Epstein-Barr virus-induced diseases in boys with the X-linked lymphoproliferative syndrome (XLP): update on studies of the registry

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.

Two Clonally Distinct B-Cell Lymphomas Reveal the Diagnosis of XLP1 in a Male Child and His Asymptomatic Male Relatives: Case Report and Review of the Literature

X-linked lymphoproliferative disease type 1 (XLP1) is a primary immunodeficiency disorder caused by pathogenic variants in the SH2D1A gene (SH2 domain containing protein 1A). Patients with XLP1 may present acutely with fulminant infectious mononucleosis, hemophagocytic lymphohistiocytosis, and/or B-cell non-Hodgkin lymphoma (B-NHL). We report a boy who developed 2 clonally distinct B-NHL 4 years apart and was found to have previously unrecognized XLP1. The report highlights the importance of clonal analysis and XLP1 testing in males with presumed late recurrences of B-NHL, and the role of allogeneic stem cell transplant (allo-SCT) in XLP1 patients and their affected male relatives.

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.

The SLAM family receptors: Potential therapeutic targets for inflammatory and autoimmune diseases

The signaling lymphocytic activation molecule (SLAM) family is comprised of nine distinct receptors (SLAMF1 through SLAMF9) that are expressed on hematopoietic cells. All of these receptors, with the exception of SLAMF4, are homotypic by nature as downstream signaling occurs when hematopoietic cells that express the same SLAM receptor interact. The SLAM family receptor function is largely controlled via SLAM associated protein (SAP) family adaptors. The SAP family adaptors consist of SAP, Ewing sarcoma associated transcript (EAT)-2, and EAT-2-related transducer (ERT). These adaptors associate with the cytoplasmic domain of the SLAM family receptors through phosphorylated tyrosines. Defects in SLAM family members and SAP adaptors have been implicated in causing immune deficiencies. This is exemplified in patients with X-linked lymphoproliferative (XLP) disease, where SAP undergoes a loss of function mutation. Furthermore, evidence has been accumulating that SLAM family members are potential targets for inflammatory and autoimmune diseases. This review will discuss the structure and function of the SLAM family receptors and SAP family adaptors, their role in immune regulation, and potential approaches to target this family of receptors therapeutically.

Two Unrelated Burkitt Lymphomas Seven Years Apart in a Patient With X-Linked Lymphoproliferative Disease Type 1 (XLP1)

OBJECTIVES

We describe a rare case of a male child with X-linked lymphoproliferative disease type 1 (XLP1) who presented with Burkitt lymphoma (BL) when he was 6 years old, achieved a complete response to therapy, and developed a second BL after seven years.

METHODS

Diagnostic H&E stained slides and ancillary studies were reviewed for both lymphomas. B-cell clonality by PCR and SNP array studies were performed on both specimens.

RESULTS

Both lymphomas were Epstein-Barr virus (EBV) negative. Flow cytometry showed λ light chain restriction in the initial BL and κ light chain restriction in the subsequent BL. B-cell clonality testing indicated that the two lymphomas are not clonally related. SNP array analysis of the second BL showed genomic changes that were not present in the first BL.

CONCLUSIONS

These results confirm that these two tumors represent unrelated BLs. Pathologists and clinicians should be aware that second lymphomas in XLP1 patients may represent new neoplasms rather than late relapses.

XLP: clinical features and molecular etiology due to mutations in SH2D1A encoding SAP

X-linked lymphoproliferative disease (XLP) is a rare primary immunodeficiency affecting approximately 1-2 per 1 million males. A key feature of XLP is the exquisite sensitivity of affected individuals to disease induced following EBV infection. However, patients can also develop hypogammaglobulinemia and B-cell lymphoma independently of exposure to EBV. XLP is caused by loss-of function mutations in SH2D1A, which encodes the intracellular adaptor molecule SAP. SAP is predominantly expressed in T cells and NK cells, and functions to regulate signal transduction pathways downstream of the SLAM family of surface receptors to control CD4+ T cell (and by extension B cells), CD8+ T cell and NK cell function, as well as the development of NKT cells. The study of XLP had shed substantial light on the requirements for lymphocyte differentiation and immune regulation, which in turn have the potential to be translated into novel treatments for not only XLP patients but individuals affected by EBV-induced disease, impaired humoral immunity and malignancy.

Occurrence of nodular lymphocyte-predominant hodgkin lymphoma in hermansky-pudlak type 2 syndrome is associated to natural killer and natural killer T cell defects

Hermansky Pudlak type 2 syndrome (HPS2) is a rare autosomal recessive primary immune deficiency caused by mutations on β3A gene (AP3B1 gene). The defect results in the impairment of the adaptor protein 3 (AP-3) complex, responsible for protein sorting to secretory lysosomes leading to oculo-cutaneous albinism, bleeding disorders and immunodeficiency. We have studied peripheral blood and lymph node biopsies from two siblings affected by HPS2. Lymph node histology showed a nodular lymphocyte predominance type Hodgkin lymphoma (NLPHL) in both HPS2 siblings. By immunohistochemistry, CD8 T-cells from HPS2 NLPHL contained an increased amount of perforin (Prf) + suggesting a defect in the release of this granules-associated protein. By analyzing peripheral blood immune cells we found a significant reduction of circulating NKT cells and of CD56(bright)CD16(-) Natural Killer (NK) cells subset. Functionally, NK cells were defective in their cytotoxic activity against tumor cell lines including Hodgkin Lymphoma as well as in IFN-γ production. This defect was associated with increased baseline level of CD107a and CD63 at the surface level of unstimulated and IL-2-activated NK cells. In summary, these results suggest that a combined and profound defect of innate and adaptive effector cells might explain the susceptibility to infections and lymphoma in these HPS2 patients.

Inflammatory polyps following successful HLA-matched cord blood transplantation in a patient with X-linked lymphoproliferative syndrome

Gastrointestinal complications following HSCT are numerous and include a variety of issues resulting in hepatic, biliary, pancreatic, and intestinal compromise. In the context of an underlying state of immune dysregulation, novel complications may arise including autoimmunity. To our knowledge, this is the first report of a patient with XLP who was successfully treated with HSCT using an HLA-matched unrelated cord blood unit that was complicated by the development of inflammatory polyps of the colon. Given the underlying diagnosis of XLP and its associated immune dysregulation, the challenge of understanding unique gastrointestinal manifestations of autoimmunity following HSCT is discussed.

SLAM family receptors and SAP adaptors in immunity

The signaling lymphocyte activation molecule (SLAM)-associated protein, SAP, was first identified as the protein affected in most cases of X-linked lymphoproliferative (XLP) syndrome, a rare genetic disorder characterized by abnormal responses to Epstein-Barr virus infection, lymphoproliferative syndromes, and dysgammaglobulinemia. SAP consists almost entirely of a single SH2 protein domain that interacts with the cytoplasmic tail of SLAM and related receptors, including 2B4, Ly108, CD84, Ly9, and potentially CRACC. SLAM family members are now recognized as important immunomodulatory receptors with roles in cytotoxicity, humoral immunity, autoimmunity, cell survival, lymphocyte development, and cell adhesion. In this review, we cover recent findings on the roles of SLAM family receptors and the SAP family of adaptors, with a focus on their regulation of the pathways involved in the pathogenesis of XLP and other immune disorders.

Impaired Epstein-Barr virus–specific CD8+ T-cell function in X-linked lymphoproliferative disease is restricted to SLAM family–positive B-cell targets

X-linked lymphoproliferative disease (XLP) is a condition associated with mutations in the signaling lymphocytic activation molecule (SLAM)–associated protein (SAP; SH2D1A). SAP functions as an adaptor, binding to and recruiting signaling molecules to SLAM family receptors expressed on T and natural killer cells. XLP is associated with extreme sensitivity to primary Epstein-Barr virus (EBV) infection, often leading to a lethal infectious mononucleosis. To investigate EBV-specific immunity in XLP patients, we studied 5 individuals who had survived EBV infection and found CD8+ T-cell responses numerically comparable with healthy donors. However, further investigation of in vitro–derived CD8+ T-cell clones established from 2 of these donors showed they efficiently recognized SLAM ligand–negative target cells expressing EBV antigens, but showed impaired recognition of EBV-transformed, SLAM ligand–positive, lymphoblastoid cell lines (LCLs). Importantly, LCL recognition was restored when interactions between the SLAM receptors CD244 and natural killer–, T-, and B-cell antigen (NTBA) and their ligands on LCLs were blocked. We propose that XLP patients' particular sensitivity to EBV, and not to other viruses, reflects at least in part EBV's strict tropism for B lymphocytes and the often inability of the CD8+ T-cell response to contain the primary infection of SLAM ligand–expressing target cells.

Epstein-Barr virus persistence in the absence of conventional memory B cells: IgM+IgD+CD27+ B cells harbor the virus in X-linked lymphoproliferative disease patients

Epstein-Barr virus (EBV) persists in healthy virus carriers within the immunoglobulin (Ig)D−CD27+ (class-switched) memory B-cell compartment that normally arises through antigen stimulation and germinal center transit. Patients with X-linked lymphoproliferative disease (XLP) lack such class-switched memory B cells but are highly susceptible to EBV infection, often developing fatal symptoms resembling those seen in EBV-associated hemophagocytic syndrome (EBV-AHS), a disease caused by aberrant virus entry into the NK- or T-cell system. Here we show that XLP patients who survive primary EBV exposure carry relatively high virus loads in the B-cell, but not the NK- or T-cell, compartment. Interestingly, in the absence of conventional class-switched memory B cells, the circulating EBV load was concentrated within a small population of IgM+IgD+CD27+ (nonswitched) memory cells rather than within the numerically dominant naive (IgM+IgD+CD27−) or transitional (CD10+CD27−) subsets. In 2 prospectively studied patients, the circulating EBV load was stable and markers of virus polymorphism detected the same resident strain over time. These results provide the first definitive evidence that EBV can establish persistence in the B-cell system in the absence of fully functional germinal center activity and of a class-switched memory B-cell compartment.

Regulation of cellular and humoral immune responses by the SLAM and SAP families of molecules

SAP (SLAM-associated protein) was identified in 1998 as an adaptor molecule involved in the intracellular signaling pathways elicited through the cell surface receptor SLAM and as the protein defective in the human immunodeficiency X-linked lymphoproliferative disease (XLP). During the past eight years, it has been established that the SLAM family of cell surface receptors (SLAM, 2B4, NTB-A, Ly9, CD84) and the SAP family of adaptors (SAP, EAT-2, ERT) play critical roles in lymphocyte development, differentiation, and acquisition of effector functions. Studies of these proteins have shown unexpected roles in cytokine production by T cells and myeloid cells, T cell-dependent humoral immune responses, NK cell-mediated cytotoxicity, and NKT cell development. This review highlights recent findings that have improved our understanding of the roles of the SLAM and SAP families of molecules in immune regulation and discusses how perturbations in the signaling pathways involving these proteins can result in different disease states.

Increased proliferation of CD8+ T cells in SAP-deficient mice is associated with impaired activation-induced cell death

Defective signaling lymphocyte activation molecule (SLAM)-associated protein (SAP) is responsible for the human X-linked lymphoproliferative syndrome. Defects in T helper 2, natural killer, natural killer T and B cells have been demonstrated in SAP-deficient humans and mice, and increased proliferation of CD8+ T cells has been observed. In the current study, we investigated the properties of CD8+ T cell proliferation and activation-induced cell death (AICD), using OT-I T cell receptor (TCR)-transgenic mice on either wild-type (WT) or SAP-/- background. Interestingly, we found that ovalbumin peptide-activated SAP-/- CD8+ T cells have lower AICD compared to their WT counterparts. Furthermore, the induction of p73, a key mediator of TCR-induced apoptosis through the mitochondrial apoptotic pathway, was significantly reduced at both the mRNA and protein levels in the activated mutant cells. Meanwhile, a reduced level of activated caspase 9 was observed in the mutant cells. We conclude that reduced AICD in activated SAP-/- CD8+ T cells is associated with impaired p73 induction, indicating that the initiation of the mitochondrial apoptotic pathway might be impaired. Our data demonstrate an intrinsic defect in SAP-/- CD8+ T cells and shed light on the increased responsiveness of CD8+ T cells in SAP-/- mice.

Hypogammaglobulinemia and exacerbated CD8 T-cell–mediated immunopathology in SAP-deficient mice with chronic LCMV infection mimics human XLP disease

The human genetic disease X-linked lymphoproliferative disease (XLP), which is caused by mutations in SH2D1A/SAP that encode SLAM-associated protein (SAP), is characterized by an inability to control Epstein-Barr virus (EBV) and hypogammaglobulinemia. It is unclear which aspects of XLP disease are specific to herpesvirus infection and which reflect general immunologic functions performed by SAP. We examined SAP– mice during a chronic LCMV infection, specifically to address the following question: Which SAP deficiency immunologic problems are general, and which are EBV specific? Illness, weight loss, and prolonged viral replication were much more severe in SAP– mice. Aggressive immunopathology was observed. This inability to control chronic LCMV was associated with both CD8 T-cell and B-cell response defects. Importantly, we demonstrate that SAP– CD8 T cells are the primary cause of the immunopathology and clinical illness, because depletion of CD8 T cells blocked disease. This is the first direct demonstration of SAP– CD8 T-cell–mediated immunopathology, confirming 30 years of XLP clinical observations and indirect experimentation. In addition, germinal center formation was extremely defective in chronically infected SAP– animals, and hypogammaglobulinemia was observed. These findings in a chronic viral infection mouse model recapitulate key features of human XLP and clarify SAP's critical role regulating both cellular and humoral immunity.

Allogeneic stem cell transplantation in X-linked lymphoproliferative disease: two cases in one family and review of the literature

X-linked lymphoproliferative disease (XLP) is a rare immunodeficiency caused by mutations in the signaling lymphocyte activating molecule-associated protein/SH2D1A gene and characterized by a dysregulated immune response to Epstein-Barr virus and other pathogens. The clinical presentation is heterogeneous and includes fulminant infectious mononucleosis, lymphoma, hypogammaglobulinemia and aplastic anemia. XLP is associated with a high morbidity and overall outcome is poor. At present, allogeneic stem cell transplantation (alloSCT) is the only curative treatment. XLP patients may be recognized in various stages of disease and even when symptoms are not yet evident. We here present two related XLP patients in different stages of disease that were both treated successfully with alloSCT using a matched unrelated donor. In addition, we have reviewed all reported cases of alloSCTs in XLP patients. Based on these results and in order to improve the final outcome, we conclude that alloSCT should be recommended in both symptomatic and asymptomatic XLP patients.

Molecular and cellular pathogenesis of X-linked lymphoproliferative disease

X-linked lymphoproliferative disease (XLP) is an inherited immune defect caused by mutations in the Src homology 2 domain-containing gene 1A, which encodes the adapter protein, signaling lymphocytic activation molecule (SLAM)-associated protein (SAP). SAP is expressed in T cells, natural killer (NK) cells, and NKT cells, where it binds to the cytoplasmic domain of the surface receptor SLAM (CD150) and the related receptors, 2B4 (CD244), CD84, Ly9 (CD229), NK-T-B-antigen, and CD2-like receptor-activating cytotoxic T cells. SAP also binds to the Src family tyrosine kinase Fyn and recruits it to SLAM, which leads to the generation of downstream phosphotyrosine signals. While the roles of the SLAM family receptors are only beginning to be understood, experiments suggest that these molecules regulate important aspects of lymphocyte function, such as proliferation, cytokine secretion, cytotoxicity, and antibody production. Thus, in XLP patients who lack functional SAP, the SLAM family receptors may not signal properly. This property likely contributes to the phenotypes of XLP, including fulminant infectious mononucleosis, lymphoma, and hypogammaglobulinemia. Further studies of SAP and the SLAM family receptors will provide insights into XLP and elucidate the signaling events regulating lymphocyte ontogeny and function.

Mice deficient in the X-linked lymphoproliferative disease gene sap exhibit increased susceptibility to murine gammaherpesvirus-68 and hypo-gammaglobulinemia

X-linked lymphoproliferative disease is characterized by immune dysregulation and uncontrolled lymphoproliferation on exposure to Epstein-Barr virus (EBV). This disease has been attributed to mutations in the SAP gene (also denominated as SH2D1A or DSHP). To delineate the role of SAP in the pathophysiology of X-linked lymphoproliferative disease, a strain of sap-deficient mice has been generated by deleting exon 2 of the gene. After infection with murine gammaherpesvirus-68, which is homologous to EBV, the mutant mice exhibit more vigorous CD8+ T cell proliferation and more disseminated lymphocyte infiltration compared to their wild-type littermates. Chronic tissue damage and hemophagocytosis were evident in sap-deficient mice but not in their wild-type littermates. Concordantly, murine gammaherpesvirus-68 reactivation was observed in sap-deficient mice, indicating an impaired control of the virus. Notably, IgE deficiency and decreased serum IgG level were observed in mutant mice prior to and after murine gammaherpesvirus-68 infection, which reproduces hypo-gammaglobulinemia in X-linked lymphoproliferative disease patients. This mouse model will therefore be a useful tool for dissecting the various phenotypes of X-linked lymphoproliferative disease.

The epidemiology of neonatal tumours. Report of an international working group

Neonatal tumours occur every 12,500-27,500 live births and comprise 2% of childhood malignancies, but there is little clarity as to their real prevalence, sites of origin and pathological nature as reported series vary. As an entity, neonatal tumours provide a unique window of opportunity to study tumours in which minimal environmental interference has occurred. The majority of tumours present with a mass at birth (e.g., teratomas, neuroblastomas, mesoblastic nephroma, fibromatosis), which are not infrequently identified on antenatal ultrasound. Histologically, teratoma and neuroblastoma remain the two main tumour types encountered with soft tissue sarcoma, renal tumours, CNS tumours and leukaemia being the next most common tumour types identified. Malignant tumours are uncommon in the neonatal period per se and benign tumours may have malignant potential. A particular problem exists in clinical classification, as histological features of malignancy do not always correlate with clinical behaviour. Benign tumours may also be life threatening because of their size and location. Other tumours may demonstrate local invasiveness, but no metastatic potential, and tumours that are clearly malignant may demonstrate unpredictable or uncertain behaviour. Screening programmes have brought more tumours to light, but do not appear to affect the overall prognosis. They may provide clues to the stage at which tumours develop in foetu. The aetiology of cancer in children is multifactorial and includes both genetic and environmental factors. The association between congenital abnormalities and tumours is well established (15% of neonatal tumours). Genetic defects are highly likely in neonatal tumours and include those with a high risk of malignancy (e.g., retinoblastoma), but also genetically determined syndromes with an increased risk of malignancy and complex genetic rearrangements. Tumours are mostly genetically related at a cellular level and factors influencing cellular maturation or apoptosis within the developing foetus may continue to operate in the neonatal period. Cytogenetics of neonatal neoplasms appear to differ from neoplasms in older children, thus possibly explaining some of the observed differences in clinical behaviour. Certain constitutional chromosome anomalies, however, specifically favour tumours occurring in the foetal and neonatal period. In support of this hypothesis, certain cytogenetic anomalies appear to be specific to neonates, and a number of examples are explored. Other environmental associations include ionizing radiation, drugs taken during pregnancy, infections, tumours in the mother and environmental exposure.

Absence of SLAM mutations in EBV-associated lymphoproliferative disease patients

X-linked lymphoproliferative disease is a rare inherited immunodeficiency in which affected males present abnormal responses to Epstein-Barr virus (EBV) infection. The gene defective in X-linked lymphoproliferative disease, SH2D1A (also named SAP or DSHP), has been identified and shown to code for an adapter protein that interacts with signaling lymphocytic activation molecule (SLAM) and several other members of the CD2 superfamily. SH2D1A is mutated in no more than 60% of X-linked lymphoproliferative disease patients. It could be postulated that a certain percentage of patients without apparent maternal transmission might be caused by other gene(s) in SH2D1A-related signal transduction pathways. Being a partner of SH2D1A and having a key role in proliferation and differentiation of the T- and B-lymphocytes, SLAM was considered as a candidate gene for patients who manifest symptoms of X-linked lymphoproliferative disease but who have no mutations in SH2D1A. As a first step, SLAM mutations were screened for from cDNA of the lymphoblastoid cell line of all available patients. Then conditions for PCR, single-strand conformational polymorphism (SSCP), heteroduplex analysis, and sequencing were established in all eight exons of SLAM. A total of 31 typical and atypical patients were analysed, from which six novel nucleotide variants were identified; however, none of these variants seems to cause abnormal function of the SLAM gene. Therefore, mutations in coding regions or splicing sites of SLAM are unlikely to play a major role in the mechanism of EBV-associated lymphoproliferation.

Bone marrow stem cells and stromal cells in autoimmune cytopenias

High-dose immunosuppression followed by autologous haemopoietic stem cell transplantation (ASCT) is a promising practice for the treatment of severe, resistant autoimmune disorders. Patients with refractory autoimmune cytopenias (AIC), primary or secondary to systemic autoimmune diseases (AID) including systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), have been proposed as potential candidates for such a therapeutic procedure. An abnormal immune milieu, however, may affect the number and functional characteristics of stem cells and/or stromal cells in the bone marrow (BM) and might impact on harvesting and engraftment potential of stem cells or on BM reconstitution following engraftment in patients with AIC undergoing ASCT. Using flow cytometry and in vitro culture assays we have shown that patients with primary AIC display increased number of BM CD34+ cells in response to abnormally high production of granulocyte-colony stimulating factor (G-CSF) by BM stroma. In contrast, patients with AIC secondary to systemic AID display increased apoptosis of BM progenitor cells resulting in low CD34+ cell numbers and abnormal haemopoiesis supporting capacity of BM stroma due to the aberrant, local or systemic, inhibitory cytokine production or to intricate interactions between haemopoietic and immune cells present within the BM microenvironment. In this review we summarize the available knowledge on BM stem cell reserve and function and stromal cell function in patients with primary and secondary AIC with special reference to SLE and RA. The underlying mechanisms possibly involved in the pathogenesis of the observed abnormalities are also discussed.

Large T-cell lymphoma in a 13-year-old girl with hyperimmunoglobulinemia E syndrome

Large T-cell lymphoma was diagnosed in a 13-year-old girl with hyperimmunoglobulinemia E syndrome (HIES). Her past medical history included severe dermatitis, recurrent pneumonia, urinary tract infections, mucocutaneous herpetic infections, fungal skin infections, and staphylococcal sepsis. The diagnosis of HIES, based on the clinical features and a serum IgE level of >20000 IU/ml, was established when the girl was 6 years old. This is the eighth case of lymphoma in a patient with HIES reported in the English-language medical literature. HIES has not usually been considered a predisposing factor for malignancy, but in view of the rarity of HIES and the young age of the patients, this association seems to be more than coincidental. A link between lymphoma and Epstein-Barr virus (EBV) infection in patients with HIES has been proposed. Serological tests for EBV in our patient were positive 6 years prior to the development of the lymphoma; however, examination for EBV DNA in the lymph node biopsy failed to detect EBV in the tumor.

Induction of the Epstein-Barr virus thymidine kinase gene with concomitant nucleoside antivirals as a therapeutic strategy for Epstein-Barr virus-associated malignancies

Lymphoproliferative diseases (LPDs) associated with the Epstein-Barr virus (EBV) include non-Hodgkin lymphomas, which occur in the setting of immunosuppression, including that induced by human immunodeficiency virus, and posttransplant lymphoproliferative disorders. These LPDs are characterized by actively proliferating, latently infected EBV-positive B lymphocytes and often follow a rapidly progressive fatal clinical course. Pharmacologic treatment for herpesvirus infections has targeted the virus-specific enzyme, thymidine kinase (TK), with nucleoside analogs. The lack of viral TK expression in EBV-positive tumors, caused by viral latency, however, makes antiviral therapy alone ineffective as an antineoplastic therapy. Arginine butyrate selectively activates the EBV TK gene in latently infected EBV-positive tumor cells. We have developed a strategy for treatment of EBV-associated lymphomas using pharmacologic induction of the latent viral TK gene and enzyme in tumor cells using arginine butyrate, followed by treatment with ganciclovir. A phase I/II trial, using an intrapatient dose escalation of arginine butyrate combined with ganciclovir, is underway. This combination therapy has produced complete clinical responses in 5 of 10 previously refractory patients, with partial responses occurring in 2 additional patients. This virus-targeted antitumor strategy may provide a new therapeutic approach to EBV-associated neoplasms.

Successful treatment of severe aplastic anemia associated with human parvovirus B19 and Epstein-Barr virus in a healthy subject with allo-BMT

Several reports have noted pancytopenia associated with Human parvovirus B19 (PVB19) or Ebstein-Barr virus (EBV) infections in patients who have no history of immunodeficiency. To our knowledge, we report the first case of severe aplastic anemia associated with both EBV and PVB19 infections in a previously healthy 22-year-old man. He was admitted to our hematology service due to anemia and thrombocytopenia. He had no symptoms or signs of infections of these viruses. His bone marrow biopsy revealed a hypocellular marrow. Specific IgM and IgG antibodies to EBV and PVB19 were elevated. EBV and PVB19 virus genomes were detected by PCR in the bone marrow nucleated cells and the peripheral blood lymphocytes. Two months after treatment with prednisone, acyclovir, and intravenous immune globulin (IVIg), the genomes of both these viruses disappeared. However, his transfusion requirement for platelet suspensions and packed red blood cells persisted. The patient underwent allogeneic bone marrow transplant (allo-BMT) and has had an enduring complete hematological response for 8 months.

Central nervous system involvement of Epstein-Barr virus lymphoproliferative disease in a patient with acute lymphocytic leukemia

Epstein-Barr virus-related lymphoproliferative disease (EBV-LPD) is a serious and often fatal complication of a variety of immune-suppressed conditions. A 6-year-old boy undergoing chemotherapy for standard-risk acute lymphocytic leukemia experienced separate episodes of EBV-LPD in different organ systems. The patient experienced three separate episodes of EBV-LPD in the cervical lymph node, the central nervous system (CNS), and the liver occurring, respectively, in January 1992, February 1992, and November 1993 after the completion of chemotherapy in May 1993. The EBV presence was confirmed by in situ hybridization in the biopsy samples from each lesion. Several different treatment modalities, including acyclovir, intravenous gamma globulin, and surgery were used to combat the EBV-LPD. The patient has recovered completely, with normal CNS and liver function, and for the past 6 years has experienced leukemia remission while not receiving chemotherapy. Careful monitoring of patients and the use of new immune therapies offer the highest chance for successful outcomes in such patients.

Recurrent B-cell non-Hodgkin's lymphoma in two brothers with X-linked lymphoproliferative disease without evidence for Epstein-Barr virus infection

We present two male siblings suffering from recurrent manifestations of B-cell non-Hodgkin's lymphoma (NHL) and recurrent infections of the lower respiratory tract associated with bronchiectasis. Immunodeficiency could not be demonstrated by any laboratory investigation. In both patients, lymphomas developed without evidence for Epstein-Barr virus (EBV) infection, i.e. no antibody response to EBV-specific antigens, negative EBV-PCR (polymerase chain reaction) in peripheral blood cells, and absence of latent membrane protein (LMP) and EBV-encoded RNA (EBER) in lymphoma cells. Molecular analysis of the SH2D1A, the gene for X-linked lymphoproliferative disease (XLP) led to the identification of a deletion in the first exon in both patients. Therefore, we postulate that the genetic defect and the following dysregulation of the B-/T-cell interaction rendered these patients susceptible to the early onset of B-cell NHL and that EBV infection is not an obligate prerequisite.

X linked lymphoproliferative disease in a United Kingdom family

X linked lymphoproliferative disease (XLP; Duncan's disease) is a rare disorder affecting boys and characterised by a defective immune response to Epstein-Barr virus caused by a mutation in a gene located at chromosome Xq25. Three siblings with XLP in a single UK family are reported and the variation in phenotypic expression of the disease in these siblings described. One of the siblings with life threatening fulminant infectious mononucleosis was successfully treated by chemotherapy, followed by bone marrow transplantation using an unaffected brother as the donor. A healthy baby boy recently born into the family was identified as carrying the defective maternal X chromosome using molecular genetic linkage analysis. This family illustrates the extent of present understanding of this often fatal condition.

Arginine butyrate-induced susceptibility to ganciclovir in an Epstein-Barr-virus-associated lymphoma

Lymphoproliferative disorders associated with Epstein-Barr virus (EBV) infections can occur in the setting of immunosuppression. In some patients, the lymphoproliferative disorder can resemble an aggressive monoclonal non-Hodgkins lymphoma (NHL). These NHL are poorly responsive to conventional therapy. Similarly, antiviral therapy with synthetic nucleosides such as ganciclovir are ineffective because the genes that render the virus susceptible to therapy are not expressed in EBV+ lymphomas. Using a cell line derived from a lung transplant recipient with an EBV+ immunoblastic NHL, we studied the ability of arginine butyrate to induce the expression of EBV thymidine kinase. Arginine butyrate was not only effective in inducing EBV thymidine kinase transcription, but also acted synergistically with the antiviral agent ganciclovir to inhibit cell proliferation and decrease cell viability. Based on these findings, the patient from whom the cell line was derived was treated with arginine butyrate/ganciclovir as well as conventional cytotoxic chemotherapy. No additional toxicity was observed with the arginine butyrate/ganciclovir therapy. Histologic examination of the tumor showed substantial necrosis. These observations suggest the feasibility of arginine butyrate induction of ganciclovir susceptibility in patients with EBV-associated lymphomas.

Distinct regions of EBV DNase are required for nuclease and DNA binding activities

Epstein-Barr virus (EBV) DNase possesses both endonuclease and exonuclease activities and accepts both double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) as substrates. To map regions of EBV DNase responsible for nuclease and DNA binding activities, a series of mutant DNase polypeptides was expressed using a bacterial system for the nuclease assay and in an in vitro transcription/translation system to assay binding activity to dsDNA or ssDNA cellulose. The results indicated that the C-terminus of EBV DNase, residues 450-460, is essential for nuclease activity but dispensable for DNA binding. However, deletion of residues 441-470 resulted in the loss of both nuclease and DNA binding activities. Substitution of Phe452 and Val458 led to inactive enzymes. In the N-terminus, deletion of residues 23-28 and residues 7-61 resulted in the loss of nuclease activity but the DNA binding activities of the deleted enzymes were intermediate and low, respectively. Mutation of Leu23 to Gly showed drastically reduced nuclease activity but its DNA binding ability was not affected. Based on the amino acid sequence alignment of various herpesvirus DNases, we chose four highly conserved and two less well conserved regions as controls for mutagenesis studies. These six internal deletion (ID) mutants were prepared using a recombinant PCR method. Each of the polypeptides was expressed in a bacterial system for the nuclease assay and using an in vitro transcription/translation system for the DNA binding assay. DNA binding and nuclease activities of all six internal deletion mutants were abolished, except that mutant ID2, with deletion of residues 138-152, retained an intermediate ability to bind DNA. These data indicate that since mutations at distinct regions within EBV DNase resulted in the loss of nuclease and/or DNA binding activities, it is suggested that these distinct regions are required for maintenance of an intact and highly ordered structure(s) for both activities.

Practical aspects in the diagnosis and management of aplastic anemia

Aplastic anemia may result from several pathogenic mechanisms, the most common is idiopathic. The current definitive treatments for aplastic anemia are bone marrow transplantation (BMT) or immunosuppressive (IS) therapy. The benefits of each are comparable. However, certain subsets of patients derive superior benefit from one or the other. Bone marrow transplantation is the initial treatment of choice for young patients (< 20 years old). It results in the complete reconstitution of hematopoiesis, whereas autologous hematopoietic remissions after IS therapy are more susceptible to relapse. Survival rates after BMT, in patients between the ages of 20 and 40, are comparable to those reported for IS therapy. Better survival rates after BMT have been achieved with improved conditioning regimens and graft-versus-host disease prophylaxis. For patients older than 40, the treatment of choice is IS. Long-term complications of IS therapy include recurrence and development of clonal myeloid disorders. Long-term complications after BMT include graft-versus-host disease and secondary neoplasms. The IS regimen includes the combination of antithymocyte globulin and cyclosporin A. The addition of growth factor to the IS regimen seems promising; however, their use on their own is not recommended. Androgens have been shown to be inferior in the treatment of aplastic anemia. The role of BMT from an unrelated donor is being investigated.

Epstein-Barr virus in B-cell non-Hodgkin's lymphomas: unexpected infection patterns and different infection incidence in low- and high-grade types

Two hundred and eight cases of B-cell non-Hodgkin's lymphoma (B-NHL) occurring in Europeans without any signs of HIV infection were investigated for their association with an Epstein-Barr virus (EBV) infection. The polymerase chain reaction (PCR) was applied for EBV-DNA detection, in situ hybridization (ISH) for the cellular localization of EBV-encoded small nuclear RNAs (EBER) and immediate-early RNAs (BHLF), and immunohistology (IH) for the detection of EBV-encoded latent membrane protein (LMP) and EBV nuclear antigen 2 (EBNA2) expression. PCR and EBER-ISH produced congruent results in those cases with amplifiable DNA. EBV was present overall in 26 per cent (54/208) of the B-NHL cases. Through EBER-ISH, the virus could be localized merely in rare non-neoplastic bystander lymphocytes in 27 and additionally in tumour cells of 27 cases. Unexpectedly, the proportion of EBV-infected tumour cells present in the different cases varied between 1 and 100 per cent. All but three of the cases with infected tumour cells were of high-grade malignancy. Correlation with the morphological and immunological tumour phenotype revealed that all cases with more than 80 per cent EBER-positive tumour cells were either B-anaplastic large cell lymphomas (B-ALCL), sporadic Burkitt's lymphomas, or B-NHLs with partial or full plasmacellular differentiation. LMP was consistently absent from Burkitt's lymphomas and constantly expressed in B-ALCLs with EBER-positive tumour cells, while in all other instances it varied greatly and was rarer than EBER expression.(ABSTRACT TRUNCATED AT 250 WORDS)

Epstein-Barr virus as an agent of haematological disease

Epstein-Barr virus (EBV) encodes genes that permit its persistence in human B lymphocytes and genes that ensure its replication in epithelial cells. Immune restraints on the virus are usually so effective that most EBV infections are limited to a minute fraction of B lymphocytes and of epithelial cells. As a result, most EBV infections are never symptomatic. Occasionally, the virus causes disease, often with the cooperation of the immune system or other less characterized cofactors. Infectious mononucleosis, a generally self-limited lymphoproliferative illness common in adolescents and young adults, is due to primary EBV infection and to the brisk cellular immune response it elicits. Lymphoproliferative disorders of EBV-infected B cells arise almost exclusively when cellular immunity is grossly compromised. EBV-positive Burkitt's lymphoma contain a translocated and deregulated c-myc oncogene and EBV-positive non-Hodgkin's lymphomas are characterized by the presence of Reed-Sternberg's and Hodgkin's cells, features that have not been directly linked to EBV. Many recent observations, however, including evidence that virus infection precedes malignant transformation and is often associated with a characteristic pattern of viral gene expression, provide continued interest in the relationship between the virus and these haematological malignancies.

Epstein-Barr virus in non-Hodgkin's lymphomas and lymphoid tissue in children

In developed countries the majority of adolescent children show serological evidence of past Epstein-Barr virus (EBV) infection. This virus is associated with non-Hodgkin's lymphomas in immunocompromised children, but the relationship of EBV DNA to these tumors in children without documented immunodeficiency has not been investigated by the polymerase chain reaction (PCR). We used a PCR method with primers from the Bam W and Bam HI regions to study non-Hodgkin's lymphomas in children, with tonsillar tissue of age-matched children as controls for the presence of EBV DNA. Six of the 20 tonsils were positive using the Bam W primers; another four showed this DNA with Bam HI primers. EBV DNA was detected in only one tumor (a lymphoblastic lymphoma) by both primer sets. The demonstration of EBV DNA in the tonsils reflects past infections and the incidence is in accordance with that expected from serologic epidemiological studies. The absence of demonstrable EBV DNA in 19 lymphomas suggests that this virus is of little consequence in the pathogenesis of non-Hodgkin's lymphomas in children who are not known to be immunocompromised. The lymphoblastic lymphoma had a mixed cell population, and the virus was not necessarily related to the malignancy.

Detection of Epstein-Barr virus small RNAs in routine paraffin sections using non-isotopic RNA/RNA in situ hybridization

The Epstein-Barr virus (EBV) is associated with an increasing range of reactive and neoplastic lesions. There is a need for a sensitive and specific method for detecting latent EBV in routine histological sections. We report the use of a highly sensitive paraffin section RNA/RNA in situ hybridization (ISH) technique using digoxigenin-labelled antisense riboprobes for demonstrating EBV encoded small RNAs (EBERs), EBV gene products that are transcribed in abundance during latent EBV infection. We applied EBER-ISH to 846 paraffin embedded specimens, including cases of reactive lymphoid hyperplasia (n = 28), infectious mononucleosis (16), Burkitt's lymphoma (44), immunodeficiency-associated lymphomas in transplant recipients (9) and AIDS patients (128), Hodgkin's disease (130), CD30 antigen positive lymphomas (106), peripheral T-cell lymphomas (104), sporadic B-cell non-Hodgkin's lymphomas (162), undifferentiated nasopharyngeal carcinoma (86), salivary gland lymphoepithelioma (11), and oral hairy leukoplakia (5). Strong, reproducible EBER staining was seen in EBV latently infected cells in archival surgical biopsy and autopsy specimens. EBER-ISH is specific, has a sensitivity comparable to that of the polymerase chain reaction, and is now the method of choice for the in situ detection of latent EBV infection.

Sex difference in the serostatus of adults to the Epstein-Barr virus

A total of 1047 adults, aged between 18 and 90 years, including blood donors and surgical patients of the Medical University of Lübeck in Germany, were screened for IgG antibodies to the Epstein-Barr Virus, either by standard indirect immunofluorescence or by a novel enzyme-linked immunosorbent assay (Enzygnost Anti-EBV/IgG, Behring, Marburg, Germany). There was a significant sex difference in the serostatus to the Epstein-Barr virus in adults. Male adults were more likely than females (p < 1%) to be EBV-seronegative. The same trend was seen in both a group of 713 blood donors and 334 surgical patients and when different test methods were used. However, this sex difference was not shown in the sera of 86 pediatric patients of the Medical University of Lübeck tested by indirect immunofluorescence for IgG antibodies to the Epstein-Barr virus. Furthermore, titers of IgG antibodies to Epstein-Barr virus specific antigens of female adults, obtained by the enzyme-linked immunosorbent assay (Enzygnost Anti-EBV/IgG), had significantly higher median values than male adults (p < 5%).

Retinal necrosis in X-linked lymphoproliferative disease

BACKGROUND

X-linked lymphoproliferative disease is a hereditary disease that renders the males susceptible to fatal infectious mononucleosis, aplastic anemia, malignant lymphoma, and hypogammaglobulinemia after infection by the Epstein-Barr virus.

METHODS

The authors examined the clinical and pathologic findings in an 8-year-old boy with bilateral retinal necrosis who died with aplastic anemia as a complication of X-linked lymphoproliferative disease.

RESULTS

Results of histopathologic examination of the eyes disclosed retinal necrosis, and examination using the polymerase chain reaction technique showed Epstein-Barr virus genomic DNA in the left eye.

CONCLUSION

Retinal necrosis may be part of the expanding spectrum of X-linked lymphoproliferative disease. It is unknown if the retinal necrosis is due directly to Epstein-Barr virus infection or a host inflammatory response.

Activation of the Epstein-Barr virus replicative cycle by human herpesvirus 6

One common attribute of herpesviruses is the ability to establish latent, life-long infections. The role of virus-virus interaction in viral reactivation between or among herpesviruses has not been studied. Preliminary experiments in our laboratory had indicated that infection of Epstein-Barr virus (EBV) genome-positive human lymphoid cell lines with human herpesvirus 6 (HHV-6) results in EBV reactivation in these cells. To further our knowledge of this complex phenomenon, we investigated the effect of HHV-6 infection on expression of the viral lytic cycle proteins of EBV. Our results indicate that HHV-6 upregulates, by up to 10-fold, expression of the immediate-early Zebra antigen and the diffuse and restricted (85 kDa) early antigens (EA-D and EA-R, respectively) in both EBV producer and nonproducer cell lines (i.e., P3HR1, Akata, and Raji). Maximal EA-D induction was observed at 72 h post-HHV-6 infection. Furthermore, expression of late EBV gene products, namely, the viral capsid antigen (125 kDa) and viral membrane glycoprotein gp350, was also increased in EBV producer cells (P3HR1 and Akata) following infection by HHV-6. By using dual-color membrane immunofluorescence, it was found that most of the cells expressing viral membrane glycoprotein gp350 were also positive for HHV-6 antigens, suggesting a direct effect of HHV-6 replication on induction of the EBV replicative cycle. No expression of late EBV antigens was observed in Raji cells following infection by HHV-6, implying a lack of functional complementation between the deleted form of EBV found in Raji cells and the superinfecting HHV-6. The susceptibility of the cell lines to infection by HHV-6 correlated with increased expression of various EBV proteins in that B95-8 cells, which are not susceptible to HHV-6 infection, did not show an increase in expression of EBV antigens following treatment with HHV-6. Moreover, UV light-irradiated or heat-inactivated HHV-6 had no upregulating effect on the Zebra antigen or EA-D in Raji cells, indicating that infectious virus is required for the observed effects of HHV-6 on these EBV products. These results show that HHV-6, another lymphotropic human herpesvirus, can activate EBV replication and may thus contribute to the pathogenesis of EBV-associated diseases.

Defective activity of Epstein-Barr virus (EBV) specific cytotoxic T lymphocytes in children with chronic active EBV infection and in their parents

Antibodies of Epstein-Barr virus (EBV), EBV-specific cytotoxic T lymphocyte (EBVCTL) activity and the lymphocyte subset of CTL were examined in 13 Japanese children with chronic active EBV infection (CAEBV) and their parents (eight fathers and 10 mothers). Anti-virus-capsid antigen (VCA)-IgG antibody titers ranged from 1:640 to 1:5120 in the patients with CAEBV and from 1:40 to 1:640 in the parents. While anti-VCA-IgM antibody was detected in three patients, anti-VCA-IgA antibody in five and anti-early-antigen (EA)-IgG antibody in 11, no antibody was detected in the parents except anti-EA antibody, which was positive in the mothers of cases 5 and 13 (1:10 and 1:40). Anti-EBV-associated nuclear antigen (EBNA) antibody was < or = 1:10 in six out of 13 patients with CAEBV and in 10 out of 18 parents tested. Epstein-Barr virus activity was significantly lower (P < 0.005) both in the children with CAEBV and in their parents than in seropositive age-matched controls. Proportions of a CTL subset (CD8+ CD11- lymphocytes) in the patients with CAEBV were significantly higher (P < 0.005) than in controls, while those in the parents were at the same level as in controls. Defective EBVCTL activity and anti-EBNA-antibody responses were frequently observed both in children with CAEBV and in their parents, which may suggest that the abnormal immune response to EBV may be based on a familial disorder, though no familial involvement has been reported in Japanese children with CAEBV.