[Determination of HLA-A, -B and -DRB1 polymorphism in brain dead organ donors representative of the Colombian general population, 2007-2014]

Distributions of the HLA-A, HLA-B, HLA-C, HLA-DRB1, and HLA-DQB1 alleles and haplotype frequencies of 1763 stem cell donors in the Colombian Bone Marrow Registry typed by next-generation sequencing

The HLA compatibility continues to be the main limitation when finding compatible donors, especially if an identical match is not found within the patient's family group. The creation of bone marrow registries allowed a therapeutic option by identifying 10/10 compatible unrelated donors (URD). However, the availability and frequency of haplotypes and HLA alleles are different among ethnic groups and geographical areas, increasing the difficulty of finding identical matches in international registries. In this study, the HLA-A, -B, -C, -DRB1, and -DQB1 loci of 1763 donors registered in the Colombian Bone Marrow Registry were typed by next-generation sequencing. A total of 52 HLA-A, 111 HLA-B, 41 HLA-C, 47 HLA-DRB1, and 20 HLA-DQB1 alleles were identified. The 3 most frequent alleles for each loci were A*24:02g (20,8%), A*02:01g (16,1%), A*01:01g (7.06%); B*35:43g (7.69%), B*40:02g (7.18%), B*44:03g (6.07%); C*04:01g (15.40%), C*01:02g (10.49%), C*07:02g (10.44%); DRB1*04:07g (11.03%), DRB1*07:01g (9.78%), DRB1*08:02g (6.72%); DQB1*03:02g (20.96%), DQB1*03:01g (17.78%) and DQB1*02:01g (16.05%). A total of 497 HLA-A-C-B-DRB1-DQB1 haplotypes were observed with a frequency greater than or equal to 0.05% (> 0.05%); the haplotypes with the highest frequency were A*24:02g~B*35:43g~C*01:02g~DQB1*03:02g~DRB1*04:07g (3.34%), A*29:02g~B*44:03g~C*16:01g~DQB1*02:01g~DRB1*07:01g (2.04%), and A*01:01g~B*08:01g~C*07:01g~DQB1*02:01g~DRB1*03:01g (1.83%). This data will allow the new Colombian Bone Marrow Donor Registry to assess the genetic heterogeneity of the Colombian population and serve as a tool of interest for future searches of unrelated donors in the country.

Functional Profile of CD8+ T-Cells in Response to HLA-A*02:01-Restricted Mutated Epitopes Derived from the Gag Protein of Circulating HIV-1 Strains from Medellín, Colombia

CD8⁺ T-cells play a crucial role in the control of HIV replication. HIV-specific CD8⁺ T-cell responses rapidly expand since the acute phase of the infection, and it has been observed that HIV controllers harbor CD8⁺ T-cells with potent anti-HIV capacity. The development of CD8⁺ T-cell-based vaccine against HIV-1 has focused on searching for immunodominant epitopes. However, the strong immune pressure of CD8⁺ T-cells causes the selection of viral variants with mutations in immunodominant epitopes. Since HIV-1 mutations are selected under the context of a specific HLA-I, the circulation of viral variants with these mutations is highly predictable based on the most prevalent HLA-I within a population. We previously demonstrated the adaptation of circulating strains of HIV-1 to the HLA-A*02 molecule by identifying mutations under positive selection located in GC9 and SL9 epitopes derived from the Gag protein. Also, we used an in silico prediction approach and evaluated whether the mutations found had a higher or lower affinity to the HLA-A*02. Although this strategy allowed predicting the interaction between mutated peptides and HLA-I, the functional response of CD8⁺ T-cells that these peptides induce is unknown. In the present work, peripheral blood mononuclear cells from 12 HIV-1⁺ HLA-A*02:01⁺ individuals were stimulated with the mutated and wild-type peptides derived from the GC9 and SL9 epitopes. The functional profile of CD8⁺ T-cells was evaluated using flow cytometry, and the frequency of subpopulations was determined according to their number of functions and the polyfunctionality index. The results suggest that the quality of the response (polyfunctionality) could be associated with the binding affinity of the peptide to the HLA molecule, and the functional profile of specific CD8⁺ T-cells to mutated epitopes in individuals under cART is maintained.

Using next-generation sequencing for characterising HLA-DRB1 and DQB1 loci in a cohort of Colombian women

The Colombian population is characterised by a high genetic diversity, secondary to the ethnic mixture arising from colonisation. Unfortunately, few reports are available regarding HLA-DRB1 and DQB1 diversity in Colombia to date. HLA-DRB1 and DQB1 diversity was identified in this study using next-generating sequencing (NGS) on a cohort of Colombian women. Cervical samples taken from 276 women were used for typing DRB1 and DQB1 loci by Illumina MiSeq. Allele and haplotype frequencies were calculated using an expectation-maximisation algorithm. Hardy-Weinberg Equilibrium and linkage disequilibrium (LD) between loci were evaluated. Forty-seven DRB1 alleles and 14 DQB1 alleles were identified. DRB1*04:07:01G and DQB1*03:02:01G alleles occurred most frequently in the target population. Significant LD was found in 44 out of the 144 identified haplotypes, within which DRB1*04:07:01G-DQB1*03:02:01G occurred most frequently (6.56%). The alleles and haplotypes found with NGS agreed with that found in previous reports involving lower resolution for the Colombian population, and greater genetic variability was found, especially concerning DRB1. Comparing allele and haplotype frequency distribution in the target population to that of other populations denoted HLA system intra- and inter-population diversity.