Advanced computational analysis of CD40LG variants in atypical X-linked hyper-IgM syndrome.

X-Linked Hyper-IgM Syndrome is caused by pathogenic variants in CD40LG. Three patients with atypical clinical and immunological features were identified with variants in CD40LG requiring further characterization. Flow cytometry was used to evaluate CD40L protein expression and binding capacity to a surrogate receptor, CD40-muIg. Though functional anomalies were observed, there was still a lack of clarity regarding the underlying mechanism. We developed structural models for wild-type and the three variants of CD40L protein observed in these patients (p. Lys143Asn, Leu225Ser and Met36Arg) to evaluate structural alterations by molecular mechanic calculations, and assess protein movement by molecular dynamic simulations. These studies demonstrate that functional analysis of variants of unknown significance in CD40LG can be supplemented by advanced computational analysis in atypical clinical contexts. These studies in combination identify the deleterious effects of these variants and potential mechanisms for protein dysfunction.

Disease Progression of WHIM Syndrome in an International Cohort of 66 Pediatric and Adult Patients.

Warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome (WS) is a combined immunodeficiency caused by gain-of-function mutations in the C-X-C chemokine receptor type 4 (CXCR4) gene. We characterize a unique international cohort of 66 patients, including 57 (86%) cases previously unreported, with variable clinical phenotypes. Of 17 distinct CXCR4 genetic variants within our cohort, 11 were novel pathogenic variants affecting 15 individuals (23%). All variants affect the same CXCR4 region and impair CXCR4 internalization resulting in hyperactive signaling. The median age of diagnosis in our cohort (5.5 years) indicates WHIM syndrome can commonly present in childhood, although some patients are not diagnosed until adulthood. The prevalence and mean age of recognition and/or onset of clinical manifestations within our cohort were infections 88%/1.6 years, neutropenia 98%/3.8 years, lymphopenia 88%/5.0 years, and warts 40%/12.1 years. However, we report greater prevalence and variety of autoimmune complications of WHIM syndrome (21.2%) than reported previously. Patients with versus without family history of WHIM syndrome were diagnosed earlier (22%, average age 1.3 years versus 78%, average age 5 years, respectively). Patients with a family history of WHIM syndrome also received earlier treatment, experienced less hospitalization, and had less end-organ damage. This observation reinforces previous reports that early treatment for WHIM syndrome improves outcomes. Only one patient died; death was attributed to complications of hematopoietic stem cell transplantation. The variable expressivity of WHIM syndrome in pediatric patients delays their diagnosis and therapy. Early-onset bacterial infections with severe neutropenia and/or lymphopenia should prompt genetic testing for WHIM syndrome, even in the absence of warts.

Hematopoietic Stem Cell Transplantation in ARPC1B Deficiency.

Mutations in the ARPC1B isoform component of human actin-related protein 2/3 complex have been recently associated with an inborn error of immunity characterized by combined immunodeficiency, allergies, autoinflammation, and platelet abnormalities. Currently, indications on the management of this novel disease and information on its outcome are lacking. We report the first case series of 7 children with a homozygous mutation in ARPC1B gene who underwent allogeneic-HSCT (allo-HSCT). All patients presented an early clinical onset, characterized by recurrent infections, failure to thrive and gastrointestinal bleeding episodes complicated with neonatal hemorrhagic enteritis in 3 cases, and macrophage activating syndrome in 2. Allo-HSCT was performed at the median age of 1.83 years after a myeloablative conditioning regimen in all cases. Engraftment occurred in all patients with full donor chimerism in 6 out of 7. The clinical course after engraftment was uneventful in 3 out of 7 children; 2 patients developed a grade 1-2 acute graft-versus-host disease (GvHD), and 1 patient a grade 1 chronic-GvHD. JC virus-related progressive multifocal leukoencephalopathy was diagnosed in one patient 13 months after haploidentical-HSCT and successfully managed with donor-derived viral-specific T-cell infusion. Only one patient had a fatal outcome 3 months after HSCT because of sepsis, after veno-occlusive disease, and transplant-associated microangiopathy. At a median follow-up of 19 months (range 3-110), 6 out of 7 patients are alive and disease-free. The severity of the clinical phenotype at diagnosis and the high survival rate, with limited transplant-related morbidity, strongly support the indication to allo-HSCT for patients with this diagnosis.

Improvement of SLC29A3 spectrum disorder-related sensorineural hearing loss after initiation of IL-6 inhibitor.

Tocilizumab is reported to reduce systemic inflammation in individuals with SLC29A3 spectrum disorder, but its effect on hearing loss has not been described. The authors present a boy toddler with a history of prematurity, dysphagia, hypersplenism, hyperpigmentation, short height and hearing loss who was referred to the immunology clinic. He initially presented shortly after birth with abnormal hearing screens followed by positive urine test for cytomegalovirus. However, the infection was determined to be postnatally acquired and hearing loss most likely from genetic causes given a family history of hearing loss and consanguinity. A pathogenic variant in SLC29A3 was found on whole-exome sequencing and given concern for SLC29A3 spectrum disorder, steroids were started. Following concerns for development of side effects with chronic steroid use, he was switched to interleukin 6 inhibitor therapy. The patient's inflammatory markers decreased on tocilizumab, and his sensorineural hearing loss was notable for improvement and stabilisation on therapy.

Neuroinflammatory Disease as an Isolated Manifestation of Hemophagocytic Lymphohistiocytosis.

Isolated neuroinflammatory disease has been described in case reports of familial hemophagocytic lymphohistiocytosis (FHL), but the clinical spectrum of disease manifestations, response to therapy and prognosis remain poorly defined. We combined an international survey with a literature search to identify FHL patients with (i) initial presentation with isolated neurological symptoms; (ii) absence of cytopenia and splenomegaly at presentation; and (iii) systemic HLH features no earlier than 3 months after neurological presentation. Thirty-eight (20 unreported) patients were identified with initial diagnoses including acute demyelinating encephalopathy, leukoencephalopathy, CNS vasculitis, multiple sclerosis, and encephalitis. Median age at presentation was 6.5 years, most commonly with ataxia/gait disturbance (75%) and seizures (53%). Diffuse multifocal white matter changes (79%) and cerebellar involvement (61%) were common MRI findings. CSF cell count and protein were increased in 22/29 and 15/29 patients, respectively. Fourteen patients progressed to systemic inflammatory disease fulfilling HLH-2004 criteria at a mean of 36.9 months after initial neurological presentation. Mutations were detected in PRF1 in 23 patients (61%), RAB27A in 10 (26%), UNC13D in 3 (8%), LYST in 1 (3%), and STXBP2 in 1 (3%) with a mean interval to diagnosis of 28.3 months. Among 19 patients who underwent HSCT, 11 neurologically improved, 4 were stable, one relapsed, and 3 died. Among 14 non-transplanted patients, only 3 improved or had stable disease, one relapsed, and 10 died. Isolated CNS-HLH is a rare and often overlooked cause of inflammatory brain disease. HLH-directed therapy followed by HSCT seems to improve survival and outcome.

Neutrophil Extracellular Traps in Tissue and Periphery in Juvenile Dermatomyositis.

OBJECTIVE: Neutrophils are key immune cells participating in host defense through several mechanisms, including the formation of neutrophil extracellular traps (NETs). This study was undertaken to investigate the role of neutrophils in juvenile dermatomyositis (JDM). METHODS: Electron microscopy was used to identify neutrophils in tissue. NETs were also imaged using fluorescence microscopy and quantified using a myeloperoxidase-DNA enzyme-linked immunosorbent assay (ELISA) in plasma obtained from healthy children (n = 20), disease controls (n = 29), JDM patients (n = 66), and JDM patients with history of calcifications (n = 20). Clinical data included disease activity scores and complement C4 levels. Levels of immune complexes (ICs) and calprotectin were analyzed using ELISA. RESULTS: Using electron microscopy, neutrophils were found to infiltrate affected muscle tissue, engulfing deposited calcium crystals. Uptake of the crystals led to neutrophil activation (P < 0.01) and subsequent phosphatidylinositol 3-kinase- and NADPH oxidase-dependent but peptidylarginine deiminase 4-independent formation of NETs, which contained mitochondrial DNA (P < 0.05), as confirmed in vivo (P < 0.001) and in vitro (P < 0.01). Peripheral NET levels were associated with calcinosis (P = 0.01), ICs (P = 0.008), and interleukin-8 levels (P = 0.004). Children with JDM had impaired NET clearance (P = 0.01), associated with autoantibody profiles including melanoma differentiation-associated protein 5 (P = 0.005), and depressed complement C4 levels (r = -0.72, P = 0.002). Furthermore, children with JDM showed evidence of neutrophil activation, with elevated levels of peroxidase activity (P = 0.02) and calprotectin (P < 0.01), which were associated with disease activity (P = 0.007), and dyslipidemia (odds ratio 4.7, P < 0.05). CONCLUSION: We found novel mechanisms of both calcium crystal-mediated neutrophil activation and cell death in JDM pathophysiology. Targeting this pathway may reduce the frequency and extent of calcinosis, as well as prevent long-term development of comorbidities, including atherosclerosis.

Long-term outcome of LRBA deficiency in 76 patients after various treatment modalities as evaluated by the immune deficiency and dysregulation activity (IDDA) score.

BACKGROUND: Recent findings strongly support hematopoietic stem cell transplantation (HSCT) in patients with severe presentation of LPS-responsive beige-like anchor protein (LRBA) deficiency, but long-term follow-up and survival data beyond previous patient reports or meta-reviews are scarce for those patients who do not receive a transplant. OBJECTIVE: This international retrospective study was conducted to elucidate the longitudinal clinical course of patients with LRBA deficiency who do and do not receive a transplant. METHOD: We assessed disease burden and treatment responses with a specially developed immune deficiency and dysregulation activity score, reflecting the sum and severity of organ involvement and infections, days of hospitalization, supportive care requirements, and performance indices. RESULTS: Of 76 patients with LRBA deficiency from 29 centers (median follow-up, 10 years; range, 1-52), 24 underwent HSCT from 2005 to 2019. The overall survival rate after HSCT (median follow-up, 20 months) was 70.8% (17 of 24 patients); all deaths were due to nonspecific, early, transplant-related mortality. Currently, 82.7% of patients who did not receive a transplant (43 of 52; age range, 3-69 years) are alive. Of 17 HSCT survivors, 7 are in complete remission and 5 are in good partial remission without treatment (together, 12 of 17 [70.6%]). In contrast, only 5 of 43 patients who did not receive a transplant (11.6%) are without immunosuppression. Immune deficiency and dysregulation activity scores were significantly lower in patients who survived HSCT than in those receiving conventional treatment (P = .005) or in patients who received abatacept or sirolimus as compared with other therapies, and in patients with residual LRBA expression. Higher disease burden, longer duration before HSCT, and lung involvement were associated with poor outcome. CONCLUSION: The lifelong disease activity, implying a need for immunosuppression and risk of malignancy, must be weighed against the risks of HSCT.

Evidence for Resident Memory T cells in Rasmussen Encephalitis.

Investigators from University of California Los Angeles studied the presence of different T cell subset population in the brain tissue of 7 patients with Rasmussen encephalitis, a rare neuroinflammatory disorder characterized by intractable seizures and usually associated with progressive hemi cerebral atrophy, who underwent brain surgery and compared them to patients with focal cortical dysplasia.