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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 33  |  Issue : 4  |  Page : 370-373

Two probable human leukocyte antigen haplotypes in association with human leukocyte antigen HLA-DRB1*13:50:01 identified in 41 randomized unrelated Taiwanese individuals


1 Department of Laboratory Medicine and Biotechnology, Tzu Chi University, Hualien, Taiwan
2 Department of Laboratory Medicine and Biotechnology, Tzu Chi University; Laboratory of Immunogenetics, Tzu Chi Cord Blood Bank, and Buddhist Tzu Chi Bone Marrow Donor Registry, Buddhist Tzu Chi Stem Cells Centre, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan

Date of Submission25-Dec-2020
Date of Decision21-Jan-2021
Date of Acceptance02-Feb-2021
Date of Web Publication11-May-2021

Correspondence Address:
Kuo-Liang Yang
Buddhist Tzu Chi Stem Cells Centre, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, 707, Section 3, Chung-Yang Road, Hualien
Taiwan
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/tcmj.tcmj_304_20

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  Abstract 


Objectives: Here, we show two probable haplotypes associated with the human leukocyte antigen (HLA) DRB1*13:50:01 allele. The haplotypes were observed from 41 randomized unrelated Taiwanese individuals among a population of 23,064 individuals tested. Materials and Methods: The samples in this study were blood samples, preserved in dipotassium ethylenediaminetetraacetic acid and/or ACD anticoagulants. The population is of donors from Tzu Chi Bone Marrow Donor Registry. Allele typing was performed using the sequence-based typing method, Sanger's sequencing. To discern the HLA-A and HLA-B alleles, exons 2 and 3 were sequenced. For DRB1 alleles, exon 2 was sequenced. Target exon sequence amplifications were done by a polymerase chain reaction and the resulting amplicons were sequenced by Bigdye Terminator Cycle Sequencing Ready Reaction kit, according to the manufacturer's protocols. Results: Two probable haplotypes that are associated with the DRB1*13:50:01 were observed among the 23,064 Taiwanese randomized unrelated individuals. One of the haplotypes is observed in 39 individuals while the other in two individuals. Conclusion: The findings in this study may be useful in studies reinforcing the understanding and clinical application of the polymorphism of HLA genes and haplotypes.

Keywords: DRB*13:50:01, Haplotypes, Human leukocyte antigen, Taiwanese


How to cite this article:
Mazibuko NA, Yang KL. Two probable human leukocyte antigen haplotypes in association with human leukocyte antigen HLA-DRB1*13:50:01 identified in 41 randomized unrelated Taiwanese individuals. Tzu Chi Med J 2021;33:370-3

How to cite this URL:
Mazibuko NA, Yang KL. Two probable human leukocyte antigen haplotypes in association with human leukocyte antigen HLA-DRB1*13:50:01 identified in 41 randomized unrelated Taiwanese individuals. Tzu Chi Med J [serial online] 2021 [cited 2021 Oct 22];33:370-3. Available from: https://www.tcmjmed.com/text.asp?2021/33/4/370/315866




  Introduction Top


The genes of the human leukocyte antigen (HLA) system of the major histocompatibility complex are genes found in the short arm of chromosome number 6. These genes are characterized by a very high polymorphism tendency which allows them to activate the immune system in fighting many biological intruders. HLA holds a very significant role in the transplantation portion of precision medicine in the clinical practices, to reduce graft versus host diseases and improve graft acceptance by the host. Previous studies show associations between some HLA genes and clinical manifestations, where the gene may either show to favor or even be disadvantageous for the condition[1].

HLA genes may vary as a result of many different modification mechanisms and it is those modifications that result in the formation of the different protein product (s) that are significant in transplantation. Chen et al.[2] have shown the observed modification of two protein sites in the protein of DRB1*11:01:01 for the formation of DRB1*13:50:01.

In transplantation medicine, donor-recipient matching is focused on allele level typing and yet haplotype match may be an even closer relationship in the HLA genes[3],[4].

A haplotype in HLA refers to genes that are inherited together from one parent to the offspring. Recombination of the HLA gene is a genetic modification mechanism that may result in the formation of new alleles[5], but for a haplotype to be recognized in the offspring, we see this, especially in family aggregation studies, the gene should be as it was in the parent. In this article, we show the likely HLA haplotype associated with DRB1*13:50:01 in 41 randomized unrelated Taiwanese individuals. Up to date, the DRB1*13:50:01 allele has been observed in two individuals, 1DM4038S1 (from Taiwan) and BY00138 (from China), according to the IPD-IMGT/HLA Database[6]. Here, in this retrospective study, we show the HLA typing results of 41 randomized unrelated Taiwanese individuals and propose the HLA haplotypes associated with DRB1*13:50:01.


  Materials and Methods Top


The samples were peripheral whole blood, with dipotassium ethylenediaminetetraacetic acid and/or acid citrate dextrose (ACD) anticoagulation additives, collected from randomized unrelated Taiwanese individuals with written informed consent at the time of blood collection. All samples were stored at -80°C until DNA extraction. Nucleic acid extraction was performed using QIAamp DNA Mini Kit-Qiagen, according to the manufacturer's protocol. The DNA samples were stored at -20° C until use. As this is a retrospective study on reviewing and analyzing the HLA typing data of individual donors, the IRB/IRC approval is exempted.

Low-resolution amplification and sequencing of the genomic HLA genes were carried out using MEDIGEN BIOTECHNOLOGY CORP. Typing Kit, provided by TBG Biotechnology Corp. High-resolution amplification was done using the HLAssure SE A/B/DRB-EX Locus SBT Kit. The amplicons were then typed using sequence-based typing, Sanger sequencing. To discern the HLA-A and HLA-B loci alleles, exons 2 and 3 were sequenced and only exon 2 for HLA-DRB1. Amplicons were sequenced using the Bigdye Terminator Cycle Sequencing Ready Reaction kit, according to the manufacturer's protocol.

It was through the studying of the typing results in our database that the repeating set of genes among a few individuals was noticed. The investigation was done and the donor typing that had the DRB1*13:50:01 was collected and analyzed to deduce a possible relationship between this DRB1 allele and alleles in HLA-A and HLA-B loci.


  Results Top


The frequency of the DRB1*13:50:01 allele in the general Taiwanese population is estimated approximately 0.18% based on the total number of 23,064 randomized unrelated Taiwanese individuals studied. This frequency is slightly higher than the 0.10% as estimated by the Allele Frequency Net Database for worldwide populations[7].

In the list of HLA typing results of individuals that have the DRB1*13:50:01 allele [Table 1], we noticed a pattern in HLA-A and HLA-B loci where the HLA-A*02 and HLA-B*40 allele group presented. The constant appearance of this set of allele group HLA-A*02, HLA-B*40, and DRB1*13:50:01 in these three loci, where it showed in 39 unrelated individuals had us concluded that this is probably an HLA haplotype associated with DRB1*13:50:01. We also observed two individuals, donors 366796 and 390827 [Table 1], who are exceptions for A*02-B*40-DRB1*13:50:01 haplotype. These two have the HLA-B*40 and HLA-DRB1*13:50:01 alleles without HLA-A*02 allele but have A*11 allele in common. We postulate that they probably carry the haplotype A*11-B*40-DRB1*13:50:01 alternatively.
Table 1: A probable DRB1*13:50:01 associated HLA haplotype HLA-A*02-HLA-B*40-HLA-DRB1* 13:50:01 is deduced from 39 randomized unrelated Taiwanese individuals who carry A*02, B*40 and DRB1*13:50:01 (underlined) in common. While a second probable DRB1*13:50:01 associated HLA haplotype HLA-A*11-HLA-B*40-HLA-DRB1* 13:50:01 (shaded) is deduced from two randomized unrelated donors 366796 and 390827 (shaded) who commonly shared A*11, B*40 and DRB1*13:50:01 (shaded)

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In exon 2, the DNA sequence of DRB1*13:50:01 bears a partial sequence identity to the sequences of DRB1*03:01:01:01, DRB1*11:01:01:01, and DRB1*13:02:01:01 [Figure 1]a. Through the comparison of the sequences of DRB1*13:50:01 and DRB1*11:01:01:01, they have identical sequence starting from codon 6 to codon 36 and from codon 59 to codon 94. On the other hand, the sequence of DRB1*13:50:01 shares identical sequence with that of either DRB1*03:01:01:01 or DRB1*13:02:01:01 from codon 37 to codon 58. This exchange of gene segments between DRB1*03:01:01:01, DRB1*11:01:01:01 and DRB1*13:02:01:01 suggests a recombination event occurred where either DRB1*03:01:01:01 or DRB1*13:02:01:01 donated a segment of DNA sequence from codon 37 to codon 58 to the sequence of DRB1*11:01:01:01 resulted the formation of DRB1*13:50:01. In agreement with the DNA sequence comparison, the comparison of protein sequences between DRB1*13:50:01 and DRB1*03:01:01:01, DRB1*11:01:01:01 and DRB1*13:02:01:01 is depicted in [Figure 1]b. It shows that the amino acid sequence of DRB1*13:50:01 is identical to DRB1*11:01:01:01 from residue number 6 to residue number 36 and from residue number 59 to residue number 94. On the other hand, the amino acid sequence of DRB1*13:50:01 is identical to either DRB1*03:01:01:01 or DRB1*13:02:01:01 from residue number 37 to residue number 58.
Figure 1: (a) In exon 2 the DNA sequence of DRB1*13:50:01shares similarity with DRB1*03:01:01:01, DRB1*11:01:01:01 and DRB1*13:02:01:01. The sequence of DRB1*13:50:01 is identical to DRB1*11:01:01:01 from codon 6 to codon 36 and from codon 59 to codon 94 (shaded). On the contrary, the sequence of DRB1*13:50:01 shares identical sequence with that of DRB1*03:01:01:01 and DRB1*13:02:01:01 from codon 37 to codon 58 (underlined). This exchange of gene segments between DRB1*03:01:01:01, DRB1*11:01:01:01 and DRB1*13:02:01:01 suggests a crossing-over event occurred during the stage of germ cell division which resulted the formation of DRB1*13:50:01. (b) The amino acid sequence of DRB1*13:50:01 is identical to DRB1*11:01:01:01 from residue number 6 to residue number 36 and from residue number 59 to residue number 94 (shaded). Similarly, the amino acid sequence of DRB1*13:50:01 is identical to either DRB1*03:01:01:01 or DRB1*13:02:01:01 from residue number 37 to residue number 58 (underlined). Dashes indicate nucleotide and amino acid identity with DRB1*13:50:01

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  Discussion Top


In this study, based on the HLA typing of 41 Taiwanese randomized unrelated individuals, we deduced two likely HLA haplotypes in association with DRB1*13:50:01 allele, namely A*02-B*40-DRB1*13:50:01 and A*11-B*40-DRB1*13:50:01. The allele DRB1*13:50:01, according to the Allele Frequency Net Database[7], was also reported in the US Asian population with a different haplotype (A*11-B*15:02-DRB1*13:50:01). This observation suggests that various DRB1*13:50:01 associated HLA haplotype may be revealed if further populations are investigated. The high-resolution variants of the most HLA-A*02 and HLA-B*40 alleles in the deduced haplotypes have not yet been defined here, however where the high resolution has been attained for the HLA-A and HLA-B loci, the alleles observed are HLA-A*02:01 and HLA-B*40:01 [Table 1]. A future in-depth study to resolve the issue may be worthwhile to continue. Comparing the findings to the information in the IPD-IMGT/HLA Database and the Allele Frequency Net Database, we were once again reminded that a bigger database is important in the course of understanding the HLA genes and HLA haplotypes.


  Conclusion Top


In this study we show the HLA typing results of 41 randomized unrelated Taiwanese individuals and propose two HLA haplotypes associated with DRB1*13:50:01. The findings here may be useful in studies reinforcing the understanding and clinical application of the polymorphism of HLA genes and haplotypes.

Acknowledgments

The authors would like to offer special gratitude to the volunteer donors for their participation in our bone marrow donor registry. We would also like to express sincere thanks to Dharma Master Cheng Yen, founder of the Buddhist Compassion Relief Tzu Chi Foundation, for continuing support and kind encouragement both spiritually and intellectually. The generosity and camaraderie of our colleagues are also greatly appreciated.

Financial support and sponsorship

Nil.

Conflicts of interest statement

There are no conflicts of interest.



 
  References Top

1.
Bettencourt A, Carvalho C, Leal B, Brás S, Lopes D, Martins da Silva A, et al. The Protective Role of HLA-DRB1(*) 13 in autoimmune diseases. J Immunol Res 2015;2015:948723.  Back to cited text no. 1
    
2.
Chen ZX, Tsan SG, Dang CW, Chu CC, Lin M, Lee YJ. Identification of two new HLA-DRB1 alleles: HLA-DRB1*1350 and DRB1*140502. Tissue Antigens 2004;64:300-3.  Back to cited text no. 2
    
3.
Yang KL, Lin PY. The deduced probable HLA-C*03:187-associated human leukocyte antigen haplotype (A*24:02-B*35:01-C*03:187-DRB1*11:01) revealed in Taiwanese unrelated hematopoietic bone marrow stem cell donors. Ci Ji Yi Xue Za Zhi 2020;32:254-7.  Back to cited text no. 3
    
4.
Yang KL, Zheng ZZ. Deduced probable human leukocyte antigen haplotypes associated with human leukocyte antigen DRB1*04:36 identified by case analysis of Taiwanese individuals. Ci Ji Yi Xue Za Zhi 2017;29:12-7.  Back to cited text no. 4
    
5.
Mishra MN, Sharma A. Recombination in human leukocyte antigen region in two Asian Indian families. Indian J Hum Genet 2012;18:109-11.  Back to cited text no. 5
  [Full text]  
6.
Robinson J, Barker DJ, Georgiou X, Cooper MA, Flicek P, Marsh SG. IPD-IMGT/HLA database. Nucleic Acids Res 2020;48:D948-55.  Back to cited text no. 6
    
7.
Allele*Frequencies Net Database. Available from: http://www.allelefrequencies.net. [Last accessed on 2020 Dec 18].  Back to cited text no. 7
    


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