SAP mediates specific cytotoxic T-cell functions in X-linked lymphoproliferative disease

Cytotoxic T cells (CTLs) and natural killer cells play a major role in the immune response to Epstein-Barr virus (EBV) infection. In X-linked lymphoproliferative (XLP) disease, a severe immunodeficiency, immunodysregulatory phenomena are observed following EBV infection, suggesting that defects exist in these effector populations. The gene defective in XLP is SAP (signaling lymphocytic activation molecule [SLAM]-associated protein), an adaptor protein that mediates signals through SLAM and other immunoglobulin superfamily receptors including 2B4. We generated EBV-specific T-cell lines from controls and XLP patients and examined CTL function in response to different stimuli. We show that XLP patients can generate EBV-T-cell lines that are phenotypically similar to those from controls. XLP patient EBV-T-cell lines showed a significant decrease in interferon-gamma (IFN-gamma) production in response to 2B4 and autologous EBV-transformed lymphoblastoid cell line (LCL) stimulation but not in response to SLAM. Furthermore, XLP EBV-T-cell lines demonstrated markedly decreased cytotoxic activity against autologous LCLs. By retroviral gene transfer of the SAP gene into XLP EBV-T-cell lines, we show reconstitution of IFN-gamma production and of cytotoxic activity confirming SAP-dependent defects. These studies demonstrate that in XLP the lack of SAP affects specific signaling pathways resulting in severe disruption of CTL function.     

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.     

The X-linked lymphoproliferative syndrome gene product SH2D1A associates with p62dok (Dok1) and activates NF-kappa B

The X-linked lymphoproliferative syndrome (XLP) is a genetic disorder in which affected males have a morbid or fatal response to Epstein-Barr virus infection. The XLP deficiency has been mapped to a gene encoding a 128-residue protein, SH2D1A, which is comprised principally of a Src homology 2 (SH2) domain. We now report that SH2D1A associates with Dok1, a protein that interacts with Ras-GAP, Csk, and Nck. An SH2D1A SH2 domain mutant that has been identified in XLP does not associate with Dok1, in accord with the hypothesis that this interaction is linked to XLP. The association of SH2D1A with Dok1 also depends on phosphorylation of Dok1 Y(449) in the sequence ALYSQVQK. Further, overexpression of SH2D1A is found to activate NF-kappaB in 293T cells. NF-kappaB activation by SH2D1A does not depend on the wild-type SH2 domain and is inhibited by a dominant-negative IkappaB kinase beta. Thus, SH2D1A can affect multiple intracellular signaling pathways that are potentially important in the normal effective host response to Epstein-Barr virus infection.     

X-linked lymphoproliferative disease: genetic lesions and clinical consequences

X-linked lymphoproliferative disorder (XLP) was first described almost 30 years ago; remarkably, the three major manifestations of XLP, fulminant infectious mononucleosis (FIM), lymphoma, and dysgammaglobulinemia, are all described in the report of the initial kindred. Subsequent establishment of an XLP registry has led to recognition of more unusual phenotypes in affected males; concurrently, much progress has been made in caring for boys with XLP, including treatment for the three major phenotypes, and curative bone marrow transplantation (BMT). The immunologic and genetic mechanisms resulting in XLP have also been intensively studied. Several years ago, the gene defective in XLP was identified as SAP (SLAM-associated protein), and recent data suggest that SAP plays a broad role in immune signaling. Here, we review the clinical manifestations and therapy of XLP, and briefly summarize recent research into the structure and function of SAP.     

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.     

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.     

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.     

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.     

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.     

Primary Immunodeficiencies Inducing EBV-Associated Severe Illnesses

Epstein-Barr virus (EBV) is a ubiquitous human gamma-herpesvirus that infects about 95% of the adult population. The majority of primary infections occurs in early childhood and is generally subclinical; it can cause infectious mononucleosis (IM), which is usually a self-limiting lymphoproliferative disorder. However, infection of EBV occasionally results in severe, often lethal diseases, which include fatal IM, hemophagocytic syndrome, polyclonal lymphoproliferative disorders, and malignant lymphoma. These severe EBV-related illnesses occur secondary to some primary immunodeficiency diseases showing inefficient immune reaction to EBV. One example is X-linked lymphoproliferative disease (XLP), which is caused by mutations in the SLAM-associated protein (SAP) gene. The major clinical manifestations of XLP are fulminant IM, malignant lymphoma and dysgammaglobulinemia. Aplastic anemia, virus-associated hemophagocytic syndrome, and vasculitis have also been reported in XLP. We have developed a flow cytometric method using the anti-SAP monoclonal antibody to search for XLP. This clinically useful assay has successfully been used to identify XLP patients in Japan. In this review, clinical and mutational characteristics of XLP in Japan are mainly described. In addition, it is shown that the similar situations to XLP can occur in other primary immunodeficiencies involving T-cell killing function, such as autoimmune lymphoproliferative syndrome caused by Fas gene mutations or familial hemophagocytic lymphohistiocytosis caused by perforin gene mutations. Finally, the EBV-related terrible disease condition, namely chronic active EBV infection, which is common in Asian areas but its genetic background remains to be elucidated, will be touched on.     

Loss of circulating CD27+ memory B cells and CCR4+ T cells occurring in association with elevated EBV loads in XLP patients surviving primary EBV infection

Detailed longitudinal studies of patients with X-linked lymphoproliferative disease (XLP) may increase our understanding of the immunologic defects that contribute to the development of lymphoma and hypogammaglobulinemia in XLP. We describe progressive changes observed in immunoglobulin concentrations, lymphocyte subsets, and Epstein-Barr virus (EBV) loads occurring in a 2-year period in a newly infected, but otherwise healthy, carrier (patient 9). We compare these findings with those observed in the patient's brother, who had hypogammaglobulinemia and XLP (patient 4). Immunoglobulin G (IgG), IgM, and IgA concentrations increased in patient 9 during acute EBV infection, but thereafter they decreased steadily to concentrations consistent with hypogammaglobulinemia, reaching a plateau 5 months after infection. In both patients, CD19+ B-lymphocyte rates remained lower than 3%, with a contraction of the B-cell memory compartment (CD27+ CD19+/CD19+) to 20% (normal range, 32%-56%). T-lymphocyte subpopulations showed a reduction in CD4+ T-cell counts and a permanent CD8+ T-cell expansion. Interestingly, CXCR3 memory TH1 cells were expanded and CCR4+ TH2 lymphocytes were reduced, suggesting that abnormal skewing of memory T-cell subsets might contribute to reduced antibody synthesis. Despite an expanded number of CD3+CD8+ lymphocytes, increased EBV loads occurred in both patients without overt clinical symptoms of mononucleosis, lymphoproliferative disease, or lymphoma.     

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.     

Large deletion of the X-linked lymphoproliferative disease gene detected by fluorescence in situ hybridization

The X-linked lymphoproliferative disease (XLP) is an inherited immunodeficiency characterized by an abnormal responses to infection with Epstein-Barr virus (EBV), resulting in fatal infectious mononucleosis, hypogammaglobulinemia, virus-associated hemophagocytic syndrome, and malignant lymphoma. Mutations in the gene coding for a T cell-specific SLAM-associated protein (SAP) have been recently identified in XLP patients. We report on a 1-year-old boy representing fulminant hemophagocytic syndrome. He developed high fever, lymphadenopathy, hepatosplenomegaly with liver dysfunction, and pancytopenia with marrow hemophagocytosis. EBV DNA was abnormally increased in the blood. Polymerase chain reaction failed to amplify SAP mRNA and genomic DNA products from the patient' As peripheral blood. A large deletion of the SAP gene was confirmed by fluorescence in situ hybridization (FISH). FISH analysis also disclosed that the patient's mother was a carrier. We conclude that FISH can be useful in the diagnosis of XLP with large deletions of the SAP gene and its carrier state.     

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.     

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.     

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.     

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.     

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.     

Lentiviral-vector-mediated gene therapy for X-linked lymphoproliferative disease restores humoral and cellular functions

BackgroundX-linked lymphoproliferative disease (XLP) arises from mutations in the gene encoding SAP, an intracellular adaptor protein expressed in T cells, natural killer (NK) cells, and natural killer T (NKT) cells. SAP deficiency causes abnormalities of NK cell cytotoxicity, NKT cell development, and T-cell-dependent humoral function. Clinical manifestations are characterised by haemophagocytic lymphohistiocytosis (HLH), lymphoma, and dysgammaglobulinaemia. Curative treatment is limited to allogeneic haemopoietic stem-cell transplantion (HSCT). Somatic gene therapy offers a potential cure in XLP. We have developed a lentiviral mediated gene therapy strategy to correct immune defects in XLP.MethodsWe designed a lentiviral vector incorporating codon-optimised human SAP cDNA and green fluorescent protein (GFP) driven by the elongation factor-1 short (EFS) promoter. Haemopoietic stem-cell progenitors from SAP-deficient mice were transduced with SAP-GFP (n=10) or GFP only (n=9) vectors before transplantation into irradiated SAP-deficient recipients. Animals were sacrificed 3 months later, 10 days post vaccination with NP-CGG to assess functional humoral reconstitution.FindingsBoth SAP and GFP expression was evident in bone marrow, thymus, spleen, and peripheral blood cells. NK cell cytotoxicity was restored to wild type levels in mice receiving the SAP-GFP vector, and NKT cell development was seen in SAP-GFP transduced mice at levels significantly higher than those seen in SAP-deficient or control mice. Baseline IgG, IgM, IgG1, and IgG3 levels were significantly increased and T-cell-dependent humoral responses were also restored, with SAP-GFP transduced mice having levels of NP-specific immunoglobulin that were significantly higher than SAP-deficient mice or controls.InterpretationWe demonstrate correction of cellular and humoral defects in SAP-deficient mice through lentiviral-vector-mediated gene transfer into haemopoietic progenitor cells, providing proof of concept for gene therapy in XLP.FundingWellcome Trust and Leukaemia Lymphoma Research.     

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.