The distribution of human leukocyte antigens genotypes among Nigerian sickle cell anaemia patients

Abstract

Background: Human leukocyte antigens (HLA) are involved in the modulation of immune responses, thus specific haplotypes, alleles and residues at different loci have been linked with disease susceptibility. There is no substantial data regarding HLA allele's linkage to sickle cell anaemia (SCA) patients from Nigeria.

Objective: This study was carried out to determine the HLA–A*, -B*, -C*, -DRB1* and -DQB1* allele frequency distribution among SCA patients of Nigerian origin.

Methods: This was an observational descriptive study of 169 registered SCA patients of the Sickle Cell Foundation Nigeria who met the European Society for Blood and Marrow Transplantation (EBMT) criteria for haematopoietic bone marrow transplantation and they were counseled for HLA tissue typing along with their siblings to know if there were any potential match among them that could donate stem cell for HSCT. Ten milliliters of venous blood were collected in a sterile Na-EDTA anticoagulant tube from each consenting subject and samples were collected and sent in batches to Istituto Mediterraneo Di Ematologia (IME), Rome, Italy for HLA study. Genomic DNA was isolated from the lymphocytes through QIAGEN DNA mini-isolation kit.  HLA genotyping for HLA –A*, -B*, -C*, -DRB1* and -DQB1* loci typing was done using sequence specific oligonucleotide polymerase chain reaction.

Results: Sixteen alleles were detected at HLA A* locus, 24 alleles at HLA B* locus, 12 alleles at HLA C* locus, 13 alleles at HLA DRB1* locus, and 5 alleles at HLA DQB1* locus. The allele frequencies of these most common alleles were ≥ 10^-1. The less common alleles have allele frequencies (AF %) of ≥10^-2.

Conclusion: HLA (A*23, A*30 and A*02), (B*53 and B*15), (C*04 and C*07), (DRB1*15, DRB1*13, DRB1*11 and DRB1*03) and (DQB1*06, DQB1*05, DQB1*02 and DQB1*03) are the most frequent alleles among SCA patients in Nigeria.

Keywords: Sickle cell anaemia, bone marrow transplantation, human leukocyte antigen, sequence specific oligonucleotide polymerase chain reaction, allele