SH2D1A mutations in Japanese males with severe Epstein-Barr virus--associated illnesses

X-linked lymphoproliferative disease (XLP), a genetic disorder characterized by immunodeficiency to Epstein-Barr virus (EBV) infection, has been linked to mutations in the SH2D1A gene. To search for the occurrence of SH2D1A mutations in Japan, we performed genetic analysis of the SH2D1A gene in 40 males presenting with severe EBV-associated illnesses, including fulminant infectious mononucleosis, EBV-positive lymphoma, and severe chronic active EBV infection. SH2D1A mutations were detected in 10 of these 40 patients. Five of these 10 cases were sporadic. Patients with SH2D1A mutations displayed severe acute infectious mononucleosis with hyperimmunoglobulin M, hypogammaglobulinemia, and B-cell malignant lymphoma. By contrast, chronic active EBV infection was not associated with SH2D1A mutations. XLP survivors exhibited normal levels of circulating EBV-DNA during convalescence, suggesting that SH2D1A protein is not directly responsible for control of EBV replication. Thus, genetic analysis of the SH2D1A gene is particularly useful in the diagnosis of sporadic cases and carriers of XLP. (Blood. 2001;98:1268-1270)     

Analysis of SH2D1A mutations in patients with severe Epstein-Barr virus infections,Burkitt's lymphoma,and Hodgkin's lymphoma

Mutations or deletions in the SH2D1A (src homology 2 domain protein 1A) gene result in a severe immunodeficiency called X-linked lymphoproliferative (XLP) disease. XLP is primarily characterized by a defective immune response against the Epstein-Barr virus (EBV), resulting in an unusually severe and often fatal clinical course following EBV infection. The second major cause of death is the development of B cell lymphomas, both in EBV-infected and EBV-negative patients. To study whether the clinical manifestation of XLP gene defects and/or polymorphisms extends beyond the classically recognized phenotype, we analyzed patients for the presence of SH2D1A gene alterations who presented with fatal or nonfatal, yet unusually severe or chronic EBV infections, and other possibly EBV-associated diseases, such as Hodgkin's lymphomas or nonendemic Burkitt's lymphomas and Burkitt-type leukemias. We identified mutations of the SH2D1A gene only in the majority of patients presenting with fatal mononucleosis or an XLP family history, but not in any of the other patients studied. The only alteration determined was a polymorphism in the 5' region of the SH2D1A gene both in patient groups as well as in controls.     

Hemophagocytic lymphohistiocytosis due to germline mutations in SH2D1A, the X-linked lymphoproliferative disease gene

The hemophagocytic lymphohistiocytoses (HLH) comprise a heterogeneous group of disorders characterized by dysregulated activation of T cells and macrophages. Although some patients with HLH harbor perforin gene mutations, the cause of the remaining cases is not known. The phenotype of HLH bears a strong resemblance to X-linked lymphoproliferative disease (XLP), an Epstein-Barr virus (EBV)-associated immunodeficiency resulting from defects in SH2D1A, a small SH2 domain-containing protein expressed in T lymphocytes and natural killer cells. Here it is shown that 4 of 25 male patients with HLH who were examined harbored germline SH2D1A mutations. Among these 4 patients, only 2 had family histories consistent with XLP. On the basis of these findings, it is suggested that all male patients with EBV-associated hemophagocytosis be screened for mutations in SH2D1A. Patients identified as having XLP should undergo genetic counseling, and be followed long-term for development of lymphoma and hypogammaglobulinemia.     

Correlation of mutations of the SH2D1A gene and epstein-barr virus infection with clinical phenotype and outcome in X-linked lymphoproliferative disease

The purposes of this study were to determine the frequency of mutations in SH2D1A in X-linked lymphoproliferative disease (XLP) and the role of SH2D1A mutations and Epstein-Barr virus (EBV) infection in determining the phenotype and outcome of patients with XLP. Analysis of 35 families from the XLP Registry revealed 28 different mutations in 34 families-large genomic deletions (n = 3), small intragenic deletions (n = 10), splice-site (n = 3), nonsense (n = 3), and missense (n = 9) mutations. No mutations were found in 25 males, so-called sporadic XLP (males with an XLP phenotype after EBV infection but no family history of XLP) or in 9 patients with chronic active EBV syndrome. Of 304 symptomatic males in the XLP Registry, 38 had no evidence of EBV infection at first clinical manifestation. When fulminant infectious mononucleosis (FIM) was excluded, there was no statistical difference in the frequency of EBV infectivity in the other XLP phenotypes. Furthermore, there was no difference at age of first clinical manifestation between EBV(+) and EBV(-) males or in survival when patients with FIM were excluded. In conclusion, it was found that mutations in the SH2D1A gene are responsible for XLP but that there is no correlation between genotype and phenotype or outcome. It was also found that though EBV infection often results in FIM, it is unnecessary for the expression of other manifestations of XLP, and it correlates poorly with outcome. These results suggest that unidentified factors, either environmental or genetic (eg, modifier genes), contribute to the pathogenesis of XLP.     

Rapid detection of intracellular SH2D1A protein in cytotoxic lymphocytes from patients with X-linked lymphoproliferative disease and their family members

Mutations in the SH2D1A gene have been described in most patients with the clinical syndrome of X-linked lymphoproliferative disease (XLP). The diagnosis of XLP is still difficult given its clinical heterogeneity and the lack of a readily available rapid diagnostic laboratory test, particularly in patients without a family history of XLP. XLP should always be a consideration in males with Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis (EBV-HLH). Four-color flow cytometric analysis was used to establish normal patterns of SH2D1A protein expression in lymphocyte subsets for healthy subjects. Three of 4 patients with XLP, as confirmed by the detection of mutations in the SH2D1A gene, had minimal intracellular SH2D1A protein in all cytotoxic cell types. The remaining patient lacked intracellular SH2D1A protein in CD56+ natural killer (NK) and T lymphocytes and had an abnormal bimodal pattern in CD8+ T cells. Carriers of SH2D1A mutations had decreased SH2D1A protein staining patterns compared with healthy controls. Eleven males with clinical syndromes consistent with XLP, predominantly EBV-HLH, had patterns of SH2D1A protein expression similar to those of healthy controls. Four-color flow cytometry provides diagnostic information that may speed the identification of this fatal disease, differentiating it from other causes of EBV-HLH.     

X-Linked Lymphoproliferative Disease in an Adult

X-linked lymphoproliferative disease (XLP) is an inherited immunodeficiency characterized by an extreme susceptibility to Epstein-Barr virus (EBV) infection. Patients with XLP mainly present with the 3 clinical manifestations of fulminant infectious mononucleosis, lymphoproliferative disorder, and dysgammaglobulinemia and in rare cases have aplastic anemia and lymphocytic vasculitis.The causative gene for XLP was identified as SH2D1A/DSHP/SLAM-associated protein (SAP) in 1998, and genetic analysis has been used for the definite diagnosis of XLP. Diagnosis for most patients occurs at ages younger than 10 years, and there are few adult patients. Here we describe a 23-year-old man with hypogammaglobulinemia and EBV-associated hemophagocytic lymphohistiocytosis and a diagnosis of XLP. In addition, the patient showed type 1 helper T-cell (Th1) skewing, as has been described in Sap knock-out mice. Th1/Th2 imbalance in humans, as well as in mice, may play an important role in the pathogenesis of XLP.     

Clinical similarities and differences of patients with X-linked lymphoproliferative syndrome type 1 (XLP-1/SAP deficiency) versus type 2 (XLP-2/XIAP deficiency)

X-linked lymphoproliferative syndromes (XLP) are primary immunodeficiencies characterized by a particular vulnerability toward Epstein-Barr virus infection, frequently resulting in hemophagocytic lymphohistiocytosis (HLH). XLP type 1 (XLP-1) is caused by mutations in the gene SH2D1A (also named SAP), whereas mutations in the gene XIAP underlie XLP type 2 (XLP-2). Here, a comparison of the clinical phenotypes associated with XLP-1 and XLP-2 was performed in cohorts of 33 and 30 patients, respectively. HLH (XLP-1, 55%; XLP-2, 76%) and hypogammaglobulinemia (XLP-1, 67%; XLP-2, 33%) occurred in both groups. Epstein-Barr virus infection in XLP-1 and XLP-2 was the common trigger of HLH (XLP-1, 92%; XLP-2, 83%). Survival rates and mean ages at the first HLH episode did not differ for both groups, but HLH was more severe with lethal outcome in XLP-1 (XLP-1, 61%; XLP-2, 23%). Although only XLP-1 patients developed lymphomas (30%), XLP-2 patients (17%) had chronic hemorrhagic colitis as documented by histopathology. Recurrent splenomegaly often associated with cytopenia and fever was preferentially observed in XLP-2 (XLP-1, 7%; XLP-2, 87%) and probably represents minimal forms of HLH as documented by histopathology. This first phenotypic comparison of XLP subtypes should help to improve the diagnosis and the care of patients with XLP conditions.     

Cell surface receptors Ly-9 and CD84 recruit the X-linked lymphoproliferative disease gene product SAP

X-linked lymphoproliferative disease (XLP) is a rare immune disorder commonly triggered by infection with Epstein-Barr virus. Major disease manifestations include fatal acute infectious mononucleosis, B-cell lymphoma, and progressive dys-gammaglobulinemia. SAP/SH2D1A, the product of the gene mutated in XLP, is a small protein that comprises a single SH2 domain and a short tail of 26 amino acids. SAP binds to a specific motif in the cytoplasmic tails of the cell surface receptors SLAM and 2B4, where it blocks recruitment of the phosphatase SHP-2. Here it is reported that Ly-9 and CD84, 2 related glycoproteins differentially expressed on hematopoietic cells, also recruit SAP. Interactions between SAP and Ly-9 or CD84 were analyzed using a novel yeast 2-hybrid system, by COS cell transfections and in lymphoid cells. Recruitment of SAP is most efficient when the specific tyrosine residues in the cytoplasmic tails of Ly-9 or CD84 are phosphorylated. It is concluded that in activated T cells, the SAP protein binds to and regulates signal transduction events initiated through the engagement of SLAM, 2B4, CD84, and Ly-9. This suggests that combinations of dysfunctional signaling pathways initiated by these 4 cell surface receptors may cause the complex phenotypes of XLP. (Blood. 2001;97:3867-3874)     

X-linked lymphoproliferative syndrome presenting with systemic lymphocytic vasculitis

X-linked lymphoproliferative syndrome (XLP) is a rare, often fatal, primary immunodeficiency disease characterized by an abnormal response to Epstein-Barr virus (EBV) infection. The gene responsible for XLP has been identified as SH2D1A/DSHP/SLAM-associated protein (SAP). The major clinical manifestations include fulminant infectious mononucleosis, lymphoproliferative disorder, and dysgammaglobulinemia. Affected males uncommonly present with lymphocytic vasculitis in addition to aplastic anemia. In this study, we describe a Japanese XLP patient who presented with hypogammaglobulinemia following acute EBV-induced infectious mononucleosis in the infancy and later had systemic lymphocytic vasculitis and hemophagocytic lymphohistiocytosis in the adulthood, which resolved by steroid pulse therapy. The patient's SAP gene was found to harbor a missense mutation (His8Asp), presumably resulting in defective expression of SAP in T cells. Biopsy specimens of lung and skin disclosed that CD8+ T cells predominantly infiltrated vascular vessels. However, immunohistochemical examination showed that EBV-infected cells were not identifiable in the vessels. We propose that T-cell-mediated immune dysregulation in XLP can cause vasculitis by EBV infection-unrelated mechanism.     

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.     

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.     

Alterations of the X-linked lymphoproliferative disease gene SH2D1A in common variable immunodeficiency syndrome

X-linked lymphoproliferative (XLP) disease is a primary immunodeficiency caused by a defect in the SH2D1A gene. At least 3 major manifestations characterize its clinical presentation: fatal infectious mononucleosis (FIM), lymphomas, and immunoglobulin deficiencies. Common variable immunodeficiency (CVID) is a syndrome characterized by immunoglobulin deficiency leading to susceptibility to infection. In some patients with CVID, a defective btk or CD40-L gene has been found, but most often there is no clearly identified etiology. Here, 2 unrelated families in whom male members were affected by CVID were examined for a defect in the XLP gene. In one family previously reported in the literature as having progressive immunoglobulin deficiencies, 3 brothers were examined for recurrent respiratory infections, whereas female family members showed only elevated serum immunoglobulin A levels. A grandson of one of the brothers died of a severe Aspergillus infection secondary to progressive immunoglobulin deficiency, FIM, aplastic anemia, and B-cell lymphoma. In the second family, 2 brothers had B lymphocytopenia and immunoglobulin deficiencies. X-linked agammaglobulinemia syndrome was excluded genetically, and they were classified as having CVID. The occurrence of FIM in a male cousin of the brothers led to the XLP diagnosis. Because the SH2D1A gene was found altered in both families, these findings indicate that XLP must be considered when more than one male patient with CVID is encountered in the same family, and SH2D1A must be analyzed in all male patients with CVID. Moreover, these data link defects in the SH2D1A gene to abnormal B-lymphocyte development and to dysgammaglobulinemia in female members of families with XLP disease.     

X-linked lymphoproliferative syndrome: a genetic condition typified by the triad of infection, immunodeficiency and lymphoma

X-linked lymphoproliferative disease (XLP) is an inherited immunodeficiency characterized by the clinical triad of increased susceptibility to primary Epstein-Barr virus (EBV) infection, dysgammaglobulinaemia and lymphoma. Most cases are caused by germline mutations in the SH2D1A gene, which encodes the adaptor molecule Signalling Lymphocytic Activation Molecule (SLAM)-associated protein (SAP). Recently, a subset of patients with an XLP-like phenotype was found to carry mutations in XIAP, the gene encoding the X-linked inhibitor of apoptosis protein (XIAP). Studies of XLP patients and Sap-/- mice reveal that loss of SAP expression impairs immune cell activities, such as natural killer and CD8+ T cell cytotoxicity, T cell cytokine production, activation-induced cell death, germinal centre formation and natural killer T cell development. Efforts to dissect the diverse roles of SAP and XIAP are enhancing our understanding of immune cell biology and defining how genetic defects in these molecules predispose to EBV-specific as well as more general cellular and humoral immune dysfunction. These studies are also highlighting critical signalling pathways that might be amenable to pharmacological targeting to improve the treatment of XLP and other disorders associated with impaired antiviral and antitumour immunity.     

Altered lymphocyte responses and cytokine production in mice deficient in the X-linked lymphoproliferative disease gene SH2D1A/DSHP/SAP

We have introduced a targeted mutation in SH2D1A/DSHP/SAP, the gene responsible for the human genetic disorder X-linked lymphoproliferative disease (XLP). SLAM-associated protein (SAP)-deficient mice had normal lymphocyte development, but on challenge with infectious agents, recapitulated features of XLP. Infection of SAP- mice with lymphocyte choriomeningitis virus (LCMV) or Toxoplasma gondii was associated with increased T cell activation and IFN-gamma production, as well as a reduction of Ig-secreting cells. Anti-CD3-stimulated splenocytes from uninfected SAP- mice produced increased IFN-gamma and decreased IL-4, findings supported by decreased serum IgE levels in vivo. The Th1 skewing of these animals suggests that cytokine misregulation may contribute to phenotypes associated with mutation of SH2D1A/SAP.     

X-linked lymphoproliferative disease due to SAP/SH2D1A deficiency: a multicenter study on the manifestations, management and outcome of the disease

X-linked lymphoproliferative disease (XLP1) is a rare immunodeficiency characterized by severe immune dysregulation and caused by mutations in the SH2D1A/SAP gene. Clinical manifestations are varied and include hemophagocytic lymphohistiocytosis (HLH), lymphoma and dysgammaglobulinemia, often triggered by Epstein-Barr virus infection. Historical data published before improved treatment regimens shows very poor outcome. We describe a large cohort of 91 genetically defined XLP1 patients collected from centers worldwide and report characteristics and outcome data for 43 patients receiving hematopoietic stem cell transplant (HSCT) and 48 untransplanted patients. The advent of better treatment strategies for HLH and malignancy has greatly reduced mortality for these patients, but HLH still remains the most severe feature of XLP1. Survival after allogeneic HSCT is 81.4% with good immune reconstitution in the large majority of patients and little evidence of posttransplant lymphoproliferative disease. However, survival falls to 50% in patients with HLH as a feature of disease. Untransplanted patients have an overall survival of 62.5% with the majority on immunoglobulin replacement therapy, but the outcome for those untransplanted after HLH is extremely poor (18.8%). HSCT should be undertaken in all patients with HLH, because outcome without transplant is extremely poor. The outcome of HSCT for other manifestations of XLP1 is very good, and if HSCT is not undertaken immediately, patients must be monitored closely for evidence of disease progression.     

Defective B cell responses in the absence of SH2D1A

More than half of patients with X-linked lympho-proliferative disease, which is caused by a defect in the intracellular adapter protein SH2D1A, suffer from an extreme susceptibility to Epstein-Barr virus. One-third of these patients, however, develop dysgammaglobulenemia without an episode of severe mononucleosis. Here we show that in SH2D1A(-/-) mice, both primary and secondary responses of all Ig subclasses are severely impaired in response to specific antigens. Because germinal centers were absent in SH2D1A(-/-) mice upon primary immunization, and because SH2D1A was detectable in wt germinal center B cells, we examined whether SH2D1A(-/-) B cell functions were impaired. Using the adoptive cotransfer of B lymphocytes from hapten-primed SH2D1A(-/-) mice with CD4(+) T cells from primed wt mice into irradiated wt mice provided evidence that signal transduction events controlled by SH2D1A are essential for B cell activities resulting in antigen specific IgG production. Defects in naive SH2D1A(-/-) B cells became evident upon cotransfer with non-primed wt CD4(+) cells into Rag2(-/-) recipients. Thus, both defective T and B cells exist in the absence of SH2D1A, which may explain the progressive dysgammaglobulinemia in a subset of X-linked lympho-proliferative disease patients without involvement of Epstein-Barr virus.     

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.     

Identification of an<Emphasis Type="Italic">SH2D1A</Emphasis> mutation in a hypogammaglobulinemic male patient with a diagnosis of common variable immunodeficiency

Common variable immunodeficiency (CVID) is a highly heterogeneous disease with an unpredictable pattern. CVID appears to have an immunologic and clinical phenotype similar to some hereditary humoral immunodeficiencies, including X-linked lymphoproliferative disease (XLP). The differential diagnosis of CVID and XLP is clinically of importance, because the two diseases have markedly different prognoses and treatment. The recent identification of the XLP gene, known as SH2D1A, has permitted a definitive diagnosis of XLP. In this report, we describe a male patient with XLP who initially received a diagnosis of CVID and developed a fatal course. Using genetic analysis, we confirmed that the patient harbored the SH2D1A gene mutation. The results support the notion that the possibility of a SH2D1A gene mutation should be considered in hypogammaglobulinemic male patients before a diagnosis of CVID is made.