The Experts below are selected from a list of 198 Experts worldwide ranked by ideXlab platform
Jakob Nilsson - One of the best experts on this subject based on the ideXlab platform.
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severe combined immunodeficiency scid presenting in childhood with agammaglobulinemia associated with novel compound heterozygous mutations in DCLRE1C
Clinical Immunology, 2019Co-Authors: Mikael Sundin, Kim Ramme, Antonios G A Kolios, Per Marits, Jakob NilssonAbstract:Abstract Severe combined immunodeficiency (SCID) can be caused by deleterious mutations in DCLRE1C, leading to deficient non-homologous end joining by compromising the function of the Artemis protein. This impairs the process of V(D)J recombination of the T- and B-cell receptors and typically results in radiosensitive T−, B−, NK+ SCID presenting during the first months of life. We present a case of a 3-year-old girl with two novel compound heterozygous variants in DCLRE1C (c.58G>C and c.374A>C) that were associated with marked reduced numbers of peripheral T- and B-cells and undetectable total serum IgG. Despite the severe laboratory phenotype, the patient had a normal development, albeit failure to thrive (−2.5 to −3 SD), during her first years of life including day-care attendance at preschool for 1.5 years. After being diagnosed with pneumonia the clinical picture of SCID was recognized and the girl successfully underwent hematopoietic stem-cell transplantation.
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late presenting atypical severe combined immunodeficiency scid associated with a novel missense mutation in DCLRE1C
Applied Immunohistochemistry & Molecular Morphology, 2018Co-Authors: Mikael Sundin, Michael Uhlin, Ahmed Gaballa, Kim Ramme, Antonios G A Kolios, Per Marits, Jakob NilssonAbstract:Immunodeficiency associated with mutations in the DNA cross-link repair 1C gene (DCLRE1C) can have variable clinical presentations including severe combined immunodeficiency (SCID), Omenn syndrome, atypical SCID or common variable immunodeficiency (CVID) (1-3). DCLRE1C encodes the protein Artemis, a nuclease with intrinsic 5′-3′ exonuclease activity on single-stranded DNA that is involved in non-homologous end joining (NHEJ). Artemis is essential for V(D)J recombination of the immunoglobulin and T-cell receptor genes that occur during B- and T-cell development.
Morton J. Cowan - One of the best experts on this subject based on the ideXlab platform.
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early outcome of a phase i ii clinical trial nct03538899 of gene corrected autologous cd34 hematopoietic cells and low exposure busulfan in newly diagnosed patients with artemis deficient severe combined immunodeficiency art scid
Biology of Blood and Marrow Transplantation, 2020Co-Authors: Misako Kawahara, Jason Yu, Ukina Sanford, Morton J. Cowan, Janelle Facchino, Shivali M Chag, Carol Fraserbrowne, Janel Longboyle, Jess OhAbstract:Background ART-SCID represents ∼3% of all SCID, but occurs in 1/2000 births in Athabascan-speaking Native Americans. Artemis protein, encoded by DCLRE1C, is essential for repairing DNA double-stranded breaks, including those generated during V(D)J recombination essential for T & B cell development. Artemis-deficiency causes not only T-B-NK+ SCID, but also increased sensitivity to alkylating drugs and radiation. ART-SCID is the most difficult type of SCID to treat with allogeneic hematopoietic cell transplantation due to high rates of rejection and GVHD, and incomplete immune reconstitution, combined with increased toxicity following exposure to intensive conditioning regimens. Thus, we developed a self-inactivating lentiviral vector containing the human Artemis promoter and cDNA (AProArt) and are evaluating its toxicity and efficacy in a Phase I/II trial in ART-SCID patients. Methods Newly diagnosed infants with ART-SCID needed to be at least 2 m/o with acceptable organ function and no matched sibling donor. CD34+ cells were isolated from bone marrow, cultured with cytokines, transduced x2 with AProArt, and cryopreserved. Patients received 2 daily doses of busulfan (PK targeted for a cumulative exposure (cAUC) of 20mg*hr/L) followed the next day by infusion of thawed cells. Results Five newly diagnosed infants have been enrolled and treated at a median age of 2.6m (range 2.3-3.7), all diagnosed by newborn screening for SCID, with a median follow-up of 10.5m (range 0-15.6). The mean (SD) Bu cAUC was 18.8±0.9 mg*hr/L. Infants received 6.6±2.4 × 106 AProArt-transduced CD34+ cells/kg with average vector copy number (VCN) in the grafts of 2.1±1.0 copies/cell and transduction efficiency 75±9%. There were no serious busulfan side effects. Four evaluable patients (≥4w post infusion) had transduced blood cells by 4w, and 3/3 evaluable patients (≥8w) developed multilineage gene marking (T, B, NK and myeloid cells) (Fig. 1). Gene-corrected CD3, CD4, CD4+45RA+CCR7+, CD8 and CD19 cells have appeared in the 3/3 evaluable patients (≥8w) (Fig. 2) with normalization of lymphocyte proliferation to mitogen in all 3 (Fig. 3). All 3 are now off isolation and managed as outpatients, although 2 developed autoimmune hemolytic anemia (AIHA) that resolved in PT001 by 18m of age and did not require therapy in PT002. Infections included rhinovirus at presentation in PT001 that resolved with T cell reconstitution. After discharge PT002 acquired and recovered from CMV and rotavirus. Analyses of insertion sites and T cell receptor diversity are pending. Conclusion Infusion of AProArt-transduced autologous CD34+ cells into ART-SCID infants pretreated with very low exposure busulfan has resulted in multilineage engraftment of transduced cells with reconstitution of T cell immunity and evidence for B cell immune development. AIHA, the only complication, has resolved upon development of T cell immunity.
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Radiation-sensitive severe combined immunodeficiency: The arguments for and against conditioning before hematopoietic cell transplantation—what to do?
The Journal of Allergy and Clinical Immunology, 2015Co-Authors: Morton J. Cowan, Andrew R. GenneryAbstract:Defects in DNA cross-link repair 1C (DCLRE1C), protein kinase DNA activated catalytic polypeptide (PRKDC), ligase 4 (LIG4), NHEJ1, and NBS1 involving the nonhomologous end-joining (NHEJ) DNA repair pathway result in radiation-sensitive severe combined immunodeficiency (SCID). Results of hematopoietic cell transplantation for radiation-sensitive SCID suggest that minimizing exposure to alkylating agents and ionizing radiation is important for optimizing survival and minimizing late effects. However, use of preconditioning with alkylating agents is associated with a greater likelihood of full T- and B-cell reconstitution compared with no conditioning or immunosuppression alone. A reduced-intensity regimen using fludarabine and low-dose cyclophosphamide might be effective for patients with LIG4, NHEJ1, and NBS1 defects, although more data are needed to confirm these findings and characterize late effects. For patients with mutations in DCLRE1C (Artemis-deficient SCID), there is no optimal approach that uses standard dose-alkylating agents without significant late effects. Until nonchemotherapy agents, such as anti-CD45 or anti-CD117, become available, options include minimizing exposure to alkylators, such as single-agent low-dose targeted busulfan, or achieving T-cell reconstitution, followed several years later with a conditioning regimen to restore B-cell immunity. Gene therapy for these disorders will eventually remove the issues of rejection and graft-versus-host disease. Prospective multicenter studies are needed to evaluate these approaches in this rare but highly vulnerable patient population.
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292. Lentivirus Vector Mediated Gene Correction in Artemis-Deficient Severe Combined Immunodeficiency
Molecular Therapy, 2015Co-Authors: Divya Punwani, Jason Yu, Denise A Carbonaro, Jennifer M Puck, Misako Stillion, Harry L. Malech, Donald B. Kohn, Scott R. Mcivor, Morton J. CowanAbstract:Mutations in DCLRE1C/Artemis, a DNA repair gene, cause T-B-NK+ SCID by preventing V(D)J recombination in T and B cell progenitors and also confer heightened sensitivity to irradiation and alkylator chemotherapy. SCID newborn screening identifies Artemis-deficient SCID (ART-SCID) early in life and while allogeneic hematopoietic cell transplantation can cure ART-SCID, preparative regimens for conditioning are poorly tolerated. Without alkylating chemotherapy patients may have graft failure while toxic effects of chemotherapy include increased mortality, short stature and abnormal dental development. Thus, building on experience with X-linked and ADA deficient SCID, we found addition of a normal Artemis gene to hematopoietic stem cells (HSC) an attractive strategy to treat ART-SCID.Since overexpression of Artemis protein causes cellular cytotoxicity, a lentivirus vector with human Artemis cDNA and its endogenous promoter (Apro-hART) was produced and used to transduce fibroblasts from ART-SCID patients and controls. Apro-hART transduced ART-SCID fibroblasts showed correction of radiosensitivity by enumeration of foci of DNA damage and proliferation assays. Radiosensitivity of cells lacking the DNA repair enzyme Ligase-4 was not corrected. View Large Image | Download PowerPoint SlideMobilized peripheral blood CD34+ cells from an ART-SCID patient, incapable of differentiation into T and B cells, were transduced with Apro-hART or GFP lentivirus and cultured on OP9 cells or injected into irradiated newborn NSG mice. OP9 cocultures and blood and spleen cells from NSG mice showed that Apro-hART-corrected, but not GFP-transduced, ART-SCID CD34+ cells differentiated into B cells and T and B cells, respectively, as did GFP-transduced control CD34+ cells. Lymphocyte maturation was proven by lineage specific surface markers and measures of V(D)J diversity and recombination, T cell receptor Vbeta spectratyping and Kappa chain receptor excision circles (KRECs), respectively. View Large Image | Download PowerPoint SlideColony forming assays with transduced cells revealed transduction efficiency of 28.6%, a mean vector copy number of 3/cell and a diverse profile of lentivirus integration sites.This successful gene correction and restoration of Artemis function in fibroblasts and HSCs from ART-SCID patients supports institution of a clinical trial of gene addition therapy for ART-SCID.
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Radiosensitive Severe Combined Immunodeficiency Disease
Immunology and Allergy Clinics of North America, 2010Co-Authors: Christopher C. Dvorak, Morton J. CowanAbstract:Severe Combined Immunodeficiency Disease (SCID) has classically been divided into those patients with residual B cells (T-B+ phenotype) and those whose defects produce an absence of both T cells and B cells (T-B- phenotype). The T-B- phenotype accounts for approximately 30% of SCID patients and is associated with worse outcomes following hematopoietic cell transplantation (HCT) in most [1–4], but not all [5] studies. A variety of genetic mutations have now been linked to the T-B- phenotype, most of which result in defects in the protein machinery required for the V(D)J recombination events critical for producing the diverse repertoire of the T- and B-cell immune system. The first step in V(D)J recombination involves creation of double-stranded DNA (dsDNA) breaks and subsequent hairpin formation by an enzymatic complex produced by the Recombination Activating genes (RAG) 1 and 2 (Figure 1). Defects in RAG also produce a T-B- form of SCID, but without radiosensitivity [6]. However, once the dsDNA breaks are created by the RAG complex, proper repair must take place in order to avoid a differentiation arrest, which in B cells occurs at the transition from cytoplasmic Igμ negative to Igμ positive pre-B cells, and in T cells occurs at the transition from pro-T to double negative pro-T cells [7,8]. Figure 1 V(D)J Recombination: Initial process and hairpin formation. Non-Homologous End Joining Eukaryotic cells possess two mechanisms by which dsDNA breaks are repaired: homologous recombination (HR) and non-homologous end joining (NHEJ). Defects in genes that produce components of the homologous recombination pathway result in diseases such as Ataxia Telangiectasia [9], Seckel Syndrome [10], Nijimegan Breakage Syndrome [11], and Fanconi Anemia [11], which are characterized by physical abnormalities with either immunodeficiency and/or predisposition to cancer development. The NHEJ pathway is especially critical in the repair of the dsDNA breaks created by the RAG process during the V(D)J recombination in T- and B- lymphocytes (Figure 2). After a dsDNA break is created, the first protein that binds to the ends of the dsDNA breaks is a heterodimer known as Ku 80/86 [12]. Ku then recruits a complex made up of two proteins: Artemis (also known as DNA cross-link repair enzyme 1C, or DCLRE1C) and DNA-dependent protein kinase catalytic subunit (DNA-PKcs). This complex performs two functions via it’s nuclease activity: first, it opens the DNA hairpins created by the RAG complex; and second, it acts to trim the ends to variable extents, thereby contributing to functional diversity [13]. Finally, the two ends of DNA are ligated together, a task carried out by a complex of two proteins: DNA Ligase IV and X-ray cross-complementation group 4 protein (XRCC4) [14,15]. Another factor, known as Cernunnos-XLF, accumulates at the site of dsDNA breaks and appears to stimulate the DNA Ligase IV: XRCC4 complex [16]. Figure 2 The Non-Homologous End Joining Pathway Agents Responsible for Double Stranded DNA Breaks Although defects in NHEJ are classically considered to produce “radiosensitive” forms of SCID, in fact, a wide variety of agents other than ionizing radiation produce dsDNA breaks via reactive oxygen species. These breaks would normally be repaired through the same NHEJ mechanism as radiation-induced damage. Cell lines from Artemis-deficient patients are moderately sensitive to mitomycin C, an alkylating agent that causes DNA crosslinks of guanine nucleotides by attaching an alkyl group [17]. Crosslinking makes it impossible for DNA strands to successfully uncoil and separate during the normal DNA replication process, so that affected cells are unable to divide properly. The stalled replication fork is normally repaired by excision of the damaged area, and subsequent DNA re-joining via the components of either the homologous recombination or NHEJ pathways. This property of alkylating agents forms the basis of their utility as anti-cancer chemotherapeutic agents. These chemotherapy medications were then adopted for their utility in the conditioning process to prepare a patient (including potentially a patient with SCID) to undergo an allogeneic HCT, since they can target the immune system, in order to prevent graft rejection, and/or host hematopoietic cells, thereby opening niches in the bone marrow microenvironment for donor cells to attach and grow. Classical alkylating agents include those in the nitrogen mustard family (e.g., cyclophosphamide and melphalan), as well as busulfan and thiotepa [18]. Another essential component of the allogeneic HCT process is control over the alloreactive donor T cells ability to cause graft-versus-host disease (GVHD). Traditionally, this has been accomplished through the use of calcineurin inhibitors, which block downstream signaling from the IL-2 receptor. Interestingly, the calcineurin inhibitor cyclosporine can produce dsDNA breaks, at least in cells deficient in DNA Ligase IV [19].
Mikael Sundin - One of the best experts on this subject based on the ideXlab platform.
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severe combined immunodeficiency scid presenting in childhood with agammaglobulinemia associated with novel compound heterozygous mutations in DCLRE1C
Clinical Immunology, 2019Co-Authors: Mikael Sundin, Kim Ramme, Antonios G A Kolios, Per Marits, Jakob NilssonAbstract:Abstract Severe combined immunodeficiency (SCID) can be caused by deleterious mutations in DCLRE1C, leading to deficient non-homologous end joining by compromising the function of the Artemis protein. This impairs the process of V(D)J recombination of the T- and B-cell receptors and typically results in radiosensitive T−, B−, NK+ SCID presenting during the first months of life. We present a case of a 3-year-old girl with two novel compound heterozygous variants in DCLRE1C (c.58G>C and c.374A>C) that were associated with marked reduced numbers of peripheral T- and B-cells and undetectable total serum IgG. Despite the severe laboratory phenotype, the patient had a normal development, albeit failure to thrive (−2.5 to −3 SD), during her first years of life including day-care attendance at preschool for 1.5 years. After being diagnosed with pneumonia the clinical picture of SCID was recognized and the girl successfully underwent hematopoietic stem-cell transplantation.
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late presenting atypical severe combined immunodeficiency scid associated with a novel missense mutation in DCLRE1C
Applied Immunohistochemistry & Molecular Morphology, 2018Co-Authors: Mikael Sundin, Michael Uhlin, Ahmed Gaballa, Kim Ramme, Antonios G A Kolios, Per Marits, Jakob NilssonAbstract:Immunodeficiency associated with mutations in the DNA cross-link repair 1C gene (DCLRE1C) can have variable clinical presentations including severe combined immunodeficiency (SCID), Omenn syndrome, atypical SCID or common variable immunodeficiency (CVID) (1-3). DCLRE1C encodes the protein Artemis, a nuclease with intrinsic 5′-3′ exonuclease activity on single-stranded DNA that is involved in non-homologous end joining (NHEJ). Artemis is essential for V(D)J recombination of the immunoglobulin and T-cell receptor genes that occur during B- and T-cell development.
Ulrich Pannicke - One of the best experts on this subject based on the ideXlab platform.
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DCLRE1C artemis mutations causing phenotypes ranging from atypical severe combined immunodeficiency to mere antibody deficiency
Human Molecular Genetics, 2015Co-Authors: Timo Volk, Ulrich Pannicke, Ismail Reisli, Alla Bulashevska, Julia Ritter, Andrea Bjorkman, Alejandro A Schaffer, Manfred Fliegauf, Esra Hazar Sayar, Ulrich SalzerAbstract:Null mutations in genes involved in V(D)J recombination cause a block in B- and T- cell development, clinically presenting as severe combined immunodeficiency (SCID). Hypomorphic mutations in the non-homologous end joining gene DCLRE1C (encoding ARTEMIS) have been described to cause atypical SCID, Omenn syndrome, Hyper IgM syndrome and inflammatory bowel disease - all with severely impaired T-cell immunity. By whole-exome sequencing, we investigated the molecular defect in a consanguineous family with three children clinically diagnosed with antibody deficiency. We identified perfectly segregating homozygous variants in DCLRE1C in three index patients with recurrent respiratory tract infections, very low B cell numbers and serum IgA levels. In patients, decreased colony survival after irradiation, impaired proliferative response, and reduced counts of naive T cells were observed in addition to a restricted T cell receptor repertoire, increased palindromic nucleotides in the complementarity determining regions 3, and long stretches of microhomology at switch junctions. Defective V(D)J recombination was complemented by wild-type ARTEMIS protein in vitro. Subsequently, homozygous or compound heterozygous DCLRE1C mutations were identified in nine patients from the same geographic region. We demonstrate that DCLRE1C mutations can cause a phenotype presenting as only antibody deficiency. This novel association broadens the clinical spectrum associated with ARTEMIS mutations. Clinicians should consider the possibility that an immunodeficiency with a clinically mild initial presentation could be a combined immunodeficiency, so as to provide appropriate care for affected patients.
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scid patients with artemis vs rag deficiencies following hct increased risk of late toxicity in artemis deficient scid
Blood, 2014Co-Authors: Catharina Schuetz, Ulrich Pannicke, Christopher C. Dvorak, Benedicte Neven, Sandrine Leroy, Klaus Schwarz, Ansgar Schulz, Manfred HoenigAbstract:A subgroup of severe combined immunodeficiencies (SCID) is characterized by lack of T and B cells and is caused by defects in genes required for T- and B-cell receptor gene rearrangement. Several of these genes are also involved in nonhomologous end joining of DNA double-strand break repair, the largest subgroup consisting of patients with T−B−NK+SCID due to DCLRE1C/ARTEMIS defects. We postulated that in patients with ARTEMIS deficiency, early and late complications following hematopoietic cell transplantation might be more prominent compared with patients with T−B−NK+SCID caused by recombination activating gene 1/2 (RAG1/2) deficiencies. We analyzed 69 patients with ARTEMIS and 76 patients with RAG1/2 deficiencies who received transplants from either HLA-identical donors without conditioning or from HLA-nonidentical donors without or with conditioning. There was no difference in survival or in the incidence or severity of acute graft-versus-host disease regardless of exposure to alkylating agents. Secondary malignancies were not observed. Immune reconstitution was comparable in both groups, however, ARTEMIS-deficient patients had a significantly higher occurrence of infections in long-term follow-up. There is a highly significant association between poor growth in ARTEMIS deficiency and use of alkylating agents. Furthermore, abnormalities in dental development and endocrine late effects were associated with alkylation therapy in ARTEMIS deficiency.
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the most frequent DCLRE1C artemis mutations are based on homologous recombination events
Human Mutation, 2010Co-Authors: Ulrich Pannicke, M Honig, Ilka Schulze, Jan Rohr, Gitta A Heinz, Sylvia Braun, Ingrid Janz, Evamaria Rump, Markus G Seidel, Susanne MatthesmartinAbstract:The nuclease ARTEMIS is an essential factor of V(D)J recombination during lymphocyte development and in the repair of DNA double-strand breaks (DSB) by the nonhomologous end joining (NHEJ) pathway. Patients with mutations in the DCLRE1C gene, which encodes ARTEMIS, suffer from radiosensitive B−/low T−/low severe combined immunodeficiency (SCID) or radiosensitive Omenn syndrome. To date, causative DCLRE1C mutations inherited as a recessive trait have been reported in 49 patients. In this study, molecular diagnoses of 29 novel patients presenting with the phenotype of B−/low SCID revealed mutations in the DCLRE1C gene. In total, 13 different mutated DCLRE1C alleles were detected, nine of which have not been described before. By far the most frequent mutations (59%) were gross deletions of exons 1–3 or exons 1–4 due to a homologous recombination of the wild-type DCLRE1C gene with a pseudo-DCLRE1C gene located 61.2 kb 5′ to the DCLRE1C start codon. Fine mapping of the recombination intervals revealed private mutations in most cases. MEIG1, a gene encoding a protein that is essential for spermatogenesis in mice, is lost by the gross deletions. Functional analyses on patients' fibroblasts demonstrated that the corresponding alleles carry null mutations of the DCLRE1C gene. Hum Mutat 30:1–11, 2010. © 2010 Wiley-Liss, Inc.
Christopher C. Dvorak - One of the best experts on this subject based on the ideXlab platform.
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Toxicity-Free Hematopoietic Stem Cell Engraftment Achieved with Anti-CD117 Monoclonal Antibody Conditioning
Biology of Blood and Marrow Transplantation, 2019Co-Authors: Rajni Agarwal, Christopher C. Dvorak, Susan S. Prohaska, Janel Long-boyle, Hye-sook Kwon, Janice M. Brown, Kenneth I. Weinberg, Anne Le, Alyssa Guttman-klein, Aaron C LoganAbstract:Successful hematopoietic cell transplantation (HCT) requires vacating recipient hematopoietic stem cell (HSC) niches to permit donor HSC engraftment to provide life-long hematopoietic and immune function. Currently HCT relies on DNA damaging radiation or chemotherapy to achieve HSC niche clearance. We have pursued a non-toxic approach to target and deplete HSC using humanized monoclonal antibody, AMG 191, that binds human CD117 (c-Kit). We opened a Phase 1 dose escalation trial using AMG 191 as the sole conditioning agent to achieve donor HSC engraftment in patients undergoing HCT for severe combined immunodeficiency (SCID). The primary endpoint is to assess the safety of administering AMG 191. Secondary endpoints include AMG 191 pharmacokinetics (PK), host HSC depletion, and determination of the dose of AMG 191 that achieves adequate donor HSC engraftment, defined as >5% donor granulocyte chimerism at 24 weeks. We have completed the first dose cohort of patients receiving 0.1 mg/kg AMG 191 and treated the first two patients in the second cohort (0.3 mg/kg). All five patients tolerated the AMG 191 infusion and the subsequent infusion of their CD34-selectd donor cells without clinical problems. Here we report efficacy in the first two patients, who have reached the 24-week timepoint. Both patients had T-B-NK+ SCID with mutations in the DCLRE1C (Artemis) gene. Both previously received unconditioned HCT as infants, failed to develop donor B cells and remained dependent on exogenous immunoglobulin. CD34-selected mobilized peripheral blood cells from the original donors were infused when the AMG 191 serum level was Conclusion: These data are proof of concept that a humanized monoclonal antibody targeting CD117 can safely clear human HSC niches and facilitate donor HSC engraftment. This study is ongoing and open for enrollment.
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SCID genotype and 6-month posttransplant CD4 count predict survival and immune recovery
Blood, 2018Co-Authors: Elie Haddad, Brent R. Logan, Linda M. Griffith, Rebecca H. Buckley, Roberta E. Parrott, Susan E. Prockop, Trudy N. Small, Jessica Chaisson, Christopher C. Dvorak, Megan MurnaneAbstract:The Primary Immune Deficiency Treatment Consortium (PIDTC) performed a retrospective analysis of 662 patients with severe combined immunodeficiency (SCID) who received a hematopoietic cell transplantation (HCT) as first-line treatment between 1982 and 2012 in 33 North American institutions. Overall survival was higher after HCT from matched-sibling donors (MSDs). Among recipients of non-MSD HCT, multivariate analysis showed that the SCID genotype strongly influenced survival and immune reconstitution. Overall survival was similar for patients with RAG, IL2RG, or JAK3 defects and was significantly better compared with patients with ADA or DCLRE1C mutations. Patients with RAG or DCLRE1C mutations had poorer immune reconstitution than other genotypes. Although survival did not correlate with the type of conditioning regimen, recipients of reduced-intensity or myeloablative conditioning had a lower incidence of treatment failure and better T- and B-cell reconstitution, but a higher risk for graft-versus-host disease, compared with those receiving no conditioning or immunosuppression only. Infection-free status and younger age at HCT were associated with improved survival. Typical SCID, leaky SCID, and Omenn syndrome had similar outcomes. Landmark analysis identified CD4+ and CD4+CD45RA+ cell counts at 6 and 12 months post-HCT as biomarkers predictive of overall survival and long-term T-cell reconstitution. Our data emphasize the need for patient-tailored treatment strategies depending upon the underlying SCID genotype. The prognostic significance of CD4+ cell counts as early as 6 months after HCT emphasizes the importance of close follow-up of immune reconstitution to identify patients who may need additional intervention to prevent poor long-term outcome.
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scid patients with artemis vs rag deficiencies following hct increased risk of late toxicity in artemis deficient scid
Blood, 2014Co-Authors: Catharina Schuetz, Ulrich Pannicke, Christopher C. Dvorak, Benedicte Neven, Sandrine Leroy, Klaus Schwarz, Ansgar Schulz, Manfred HoenigAbstract:A subgroup of severe combined immunodeficiencies (SCID) is characterized by lack of T and B cells and is caused by defects in genes required for T- and B-cell receptor gene rearrangement. Several of these genes are also involved in nonhomologous end joining of DNA double-strand break repair, the largest subgroup consisting of patients with T−B−NK+SCID due to DCLRE1C/ARTEMIS defects. We postulated that in patients with ARTEMIS deficiency, early and late complications following hematopoietic cell transplantation might be more prominent compared with patients with T−B−NK+SCID caused by recombination activating gene 1/2 (RAG1/2) deficiencies. We analyzed 69 patients with ARTEMIS and 76 patients with RAG1/2 deficiencies who received transplants from either HLA-identical donors without conditioning or from HLA-nonidentical donors without or with conditioning. There was no difference in survival or in the incidence or severity of acute graft-versus-host disease regardless of exposure to alkylating agents. Secondary malignancies were not observed. Immune reconstitution was comparable in both groups, however, ARTEMIS-deficient patients had a significantly higher occurrence of infections in long-term follow-up. There is a highly significant association between poor growth in ARTEMIS deficiency and use of alkylating agents. Furthermore, abnormalities in dental development and endocrine late effects were associated with alkylation therapy in ARTEMIS deficiency.
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Radiosensitive Severe Combined Immunodeficiency Disease
Immunology and Allergy Clinics of North America, 2010Co-Authors: Christopher C. Dvorak, Morton J. CowanAbstract:Severe Combined Immunodeficiency Disease (SCID) has classically been divided into those patients with residual B cells (T-B+ phenotype) and those whose defects produce an absence of both T cells and B cells (T-B- phenotype). The T-B- phenotype accounts for approximately 30% of SCID patients and is associated with worse outcomes following hematopoietic cell transplantation (HCT) in most [1–4], but not all [5] studies. A variety of genetic mutations have now been linked to the T-B- phenotype, most of which result in defects in the protein machinery required for the V(D)J recombination events critical for producing the diverse repertoire of the T- and B-cell immune system. The first step in V(D)J recombination involves creation of double-stranded DNA (dsDNA) breaks and subsequent hairpin formation by an enzymatic complex produced by the Recombination Activating genes (RAG) 1 and 2 (Figure 1). Defects in RAG also produce a T-B- form of SCID, but without radiosensitivity [6]. However, once the dsDNA breaks are created by the RAG complex, proper repair must take place in order to avoid a differentiation arrest, which in B cells occurs at the transition from cytoplasmic Igμ negative to Igμ positive pre-B cells, and in T cells occurs at the transition from pro-T to double negative pro-T cells [7,8]. Figure 1 V(D)J Recombination: Initial process and hairpin formation. Non-Homologous End Joining Eukaryotic cells possess two mechanisms by which dsDNA breaks are repaired: homologous recombination (HR) and non-homologous end joining (NHEJ). Defects in genes that produce components of the homologous recombination pathway result in diseases such as Ataxia Telangiectasia [9], Seckel Syndrome [10], Nijimegan Breakage Syndrome [11], and Fanconi Anemia [11], which are characterized by physical abnormalities with either immunodeficiency and/or predisposition to cancer development. The NHEJ pathway is especially critical in the repair of the dsDNA breaks created by the RAG process during the V(D)J recombination in T- and B- lymphocytes (Figure 2). After a dsDNA break is created, the first protein that binds to the ends of the dsDNA breaks is a heterodimer known as Ku 80/86 [12]. Ku then recruits a complex made up of two proteins: Artemis (also known as DNA cross-link repair enzyme 1C, or DCLRE1C) and DNA-dependent protein kinase catalytic subunit (DNA-PKcs). This complex performs two functions via it’s nuclease activity: first, it opens the DNA hairpins created by the RAG complex; and second, it acts to trim the ends to variable extents, thereby contributing to functional diversity [13]. Finally, the two ends of DNA are ligated together, a task carried out by a complex of two proteins: DNA Ligase IV and X-ray cross-complementation group 4 protein (XRCC4) [14,15]. Another factor, known as Cernunnos-XLF, accumulates at the site of dsDNA breaks and appears to stimulate the DNA Ligase IV: XRCC4 complex [16]. Figure 2 The Non-Homologous End Joining Pathway Agents Responsible for Double Stranded DNA Breaks Although defects in NHEJ are classically considered to produce “radiosensitive” forms of SCID, in fact, a wide variety of agents other than ionizing radiation produce dsDNA breaks via reactive oxygen species. These breaks would normally be repaired through the same NHEJ mechanism as radiation-induced damage. Cell lines from Artemis-deficient patients are moderately sensitive to mitomycin C, an alkylating agent that causes DNA crosslinks of guanine nucleotides by attaching an alkyl group [17]. Crosslinking makes it impossible for DNA strands to successfully uncoil and separate during the normal DNA replication process, so that affected cells are unable to divide properly. The stalled replication fork is normally repaired by excision of the damaged area, and subsequent DNA re-joining via the components of either the homologous recombination or NHEJ pathways. This property of alkylating agents forms the basis of their utility as anti-cancer chemotherapeutic agents. These chemotherapy medications were then adopted for their utility in the conditioning process to prepare a patient (including potentially a patient with SCID) to undergo an allogeneic HCT, since they can target the immune system, in order to prevent graft rejection, and/or host hematopoietic cells, thereby opening niches in the bone marrow microenvironment for donor cells to attach and grow. Classical alkylating agents include those in the nitrogen mustard family (e.g., cyclophosphamide and melphalan), as well as busulfan and thiotepa [18]. Another essential component of the allogeneic HCT process is control over the alloreactive donor T cells ability to cause graft-versus-host disease (GVHD). Traditionally, this has been accomplished through the use of calcineurin inhibitors, which block downstream signaling from the IL-2 receptor. Interestingly, the calcineurin inhibitor cyclosporine can produce dsDNA breaks, at least in cells deficient in DNA Ligase IV [19].