ESC HEART FAILURE ORIGINAL RESEARCH ARTICLE ESC Heart Failure 2019; 6: 388–395 Published online 23 January 2019 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/ehf2.12406 Determination of HLA-A, -B, -C, -DRB1 and -DQB1 allele and haplotype frequencies in heart failure patients Santiago Roura1,2†, Francesc Rudilla3,4†, Paloma Gastelurrutia1,2, Emma Enrich3,4, Eva Campos3, Josep Lupón2,5,6, Evelyn Santiago-Vacas5, Sergi Querol4,7* and Antoni Bayés-Genís1,2,5,6* 1 ICREC Research Program, Germans Trias i Pujol Health Science Research Institute, Badalona, Spain; 2CIBER Cardiovascular, Instituto de Salud Carlos III, Madrid, Spain; 3 Histocompatibility and Immunogenetics Laboratory, Blood and Tissue Bank, Barcelona, Spain; 4Transfusional Medicine Group, Vall d’Hebron Research Institute, Autonomous University of Barcelona (UAB), Barcelona, Spain; 5Cardiology Service, Germans Trias i Pujol University Hospital, Badalona, Spain; 6Department of Medicine, UAB, Barcelona, Spain; 7Cell Therapy Unit, Blood and Tissue Bank, Barcelona, Spain Abstract Aims Cell therapy can be used to repair functionally impaired organs and tissues in humans. Although autologous cells have an immunological advantage, it is difficult to obtain high cell numbers for therapy. Well-characterized banks of cells with hu- man leukocyte antigens (HLA) that are representative of a given population are thus needed. The present study investigates the HLA allele and haplotype frequencies in a cohort of heart failure (HF) patients. Methods and results We carried out the HLA typing and the allele and haplotype frequency analysis in 247 ambulatory HF patients. We determined HLA class I (A, B, and C) and class II (DRB1 and DQB1) using next-generation sequencing technology. The allele frequencies were obtained using Python for Population Genomics (PyPop) software, and HLA haplotypes were es- timated using HaploStats. A total of 30 HLA-A, 56 HLA-B, 23 HLA-C, 36 HLA-DRB1, and 15 HLA-DQB1 distinct alleles were iden- tified within the studied cohort. The genotype frequencies of all five HLA loci were in Hardy–Weinberg equilibrium. We detected differences in HLA allele frequencies among patients when the etiological cause of HF was considered. There were a total of 494 five-loci haplotypes, five of which were present six or more times. Moreover, the most common estimated HLA haplotype was HLA-A*01:01, HLA-B*08:01, HLA-C*07:01, HLA-DRB1*03:01, and HLA-DQB1*02:01 (6.07% haplotype fre- quency per patient). Remarkably, the 11 most frequent haplotypes would cover 31.17% of the patients of the cohort in need of allogeneic cell therapy. Conclusions Our findings could be useful for improving allogeneic cell administration outcomes without concomitant immunosuppression. Keywords Allogeneic cell therapy; Allele frequency; Haplotype frequency; Heart failure Received: 27 June 2018; Accepted: 12 December 2018 *Correspondence to: Antoni Bayés-Genís, MD, PhD, FESC, FHFA, Head, Heart Institute, Hospital Universitari Germans Trias i Pujol, and Department of Medicine, UAB, Carretera del Canyet s/n 08916 Badalona, Spain. Tel: +34 934978915; Fax: +34 934978939. Email: abayesgenis@gmail.com Sergio Querol, MD, PhD, Head of Cell Therapy Services, Catalan Blood and Tissue Bank (BST), Frederic Duran i Jordà Center, Barcelona, Spain. Tel: +34 935573505; Fax: +34 935573506. Email: squerol@bst.cat †These authors contributed equally to the present work. Introduction patient survival and comorbidities, replacement of the irrep- arably injured heart by a donor organ is the only option in Heart failure (HF) is recognized as the true epidemic of the some cases. However, this is often impaired by limited do- 21st century, affecting 1–2% of the adult population in devel- nors, organ rejection, and receptors that need chronic immu- oped countries, with a prevalence of ≥10% among those aged nosuppression, which greatly reduces the patient’s quality of 70 years and older.1 Despite effective medication, left ven- life.2 In this context, cell-based therapy constitutes a promis- tricular assist devices, and surgeries that have improved ing option to restore damaged heart tissue.3,4 Autologous cell © 2019 The Authors. ESC Heart Failure published by John Wiley & Sons Ltd on behalf of the European Society of Cardiology. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any me- dium, provided the original work is properly cited and is not used for commercial purposes. HLA haplotypes in heart failure patients 389 transplantation is preferred for regenerative purposes be- Table 1 Baseline demographic, clinical, and biochemical data of the study participants cause there is no risk of immune rejection. However, the use of autologous cells has some potential limitations. In gen- n = 247 eral, high cell numbers are not immediately available from Age (years) 68.7 ± 12.2 the same recipient. Moreover, cells isolated from elderly do- Male sex 209 (84.6%) Aetiology nors show decreased differentiation and regenerative capa- Ischaemic heart disease 152 (61.5%) bilities, resulting in disappointing treatment outcomes. To Dilated CM 42 (17%) overcome these limitations, therapeutic strategies are using Hypertensive CM 9 (3.6%) Alcoholic CM 12 (4.9%) allogeneic cells despite the need for human leukocyte antigen Drug-induced CM 4 (1.6%) (HLA) matching between the donor and recipient. Valvular disease 13 (5.3) Histocompatibility is mainly determined by the major his- Hypertrophic CM 5 (2.0%) Other 10 (4%) tocompatibility complex genes (termed HLA in humans), the HF duration (months) 60 (14–119) most polymorphic genes in the human genome, which are lo- LVEF 29.5% ± 6.5 cated on a 3.6 Mb region on chromosome 6p21. The HLA NYHA functional class I 8 (3.2%) genes have important roles in immune system regulation.5–7 II 156 (63.2%) Mainly, the HLA molecules present antigens to T lymphocytes III 81 (32.8%) that direct the immune response and prevent autoreactivity. IV 2 (0.8%) Co-morbidities It is important to note that the immune response against HLA Hypertension 182 (73.7%) antigens is a major obstacle in organ and haematopoietic Diabetes mellitus 112 (45.3%) stem cell transplantation. Currently, HLA typing is used to COPD 71 (28.7%) Renal failurea 146 (59.1%) search for an adult HLA match or cord blood donors to pre- Anaemiab 116 (47%) vent graft-versus-host disease and graft rejection during Atrial fibrillation/flutter 100 (40.5%) transplantation.8–12 Thus, to increase the success of the func- Biochemical Na 139 ± 3.9 tional engraftment of a variety of cell suspensions or cell- Haemoglobin 12.9 ± 1.6 embedded implants, there is a need for ready-to-use banks eGFR 55.5 ± 25.2 of HLA homozygous stem cells covering the largest number NTproBNP 1673 (702–4115) Treatments of HLA combinations. ACEI/ARB 207 (83.8%) In this field of study, next-generation sequencing (NGS) ap- Beta-blockers 234 (94.7%) proaches are based on amplification of the selected regions MRA 171 (69.2%) Loop diuretics 214 (86.6%) by PCR followed by massively parallel sequencing of the Digoxin 70 (28.3%) amplicons. In recent years, different HLA typing strategies Ivabradine 38 (15.4%) by NGS have been developed that provide high throughput Statins 199 (80.6%) ICD 83 (33.6%) sequencing, unambiguous high-resolution results, and re- CRT 51 (20.6%) duced costs per sample.13–16 Thus, the aim of this study was to perform a high- ACEI, angiotensin-converting enzyme inhibitor; ARB, angiotensin receptor blocker; CM, cardiomyopathy; CRT, cardiac resolution exploratory HLA analysis in a cohort of patients resynchronization therapy; ICD, implantable cardioverter device; with HF to determine the HLA-A, -B, -C, -DRB1, and -DQB1 LVEF, left ventricular ejection fraction; MRA: mineral corticoid re- allele and haplotype frequencies by NGS and develop conve- ceptor antagonist; NYHA, New York Heart Association. Data expressed as mean ± standard deviation, median (25th–75th niently designed donor panels. These data should maximize percentiles), or absolute number (percentage). 2 the match probabilities for this patient population and a eGFR (CKD-EPI) <60 mL/min/1.73 m . improve potential allogeneic cell therapy outcomes. b Hb < 12 g/dL in women and <13 g/dL in men. to participation. The study protocol was approved by the Clin- Methods ical Research Ethics Committee of our institution (reference number PI-17-044) and was designed in accordance with Study population the principles outlined in the 2013 revision of the Declaration of Helsinki of 1975.19 Patients provide specific ancestry data. Our study cohort included 247 ambulatory patients who attended a multidisciplinary HF unit (Table 1). The referral in- clusion criteria are described elsewhere.17,18 All patients Blood extraction and processing attended follow-up visits at regular predefined intervals and additional visits when required in cases of decompensation. Blood samples (~3 mL) were collected into EDTA tubes via Each subject provided their written informed consent prior standard forearm venipuncture performed between 9:00 a.m. ESC Heart Failure 2019; 6: 388–395 DOI: 10.1002/ehf2.12406 390 S. Roura et al. and 11:00 a.m. and were processed within 4 h after collec- of Catalonia. All laboratory measurements were performed tion. Samples and data from patients included in this study by staff blinded to the patients’ clinical characteristics. DNA were processed and collected by the IGTP-HUGTP Biobank was extracted from peripheral blood using the QIAsymphony from the Spanish National Biobanks Network of Instituto de DNA purification system (Qiagen, Toronto, Canada) according Salud Carlos III (PT13/0010/0009) and Tumour Bank Network to the manufacturer’s protocol. Table 2 Class I allele frequencies in heart failure patients HLA-A N AF HLA-B N AF HLA-C N AF A*02:01 119 24.09 B*44:03 46 9.31 C*07:01 66 13.36 A*01:01 66 13.36 B*18:01 37 7.49 C*04:01 64 12.96 A*24:02 50 10.12 B*44:02 36 7.29 C*05:01 58 11.74 A*03:01 46 9.31 B*08:01 31 6.28 C*06:02 47 9.51 A*29:02 35 7.09 B*51:01 31 6.28 C*16:01 38 7.69 A*11:01 31 6.28 B*07:02 27 5.47 C*07:02 33 6.68 A*26:01 19 3.85 B*14:02 21 4.25 C*12:03 32 6.48 A*30:02 15 3.04 B*38:01 18 3.64 C*08:02 24 4.86 A*32:01 14 2.83 B*35:01 18 3.64 C*01:02 22 4.45 A*31:01 12 2.43 B*50:01 17 3.44 C*02:02 21 4.25 A*23:01 10 2.02 B*15:01 16 3.24 C*03:03 17 3.44 A*68:01 9 1.82 B*57:01 14 2.83 C*15:02 14 2.83 A*33:01 8 1.62 B*49:01 14 2.83 C*03:04 14 2.83 A*68:02 8 1.62 B*45:01 13 2.63 C*12:02 9 1.82 A*25:01 8 1.62 B*27:05 12 2.43 C*14:02 7 1.42 A*30:01 8 1.62 B*40:01 11 2.23 C*17:01 7 1.42 A*02:05 7 1.42 B*52:01 10 2.02 C*15:05 6 1.21 A*33:03 5 1.01 B*35:03 10 2.02 C*03:02 3 0.61 A*66:01 5 1.01 B*53:01 9 1.82 C*05:09 3 0.61 A*03:02 4 0.81 B*40:02 7 1.42 C*02:10 3 0.61 A*02:02 3 0.61 B*37:01 7 1.42 C*07:04 3 0.61 A*69:01 3 0.61 B*39:01 7 1.42 C*16:02 2 0.40 A*24:03 2 0.40 B*07:05 6 1.21 C*15:06 1 0.20 A*74:03 1 0.20 B*35:02 6 1.21 A*02:03 1 0.20 B*58:01 6 1.21 A*26:08 1 0.20 B*13:02 6 1.21 A*30:04 1 0.20 B*56:01 5 1.01 A*01:02 1 0.20 B*41:01 4 0.81 A*29:01 1 0.20 B*35:08 4 0.81 A*24:10 1 0.20 B*39:06 4 0.81 B*41:02 4 0.81 B*15:03 3 0.61 B*15:17 3 0.61 B*14:01 3 0.61 B*55:01 3 0.61 B*44:05 3 0.61 B*40:06 2 0.40 B*50:02 2 0.40 494 100.00 494 100.00 B*51:08 1 0.20 B*39:24 1 0.20 B*15:09 1 0.20 B*27:03 1 0.20 B*18:03 1 0.20 B*57:03 1 0.20 B*51:02 1 0.20 B*78:01 1 0.20 B*35:30 1 0.20 B*47:01 1 0.20 B*27:12 1 0.20 B*15:24 1 0.20 B*27:02 1 0.20 B*44:130 1 0.20 B*15:16 1 0.20 B*15:18 1 0.20 B*46:01 1 0.20 B*39:02 1 0.20 494 100.00 AF, allelic frequency; N, number of observed alleles. ESC Heart Failure 2019; 6: 388–395 DOI: 10.1002/ehf2.12406 HLA haplotypes in heart failure patients 391 Human leukocyte antigen typing exhibited the highest frequencies. Twenty-nine of the HLA-B alleles (32%) appeared less than 1%. As for HLA-C, three al- HLA-A, -B, -C, -DRB1, and -DQB1 were analysed by NGS using leles, C*07:01 (13.36%), C*04:01 (12.96%), and C*05:01 the Illumina MiSeq instrument. Focusing on key exons, the (11.74%), exhibited the most frequencies. Almost one- analysis characterized HLA exons 2 to 4 for class I alleles quarter of the HLA-C alleles appeared with a frequency less and exons 2 and 3 for class II alleles using the NGSengine soft- than 1% (Table 2). ware (version 2.8.0, GenDX, Netherlands) and the November The most likely HLA-DRB1 alleles were DRB1*07:01 2017 IPD-IMGT/HLA database 3.30.0, as the allele reference (14.78%) and DRB1*03:01 (13.16%). Eleven HLA-DRB1 alleles library. The HLA allele frequencies were estimated using (22.22%) were observed less than 1%. The most frequent PyPop software (version http://www.pypop.org). alleles were DQB1*03:01 (15.38%), DQB1*05:01 (14.57%), DQB1*02:01 (13.36%), and DQB1*02:02 (13.36%). All HLA-DQB1 alleles appeared six or more times (Table 3). Human leukocyte antigen haplotype determination Importantly, the most frequent HLA alleles in this HF pop- ulation are in line with the most frequent HLA alleles pre- We determined the HLA haplotype by complete typing of sented in our reference population. In particular, we used HLA-A, -B, -C, -DRB1, and -DQB1. The haplotypes were not as reference database all NGS-typed samples collected in determined by segregation because no parents’ samples the bank of samples of Blood and Tissue Bank (Barcelona, were available. The HLA haplotype estimation was performed Spain). Because Blood and Tissue Bank implemented NGS using HaploStats (http://www.haplostats.org) software based for typing their samples in 2015, they have assessed more on haplotype frequencies. The haplotypes were counted than 15 000 samples from our area (data not shown). Also, using Microsoft Excel. The exact test for deviation from Hardy–Weinberg Equilibrium was evaluated by PyPop software, which uses an algorithm to estimate the P-value. Table 3 Class II allele frequencies in heart failure patients Also, PyPop analyses were performed to estimate the HLA-DRB1 N AF HLA-DQB1 N AF haplotype, linkage disequilibrium (D), and relative linkage DRB1*07:01 73 14.78 DQB1*03:01 76 15.38 disequilibrium (D’). DRB1*03:01 65 13.16 DQB1*05:01 72 14.57 DRB1*15:01 40 8.10 DQB1*02:01 66 13.36 DRB1*13:01 36 7.29 DQB1*02:02 66 13.36 DRB1*01:01 35 7.09 DQB1*03:02 48 9.72 DRB1*11:01 27 5.47 DQB1*06:02 38 7.69 Results DRB1*11:04 23 4.66 DQB1*06:03 36 7.29 DRB1*01:02 21 4.25 DQB1*03:03 22 4.45 DRB1*04:04 17 3.44 DQB1*04:02 15 3.04 Table 1 shows the clinical characteristics of the studied popu- DRB1*13:02 17 3.44 DQB1*05:03 13 2.63 lation. In general, patients were middle-aged and predomi- DRB1*04:05 13 2.63 DQB1*05:02 12 2.43 nantly male, frequently had an ischaemic aetiology, were in DRB1*09:01 11 2.23 DQB1*06:04 9 1.82 DRB1*11:02 10 2.02 DQB1*06:09 8 1.62 NYHA functional class II or III, and were treated following con- DRB1*04:02 10 2.02 DQB1*06:01 7 1.42 temporary guidelines. Within the cohort of HF patients, we DRB1*16:01 10 2.02 DQB1*03:19 6 1.21 measured the HLA-A, -B, -C, -DRB1, and -DQB1 allele and hap- DRB1*08:01 10 2.02 DRB1*04:03 9 1.82 lotype frequencies using whole genomic DNA extracted from DRB1*10:01 9 1.82 peripheral blood samples and high-resolution NGS technol- DRB1*15:02 8 1.62 ogy. While HLA class I alleles were defined based on the DRB1*14:54 7 1.42 DRB1*04:01 6 1.21 sequences of exons 2, 3, and 4, HLA class II alleles were DRB1*13:03 6 1.21 designated based on the sequences of exons 2 and 3. Once DRB1*04:07 5 1.01 HLA typing was performed, we noticed that all patients were DRB1*01:03 5 1.01 DRB1*12:01 5 1.01 heterozygous at the five HLA loci. Furthermore, the genotype DRB1*14:04 4 0.81 frequencies of all five HLA loci were in Hardy–Weinberg DRB1*04:06 2 0.40 equilibrium proportions. DRB1*13:05 2 0.40 DRB1*16:02 1 0.20 In this patient cohort, the number of distinct HLA alleles DRB1*15:03 1 0.20 were 30 for HLA-A, 56 for HLA-B, 23 for HLA-C, 36 for HLA- DRB1*04:11 1 0.20 DRB1, and 15 for HLA-DQB1. Three HLA-A alleles, A*02:01 DRB1*14:05 1 0.20 DRB1*13:11 1 0.20 (24.09%), A*01:01 (13.36%), and A*24:02 (10.12%), were DRB1*08:04 1 0.20 the most frequent HLA-A alleles. Eleven of the HLA-A alleles DRB1*04:37 1 0.20 identified (36.66%) appeared less than 1%. With regard to DRB1*12:02 1 0.20 494 100.00 494 100.00 HLA-B, B*44:03 (9.31%), B*18:01 (7.49%), B*44:02 (7.29%), B*08:01 (6.28%), B*51:01 (6.28%), and B*07:02 (5.47%) AF, allele frequency; N, number of observed alleles. ESC Heart Failure 2019; 6: 388–395 DOI: 10.1002/ehf2.12406 392 S. Roura et al. Table 4 The most frequent haplotypes in heart failure patients ID Haplotypes N HF PHF 1 A*01:01, B*08:01, C*07:01, DRB1*03:01, DQB1*02:01 15 3.04 6.07 2 A*29:02, B*44:03, C*16:01, DRB1*07:01, DQB1*02:02 11 2.23 4.45 3 A*30:02, B*18:01, C*05:01, DRB1*03:01, DQB1*02:01 10 2.02 4.05 4 A*23:01, B*44:03, C*04:01, DRB1*07:01, DQB1*02:02 7 1.42 2.83 5 A*02:01, B*08:01, C*07:01, DRB1*03:01, DQB1*02:01 6 1.21 2.43 6 A*33:01, B*14:02, C*08:02, DRB1*01:02, DQB1*05:01 6 1.21 2.43 7 A*02:01, B*18:01, C*05:01, DRB1*03:01, DQB1*02:01 5 1.01 2.02 8 A*02:01, B*44:02, C*05:01, DRB1*01:01, DQB1*05:01 5 1.01 2.02 9 A*02:01, B*07:02, C*07:02, DRB1*15:01, DQB1*06:02 4 0.81 1.62 10 A*24:02, B*45:01, C*16:01, DRB1*10:01, DQB1*05:01 4 0.81 1.62 11 A*02:01, B*44:02, C*05:01, DRB1*11:01, DQB1*03:01 4 0.81 1.62 31.17 HF, haplotype frequency; ID, identification; N, number of observed haplotypes; PHF, population haplotype frequency. Figure 1 The 11 most frequent haplotypes are present in the 31.17% of five-loci haplotypes analysed, five of which were present six the patients of our cohort. Each column represents the accumulated per- or more times (Table S1). The most common five-loci haplo- centage of individuals that have each haplotype (referenced in Table 4 as type detected was A*01:01-B*08:01-C*07:01-DRB1*03:01- ID) and its previous ones. DQB1*02:01 (3.04%), which had a haplotype frequency of 6.07% per patient (Table 4 ). Remarkably, 31.17% of patients would be covered by the 11 most frequent HLA haplotypes (Figure 1). Lastly, we focused on the two main etiological causes (DCM and IHF) (Tables S2–S7 ). In this context, we found that the frequent haplotype A*29:02-B*44:03-C*16:01- DRB1*07:01-DQB1*02:02 was not present in any of the DCM patients. Moreover, the haplotype A*01:01-B*08:01- C*07:01-DQB1*02:01-DRB1*03:01 (1.19%) was found only once. Discussion The increased incidence and prevalence of congestive HF we used the Allele Frequency Net Database as a reference have led to the need for novel treatment strategies, including (http://allelefrequencies.net). cell-based therapies. Translating cell administration into the We likewise studied the HLA allele, taking into account clinic requires the ability to deliver a safe and efficacious the two main etiological causes of HF in our cohort of product that is ready-to-use at the optimal dosage. Allogeneic patients. Of note, the cohorts of patients with dilated cardio- cell therapy is immediately available and provides a high myopathy (DCM) and ischaemic HF (IHF) showed some number of cells20; however, it is clearly a disruptive concept differences on HLA allele frequencies. Regarding DCM in biology. The standard immunologic dogma holds that any patients, HLA-A*03:01 (5.95%), HLA-B*08:01 (1.19%), and foreign tissue will elicit an immune reaction.20 This is clearly HLA-DRB1*03:01 (8.33%) were less represented as apparent in whole organ, tissue, or cell transplants in which compared with the IHF group and reference database. On aggressive immunosuppression is necessary to protect the contrary, HLA-C*04:01 (20.24%), HLA-DRB1*04:03 allografts from rejection.21 Thus, the analysis of histocompat- (3.57%), HLA-DRB1*04:04 (4.76%), and HLA-DRB1*04:05 ibility is most relevant in this field, where differences be- (3.57%) were more common on patients with DCM. On the tween the donor’s HLA alleles and the recipient’s trigger the other hand, the IHF patients had over represented immune system to reject the transplant. The World Marrow HLA-DQB1*05:01 (16.45%) and HLA-C*05:01 (12.50%). Donor Association guidelines for establishing the extent and HLA-DQB1*03:01 (12.50%) was also less expressed in this quality of histocompatibility testing for unrelated donor regis- cohort of patients. tries, umbilical cord blood banks, and transplant centres When ethnicity of our cohort of HF patients was consid- involved an international exchange of cells for allogeneic ered, we identified 383 unique haplotypes from the 494 therapy.22 ESC Heart Failure 2019; 6: 388–395 DOI: 10.1002/ehf2.12406 HLA haplotypes in heart failure patients 393 As the field of cell-based therapy evolves, it has become bone marrow donors and samples preserved in umbilical cord evident that various cell types – mesenchymal stem cells banks, because both are already HLA typed. The findings from (MSCs) being the prototype – have sufficient ability to evade this study will be part of a subsequent study of samples and/or suppress the immune system to the extent that they stored in the Catalan Blood and Tissue Bank (BST). The search may be used as allografts without requiring concomitant im- and selection of HLA homozygous cord units for the 11 most munosuppression.23,24 Moreover, increasing evidence has frequent haplotypes could extend future administrations of suggested that the effect of infused MSCs is not direct, but therapeutic cells. rather due to paracrine signalling. Paracrine signalling is con- Remarkably, despite further studies using a large cohort of sistent with findings in which a low number of retained or HF patients are warranted to potentially assess statistical sig- seeded cells could promote restorative effects, such as nificances, our findings suggest a protective role for some forming vessels to protect resident cardiomyocytes from ap- haplotypes such as HLA-B*08:01 and HLA-DQB1*03:01, optosis, and mobilize host stem or progenitor cells to poten- which are underrepresented in DCM and IHF patients, tiate both vascularization and cardiomyogenesis.25,26 Thus, respectively. In contrast, the haplotypes HLA-DRB1*04:03, alternative cell sources are being examined, including plurip- HLA-DRB1*04:04, and HLA-DRB1*04:05 could be associated otent stem cells (iPS). The iPS cells are in the preclinical stage, with DCM because their frequencies are higher compared can be generated after inducing the expression of transcrip- with IHF patients and control subjects (reference database). tion factors associated with pluripotency, and exhibit unlim- In sum, the present study revealed, for the first time, the ited self-renewal and differentiation to many cell lineage most frequent HLA allele combinations within a cohort of types.27,28 Clinically, the pluripotency state of iPS allows for ambulatory HF patients. Autologous administration of MSC a wide range of disease treatments, and their pre- and iPS is still preferred for regenerative purposes because differentiation ex vivo may guarantee their safeness.29–31 the rejection risks are avoided. However, our findings Nevertheless, their high proliferation rate increases the risks suggest that safe iPS-based products, e.g. predifferentiated associated with products containing iPS (e.g. risk of tumour cardiomyocytes or endothelial cells, can be useful for treating formation).32 Indeed, in contrast to MSCs, derivatives from these patients in future clinical trials if the recipient and iPS can currently only be used for autologous cell administra- donor are HLA matched. Indeed, an iPS bank of 11 cell lines tion. Thus, it is necessary to generate iPS banks for HLA- will cover almost one-third of this patient population. matched allogeneic cell therapy based on known donor and recipient HLA types. Moreover, the major purposes of devel- oping these iPS banks are to ensure cost-effectiveness, solve Acknowledgements the issue of high time consumption in processing autologous iPS or derivatives, and guarantee their utility for acute We specially thank the nurses, Beatriz González, Margarita patients.33 Rodríguez, Carmen Rivas, Violeta Díaz, Núria Benito, Albas The presented results showed that the most common five- Ros, Jessica Ruiz, and Jenifer García, for data collection and loci haplotype detected was A*01:01-B*08:01-C*07:01- their invaluable work at the HF unit. DRB1*03:01-DQB1*02:01 (3.04%), which had a haplotype frequency of 6.07% per patient in our cohort. This HLA-estimated haplotype within our cohort of patients is Conflict of interest common and conserved in North European Caucasians.34–36 In particular, when we consider the Allele Frequency Net None declared. Database, the haplotype frequency of A*01:01-B*08:01- C*07:01-DQB1*02:01-DRB1*03:01 in North European Caucasians is over 3%. Remarkably, 31.17% of patients in our cohort would be covered by the 11 most frequent haplo- Funding types. This finding from a real setting is in agreement with that previously reported by Gourraud et al.37 These authors This study was supported by Grants from the Ministerio de developed a mathematical model and calculated that, in Educación y Ciencia (SAF2014-59892), Fundació La MARATÓ order to obtain iPS for the 20 most frequent HLA haplotypes, de TV3 (201502, 201516), CIBER Cardiovascular (CB16/11/ 26 000 European-American donors would need to be 00403), Generalitat de Catalunya 2017SGR 00483, CERCA analysed and 50% would be compatible. This confirms that Programme and PERIS Programme, Departament de Salut relatively few, but very well selected, donors would give rise SLT002/16/00234, SLT002_16_00209, and AdvanceCat with to iPS lines with a very important clinical utility. To carry out the support of ACCIÓ (Catalonia Trade & Investment; the screening and identify the largest number of possible Generalitat de Catalunya) under the Catalonian European donors, it would be necessary to collaborate with multiple Regional Development Fund operational programme, centres worldwide.38 This study searched among potential 2014–2020. ESC Heart Failure 2019; 6: 388–395 DOI: 10.1002/ehf2.12406 394 S. Roura et al. Supporting information Table S4. Class I allele frequencies in ischemic heart failure patients. Additional supporting information may be found online in the Table S5. Class II allele frequencies in ischemic heart failure Supporting Information section at the end of the article. patients. Table S6. 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