Omenn Syndrome in Two Infants with Different Hypomorphic Variants in Janus Kinase 3

Biallelic null or hypomorphic variants in JAK3 cause SCID and less frequently Omenn syndrome. We investigated homozygous hypomorphic JAK3 mutations in two patients, and expression and function of a novel JAK3R431P variant in Omenn syndrome. Immunophenotyping of PBMC from the patient with the novel JAK3R431P variant was undertaken, by flow cytometry and Phosflow after stimulation with IL-2, IL-7, and IL-15. JAK3 expression was investigated by Western blotting. We report two patients with homozygous hypomorphic JAK3 variants and clinical features of Omenn syndrome. One patient had a previously described JAK3R775H variant, and the second had a novel JAK3R431P variant. One patient with a novel JAK3R431P variant had normal expression of JAK3 in immortalised EBV-LCL cells but reduced phosphorylation of STAT5 after stimulation with IL-2, IL-7, and IL-15 consistent with impaired kinase activity. These results suggest the JAK3R431P variant to be hypomorphic. Both patients are alive and well after allogeneic haematopoietic stem cell transplantation. They have full donor chimerism, restitution of thymopoiesis and development of appropriate antibody responses following vaccination. We expand the phenotype of hypomorphic JAK3 deficiency and demonstrate the importance of functional testing of novel variants in disease-causing genes.

Outcome of Second Allogeneic HSCT for Patients with Inborn Errors of Immunity: Retrospective Study of 20 Years' Experience

A significant complication of HSCT is graft failure, although few studies focus on this problem in patients with inborn errors of immunity (IE). We explored outcome of second HSCT for IEI by a retrospective, single-centre study between 2002 and 2022. Four hundred ninety-three patients underwent allogeneic HSCT for severe combined immunodeficiency (SCID; n = 113, 22.9%) or non-SCID IEI (n = 380, 77.1%). Thirty patients (6.0%) required second HSCT. Unconditioned infusion or no serotherapy at first HSCT was more common in patients who required second transplant. Median interval between first and second HSCT was 0.97 years (range: 0.19-8.60 years); a different donor was selected for second HSCT in 24/30 (80.0%) patients. Conditioning regimens for second HSCT were predominately treosulfan-based (with thiotepa: n = 18, 60.0%; without, n = 6, 20.0%). Patients received grafts from peripheral blood stem cell (n = 25, 83.3%) or bone marrow (n = 5, 16.7%) with median stem cell dose 9.5 × 106 CD34 + cells/kilogram (range: 1.4-32.3). Median follow-up was 1.92 years (0.22-16.0). Overall survival was 80.8% and event-free survival was 64.7%. Four patients died, two of early-transplant related complications, and two of late sepsis post-second HSCT. Three patients required third HSCT; all are alive with 100% donor chimerism. Cumulative incidence of acute graft-versus-host disease was 28.4%, (all grade I-II). Viral reactivation was seen in 13/30 (43.3%) patients, including HHV6 (n = 6), CMV (n = 4), and adenovirus (n = 2). At latest follow-up, 25/26 surviving patients have donor chimerism ≥ 90% and 16/25 (64.0%) have discontinued immunoglobulin replacement. Second HSCT offers IEI patients with graft failure curative treatment with good overall survival and immunological recovery.

Allogeneic HSCT for Symptomatic Female X-linked Chronic Granulomatous Disease Carriers

X-linked chronic granulomatous disease (XL-CGD) is an inherited disorder of superoxide production, causing failure to generate the oxidative burst in phagocytes. It is characterized by invasive bacterial and fungal infections, inflammation, and chronic autoimmune disease. While XL-CGD carriers were previously assumed to be healthy, a range of clinical manifestations with significant morbidity have recently been described in a subgroup of carriers with impaired neutrophil oxidative burst due to skewed lyonization. Allogeneic hematopoietic stem cell transplantation (HSCT) is the standard curative treatment for CGD but has rarely been reported in individual symptomatic carriers to date. We undertook a retrospective international survey of outcome of HSCT for symptomatic XL-CGD carriers. Seven symptomatic female XL-CGD carriers aged 1-56 years underwent HSCT in four centers, indicated for severe and recurrent infection, colitis, and autoimmunity. Two patients died from transplant-related complications, following donor engraftment and restoration of oxidative burst. All surviving patients demonstrated resolution of their neutrophil oxidative burst defect with concordant reduction in infection and inflammatory symptoms and freedom from further immunosuppressive therapy. In conclusion, allogeneic HSCT may cure the phagocyte defect in symptomatic XL-CGD carriers and improve their recurrent and disabling infective and inflammatory symptoms but risks transplant-related complications.

Too much of a good thing: a review of primary immune regulatory disorders

Primary immune regulatory disorders (PIRDs) are inborn errors of immunity caused by a loss in the regulatory mechanism of the inflammatory or immune response, leading to impaired immunological tolerance or an exuberant inflammatory response to various stimuli due to loss or gain of function mutations. Whilst PIRDs may feature susceptibility to recurrent, severe, or opportunistic infection in their phenotype, this group of syndromes has broadened the spectrum of disease caused by defects in immunity-related genes to include autoimmunity, autoinflammation, lymphoproliferation, malignancy, and allergy; increasing focus on PIRDs has thus redefined the classical 'primary immunodeficiency' as one aspect of an overarching group of inborn errors of immunity. The growing number of genetic defects associated with PIRDs has expanded our understanding of immune tolerance mechanisms and prompted identification of molecular targets for therapy. However, PIRDs remain difficult to recognize due to incomplete penetrance of their diverse phenotype, which may cross organ systems and present to multiple clinical specialists prior to review by an immunologist. Control of immune dysregulation with immunosuppressive therapies must be balanced against the enhanced infective risk posed by the underlying defect and accumulated end-organ damage, posing a challenge to clinicians. Whilst allogeneic hematopoietic stem cell transplantation may correct the underlying immune defect, identification of appropriate patients and timing of transplant is difficult. The relatively recent description of many PIRDs and rarity of individual genetic entities that comprise this group means data on natural history, clinical progression, and treatment are limited, and so international collaboration will be needed to better delineate phenotypes and the impact of existing and potential therapies. This review explores pathophysiology, clinical features, current therapeutic strategies for PIRDs including cellular platforms, and future directions for research.

Recurrent group B stretococcus infection in an extremely premature infant: as a preterm neonate, infant and toddler

We report five discrete episodes of group B streptococcus (GBS) bacteraemia in an extremely premature infant, extending into early childhood. The first four episodes occurred during infancy despite appropriate treatment. Breastmilk was positive for group B streptococcal 16S DNA by polymerase chain reaction. The fifth episode occurred at 17 months of age, shortly after stopping antimicrobial prophylaxis.Radiological investigations did not identify a focus for recurrence of GBS bacteraemia, and immunological investigations and targeted whole genome sequencing yielded only transient hypogammaglobulinaemia of infancy, which resolved.This case highlights invasive GBS infection as a cause of infant morbidity. Premature infants are at particular risk of invasive as well as recurrent disease. GBS is typically a sensitive organism and each episode of GBS in our patient was effectively treated with penicillin. The role of breastmilk in recurrent GBS is controversial; in this case infant and mother isolated identical GBS serotypes and were concurrently treated with rifampicin.

BCG lymphadenitis: a potential complication of immune reconstitution following haematopoietic stem cell transplant

An MHC class II deficient 2-year-old boy presented with fever and an enlarging left neck mass 100 days post allogeneic haematopoietic stem cell transplant (HSCT). Fever persisted despite treatment with broad-spectrum β-lactam antibiotics. His BCG vaccination site at presentation was quiescent. Ultrasound showed enlarged cervical lymph nodes. An incisional biopsy of the large nodal mass yielded acid-fast bacilli, identified as Mycobacterium bovis by genome sequencing. Treatment with rifampicin, isoniazid and pyridoxine was started. The mass suppurated (figure 1), before healing concurrently with T-lymphocyte reconstitution at approximately day 130 post-HSCT.

TCRαβ-Depleted Haploidentical Grafts Are a Safe Alternative to HLA-Matched Unrelated Donor Stem Cell Transplants for Infants with Severe Combined Immunodeficiency

Hematopoietic stem cell transplantation and gene therapy are the only curative therapies for severe combined immunodeficiency (SCID). In patients lacking a matched donor, TCRαβ/CD19-depleted haploidentical family donor transplant (TCRαβ-HaploSCT) is a promising strategy. Conditioned transplant in SCID correlates to better myeloid chimerism and reduced immunoglobulin dependency. We studied transplant outcome in SCID infants according to donor type, specifically TCRαβ-HaploSCT, and conditioning, through retrospective cohort analysis of 52 consecutive infants with SCID transplanted between 2013 and 2020. Median age at transplant was 5.1 months (range, 0.8-16.6). Donors were TCRαβ-HaploSCT (n = 16, 31.4%), matched family donor (MFD, n = 15, 29.4%), matched unrelated donor (MUD, n = 9, 17.6%), and matched unrelated cord blood (CB, n = 11, 21.6%). Forty-one (80%) received fludarabine/treosulfan-based conditioning, 3 (6%) had alemtuzumab only, and 7 (14%) received unconditioned infusions. For conditioned transplants (n = 41), 3-year overall survival was 91% (95% confidence interval, 52-99%) for TCRαβ-HaploSCT, 80% (41-98%) for MFD, 87% (36-98%) for MUD, and 89% (43-98%) for CB (p = 0.89). Cumulative incidence of grade II-IV acute graft-versus-host disease was 11% (2-79%) after TCRαβ-HaploSCT, 0 after MFD, 29% (7-100%) after MUD, and 11% (2-79%) after CB (p = 0.10). 9/10 patients who received alemtuzumab-only or unconditioned transplants survived. Myeloid chimerism was higher following conditioning (median 47%, range 0-100%) versus unconditioned transplant (median 3%, 0-9%) (p < 0.001), as was the proportion of immunoglobulin-free long-term survivors (n = 29/36, 81% vs n = 4/9, 54%) (p < 0.001). TCRαβ-HaploSCT has comparable outcome to MUD and is a promising alternative donor strategy for infants with SCID lacking MFD. This study confirms that conditioned transplant offers better myeloid chimerism and immunoglobulin freedom in long-term survivors.

HSCT in two brothers with CGD arising from mutations in CYBC1 corrects the defect in neutrophil function

Homozygous mutations in cytochrome b-245 chaperone 1 (CYBC1) have been recently described as causing recurrent infections and inflammatory disease in an Icelandic cohort and a patient from Saudi Arabia, by destabilising the dimerisation of gp91^phox with p22^phox, manifesting as phenotypic chronic granulomatous disease (CGD). Haematopoietic stem cell transplantation is the treatment of choice in CGD, though experience of transplantation in this subtype of CGD is limited to a brief description in one patient. We provide clinical and transplant data for two Icelandic brothers with CGD due to homozygous p.Tyr2Ter mutations in CYBC1, demonstrating maintained cure of the immune defect 11 years post-transplant in one brother, and death in the peri-transplant period for the other.

Stem cell transplantation as treatment for major histocompatibility class I deficiency

Major histocompatibility class I deficiency, due to genetic lesions in TAP1, TAP2, TAPBP, or B2M, manifests with recurrent sinopulmonary infections and granulomatous skin ulceration, and is predominately treated with antimicrobial prophylaxis and chest physiotherapy. One previous report of hematopoietic stem cell transplantation has been described in the literature, demonstrating cure of the immune defect without significant graft-versus-host disease. In this report, we expand the literature on HSCT in MHC-I deficiency with follow-up of the original patient, demonstrating maintained resolution of normal immune function and regression of the granulomatous rash 15 years post-transplant, and describe a further patient with mycobacterial disease whose transplant course was complicated by severe graft-versus-host disease.

STAT3 Hyper-IgE Syndrome-an Update and Unanswered Questions

The hyper-IgE syndromes (HIES) are a heterogeneous group of inborn errors of immunity sharing manifestations including increased infection susceptibility, eczema, and raised serum IgE. Since the prototypical HIES description 55 years ago, areas of significant progress have included description of key disease-causing genes and differentiation into clinically distinct entities. The first two patients reported had what is now understood to be HIES from dominant-negative mutations in signal transduction and activator of transcription 3 (STAT3-HIES), conferring a broad immune defect across both innate and acquired arms, as well as defects in skeletal, connective tissue, and vascular function, causing a clinical phenotype including eczema, staphylococcal and fungal skin and pulmonary infection, scoliosis and minimal trauma fractures, and vascular tortuosity and aneurysm. Due to the constitutionally expressed nature of STAT3, initial reports at treatment with allogeneic stem cell transplantation were not positive and treatment has hinged on aggressive antimicrobial prophylaxis and treatment to prevent the development of end-organ disease such as pneumatocele. Research into the pathophysiology of STAT3-HIES has driven understanding of the interface of several signaling pathways, including the JAK-STAT pathways, interleukins 6 and 17, and the role of Th17 lymphocytes, and has been expanded by identification of phenocopies such as mutations in IL6ST and ZNF341. In this review we summarize the published literature on STAT3-HIES, present the diverse clinical manifestations of this syndrome with current management strategies, and update on the uncertain role of stem cell transplantation for this disease. We outline key unanswered questions for further study.

P011 Sharing is caring: a regional service development project exploring secondary immunosuppression in children

Background/Aims 

The range of approved immunosuppressive and immunomodulatory (IM) agents has grown considerably with an increasing list of indications across paediatric specialties. At present, there is limited evidence supporting best practice for prescribing and monitoring of IM agents in children and young people (CYP). We present a staged service development project exploring cross-specialty prescribing and monitoring of IM agents at a tertiary children’s hospital (Great North Children’s Hospital, GNCH) and data sharing with local hospitals across northeast England.

Methods 

In Phase 1, we searched pharmacy databases and surveyed specialty teams in GNCH to identify clinicians regularly prescribing IM agents to CYP over a twelve-month period. Phase 2 was a cross-specialty retrospective case-notes review of prescribing, monitoring and infection surveillance in a representative sample of CYP on IM agents. Phase 3 explored information sharing with six other hospitals in the region and acute presentations to these sites involving CYP on IM agents.

Results 

Phase 1 identified 9 paediatric and 2 adult specialties prescribing IM agents to 416 CYP. 32 discrete IM therapies were prescribed with significant between-specialty overlap in drugs prescribed but a wide range of prescribing and monitoring practices. Phase 2 assessed 77 CYP on IM agents in detail - 57% were prescribed &gt;1 IM agent, 100% had FBC measured at least once (range once only to weekly), 18% developed lymphopenia at least once and 40% were prescribed prophylactic antibiotics. Previous varicella exposure had been assessed in 70%. Phase 3 data are summarised in Table 1. P011 Table 1:Information sharing and acute presentations to regional hospitals local to immunosuppressed patientsTotal number of patients141Mean age in years (range)11 (2 - 17)NDiagnosisJIA without uveitis108JIA with uveitis9Uveitis alone8Systemic JIA4Period fever4Behçet’s disease2Juvenile dermatomyositis2Scleroderma1Juvenile systemic lupus erythematosus1Mixed connective tissue disease1Granulomatosis with polyangiitis1Immunosuppressive or immunomodulatory agent usedAdalimumab65Methotrexate42Tocilizumab22Mycophenolate mofetil10Etanercept10Infliximab5Sulfasalazine5Prednisolone4Abatacept4Leflunomide4Canakinumab2Colchicine2Anakinra2Rituximab2Cyclophosphamide1Number of immunosuppressive or immunomodulatory agents per patient3 agents52 agents441 agent92Number of acute presentations by diagnosis or presenting complaint (n = 19)Fever4Chickenpox4Viral upper respiratory tract infection2Joint pain2Abdominal pain2Rash2Eye infection1Tonsilitis1Wheeze1Yes (%)No (%)Named local consultant (n = 129)3763Correct diagnosis recorded locally (n = 130)8020Correct immunosuppressive or immunomodulatory agent recorded locally (n = 130)5050Open access for febrile illness (n = 116)4159Reviewed in past 2 years for acute illness (n = 109)1783Note: presented numbers for immunosuppressive or immunomodulatory agents are not mutually exclusive. JIA, juvenile idiopathic arthritis

Conclusion 

IM agents are central to modern paediatric clinical care across a wide range of diseases. This staged project identified significant variation in IM prescribing and monitoring practice between specialties at GNCH. Communication between specialty and local teams is inadequate. Particular areas of concern include limited diagnostic, blood monitoring and medication information sharing and limited local information governing management of intercurrent illness and vaccination. Although different disease processes can necessitate different advice and prescribing practices, sharing examples of good practice will minimise unnecessary variation. We propose the development of a regional immunosuppression working group to improve quality and safety across our region.

Disclosure 

J.L. Bennett: None. C. Tsilifis: None. A. Flinn: None. T. Altmann: None. N. Jansen: None. H. Tumelty: None. K. Aitken: None. S. Bhopal: None. E. Harrison: None. S. Ravenscroft: None. E. Sen: None. E. Williams: None. T. Flood: None. S. Sampath: None. A. Battersby: None. F. McErlane: None.

Hematopoietic Stem Cell Transplantation Resolves the Immune Deficit Associated with STAT3-Dominant-Negative Hyper-IgE Syndrome

Autosomal dominant hyper-IgE syndrome caused by dominant-negative loss-of-function mutations in signal transducer and activator of transcription factor 3 (STAT3) (STAT3-HIES) is a rare primary immunodeficiency with multisystem pathology. The quality of life in patients with STAT3-HIES is determined by not only the progressive, life-limiting pulmonary disease, but also significant skin disease including recurrent infections and abscesses requiring surgery. Our early report indicated that hematopoietic stem cell transplantation might not be effective in patients with STAT3-HIES, although a few subsequent reports have reported successful outcomes. We update on progress of our patient now with over 18 years of follow-up and report on an additional seven cases, all of whom have survived despite demonstrating significant disease-related pathology prior to transplant. We conclude that effective cure of the immunological aspects of the disease and stabilization of even severe lung involvement may be achieved by allogeneic hematopoietic stem cell transplantation. Recurrent skin infections and abscesses may be abolished. Donor T_H17 cells may produce comparable levels of IL17A to healthy controls. The future challenge will be to determine which patients should best be offered this treatment and at what point in their disease history.

Neonatal Thoracic Infection with Mixta

The Erwiniaceae are a family of gram-negative, aerobic coliforms which are pathogenic to a number of plants. Recently described within this family are the Pantoea, strains of which have been associated with infection in immunocompromised children and post-surgical meningitis but also colonisation of a healthy human subject's gastrointestinal tract, as well as a variety of agricultural diseases. In 2015, a further clade of this family was established as the genus Mixta.

In this case report, we describe infection of the pleural space and lung parenchyma with members of Mixta in a term neonate following an anastomic leak post-primary repair of congenital trache-oesophageal fistula, causing a respiratory and cardiovascular deterioration. Mixta were identified by MALDI-TOF. The child made a full recovery with use of intravenous piperacillin-tazobactam.

The Mixta genus must be added to a list of opportunistic pathogens responsible for infection following perforation of the gastrointestinal tract.