Abstract:
Human leukocyte antigens (HLA) diversity has a tremendous impact on shaping the
transplantation practices, transfusion-associated graft versus host disease prevention
strategies, and host–pathogen interactions. Here, we conducted a retrospective study of
HLA class I and class II homozygosity at allelic and haplotype levels in unrelated individuals
genotyped from 2012 to 2016 in a tertiary hospital in the capital of Saudi Arabia. Among
5,000 individuals, 2,773 individuals meet inclusion criteria and were retrospectively
analyzed for HLA-A, -B, -C–DRB1, and -DQB1 homozygosity at allelic and haplotype
levels. HLA molecular typing was performed using a commercial reverse sequencespecific oligonucleotide (rSSO) kit. We were able to identify 15 HLA-A, 20 HLA-B,
11 HLA-C, 13 HLA-DRB1, and five HLA-DQB1 homozygous alleles demonstrating a
very low genetic diversity in the Saudi population. The highest homozygosity in HLA class I
was found in locus C followed by A and B (20.3% > 16.1% > 15.5%; p < 0.001) where the
most homozygote alleles were A*02 (9.2%), B*51 and B*50 (5.7% and 3.7%), and C*07,
C*06, and C*15 (7.2%, 5.48%, and 3.3%) and in HLA class II, the highest homozygosity
was found in locus DQB1 compared to DRB1 (31.71% > 19.2%; p < 0.001), with the most
common homozygote alleles being DRB1*07 and DRB1*04 (5.33% and 4.2%) and
DQB1*02, DQB1*06, and DQB1*03 (13.55%, 7.92%, and 7.64%). The frequency of
finding an individual with one homozygote allele was (24.6%), two homozygote alleles
(13.5%), three homozygote alleles (4.7%), four homozygote alleles (3.4%), and five alleles
were (4.8%). The most frequent homozygote haplotypes are
A*23~C*06~B*50~DRB1*07~DQB1*02 and A*02~C*06~B*50~DRB1*07~DQB1*02.
This study shows low diversity of both class I and II alleles and haplotypes in the
Saudi population, which would have a significant impact on shaping the
transplantation practices, transfusion-associated graft versus host disease prevention
strategies, and host–pathogen interactions.
