Balkan Journal of Medical Genetics

HIGH-RESOLUTION HLA-DRB1 ALLELE FREQUENCIES IN A ROMANIAN COHORT OF STEM CELL DONORS
Caragea ÌÀ, Ursu IR, Visan DL, Maruntelu I, Iordache P, Constantinescu A, Tizu M, Tălăngescu A, Constantinescu I
*Corresponding Author: Lect., MD, PhD Radu-Ioan Ursu, Carol Davila University of Medicine and Pharmacy, Department of Medical Genetics, Bucharest, Romania, Str. Batistei 12, Bucharest, Romania; tel.: 0040736167020; e-mail: dr.radu.ursu@gmail.com
page: 43

RESULTS

A total of 41 different HLA-DRB1 alleles were de- tected in our cohort (table 1). Table 1. The alleles with the highest frequen- cies for the HLA-DRB1 locus were represented by the DRB1*16:01:01 (12.6%), DRB1*11:04:01 (12.1%), DRB1*03:01:01 (12%), DRB1*07:01:01 (9.3%), DRB1*01:01:01 (7.3%), DRB1*11:01:01 (6.3%) and DRB1*13:01:01 (6%) (table 1). Out of the total of 41 de- tected alleles, 3 had frequencies higher than 10% (table 1), identified out of a total of 297 individuals. The top 3 alleles amount to more than one third of all the identified alleles (36.67%) (table 1). All these 3 alleles had frequencies of 12% - 13% [DRB1*16:01:01 (12.6%), DRB1*11:04:01 (12.1%), DRB1*03:01:01 (12%)], with the top frequency at 12.6% (table 1, figure 1).7 of the 41 HLA-DRB1 alleles had frequencies higher than 5%. In total, the added frequencies of these 7 alleles rep- resent almost two thirds (65.55%) of all detected HLA- DRB1 variants, identified in 531 individuals. HLA-DRB1 alleles with low frequencies (<5%) stand for 35% (279 individuals) of all observed variants (table 1). Out of the entire cohort and all detected HLA-DRB1 variants, 18 alleles showed frequencies lower than 1% (table 1). 13 of these rare variants were detected in just one individual each (0.12%), while the HLA-DRB1*02:02:01 allele was observed in 2 individuals (0.24%) and DRB1*08:03:02 in 3 (0.37%), all with frequencies lower than 0.5%. 3 of the 18 rare alleles had frequencies of 0.5%-1% (DRB1*11:03:01 and DRB1*14:04:01, both in 8 individu- als, 0.99% each) and DRB1*11:03:01 (6 persons, 0.74%). Apart from the aforementioned 18 rare HLA-DRB1 alleles, 4 others had frequencies close to 1% (1.11%), being detected in 9 individuals each. These 4 alleles represent together 4.44% of all resulted HLA-DRB1 variants. In total, 22 HLA-DRB1 alleles had frequencies of a maximum of 1.11%, totalizing 9.38% of all detected vari- ants and being identified in 76 individuals. The rest of the 734 HLA-DRB1 alleles represent 90.62% of all variants. When adding the identified frequencies of all the variants for each HLA-DRB1 allele, the top alleles, with frequencies higher than 10%, were DRB1*11 (19.38%), DRB1*16 (13.95%), DRB1*03 (12.10%), DRB1*13 (10.99%) (table 2, figure 2). Table 2. 6 other alleles revealed average frequencies, of 5% - 10% (DRB1*04, DRB1*07, DRB1*01, DRB1*15 and DRB1*14), while 2 were found in the 1%-5% fre- quency range and 3 had low frequencies, of less than 1% (DRB1*02, DRB1*05, DRB1*09) (table 2).

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