Large Deletion of MAGT1 Gene in a Patient with Classic Kaposi Sarcoma, CD4 Lymphopenia, and EBV Infection

HLH and Recurrent EBV Lymphoma as the presenting manifestation of MAGT1 Deficiency: A Systematic Review of the Expanding Disease Spectrum

Magnesium transporter 1 (MAGT1) gene loss-of-function variants lead to X-linked MAGT1 deficiency with increased susceptibility to EBV infection and N-glycosylation defect (XMEN), a condition with a variety of clinical and immunological effects. In addition, MAGT1 deficiency has been classified as a congenital disorder of glycosylation (CDG) due to its unique role in glycosylation of multiple substrates including NKG2D, necessary for viral protection. Due to the predisposition for EBV, this etiology has been linked with hemophagocytic lymphohistiocytosis (HLH), however only limited literature exists. Here we present a complex case with HLH and EBV-driven classic Hodgkin lymphoma (cHL) as the presenting manifestation of underlying immune defect. However, the patient's underlying immunodeficiency was not identified until his second recurrence of Hodgkin disease, recurrent episodes of Herpes Zoster, and after he had undergone autologous hematopoietic stem cell transplant (HSCT) for refractory Hodgkin lymphoma. This rare presentation of HLH and recurrent lymphomas without some of the classical immune deficiency manifestations of MAGT1 deficiency led us to review the literature for similar presentations and to report the evolving spectrum of disease in published literature. Our systematic review showcased that MAGT1 predisposes to multiple viruses (including EBV) and adds risk of viral-driven neoplasia. The roles of MAGT1 in the immune system and glycosylation were highlighted through the multiple organ dysfunction showcased by the previously validated Immune Deficiency and Dysregulation Activity (IDDA2.1) score and CDG-specific Nijmegen Pediatric CDG Rating Scale (NPCRS) score for the patient cohort in the systematic review.

Adult-onset neurodegeneration in XMEN disease

BACKGROUND

XMEN (X-linked immunodeficiency with magnesium defect, Epstein-Barr virus (EBV), and N-linked glycosylation defect) disease results from loss-of-function mutations in MAGT1, a protein that serves as a magnesium transporter and a subunit of the oligosaccharyltransferase (OST) complex. MAGT1 deficiency disrupts N-linked glycosylation, a critical regulator of immune function. XMEN results in recurrent EBV infections and a propensity for EBV-driven malignancies. Although XMEN is recognized as a systemic congenital disorder of glycosylation (CDG), its neurological involvement is rare and poorly characterized.

CASES

Two young men, ages 32 and 33, are described here with truncating mutations in MAGT1, progressive behavioral changes, and neurodegenerative symptoms. These features manifested well into adulthood. Both patients still presented with many of the molecular and clinical hallmarks of the typical XMEN patient, including chronic EBV viremia and decreased expression of NKG2D.

CONCLUSION

While previously unrecognized, XMEN may include prominent and disabling CNS manifestations. How MAGT1 deficiency directly or indirectly contributes to neurodegeneration remains unclear. Elucidating this mechanism may contribute to the understanding of neurodegeneration more broadly.

Genetics of Primary Hemophagocytic Lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) constitutes a rare, potentially life-threatening hyperinflammatory immune dysregulation syndrome that can present with a variety of clinical signs and symptoms, including fever, hepatosplenomegaly, and abnormal laboratory and immunological findings such as cytopenias, hyperferritinemia, hypofibrinogenemia, hypertriglyceridemia, elevated blood levels of soluble CD25 (interleukin (IL)-2 receptor α-chain), or diminished natural killer (NK)-cell cytotoxicity (reviewed in detail in Chapter 11 of this book). While HLH can be triggered by an inciting event (e.g., infections), certain monogenic causes have been associated with a significantly elevated risk of development of HLH, or recurrence of HLH in patients who have recovered from their disease episode. These monogenic predisposition syndromes are variably referred to as "familial" (FHL) or "primary" HLH (henceforth referred to as "pHLH") and are the focus of this chapter. Conversely, secondary HLH (sHLH) often occurs in the absence of monogenic etiologies that are commonly associated with pHLH and can be triggered by infections, malignancies, or rheumatological diseases; these triggers and the genetics associated with sHLH are discussed in more detail in other chapters in this book.

Today's Kaposi sarcoma is not the same as it was 40 years ago, or is it?

This review will provide an overview of the notion that Kaposi sarcoma (KS) is a disease that manifests under diverse and divergent circumstances. We begin with a historical introduction of KS and KS-associated herpesvirus (KSHV), highlight the diversity of clinical presentations of KS, summarize what we know about the cell of origin for this tumor, explore KSHV viral load as a potential biomarker for acute KSHV infections and KS-associated complications, and discuss immune modulators that impact KSHV infection, KSHV persistence, and KS disease.

How to recognize inborn errors of immunity in a child presenting with a malignancy: guidelines for the pediatric hemato-oncologist

Inborn errors of immunity (IEI) are a group of disorders caused by genetically determined defects in the immune system, leading to infections, autoimmunity, autoinflammation and an increased risk of malignancy. In some cases, a malignancy might be the first sign of an underlying IEI. As therapeutic strategies might be different in these patients, recognition of the underlying IEI by the pediatric hemato-oncologist is important. This article, written by a group of experts in pediatric immunology, hemato-oncology, pathology and genetics, aims to provide guidelines for pediatric hemato-oncologists on how to recognize a possible underlying IEI and what diagnostic tests can be performed, and gives some consideration to treatment possibilities.

Immune checkpoints in T cells during oncogenic γ-herpesvirus infections

Epstein-Barr virus (EBV) and Kaposi sarcoma-associated herpesvirus (KSHV) are two persistent oncogenic γ-herpesviruses with an exclusive tropism for humans. They cause cancers of lymphocyte, epithelial and endothelial cell origin, such as Burkitt's and Hodgkin's lymphoma, primary effusion lymphoma, nasopharyngeal carcinoma, and Kaposi sarcoma. Mutations in immune-related genes but also adverse events during immune checkpoint inhibition in cancer patients have revealed molecular requirements for immune control of EBV and KSHV. These include costimulatory and coinhibitory receptors on T cells that are currently explored or already therapeutically targeted in tumor patients. This review discusses these co-receptors and their influence on EBV- and KSHV-associated diseases. The respective studies reveal surprising specificities of some of these receptors for immunity to these tumor viruses, benefits of their blockade for some but not other virus-associated diseases, and that EBV- and KSHV-specific immune control should be monitored during immune checkpoint inhibition to prevent adverse events that might be associated with their reactivation during treatment.

CD5 B-Cell Predominant Primary Immunodeficiency: Part of the Spectrum of MAGT1 Deficiency

Background

Selective anti-polysaccharide antibody deficiency (SPAD) with CD5 B-cell predominance and autoimmune phenomena was identified in a male cohort first reported by Antall et al in 1999. The phenotypically likewise and genotypically identical X-linked immunodeficiency with magnesium defect, Epstein-Barr Virus infection, and neoplasia (XMEN) disease was defined as a novel primary immunodeficiency (PID) in 2011. Recent studies of the magnesium transporter 1 (MAGT1) gene mutation reveal glycosylation defects contributing to more phenotypic variance than the "XMEN" title pathologies. The updated title, "X-linked MAGT1 deficiency with increased susceptibility to EBV-infection and N-linked glycosylation defect," was proposed in 2020.

Objectives

To reflect the patient population more accurately, a prospective classification update may consider MAGT1 glycobiological errors contributing to phenotypic variance but also pre-genetic testing era reports with CD5 B-cell predominance.

Methods

Patient 1 from Antall et al presented at 28 years of age for further immunological evaluation of his CD5/CD19 B-cell predominance diagnosed at 5 years old.

Design

Immune re-evaluation done through flow cytometry and next-generation sequencing.

Results

Flow cytometry B-cell phenotyping revealed persistent CD5+CD19+ (93%). Flow cytometric histogram quantified reduced activator CD16+CD56+ natural killer and CD8+ T-cell receptor, Group 2, Member D (NKG2D) glycoprotein expression. A c.923-1_934 deletion loss of function mutation was identified in the MAGT1 gene.

Conclusion

We suggest the novel PID XMEN, based on its CD5 B-cell predominance, had been discovered and reported over a decade earlier as CD5+ PID based on the MAGT1 mutation found in the same. We encourage consideration of combining these labels and recent findings to offer the most accurate classification of this disease.

Identification of a novel MAGT1 mutation supports a diagnosis of XMEN disease

XMEN (X-linked immunodeficiency with magnesium defect) is caused by loss-of-function mutations in MAGT1 which is encoded on the X chromosome. The disorder is characterised by CD4 lymphopenia, severe chronic viral infections and defective T-lymphocyte activation. XMEN patients are susceptible to Epstein-Barr virus infections and persistently low levels of intracellular Mg²⁺. Here we describe a patient that presented with multiple recurrent infections and a subsequent diffuse B-cell lymphoma. Molecular genetic analysis by exome sequencing identified a novel hemizygous MAGT1 nonsense mutation c.1005T>A (NM_032121.5) p.(Cys335*), confirming a diagnosis of XMEN deficiency. Follow-up immunophenotyping was performed by antibody staining and flow cytometry; proliferation was determined by ³H-thymidine uptake after activation by PHA and anti-CD3. Cytotoxic natural killer cell activity was assessed with K562 target cells using the NKTEST^TM assay. While lymphocyte populations were superficially intact, B cells were largely naive with a reduced memory cell compartment. Translated NKG2D was absent on both NK and T cells in the proband, and normally expressed in the carrier mother. In vitro NK cell activity was intact in both the proband and his mother. This report adds to the growing number of identified XMEN cases, raising awareness of a, still rare, X-linked immunodeficiency.

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.

Further Delineation of the Spectrum of XMEN Disease in Six Chinese Pediatric Patients

X-linked MAGT1 deficiency with increased susceptibility to EBV-infection and N-linked glycosylation defect (XMEN) disease is a primary immunodeficiency caused by loss-of-function variants in the MAGT1 gene. Only two patients from one family have been diagnosed with XMEN in China. In this study, we retrospectively analyzed the genetic, clinical, and immunological characteristics of six pediatric patients in a Chinese cohort. Medical records were retrieved, immunological phenotypes were assessed, and infectious microbes in patients were detected. Six male patients (mean age, 6.3 years) from five unrelated families were genetically diagnosed as XMEN. Five patients presented with a major complaint of elevated liver enzymes, while one patient was referred for recurrent fever, cough and skin rash. Five patients developed EBV viremia, and one patient developed non-Hodgkin’s lymphoma. Histopathological findings from liver biopsy tissues showed variable hepatic steatosis, fibrosis, inflammatory infiltration, and glycogenosis. Immune phenotypes included CD4 T-cell lymphopenia, elevated B cells, inverted CD4/CD8 ratios, and elevated αβDNTs. No pathogenic microbes other than EBV were identified in these patients. This study reports the clinical and molecular features of Chinese patients with XMEN. For patients with transaminase elevation, chronic EBV infection and EBV-associated lymphoproliferative disease, the possibility of XMEN should be considered in addition to isolated liver diseases.

MAGT1 is required for HeLa cell proliferation through regulating p21 expression, S-phase progress, and ERK/p38 MAPK MYC axis

Magnesium transporter subtype 1 (MAGT1) is known to participate in animal development and cell differentiation. Thus far, MAGT1 studies have mainly focused on its role in cardiomyocyte regulation and differentiation; only a few studies have demonstrated its role in cell proliferation. To investigate the underlying mechanism of MAGT1 in cell proliferation, HeLa and SiHa cells were transiently knocked down with different siRNAs. We showed that cell proliferation was substantially restricted by S-phase arrest and apoptosis in the MAGT1-knocked down cells, which was further confirmed by the increased expression of p21, cyclin-A1, and cyclin-B1, as well as the decreased expression of MYC, cyclin-D1, cyclin-E1, and CDK2. MAGT1 knockdown also resulted in significant changes in the transcriptional expression of 1,598 genes that were analyzed by RNA sequencing. Bioinformatics analysis showed that MAGT1 was related to the MAPK signaling pathway. Western blot analysis confirmed that the phosphorylation of extracellular signal-related protein kinase 1/2 (ERK1/2) and p38 was remarkably reduced in MAGT1 down-regulated groups. Additionally, MAGT1 was required for the function of viral proteins E6/E7 during cell proliferation and G1/S cell-cycle progression. Therefore, MAGT1 plays a crucial role in the proliferation of HPV-positive cervical cancer cells, S-phase progression, and the ERK/p38 MAPK signaling pathway. These results indicate the potential of MAGT1 as a novel target for anticancer research.Abbreviations: MAGT1: Magnesium transporter subtype 1; MAPK: Mitogen-activated protein kinase; XMEN: X-linked immunodeficiency with Magnesium defect, Epstein-Barr virus infection and Neoplasia; BMMSCs: Bone Marrow Mesenchymal Stem Cells; Dpp: Decapentaplegic; CDKIs: CDK inhibitors; GPCR: G-protein coupled receptor; GO: Gene Ontology; KEGG: Kyoto Encyclopedia of Genes and Genomes; RTK: Receptor Tyrosine Kinase; PTK: Protein Tyrosine Kinase; FGFR: Fibroblast Growth Factor Receptor; BMP: Bone Morphogenetic Protein; HPV18 E6/E7: Human Papillomavirus 18 Early protein 6/ early protein 7; FACS: Fluorescence Activated Cell Sorting; PI: Propidium Iodide.

Human inborn errors of immunity to oncogenic viruses

Oncoviruses are viruses that can cause tumors. Seven viruses are currently recognized as oncogenic in humans: Epstein Barr virus (EBV), Kaposi sarcoma-associated herpesvirus (KSHV, also known as HHV8), human papillomaviruses (HPVs), hepatitis B virus (HBV), hepatitis C virus (HCV), human T-lymphotropic virus-1 (HTLV-1), and Merkel cell polyomavirus (MCPyV). The clinical phenotypes resulting from infection with these oncoviruses range from asymptomatic infection to invasive cancers. Patients with inborn errors of immunity (IEI) are prone to the development of infectious diseases caused by a narrow or broad spectrum of pathogens, including oncoviruses in some cases. Studies of patients with IEI have deepened our understanding of the non-redundant mechanisms underlying the control of EBV, HHV8 and HPV infections. The human genetic factors conferring predisposition to oncogenic HBV, HCV, HTLV-1 and MCPyV manifestations remain elusive. We briefly review here what is currently known about the IEI conferring predisposition to severe infection with oncoviruses.

Altered NK-cell compartment and dysfunctional NKG2D/NKG2D-ligand axis in patients with ataxia-telangiectasia

Ataxia-telangiectasia (A-T) is a multisystem disorder caused by biallelic pathogenic variants in the gene encoding A-T mutated (ATM) kinase, a master regulator of the DNA damage response (DDR) pathway. Most A-T patients show cellular and/or humoral immunodeficiency that has been associated with cancer risk and reduced survival, but NK cells have not been thoroughly studied. Here we investigated NK cells of A-T patients with a special focus on the NKG2D receptor that triggers cytotoxicity upon engagement by its ligands (NKG2DLs) commonly induced via the DDR pathway on infected, transformed, and variously stressed cells. Using flow cytometry, we examined the phenotype and function of NK cells in 6 A-T patients as compared with healthy individuals. NKG2D expression was evaluated also by western blotting and RT-qPCR; plasma soluble NKG2DLs (sMICA, sMICB, sULBP1, ULBP2) were measured by ELISA. Results showed that A-T NK cells were skewed towards the CD56^neg anergic phenotype and displayed decreased expression of NKG2D and perforin. NKG2D was reduced at the protein but not at the mRNA level and resulted in impaired NKG2D-mediated cytotoxicity in 4/6 A-T patients. Moreover, in A-T plasma we found 24-fold and 2-fold increase of sMICA and sULBP1, respectively, both inversely correlated with NKG2D expression. Overall, NK cells are disturbed in A-T patients showing reduced NKG2D expression, possibly caused by persistent engagement of its ligands, that may contribute to susceptibility to cancer and infections and represent novel targets for therapeutic interventions.

Genetic predisposition to lymphomas: Overview of rare syndromes and inherited familial variants

Approximately 10 % of malignancies occur in carriers of germline mutations predisposing to cancer. A high risk of developing lymphomas has been noted in many primary immunodeficiencies, including DNA repair disorders. Moreover, implementation of next-generation sequencing has recently enabled to uncover rare genetic variants predisposing patients to lymphoid neoplasms. Some patients harboring inherited predisposition to lymphomas require dedicated clinical management, which will contribute to effective cancer treatment and to the prevention of potential severe toxicities and secondary malignancies. In line with that, our review summarizes the natural history of lymphoid tumors developing on different germline genetic backgrounds and discusses the progress that has been made toward successfully treating these malignancies.

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.

The Role of Lytic Infection for Lymphomagenesis of Human γ-Herpesviruses

Epstein Barr virus (EBV) and Kaposi sarcoma associated herpesvirus (KSHV) are two oncogenic human γ-herpesviruses that are each associated with 1-2% of human tumors. They encode bona fide oncogenes that they express during latent infection to amplify their host cells and themselves within these. In contrast, lytic virus particle producing infection has been considered to destroy host cells and might be even induced to therapeutically eliminate EBV and KSHV associated tumors. However, it has become apparent in recent years that early lytic replication supports tumorigenesis by these two human oncogenic viruses. This review will discuss the evidence for this paradigm change and how lytic gene products might condition the microenvironment to facilitate EBV and KSHV associated tumorigenesis.

MAGT1 messenger RNA-corrected autologous T and natural killer cells for potential cell therapy in X-linked immunodeficiency with magnesium defect, Epstein-Barr virus infection and neoplasia disease

BACKGROUND AIM

X-linked MAGT1 deficiency with increased susceptibility to EBV-infection and N-linked glycosylation defect' (XMEN) disease is caused by mutations in the magnesium transporter 1 (MAGT1) gene. Loss of MAGT1 function results in a glycosylation defect that abrogates expression of key immune proteins such as the NKG2D receptor on CD8⁺ T and NK cells, which is critical for the recognition and killing of virus-infected and transformed cells, a biomarker for MAGT1 function. Patients with XMEN disease frequently have increased susceptibility to EBV infections and EBV-associated B cell malignancies, for which no specific treatment options are currently available. Experimental transfer of donor EBV-specific cytotoxic T cells may be beneficial but carries the risks of eliciting alloimmune responses. An approach for cell therapy to address viral infections and associated complications that avoids the risks of alloimmunity is needed.

METHODS

Here the authors assess the feasibility and efficiency of correcting autologous lymphocytes from XMEN patients by MAGT1 mRNA electroporation (EP) that avoids genomic integration and can be scaled for clinical application.

RESULTS AND CONCLUSIONS

Restoration of NKG2D expression was demonstrated in XMEN patient lymphocytes after MAGT1 mRNA electroporation that reach healthy donor levels in CD8⁺ T and NK cells at 1-2 days after EP. NKG2D expression persisted at ∼50% for 2 weeks after EP. Functionally, mRNA-correction of XMEN NK cells rescued cytotoxic activity also to healthy donor NK cell level. The restored NKG2D receptor expression and function were unaffected by cryopreservation, which will make feasible repeat infusions of MAGT1 mRNA-corrected autologous XMEN CD8⁺ T and NK cells for potential short term therapy for XMEN patients without the risks of alloimmunization.

Congenital disorders of glycosylation: Still "hot" in 2020

BACKGROUND

Congenital disorders of glycosylation (CDG) are inherited metabolic diseases caused by defects in the genes important for the process of protein and lipid glycosylation. With the ever growing number of the known subtypes and discoveries regarding the disease mechanisms and therapy development, it remains a very active field of study.

SCOPE OF REVIEW

This review brings an update on the CDG-related research since 2017, describing the novel gene defects, pathobiomechanisms, biomarkers and the patients' phenotypes. We also summarize the clinical guidelines for the most prevalent disorders and the current therapeutical options for the treatable CDG.

MAJOR CONCLUSIONS

In the majority of the 23 new CDG, neurological involvement is associated with other organ disease. Increasingly, different aspects of cellular metabolism (e.g., autophagy) are found to be perturbed in multiple CDG.

GENERAL SIGNIFICANCE

This work highlights the recent trends in the CDG field and comprehensively overviews the up-to-date clinical recommendations.

Primary immunodeficiencies reveal the molecular requirements for effective host defense against EBV infection

Epstein-Barr virus (EBV) is an enigma; on one hand, it infects and persists in latent form in the vast majority of the global population, causing relatively benign disease in otherwise healthy individuals. On the other hand, EBV represents the first identified oncogenic virus, capable of causing ≥7 different types of malignancies, usually in immunocompromised individuals. Furthermore, some individuals with defined inborn errors of immunity exhibit extreme susceptibility to EBV-induced disease, developing severe and often fatal infectious mononucleosis, hemophagocytic lymphohistiocytosis, lymphoproliferative disease, and/or EBV+ B-cell lymphoma. Thus, host and pathogen have coevolved to enable viral persistence and survival with minimal collateral damage to the healthy host. However, acquired or genetic disruptions to host defense that tip the balance in favor of EBV can have catastrophic effects. The study of primary immunodeficiencies has provided opportunities to define nonredundant requirements for host defense against EBV infection. This has not only revealed mechanisms underlying EBV-induced disease in these primary immunodeficiencies but also identified molecules and pathways that could be targeted to enhance the efficacy of an EBV-specific vaccine or treat severe EBV infection and pathological consequences in immunodeficient hosts.

An Update on XMEN Disease

“X-linked immunodeficiency with magnesium defect, Epstein-Barr virus (EBV) infection, and neoplasia” (XMEN) disease is an inborn error of glycosylation and immunity caused by loss of function mutations in the magnesium transporter 1 (MAGT1) gene. It is a multisystem disease that strongly affects certain immune cells. MAGT1 is now confirmed as a non-catalytic subunit of the oligosaccharyltransferase complex and facilitates Asparagine (N)-linked glycosylation of specific substrates, making XMEN a congenital disorder of glycosylation manifesting as a combined immune deficiency. The clinical disease has variable expressivity and impaired glycosylation of key MAGT1-dependent glycoproteins in addition to Mg²⁺ abnormalities can explain some of the immune manifestations. NKG2D, an activating receptor critical for cytotoxic function against EBV, is poorly glycosylated and invariably decreased on CD8⁺ T cells and natural killer (NK) cells from XMEN patients. It is the best biomarker of the disease. The characterization of EBV-naïve XMEN patients has clarified features of the genetic disease that were previously attributed to EBV infection. Extra-immune manifestations, including hepatic and neurological abnormalities have recently been reported. EBV-associated lymphomas remain the main cause of severe morbidity. Unfortunately, treatment options to address the underlying mechanism of disease remain limited and Mg²⁺ supplementation has not proven successful. Here, we review the expanding clinical phenotype and recent advances in glycobiology that have increased our understanding of XMEN disease. We also propose updating XMEN to “X-linked MAGT1 deficiency with increased susceptibility to EBV-infection and N-linked glycosylation defect” in light of these novel findings.

Immunosuppressive FK506 treatment leads to more frequent EBV-associated lymphoproliferative disease in humanized mice

Post-transplant lymphoproliferative disorder (PTLD) is a potentially fatal complication after organ transplantation frequently associated with the Epstein-Barr virus (EBV). Immunosuppressive treatment is thought to allow the expansion of EBV-infected B cells, which often express all eight oncogenic EBV latent proteins. Here, we assessed whether HLA-A2 transgenic humanized NSG mice treated with the immunosuppressant FK506 could be used to model EBV-PTLD. We found that FK506 treatment of EBV-infected mice led to an elevated viral burden, more frequent tumor formation and diminished EBV-induced T cell responses, indicative of reduced EBV-specific immune control. EBV latency III and lymphoproliferation-associated cellular transcripts were up-regulated in B cells from immunosuppressed animals, akin to the viral and host gene expression pattern found in EBV-PTLD. Utilizing an unbiased gene expression profiling approach, we identified genes differentially expressed in B cells of EBV-infected animals with and without FK506 treatment. Upon investigating the most promising candidates, we validated sCD30 as a marker of uncontrolled EBV proliferation in both humanized mice and in pediatric patients with EBV-PTLD. High levels of sCD30 have been previously associated with EBV-PTLD in patients. As such, we believe that humanized mice can indeed model aspects of EBV-PTLD development and may prove useful for the safety assessment of immunomodulatory therapies.

Magnesium: The overlooked electrolyte in blood cancers?

Magnesium is an important element that has essential roles in the regulation of cell growth, division, and differentiation. Mounting evidence in the literature suggests an association between hypomagnesemia and all-cause mortality. In addition, epidemiologic studies have demonstrated that a diet poor in magnesium increases the risk of developing cancer, highlighting its importance in the field of hematology and oncology. In solid malignancies, hypomagnesemia at diagnosis portends a worse prognosis. However, little is known about prognosis in patients with hypomagnesemia and blood cancers in general; lymphoma more specifically. Hypomagnesemia has been associated with a higher viral load of the Epstein Barr virus, a virus associated with a multitude of hematologic malignancies. The role of magnesium in the immune system has been further elucidated in studies of patients with a rare primary immunodeficiency known as XMEN disease (X-linked immunodeficiency with Magnesium defect, Epstein-Barr virus (EBV) infection, and Neoplasia disease). These patients have a mutation in the MAGT1 gene, which codes for a magnesium transporter. The mutation leads to impaired T cell activation and an increased risk of developing hematologic malignancies. In this review we discuss the relevance of magnesium as an electrolyte, current measurement techniques, and the known data related to cause and prognosis of blood cancers. The goal is to use these data to stimulate additional high-quality and well powered studies to further investigate the role of magnesium in preventing cancer and improving outcomes of patients with malignancy and concomitant magnesium deficiency.

Genetic susceptibility to EBV infection: insights from inborn errors of immunity

Epstein-Barr virus (EBV) is a ubiquitous human pathogen, infecting > 90% of the adult population. In the vast majority of healthy individuals, infection with EBV runs a relatively benign course. However, EBV is by no means a benign pathogen. Indeed, apart from being associated with at least seven different types of malignancies, EBV infection can cause severe and often fatal diseases-hemophagocytic lymphohistiocytosis, lymphoproliferative disease, B-cell lymphoma-in rare individuals with specific monogenic inborn errors of immunity. The discovery and detailed investigation of inborn errors of immunity characterized by heightened susceptibility to, or increased frequency of, EBV-induced disease have elegantly revealed cell types and signaling pathways that play critical and non-redundant roles in host-defense against EBV. These analyses have revealed not only mechanisms underlying EBV-induced disease in rare genetic conditions, but also identified molecules and pathways that could be targeted to treat severe EBV infection and pathological consequences in immunodeficient hosts, or even potentially enhance the efficacy of an EBV-specific vaccine.

Signaling pathways involved in the T-cell-mediated immunity against Epstein-Barr virus: Lessons from genetic diseases

Primary immunodeficiencies (PIDs) provide researchers with unique models to understand in vivo immune responses in general and immunity to infections in particular. In humans, impaired immune control of Epstein-Barr virus (EBV) infection is associated with the occurrence of several different immunopathologic conditions; these include non-malignant and malignant B-cell lymphoproliferative disorders, hemophagocytic lymphohistiocytosis (HLH), a severe inflammatory condition, and a chronic acute EBV infection of T cells. Studies of PIDs associated with a predisposition to develop severe, chronic EBV infections have led to the identification of key components of immunity to EBV - notably the central role of T-cell expansion and its regulation in the pathophysiology of EBV-associated diseases. On one hand, the defective expansion of EBV-specific CD8 T cells results from mutations in genes involved in T-cell activation (such as RASGRP1, MAGT1, and ITK), DNA metabolism (CTPS1) or co-stimulatory pathways (CD70, CD27, and TNFSFR9 (also known as CD137/4-1BB)) leads to impaired elimination of proliferating EBV-infected B cells and the occurrence of lymphoma. On the other hand, protracted T-cell expansion and activation after the defective killing of EBV-infected B cells is caused by genetic defects in the components of the lytic granule exocytosis pathway or in the small adapter protein SH2D1A (also known as SAP), a key activator of T- and NK cell-cytotoxicity. In this setting, the persistence of EBV-infected cells results in HLH, a condition characterized by unleashed T-cell and macrophage activation. Moreover, genetic defects causing selective vulnerability to EBV infection have highlighted the role of co-receptor molecules (CD27, CD137, and SLAM-R) selectively involved in immune responses against infected B cells via specific T-B cell interactions.

Defective glycosylation and multisystem abnormalities characterize the primary immunodeficiency XMEN disease

X-linked immunodeficiency with magnesium defect, EBV infection, and neoplasia (XMEN) disease are caused by deficiency of the magnesium transporter 1 (MAGT1) gene. We studied 23 patients with XMEN, 8 of whom were EBV naive. We observed lymphadenopathy (LAD), cytopenias, liver disease, cavum septum pellucidum (CSP), and increased CD4-CD8-B220-TCRαβ+ T cells (αβDNTs), in addition to the previously described features of an inverted CD4/CD8 ratio, CD4+ T lymphocytopenia, increased B cells, dysgammaglobulinemia, and decreased expression of the natural killer group 2, member D (NKG2D) receptor. EBV-associated B cell malignancies occurred frequently in EBV-infected patients. We studied patients with XMEN and patients with autoimmune lymphoproliferative syndrome (ALPS) by deep immunophenotyping (32 immune markers) using time-of-flight mass cytometry (CyTOF). Our analysis revealed that the abundance of 2 populations of naive B cells (CD20+CD27-CD22+IgM+HLA-DR+CXCR5+CXCR4++CD10+CD38+ and CD20+CD27-CD22+IgM+HLA-DR+CXCR5+CXCR4+CD10-CD38-) could differentially classify XMEN, ALPS, and healthy individuals. We also performed glycoproteomics analysis on T lymphocytes and show that XMEN disease is a congenital disorder of glycosylation that affects a restricted subset of glycoproteins. Transfection of MAGT1 mRNA enabled us to rescue proteins with defective glycosylation. Together, these data provide new clinical and pathophysiological foundations with important ramifications for the diagnosis and treatment of XMEN disease.

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.

Inherited Immunodeficiencies With High Predisposition to Epstein-Barr Virus-Driven Lymphoproliferative Diseases

Epstein–Barr Virus (EBV) is a gamma-herpes virus that infects 90% of humans without any symptoms in most cases, but has an oncogenic potential, especially in immunocompromised individuals. In the past 30 years, several primary immunodeficiencies (PIDs) associated with a high risk to develop EBV-associated lymphoproliferative disorders (LPDs), essentially consisting of virus-associated hemophagocytic syndrome, non-malignant and malignant B-cell LPDs including non-Hodgkin and Hodgkin’s types of B lymphomas have been characterized. Among them are SH2D1A (SAP), XIAP, ITK, MAGT1, CD27, CD70, CTPS1, RASGRP1, and CORO1A deficiencies. Penetrance of EBV infection ranges from 50 to 100% in those PIDs. Description of large cohorts and case reports has refined the specific phenotypes associated with these PIDs helping to the diagnosis. Specific pathways required for protective immunity to EBV have emerged from studies of these PIDs. SLAM-associated protein-dependent SLAM receptors and MAGT1-dependent NKG2D pathways are important for T and NK-cell cytotoxicity toward EBV-infected B-cells, while CD27–CD70 interactions are critical to drive the expansion of EBV-specific T-cells. CTPS1 and RASGRP1 deficiencies further strengthen that T-lymphocyte expansion is a key step in the immune response to EBV. These pathways appear to be also important for the anti-tumoral immune surveillance of abnormal B cells. Monogenic PIDs should be thus considered in case of any EBV-associated LPDs.

Impaired Control of Epstein-Barr Virus Infection in B-Cell Expansion with NF-κB and T-Cell Anergy Disease

B-cell expansion with NF-κB and T-cell anergy (BENTA) disease is a B-cell-specific lymphoproliferative disorder caused by germline gain-of-function mutations in CARD11. These mutations force the CARD11 scaffold into an open conformation capable of stimulating constitutive NF-κB activation in lymphocytes, without requiring antigen receptor engagement. Many BENTA patients also suffer from recurrent infections, with 7 out of 16 patients exhibiting chronic, low-grade Epstein–Barr virus (EBV) viremia. In this mini-review, we discuss EBV infection in the pathogenesis and clinical management of BENTA disease, and speculate on mechanisms that could explain inadequate control of viral infection in BENTA patients.

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.

Pathogenesis of infections in HIV-infected individuals: insights from primary immunodeficiencies

Following infection with almost any given microorganism other than an emerging pathogen, only a minority of individuals develop life-threatening clinical disease, implying that these individuals have some form of immunodeficiency. A growing number of inherited and acquired immunodeficiencies have been deciphered over the last 50 years. HIV infection is probably the best-known acquired immunodeficiency. It emerged about 40 years ago and precipitates various severe infections, the occurrence of which is associated with a fall in circulating CD4⁺ T cells. However, despite the strength of this correlation, infection rates differ between patients with similar levels and durations of CD4⁺ T lymphopenia in the presence or absence of antiretroviral treatment. Moreover, a few infections seem to be less dependent on total CD4⁺ T-cell levels. The fine detail of the mechanisms underlying these infections is unknown. We discuss here how studies of the human genetics and immunology of some of these infections in patients with primary immunodeficiencies (PIDs) have provided unique insights into their molecular and cellular basis. Defects of specific CD4⁺ Th-cell subsets account for some of these infections, as best exemplified by Th1* for mycobacteriosis and Th17 for candidiasis. PIDs are individually rare, but collectively much more common than initially thought, with new disorders being discovered at an ever-increasing pace and a global prevalence worldwide approaching that of HIV infection. Studies of known and new PIDs should make it possible to dissect the pathogenesis of most human infections at an unprecedented level of molecular and cellular precision. The predictive, preventive, and therapeutic implications of studies of immunity to infection in PIDs may extend to HIV-infected patients and patients with infectious diseases in other settings.

Human immunity against EBV-lessons from the clinic

The mammalian immune system has evolved over many millennia to be best equipped to protect the host from pathogen infection. In many cases, host and pathogen have coevolved, each acquiring sophisticated ways of inducing or protecting from disease. Epstein-Barr virus (EBV) is a human herpes virus that infects >90% of individuals. Despite its ubiquity, infection by EBV is often subclinical; this invariably reflects the necessity of the virus to preserve its host, balanced with sophisticated host immune mechanisms that maintain viral latency. However, EBV infection can result in various, and often fatal, clinical sequelae, including fulminant infectious mononucleosis, hemophagocytic lymphohistiocytosis, lymphoproliferative disease, organomegaly, and/or malignancy. Such clinical outcomes are typically observed in immunosuppressed individuals, with the most extreme cases being Mendelian primary immunodeficiencies (PIDs). Although these conditions are rare, they have provided critical insight into the cellular, biochemical, and molecular requirements for robust and long-lasting immunity against EBV infection. Here, we review the virology of EBV, mechanisms underlying disease pathogenesis in PIDs, and developments in immune cell–mediated therapy to treat disorders associated with or induced by EBV infection.