Successful Treatment of Epstein-Barr Virus-Associated Hemophagocytic Lymphohistiocytosis with HLH-94 Protocol

Hemophagocytic lymphohistiocytosis (HLH) is a rare, fatal disorder of children, affecting predominantly the mononuclear phagocytic system. Previous reports indicate that Epstein-Barr virus (EBV)-associated hemophagocytic lymphohistiocytosis (EBV-HLH) can also be fatal in many cases, although the prognosis for EBV-HLH is better than for the familial form of hemophagocytic lymphohistiocytosis. We treated four patients with EBV-HLH using immunochemotherapy including steroid, etoposide (VP-16), and cyclosporin, according to the HLH-94 protocol. All patients experienced persistent fever, cytopenia, and hypertriglyceridemia. Serological testing for EBV showed reactivated EBV infections in all patients. EBV DNA detected by PCR and EBV-encoded small RNA measured by in situ hybridization were confirmed in the patients' bone marrow specimens. Hemophagocytosis was shown in bone marrow aspirates and liver biopsy specimen. Complete remission was achieved in all patients after induction and continuation therapy for 4-10 months (median, 7 months) and was maintained for 15-27 months (median, 19 months) without the need for bone marrow transplantation. These results suggest that EBV-HLH can be effectively controlled by immunochemotherapy using the HLH-94 protocol

Hematopoietic Stem Cell Transplantation for the Treatment of Epstein-Barr Virus-Associated T- or NK-Cell Lymphoproliferative Diseases and Associated Disorders

Chronic active Epstein-Barr virus infection (CAEBV) is a prototype of EBV-associated T- and/or NK-cell (EBV+ T/NK-cell) lymphoproliferative disorders. Most subtypes of these are lethal. We established a unified treatment strategy composed of step 1 (immunochemotherapy: steroids, cyclosporine A, and etoposide), step 2 (multi-drug block chemotherapy), and step 3 (allogeneic hematopoietic stem cell transplantation; HSCT) for CAEBV and its related diseases. Allogeneic HSCT is the only cure for CAEBV with few exceptions. Primary-EBV infection-associated hemophagocytic lymphohistiocytosis (primary-EBV HLH) is also an EBV+ T/NK-cell lymphoproliferation. The nature of EBV+ T/NK cells in CAEBV and those in primary-EBV HLH differ. In primary-EBV HLH, most patients need step 1 only and some require step 2 for the successful induction of apoptosis in EBV-infected T cells; however, some exceptional patients require HSCT. We herein present our single institutional experience of CAEBV and primary-EBV HLH, together with that of post-transplant EBV+ T/NK-cell lymphoproliferative disease. We also discuss some practical points on HCST with a review of the literature

Autoimmune-Associated Hemophagocytic Syndrome/Macrophage Activation Syndrome

NonePublishe

Severe Epstein-Barr virus infection in primary immunodeficiency and the normal host

Epstein–Barr virus (EBV) infection is ubiquitous in humans, but the majority of infections have an asymptomatic or self-limiting clinical course. Rarely, individuals may develop a pathological EBV infection with a variety of life threatening complications (including haemophagocytosis and malignancy) and others develop asymptomatic chronic EBV viraemia. Although an impaired ability to control EBV infection has long been recognised as a hallmark of severe T-cell immunodeficiency, the advent of next generation sequencing has identified a series of Primary Immunodeficiencies in which EBV-related pathology is the dominant feature. Chronic active EBV infection is defined as chronic EBV viraemia associated with systemic lymphoproliferative disease, in the absence of immunodeficiency. Descriptions of larger cohorts of patients with chronic active EBV in recent years have significantly advanced our understanding of this clinical syndrome. In this review we summarise the current understanding of the pathophysiology and natural history of these diseases and clinical syndromes, and discuss approaches to the investigation and treatment of severe or atypical EBV infection

Role of syntaxin-11 and munc18-2 in lymphocyte cytotoxic granule exocytosis

Mutations in genes required for the exocytosis of cytotoxic granules by NK cells and cytotoxic T lymphocytes are associated with early-onset familial hemophagocytic lymphohistiocytosis (FHL). In this project, we examined how certain missense mutations in genes encoding syntaxin-11 and Munc18-2 abolish exocytosis and cause disease. Furthermore, we dissected the role of another protein suspected to play a role in cytotoxic granule exocytosis, VAMP8. In the first study, we characterized an FHL5 patient (Munc18-2 p.Q432X and p.S545L) who developed Hodgkin lymphoma with underlying Epstein-Barr virus (EBV) infection. The tissue displayed high infiltrates of cytotoxic T lymphocytes responsive to EBV-derived peptides, yet the cells had dramatically reduced Munc18- 2 protein levels and were unable to undergo cytotoxic granule exocytosis. The patient is an important example of how Munc18-2 missense mutations impairing exocytosis can lead to late-onset HLH and, due to decreased immunosurveillance, might result in cancer. In the second study, we examined the pathophysiological mechanism underlying an N-terminal syntaxin-11 mutation (syntaxin-11 p.L58P) associated with FHL4 in three unrelated patients. These patients displayed defective cytotoxic granule exocytosis despite the functionally important SNARE domain of syntaxin-11 being intact. As the p.L58 is an evolutionary conserved amino acid, we hypothesized that the mutation interrupts interactions with Munc18-2. Further, we determined whether other conserved N-terminal syntaxin-11 residues also contribute to Munc18-2 binding. We found that the interaction is dependent on both an intact syntaxin-11 N-terminal peptide as well as Habc domain because mutations in either completely abolished binding to Munc18-2. It is thus plausible that syntaxin-11, analogous to the syntaxin- 1 / Munc18-1 interaction, employs distinct binding modes to different domains of Munc18-2. The interruption of the syntaxin-11 / Munc18-2 interaction could explain the reduced syntaxin-11 expression levels. Lastly, cytotoxic granule exocytosis is dependent on several proteins being part of the fusion complex between a cytotoxic granule and plasma membrane, yet the v-SNARE mediating granule fusion remains elusive. In the third study, we suspected VAMP8 to play a key role in this fusion process. However, VAMP8 did not localize to cytotoxic granules but instead to recycling endosomes. Upon T cell receptor stimulation, recycling endosomes were recruited to the immune synapse and fused with the plasma membrane. As VAMP8 knockdown blocked cytotoxic granule release, we hypothesized that VAMP8+ recycling endosomes might deliver an important component for the cytotoxic fusion machinery to the plasma membrane. Indeed, recycling endosomes transported syntaxin-11 to the plasma membrane, with VAMP8 knockdown hampering syntaxin-11 delivery. In summary, these data provide a deeper understanding of FHL and the molecular mechanisms of cytotoxic granule exocytosis. We describe a possible link between FHL and cancer which may have diagnostic, prognostic and treatment implications for other FHL patients. Further, we show how N-terminal syntaxin-11 mutations can cause disease, with data hinting towards a meticulous series of interaction modes necessary for syntaxin-11 maintenance and cytotoxic granule secretion. Finally, we find that VAMP8 delivers syntaxin-11 to the immunological synapse in human cytotoxic lymphocytes, demonstrating an unexpected role of recycling endosomes in cytotoxic granule exocytosis

Hematopoietic stem cell transplantation in children with non-malignant disorders

Hematopoietic Stem Cell Transplantation (HSCT) is a curative option for specific non-malignant disorders in childhood, including hemoglobinopathies and primary immune deficiencies. Despite promising results in the recent years, many issues regarding timing of HSCT, donor selection, conditioning regimen and post-transplant care are currently open. Here, a cohort of 11 patients with Sickle Cell Disease transplanted after a Treosulfan-based conditioning regimen is described showing that this approach is suitable also when alternative donors are employed. Optimal modalities for HSCT in patients with Hemophagocytic Lymphohistiocytosis (HLH) are investigated through the analysis of outcomes of a 109 transplanted children. We demonstrate that active HLH should not preclude transplantation and that haploidentical HSCT is associated with dismal outcomes. Finally, data regarding supportive measure and psychological consequences of HSCT in children are presented