TYPE Case Report PUBLISHED 27 December 2022 DOI 10.3389/fimmu.2022.1070068 Case report: Challenges in OPEN ACCESS immune reconstitution EDITED BY Irina A. Tuzankina, Institute of Immunology and following hematopoietic Physiology (RAS), Russia REVIEWED BY stem cell transplantation for Barbara Pia˛tosa, Children’s Memorial Health Institute (IPCZD), Poland CTLA-4 insufficiency-like Sukru Nail Guner, Meram Faculty of Medicine, Turkey primary immune *CORRESPONDENCE Adriana Margarit-Soler amargaritsoler@gmail.com regulatory disorders Laia Alsina laia.alsina@sjd.es Adriana Margarit-Soler 1*, Àngela Deyà-Martı́nez 2,3,4, SPECIALTY SECTION This article was submitted to Juan Torres Canizales 5, Alexandru Vlagea 5, Ana Garcı́a-Garcı́a 2,3,4, Primary Immunodeficiencies, Júlia Marsal 1, Maria Trabazo Del Castillo 1, Sı́lvia Planas 6, a section of the journal Frontiers in Immunology Sı́lvia Simó 7,8, Ana Esteve-Sole 2,3,4, Marı́a Suárez- RECEIVED 14 October 2022 Lledó Grande 9,10,11, Isabel Badell 1,12, Montserrat Rovira Tarrats 1,9,10, 28 November 2022 ACCEPTED PUBLISHED 27 December 2022 Francesc Fernández-Avilés 9,10and Laia Alsina 2,3,4,11* CITATION 1 Bone Marrow Transplant Unit, Oncology Service, Hospital Sant Joan de Déu, Barcelona, Spain, Margarit-Soler A, Deyà-Martı´nez À, Clinical Immunology and Primary Immunodeficiencies Unit, Pediatric Allergy and Clinical 2 Canizales JT, Vlagea A, Garcı´a- Immunology Department, Hospital Sant Joan de Déu, Barcelona, Spain, 3 Study Group for Immune Garcı´a A, Marsal J, Del Castillo MT, Dysfunction Diseases in Children (GEMDIP), Institut de Recerca Sant Joan de Déu, Barcelona, Spain, Planas S, Simó S, Esteve-Sole A, 4 Clinical Immunology Program Hospital Sant Joan de Déu-Hospital Clı´nic Barcelona, Grande MS-L, Badell I, Tarrats MR, Barcelona, Spain, 5 Clinical Immunology Unit, Department of Immunology, Biomedical Diagnostic Fernández-Avilés F and Alsina L (2022) Center, Hospital Clı´nic of Barcelona-Institut d'Investigacions Biomèdiques August Pi i Sunyer Case report: Challenges in immune (IDIBAPS), Barcelona, Spain, 6 Department of Pathology, Hospital Sant Joan de Déu, reconstitution following hematopoietic Barcelona, Spain, 7 Infectious Diseases Unit, Department of Pediatrics, Hospital Sant Joan de Déu, stem cell transplantation for CTLA-4 Barcelona, Spain, 8 Center for Biomedical Network Research on Epidemiology and Public Health insufficiency-like primary immune (CIBERESP), Madrid, Spain, 9 Hematopoietic Transplantation Unit, Hematology Department, Clinical regulatory disorders. Institute of Hematology and Oncology (ICMHO), Hospital Clı´nic de Barcelona, Barcelona, Spain, Front. Immunol. 13:1070068. 10 Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Hospital Clinic, doi: 10.3389/fimmu.2022.1070068 Barcelona, Spain, 11 Department of Surgery and Surgical Specializations, Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain, 12 Pediatric Haematology and Stem COPYRIGHT Cell Transplantation Unit, Pediatric Department, Hospital de la Santa Creu i Sant Pau, Universitat © 2022 Margarit-Soler, Deyà-Martı´nez, Autònoma de Barcelona, Barcelona, Spain Canizales, Vlagea, Garcı´a-Garcı´a, Marsal, Del Castillo, Planas, Simó, Esteve-Sole, Grande, Badell, Tarrats, Fernández- Avilés and Alsina. This is an open-access article distributed under the terms of the Creative Commons Attribution Cytotoxic T-lymphocyte antigen-4 (CTLA-4) haploinsufficiency is a T-cell License (CC BY). The use, distribution hyperactivation disorder that can manifest with both immunodeficiency and or reproduction in other forums is immune dysregulation. Approximately one-third of patients may present mild permitted, provided the original author(s) and the copyright owner(s) symptoms and remain stable under supportive care. The remaining patients are credited and that the original may develop severe multiorgan autoimmunity requiring lifelong publication in this journal is cited, in accordance with accepted academic immunosuppressive treatment. Hematopoietic stem cell transplantation practice. No use, distribution or (HSCT) is potentially curable for patients with treatment-resistant immune reproduction is permitted which does dysregulation. Nevertheless, little experience is reported regarding the not comply with these terms. management of complications post-HSCT. We present case 1 (CTLA-4 haploinsufficiency) and case 2 (CTLA-4 insufficiency-like phenotype) manifesting with severe autoimmunity including cytopenia and involvement Frontiers in Immunology 01 frontiersin.org Margarit-Soler et al. 10.3389/fimmu.2022.1070068 of the central nervous system (CNS), lung, and gut and variable impairment of humoral responses. Both patients underwent HSCT for which the main complications were persistent mixed chimerism, infections, and immune- mediated complications [graft-versus-host disease (GVHD) and nodular lung disease]. Detailed management and outcomes of therapeutic interventions post-HSCT are discussed. Concretely, post-HSCT abatacept and human leukocyte antigen (HLA)-matched sibling donor lymphocyte infusions may be used to increase T-cell donor chimerism with the aim of correcting the immune phenotype of CTLA-4 haploinsufficiency. KEYWORDS CTLA-4, primary immunodeficiency, hematopoietic stem cell transplantation, abatacept, immune reconstitution, chimerism Introduction Detailed clinical observations can provide insight into the challenges of HSCT management in this subgroup of PIRD Regulatory T cell (Treg) defects are conditions included within patients and more so when they are diagnosed worldwide, the category of primary immune regulatory disorders (PIRDs) (1). including Eastern Europe (5), and the HSCT approach can be They are defined by quantitative or qualitative impairment of the variable. Thus, we present case 1 (CTLA-4 haploinsufficiency) Treg compartment, predisposing to severe multiorgan and case 2 (CTLA-4 insufficiency-like phenotype), both autoimmunity with or without susceptibility to infections (2–4). manifested with autoimmune cytopenia, enteropathy, and Cytotoxic T-lymphocyte antigen-4 (CTLA-4) haploinsufficiency is lymphoproliferation, with typical lung and central nervous included in this group, since the reduced surface availability of system (CNS) involvement, and variable impairment of CTLA-4 ultimately results in Treg cell dysfunction (5). The three humoral responses. Both patients underwent HSCT, and the entities that negatively affect CTLA-4 function in human disease are main complications were mixed chimerism, infections, and CTLA-4, lipopolysaccharide-responsive and beige like anchor immune-mediated complications. protein (LRBA), and DEF6 deficiencies (5). These three have been grouped under the term immune checkpoint defects (6). They share common features of dual symptoms of immune dysregulation and Clinical description immune deficiency, with variable disease expressivity even in individuals with the same mutation (5, 7). Shared phenotypic Case 1 manifestations of immune dysregulation include autoimmune cytopenia, enteropathy, and lymphoproliferation (5, 8, 9). This W e p r e s e n t a n 1 8 -y e a r - o l d m a n w i t h C T L A - 4 triad combination is not commonly seen in other PIRDs (5). haploinsufficiency [CTLA4 frameshift mutation c.342_342delC, The long-term therapeutic approach for affected patients is reported in Schwab et al. (8), subject 42] with low CTLA-4 challenging (5, 10). Approximately one-third of patients may expression in FoxP3+ CD4 T cell (Supplementary Figure S1) present mild symptoms and remain stable under supportive care (16). Patient presented autoimmune and/or inflammatory (8). The remaining patients may develop severe multiorgan disorders such as autoimmune hemolytic anemia (AIHA), autoimmunity requiring lifelong immunosuppressive treatment idiopathic thrombocytopenic purpura (ITP), granulomatous- with Treg-sparing immunosuppression [mammalian target of lymphocytic interstitial lung disease (GLILD), and rapamycin (mTOR) inhibitors] or targeted soluble CTLA-4-Ig autoimmune encephalitis, requiring multiple (abatacept, belatacept) (10, 11). Currently, hematopoietic stem cell immunosuppressants as shown in Figure 1. HSCT was transplantation (HSCT) is offered to these patients with treatment- indicated due to partial response of these immune resistant immune dysregulation (1, 12). Nevertheless, little dysregulatory manifestations despite targeted treatment. His experience in HSCT in these conditions is reported (10), mostly immune deficiency and dysregulation activity (IDDA) score in LRBA deficiency (13). Doubts regarding bridge or remission (11) prior to HSCT was 17.6. Main characteristics of his induction therapy (11, 13, 14), conditioning for the transplant (15), baseline disease and HSCT are presented in Table 1. The and post-HSCT chimerism goals remain. patient received HSCT from his identical human leukocyte Frontiers in Immunology 02 frontiersin.org Margarit-Soler et al. 10.3389/fimmu.2022.1070068 A B FIGURE 1 (A) Timeline of case 1. (B) Timeline of case 2. Steroids; AIHA, autoimmune hemolytic anemia; ITP, immune thrombocytopenic purpura; AI, autoimmune; HSCT, hematopoietic stem cell transplantation; CMV, cytomegalovirus; MC, myeloid chimerism; LC, lymphoid chimerism; CSA, cyclosporin; DLI, donor lymphocyte infusion; GLILD, granulomatous-lymphocytic interstitial lung disease; RTX, rituximab; IgRT, immunoglobulin replacement therapy; IBD, inflammatory bowel disease; GVHD, graft-versus-host disease. antigen (HLA) sister, both sharing blood type and positivity for completed with brain magnetic resonance imaging, positron cytomegalovirus (CMV). The European Group for Blood and emission tomography (PET) scan, bronchoalveolar lavage Marrow Transplantation (EBMT) guidelines were followed for (BAL), and bone marrow aspirate. Multiple adenopathies and HSCT using treosulfan, fludarabine, and thiotepa as splenomegaly were seen. Bone marrow aspirate was normal. conditioning treatment and cyclosporin and mycophenolate Epstein–Barr virus (EBV) was positive in blood and in the BAL, for graft-versus-host disease (GVHD) prophylaxis (17). The although at a very low number of copies (<250 copies/ml), and clinical course was complicated with low donor lymphoid the patient did not present other signs of posttransplant chimerism and an episode of lung lesions that posed the lymphoproliferative disorder (PTLD). differential diagnosis with GLILD. Both resolved with the A lung wedge biopsy was performed, demonstrating non- combination of donor lymphocyte infusions (DLIs) from the necrotizing granulomatous inflammation concentrated identical HLA sister and expert management of immune bronchovasculocentrically and paraseptally, made up of modulation including abatacept introduction post-HSCT, as histiocytes admixed with a lymphocytic component, described below. The timeline is depicted in Figure 1. predominantly T-cell CD4+. Microbiological tests ruled out Three months post-procedure, split chimerism showed infection. These findings were suggestive of a GLILD flare myeloid lineage of 89% and lymphoid lineage of 18% from the (18). To confirm which T cells (female donor vs. male patient) donor. In order to improve the chimerism, cyclosporin was were driving this inflammation, fluorescence in situ quickly withdrawn over 4 weeks and abatacept as a target hybridization (FISH) X/Y was performed in the lung tissue to therapy was started to control the dysregulated lymphocytes assess the chimerism in situ. The same pattern as in the blood that could be left from the recipient. Three weeks later, (Figure 2) was observed, ruling out enrichment of the patient’s T chimerism remained very low in the lymphoid lineage (18%); cells in the granulomas. Lung lesions presented remission within therefore, the patient received three DLIs (total dose CD3 1.3 × 2 weeks without further intervention. The patient remained on 108) from his sister with no signs of GVHD after that. Seven abatacept as the sole immunosuppression. months after transplant, 3 months after stopping cyclosporin Fifteen months post-HSCT, the patient presented good and switching to abatacept, and 1.5 months after DLI, chimerism clinical evolution with an improvement in the CT scan and improved, showing 92% of myeloid and 49% of lymphoid from respiratory test. Chimerism presented sustained improvement, the donor. maintaining 100% and >95% in myeloid and lymphoid lineages, Eight months after transplantation, the patient presented respectively. In this context, abatacept was discontinued. fever and diarrhea. Infectious screening was positive for Currently, 21 months posttransplantation, CT scan and Campylobacter coli in a stool culture. After 5 days of fever and pulmonary function tests are within normal range and the on antibiotics, computed tomography (CT) scan showed patient’s chimerism is 100% in both lineages. He is off m u l t i p l e l u n g n o d ul e s s u g g e s t i n g a n i n f e c t i o n o r immunosuppression with good immune reconstitution and lymphoproliferative disorder (Figure 2). The study was also off immunoglobulin replacement therapy (IgRT) (Table 1). Frontiers in Immunology 03 frontiersin.org Margarit-Soler et al. 10.3389/fimmu.2022.1070068 TABLE 1 Table 1 Summary of the two cases. Case 1-♂ Case 2-♂ Pre-HSCT \ Age at disease onset (years) 6 15 Age at CVID diagnosis (years) 10 15 Positive genetic diagnosis CTLA4 frameshift mutation c.342_342delC (13 years old) No Immune workup at CVID diagnosis Absolute lymphocytes (cells/mm3) 1,100 (low) 1,200 (low) CD19+ lymphocytes (%/abs) 13.9/153 (normal/normal) 11/132 (low/low) CD4+ lymphocytes (%/abs) 43.9/473 (normal/normal) 32/384 (normal/low) CD8+ lymphocytes (%/abs) 30.8/339 (normal/normal) 31/372 (normal/ normal) CD19+ naive (IgM+IgD+CD27-) (%, abs) 97.3/149 (high/ normal) 78/102 (normal/normal) CD19+ switched memory (IgD-CD27+)(%, 0.5/1 (low/low) 12/16 (normal/low) abs) CD19+CD21lowCD38low (%,abs) Not determined 22.8/30 (high/normal) Naive CD3+CD45RA+ (%) 54 (normal) 35.9 (normal) Memory CD3+CD45RO+ (%) 31 (normal) 37.9 (normal) IgG (mg/dl) 588 (low) 576 (low) IgA (mg/dl) 18 (low) 44 (low) IgM (mg/dl) 43 (normal) 34 (low) Immune workup before HSCT Absolute lymphocytes (cells/mm3) 900 (low) 700 (low) CD19+ lymphocytes (%/abs) 22.3/200 (normal/normal) 0/0 (under RTX. low/low) CD4+ lymphocytes (%/abs) 43.9/395 (normal/normal) 25.4/177 (low/low) CD8+ lymphocytes (%/abs) 23.5/211 (normal/normal) 44/308 (high/normal) CD19+ naive (IgM+IgD+CCD27-) (%/abs) 98.5/97 (high/ normal) NA CD19+ switched memory (IgD-CD27+) 0.4/0.8 (low/low) NA (%/abs) CD19+CD21low CD38low (%) 3.5 (normal) NA Naive CD4+ (CD4+ CD45RA+) (%) 52.9 (normal) 17.5 (low) Eff.mem.CD4+(CD4+CD45RA-CCR7-) (%) 6.6 (normal) 55.4 (high) Naive CD8+ (CD8+ CD45RA+) (%) 68 (normal) 10.8 (low) Eff. mem.CD8+ (CD8+CD45RA-CCR7-)(%) 16.3 (normal) 75.5 (high) IgG (mg/dl) 882 (normal, under IgRT) 1,381 (normal, under IgRT) IgA (mg/dl) 12 (low) 24 (low) IgM (mg/dl) 34 (low) 24 (low) IgRT Yes Yes Infections CMV chronic infection Periorbital infection Recurrent enteric infections (Campylobacter spp. and Salmonella spp.) Immune-dysregulatory phenotype Evans syndrome Immune thrombocytopenia Granulomatous-lymphocytic lung disease Granulomatous-lymphocytic lung disease Autoimmune encephalomyelitis Autoimmune encephalomyelitis Lymphoproliferation (splenomegaly, adenomegalies) Inflammatory bowel disease Lymphoproliferation (splenomegaly) Immunosuppressants prior to HSCT (see Steroids, mycophenolate, sirolimus, rituximab, abatacept Steroids, mycophenolate, sirolimus, rituximab, Figure 1) abatacept IDDA score 17.6 21.6 (Continued) Frontiers in Immunology 04 frontiersin.org Margarit-Soler et al. 10.3389/fimmu.2022.1070068 TABLE 1 Continued Case 1-♂ Case 2-♂ Post-HSCT Age at HSCT (years) 18 21 Karnofsky 100% 90% Conditioning regimen Flu-Treo-Thio Flu-Treo-Thio GVHD prophylaxis Alemtuzumab, CSA, MMF Alemtuzumab, CSA, MMF Type of donor BM-identical HLA MSD BM-10/10 HLA MUD TNC 2.3 × 10e8/kg TNC 1.63 × 10e8/kg Graft failure No No Slow engraftment at day 28 Yes Yes Infections CMV, Herpes simplex CMV, ADV, BK , SARS-CoV-2 GVHD No Yes, acute (CSA switched to sirolimus due to renal disease) Mixed chimerism 3 months post-HSCT Yes Yes (both lineages) Interventions for mixed chimerism Switch CSA to abatacept No DLI Off IS 14 m post-HSCT (abatacept) 17 m post-HSCT (sirolimus) Off IgRT Yes, since 6 m post-HSCT No Immune workup 21 m post-HSCT Absolute lymphocytes (cells/mm3) 2,500 (normal) 800 (low) CD19+ lymphocytes (%/abs) 27/675 (high/high) 4.9/19 (low/low) CD4+ lymphocytes (%/abs) 25/628 (low/normal) 25/100 (low/low) CD8+ lymphocytes (%/abs) 36/900 (high/normal) 56/222 (high/low) NK cells/mm3 (%/abs) 8/200 (normal/normal) 8.2/32 (normal/low) Naive CD4+ (CD4+ CD45RA+) (%/abs) 47.9/300.8 (normal/normal) 30.2/30.2 (low/low) Eff.mem.CD4+(CD4+CD45RA-CCR7-)(%/abs) 26.8/168.3 (normal/normal) 40.1/40.1 (normal/low) Naive CD8+ (CD8+ CD45RA+) (%/abs) 21.1/189.9 (normal/normal) 13.7/30.4 (low/low) Eff.mem.CD8+ (CD8+CD45RA-CCR7-) 2.9/26.1 (low/low) 35.4/78.58 (normal/low) (%/abs) CD19+ naive (%/ abs) 97.2/656.1 (high/high) 97.4/18.5 (high/low) CD19+ switched memory (IgD –CD27+) 1.6/10.8 (low/low) 1/0.0 (low/low) (%/abs) IgG (mg/dl) 1,497 (normal) 870 (normal, under IgRT) IgA (mg/dl) <3 (low) <3 (low) IgM (mg/dl) 137 (normal) 19 (low) HSCT, hematopoietic stem cell transplantation; m, months; CVID, common variable immunodeficiency; NA, not applicable; Eff.mem., effector memory; IgRT, immunoglobulin replacement therapy; CMV, cytomegalovirus; IDDA, immune deficiency and dysregulation activity (ref 12); yo, years old; Flu, fludarabine; Treo, treosulfan; Thio, thiotepa; GVHD, graft- versus-host disease; CSA, cyclosporin; MMF, mycophenolate; BM, bone marrow; HLA, human leukocyte antigen; MSD, matched sibling donor; MUD, matched unrelated donor; TNC, total nucleated cell dose; ADV, adenovirus; DLI, donor lymphocyte infusion; IS, immunosuppressant; RTX, rituximab; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2. Case 2 Constitutional Panel 17 Mb, Agilent), and an array comparative genomic hybridization (aCGH) was normal. The We present a 21-year-old man with common variable patient fulfilled the European Society for Immunodeficiencies immunodeficiency (CVID) and a phenotype of immune (ESID) Registry Working Definitions for the Clinical Diagnosis dysregulation similar to CTLA-4 haploinsufficiency for Common Variable Immunodeficiency (19) (Table 1). characterized by autoimmune cytopenia, inflammatory bowel However, CTLA-4 expression in FoxP3+ CD4+ T cells disease (IBD), lymphoproliferation (GLILD), autoimmune resembled that of CTLA-4-deficient patients, with a marked encephalitis, and humoral deficiency requiring multiple decrease in the CTLA-4hiFoxP3+CD4+ T cells (Supplementary immunosuppressants (Figure 1). No genetic defect was Figure S1). HSCT was indicated due to a partial control of identified in a gene panel including inborn errors of immunity immune dysregulation despite sirolimus and abatacept. The (IEIs) and PIRD-related genes (SureSelect Custom IDDA score prior to HSCT was 21.6. The patient received Frontiers in Immunology 05 frontiersin.org Margarit-Soler et al. 10.3389/fimmu.2022.1070068 FIGURE 2 Study of lung lesions of case 1. First image computed tomography (CT) scan showing multiple lung nodules. Second image wedge luyng biopsy demonstrated a non-necrotizing granulomatous inflammation concentrated bronchovasculocentrically and paraseptally [hematoxylin and eosin (H&E), 2x]. Third image fluorescencein-situ hybridization (FISH) using locus specific indentifier (LSI) SRY. In the lymphocytic infiltrates, up to 27% of the nuclei showed a green dot (CEP X) and a red dot (SRY), and 73% of the nuclei showed two green dots (CEP X), thus indicating that the majority of the lymphocytic infiltrate corresponded to the female donor. HSCT from an HLA-identical (10/10) unrelated donor with the 14), transplant conditioning (15), and post-HSCT chimerism same blood type. The patient was CMV-positive, while the goals need to be refined. The two cases reported here are donor was negative. The clinical course was complicated by representative of this group of patients who fail to respond to GVHD, mixed chimerism, and infectious episodes, as described conservative immunosuppressant treatment and move to HSCT below. The timeline is depicted in Figure 1. with high levels of immune dysregulation. Their post-HSCT One month post-HSCT, he developed grade 2 GVHD outcome and management highlight the importance of an requiring steroids and poor engraftment requiring granulocyte individualized approach to achieve maximum, if not full, colony-stimulating factor and eltrombopag. He also presented lymphoid chimerism to ensure disease remission and complete CMV infection requiring preemptive treatment with foscarnet, immune reconstitution. cidofovir, and specific T-lymphocyte infusion. Thereafter, CMV Over the last decade, allo-HSCT outcomes in IEI have improved infection was controlled, but he developed BK hemorrhagic significantly. The survival rate for conventional IEI transplants is now cystitis, community-acquired pneumonia, and a severe acute approaching 90% (17, 20, 21). HSCT is also being offered to young respiratory syndrome coronavirus 2 (SARS-CoV-2) upper adults with high rates of success (22). This is due to improved donor respiratory tract infection. selection, better management of HSCT complications, and optimized Mixed chimerism persisted around 60%–70% in the supportive care (20, 23, 24). Still, high levels of hyperinflammation lymphocytic lineage (Figure 1). Cyclosporin was switched to prior to transplant may promote a greater incidence of alloreactivity sirolimus for the treatment of GVHD at 8 months post-HSCT disorders post-HSCT (25, 26), and has already been shown to worsen due to renal dysfunction. Lymphoid chimerism remained in HSCT outcomes, with a greater risk of GVHD (as observed in case 2) similar range, with a slight increase to 75%. At 17 months post- and toxicity, and impaired immune reconstitution (25). Also, HSCT, with controlled GVHD, immunosuppression was slowly although the same conditioning and GVHD prophylaxis were discontinued with no complications. As the patient maintained a given in both cases, they received different types of graft: case 1 stable lymphoid chimerism above 70%–75% and persistent received marrow from his HLA-identical sister and case 2 received grade 2 GVHD, no further interventions were performed. marrow from a 10/10 HLA unrelated donor. Still, some immune Currently, 21 months post-HSCT, the patient is off disparities could be present and interfere in the immune immunosuppression. He still presents mixed donor chimerism reconstitution phase, as described before (25, 27). In addition, of 34% in granulocytes and 75% in T lymphocytes without patient 2 presented a higher IDDA score and higher number of autoimmune episodes. His immune cellular and humoral effector memory CD4+ cells prior to HSCT. All these factors may reconstitution is still incomplete, requiring IgRT and have contributed to the different post-HSCT outcome in antimicrobial prophylaxis (Table 1). both patients. In our cases, HLA-matched donors (one related, one unrelated) and bone marrow source were used. In this sense, it is important to Discussion bear in mind that because of the genetic nature of most IEIs, genetic screening of family donors is warranted regardless of symptoms, Currently, the management of CTLA-4 haploinsufficiency since PIRDs can display a late or variable clinical onset, as typically and similar diseases characterized by marked T-cell activation is described for CTLA-4 haploinsufficiency (8). In order to minimize still in discussion. Bridge or remission induction therapy (11, 13, the higher incidence of alloreactivity, the role of biologic modifiers or Frontiers in Immunology 06 frontiersin.org Margarit-Soler et al. 10.3389/fimmu.2022.1070068 targeted therapies as a bridge to HSCT in PIRDs is an important field More and more adolescents and young adults (AYAs) with IEI to explore (14). In our center, both patients received targeted are referred for HSCT (22, 34, 35). For these patients, aging leads to immunosuppression including abatacept until 2 weeks prior to early end organ damage, reduced quality of life, and early death transplantation. Currently, one of the main questions that arise is (36). Transplant decision is challenging, as they have survived the dichotomy between lifelong immune modulation vs. HSCT for childhood with conservative management, but HSCT needs to be IEI and PIRD (28). considered before further deterioration. Both of our reported Current recommendations do not identify patients with CTLA-4 patients have received adult-stage HSCT with reduced toxicity haploinsufficiency who might benefit from long-term targeted regimen, and the decision to transplant was based on the lack of immunomodulation vs. HSCT nor the optimal timing for HSCT disease control despite long-term use of two targeted (10). HSCT outcomes must be balanced with the risks of disease. immunomodulators. For newly identified diseases with alternative Reports of HSCT for CTLA-4 haploinsufficiency are scarce. They targeted therapies (14, 37–39) such as CTLA-4 fusion proteins, illustrate that HSCT can be effective (8, 29). Schwab et al. (8) reported careful follow-up of different treatment cohorts is necessary to 12 transplanted patients among 90 symptomatic CTLA4 mutation determine the best treatment modalities in the long-term. The safety carriers undergoing allo-HSCT between 10 and 50 years of age. Main and efficacy of abatacept for adult patients with CTLA-4 indications were uncontrollable cytopenia, enteropathy, and insufficiency or LRBA deficiency are currently being evaluated in lymphoma with additional autoimmune disorders involving a phase 2 clinical trial (ABACHAI) (40). lymphoproliferative and infectious complications (8). Nine of the For some IEIs, a certain level of mixed chimerism is sufficient to 12 patients (75%) are alive, three of them more than 5 years after improve the patients’ well-being. But is there a minimum level of HSCT and currently well without medication. Slatter et al. (29) donor T-cell chimerism required to correct the immune phenotype described eight pediatric patients with CTLA-4 haploinsufficiency of PIRD whose immune pathology is T-cell activation? Chimerism who underwent HSCT. All received transplants from 10/10 HLA- was designed to monitor the percentage of the donor cells after the matched unrelated donors following a reduced-intensity infusion and not to monitor the disease baseline or malignant relapse conditioning regimen; the outcome was 50% GVHD, 25% (41). Full donor T-cell chimerism in LRBA deficiency has been autoimmune disorders, and an overall survival rate of 75% (29). In shown to be positively linked to the probability of remission, although the report by Chan et al. (24), 13 of the 226 transplanted patients were data on the relevance of donor chimerism for cure are still limited (11, CTLA-4 haploinsufficiencies, but no specific subgroup data analysis 13, 42, 43). In many IEIs, stable mixed donor chimerism does not lead could be performed. The informed nature of decision-making for to graft rejection, and it may suffice to correct the underlying clinicians, patients, and families in these ill-defined situations is immunodeficiency (44). However, it has been shown that donor improved if clinical outcome data of defined patients with defined myeloid chimerism is important for long-term immune recovery of T treatments are reported. For this purpose, a systematic description of and B lymphocytes and adequate immune function after HSCT (45). patients with CTLA-4 haploinsufficiency undergoing HSCT is In case 2, low mixed myeloid chimerism was a concern, although no needed. This description should include IDDA score prior to DLIs were considered due to the high risk of GVHD and to donor HSCT. The IDDA score (11) can be used to compare availability. Some data suggest that mixed chimerism can cause semiquantitative values in one individual over time (clinical course, persistent autoimmunity or autoinflammation in these patients longitudinally) or between individuals or cohorts at a specific time (46–48). From the report by Slatter et al. (29), six of the eight point (cross-sectionally). The new IDDA version includes broader patients are alive and well with donor chimerism ranging 85%– manifestations of immune dysregulation, factors that indicate the 100%. So, for patients with CTLA-4 haploinsufficiency who present quality of life and need for supportive care, and the occurrence of mixed chimerism post-HSCT, it seems reasonable to aim at high, or malignancies (30). This is critical because the absence of ongoing even full, T-cell chimerism. In cases of no active GVHD, like in case 1, medication and quality of life are important features that are rarely weaning from the immunosuppressant drugs and performing DLI, quantified, and these may be better in patients who have undergone especially in matched family donors, could be considered. In case 1, transplantation (31–33). Also, a detailed description of abatacept was also started to immunomodulate the patient’s CTLA-4 immunosuppressants used prior to and post-HSCT and the haploinsufficient lymphocytes. The use of abatacept prior to HSCT is dynamics of T-cell chimerism are necessary to enable comparisons to modulate autologous activated T cells to control the underlying of therapeutic approaches. In our patients, disease evolution prior to disease. Its use in the posttransplant phase could be beneficial both in HSCT was 12 and 6 years, respectively; the patients had a high disease controlling the remaining autologous T cells to reduce the risk of burden with IDDA scores >15 and had received multiple courses of disease flare, but also to modulate allo-reactive donor T cells to reduce immunosuppressants with only partial or transient responses. the risk of GVHD development (49, 50). On the other hand, if the Despite the non-compelling abovementioned HSCT data, the patient presents GVHD, such as case 2, the approach to slowly transplant choice was made by the patients, mainly motivated by withdraw the immunosuppressant drug, or even switch to a Treg- chronic disease fatigue and the low quality of life of two active sparing regimen such as sirolimus, can be considered. It is difficult to young adults. ascertain what the main reasons are for such a different outcome. Our Frontiers in Immunology 07 frontiersin.org Margarit-Soler et al. 10.3389/fimmu.2022.1070068 hypothesis is that GVHD development in case 2 [linked to a matched Data availability statement unrelated donor (MUD) and higher levels of inflammation at the time of HSCT] was one of the main determinants in the different The original contributions presented in the study are management of mixed chimerism and final outcome, since it obliged included in the article/Supplementary Material. Further to a certain level of immunosuppression and interfered with inquiries can be directed to the corresponding authors. immune reconstitution. Beyond chimerism, during the early phase of PIRD patient transplant, the recipient’s dysregulated lymphocytes are still a Ethics statement concern, especially in mixed chimerism. Therefore, close monitoring of inflammation and autoimmune complications is Written informed consent was obtained from the crucial for early flare recognition until chimerism and immune individual(s) for the publication of any potentially identifiable reconstitution are complete. In case 1, it is difficult to determine images or data included in this article. whether the lung nodular lesions were a flare of his GLILD in the context of persistent low chimerism and his being off abatacept (no infection or PTLD was demonstrated, and he was respiratory asymptomatic so suspicion of an immune reconstitution Author contributions phenomenon was reduced). Also, no CT had been performed in the first 8 months post-HSCT to enable comparisons. The AM-S and ÀD-M: These authors share first authorship; AM- predominance of donor T cells in the nodules along with the S, ÀD-M, and JT: These authors contributed equally to this improved chimerism thereafter might explain the quick resolution work; FF-A and LA: These authors share last authorship. All of the lung nodules in a GLILD. In patient 2, currently with 75% of authors contributed to manuscript revision, read, and approved lymphoid chimerism, no disease flare has been observed while off the submitted version. immunosuppression. Immunological biomarkers are still to be defined in the monitoring of PIRD patients’ immune reconstitution and detection of immune dysregulation post- Funding HSCT. Functional studies on the underlying genetic defect (i.e., transendocytosis test for checkpoint deficiencies) might be of This study was supported by the projects PI18/00223, FI19/ interest in cases of persistent mixed lymphoid chimerism (6, 8, 51). 00208 and PI21/00211 of LA, integrated in the Plan Nacional de I+D+I and cofinanced by the ISCIII – Subdirecció n General de Evaluació n y Fomento de la Investigació n Sanitaria – and Conclusion the Fondo Europeo de Desarrollo Regional (FEDER), by Pla Estratègic de Recerca i Innovació en Salut (PERIS), CTLA-4 haploinsufficiency encompasses a heterogeneous and Departament de Salut, Generalitat de Catalunya (SLT006/17/ often complex group of patients requiring an individualized 00199 to LA), by a 2017 Leonardo Grant for Researchers therapeutic approach. Detailed descriptions of case reports and and Cultural Creators, BBVA Foundation (IN[17] HSCT outcomes are crucial to identify strategies to improve allo- _BBM_CLI_0357) to LA, by a 2017 Beca de Investigació n de HSCT outcomes and help delimit the target T-cell chimerism and la Sociedad Española De Inmunologı́a Clı́nica Alergologı́a y thereby avoid disease flares. These strategies may include the use of Asma Pediá trica to LA, and by a 2022 Convocatòria de Beques targeted immunomodulators not only prior to but also post-HSCT. de Recerca IRSJD – Carmen de Torres 2022 to LA (2022AR- Furthermore, we need to define post-HSCT-specific monitoring and IRSJD-CdTorres) and CERCA Programme/Generalitat evaluate improvements of disease burden with specific scores. All of de Catalunya. the foregoing is necessary to enrich the informed nature of the decision-making in lifelong management of children and adults with these diseases. Acknowledgments The authors gratefully acknowledge all team members, Patient perspective and informed especially the nursery team, who dedicate their best efforts to consent taking care of transplant patients. In addition, we would like to thank Eva Rodriguez Nunez, Biomedical Scientist from the Written informed consent was obtained from the individuals Anatomical Pathology Department. We also would like to for the publication of any potentially identifiable images or data thank both patients for allowing the publication of their included in this article. case details. Frontiers in Immunology 08 frontiersin.org Margarit-Soler et al. 10.3389/fimmu.2022.1070068 Conflict of interest organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or The authors declare that the research was conducted in the claim that may be made by its manufacturer, is not guaranteed absence of any commercial or financial relationships that could or endorsed by the publisher. be construed as a potential conflict of interest. Supplementary material Publisher’s note The Supplementary Material for this article can be found All claims expressed in this article are solely those of the online at: https://www.frontiersin.org/articles/10.3389/ authors and do not necessarily represent those of their affiliated fimmu.2022.1070068/full#supplementary-material References 1. Chan AY, Torgerson TR. Primary immune regulatory disorders: A growing regulatory T cells. Pediatr Allergy Immunol (2018) 29(4):425–32. doi: 10.1111/ universe of immune dysregulation. Curr Opin Allergy Clin Immunol (2020) 20 pai.12890 (6):582–90. doi: 10.1097/ACI.0000000000000689 17. 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