{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,4]],"date-time":"2026-07-04T19:42:39Z","timestamp":1783194159709,"version":"3.54.6"},"reference-count":28,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2025,5,29]],"date-time":"2025-05-29T00:00:00Z","timestamp":1748476800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Human Leukocyte Antigen (HLA) genes are remarkable for their structural complexity and polymorphism. Located on chromosome 6 within the Major Histocompatibility Complex (MHC), these genes exhibit significant frequency variations across human populations and play a crucial role in immune responses, disease susceptibility, and transplant compatibility. This study aimed to assess the genetic profiles and HLA-A\/HLA-B\/HLA-C\/HLA-DRB1 haplotype frequencies in a Romanian cohort. Whole venous blood samples were collected from 405 healthy, unrelated Romanian volunteers. Using next-generation sequencing (NGS), the study population was genotyped for HLA class I (HLA-A, HLA-B, and HLA-C) and class II (HLA-DRB1) loci. Haplotype frequencies were estimated using the expectation-maximization algorithm, addressing phase and allelic ambiguity. The Romanian cohort was compared with multiple populations sourced from the Allele Frequencies Net Database. The study identified 635 different HLA-A\/HLA-B\/HLA-C\/HLA-DRB1 haplotypes. Among them, two haplotypes had frequencies close to 3%: HLA-A*01:01:01\/HLA-B*08:01:01\/HLA-C*07:01:01\/HLA-DRB1*03:01:01, with a frequency of 3.33%, and HLA-A*02:01:01\/HLA-B*18:01:01\/HLA-C*17:01:01\/HLA-DRB1*11:04:01, with a frequency of 2.84%. All other 633 haplotypes (approximately 99.7% of the total) had frequencies below 1%. The results of the current study underscore the extremely high diversity of HLA haplotypes in this population and the fact that even the most frequent haplotypes are relatively low in prevalence (each under 5% in this cohort). These findings and the great haplotypical diversity detected highlight the importance of NGS and high-resolution HLA typing in hematopoietic stem cell and solid organ transplantation, while also contributing to the better understanding of the area-specific population genetics resulting from historical regional dynamics. Further research with larger cohorts is necessary to validate these findings and expand upon their clinical implications.<\/jats:p>","DOI":"10.3390\/ijms26115250","type":"journal-article","created":{"date-parts":[[2025,5,30]],"date-time":"2025-05-30T06:14:27Z","timestamp":1748585667000},"page":"5250","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Characterization of HLA-A\/HLA-B\/HLA-C\/HLA-DRB1 Haplotypes in Romanian Stem Cell Donors Through High-Resolution Next-Generation Sequencing"],"prefix":"10.3390","volume":"26","author":[{"given":"Andreea Mirela","family":"Caragea","sequence":"first","affiliation":[{"name":"Department of Immunology and Transplantation Immunology, \u201cCarol Davila\u201d University of Medicine and Pharmacy, 050474 Bucharest, Romania"},{"name":"Center for Immunogenetics and Virology, Fundeni Clinical Institute, 050474 Bucharest, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Radu-Ioan","family":"Ursu","sequence":"additional","affiliation":[{"name":"Department of Medical Genetics, \u201cCarol Davila\u201d University of Medicine and Pharmacy, 050474 Bucharest, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lauren\u021biu Camil","family":"Boh\u00eel\u021bea","sequence":"additional","affiliation":[{"name":"Department of Medical Genetics, \u201cCarol Davila\u201d University of Medicine and Pharmacy, 050474 Bucharest, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Paul","family":"Iordache","sequence":"additional","affiliation":[{"name":"Department of Epidemiology, \u201cCarol Davila\u201d University of Medicine and Pharmacy, 050474 Bucharest, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alexandra-Elena","family":"Constantinescu","sequence":"additional","affiliation":[{"name":"Department of Immunology and Transplantation Immunology, \u201cCarol Davila\u201d University of Medicine and Pharmacy, 050474 Bucharest, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5828-2694","authenticated-orcid":false,"given":"Ileana","family":"Constantinescu","sequence":"additional","affiliation":[{"name":"Department of Immunology and Transplantation Immunology, \u201cCarol Davila\u201d University of Medicine and Pharmacy, 050474 Bucharest, Romania"},{"name":"Center for Immunogenetics and Virology, Fundeni Clinical Institute, 050474 Bucharest, Romania"},{"name":"\u201cEmil Palade\u201d Center of Excellence for Young People in Scientific Research (EP-CEYR), Academy of Romanian Scientists, AORS, 050045 Bucharest, Romania"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,5,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"145","DOI":"10.1016\/j.humimm.2017.12.003","article-title":"HLA-A, -B, -C and -DRB1 allele and haplotype frequencies in the Macedonian population based on a family study","volume":"79","author":"Kirijas","year":"2018","journal-title":"Hum. Immunol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1111\/j.1399-0039.2008.01151.x","article-title":"HLA-A, -B, -C, and -DRB1 allele and haplotype frequencies distinguish Eastern European Americans from the general European American population","volume":"73","author":"Mack","year":"2008","journal-title":"Tissue Antigens"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"162","DOI":"10.1159\/000360855","article-title":"A new HLA map of Europe: Regional genetic variation and its implication for peopling history, disease-association studies and tissue transplantation","volume":"76","author":"Buhler","year":"2013","journal-title":"Hum. Hered."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"375","DOI":"10.1353\/hub.2003.0040","article-title":"HLA genes in the Chuvashian population from European Russia: Admixture of Central European and Mediterranean populations","volume":"75","author":"Moscoso","year":"2003","journal-title":"Hum. Biol."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Toki\u0107, S., \u017di\u017ekova, V., \u0160tefani\u0107, M., Glava\u0161-Obrovac, L., Marczi, S., Samard\u017eija, M., Sikorova, K., and Petrek, M. (2020). HLA-A, -B, -C, -DRB1, -DQA1, and -DQB1 allele and haplotype frequencies defined by next generation sequencing in a population of East Croatia blood donors. Sci. Rep., 10.","DOI":"10.1038\/s41598-020-62175-9"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"51","DOI":"10.1111\/tan.13401","article-title":"HLA allele and haplotype diversity in the Croatian population: State of the art","volume":"92","author":"Grubic","year":"2018","journal-title":"HLA"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"394","DOI":"10.1111\/j.1744-313X.2012.01117.x","article-title":"HLA gene and haplotype frequencies in Russians, Bashkirs and Tatars, living in the Chelyabinsk Region (Russian South Urals)","volume":"39","author":"Suslova","year":"2012","journal-title":"Int. J. Immunogenet."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"337","DOI":"10.1111\/j.1744-313X.2009.00868.x","article-title":"HLA allele and haplotype frequencies in the Albanian population and their relationship with the other European populations","volume":"36","author":"Sulcebe","year":"2009","journal-title":"Int. J. Immunogenet."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"193","DOI":"10.1111\/j.1399-0039.2007.00991.x","article-title":"Allele and extended haplotype polymorphism of HLA-A, -C, -B, -DRB1 and -DQB1 loci in Polish population and genetic affinities to other populations","volume":"71","author":"Nowak","year":"2008","journal-title":"Tissue Antigens"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"820","DOI":"10.1098\/rstb.2011.0320","article-title":"Tracking human migrations by the analysis of the distribution of HLA alleles, lineages and haplotypes in closed and open populations. Philosophical transactions of the Royal Society of London","volume":"367","author":"Hollenbach","year":"2012","journal-title":"Ser. B Biol. Sci."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"211","DOI":"10.1111\/iji.12117","article-title":"HLA-A, HLA-B and HLA-DRB1 allele and haplotype diversity among volunteer bone marrow donors from Croatia","volume":"41","author":"Grubic","year":"2014","journal-title":"Int. J. Immunogenet."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"167","DOI":"10.1007\/s00251-015-0891-9","article-title":"The frequency of HLA alleles in the Romanian population","volume":"68","author":"Constantinescu","year":"2016","journal-title":"Immunogenetics"},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Arrieta-Bola\u00f1os, E., Hern\u00e1ndez-Zaragoza, D.I., and Barquera, R. (2023). An HLA map of the world: A comparison of HLA frequencies in 200 worldwide populations reveals diverse patterns for class I and class II. Front. Genet., 14.","DOI":"10.3389\/fgene.2023.866407"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"21","DOI":"10.1111\/j.1399-0039.2011.01668.x","article-title":"HLA-A, HLA-B, and HLA-DRB1 allele distribution in a large Armenian population sample","volume":"78","author":"Matevosyan","year":"2011","journal-title":"Tissue Antigens"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"111","DOI":"10.1034\/j.1399-0039.2002.600201.x","article-title":"Population genetic relationships between Mediterranean populations determined by HLA allele distribution and a historic perspective","volume":"60","year":"2002","journal-title":"Tissue Antigens"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Drenovska, K., Ivanova, M., Vassileva, S., Shahid, M.A., and Naumova, E. (2022). Association of specific HLA alleles and haplotypes with pemphigus vulgaris in the Bulgarian population. Front. Immunol., 13.","DOI":"10.3389\/fimmu.2022.901386"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"249","DOI":"10.1111\/tan.14937","article-title":"HLA allele and haplotype frequencies in Kazakhstani Russians and their relationship with other populations","volume":"101","author":"Hajjej","year":"2023","journal-title":"HLA"},{"key":"ref_18","first-page":"1342762","article-title":"HLA Polymorphisms and Haplotype Diversity in Transylvania, Romania","volume":"2019","author":"Matei","year":"2019","journal-title":"J. Immunol. Res."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"341","DOI":"10.1111\/j.1399-0039.2012.01936.x","article-title":"HLA population genetics: A Lebanese population","volume":"80","author":"Cano","year":"2012","journal-title":"Tissue Antigens"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"807","DOI":"10.1016\/j.humimm.2019.07.275","article-title":"Next-generation sequencing reveals new information about HLA allele and haplotype diversity in a large European American population","volume":"80","author":"Creary","year":"2019","journal-title":"Hum. Immunol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"3593","DOI":"10.1007\/s11033-021-06379-w","article-title":"Application of the conventional and novel methods in testing EGFR variants for NSCLC patients in the last 10 years through different regions: A systematic review","volume":"48","author":"Obradovic","year":"2021","journal-title":"Mol. Biol. Rep."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Caragea, A.M., Ursu, R.-I., Maruntelu, I., Tizu, M., Constantinescu, A.-E., T\u0103l\u0103ngescu, A., and Constantinescu, I. (2024). High Resolution HLA-A, HLA-B, and HLA-C Allele Frequencies in Romanian Hematopoietic Stem Cell Donors. Int. J. Mol. Sci., 25.","DOI":"10.3390\/ijms25168837"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"43","DOI":"10.2478\/bjmg-2024-0009","article-title":"High-Resolution HLA-DRB1 Allele Frequencies in a Romanian Cohort of Stem Cell Donors","volume":"27","author":"Caragea","year":"2024","journal-title":"Balkan J. Med. Genet."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"101559","DOI":"10.1016\/j.beha.2024.101559","article-title":"PGAE HLA Consortium of the 18th International HLA and Immunogenetics Workshop. The most frequent HLA alleles around the world: A fundamental synopsis","volume":"37","author":"Nunes","year":"2024","journal-title":"Best Pract. Res. Clin. Haematol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"233","DOI":"10.1016\/j.humimm.2016.01.020","article-title":"The IPD-IMGT\/HLA Database\u2013New developments in reporting HLA variation","volume":"77","author":"Robinson","year":"2016","journal-title":"Hum. Immunol."},{"key":"ref_26","first-page":"D783","article-title":"Allele frequency net database (AFND) 2020 update: Gold-standard data classification, open access genotype data and new query tools","volume":"48","author":"McCabe","year":"2020","journal-title":"Nucleic Acids Res."},{"key":"ref_27","unstructured":"(2025, January 02). Allele Frequency Database. Available online: http:\/\/www.allelefrequencies.net."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"D913","DOI":"10.1093\/nar\/gkq1128","article-title":"Allele frequency net: A database and online repository for immune gene frequencies in worldwide populations","volume":"39","author":"Christmas","year":"2011","journal-title":"Nucleic Acids Res."}],"container-title":["International Journal of Molecular Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1422-0067\/26\/11\/5250\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T17:43:34Z","timestamp":1760031814000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1422-0067\/26\/11\/5250"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,5,29]]},"references-count":28,"journal-issue":{"issue":"11","published-online":{"date-parts":[[2025,6]]}},"alternative-id":["ijms26115250"],"URL":"https:\/\/doi.org\/10.3390\/ijms26115250","relation":{},"ISSN":["1422-0067"],"issn-type":[{"value":"1422-0067","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,5,29]]}}}