Phenotype, genotype, treatment, and survival outcomes in patients with X-linked inhibitor of apoptosis deficiency.

BACKGROUND: X-linked inhibitor of apoptosis (XIAP) deficiency is a rare primary immunodeficiency disease caused by XIAP gene mutations. A broad range of phenotype, severity, and age at onset present challenges for patient management. OBJECTIVE: We sought to characterize the phenotype, treatment, and survival outcomes of XIAP deficiency and to assess parameters influencing prognosis. METHODS: Data published from 2006 to 2020 were retrospectively analyzed. RESULTS: A total of 167 patients from 117 families with XIAP deficiency were reported with 90 different mutations. A wide spectrum of clinical features were seen, of which hemophagocytic lymphohistiocytosis (HLH) and inflammatory bowel disease were the most common. Patients frequently developed multiple features with no clear genotype-phenotype correlation. A total of 117 patients were managed conservatively and 50 underwent hematopoietic stem-cell transplantation (HSCT), with respective overall survival probabilities of 90% and 53% at age 16 years. The predominant indication for HSCT was early-onset HLH. Active HLH and myeloablative conditioning regimens increased HSCT-related mortality, although HSCT outcome was much better after 2015 than before. For conservatively managed patients reaching adulthood, survival probabilities were 86% at age 30 years and 37% by age 52 years, with worse outcomes for patients developing the disease before the age of 5 years or with new disease features in adulthood. Nine asymptomatic mutation carriers with a median age of 13.5 years were identified. CONCLUSIONS: Our study demonstrates the variable nature of XIAP deficiency, which evolves over life for individual patients. Better therapeutic strategies and prospective studies are required to reduce morbidity and mortality and improve decision making and long-term outcomes for patients with XIAP deficiency.

International retrospective study of allogeneic hematopoietic cell transplantation for activated PI3K-delta syndrome.

BACKGROUND: Activated phosphoinositide 3-kinase delta syndrome (APDS) is a combined immunodeficiency with a heterogeneous phenotype considered reversible by allogeneic hematopoietic cell transplantation (HCT). OBJECTIVES: This study sought to characterize HCT outcomes in APDS. METHODS: Retrospective data were collected on 57 patients with APDS1/2 (median age, 13 years; range, 2-66 years) who underwent HCT. RESULTS: Pre-HCT comorbidities such as lung, gastrointestinal, and liver pathology were common, with hematologic malignancy in 26%. With median follow-up of 2.3 years, 2-year overall and graft failure-free survival probabilities were 86% and 68%, respectively, and did not differ significantly by APDS1 versus APDS2, donor type, or conditioning intensity. The 2-year cumulative incidence of graft failure following first HCT was 17% overall but 42% if mammalian target of rapamycin inhibitor(s) (mTORi) were used in the first year post-HCT, compared with 9% without mTORi. Similarly, 2-year cumulative incidence of unplanned donor cell infusion was overall 28%, but 65% in the context of mTORi receipt and 23% without. Phenotype reversal occurred in 96% of evaluable patients, of whom 17% had mixed chimerism. Vulnerability to renal complications continued post-HCT, adding new insights into potential nonimmunologic roles of phosphoinositide 3-kinase not correctable through HCT. CONCLUSIONS: Graft failure, graft instability, and poor graft function requiring unplanned donor cell infusion were major barriers to successful HCT. Post-HCT mTORi use may confer an advantage to residual host cells, promoting graft instability. Longer-term post-HCT follow-up of more patients is needed to elucidate the kinetics of immune reconstitution and donor chimerism, establish approaches that reduce graft instability, and assess the completeness of phenotype reversal over time.

Human cytomegalovirus haplotype reconstruction reveals high diversity due to superinfection and evidence of within-host recombination.

Recent sequencing efforts have led to estimates of human cytomegalovirus (HCMV) genome-wide intrahost diversity that rival those of persistent RNA viruses [Renzette N, Bhattacharjee B, Jensen JD, Gibson L, Kowalik TF (2011) PLoS Pathog 7:e1001344]. Here, we deep sequence HCMV genomes recovered from single and longitudinally collected blood samples from immunocompromised children to show that the observations of high within-host HCMV nucleotide diversity are explained by the frequent occurrence of mixed infections caused by genetically distant strains. To confirm this finding, we reconstructed within-host viral haplotypes from short-read sequence data. We verify that within-host HCMV nucleotide diversity in unmixed infections is no greater than that of other DNA viruses analyzed by the same sequencing and bioinformatic methods and considerably less than that of human immunodeficiency and hepatitis C viruses. By resolving individual viral haplotypes within patients, we reconstruct the timing, likely origins, and natural history of superinfecting strains. We uncover evidence for within-host recombination between genetically distinct HCMV strains, observing the loss of the parental virus containing the nonrecombinant fragment. The data suggest selection for strains containing the recombinant fragment, generating testable hypotheses about HCMV evolution and pathogenesis. These results highlight that high HCMV diversity present in some samples is caused by coinfection with multiple distinct strains and provide reassurance that within the host diversity for single-strain HCMV infections is no greater than for other herpesviruses.

The extended phenotype of LPS-responsive beige-like anchor protein (LRBA) deficiency.

BACKGROUND: LPS-responsive beige-like anchor protein (LRBA) deficiency is a primary immunodeficiency caused by biallelic mutations in LRBA that abolish LRBA protein expression. OBJECTIVE: We sought to report the extended phenotype of LRBA deficiency in a cohort of 22 LRBA-deficient patients. METHODS: Clinical criteria, protein detection, and genetic sequencing were applied to diagnose LRBA deficiency. RESULTS: Ninety-three patients met the inclusion criteria and were considered to have possible LRBA deficiency. Twenty-four patients did not express LRBA protein and were labeled as having probable LRBA deficiency, whereas 22 were genetically confirmed as having definitive LRBA deficiency, with biallelic mutations in LRBA. Seventeen of these were novel and included homozygous or compound heterozygous mutations. Immune dysregulation (95%), organomegaly (86%), recurrent infections (71%), and hypogammaglobulinemia (57%) were the main clinical complications observed in LRBA-deficient patients. Although 81% of LRBA-deficient patients had normal T-cell counts, 73% had reduced regulatory T (Treg) cell numbers. Most LRBA-deficient patients had low B-cell subset counts, mainly in switched memory B cells (80%) and plasmablasts (92%), with a defective specific antibody response in 67%. Of the 22 patients, 3 are deceased, 2 were treated successfully with hematopoietic stem cell transplantation, 7 are receiving immunoglobulin replacement, and 15 are receiving immunosuppressive treatment with systemic corticosteroids alone or in combination with steroid-sparing agents. CONCLUSION: This report describes the largest cohort of patients with LRBA deficiency and offers guidelines for physicians to identify LRBA deficiency, supporting appropriate clinical management.

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.

Disease-associated missense mutations in the EVH1 domain disrupt intrinsic WASp function causing dysregulated actin dynamics and impaired dendritic cell migration.

Wiskott Aldrich syndrome (WAS), an X-linked immunodeficiency, results from loss-of-function mutations in the human hematopoietic cytoskeletal regulator gene WAS. Many missense mutations in the Ena Vasp homology1 (EVH1) domain preserve low-level WAS protein (WASp) expression and confer a milder clinical phenotype. Although disrupted binding to WASp-interacting protein (WIP) leads to enhanced WASp degradation in vivo, the intrinsic function of EVH1-mutated WASp is poorly understood. In the present study, we show that, despite mediating enhanced actin polymerization compared with wild-type WASp in vitro, EVH1 missense mutated proteins did not support full biologic function in cells, even when levels were restored by forced overexpression. Podosome assembly was aberrant and associated with dysregulated lamellipodia formation and impaired persistence of migration. At sites of residual podosome-associated actin polymerization, localization of EVH1-mutated proteins was preserved even after deletion of the entire domain, implying that WIP-WASp complex formation is not absolutely required for WASp localization. However, retention of mutant proteins in podosomes was significantly impaired and associated with reduced levels of WASp tyrosine phosphorylation. Our results indicate that the EVH1 domain is important not only for WASp stability, but also for intrinsic biologic activity in vivo.

Stem cell transplantation for primary immune deficiency.

PURPOSE OF REVIEW: In this article, we summarize the recent advances in treating primary immune deficiency (PID) disorders by stem cell transplantation (SCT); we have focused on articles published in the past 2 years since the last major review of SCT for PID. RECENT FINDINGS: Analyses of the outcomes of SCT for PID by specific molecular defect have clarified which conditions are receptive to unconditioned transplants and which require more myeloablative conditioning. Improved outcomes for 'difficult' conditions [adenosine deaminase-severe combined immunodeficiency (ADA-SCID), major histocompatibility complex class II deficiency] and potential advantages of using cord blood as a stem cell source have also been described. Newborn screening for SCID identifies well babies with SCID: the optimal SCT protocol for such young infants remains to be determined. Reduced toxicity conditioning has been successfully used to treat conditions such as Wiskott-Aldrich syndrome and chronic granulomatous disease, offering curative engraftment with reduced transplant-related mortality. Similarly, treating children with familial hemophagocytic lymphohistiocytosis using reduced intensity conditioning SCT results in much improved outcomes. Advances in next generation sequencing have identified new diseases amenable to SCT, such as DOCK8 deficiency, resulting in improved quality of life and protection from malignancy. SUMMARY: Recent studies suggest that further improvements in treating PID with SCT are possible with a greater understanding of the genetics and immunobiology of these diseases, facilitating the matching of donor type and conditioning regimens, or indeed alternative therapies (such as gene therapy) to specific PID disorders.

Neuroinflammation, autoinflammation, splenomegaly and anemia caused by bi-allelic mutations in IRAK4.

We describe a novel, severe autoinflammatory syndrome characterized by neuroinflammation, systemic autoinflammation, splenomegaly, and anemia (NASA) caused by bi-allelic mutations in IRAK4. IRAK-4 is a serine/threonine kinase with a pivotal role in innate immune signaling from toll-like receptors and production of pro-inflammatory cytokines. In humans, bi-allelic mutations in IRAK4 result in IRAK-4 deficiency and increased susceptibility to pyogenic bacterial infections, but autoinflammation has never been described. We describe 5 affected patients from 2 unrelated families with compound heterozygous mutations in IRAK4 (c.C877T (p.Q293*)/c.G958T (p.D320Y); and c.A86C (p.Q29P)/c.161 + 1G>A) resulting in severe systemic autoinflammation, massive splenomegaly and severe transfusion dependent anemia and, in 3/5 cases, severe neuroinflammation and seizures. IRAK-4 protein expression was reduced in peripheral blood mononuclear cells (PBMC) in affected patients. Immunological analysis demonstrated elevated serum tumor necrosis factor (TNF), interleukin (IL) 1 beta (IL-1ß), IL-6, IL-8, interferon α2a (IFN-α2a), and interferon ß (IFN-ß); and elevated cerebrospinal fluid (CSF) IL-6 without elevation of CSF IFN-α despite perturbed interferon gene signature. Mutations were located within the death domain (DD; p.Q29P and splice site mutation c.161 + 1G>A) and kinase domain (p.Q293*/p.D320Y) of IRAK-4. Structure-based modeling of the DD mutation p.Q29P showed alteration in the alignment of a loop within the DD with loss of contact distance and hydrogen bond interactions with IRAK-1/2 within the myddosome complex. The kinase domain mutation p.D320Y was predicted to stabilize interactions within the kinase active site. While precise mechanisms of autoinflammation in NASA remain uncertain, we speculate that loss of negative regulation of IRAK-4 and IRAK-1; dysregulation of myddosome assembly and disassembly; or kinase active site instability may drive dysregulated IL-6 and TNF production. Blockade of IL-6 resulted in immediate and complete amelioration of systemic autoinflammation and anemia in all 5 patients treated; however, neuroinflammation has, so far proven recalcitrant to IL-6 blockade and the janus kinase (JAK) inhibitor baricitinib, likely due to lack of central nervous system penetration of both drugs. We therefore highlight that bi-allelic mutation in IRAK4 may be associated with a severe and complex autoinflammatory and neuroinflammatory phenotype that we have called NASA (neuroinflammation, autoinflammation, splenomegaly and anemia), in addition to immunodeficiency in humans.

Omission of in vivo T-cell depletion promotes rapid expansion of naïve CD4+ cord blood lymphocytes and restores adaptive immunity within 2 months after unrelated cord blood transplant.

Umbilical cord blood transplant (UCBT) is associated with impaired early immune reconstitution. This might be explained by a lower T-cell dose infused, the naivety of cord blood T-cells and the use of in vivo T-cell depletion. We studied the pattern of early immune reconstitution and the clinical outcome of children undergoing unrelated UCBT when in vivo T-cell depletion was omitted. Thirty children affected by malignancies (46%) or immunodeficiencies (54%) underwent an unrelated UCBT. Prospective assessment of immune reconstitution and clinical outcome was performed. We observed an unprecedented CD4(+) T-cell reconstitution, with a median cell count at 30 and 60 d post UCBT of 0.3 × 10(9) /l and 0.56 × 10(9) /l, respectively. Early T-cell expansion was thymic-independent, with a rapid shift from naïve to central memory phenotype and early regulatory T-cell recovery. Viral infections were frequent (63%) but resolved rapidly in most cases and virus-specific T-lymphocytes were detected within 2 months post-UCBT. Acute graft-versus-host disease (GvHD) was frequent (grade II = 34%, grade III-IV = 16%) but steroid responsive, and the incidence of chronic GvHD was low (14%). The omission of in vivo T-cell depletion promotes a unique thymic-independent CD4(+) T-cell reconstitution after unrelated UCBT in children. We postulate that this relates to the specific immunological and ontological qualities of fetal-derived lymphocytes.

Detection of Low Frequency Multi-Drug Resistance and Novel Putative Maribavir Resistance in Immunocompromised Pediatric Patients with Cytomegalovirus.

Human cytomegalovirus (HCMV) is a significant pathogen in immunocompromised individuals, with the potential to cause fatal pneumonitis and colitis, as well as increasing the risk of organ rejection in transplant patients. With the advent of new anti-HCMV drugs there is therefore considerable interest in using virus sequence data to monitor emerging resistance to antiviral drugs in HCMV viraemia and disease, including the identification of putative new mutations. We used target-enrichment to deep sequence HCMV DNA from 11 immunosuppressed pediatric patients receiving single or combination anti-HCMV treatment, serially sampled over 1-27 weeks. Changes in consensus sequence and resistance mutations were analyzed for three ORFs targeted by anti-HCMV drugs and the frequencies of drug resistance mutations monitored. Targeted-enriched sequencing of clinical material detected mutations occurring at frequencies of 2%. Seven patients showed no evidence of drug resistance mutations. Four patients developed drug resistance mutations a mean of 16 weeks after starting treatment. In two patients, multiple resistance mutations accumulated at frequencies of 20% or less, including putative maribavir and ganciclovir resistance mutations P522Q (UL54) and C480F (UL97). In one patient, resistance was detected 14 days earlier than by PCR. Phylogenetic analysis suggested recombination or superinfection in one patient. Deep sequencing of HCMV enriched from clinical samples excluded resistance in 7 of 11 subjects and identified resistance mutations earlier than conventional PCR-based resistance testing in 2 patients. Detection of multiple low level resistance mutations was associated with poor outcome.

Current and emerging treatment options for Wiskott-Aldrich syndrome.

Wiskott-Aldrich syndrome is a life-threatening primary immunodeficiency associated with a bleeding tendency, eczema and a high incidence of autoimmunity and malignancy. Stem cell transplantation offers the opportunity of cure for all these complications, and over the past 35 years there has been a remarkable improvement in survival following this treatment. Here, we review advances in management of clinical complications pre- and post-transplant, as well as discuss the morbidity Wiskott-Aldrich syndrome patients experience following treatment. For patients with a poorly matched stem cell donor, recent gene therapy trials demonstrate encouraging results and the potential of low-toxicity therapy for all patients.