with a simultaneous diagnosis of Chronic Active Epstein-Barr Virus (CAEBV) - a distinct clinical entity from acute EBV infections and a well-described trigger of Hemophagocytic Lymphohistiocytosis (HLH). This is, to the best of our knowledge, the only individual to ever be diagnosed with CAEBV in the setting of this specific variant and the oldest to be diagnosed with a coexisting perforin variant. This case provides understanding of EBV, human genetics, and lymphoproliferative disorders while adding a unique differential diagnosis to adults who present with fever of unknown origin and diffuse lymphadenopathy without evidence of malignancy. This report explores the diagnosis and treatment of both HLH and CAEBV, encouraging discussion regarding current clinical management and future research needs.

Cytotoxicity in Epstein Barr virus specific immune control

Epstein Barr virus (EBV) is the most common human tumor virus, persistently infecting more than 95% of the human adult population and readily transforming human B cell in culture. Fortunately, only a small minority of EBV carriers develops virus associated malignancies. The majority controls persistent EBV infection with cytotoxic lymphocytes, mainly NK, γδ and CD8⁺ T cells and the characteristics of the required immune responses get more and more defined by primary immunodeficiencies that affect molecules of these cytotoxic lymphocytes and their investigation in mice with reconstituted human immune system components (humanized mice) that are susceptible to EBV infection and associated lymphomagenesis. The gained information should be able to guide us to develop immunotherapies against EBV and tumors in general.

NK-cell post-transplant lymphoproliferative disease with chronic active Epstein-Barr virus infection-like clinical findings

A 69-year-old man who underwent cord blood transplantation seven years ago was admitted because of fever, elevated liver enzymes and thrombocytopenia. Bone marrow aspirate revealed hemophagocytic lymphohistiocytosis. Viral capsid antigen (VCA)-immunoglobulin (Ig) G, VCA-IgM, VCA-IgA, Epstein-Barr virus nuclear antigen-IgG, early antigen-diffuse-type and restricted-type (EA-DR) IgG, and EA-DR IgA titers were 2560, <10, 10, 40, 40, and <10, respectively. Real-time polymerase chain reaction assay of peripheral whole blood for Epstein-Barr virus-deoxyribonucleic acid (EBV-DNA) revealed 240,000 copies/μg DNA. Flow cytometric in situ hybridization assay confirmed that EBV-infected cells were NK-cells. Clonality evaluation by Southern blot assay of EBV-DNA terminal repeats proved to be bi-clonal. Accordingly, we made a diagnosis of NK-cell post-transplant lymphoproliferative disease with chronic active EBV infection-like clinical findings (CAEBV-like NK-cell PTLD). Although CAEBV-like PTLD is extremely rare, its prognosis seems to be very poor. The disease should be considered in such patients who present persistent or recurrent infectious mononucleosis-like symptoms after transplantation.

Immunodeficiencies that predispose to pathologies by human oncogenic γ-herpesviruses

Human γ-herpesviruses include the closely related tumor viruses Epstein Barr virus (EBV) and Kaposi sarcoma-associated herpesvirus (KSHV). EBV is the most growth-transforming pathogen known and is linked to at least seven human malignancies. KSHV is also associated with three human cancers. Most EBV- and KSHV-infected individuals fortunately remain disease-free despite persistent infection and this is likely due to the robustness of the immune control that they mount against these tumor viruses. However, upon immune suppression EBV- and KSHV-associated malignancies emerge at increased frequencies. Moreover, primary immunodeficiencies with individual mutations that predispose to EBV or KSHV disease allow us to gain insights into a catalog of molecules that are required for the immune control of these tumor viruses. Curiously, there is little overlap between the mutation targets that predispose individuals to EBV versus KSHV disease, even so both viruses can infect the same host cell, human B cells. These differences will be discussed in this review. A better understanding of the crucial components in the near-perfect life-long immune control of EBV and KSHV should allow us to target malignancies that are associated with these viruses, but also induce similar immune responses against other tumors.

Epstein-Barr Virus-Associated γδ T-Cell Lymphoproliferative Disorder Associated With Hypomorphic IL2RG Mutation

Chronic active Epstein-Barr virus (EBV) infection (CAEBV) is an EBV-associated lymphoproliferative disease characterized by repeated or sustainable infectious mononucleosis (IM)-like symptoms. EBV is usually detected in B cells in patients who have IM or Burkitt's lymphoma and even in patients with X-linked lymphoproliferative syndrome, which is confirmed to have vulnerability to EBV infection. In contrast, EBV infects T cells (CD4⁺ T, CD8⁺ T, and γδT) or NK cells mono- or oligoclonally in CAEBV patients. It is known that the CAEBV phenotypes differ depending on which cells are infected with EBV. CAEBV is postulated to be associated with a genetic immunological abnormality, although its cause remains undefined. Here we describe a case of EBV-related γδT-cell proliferation with underlying hypomorphic IL2RG mutation. The immunological phenotype consisted of γδT-cell proliferation in the peripheral blood. A presence of EBV-infected B cells and γδT cells mimicked γδT-cell-type CAEBV. Although the patient had normal expression of CD132 (common γ chain), the phosphorylation of STAT was partially defective, indicating impaired activation of the downstream signal of the JAK/STAT pathway. Although the patient was not diagnosed as having CAEBV, this observation shows that CAEBV might be associated with immunological abnormality.

Chronic Active Epstein-Barr Virus Disease

Chronic active Epstein–Barr virus (CAEBV) disease is a rare disorder in which persons are unable to control infection with the virus. The disease is progressive with markedly elevated levels of EBV DNA in the blood and infiltration of organs by EBV-positive lymphocytes. Patients often present with fever, lymphadenopathy, splenomegaly, EBV hepatitis, or pancytopenia. Over time, these patients develop progressive immunodeficiency and if not treated, succumb to opportunistic infections, hemophagocytosis, multiorgan failure, or EBV-positive lymphomas. Patients with CAEBV in the United States most often present with disease involving B or T cells, while in Asia, the disease usually involves T or NK cells. The only proven effective treatment for the disease is hematopoietic stem cell transplantation. Current studies to find a cause of this disease focus on immune defects and genetic abnormalities associated with the disease.

Epstein-Barr Virus-Specific Immune Control by Innate Lymphocytes

Epstein–Barr virus (EBV) is a potent B cell transforming pathogen in humans. In most persistently EBV-infected individuals, potent cytotoxic lymphocyte responses prevent EBV-associated pathologies. In addition to comprehensive adaptive T cell responses, several innate lymphocyte populations seem to target different stages of EBV infection and are compromised in primary immunodeficiencies that render individuals susceptible to symptomatic EBV infection. In this mini-review, I will highlight the functions of natural killer, γδ T cells, and natural killer T cells during innate immune responses to EBV. These innate lymphocyte populations seem to restrict both lytic replication and transforming latent EBV antigen expression. The mechanisms underlying the recognition of these different EBV infection programs by the respective innate lymphocytes are just starting to become unraveled, but will provide immunotherapeutic strategies to target pathologies that are associated with the different EBV infection programs.

Recurrent scarring papulovesicular lesions on sun-exposed skin in a 22-year-old man

KEY TEACHING POINTS.

MPEG1/perforin-2 mutations in human pulmonary nontuberculous mycobacterial infections

Perforin-2 is a highly conserved pore-forming protein encoded by macrophage expressed gene 1 (MPEG1). A number of studies have shown that Perforin-2-deficient mice are unable to survive following a bacterial challenge that is nonlethal in WT mice. There is also recent evidence that Mpeg1+/- heterozygous mice display an intermediate killing ability compared with Mpeg1 WT and Mpeg1-/- mice. Despite these in vivo findings, to date, no perforin-2 deficiencies have been associated with human disease. Here, we report four patients with persistent nontuberculous mycobacterial infection who had heterozygous MPEG1 mutations. In vitro, neutrophils, macrophages, and B cells from these patients were unable to kill Mycobacterium avium as efficiently as normal controls. CRISPR mutagenesis validated the deleterious antibacterial activity of these mutations. These data suggest that perforin-2 haploinsufficiency may contribute to human susceptibility to infections with intracellular bacteria.

Pathophysiology and epidemiology of hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a syndrome characterized by extreme immune activation, resulting in pathologic inflammation. The diagnosis includes a spectrum of inherited or acquired defects in cytotoxic lymphocyte function, often with uncontrolled infections. HLH may also arise as the result of persistent antigen stimulation due to autoimmune disease or malignancy. HLH is often described in binary terms as "primary," indicating Mendelian inheritance of gene mutations resulting in cytotoxic lymphocyte dysfunction, or "secondary" indicating an acquired reactive disorder. Increasing evidence describes HLH as more complex phenomenon, resulting from specific immune challenges in patients with a susceptible genetic background. Early recognition of HLH and evaluation of potential causes is critically important, as survival generally requires urgent treatment with immune suppression and resolution of the activating antigen. However, the diagnosis of HLH is challenged by the myriad of pathways that lead to pathologic inflammation and the clinical overlap with other conditions. Further improvements in therapy will require prospective trials to define optimal strategies for each patient based on the individual paths that lead to pathologic inflammation.

Primary Immunodeficiencies Associated with EBV Disease

Epstein-Barr virus (EBV) infects nearly all humans and usually is asymptomatic, or in the case of adolescents and young adults, it can result in infectious mononucleosis. EBV-infected B cells are controlled primarily by NK cells, iNKT cells, CD4 T cells, and CD8 T cells. While mutations in proteins important for B cell function can affect EBV infection of these cells, these mutations do not result in severe EBV infection. Some genetic disorders affecting T and NK cell function result in failure to control EBV infection, but do not result in increased susceptibility to other virus infections. These include mutations in SH2D1A, BIRC4, ITK, CD27, MAGT1, CORO1A, and LRBA. Since EBV is the only virus that induces proliferation of B cells, the study of these diseases has helped to identify proteins critical for interactions of T and/or NK cells with B cells. Mutations in three genes associated with hemophagocytic lymphohistocytosis, PRF1, STXBP2, and UNC13D, can also predispose to severe chronic active EBV disease. Severe EBV infection can be associated with immunodeficiencies that also predispose to other viral infections and in some cases other bacterial and fungal infections. These include diseases due to mutations in PIK3CD, PIK3R1, CTPS1, STK4, GATA2, MCM4, FCGR3A, CARD11, ATM, and WAS. In addition, patients with severe combined immunodeficiency, which can be due to mutations in a number of different genes, are at high risk for various infections as well as EBV B cell lymphomas. Identification of proteins important for control of EBV may help to identify new targets for immunosuppressive therapies.