X-linked Lymphoproliferative Disease Research Articles

Highly sensitive detection of Epstein-Barr virus-infected cells by EBER flow FISH.

When Epstein-Barr virus (EBV) infection is suspected, identification of infected cells is important to understand the pathogenesis, determinine the treatment strategy, and predict the prognosis. We used the PrimeFlow™ RNA Assay Kit with a probe to detect EBV-encoded small RNAs (EBERs) and multiple surface markers, to identify EBV-infected cells by flow cytometry. We analyzed a total of 24 patients [11 with chronic active EBV disease (CAEBV), 3 with hydroa vacciniforme lymphoproliferative disorder, 2 with X-linked lymphoproliferative disease type 1 (XLP1), 2 with EBV-associated hemophagocytic lymphohistiocytosis, and 6 with posttransplant lymphoproliferative disorder (PTLD)]. We compared infected cells using conventional quantitative PCR methods and confirmed that infected cell types were identical in most patients. Patients with CAEBV had widespread infection in T and NK cells, but a small amount of B cells were also infected, and infection in patients with XLP1 and PTLD was not limited to B cells. EBV-associated diseases are believed to be complex pathologies caused by EBV infecting a variety of cells other than B cells. We also demonstrated that infected cells were positive for HLA-DR in patients with CAEBV. EBER flow FISH can identify EBV-infected cells with high sensitivity and is useful for elucidating the pathogenesis.

HAPLOIDENTICAL HEMATOPOIETIC STEM CELL TRANSPLANTATION FOR PAEDIATRIC PATIENTS WITH X-LINKED LYMPHOPROLIFERATIVE SYNDROME

The aim of this study was to investigate the prognostic factors of haploid hematopoietic stem cell transplantation in the treatment of X-linked lymphoproliferative syndrome. Seven children with X-linked lymphoproliferative syndrome diagnosed by XIAP gene analysis were enrolled. The conditioning regimens were tolerated in all seven patients, and the median time of neutrophil engraftment was 10 days (8-13 days), that of platelet engraftment was 21 days (14-24 days). STR-PCR analysis on the peripheral blood cells showed complete donor origins. Four cases developed Grade I acute graft versus host disease (aGVHD), one developed Grade III aGVHD (intestinal tract), and two cases had limited chronic GVHD. Four cases had cytomegalovirus (CMV) reactivation, and two cases had Epstein–Barr virus (EBV) reactivation. One case was diagnosed as pneumocystosis, and thrombotic microangiopathy (TMA) occurred in three cases. During the follow-up period (median time of 42 months), one patient died of TMA and six patients survived. Statistical analysis showed that the status of disease remission and the positive result of virus in blood before transplantation were independent prognostic factors. Haplo-HSCT might be a curative option for children with refractory X-linked lymphoproliferative syndrome. Low-intensity conditioning regimens may reduce transplant-related mortality and improve overall survival.

Single-Cell Transcriptomic Analysis of Epstein-Barr Virus-Associated Hemophagocytic Lymphohistiocytosis.

Epstein-Barr virus (EBV) infection can lead to infectious mononucleosis (EBV-IM) and, more rarely, EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH), which is characterized by a life-threatening hyperinflammatory cytokine storm with immune dysregulation. Interferon-gamma (IFNγ) has been identified as a critical mediator for primary HLH; however, the detailed role of IFNγ and other cytokines in EBV-HLH is not fully understood. In this study, we used single-cell RNA sequencing to characterize the immune landscape of EBV-HLH and compared it with EBV-IM. Three pediatric patients with EBV-HLH with different backgrounds,one with X-linked lymphoproliferative syndrome type 1 (XLP1), two with chronic active EBV disease (CAEBV), and two patients with EBV-IM were enrolled. The TUBA1B + STMN1 + CD8 + T cell cluster, a responsive proliferating cluster with rich mRNA detection, was explicitly observed in EBV-IM, and the upregulation of SH2D1A-the gene responsible for XLP1-was localized in this cluster. This proliferative cluster was scarcely observed in EBV-HLH cases. In EBV-HLH cases with CAEBV, upregulation of LAG3 was observed in EBV-infected cells, which may be associated with an impaired response by CD8 + T cells. Additionally, genes involved in type I interferon (IFN) signaling were commonly upregulated in each cell fraction of EBV-HLH, and activation of type II IFN signaling was observed in CD4 + T cells, natural killer cells, and monocytes but not in CD8 + T cells in EBV-HLH. In conclusion, impaired responsive proliferation of CD8 + T cells and upregulation of type I IFN signaling were commonly observed in EBV-HLH cases, regardless of the patients' background, indicating the key features of EBV-HLH.

Inborn errors of immunity and its clinical significance in children with lymphoma in China: a single-center study

ObjectiveTo investigate the incidence, clinical and genetic characteristics of pediatric lymphoma patients of China with inborn errors of immunity (IEI)-related gene mutations, which have not been fully studied. MethodFrom Jan. 2020 to Mar. 2023, IEI-related genetic mutations were retrospectively explored in 108 children with lymphomas admitted to Beijing Children's Hospital by NGS. Genetic rule and clinical characteristics as well as treatment outcomes were compared between patients with or without IEI-related gene mutations. ResultsA total of 17 patients (15.7 %) harbored IEI-associated mutations, including 4 cases with X-linked lymphoproliferative syndrome (XLP), 3 cases had mutations in tumor necrosis factor receptor superfamily 13B (TNFRSF13B), 2 cases with Activated p110 syndrome (APDS). Patients with IEI all had alteration of immunocompetence with decreased levels of immunoglobulin and lymphocyte subsets. Recurrent infection existed in 41.2 % of patients. The 18-month event-free survival (EFS) and the overall response rate (ORR) of patients with IEI are significantly lower than those without IEI (33.86% vs. 73.26 %, p = 0.011; 52.94% vs. 87.91 %, p = 0.002, respectively). In addition, patients with IEI had a higher progression disease (PD) rate of 23.5 % than those without IEI of 4.4 % (p = 0.006). ConclusionThe present study demonstrated that IEI-associated lymphomas were much more common than originally appreciated in pediatric lymphomas, and those were insensitive to treatment and more likely to progress or relapse. The genomic analysis and a thorough review of the medical history of IEI can be used to distinguish them from pediatric lymphomas without IEI, which are beneficial for the early diagnosis and direct intervention.

X-Linked Lymphoproliferative Syndrome: A Spectrum of Clinical and Immunological Profile and Novel Pathogenic Variants from Chandigarh, India

Introduction: X-linked lymphoproliferative syndrome (XLP) is a rare primary immune deficiency. Two types of XLP have been described: XLP-1 and XLP-2. Methods: We found 7 patients with XLP (3 had XLP-1 and 4 had XLP-2) after reviewing the data from Pediatric Immunodeficiency Clinic from 1997 to 2021. Results: Mean age at diagnosis was 3.8 years, and mean delay in diagnosis was 2.6 years. Five patients had recurrent episodes of infections. Four patients developed at least one episode of hemophagocytic lymphohistiocytosis (HLH) (2 with XLP-1 and 2 with XLP-2). Of these, 2 had recurrent HLH (both with XLP-2). Epstein-Barr virus (EBV) infection was detected in 2 (1 with XLP-1 and 1 with XLP-2). Both these patients had HLH. One child with XLP-2 had inflammatory bowel disease. Hypogammaglobulinemia was seen in 3 (2 with XLP-1 and 1 with XLP-2). Genetic analysis showed previously reported variants in 5, while 2 had novel variants (one in exon 7 of XIAP gene [c.1370dup p.Asn457Lysfs Ter16] and other had splice site variant in intron 1 of SH2D1A gene [c.138-2_138-1insG]). Episodes of HLH were managed with intravenous immunoglobulin (IVIg), methylprednisolone, oral prednisolone, cyclosporine, and rituximab. Inflammatory bowel disease was managed using oral prednisolone and azathioprine. One patient underwent haploidentical hematopoietic stem cell transplantation. One child with XLP-2 and WAS died because of fulminant pneumonia. Discussion/Conclusions: XLP should be considered as a strong possibility in any patient with features of HLH, repeated infections with hypogammaglobulinemia, persistent EBV infection, and early-onset IBD.

Population Pharmacokinetic Modeling for Twice-Daily Intravenous Busulfan in a Large Cohort of Pediatric Patients Undergoing Hematopoietic Stem Cell Transplantation-A 10-Year Single-Center Experience.

Reaching target exposure of busulfan-based conditioning prior to hematopoietic stem cell transplantation is vital for favorable therapy outcomes. Yet, a wide inter-patient and inter-occasion variability in busulfan exposure has been reported, especially in children. We aimed to identify factors associated with the variability of busulfan pharmacokinetics in 124 consecutive patients transplanted at the University Children's Hospital Zurich between October 2010 and February 2020. Clinical data and busulfan plasma levels after twice-daily intravenous administration were analyzed retrospectively by population pharmacokinetic modeling. The volume of distribution correlated with total body water. The elimination rate constant followed an age-dependent maturation function, as previously suggested, and correlated with the levels of serum albumin. Acute lymphoblastic leukemia reduced busulfan clearance by 20%. Clearance significantly decreased by 17% on average from the start to the third day of busulfan administration, in agreement with other studies. An average reduction of 31% was found in patients with hemophagocytic lymphohistiocytosis and X-linked lymphoproliferative disease. In conclusion, we demonstrate that in addition to known factors, underlying disease and serum albumin significantly impact busulfan pharmacokinetics in pediatric patients; yet, substantial unexplained variability in some patients remained. Thus, we consider repeated pharmacokinetic assessment essential to achieve the desired target exposure in twice-daily busulfan administration.

XIAP promotes the expansion and limits the contraction of CD8 T cell response through cell extrinsic and intrinsic mechanisms respectively.

XIAP is an endogenous inhibitor of cell death and inactivating mutations of XIAP are responsible for X-linked lymphoproliferative disease (XLP-2) and primary immunodeficiency, but the mechanism(s) behind these contradictory outcomes have been unclear. We report that during infection of macrophages and dendritic cells with various intracellular bacteria, XIAP restricts cell death and secretion of IL-1β but promotes increased activation of NFκB and JNK which results in elevated secretion of IL-6 and IL-10. Poor secretion of IL-6 by Xiap-deficient antigen presenting cells leads to poor expansion of recently activated CD8 T cells during the priming phase of the response. On the other hand, Xiap-deficient CD8 T cells displayed increased proliferation and effector function during the priming phase but underwent enhanced contraction subsequently. Xiap-deficient CD8 T cells underwent skewed differentiation towards short lived effectors which resulted in poor generation of memory. Consequently Xiap-deficient CD8 T cells failed to provide effective control of bacterial infection during re-challenge. These results reveal the temporal impact of XIAP in promoting the fitness of activated CD8 T cells through cell extrinsic and intrinsic mechanisms and provide a mechanistic explanation of the phenotype observed in XLP-2 patients.

An Atypical Presentation of X-linked Lymphoproliferative Disease type 1 Presenting with Seronegative Coccidioidomycosis

X-linked lymphoproliferative disease (XLP-1), an inborn error of immunity (IEI) caused by pathogenic variants in SH2D1A encoding signaling lymphocyte activation molecule-associated protein (SAP), is characterized by hemophagocytic lymphohistiocytosis (HLH), lymphoma, and hypogammaglobulinemia. We report the first known case of XLP-1 presenting with seronegative coccidioidomycosis. CaseA 13-year-old boy with persistent asthma, recurrent otitis media requiring four sets of tympanostomy tubes, chronic sinusitis, and Common Variable Immunodeficiency (CVID) presented with acute-on-chronic hypoxic respiratory failure. He had been off subcutaneous immunoglobulin (SCIg) replacement for 2 years. Sputum culture was positive for H. influenzae, treated with cefepime and azithromycin and supplemental oxygen for acute hypoxic respiratory failure. Fever persisted despite 48 hours of antibiotics. CT chest showed bronchiectasis with mediastinal, subcarinal and hilar adenopathy. Coccidioides immitis IgG and IgM were negative, but urine antigen was positive. There was no radiologic or cerebrospinal fluid evidence of disseminated coccidioidomycosis.Immunologic workup revealed undetectable IgG, IgA, IgM, and IgE (table 1). Lymphocyte subsets showed severe T and NK cell lymphopenia. Total B cell count was normal, but he had decreased CD19+27+ and transitional B cells, with absent switched memory B cells and no plasmablasts (table 1). Lymphocyte proliferation to mitogens/antigens was decreased. Serum ferritin was normal, and EBV PCR was negative. A targeted 429-gene panel identified a hemizygous variant of uncertain significance (VUS) in SH2D1A, c.82_102dup (p.Ser28_Ser34dup). SAP expression was absent in CD4+ T cells and NK cells with a bimodal expression in CD8+ T cells, suggesting possible mosaicism in this subset. He was diagnosed with X-linked lymphoproliferative disease 1 (XLP-1) and treated with fluconazole, trimethoprim-sulfamethoxazole prophylaxis, and IgG replacement (1 g/kg intravenous initially, then transitioned to weekly SCIg targeting an IgG >1000 mg/dL), with clinical improvement, resolution of fevers and acute hypoxia. He was referred for hematopoietic cell transplant evaluation.Coccidioidomycosis has not been described in a new diagnosis of XLP-1 and should be considered in this IEI. Coccidioidomycosis susceptibility has been reported in other IEIs including impaired interleukin-12/interferon-gamma axis signaling, STAT3 loss of function, chronic granulomatous disease, and recently cytidine triphosphate synthase 1 (CTPS1) deficiency.Table 1Patient’s immunologic variables compared to reference range. Absolute values are shownImmunologic VariablePatient ValuesReference RangeIgG<70 (L)<70 mg/dLIgA<15 (L)<15 mg/dLIgM<8 (L)<8 mg/dLIgE<1.5 (L)<1.5 IU/uLTotal CD4+ T Cells11 (L)570–2400 cells/uLTotal CD8+ T Cells63 (L)210–1200 cells/uLTotal CD19+ B cells173165–1154 cells/uLCD19+ CD24++ CD38++ (Transitional B Cells)0 (L)8–392 cells/uLCD19+CD24+CD38+ (Naïve B Cells)12159–1146 cells/uLCD19+CD27-(Naïve B cells)169140–2269 cells/uLCD19+ CD27+ CD38+ IgM- (Plasmablasts)0<30 cells/uLCD19+CD27+IgD-IgM- (Switched-memory B cells)0 (L)6–190 cells/uLCD16+ CD56+ (NK Cells)32 (L)78–470 cells/uLL – low

Clinical Case of X-Linked Lymphoproliferative Syndrome Burdened with Hemophagocytic Lymphohistiocytosis and Crohn's Disease

Background. X-linked lymphoproliferative (XLP) syndrome is hereditary disease with the incidence of 1-3 per 1 million born boys. This clinical case demonstrates a rare picture of XLP type 2 manifestation without prior Epstein-Barr virus.Clinical case description. Boy D., 15 years old, was admitted to Morozovskaya Children's City Hospital with complaints on fever, abdominal pain, loose stools, weight loss. The past medical history included hemophagocytic syndrome (remission) and acute erythema nodosum. We have performed several studies: abdominal ultrasound (hepatomegaly, dynamic changes in the intestine: parts of the small intestine were enlarged and walls were thickened, mass peristalsis, walls of transverse colon and descending colon are thickened up to 5 mm, mesenteric lymphadenopathy), rectosigmoidoscopy (high-activity ulcerative proctosigmoiditis corresponds to Crohn's disease), biochemical and clinical blood tests (active hemophagocytic syndrome), coagulogram (secondary hypocoagulation), myelogram (no data on hemoblastosis or aplastic condition). Virological blood tests (CMV, EBV, HHV-VI): negative. Laboratory and instrumental tests have revealed recurrence of hemophagocytic syndrome and Crohn's disease. The child was consulted by rheumatologist, hematologist, gastroenterologist, geneticist, neurologist, and clinical pharmacologist. The primary immune deficiency disease was suspected in this patient due to his medical history. Molecular genetic study was performed (deletion including the XIAP gene was revealed) and the diagnosis of primary immune deficiency was verified: X-linked lymphoproliferative syndrome type 2. Thus, allogeneic haematopoietic stem cell transplantation (HSCT) was performed.Conclusion. XLP diagnosis and management require multidisciplinary approach. The early diagnosis is crucial due to the high risk of secondary complications development that can significantly worsen the disease's prognosis. Allogeneic HSCT is the only effective treatment for the disease.

Masks of cancers in the practice of an infectious disease doctor

The purpose of this work is to remind doctors of practical medicine about the importance of differential diagnosis with cancers in general pediatric practice and to increase the vigilance of clinicians regarding the similarity of manifestations of oncology and infectious diseases on the example of specific clinical cases. We conducted an empirical, descriptive study of 4 clinical cases of cancers in children. We selected them among 21 patients who were diagnosed with cancer during the inpatient treatment at the Kyiv City Children’s Infectious Disease Hospital in 2014–2019. The first clinical case describes a brain neoplasm that was initially thought to be acute VZV encephalitis in an 11-year-old child. The second is a case of acute leukemia in a 3-year-old child who was hospitalized with suspected meningococcal infection. In the third case, we presented a 7-year-old patient who was admitted with infectious mononucleosis and as a result, was diagnosed with hemophagocytic syndrome, immunodeficiency and Duncan disease. The latest case demonstrates the combination of tuberculous meningitis and cerebral astrocytoma in a 15-year-old patient, which was initially mistaken for viral encephalitis. Conclusions. Awareness of cancers is important in the diagnosis of infectious nosologies. Dynamic monitoring and the use of a wide range of laboratory and instrumental methods allows to prevent diagnostic errors and to seek treatment in a timely manner.

370 - The importance of early detection in x-linked lymphoproliferative syndrome type 1: the story of three family members

370 - The importance of early detection in x-linked lymphoproliferative syndrome type 1: the story of three family members

Rare diseases presenting with hemophagocytic lymphohistiocytosis.

Hemophagocytic lymphohistiocytosis (HLH) is a potentially fatal hyperinflammatory disorder characterized by hypercytokinemia caused by excessive activation of cytotoxic T cells and macrophages. HLH is caused by a variety of factors and is classified into primary and secondary HLH. Familial HLH (FHL) types 1-5, X-linked lymphoproliferative syndrome types 1 and 2, and FHL syndrome with hypopigmentation are all examples of primary HLH. Secondary HLH, on the other hand, is linked to infections, malignant tumors, autoimmune diseases, and other diseases. The causes of HLH vary, and finding the underlying disease is critical for diagnosis and treatment. The majority of HLH is caused by the aforementioned conditions; however, approximately 10% of cases are caused by rare diseases such as inborn errors of immunity (IEI) and inborn errors of metabolism (IEM). Novel IEI, such as RhoG, MAP kinase activating death domain, TIM3, and ZNFX1 deficiencies, have recently been identified as causes of HLH. IEM patients are rarely associated with HLH. Surprisingly, children with lysinuric protein intolerance and lysosomal acid lipase deficiency (Wolman disease) frequently develop HLH. This review focuses on the most recent knowledge of HLH caused by rare diseases such as IEI and IEM.

SAP DEFICIENCY PRESENTING IN A CHILD WITH RECURRENT DIFFUSE LARGE B CELL LYMPHOMA

<h3>Introduction</h3> SLAM–associating protein deficiency (SAP deficiency), also known as X-linked lymphoproliferative disease (XLPD Type 1), is an inborn error of immunity caused by a hemizygous variant in the <i>SH2D1A</i> gene, which encodes this protein. SAP is essential for immunity to Epstein Barr Virus (EBV) with deficiency leading to fulminant EBV infection, hemophagocytic lymphohistiocytosis (HLH) and B-cell lymphomas. Herein, we describe a child who presented with recurrent B cell lymphoma and was determined to have SAP deficiency. <h3>Case Description</h3> The patient is a 7 yo previously healthy male who presented with throat pain, enlarged tonsils and cervical lymphadenopathy. He failed multiple courses of antibiotics, and tonsillar incision and drainage was ineffective. Tonsillar biopsy showed mature large B-cell lymphoma, stage II. He responded to chemotherapy, but after 3 months off therapy had relapse of disease with a tonsillar mass, confirmed by biopsy. On further work-up, testing showing very low SAP expression in lymphocytes: %SAP expressed in CD8+ Tcells 1% (ref range >62%), CD8- T cells 0% (ref range >64%), CD56 NK cells 0% (ref range >55%). XIAP expression in lymphocytes was normal. This was consistent with XLPD Type 1 or SAP deficiency. <h3>Conclusion</h3> Patients with SAP may present in infancy or in childhood with clinical presentation derived by an increased susceptibility to EBV. However, the phenotype is variable making recognition challenging without fulminant EBV infection, HLH or hypogammaglobulinemia. Immunologists should have a high suspicion for SAP deficiency in patients with recurrent lymphomas as diagnosis changes management with hematopoietic stem cell transplant leading to cure.

X-LINKED LYMPHOPROLIFERATIVE DISEASE: DIAGNOSTIC CHALLENGE IN A MIDDLE-AGED MALE

<h3>Introduction</h3> X-Linked Lymphoproliferative Disease Type 1 (XLP1) is a rare disease of males caused by mutation in the gene <i>SH2D1A</i> and is characterized by vulnerability to EBV infection, lymphoma and dysgammaglobulinemia. Fulminant infectious mononucleosis in early childhood is the most common clinical manifestation, but on rare occasions XLP1 does not present until adulthood. <h3>Case Description</h3> We present a 43-year-old male with a history of recurrent sinusitis and bronchitis and leukopenia since childhood. He had EBV infection when he was 18 years old complicated by jaundice and hepatitis that required treatment with corticosteroids. At the age of 42, he developed ITP and was found to have mild splenomegaly. Serum immunoglobulins were mildly abnormal with IgG of 575, IgM of 762 and IgA of 145 mg/dL. Lymphocyte immunophenotyping was within normal limits and serum protein electrophoresis and serum free light chains were normal. Bone marrow biopsy was unremarkable. Invitate PID panel was performed, which revealed a pathogenic variant in SH2D1A gene (c.2T>C). SAP expression by flow cytometry revealed absence in NK cells but present in 17% of CD8+ T cell population suggestive of a somatic reversion in this population. He had mildly decreased NK cell function and positive EBV serology. <h3>Discussion</h3> We present a case of XLP1 diagnosis in adulthood with a history of EBV infection of moderate severity and mild initial immunologic abnormalities. In patients with somatic reversion in CD8+ T cells, milder disease may be more common and genetic testing should be considered early. The management options including bone marrow transplant should be carefully considered.

Epstein Barr virus-mediated transformation of B cells from XIAP-deficient patients leads to increased expression of the tumor suppressor CADM1

X-linked lymphoproliferative disease (XLP) is either caused by loss of the SLAM-associated protein (SAP; XLP-1) or the X-linked inhibitor of apoptosis (XIAP; XLP-2). In both instances, infection with the oncogenic human Epstein Barr virus (EBV) leads to pathology, but EBV-associated lymphomas only emerge in XLP-1 patients. Therefore, we investigated the role of XIAP during B cell transformation by EBV. Using humanized mice, IAP inhibition in EBV-infected mice led to a loss of B cells and a tendency to lower viral titers and lymphomagenesis. Loss of memory B cells was also observed in four newly described patients with XIAP deficiency. EBV was able to transform their B cells into lymphoblastoid cell lines (LCLs) with similar growth characteristics to patient mothers’ LCLs in vitro and in vivo. Gene expression analysis revealed modest elevated lytic EBV gene transcription as well as the expression of the tumor suppressor cell adhesion molecule 1 (CADM1). CADM1 expression on EBV-infected B cells might therefore inhibit EBV-associated lymphomagenesis in patients and result in the absence of EBV-associated malignancies in XLP-2 patients.

Immune-mediated inflammatory diseases with chronic excess of serum interleukin-18.

Review: Interleukin-18 (IL-18) is a proinflammatory cytokine that promotes various innate immune processes related to infection, inflammation, and autoimmunity. Patients with systemic juvenile idiopathic arthritis and adult-onset Still’s disease exhibit chronic excess of serum IL-18, which is associated with a high incidence of macrophage activation syndrome (MAS), although the mechanisms of IL-18 regulation in such diseases remain largely unknown. Similar elevation of serum IL-18 and susceptibility to MAS/hemophagocytic lymphohistiocytosis (HLH) have been reported in monogenic diseases such as X-linked inhibitor of apoptosis deficiency (i.e., X-linked lymphoproliferative syndrome type 2) and NLRC4-associated autoinflammatory disease. Recent advances in molecular and cellular biology allow the identification of other genetic defects such as defects in CDC42, PSTPIP1, and WDR1 that result in high serum IL-18 levels and hyperinflammation. Among these diseases, chronic excess of serum IL-18 appears to be linked with severe hyperinflammation and/or predisposition to MAS/HLH. In this review, we focus on recent findings in inflammatory diseases associated with and probably attributable to chronic excess of serum IL-18 and describe the clinical and therapeutical relevance of understanding the pathology of this group of diseases.

Allosteric inhibition of SHP2 rescues functional T-cell abnormalities in SAP deficiency

X-linked lymphoproliferative disease (XLP) is a primary immunodeficiency arising from SH2D1A mutations leading to loss of SLAM-associated protein (SAP). SAP is an intracellular adaptor protein that binds to SLAM family receptors and is expressed in specific lymphoid lineages. In T cells, SAP relays activatory signals from the T-cell receptor but in its absence SH2 containing protein tyrosine phosphase-1 (SHP1), SH2 containing protein tyrosine phosphase-2 (SHP2), and SH2 containing inositol 5'-phosphatase proteins (SHIP) induce T-cell inhibitory signals leading to abnormal T-cell responses. This results in severe clinical manifestations including immune dysregulation, dysgammaglobulinemia, lymphoma, and hemophagocytic lymphohistiocytosis. Current treatment relies on supportive therapies including immunoglobulin replacement and symptom-directed therapy, with hematopoietic stem cell transplant offering the only curative option. As most XLP symptoms are due to defective T-cell function, this study investigated whether inhibition of SHP2 can restore cellular function in the absence of SAP. Healthy donor and XLP patient T cells were activated with anti-CD3/CD28 in T-cell media supplemented with a SHP2 inhibitor (RMC-4550 invitro for 24 hours) and functional assays were performed to assess follicular TH (TFH) cell function, CD8 cytotoxicity, and sensitivity to restimulation-induced cell death. Additionally, SAP-deficient (SAPy/-) mice were treated with RMC-4550 before T-cell mediated challenge with 4-hydroxy-3-nitrophenylacetly conjugated chicken gammaglobulin and subsequent assessment of humoral immunity analyzing TFH cell population, germinal center formation, and antigen-dependent immunoglobulin secretion. This study shows that the use of RMC-4550 restores T-cell function in XLP patient cells and a SAPy/- model, demonstrating restoration of TFH cell function through immunoglobulin and cytokine secretion analysis alongside rescue of cytotoxicity and restimulation-induced cell death. These data suggest that SHP2 inhibitors could offer a novel and effective targeted treatment approach for patients with XLP.

Genome Editing With TALEN, CRISPR-Cas9 and CRISPR-Cas12a in Combination With AAV6 Homology Donor Restores T Cell Function for XLP.

X-linked lymphoproliferative disease is a rare inherited immune disorder, caused by mutations or deletions in the SH2D1A gene that encodes an intracellular adapter protein SAP (Slam-associated protein). SAP is essential for mediating several key immune processes and the immune system - T cells in particular - are dysregulated in its absence. Patients present with a spectrum of clinical manifestations, including haemophagocytic lymphohistiocytosis (HLH), dysgammaglobulinemia, lymphoma and autoimmunity. Treatment options are limited, and patients rarely survive to adulthood without an allogeneic haematopoietic stem cell transplant (HSCT). However, this procedure can have poor outcomes in the mismatched donor setting or in the presence of active HLH, leaving an unmet clinical need. Autologous haematopoeitic stem cell or T cell therapy may offer alternative treatment options, removing the need to find a suitable donor for HSCT and any risk of alloreactivity. SAP has a tightly controlled expression profile that a conventional lentiviral gene delivery platform may not be able to fully replicate. A gene editing approach could preserve more of the endogenous regulatory elements that govern SAP expression, potentially providing a more optimum therapy. Here, we assessed the ability of TALEN, CRISPR-Cas9 and CRISPR-Cas12a nucleases to drive targeted insertion of SAP cDNA at the first exon of the SH2D1A locus using an adeno-associated virus serotype 6 (AAV6)-based vector containing the donor template. All nuclease platforms were capable of high efficiency gene editing, which was optimised using a serum-free AAV6 transduction protocol. We show that T cells from XLP patients corrected by gene editing tools have restored physiological levels of SAP gene expression and restore SAP-dependent immune functions, indicating a new therapeutic opportunity for XLP patients.

Hematological manifestations of X-linked lymphoproliferative disease

Zespół limfoproliferacyjny sprzężony z chromosomem X (XLP) to rzadka choroba genetyczna występująca głównie u chłopców. Istnieją dwa rodzaje choroby, każdy o innej charakterystyce klinicznej i genetycznej. XLP1 jest spowodowane mutacją w genie SH2D1A, a XLP2 mutacją w genie XIAP/BIRC. Wady genetyczne prowadzą do dysfunkcji układu odpornościowego. Objawy kliniczne mogą wykazywać różnice, nawet wśród członków rodziny, którzy są nosicielami tej samej mutacji. Manifestacja jest zespołem zaburzeń hematologicznych: choroba objawia się najczęściej limfohistiocytozą hemofagocytarną, dysgammaglobulinemią, piorunującą mononukleozą zakaźną, splenomegalią, występowaniem chłoniaków z komórek B zlokalizowanych w pobliżu zastawki krętniczo-kątniczej i zapaleniem jelita grubego. Diagnostyka różnicowa powinna przede wszystkim uwzględniać wrodzone niedobory odporności. XLP jest chorobą śmiertelną, ale wraz z rozwojem nowych opcji leczenia, oczekiwana długość życia pacjentów znacznie się wydłużyła. Obecnie jedynym ostatecznym sposobem leczenia jest wczesne allogeniczne przeszczepienie krwiotwórczych komórek macierzystych. Pojawienie się nasilonych objawów przed przeszczepieniem zmniejsza szanse pacjenta na sukces terapeutyczny. W związku z tym bardzo ważne jest postawienie wczesnej diagnozy. Nowe terapie, które obejmują hamowanie enzymów, terapię genową i edycję genów budzą nadzieje klinicystów. Pacjentom i ich rodzinom należy zapewnić poradnictwo genetyczne oraz możliwość wczesnej diagnostyki molekularnej.

Patients with XLP type 1 have variable numbers of NKT cells.

X-linked lymphoproliferative disease (XLP1) is a rare primary immunodeficiency that usually presents in early childhood. Patients with XLP1 have been reported to have absent NKT cells, and it has been suggested that this can be diagnostic for the disorder. Whilst NKT frequency in adults is variable, little is known about their frequency in children. Therefore, we established a paediatric reference range for these cells. In contrast to previous reports, in our cohort of XLP1 patients, NKT cell numbers were found to be variable, and we would advise against using the finding of NKT cells to exclude a diagnosis of XLP1.