DOCK8 deficiency: Insights into pathophysiology, clinical features and management

Combined immunodeficiency (CID) refers to inborn errors of human T cells that also affect B cells because of the T cell deficit or an additional B cell–intrinsic deficit. In this study, we report six patients from three unrelated families with biallelic loss-of-function mutations in RLTPR , the mouse orthologue of which is essential for CD28 signaling. The patients have cutaneous and pulmonary allergy, as well as a variety of bacterial and fungal infectious diseases, including invasive tuberculosis and mucocutaneous candidiasis. Proportions of circulating regulatory T cells and memory CD4+ T cells are reduced. Their CD4+ T cells do not respond to CD28 stimulation. Their CD4+ T cells exhibit a "Th2" cell bias ex vivo and when cultured in vitro, contrasting with the paucity of "Th1," "Th17," and T follicular helper cells. The patients also display few memory B cells and poor antibody responses. This B cell phenotype does not result solely from the T cell deficiency, as the patients’ B cells fail to activate NF-κB upon B cell receptor (BCR) stimulation. Human RLTPR deficiency is a CID affecting at least the CD28-responsive pathway in T cells and the BCR-responsive pathway in B cells.

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Dual T cell- and B cell-intrinsic deficiency in humans with biallelic RLTPR mutations.

Malignancies occur with a higher incidence rate and manifest earlier in life in patients with primary immunodeficiency disorders (PIDs) than in the general population. However, no universal mechanism of malignancy predisposition in patients with PIDs has been determined. Despite strong support for the physiologic role of tumor immunosurveillance and the increasing success of strategies in immunologic tumor therapy, which include checkpoint inhibition, mAbs, and engineered T-cell antigen receptors, the incidence and pattern of malignancies in patients with PIDs do not reflect an increased tumor immune escape per se. In contrast, malignancies appear to be restricted to either (1) tissue types bearing the same molecular defect that underlies the PID, such as syndromes of DNA repair deficiency or immune cell-specific maturation or functional defects that suggest a cell-intrinsic oncogenic basis, or (2) other tissues when they are infected by transforming viruses or chronically inflamed, pointing toward extrinsic causes for transformation that are potentially facilitated by but not predominantly caused by a lack of immunosurveillance. Based on recent studies of pre-existing conditions in patients with malignancies and on malignancies in large PID cohorts, we conclude that a large part of tumor predisposition in patients with PIDs is derived from the same molecular defect as the immunodeficiency itself. The presented concept elucidates diverse pathomechanisms and risks of malignancies in patients with PIDs in light of current tumor immune therapies.

Intrinsic and extrinsic causes of malignancies in patients with primary immunodeficiency disorders

Epstein-Barr Virus (EBV) is a gamma-herpes virus that infects 90% of humans without any symptoms in most cases, but has an oncogenic potential, especially in immunocompromised individuals. In the past 30 years several primary immunodeficiencies (PIDs) associated with a high risk to develop EBV-associated lymphoproliferative disorders, essentially consisting of virus-associated hemophagocytic syndrome (VAHS), non-malignant and malignant B-cell lymphoproliferative disorders (LPD) including non-Hodgkin and Hodgkin’s types of B lymphomas have been characterized. Among them are SH2D1A (SAP), XIAP, ITK, MAGT1, CD27, CD70, CTPS1, RASGRP1 and CORO1A deficiencies. Penetrance of EBV infection ranges from 50 to 100% in those PIDs. Description of large cohorts and case reports have refined the specific phenotypes associated to these PIDs helping to the diagnosis. Specific pathways required for protective immunity to EBV have emerged from studies of these PIDs. SAP-dependent SLAM receptors and MAGT1-dependent NKG2D pathways are important for T and NK-cell cytotoxicity towards EBV-infected B-cells, while CD27-CD70 interactions are critical to drive the expansion of EBV-specific T-cells. CTPS1 and RASGRP1 deficiencies further strengthen that T-lymphocyte expansion is a key step in the immune response to EBV. These pathways appear to be also important for the anti-tumoral immune surveillance of abnormal B cells. Monogenic PIDs should be thus considered in case of any EBV-associated lymphoproliferative disorders.

Inherited Immunodeficiencies With High Predisposition to Epstein-Barr Virus-Driven Lymphoproliferative Diseases.

Hyper IgE syndromes comprise a group of rare primary immunodeficiency disorders characterized by a triad of atopic dermatitis, recurrent skin and lung infections along with elevated IgE levels. Job syndrome or autosomal dominant hyper IgE syndrome because of heterozygous loss-of-function mutations with dominant negative effect in signal transducer and activator of transcription-3 is the prototype of these disorders. However, several other genetically characterized immunodeficiency disorders have been identified over the past decade and joined the umbrella of hyper IgE syndromes including autosomal recessive mutations in the DOCK8, ZNF431 and PGM3 genes and heterozygous mutations with dominant negative effect in the CARD11 gene. Moreover, a number of phenotypically distinct immunodeficiency disorders can mimic hyper IgE syndromes, adding to the diagnostic challenge. Herein, we will concisely review these disorders, their molecular bases, highlighting key distinguishing clinical and laboratory findings and therapeutic options.

Hyper IgE syndromes: clinical and molecular characteristics

Mutations in DOCK8 result in autosomal recessive Hyper-IgE syndrome with combined immunodeficiency (CID). However, the natural course of disease, long-term prognosis, and optimal therapeutic management have not yet been clearly defined. In an international retrospective survey of patients with DOCK8 mutations, focused on clinical presentation and therapeutic measures, a total of 136 patients with a median follow-up of 11.3 years (1.3-47.7) spanning 1693 patient years, were enrolled. Eczema, recurrent respiratory tract infections, allergies, abscesses, viral infections and mucocutaneous candidiasis were the most frequent clinical manifestations. Overall survival probability in this cohort [censored for hematopoietic stem cell transplantation (HSCT)] was 87 % at 10, 47 % at 20, and 33 % at 30 years of age, respectively. Event free survival was 44, 18 and 4 % at the same time points if events were defined as death, life-threatening infections, malignancy or cerebral complications such as CNS vasculitis or stroke. Malignancy was diagnosed in 23/136 (17 %) patients (11 hematological and 9 epithelial cancers, 5 other malignancies) at a median age of 12 years. Eight of these patients died from cancer. Severe, life-threatening infections were observed in 79/136 (58 %); severe non-infectious cerebral events occurred in 14/136 (10 %). Therapeutic measures included antiviral and antibacterial prophylaxis, immunoglobulin replacement and HSCT. This study provides a comprehensive evaluation of the clinical phenotype of DOCK8 deficiency in the largest cohort reported so far and demonstrates the severity of the disease with relatively poor prognosis. Early HSCT should be strongly considered as a potential curative measure.

Helen Su

Papers

DOCK8 Deficiency: Clinical and Immunological Phenotype and Treatment Options - a Review of 136 Patients