Two novel alleles HLA-A*02:433 and HLA-A*02:434 identified in Saudi bone marrow donors using sequence-based typing

Area of Science:

• Immunogenetics
• Molecular Biology
• Human Leukocyte Antigen (HLA) System

Background:

• The Human Leukocyte Antigen (HLA) system plays a critical role in immune response and transplantation.
• Accurate HLA typing is essential for successful allogeneic bone marrow transplantation.
• The Saudi Bone Marrow Donor Registry (SBMDR) contributes to global HLA allele diversity data.

Purpose of the Study:

• To report the identification and characterization of two previously unknown HLA-A alleles.
• To contribute novel HLA-A allele sequences to the global HLA database.
• To enhance the accuracy of HLA matching for potential bone marrow donors.

Main Methods:

• Sequence-Based Typing (SBT) was employed for high-resolution HLA allele identification.
• Analysis of nucleotide sequences to pinpoint specific variations from known alleles.
• Comparison of novel sequences against existing HLA allele databases.

Main Results:

• Two novel HLA-A alleles, designated HLA-A*02:433 and HLA-A*02:434, were discovered.
• HLA-A*02:433 differs from HLA-A*02:05:01G by a single nucleotide substitution (G>A at position 449 in exon 2), resulting in an amino acid change (Gly83Ser).
• HLA-A*02:434 differs from HLA-A*02:01:01G by a single nucleotide substitution (C>A at position 245 in exon 2), resulting in an amino acid change (Phe15Thr).

Conclusions:

• The identified alleles likely arose from point mutations within existing HLA-A*02 subtypes.
• These novel alleles represent important additions to the HLA-A genetic diversity.
• Accurate identification of these alleles is vital for improving HLA matching in bone marrow registries.