Identification of a new HLA-DRB1 allele, HLA-DRB1*0436

Association of HLA-C*07:359 with HLA-A, -B, and -DRB1 alleles in Taiwanese

Objectives

It is thought that Taiwanese indigenous people were the "first people" to populate Taiwan (Formosa) having been there for over 5000 years, preceding the Dutch colonization (from 1624 to 1662) and Spanish colonization (from 1626 to 1642). Taiwan's indigenes, represented by Austronesian language speakers, currently constitute approximately 2% of the total population in Taiwan. It is unknown whether they evolved from Taiwan's Paleolithic or Neolithic cultures, arrived during or after the Neolithic period from China or Southeast Asia or both. HLA studies on the Taiwanese indigenous population have found several intriguing genetic information showing one or two relatively frequently observed alleles and a small number of relatively less frequently observed ones. We report here a relatively frequently observed HLA-C*07:359 allele in the Taiwanese indigenous population, its linkage with HLA-B*39:01, and its probable associated HLA haplotype in two Taiwanese indigenous families. HLA-C*07:359 is a rarely observed allele in the HLA-C locus in the world populations. The objective of this study is to report the allele HLA-C*07:359 that is more frequently found in the Taiwanese population, especially in the Taiwanese indigenous people, to demonstrate that it has a close linkage with HLA-B*39:01 allele in the HLA-B locus and to show the plausible deduced HLA-A-C-B-DRB1-DQB1 haplotypes in association with HLA-C*07:359 in two families of Taiwanese indigenous unrelated individuals.

Materials and Methods

The samples were peripheral whole blood, with dipotassium ethylenediaminetetraacetic acid and/or acid citrate dextrose anticoagulation additives. The sequence-based typing method was employed to confirm the low incidence of the allele of HLA-C*07:359 observed in Taiwanese. Polymerase chain reaction was carried out to amplify exons 2, 3, and 4 of the HLA-A,-B,-C,-DRB1 and-DQB1 loci with group-specific primer sets. Amplicons were sequenced using the BigDye Terminator Cycle Sequencing Ready Reaction Kit in both directions according to the manufacturer's protocol.

Results

C*07:359 is an uncommon allele in the HLA-C locus in the world general population, according to our literature review. However, in this study, it is observed in the general Taiwanese population (frequency 0.41%), especially in the Taiwanese indigenous people at a frequency of 0.23%. In addition, we deduced two probable HLA haplotypes in association with C*07:359 in two indigenous families: A*24:02-C*07:359-B*39:01-DRB1*04:36 and A*24:02-C*07:359-B*39:01-DRB1*04:04.

Conclusion

The two deduced HLA haplotypes associated with the uncommon C*07:359 allele that we report here are valuable for HLA tissue typing laboratories for reference purposes and for stem cell transplantation donor search coordinators to determine the likelihood of finding compatible donors in unrelated bone marrow donor registries for patients bearing the uncommon HLA allele. Since C*07:359 was found mostly in the Taiwanese indigenous population, we think the allele and its haplotypes we report here are important in population and anthropological studies.

HLA class II peptide-binding-region analysis reveals funneling of polymorphism in action

BACKGROUND

HLA-class II proteins hold important roles in key physiological processes. The purpose of this study was to compile all class II alleles reported in human population and investigate patterns in pocket variants and their combinations, focusing on the peptide-binding region (PBR).

METHODS

For this purpose, all protein sequences of DPA1, DQA1, DPB1, DQB1 and DRB1 were selected and filtered, in order to have full PBR sequences. Proportional representation was used for pocket variants while population data were also used.

RESULTS

All pocket variants and PBR sequences were retrieved and analyzed based on the preference of amino acids and their properties in all pocket positions. The observed number of pocket variants combinations was much lower than the possible inferred, suggesting that PBR formation is under strict funneling. Also, although class II proteins are very polymorphic, in the majority of the reported alleles in all populations, a significantly less polymorphic pocket core was found.

CONCLUSIONS

Pocket variability of five HLA class II proteins was studied revealing favorable properties of each protein. The actual PBR sequences of HLA class II proteins appear to be governed by restrictions that lead to the establishment of only a fraction of the possible combinations and the polymorphism recorded is the result of intense funneling based on function.

Deduced probable human leukocyte antigen haplotypes associated with human leukocyte antigen DRB1*04:36 identified by case analysis of Taiwanese individuals

Objective:

Human leukocyte antigen (HLA) DRB1*04:36 is a low-frequency HLA-DRB1 allele. The aim here is to report the ethnicity of DRB1*04:36 and its associated HLA haplotypes among Taiwanese individuals.

Materials and Methods:

A sequence-based typing method was employed to confirm this low incidence allele. Polymerase chain reaction was performed to amplify exons 2 and 3 of the HLA-A and HLA-B loci and exon 2 of the HLA-DRB1 locus using group-specific primer sets. The amplicons were sequenced in both directions using BigDye Terminator Cycle Sequencing Ready Reaction kits and the manufacturer's protocols. One group of unrelated blood donors used in this study consists of randomized individuals with Taiwanese ethnicity who participate in the Tzu Chi Bone Marrow Donor Registry and the other group are randomized unrelated individuals from mainland China. The family members in the family part of the study are volunteer blood donors.

Results:

In exon 2, the DNA sequence of DRB1*04:36 is identical to DRB1*04:03:01 except for a nucleotide segment from residue 286 to residue 308. The nucleotide segment from residue 286 to residue 308, incidentally, is identical to that of DRB1*11:01:01:01. These observations suggest that DRB1*04:36 may have been derived through a gene recombination event involving DRB1*04:03:01 and DRB1*11:01:01:01. Our family study indicated that the HLA haplotype in association with DRB1*04:36 can be deduced to be A*24:02-B*39:01-DRB1*04:36. A randomized population study using Taiwanese suggests that additional DRB1*04:36 associated HLA haplotypes seem to exist.

Conclusion:

The information on the ethnicity of the DRB1**04:36 allele, and the deduced probable HLA haplotypes associated with the low incidence DRB1*04:36 allele that we report here, is of value to HLA testing laboratories for reference purposes. In addition, they can be used by stem cell transplantation donor search coordinators to aid the creation of strategy for finding compatible donors who are part of unrelated bone marrow donor registries when a patient carries this uncommon HLA allele.