Wiskott-Aldrich Syndrome: A study on 577 patients defining the genotype as a predictive biomarker for disease severity

WAS is a multifaceted monogenic disorder with a broad disease spectrum and variable disease severity and a variety of treatment options including allogeneic hematopoietic stem cell transplantation (HSCT) and gene therapy (GT). No reliable biomarker exists to predict disease course and outcome for individual patients. A total of 577 patients with a WAS variant from 26 countries and a median follow-up of 8.9 years (0.3-71.1), totaling 6118 patient-years, were included in this international retrospective study. Overall survival (OS) of the cohort (censored at HSCT or GT) was 82% (95% CI 78-87) at 15 years and 70% (61-80) at 30 years of age. The type of variant was predictive of outcome: patients with a missense variant in exons 1 or 2 or with the intronic hotspot variant c.559+5G>A (class I variants) had a 15-year OS of 93% (89-98) and a 30-year OS of 91% (86-97), compared to 71% (62-81) and 48% (34-68) in patients with any other variant (class II; p<0.0001). The cumulative incidence rates of disease-related complications such as severe bleeding (p=0.007), life-threatening infection (p<0.0001), and autoimmunity (p=0.004) occurred significantly later in patients with a class I variant. The cumulative incidence of malignancy (p=0.6) was not different between classes I and II. This study represents the largest cohort of WAS patients studied so far. It confirms the spectrum of disease severity and quantifies the risk for specific disease-related complications. The class of variant is a biomarker to predict the outcome for WAS patients.

Simple Measurement of IgA Predicts Immunity and Mortality in Ataxia-Telangiectasia

Patients with ataxia-telangiectasia (A-T) suffer from progressive cerebellar ataxia, immunodeficiency, respiratory failure, and cancer susceptibility. From a clinical point of view, A-T patients with IgA deficiency show more symptoms and may have a poorer prognosis. In this study, we analyzed mortality and immunity data of 659 A-T patients with regard to IgA deficiency collected from the European Society for Immunodeficiencies (ESID) registry and from 66 patients with classical A-T who attended at the Frankfurt Goethe-University between 2012 and 2018. We studied peripheral B- and T-cell subsets and T-cell repertoire of the Frankfurt cohort and survival rates of all A-T patients in the ESID registry. Patients with A-T have significant alterations in their lymphocyte phenotypes. All subsets (CD3, CD4, CD8, CD19, CD4/CD45RA, and CD8/CD45RA) were significantly diminished compared to standard values. Patients with IgA deficiency (n = 35) had significantly lower lymphocyte counts compared to A-T patients without IgA deficiency (n = 31) due to a further decrease of naïve CD4 T-cells, central memory CD4 cells, and regulatory T-cells. Although both patient groups showed affected TCR-ß repertoires compared to controls, no differences could be detected between patients with and without IgA deficiency. Overall survival of patients with IgA deficiency was significantly diminished. For the first time, our data show that patients with IgA deficiency have significantly lower lymphocyte counts and subsets, which are accompanied with reduced survival, compared to A-T patients without IgA deficiency. IgA, a simple surrogate marker, is indicating the poorest prognosis for classical A-T patients. Both non-interventional clinical trials were registered at clinicaltrials.gov 2012 (Susceptibility to infections in ataxia-telangiectasia; NCT02345135) and 2017 (Susceptibility to Infections, tumor risk and liver disease in patients with ataxia-telangiectasia; NCT03357978)

Current clinical practice and challenges in the management of secondary immunodeficiency in hematological malignancies

Objective

Despite long‐standing safe and effective use of immunoglobulin replacement therapy (IgRT) in primary immunodeficiency, clinical data on IgRT in patients with secondary immunodeficiency (SID) due to B‐cell lymphoproliferative diseases are limited. Here, we examine the correlation between approved IgRT indications, treatment recommendations, and clinical practice in SID.

Methods

An international online survey of 230 physicians responsible for the diagnosis of SID and the prescription of IgRT in patients with hematological malignancies was conducted.

Results

Serum immunoglobulin was measured in 83% of patients with multiple myeloma, 76% with chronic lymphocytic leukemia, and 69% with non‐Hodgkin lymphoma. Most physicians (85%) prescribed IgRT after ≥2 severe infections. In Italy, Germany, Spain, and the United States, immunoglobulin use was above average in patients with hypogammaglobulinemia, while in the UK considerably fewer patients received IgRT. The use of subcutaneous immunoglobulin was highest in France (34%) and lowest in Spain (19%). Immunologists measured specific antibody responses, performed test immunization, implemented IgRT, and used subcutaneous immunoglobulin more frequently than physicians overall.

Conclusions

The management of SID in hematological malignancies varied regionally. Clinical practice did not reflect treatment guidelines, highlighting the need for robust clinical studies on IgRT in this population and harmonization between countries and disciplines.

Antigenic mimicry of ubiquitin by the gut bacterium Bacteroides fragilis: a potential link with autoimmune disease

Ubiquitin is highly conserved across eukaryotes and is essential for normal eukaryotic cell function. The bacterium Bacteroides fragilis is a member of the normal human gut microbiota, and the only bacterium known to encode a homologue of eukaryotic ubiquitin. The B. fragilis gene sequence indicates a past horizontal gene transfer event from a eukaryotic source. It encodes a protein (BfUbb) with 63% identity to human ubiquitin which is exported from the bacterial cell. The aim of this study was (i) to determine if there was antigenic cross‐reactivity between B. fragilis ubiquitin and human ubiquitin and (ii) to determine if humans produced antibodies to BfUbb. Molecular model comparisons of BfUbb and human ubiquitin predicted a high level (99·8% confidence) of structural similarity. Linear epitope mapping identified epitopes in BfUbb and human ubiquitin that cross‐react. BfUbb also has epitope(s) that do not cross‐react with human ubiquitin. The reaction of human serum (n = 474) to BfUbb and human ubiquitin from the following four groups of subjects was compared by enzyme‐linked immunosorbent assay (ELISA): (1) newly autoantibody‐positive patients, (2) allergen‐specific immunoglobulin (Ig)E‐negative patients, (3) ulcerative colitis patients and (4) healthy volunteers. We show that the immune system of some individuals has been exposed to BfUbb which has resulted in the generation of IgG antibodies. Serum from patients referred for first‐time testing to an immunology laboratory for autoimmune disease are more likely to have a high level of antibodies to BfUbb than healthy volunteers. Molecular mimicry of human ubiquitin by BfUbb could be a trigger for autoimmune disease.

T cell immunodeficiency

T cell immunodeficiency can occur as one of a group of primary disorders or develop secondary to chronic infection, illness or drug therapy. Primary T cell disorders are rare, accounting for approximately 11% of reported primary immunodeficiencies, and generally present in infancy or early childhood. Early recognition is very important as many of these patients will require bone marrow transplantation prior to the onset of severe infection or other complications. Because of their rarity, these infants usually present to clinicians who have little or no prior experience of these conditions, and therefore laboratory-based clinicians with knowledge of the key laboratory/pathological abnormalities and clinical features have a valuable role in identifying the possibility of immunodeficiency. Secondary T cell deficiency is a cardinal feature of HIV infection and the specific susceptibility to infectious micro-organisms is highlighted. The possibility of T cell immunodeficiency should be considered in any patient presenting with unusual or severe viral, fungal or protozoal infection.

A novel treatment in X-linked agammaglobulinaemia - hyperbaric oxygen therapy in refractory chronic wounds

Chronic wounds are a rare complication of X-linked agammaglobulinaemia (XLA). Fastidious organisms such as helicobacter bills have been reported in XLA with chronic wounds but sterile chronic wounds also occur. Hyperbaric Oxygen Therapy has been used in chronic wounds but has not previously been reported in primary antibody deficiencies. We present a case of a chronic wound in a patient with XLA refractory to antimicrobial therapy that made a remarkable recovery following Hyperbaric Oxygen Therapy.

A new functional assay for the diagnosis of X-linked inhibitor of apoptosis (XIAP) deficiency

X-linked inhibitor of apoptosis (XIAP) deficiency, caused by mutations in BIRC4, is an immunodeficiency associated with immune dysregulation and a highly variable clinical presentation. Current diagnostic screening tests such as flow cytometry for XIAP expression or lymphocyte apoptosis assays have significant limitations. Based on recent evidence that XIAP is essential for nucleotide-binding and oligomerization domains (NOD)1/2 signalling, we evaluated the use of a simple flow cytometric assay assessing tumour necrosis factor (TNF) production of monocytes in response to NOD2 stimulation by muramyl dipeptides (L18-MDP) for the functional diagnosis of XIAP deficiency. We investigated 12 patients with XIAP deficiency, six female carriers and relevant disease controls. Irrespective of the diverse clinical phenotype, the extent of residual protein expression or the nature of the mutation, the TNF response was severely reduced in all patients. On average, L18-MDP induced TNF production in 25% of monocytes from healthy donors or female carriers, while fewer than 6% of monocytes responded in affected patients. Notably, the assay clearly discriminated affected patients from disease controls with other immunodeficiencies accompanied by lymphoproliferation, hypogammaglobulinaemia or inflammatory bowel disease. Functional testing of the NOD2 signalling pathway is an easy, fast and reliable assay in the diagnostic evaluation of patients with suspected XIAP deficiency.

The United Kingdom Primary Immune Deficiency (UKPID) Registry: report of the first 4 years' activity 2008-2012

This report summarizes the establishment of the first national online registry of primary immune deficency in the United Kingdom, the United Kingdom Primary Immunodeficiency (UKPID Registry). This UKPID Registry is based on the European Society for Immune Deficiency (ESID) registry platform, hosted on servers at the Royal Free site of University College, London. It is accessible to users through the website of the United Kingdom Primary Immunodeficiency Network (www.ukpin.org.uk). Twenty-seven centres in the United Kingdom are actively contributing data, with an additional nine centres completing their ethical and governance approvals to participate. This indicates that 36 of 38 (95%) of recognized centres in the United Kingdom have engaged with this project. To date, 2229 patients have been enrolled, with a notable increasing rate of recruitment in the past 12 months. Data are presented on the range of diagnoses recorded, estimated minimum disease prevalence, geographical distribution of patients across the United Kingdom, age at presentation, diagnostic delay, treatment modalities used and evidence of their monitoring and effectiveness.

Eczema and X-linked agammaglobulinaemia

An 8-year-old boy presented with eczematous skin lesions, recurrent otitis media and unexplained pyrexias. X-linked agammaglobulinaemia was diagnosed and treatment commenced with intravenous immunoglobulin replacement therapy. X-linked agammaglobulinaemia (XLA) is a primary immunodeficiency syndrome associated with a deficiency of B lymphocytes, caused by a defect in the expression of Bruton's tyrosine kinase. It affects only boys and usually presents before the age of 2 years with recurrent bacterial sinopulmonary infections. IgG levels are usually <2 g/L (normal range 5.4-16.1) and IgM and IgA are usually undetectable. The commonest cutaneous features of XLA are pyogenic skin infections; however, eczema can occur with increased frequency. We report a child who presented with multiple discrete eczematous lesions who subsequently developed eczematous exacerbations several days after administration of intravenous immunoglobulin (IVIg) replacement therapy.

Inactivation of the Fas gene by Alu insertion: retrotransposition in an intron causing splicing variation and autoimmune lymphoproliferative syndrome

Mutations in the Fas (apo-1, CD95) gene result in autoimmune lymphoproliferative syndrome (ALPS). These mutations are dominated by small deletions and point mutations that result in splicing errors or missense changes. We report here a novel mutation caused by retrotransposon insertion, which results in loss of exon 8 and ALPS. A father and son suffering from recurrent lymphadenopathy were examined for resistance to Fas-mediated apoptosis. A functional defect was detected and RT-PCR analysis revealed two different copies of Fas mRNA, one normal and a second shorter version lacking exon 8. DNA analysis of the genomic region between exons seven and nine in the longer copy revealed two PCR products, one being 331 base pairs (bp) longer than expected. Sequencing revealed that intron 7 had undergone an insertion event with an Alu element (99.31% homology with Alu-Sb1) of 331 bp. This element included a 34-bp Poly A tract that was flanked on each side by a perfect 17 bp direct duplication of the target site. Both patients were heterozygous for the mutated allele that produced Fas mRNA lacking exon 8, although not due to loss of a splice junction. The structure of the insertion suggests that the Alu element may have integrated by retrotransposition, and represents the first report of a retrotransposon causing ALPS.