#5950 MAJOR HLA ALLELE AND HAPLOTYPE FREQUENCIES IN THE MALTESE KIDNEY TRANSPLANT REGISTRY

Abstract

Abstract Background and Aims The human leukocyte antigens (HLA) are the most diverse and polymorphic genes in the human genome and matching them is of vital importance for maximising the survival of kidney transplants. The Maltese archipelago consists of three inhabited islands in the Mediterranean Sea, with a total population of just over half a million people. HLA polymorphisms in Malta have never been described. The aim of this study was to investigate allelic frequencies and determine the most common haplotypes for major HLA Class I and Class II groups in the Maltese kidney transplant registry. This will hopefully facilitate organ sharing with other European countries and improve the HLA matching for kidney transplant recipients. Method All patients of Maltese ethnicity on the national kidney transplant list between 2018 and 2022 were analysed retrospectively. HLA typing is routinely performed at medium to high resolution using polymerase chain reaction sequence specific oligonucleotide probes and Luminex technology at the HLA-A, HLA-B, HLA-C, HLA-DR, HLA-DQ and HLA-DP loci. Allele and haplotype frequencies were calculated by direct counting and simple percentages. Results A total of 191 patient samples were analysed yielding the following allele types: 16 HLA-A, 31 HLA-B, 17 HLA-C, 15 HLA-DRB1, 6 HLA-DP, 7 HLA-DQ, 5 HLA-DRB3, one HLA-DRB4 and one HLA DRB5. The most frequent allele groups for the HLA-A locus were HLA-A*02 (30.9%), HLA-A*24 (12.0%) and HLA-A*01 (11.8%) whilst for the HLA-B locus these were HLA-B*35 (16.2%), HLA-B*18 (11.5%) and HLA-B*51 (7.1%). The most prevalent allele groups for the HLA-DRB1 locus were HLA-DRB1*11 (24.1%), HLA-DRB1*04 (13.1%) and HLA-DRB1*07 (11.3%). The commonest allele group for each of HLA-C, HLA-DP and HLA-DR loci were HLA-C*07 (23.6%), HLA-DP4 (5.8%), HLA-DQ7 (31.2%) respectively. The five most frequently encountered haplotypes were HLA-A*02-B*13-DRB1*07 (2.1%), HLA-A*02-B*35-DRB1*04 (1.6%), HLA-A*02-B*18-DRB1*10 (1.3%), HLA-A*02-B*35-DRB1*11 (1.3%), HLA-A*24-B*35-DRB1*11 (1.3%). Conclusion This study provides the first data on the Major HLA allele and haplotype frequencies in Maltese kidney transplant candidates. Such data may be crucial in setting up international kidney exchange programmes.