Severe combined immunodeficiency: recent developments and guidance on clinical management

A Novel Truncating Mutation in PAX1 Gene Causes Otofaciocervical Syndrome Without Immunodeficiency

Otofaciocervical syndrome (OTFCS) is a rare genetic disorder of both autosomal recessive and autosomal dominant patterns of inheritance. It is caused by biallelic or monoallelic mutations in PAX1 or EYA1 genes, respectively. Here, we report an OTFCS2 female patient of 1st consanguineous healthy parents. She manifested facial dysmorphism, hearing loss, intellectual disability (ID), and delayed language development (DLD) as the main clinical phenotype. The novel homozygous variant c.1212dup (p.Gly405Argfs*51) in the PAX1 gene was identified by whole exome sequencing (WES), and family segregation confirmed the heterozygous status of the mutation in the parents using the Sanger sequencing. The study recorded a novel PAX1 variant representing the sixth report of OTFCS2 worldwide and the first Egyptian study expanding the geographic area where the disorder was confined.

Defining the Clinical, Emotional, Social, and Financial Burden of Congenital Athymia

INTRODUCTION

Characterize the burden of illness in pediatric patients with congen̄ital athymia who were receiving supportive care.

METHODS

This cross-sectional study of adult caregivers of patients with congenital athymia used both a quantitative survey and qualitative interviews. Caregivers of patients currently receiving supportive care responded to questions about the past 12 months and completed the parent proxy version of the Pediatric Quality of Life Inventory Generic instrument (PedsQL) for patients aged 2-4 years. For caregivers of patients who had received supportive care in the past, questions were asked about the period when they were receiving supportive care only.

RESULTS

The sample included caregivers of 18 patients, 5 who were currently receiving supportive care and 13 who received investigational cultured human thymus tissue implantation before study enrollment and had received supportive care in the past. The impact of congenital athymia was substantial. Reports included the need to live in isolation (100% of respondents); caregiver emotional burden such as fear of death, infection, and worries about the future (100%); financial hardship (78%); and the inability to meet family/friends (72%). Patients had frequent and prolonged hospitalizations (78%) and had high utilization of procedures, medications, and home medical supplies. Caregiver-reported PedsQL scores for patients currently receiving supportive care (n = 4) indicated low health-related quality of life.

CONCLUSIONS

Caregivers of patients with congenital athymia reported high clinical, emotional, social, and financial burden on patients and their families.

Congenital Athymia: Genetic Etiologies, Clinical Manifestations, Diagnosis, and Treatment

Congenital athymia is an ultra-rare disease characterized by the absence of a functioning thymus. It is associated with several genetic and syndromic disorders including FOXN1 deficiency, 22q11.2 deletion, CHARGE Syndrome (Coloboma, Heart defects, Atresia of the nasal choanae, Retardation of growth and development, Genitourinary anomalies, and Ear anomalies), and Complete DiGeorge Syndrome. Congenital athymia can result from defects in genes that impact thymic organ development such as FOXN1 and PAX1 or from genes that are involved in development of the entire midline region, such as TBX1 within the 22q11.2 region, CHD7, and FOXI3. Patients with congenital athymia have profound immunodeficiency, increased susceptibility to infections, and frequently, autologous graft-versus-host disease (GVHD). Athymic patients often present with absent T cells but normal numbers of B cells and Natural Killer cells (T-B+NK+), similar to a phenotype of severe combined immunodeficiency (SCID); these patients may require additional steps to confirm the diagnosis if no known genetic cause of athymia is identified. However, distinguishing athymia from SCID is crucial, as treatments differ for these conditions. Cultured thymus tissue is being investigated as a treatment for congenital athymia. Here, we review what is known about the epidemiology, underlying etiologies, clinical manifestations, and treatments for congenital athymia.

Economic burden of congenital athymia in the United States for patients receiving supportive care during the first 3 years of life

AIMS

Congenital athymia is an ultra-rare pediatric condition characterized by the lack of thymus in utero and the naïve T cells critical for infection defense and immune regulation. Patients with congenital athymia receive supportive care to minimize and treat infections, autoimmune phenomena, and autologous graft-versus-host disease (aGVHD) manifestations, but historically, die within the first 3 years of life with supportive care only. We estimated the healthcare resource utilization and economic burden of supportive care over patients' first 3 years of life in the United States.

METHODS

A medical chart audit by the treating physician was used to collect patient data from birth to age 3 on clinical manifestations associated with congenital athymia (clinical manifestations due to underlying syndromic conditions excluded). Using costs and charges from publicly available sources, the total economic burden of direct medical costs and charges for the first 3 years of life (considered "lifetime" for patients receiving supportive care) and differences in economic burden between patients with higher and lower inpatient hospitalization durations were estimated.

RESULTS

All patients (n = 10) experienced frequent infections and aGVHD manifestations; 40% experienced ≥1 episode of sepsis, and 20% had recurrent sepsis episodes annually. The estimated mean 3-year economic burden per patient was US$5,534,121 (2020 US dollars). The annual mean inpatient hospitalization duration was 150.6 days. Inpatient room charges accounted for 79% of the economic burden, reflecting the high costs of specialized care settings required to prevent infection, including isolation. Patients with high inpatient utilization (n = 5; annual mean inpatient hospitalization duration, 289.6 days) had an estimated 3-year economic burden of US$9,926,229.

LIMITATIONS

The total economic burden may not be adequately represented due to underestimation of some direct costs or overestimation of others.

CONCLUSIONS

Current treatment of patients with congenital athymia (supportive care) presents a high economic burden to the healthcare system.

Host genetics and infectious disease: new tools, insights and translational opportunities

Understanding how human genetics influence infectious disease susceptibility offers the opportunity for new insights into pathogenesis, potential drug targets, risk stratification, response to therapy and vaccination. As new infectious diseases continue to emerge, together with growing levels of antimicrobial resistance and an increasing awareness of substantial differences between populations in genetic associations, the need for such work is expanding. In this Review, we illustrate how our understanding of the host–pathogen relationship is advancing through holistic approaches, describing current strategies to investigate the role of host genetic variation in established and emerging infections, including COVID-19, the need for wider application to diverse global populations mirroring the burden of disease, the impact of pathogen and vector genetic diversity and a broad array of immune and inflammation phenotypes that can be mapped as traits in health and disease. Insights from study of inborn errors of immunity and multi-omics profiling together with developments in analytical methods are further advancing our knowledge of this important area.

Infectious diseases are an ever-present global threat. In this Review, Kwok, Mentzer and Knight discuss our latest understanding of how human genetics influence susceptibility to disease. Furthermore, they discuss emerging progress in the interplay between host and pathogen genetics, molecular responses to infection and vaccination, and opportunities to bring these aspects together for rapid responses to emerging diseases such as COVID-19.

Mutational landscape of severe combined immunodeficiency patients from Turkey

Severe combined immunodeficiency (SCID) has a diverse genetic aetiology, where a clinical phenotype, caused by single and/or multiple gene variants, can give rise to multiple presentations. The advent of next-generation sequencing (NGS) has recently enabled rapid identification of the molecular aetiology of SCID, which is crucial for prognosis and treatment strategies. We sought to identify the genetic aetiology of various phenotypes of SCIDs and assessed both clinical and immunologic characteristics associated with gene variants. An amplicon-based targeted NGS panel, which contained 18 most common SCID-related genes, was contumely made to screen the patients (n = 38) with typical SCID, atypical SCID or OMENN syndrome. Allelic segregations were confirmed for the detected gene variants within the families. In total, 24 disease-causing variants (17 known and 7 novel) were identified in 23 patients in 9 different SCID genes: RAG1 (n = 5), RAG2 (n = 2), ADA (n = 3), DCLRE1C (n = 2), NHEJ1 (n = 2), CD3E (n = 2), IL2RG (n = 3), JAK3 (n = 4) and IL7R (n = 1). The overall success rate of our custom-made NGS panel was 60% (39.3% for NK+ SCID and 100% for NK- SCID). Incidence of autosomal-recessive inherited genes is more frequently found in our cohort than the previously reported populations probably due to the high consanguineous marriages in Turkey. In conclusion, the custom-made sequencing panel was able to identify and confirm the previously known and novel disease-causing variants with high accuracy.

Gene analysis of seven cases of primary immunodeficiency

BACKGROUND

Primary immune deficiency diseases (PID) are a group of potentially serious disorders in which inherited defects in the immune system lead to increased infections. This paper explores the clinical characteristics and pathogenic gene mutation of PID.

METHODS

The clinical data, clinical manifestations, and gene sequencing results of seven children were analyzed.

RESULTS

Among the seven children, six were male, and one was female, aged from 4 months to 13 years old. All of them had a history of repeated infection and pneumonia. High throughput sequencing (NGS) showed that the BTK gene of case 1 had c.1921c > t mutation; the BTK gene of case 2 had c.906-908del splice site mutation; the BTK gene of case 3 had c.718delg mutation; the cybb gene of case 4 had c.469c > t mutation; the IL2RG gene of case 5 had c.202g > A mutation; the STAT1 gene of case 6 had c.854a > G mutation; the case 7 had c.718delg mutation. There was c.1154c > t mutation in the STAT1 gene. Cases 1, 3, 6 and 7 were new mutations, and cases 2, 4, and 5 were inherited from mothers.

CONCLUSIONS

In clinical cases of children with recurrent infection, the immunologic index is abnormal, so we need to be highly aware of the possibility of PID, and timely high-throughput sequencing is helpful for the diagnosis.

Latin American consensus on the supportive management of patients with severe combined immunodeficiency

Severe combined immunodeficiency (SCID) represents the most lethal form of primary immunodeficiency, with mortality rates of greater than 90% within the first year of life without treatment. Hematopoietic stem cell transplantation and gene therapy are the only curative treatments available, and the best-known prognostic factors for success are age at diagnosis, age at hematopoietic stem cell transplantation, and the comorbidities that develop in between. There are no evidence-based guidelines for standardized clinical care for patients with SCID during the time between diagnosis and definitive treatment, and we aim to generate a consensus management strategy on the supportive care of patients with SCID. First, we gathered available information about SCID diagnostic and therapeutic guidelines, then we developed a document including diagnostic and therapeutic interventions, and finally we submitted the interventions for expert consensus through a modified Delphi technique. Interventions are grouped in 10 topic domains, including 123 "agreed" and 38 "nonagreed" statements. This document intends to standardize supportive clinical care of patients with SCID from diagnosis to definitive treatment, reduce disease burden, and ultimately improve prognosis, particularly in countries where newborn screening for SCID is not universally available and delayed diagnosis is the rule. Our work intends to provide a tool not only for immunologists but also for primary care physicians and other specialists involved in the care of patients with SCID.

Use of Ceftolozane/tazobactam for the Treatment of Multidrug-resistant Pseudomonas aeruginosa Pneumonia in a Pediatric Patient with Combined Immunodeficiency (CID): A Case Report from a Tertiary Hospital in Saudi Arabia

Infections, with multidrug-resistant Pseudomonas aeruginosa, are a major concern in the pediatric intensive care unit, especially in immunocompromised patients. Some of these strains are resistant to all beta-lactams, including carbapenems, leaving very limited treatment options remaining. These options include aminoglycosides and colistin, both of which have poor pharmacokinetic profiles with significant toxicities. Newer beta-lactam/beta-lactamase inhibitor combinations offer additional novel options to treat such infections, given their good pharmacokinetic profiles and activity against multi-drug resistant strains. Ceftolozane/tazobactam is a novel cephalosporin/beta-lactamase inhibitor combination approved in 2014. The drug demonstrates good activity against multidrug-resistant P. aeruginosa strains, including those resistant to all other antibiotics. Ceftolozane/tazobactam is currently approved in adult patients 18 years and older only. There are very limited data on its pharmacokinetic profile and clinical utility in the pediatric population. We report the use of ceftolozane/tazobactam to successfully treat pneumonia caused by multidrug-resistant P. aeruginosa in a pediatric patient with combined immunodeficiency syndrome.

Novel IL2RG Mutation Causes Leaky TLOWB+NK+ SCID With Nodular Regenerative Hyperplasia and Normal IL-15 STAT5 Phosphorylation

X-linked severe combined immunodeficiency disease (SCID) is caused by mutations in the interleukin (IL)-2 receptor γ (IL2RG) gene and patients usually present with a TBNK SCID phenotype. Nevertheless, a minority of these patients present with a TBNK phenotype, similar to the IL-7R-deficient patients. We report a patient with a novel missense p.Glu297Gly mutation in the IL2RG gene presenting with a leaky TBNK SCID with delayed onset, moderate susceptibility to infections, and nodular regenerative hyperplasia. He presents with preserved STAT5 tyrosine phosphorylation in response to IL-15 stimulation but not in response to IL-2 and IL-7, resulting in the NK phenotype.

Co-appearance of OPV and BCG vaccine-derived complications in two infants with severe combined immunodeficiency

Infants with severe combined immunodeficiency (SCID) are at risk of developing severe life-threatening infections if they are inadvertently given attenuated live vaccines. Concomitant appearance of two live vaccine-associated complications in one person is rarely reported. In this study, we present two SCID infants, who received BCG and oral polio vaccines according to their local immunization schedule early in life, before the diagnosis of immunodeficiency was made. Their clinical presentation, extensive immunological workup, genetic tests, and clinical disease course are presented. Both patients developed localized and disseminated infections originating from the BCG vaccine (BCGitis and BCGiosis, respectively) and in addition suffered from diarrhea and chronic fecal secretion of vaccine-derived poliovirus. Alarmingly, in case 2, the poliovirus was a type 2 vaccine-derived poliovirus in which both neurovirulence attenuation sites reverted to the neurovirulent genotype. These cases highlight the importance of early recognition of SCID by neonatal screening or thorough family anamnesis, and the need to further defer the timing of administration of attenuated live vaccines.

Inmunodeficiencia combinada severa (SCID) en Neiva, Colombia. Reporte de caso

Introducción. Las inmunodeficiencias primarias son enfermedades genéticas del sistema inmune que incrementan la susceptibilidad a infecciones. Una de las formas más graves en niños es la inmunodeficiencia combinada severa.Presentación del caso. Se presenta el caso de un niño que fue diagnosticado con inmunodeficiencia combinada severa; este era un paciente masculino de ocho meses que presentó cuadro clínico consistente en múltiples hospitalizaciones debido a infección por citomegalovirus, endocarditis por Candida albicans e infección recurrente de las vías urinarias por Pseudomonas aeruginosa.El perfil inmunológico mostró disminución del número absoluto de células CD3+ y CD19+, lo que permitió realizar el diagnóstico de inmunodeficiencia combinada severa instaurándose manejo; sin embargo, el niño no se recuperó y falleció.Conclusiones. Las inmunodeficiencias primarias son patologías que requieren una intervención oportuna que permita brindar un mejor pronóstico a los pacientes.

Detecting 22q11.2 Deletion Syndrome in Newborns with Low T Cell Receptor Excision Circles from Severe Combined Immunodeficiency Screening

OBJECTIVE

Based on experiences and results from newborn screening for severe combined immunodeficiency (SCID), we evaluated the occurrence of chromosome 22q11.2 deletion syndrome (22q11.2DS) in newborns with different T cell receptor excision circles (TREC) results and established a second tier genetic test for 22q11.2DS.

STUDY DESIGN

Recalled dried blood spots from 486 newborns with TREC results <90 copies/uL were tested from the SCID newborn screening. Quantitative real-time polymerase chain reaction assay was used to detect the copy number of TBX1 and HIRA genes by simple DNA extraction method. Multiplex ligation dependent probe amplification was used for further confirmation.

RESULTS

Four hundred sixty-eight cases were considered negative because their haploid copy number of TBX1 and HIRA genes was >0.75. Eighteen cases with TBX1 and/or HIRA gene copy number <0.75 were suspected as positive, and 13 cases were further confirmed with 22q11.2DS. Detection rates of 22q11.2DS were 10.7% (6/56) in TREC <30 copies, 6.8% (9/132) in <50 TREC copies, 4.6% (12/260) in <70 TREC copies, and 2.7% (13/486) in <90 TREC copies.

CONCLUSIONS

22q11.2DS detection can be incorporated into the second-tier assay in subjects with low TREC copies in SCID screening. The dried blood spot methods were feasible for 22q11.2DS newborn screening.

Uncommon Neonatal Skin Lesions

Certain rashes and cutaneous lesions in a newborn can be clues to more concerning diseases and conditions if recognized and evaluated promptly. Langerhans cell histiocytosis, cutaneous forms of cancer (such as leukemia cutis, neuroblastoma, and rhabdomyosarcoma), developmental abnormalities such as neural tube or spinal dysraphism, and aplasia cutis congenita, nutritional deficiency, and immunodeficiency all have a range of cutaneous findings that will be reviewed herein to guide diagnosis and management. [Pediatr Ann. 2019;48(1):e30-e35.].

A novel pathogenic frameshift variant of CD3E gene in two T-B+ NK+ SCID patients from Turkey

Severe combined immunodeficiency (SCID) is the most severe form of primary immunodeficiency, which is characterized by the dysfunction and/or absence of T lymphocytes. Early diagnosis of SCID is crucial for overall survival, and if it remains untreated, SCID is often fatal. Next-generation sequencing (NGS) has become a rapid, high-throughput technology, and has already been proven to be beneficial in medical diagnostics. In this study, a targeted NGS panel was developed to identify the genetic variations of SCID by using SmartChip-TE technology, and a novel pathogenic frameshift variant was found in the CD3E gene. Sanger sequencing has confirmed the segregation of the variant among patients. We found a novel deletion in the CD3E gene (NM000733.3:p.L58Hfs*9) in two T-B+ NK+ patients. The variant was not found in the databases of dbSNP, ExAC, and 1000G. One sibling in family I was homozygous and the rest of the family members were heterozygous for this variant. T cell receptor excision circle (TREC) and kappa-deleting recombination excision circle (KREC) analyses were performed for T and B cell maturation. TRECs were not detected in both patients and the KREC copy numbers were similar to the other family members. In addition, heterozygous family members showed decreased TREC levels when compared with the wild-type sibling, indicating that carrying this variant in one allele does not cause immunodeficiency, but does effect T cell proliferation. Here, we report a novel pathogenic frameshift variant in CD3E gene by using targeted NGS panel.

Identification of 22q11.2 Deletion Syndrome via Newborn Screening for Severe Combined Immunodeficiency

PURPOSE

Chromosome 22q11.2 deletion syndrome (22q11.2DS), the most common cause of DiGeorge syndrome, is quite variable. Neonatal diagnosis traditionally relies on recognition of classic features and cytogenetic testing, but many patients come to attention only following identification of later onset conditions, such as hypernasal speech due to palatal insufficiency and developmental and behavioral differences including speech delay, autism, and learning disabilities that would benefit from early interventions. Newborn screening (NBS) for severe combined immunodeficiency (SCID) is now identifying infants with 22q11.2DS due to T cell lymphopenia. Here, we report findings in such neonates, underscoring the efficacy of early diagnosis.

METHODS

A retrospective chart review of 1350 patients with 22q11.2DS evaluated at the Children's Hospital of Philadelphia identified 11 newborns with a positive NBS for SCID.

RESULTS

Five out of 11 would have been diagnosed with 22q11.2DS without NBS, whereas early identification of 22q11.2DS in 6/11 led to the diagnosis of significant associated features including hypocalcemia, congenital heart disease (CHD), and gastroesophageal reflux disease that may have gone unrecognized and therefore untreated.

CONCLUSIONS

Our findings support rapidly screening infants with a positive NBS for SCID, but without SCID, for 22q11.2DS even when typically associated features such as CHD are absent, particularly when B cells and NK cells are normal. Moreover, direct NBS for 22q11.2DS using multiplex qPCR would be equally, if not more, beneficial, as early identification of 22q11.2DS will obviate a protracted diagnostic odyssey while providing an opportunity for timely assessment and interventions as needed, even in the absence of T cell lymphopenia.

Newborn Sequencing in Genomic Medicine and Public Health

The rapid development of genomic sequencing technologies has decreased the cost of genetic analysis to the extent that it seems plausible that genome-scale sequencing could have widespread availability in pediatric care. Genomic sequencing provides a powerful diagnostic modality for patients who manifest symptoms of monogenic disease and an opportunity to detect health conditions before their development. However, many technical, clinical, ethical, and societal challenges should be addressed before such technology is widely deployed in pediatric practice. This article provides an overview of the Newborn Sequencing in Genomic Medicine and Public Health Consortium, which is investigating the application of genome-scale sequencing in newborns for both diagnosis and screening.

Eczema and Urticaria as Manifestations of Undiagnosed and Rare Diseases

Eczema and urticaria are common disorders encountered in pediatric patients, but they may occasionally be the presenting complaint in a child with an underlying rare disease. Immunodeficiency syndromes should be suspected when eczema is associated with neonatal onset, recurrent infections, chronic lymphadenopathy, or failure to thrive. Nutritional deficiencies and mycosis fungoides are in the differential diagnosis for a child with a recalcitrant eczematous eruption. Autoinflammatory syndromes should be suspected in a child with chronic urticaria, fever, and other systemic signs of inflammation. Although these disorders are rare, early recognition allows for appropriate treatment and decreased morbidity for the child.

FOXN1 deficient nude severe combined immunodeficiency

Nude severe combined immunodeficiency is a rare inherited disease caused by autosomal recessive loss-of-function mutations in FOXN1. This gene encodes a transcription factor essential for the development of the thymus, the primary lymphoid organ that supports T-cell development and selection. To date nine cases have been reported presenting with the clinical triad of absent thymus resulting in severe T-cell immunodeficiency, congenital alopecia universalis and nail dystrophy. Diagnosis relies on testing for FOXN1 mutations, which allows genetic counselling and guides therapeutic management. Options for treating the underlying immune deficiency include HLA-matched genoidentical haematopoietic cell transplantation containing mature donor T-cells or thymus tissue transplantation. Experience from other severe combined immune deficiency syndromes suggests that early diagnosis, supportive care and definitive management result in better patient outcomes. Without these the prognosis is poor due to early-onset life threatening infections.

Family History of Early Infant Death Correlates with Earlier Age at Diagnosis But Not Shorter Time to Diagnosis for Severe Combined Immunodeficiency

BACKGROUND

Severe combined immunodeficiency (SCID) is fatal unless treated with hematopoietic stem cell transplant. Delay in diagnosis is common without newborn screening. Family history of infant death due to infection or known SCID (FH) has been associated with earlier diagnosis.

OBJECTIVE

The aim of this study was to identify the clinical features that affect age at diagnosis (AD) and time to the diagnosis of SCID.

METHODS

From 2005 to 2016, 147 SCID patients were referred to the Asian Primary Immunodeficiency Network. Patients with genetic diagnosis, age at presentation (AP), and AD were selected for study.

RESULTS

A total of 88 different SCID gene mutations were identified in 94 patients, including 49 IL2RG mutations, 12 RAG1 mutations, 8 RAG2 mutations, 7 JAK3 mutations, 4 DCLRE1C mutations, 4 IL7R mutations, 2 RFXANK mutations, and 2 ADA mutations. A total of 29 mutations were previously unreported. Eighty-three of the 94 patients fulfilled the selection criteria. Their median AD was 4 months, and the time to diagnosis was 2 months. The commonest SCID was X-linked (n = 57). A total of 29 patients had a positive FH. Candidiasis (n = 27) and bacillus Calmette-Guérin (BCG) vaccine infection (n = 19) were the commonest infections. The median age for candidiasis and BCG infection documented were 3 months and 4 months, respectively. The median absolute lymphocyte count (ALC) was 1.05 × 10⁹/L with over 88% patients below 3 × 10⁹/L. Positive FH was associated with earlier AP by 1 month (p = 0.002) and diagnosis by 2 months (p = 0.008), but not shorter time to diagnosis (p = 0.494). Candidiasis was associated with later AD by 2 months (p = 0.008) and longer time to diagnosis by 0.55 months (p = 0.003). BCG infections were not associated with age or time to diagnosis.

CONCLUSION

FH was useful to aid earlier diagnosis but was overlooked by clinicians and not by parents. Similarly, typical clinical features of SCID were not recognized by clinicians to shorten the time to diagnosis. We suggest that lymphocyte subset should be performed for any infant with one or more of the following four clinical features: FH, candidiasis, BCG infections, and ALC below 3 × 10⁹/L.

Clinical Features Before Hematopoietic Stem Cell Transplantation or Enzyme Replacement Therapy of Children With Combined Immunodeficiency

BACKGROUND

Survival of children with combined immunodeficiency is strongly related to patient's age and clinical situation at the time of hematopoietic stem cell transplantation (HSCT). We describe the clinical features before HSCT or enzyme replacement therapy (ERT) in a cohort of children treated in a National Reference Unit.

METHODS

A retrospective study of children with CIDs treated in our Hospital during a 20-year period (1995-2014) was performed, analyzing their clinical situation before HSCT/ERT.

RESULTS

Thirty-one children were included. Risk factors such as family history or consanguinity were present in 35% of cases, but only 3 children (9%) were initially studied because of family history. Median ages at clinical onset, diagnosis and HSCT/ERT were 3.3, 5.6 and 8.1 months, respectively. All patients had lymphopenia before HSCT/ERT. At the time of admission to our unit, 68% of cases had abnormal lung auscultation, 72% were malnourished, 45% reported chronic gastroenteritis and 35% had hepatosplenomegaly. Before HSCT/ERT, respiratory infections and sepsis episodes were documented in 80% and 42% of cases, respectively. In 23% of children, a viral systemic infection was confirmed. The mortality rate was 35%, and 72% of children who died had Gram-negative bacterial sepsis or a viral infection.

CONCLUSIONS

The present study shows the characteristics and outcome of children with CIDs in the absence of neonatal screening. Although all our patients had lymphopenia and most of them had suffered relevant infections or had a positive family history, these factors were not identified early. Respiratory and systemic viral infections were the main source of infection with important implications in clinical outcome. Our results highlight the importance of the implementation of neonatal screening, to improve survival rates.

Update on the safety and efficacy of retroviral gene therapy for immunodeficiency due to adenosine deaminase deficiency

Adenosine deaminase (ADA) deficiency is a rare, autosomal-recessive systemic metabolic disease characterized by severe combined immunodeficiency (SCID). The treatment of choice for ADA-deficient SCID (ADA-SCID) is hematopoietic stem cell transplant from an HLA-matched sibling donor, although <25% of patients have such a donor available. Enzyme replacement therapy (ERT) partially and temporarily relieves immunodeficiency. We investigated the medium-term outcome of gene therapy (GT) in 18 patients with ADA-SCID for whom an HLA-identical family donor was not available; most were not responding well to ERT. Patients were treated with an autologous CD34(+)-enriched cell fraction that contained CD34(+) cells transduced with a retroviral vector encoding the human ADA complementary DNA sequence (GSK2696273) as part of single-arm, open-label studies or compassionate use programs. Overall survival was 100% over 2.3 to 13.4 years (median, 6.9 years). Gene-modified cells were stably present in multiple lineages throughout follow up. GT resulted in a sustained reduction in the severe infection rate from 1.17 events per person-year to 0.17 events per person-year (n = 17, patient 1 data not available). Immune reconstitution was demonstrated by normalization of T-cell subsets (CD3(+), CD4(+), and CD8(+)), evidence of thymopoiesis, and sustained T-cell proliferative capacity. B-cell function was evidenced by immunoglobulin production, decreased intravenous immunoglobulin use, and antibody response after vaccination. All 18 patients reported infections as adverse events; infections of respiratory and gastrointestinal tracts were reported most frequently. No events indicative of leukemic transformation were reported. Trial details were registered at www.clinicaltrials.gov as #NCT00598481.

Long-term multilineage engraftment of autologous genome-edited hematopoietic stem cells in nonhuman primates

Genome editing in hematopoietic stem and progenitor cells (HSPCs) is a promising novel technology for the treatment of many human diseases. Here, we evaluated whether the disruption of the C-C chemokine receptor 5 (CCR5) locus in pigtailed macaque HSPCs by zinc finger nucleases (ZFNs) was feasible. We show that macaque-specific CCR5 ZFNs efficiently induce CCR5 disruption at levels of up to 64% ex vivo, 40% in vivo early posttransplant, and 3% to 5% in long-term repopulating cells over 6 months following HSPC transplant. These genome-edited HSPCs support multilineage engraftment and generate progeny capable of trafficking to secondary tissues including the gut. Using deep sequencing technology, we show that these ZFNs are highly specific for the CCR5 locus in primary cells. Further, we have adapted our clonal tracking methodology to follow individual CCR5 mutant cells over time in vivo, reinforcing that CCR5 gene-edited HSPCs are capable of long-term engraftment. Together, these data demonstrate that genome-edited HSPCs engraft, and contribute to multilineage repopulation after autologous transplantation in a clinically relevant large animal model, an important step toward the development of stem cell-based genome-editing therapies for HIV and potentially other diseases as well.

A Boy with Relentless Pruritus: Job's Syndrome

Patient: Male, 6

Final Diagnosis: Job’s Syndrome (hyper IgE syndrome)

Symptoms: Pruritus

Medication: —

Clinical Procedure: None

Specialty: Allergology

Genetically engineered livestock for biomedical models

To commemorate Transgenic Animal Research Conference X, this review summarizes the recent progress in developing genetically engineered livestock species as biomedical models. The first of these conferences was held in 1997, which turned out to be a watershed year for the field, with two significant events occurring. One was the publication of the first transgenic livestock animal disease model, a pig with retinitis pigmentosa. Before that, the use of livestock species in biomedical research had been limited to wild-type animals or disease models that had been induced or were naturally occurring. The second event was the report of Dolly, a cloned sheep produced by somatic cell nuclear transfer. Cloning subsequently became an essential part of the process for most of the models developed in the last 18 years and is stilled used prominently today. This review is intended to highlight the biomedical modeling achievements that followed those key events, many of which were first reported at one of the previous nine Transgenic Animal Research Conferences. Also discussed are the practical challenges of utilizing livestock disease models now that the technical hurdles of model development have been largely overcome.

Severe combined immunodeficiencies and related disorders

Severe combined immunodeficiencies (SCIDs) comprise a group of rare, monogenic diseases that are characterized by an early onset and a profound block in the development of T lymphocytes. Given that adaptive immunity is abrogated, patients with SCID are prone to recurrent infections caused by both non-opportunistic and opportunistic pathogens, leading to early death unless immunity can be restored. Several molecular defects causing SCIDs have been identified, along with many other defects causing profound, albeit incomplete, T cell immunodeficiencies; the latter are referred to as atypical SCIDs or combined immunodeficiencies. The pathophysiology of many of these conditions has now been characterized. Early, accurate and precise diagnosis combined with the ongoing implementation of newborn screening have enabled major advances in the care of infants with SCID, including better outcomes of allogeneic haematopoietic stem cell transplantation. Gene therapy is also becoming an effective option. Further advances and a progressive extension of the indications for gene therapy can be expected in the future. The assessment of long-term outcomes of patients with SCID is now a major challenge, with a view to evaluating the quality and sustainability of immune restoration, the risks of sequelae and the ability to relieve the non-haematopoietic syndromic manifestations that accompany some of these conditions.