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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., (© 2022. The Author(s).)

Molecular dissection of inborn errors of immunity can help to elucidate the nonredundant functions of individual genes. We studied 3 children with an immune dysregulation syndrome of susceptibility to infection, lymphadenopathy, hepatosplenomegaly, developmental delay, autoimmunity, and lymphoma of B-cell (n = 2) or T-cell (n = 1) origin. All 3 showed early autologous T-cell reconstitution following allogeneic hematopoietic stem cell transplantation. By whole-exome sequencing, we identified rare homozygous germline missense or nonsense variants in a known epigenetic regulator of gene expression: ten-eleven translocation methylcytosine dioxygenase 2 (TET2). Mutated TET2 protein was absent or enzymatically defective for 5-hydroxymethylating activity, resulting in whole-blood DNA hypermethylation. Circulating T cells showed an abnormal immunophenotype including expanded double-negative, but depleted follicular helper, T-cell compartments and impaired Fas-dependent apoptosis in 2 of 3 patients. Moreover, TET2-deficient B cells showed defective class-switch recombination. The hematopoietic potential of patient-derived induced pluripotent stem cells was skewed toward the myeloid lineage. These are the first reported cases of autosomal-recessive germline TET2 deficiency in humans, causing clinically significant immunodeficiency and an autoimmune lymphoproliferative syndrome with marked predisposition to lymphoma. This disease phenotype demonstrates the broad role of TET2 within the human immune system., (© 2020 by The American Society of Hematology.)

Haematopoietic SCT (HSCT) is curative for many children with primary immunodeficiencies or other non-malignant conditions. Outcome for those admitted to intensive care following HSCT for oncology diagnoses has historically been very poor. There is no literature available specifically regarding the outcome for children with primary immunodeficiency requiring intensive care following HSCT. We reviewed our post-HSCT admission to intensive care over a 5-year period. A total of 111 children underwent HSCT. Median age at transplant was 1 year 4 months. The most common diagnosis was SCID. In all, 35% had at least one intensive care admission and 44% survived to be discharged from intensive care. Also, 73% of admission episodes requiring invasive ventilation but no inotropes or renal replacement therapy resulted in survival to discharge. Children undergoing HSCT for immunological diagnoses had a high rate of admission to intensive care. No factors were identified that could predict the need for admission. Invasive ventilation alone has a much better outcome than that in historical series. However, the need for multi-organ system support was still associated with a poor outcome. This information is useful when counselling families of children that have deteriorated and been admitted to intensive care during the HSCT procedure.

Background: Hematopoietic stem cell transplantation remains the only treatment for most patients with severe combined immunodeficiencies (SCIDs) or other primary immunodeficiencies (non-SCID PIDs)., Objective: To analyze the long-term outcome of patients with SCID and non-SCID PID from European centers treated between 1968 and 2005., Methods: The product-limit method estimated cumulative survival; the log-rank test compared survival between groups. A Cox proportional-hazard model evaluated the impact of independent predictors on patient survival., Results: In patients with SCID, survival with genoidentical donors (n = 25) from 2000 to 2005 was 90%. Survival using a mismatched relative (n = 96) has improved (66%), similar to that using an unrelated donor (n = 46; 69%; P = .005). Transplantation after year 1995, a younger age, B(+) phenotype, genoidentical and phenoidentical donors, absence of respiratory impairment, or viral infection before transplantation were associated with better prognosis on multivariate analysis. For non-SCID PID, in contrast with patients with SCID, we confirm that, in the 2000 to 2005 period, using an unrelated donor (n = 124) gave a 3-year survival rate similar to a genoidentical donor (n = 73), 79% for both. Survival was 76% in phenoidentical transplants (n = 23) and worse in mismatched related donor transplants (n = 47; 46%; P = .016)., Conclusion: This is the largest cohort study of such patients with the longest follow-up. Specific issues arise for different patient groups. Patients with B-SCID have worse survival than other patients with SCID, despite improvements in each group. For non-SCID PID, survival is worse than SCID, although more conditions are now treated. Individual disease categories now need to be analyzed so that disease-specific prognosis may be better understood and the best treatments planned., (Copyright (c) 2010 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

More than 11 genetic causes of severe combined immunodeficiency (SCID) have been identified, affecting development and/or function of T lymphocytes, and sometimes B lymphocytes and natural killer (NK) cells. Deletion of 22q11.2 is associated with immunodeficiency, although less than 1% of cases are associated with T-B + NK + SCID phenotype. Severe immunodeficiency with CHARGE syndrome has been noted only rarely Omenn syndrome is a rare autosomal recessive form of SCID with erythroderma, hepatosplenomegaly, lymphadenopathy and alopecia. Hypomorphic recombination activating genes 1 and 2 mutations were first described in patients with Omenn syndrome. More recently, defects in Artemis, RMRP, IL7Ralpha and common gamma chain genes have been described. We describe four patients with mutations in CHD7, who had clinical features of CHARGE syndrome and who had T-B + NK + SCID (two patients) or clinical features consistent with Omenn syndrome (two patients). Immunodeficiency in patients with DiGeorge syndrome is well recognized--CHARGE syndrome should now be added to the causes of T-B + NK + SCID, and mutations in the CHD7 gene may be associated with Omenn-like syndrome.

Pulmonary infection, often insidious, is frequent in primary immunodeficiency (PID) and acquired immunodeficiency. Pulmonary complications are serious obstacles to success of haematopoietic SCT (HSCT) for these conditions. Bronchoalveolar lavage (BAL) permits identification of lower respiratory tract pathogens that may direct specific treatment and influence prognosis. There are no reports about the utility of pre-HSCT BAL for immunodeficient patients. We prospectively studied the value of 'routine' BAL before commencing transplantation in patients undergoing HSCT for severe immunological disease. Routine non-bronchoscopic BAL was performed under general anaesthetic, a few days before commencing pre-HSCT cytoreductive chemotherapy. Patients were categorized as symptomatic or asymptomatic with respect to pulmonary disease or infection. Samples were sent for microbiological processing. Complications arising from the procedure, pathogens isolated and treatments instituted were recorded. Results were available from 69/75 patients transplanted during the study period; 26 (38%) had pathogens identified (six asymptomatic patients), 10 (14.5%) developed complications post-procedure (two asymptomatic patients)-all recovered, 21 had management changes. There was no statistically significant difference in the number of positive isolates from severe combined or other immunodeficient patients, or of symptomatic or asymptomatic patients. Routine non-bronchoscopic BAL is safe in immunodeficient patients about to undergo HSCT, and leads to management changes.

Recombinase activating genes 1/2 (RAG1/2) deficiency, critical to initiate gene rearrangement encoding lymphocyte receptors, causes T-B- severe combined immunodeficiency (SCID) and Omenn syndrome (OS), characterised by erythroderma, hepatosplenomegaly, lymphadenopathy, activated, clonal T cell expansions with restricted TCRVbeta family usage, and opportunistic infection. Many features of OS resemble graft-versus-host disease (GvHD). Frequency of GvHD-associated cytokine gene polymorphisms (CGPs) with OS was investigated to explain phenotypic differences between T-B- SCID and OS. Allele frequencies of IFNgamma T874A, IFNgamma-R1, TNFalphad microsatellites, IL-10 promoter region C592A and A1082G, IL-4 C-590T, IL-6 G-174C, IL-4R Q+576R, IFNgamma-R1 T-56C, TNFalphaRII 196 M/R single-nucleotide polymorphisms and IL-1Ra intron 1 VNTR were examined in 33 OS and 23 SCID patients. No significant differences in allele frequencies were found between the groups, and no trends identified. The mechanisms determining the OS or T-B-NK+ SCID phenotype remain to be determined.

Background: Patients with severe combined immunodeficiency and preexisting viral pneumonitis formally had a poor outcome from hematopoietic stem cell transplantation. With inhaled steroid and antitumor necrosis factor alpha antibody treatment, results improved. The poor outcome of patients with viral central nervous system infection prompted this retrospective single center review., Results: Eight of 71 patients with severe combined immunodeficiency transplanted since 1987 were identified with viral central nervous system infection (adenovirus [1], cytomegalovirus [2], Epstein-Barr virus [2], parvovirus [1], varicella zoster virus [1], human herpesvirus 6 [1]). Nonspecific neurologic symptoms included drowsiness, irritability, head lag, fisting and floppiness. Later symptoms included unresponsiveness, apnea, posturing, hypotonia, hyperreflexia and seizures. All had neuroradiologic investigations. Only one had an initially normal computed tomography scan. Magnetic resonance image abnormalities included cerebral atrophy, basal ganglia changes, diffuse leukoencephalopathy, and multifocal mass lesions. Five patients had virus identified from cerebrospinal fluid by polymerase chain reaction and brain tissue examination from 3 patients identified human herpesvirus 6, adenovirus type 41 and varicella zoster virus. Three children remain alive, 2 received replete marrow and one remains untransplanted. Others who received T cell depleted marrow died of neurologic sequelae., Conclusion: Outcome of viral central nervous system infection after hematopoietic stem cell transplantation for severe combined immunodeficiency is poor, particularly associated with T cell depleted marrow.

Omenn syndrome (OS) is characterised by hepatosplenomegaly, lymphadenopathy, erythema, eosinophilia, elevated IgE, oligoclonal T cell expansions and recombinase activating gene (RAG) mutations. We investigated 9 cases of OS to correlate genotype with immunophenotype using a two-color flow cytometry with monoclonal antibodies against CD3 and TCRVB families to map TCRVB usage. T and B clonal cell populations were examined in peripheral blood lymphocytes by PCR and sequencing of TCRB/TCRG T cell and IGH FR2/FR3 B cell products. RAG and Artemis genes were sequenced from genomic DNA. All patients demonstrated absent TCRVB families; six had predominant TCRVB families, six oligoclonal TCR gene rearrangements including TCRGD rearrangements. One demonstrated functional IGH rearrangement, an observation not previously reported. In this clinically homogeneous population, with similar immunological phenotype, RAG mutations were identified in only 2/9 patients. OS is a genetically heterogeneous condition, and patients with similar immunophenotypes may have as yet unidentified gene defects.

Adenovirus causes disseminated disease following bone marrow transplantation (BMT). We report a child who underwent T-cell-depleted BMT. Adenovirus subgenus F serotype 41 was detected antemortem by PCR in cerebrospinal fluid and postmortem in other tissues. Serotypes 40 and 41, associated with gastrointestinal disease, have not previously been implicated in disseminated disease.

Established treatment of severe combined immunodeficiencies (SCID) and other primary immunodeficiencies (PID) is bone marrow transplantation (BMT). Normal lymphocyte numbers and protein antigen responses are present within 2 years of BMT, polysaccharide antibody responses appear last. Streptococcus pneumoniae infection causes significant morbidity and mortality post-BMT. Previous studies have shown good protein antigen responses post-BMT for SCID and PID, but had not examined the polysaccharide responses. We retrospectively analysed pneumococcal polysaccharide (PPS) responses in our patient series. In total, 22 SCID and 12 non-SCID PID were evaluated, all >2 years post BMT: 17 SCID, 12 PID received chemotherapy conditioning; 17 SCID, three PID had T-cell depleted (TCD) BMT, others had nonconditioned whole marrow BMT. All had normal Haemophilus influenza B and tetanus antibody responses. Of 22 SCID, 13 vs 11/12 PID responded to PPS vaccine (P=0.05). There was no association with donor age, GvHD, B-cell chimerism, or IgG2 level. Fewer TCD marrow recipients responded to PPS (P=0.04). Analysis of the SCID group showed no association of PPS response with type of marrow received. This is the first study to specifically examine PPS antibody responses following SCID and PID BMT. Pneumococcal conjugate vaccine antibody responses should be examined in these children.

Aims: To evaluate outcome following neonatal bone marrow transplantation (BMT) for severe combined immunodeficiency (SCID) when there is a family history of a previously affected sibling, and to compare results with those published for in utero BMT., Methods: A retrospective review of cases referred and transplanted between 1987 and 1999, focusing on infectious and graft versus host disease (GvHD) complications after BMT, and T and B lymphocyte function. Thirteen patients received 18 stem cell transplants: four whole marrow, one cord blood, 10 parental T cell depleted (TCD) haplo-identical, and three TCD unrelated donor BMT. Nine were conditioned with busulphan and cyclophosphamide., Results: All are alive and well (six months to 11.5 years after BMT). Six had grade I-II acute GvHD and two chronic GvHD (now resolved). Three had a top up BMT for poor T cell function, one had a third BMT for graft failure and chronic GvHD, and one had a third BMT for graft failure. Twelve have good in vitro proliferation to T cell mitogens, and all have normal serum IgA levels. Three receive intravenous immunoglobulin; for one of these, it is less than one year since BMT. Nine are above the 2nd centile, and 10 of 12 old enough to be assessed have normal neurodevelopment., Conclusion: These results are better than those published for in utero BMT for SCID. Early postnatal BMT should be the preferred option in neonatal SCID.

Early diagnosis of severe combined immunodeficiency (SCID) is important to enable prompt referral to a supraregional centre for bone marrow transplantation before the occurrence of end organ damage secondary to infective complications. This review outlines clinical, microbiological, and immunopathological clues that aid the diagnosis of SCID and emphasises the multidisciplinary approach needed to diagnose and treat these infants.

Background: SCID can be cured by BMT. Depletion of mature T cells from BM has enabled HLA non-identical stem-cell transplantation. We report the outcome of 30 patients treated with 37 T-cell depleted BMT procedures using CAMPATH-1M in vitro between 1987-98 in a single center., Methods: Immune reconstitution and quality-of-life were assessed in 19 longterm survivors. All but two received pre-transplant conditioning. T- and B-cell chimerism, numbers and function were analyzed during a median follow-up of 5.3 years (range 1.33-12)., Results: The overall engraftment rate was 59%, six children required repeated BMT and the survival rate was 63%. All have donor T cells, 58% normal T-cell numbers and 74% normal T-cell function. Of 17 evaluated, 16 patients (94%) have normal IgM and IgG levels, and production of specific Abs to protein Ags, but only 5/16 (31%) have a good response to pneumococcal polysaccharide. Early and late post-BMT complications were rare and there were no delayed deaths. Only one child continues on long-term i.v. Ig 4-years post-BMT. Eleven children died (37%)., Discussion: CAMPATH-1M T-cell depleted BMT for SCID resulted in 63% survival. Deaths of 11 children were mainly due to pre-existing infections. Seventeen of 19 long-term survivors have normal immune function and good quality-of-life.

Respiratory viral infections are major causes of morbidity and mortality in children with SCID and other primary immunodeficiencies who require BMT. Twenty-two of 73 (30%) such children were admitted with respiratory viral infections, of whom 13/22 (59%) died. All viruses were detected in nasopharyngeal aspirate (NPA). Virus was only found in BAL in those with LRTI. Eleven of 22 (50%) had paramyxovirus infections, all with severe viral pneumonitis which worsened post BMT. Five of 11 (45.5%) survived overall. All 11 received aerosolised ribavirin; five of 11 received additional inhaled immunoglobulin and corticosteroid. Three of 5 (60%) survived compared with two of six (33.3%) not thus treated. Three of 22 (13.6%) had adenoviruses; one died of disseminated disease, including pneumonia despite intravenous ribavirin. Eleven patients had rhinovirus detected; nine of 11 (82%) were asymptomatic or coryzal and survived. Two patients with additional severe lung pathologies had LRT rhinovirus and died. All patients received intravenous immunoglobulin. No treatments resulted in viral clearance without successful T cell engraftment. Respiratory viruses, particularly paramyxoviruses and adenoviruses are common, significant pathogens in these patients, significantly worsening outcome of BMT. NPA is an ideal specimen for diagnosis and monitoring of infection. Aggressive treatments may reduce viral replication and damage. Nebulised immunoglobulin and corticosteroid in LRTI may improve respiratory function and outcome.

The clinical course of 10 children who have been diagnosed with major histocompatibility complex (MHC) class II deficiency (bare lymphocyte syndrome) in the UK over the past eight years is described. They have had a generally poor prognosis, with only two of the 10 still alive despite eight attempts at bone marrow transplantation in six patients. Overwhelming viral infection was the predominant cause of death. Alternative transplant strategies or novel therapies are required for these patients.

Unlabelled: A preterm baby born with scaly skin who later developed recurrent infections and was subsequently diagnosed to have Omenn syndrome is presented., Conclusion: Any baby with ichthyotic skin and recurrent infections should have immunodeficiency considered in the differential diagnosis.

Background: Pneumocystis carinii is an important pathogen in immunodeficiency but may be an unrecognised cause of respiratory compromise., Objectives: To ascertain the incidence of P carinii pneumonia (PCP) at presentation of severe combined immunodeficiency (SCID), whether it had been diagnosed, and the effect of treatment on outcome., Setting: The supraregional paediatric bone marrow transplant unit for primary immunodeficiencies at Newcastle General Hospital., Methods: Retrospective case note review of infants referred with a diagnosis of SCID from 1992 to 1998., Results: Ten of 50 infants had PCP at presentation; only one was diagnosed before transfer. Eight were diagnosed by bronchoalveolar lavage and two by lung biopsy. In only one was P carinii identified in nasopharyngeal secretions. Five required ventilation for respiratory failure but all were successfully treated with co-trimoxazole and methylprednisolone with or without nebulised budesonide. Nine survived to bone marrow transplantation and four are long term survivors after bone marrow transplantation; no deaths were related to PCP., Conclusions: PCP is a common presenting feature of SCID but is rarely recognised. Bronchoalveolar lavage or lung biopsy are needed for diagnosis. Treatment with co-trimoxazole is highly successful.

Respiratory syncytial virus and parainfluenza virus infection carry a poor prognosis in severe combined immunodeficiency (SCID), particularly if the viral load is high. Patients with high viral load develop severe pneumonitis at engraftment which may possibly be modulated by immunotherapy, including high dose nebulised corticosteroids. Further work is required to develop effective treatment for this severe condition.

Bone marrow transplantation is the only curative treatment for children with severe combined immunodeficiency (SCID). In the absence of an HLA-identical sibling, haploidentical parental donor marrow can be used provided it is depleted of T cells to prevent otherwise inevitable GVHD. Campath 1M has been successfully used for this procedure in several centres. In our centre 17 SCID patients plus one with combined immunodeficiency (CID) were transplanted with Campath 1M T cell-depleted bone marrow. Progenitor cell recovery, before and after T cell depletion, was monitored using granulocyte-macrophage colony-forming cell assays (GMCFU) and CD34 analysis. The numbers of GMCFU/kg transplanted correlated with engraftment and survival post-transplant and monitoring CD34+ cell numbers in the T cell-depleted marrow pretransplant may be an additional indicator of successful engraftment. Use of a buffy coat marrow preparation with restriction of the number of T cells to < 5 x 10(5)/kg was associated with graft failure in four and death in five of eight children, probably because too few stem cells were infused. T cell depletion of a mononuclear cell preparation of donor marrow with no arbitrary ceiling of infused T cells is highly effective at preventing clinically important GVHD and cured nine out of 10 children transplanted with such material.

An infant with severe combined immunodeficiency (SCID) is described, who presented with severe anaemia and hepatosplenomegaly due to disseminated Bacillus Calmette-Guérin (BCG) infection involving the bone marrow, liver and spleen. After BMT, huge splenic enlargement occurred, presumably due to proliferation of engrafted donor lymphocytes, leading to severe hypersplenism. Peripheral blood cell consumption was resolved by splenectomy, but gradual loss of the marrow graft followed.

Materno-fetal GVHD is commonly a fatal condition occurring in patients with severe combined immunodeficiency (SCID). Definitive diagnosis is often difficult. We describe a patient with clinical features suggestive of materno-fetal GVHD but in whom histology was atypical. Y chromosome-specific PCR amplification analysis of DNA extracted from the skin biopsy was performed to detect chimeric evidence of infiltrating maternal T cells. This revealed strong positivity for the Y chromosome, indicating lack of maternal T cell engraftment and thus confirming a diagnosis of Omenn's syndrome, a variant of SCID in which atypical lymphocyte clones give rise to a similar picture. In contrast, Y chromosome-specific PCR analysis of skin biopsy DNA from a male patient with a rash clinically and histologically typical of materno-fetal GVHD revealed absence of the Y chromosome, indicating infiltration of maternal cells and thus confirming the diagnosis of materno-fetal GVHD. Y chromosome-specific PCR analysis is thus a useful investigation for the differentiation of materno-fetal GVHD from Omenn's syndrome in pre-BMT SCID patients presenting with unexplained rash.

Infants with severe combined immunodeficiency syndrome (SCIDS) have a greatly improved prognosis if diagnosed and treated before they develop overwhelming infection. Clinical and laboratory data on 45 patients with SCIDS were retrospectively reviewed to assess the value of absolute lymphocyte counts in making an early diagnosis. Ninety infants matched for age, sex, and presenting symptoms were used as controls. Thirteen (29%) infants with SCIDS were diagnosed at birth as previous siblings had been affected; 32 (71%) were diagnosed after the development of symptoms. Eighteen (56%) of these remained undiagnosed until after 6 months of age. The first symptoms occurred at a median of 5 weeks (range 1 day to 8 months) and the first admission to hospital was at 4 months (range 1 week to 16 months). Symptoms included respiratory infection (91%), vomiting and diarrhoea (81%), failure to thrive (88%), candidiasis (50%), and skin lesions (28%). The mean lymphocyte count was 1.71 x 10(9)/l compared with 7.2 x 10(9)/l in controls. Excluding one child with Omenn's syndrome (lymphocyte count 23.3 x 10(9)/l, all symptomatic infants with SCIDS had lymphocyte counts less than 2.8 x 10(9)/l at presentation. The median delay between the first abnormal lymphocyte count and diagnosis was seven weeks (range one day to 13 months). Twenty eight (88%) of 32 infants would have been diagnosed before 6 months of age if investigated after the first low lymphocyte count. These data indicate that low lymphocyte counts are predictive of SCIDS. Paediatricians are urged to pay attention to the absolute lymphocyte counts in all infants in whom a full blood count is performed. Those with lymphocyte counts persistently less than 2.8 x 10(9)l should be investigated for SCIDS.