HLA-A, B and C markers in the Portuguese population

HLA-A, -B, and -DRB1 allele and haplotype diversity in a cohort of Brazilian renal transplant candidates

The distribution of organs for renal transplant depends on HLA matching between donor and recipient. This study aimed to characterize the allele and haplotype frequencies of HLA-A, -B, and -DRB1 in a cohort of renal transplant candidates populations in the region of Sao José do Rio Preto (State of São Paulo), to compare the allele frequencies between Caucasian and Black in that region, as well as to compare these frequencies with different Brazilian populations reported. The HLA-A, -B, and -DRB1 allele and haplotypes frequencies were analyzed in a sample of 2.624 individuals and classified according to the ethnic group (2.347 Caucasians and 277 Blacks). The HLA class I (A, B) and class II (DRB1) specificities were determined by complement-dependent microlymphocytotoxic (CDC) and Polymerase Chain Reaction/Sequence Specific Priming (PCR-SSP) methods, respectively. Twenty-one HLA-A, 34 HLA-B and 13 HLA-DRB1 allelic groups were identified. The most frequent alleles for each locus were HLA-A(∗)02, HLA-B(∗)35, and HLA-DRB1(∗)11. The most frequent haplotypes found were A(∗)01 B(∗)08 DRB1(∗)03 among Caucasians and A(∗)29 B(∗)15 DRB1(∗)04 among Blacks. The most common alleles for each locus among RTx were HLA-A(∗)02, HLA-B(∗)35 and HLA-DRB1(∗)11. The haplotypes A(∗)01 B(∗)08 DRB1(∗)03 and A(∗)29 B(∗)44 DRB1(∗)07 prevailed among Caucasians and Blacks, respectively. This study provides the first data on the HLA-A, HLA-B and HLA-DRB1 allele and haplotype frequencies of renal transplant candidates populations in the region of Sao José do Rio Preto.

HLA-A, HLA-B, and HLA-DRB1 Allele and Haplotype Frequencies in Renal Transplant Candidates in a Population in Southern Brazil

BACKGROUND

Very few studies have examined the diversity of human leukocyte antigens (HLA) in the Brazilian renal transplant candidates.

METHODS

The frequencies of the HLA-A, HLA-B, and HLA-DRB1 alleles, haplotypes and phenotypes were studied in 522 patients with chronic renal failure, renal transplant candidates, registered at the Transplant Centers in north/northwestern Paraná State, southern Brazil. Patients were classified according to the ethnic group (319 whites [Caucasians], 134 mestizos [mixed race descendants of Europeans, Africans, and Amerindians; browns or "pardos"] and 69 blacks). The HLA typing was performed by the polymerase chain reaction sequence-specific oligonucleotide method (PCR-SSO), combined with Luminex technology.

RESULTS

In the analysis of the total samples, 20 HLA-A, 32 HLA-B, and 13 HLA-DRB1 allele groups were identified. The most frequent allele groups for each HLA locus were HLA-A*02 (25.4%), HLA-B*44 (10.9%), and HLA-DRB1*13 (13.9%). The most frequent haplotypes were HLA-A*01-B*08-DRB1*03 (2.3%), A*02-B*44-DRB1*07 (1.2%), and A*03-B*07-DRB1*11 (1.0%). Significant differences (P < 0.05) were observed in the HLA-A*68, B*08, and B*58 allele frequencies among ethnic groups.

CONCLUSIONS

This study provides the first data on the HLA-A, HLA-B, and HLA-DRB1 allele, phenotype and haplotype frequencies of renal transplant candidates in a population in southern Brazil.

Rio Grande do Norte, Brazil, voluntary bone marrow donors registry analysis

Objective: this study aimed to report the allele and haplotype frequencies of volunteer bone marrow donors (VBMD) from the state of Rio Grande do Norte (RN) who were enrolled in the Brazilian Volunteer Bone Marrow Donor Registry (REDOME). Methods: the sample comprised 12,973 VBMD who had their allele and haplotype frequencies calculated by Arlequin 3.5.1.2. A multivariate analysis of the data was obtained through a principal component analysis (PCA) and hierarchical cluster analysis (HCA) performed with SPSS 8.0. Results: the most frequent allelic group was HLA-A*02, followed by -DRB1*13, -DRB1*04, -DRB1*07, -B*44, -B*35, -A*24 and -DRB1*01. Of the 2,701 haplotypes observed, the three most frequent were HLA-A*01 B*08 DRB1*03 (1.62%), -A*29 B*44 DRB1*07 (1.56%) and -A*02 B*44 DRB1*04 (1.29%). These haplotypes were in linkage disequilibrium. RN allele and haplotype frequencies were very similar to those in other Brazilian states in which similar studies have been performed. The PCA revealed that RN is highly genetically similar to Caucasian populations, especially those from Iberian countries, which strongly influenced the state’s ethnic composition. Africans and Amerindians also influenced the RN population structure, to a lesser extent. Conclusion: the HCA reinforced the conclusion that, despite its highly admixed profile, the RN population is genetically similar to European and European-descended populations. The PCA also showed that RN cities do not contribute to the same extent to REDOME, with less populous cities being underrepresented, indicating the need to enroll more VBMD from these smaller cities to faithfully depict the state’s population structure in the database.

Frequencies of allele groups HLA-A, HLA-B and HLA-DRB1 in a population from the northwestern region of São Paulo State, Brazil

The aim of this study was to estimate the HLA-A, HLA-B and HLA-DRB1 allele groups frequencies in a population of 1559 volunteer bone marrow donors from the northwestern region of São Paulo State grouped according to ethnicity. An additional objective was to compare the allele frequencies of the current study with data published for other Brazilian populations. The allele groups were characterized by the PCR-rSSO method using Luminex(®) technology. Twenty HLA-A, 32 HLA-B and 13 HLA-DRB1 allele groups were identified. The most common allele groups in European descent and mixed African and European descent samples were HLA-A*02, HLA-B*35 and HLA-DRB1*13, while HLA-A*02, HLA-B*35 and HLA-DRB1*11 were more common in African descent samples. The HLA-A*23, HLA-A*36, HLA-B*58 and HLA-B*81 allele groups were more common in sample from African descent than European descent, and the HLA-DRB1*08 was more common in mixed African and European descent than in European descent. Allele group frequencies were compared with samples from other Brazilian regions. The HLA-A*30 and HLA-A*23 were more common in this study than in the populations of Rio Grande do Sul and Paraná; and the HLA-A*01, HLA-B*18, HLA-B*57 and HLA-DRB1*11 were more common in this study than in the population of Piauí. The least frequent allele groups were HLA-A*31, HLA-B*15, HLA-B*40 and HLA-DRB1*08 for the population of Piauí, HLA-A*01 and HLA-A*11 for Parana, HLA-A*02 and -A*03 for Rio Grande do Sul and HLA-DRB1*04 for Paraná, Rio Grande do Sul and Piauí. These data provide an overview on the knowledge on HLA diversity in the population of the northwestern region of São Paulo State and show that the genes of this system are useful to distinguish different ethnic groups.

Evaluation of the humoral immune response to human leukocyte antigens in Brazilian renal transplant candidates

Pre-transplant sensitization to human leukocyte antigens (HLA) is a risk factor for graft failure. Studies of the immunological profile related to anti-HLA antibodies in Brazilian renal transplant candidates are few. In this study, we evaluated the humoral immune response to HLA antigens in 269 renal transplant candidates, in Paraná State, Brazil. The HLA typing was performed by the polymerase chain reaction sequence-specific oligonucleotide method (PCR-SSO) combined with Luminex technology, using an SSO-LABType commercial kit (One Lambda, Inc., Canoga Park, CA, USA). The percentages of panel-reactive antibodies (PRA) and the specificity of anti-HLA antibodies were determined using the LS1PRA and LS2PRA commercial kits (One Lambda, Inc.). The PRA-positive group consisted of 182 (67.7%) patients, and the PRA-negative group of 87 (32.3%) patients. The two groups differed significantly only with respect to gender. Females were the most sensitized. Among the 182 patients with PRA- positive, 62 (34.1%) were positive for class I and negative for class II, 39 (21.4%) were negative for class I and positive for class II, and 81 (44.5%) were positive for both classes I and II. The HLA-A*02, A*24, A*01, B*44, B*35, B*15, DRB1*11, DRB1*04 and DRB1*03 allele groups were the most frequent. The specificities of anti-HLA antibodies were more frequent: A34, B57, Cw15, Cw16, DR51, DQ8 and DP14. This study documented the profile of anti-HLA antibodies in patients with chronic renal failure who were on waiting lists for an organ in Paraná, and found high sensitization to HLA antigens in the samples.

HLA-A, HLA-B and HLA-DRB1 haplotype frequencies in Piauí's volunteer bone marrow donors enrolled at the Brazilian registry

This study aimed to report the antigen and haplotype frequencies (HFs) of volunteer bone marrow donors (VBMDs) from the state of Piauí who were enrolled in the National Volunteer Bone Marrow Donor Registry (REDOME). The research subjects were 21,943 volunteer bone marrow donors, predominantly young adult women (53.3%). The most frequent allelic group was HLA-A2, followed by -DRB1*13, -DRB1*04, -DRB1*07, -B*15, -B∗35, -B*44, -A*24 and -A*03. Of the 2,704 haplotypes observed, the three most frequent haplotypes were A*29 B*44 DRB1*07 (1.45%), A*01 B*08 DRB1*03 (1.4%) and A*03 B*07 DRB1*15 (0.92%). These three haplotypes were in linkage disequilibrium. PCA showed that 98% of the VBMDs have HLA allele frequencies that are very similar to those from Teresina, the capital city of Piauí. According to the PCA results, these municipalities are distributed with a close proximity to Teresina, which in turn has a close genetic proximity to the Hispanic ethnicity, intermediate proximity to Caucasians and Africans and a distant kinship to Amerindians. The hierarchical proximity of the population of Piauí to the Portuguese and Hispanic populations to shows the strong influence of the latter on the former.

HLA-A, -B, and -DRB1 allelic and haplotypic diversity in a sample of bone marrow volunteer donors from Rio Grande do Sul State, Brazil

The HLA A, B, and DRB1 allele, phenotype, and haplotype frequencies were studied in a sample of 5,000 volunteer bone marrow donors registered at the Brazilian Volunteer Bone Marrow Donor Registry. The participants live in the state of Rio Grande do Sul and were classified according to ethnic group (4,428 Caucasians, 324 mestizos [mixed race], and 248 blacks). Typing was performed using the polymerase chain reaction sequence-specific oligonucleotide method combined with Luminex technology. Twenty-one HLA-A, 33 HLA-B, and 13 HLA-DRB1 allele groups were identified. The most frequent allele groups for each locus were A*02, B*35, and DRB1*13. The most frequent haplotypes were A*01 B*08 DRB1*03 in Caucasians and mestizos and A*02 B*15 and DRB1*04 in blacks. The allele frequencies were compared with samples from different Brazilian regions. In most comparisons no significant differences were found. The most significant differences were observed in the comparison of the groups of our sample, indicating that human leukocyte antigen (HLA) is a good marker to distinguish among people from different ethnic groups. The data provide insight on the knowledge of HLA diversity in the population of Rio Grande do Sul and in the search for a better match for transplant.

Linkage disequilibrium between S65C HFE mutation and HLA A29-B44 haplotype in Terceira Island, Azores

Our objective was to investigate the frequency of HFE gene mutations and to study linkage disequilibrium (LD) between HLA-Class I alleles and these mutations in the population of Terceira Island, Azores, Portugal. A total of 218 unrelated individuals were investigated. Three HFE mutations--C282Y, H63D, and S65C--were identified by restriction endonuclease digestion of polymerase chain reaction (PCR)-amplified genomic DNA. HLA-Class I alleles were typed by PCR-single-strand polymorphism. Gene frequencies and LD were estimated using Arlequin V 1.1. Six genotypes were found in the population: WT/WT (58.3%), H63D/WT (31.2%), H63D/H63D (2.3%), H63D/C282Y (0.9%), S65C/WT (4.1%), and C282Y/WT (3.2%). No cases of C282Y or S65C homozygosity were identified. HLA haplotype A3-B7 was in LD with C282Y; HLA alleles A29, B44, and HLA haplotype A29-B44 were in LD with S65C mutation. HFE gene frequencies in this population are similar to those in other European populations; HFE S65C mutation was found in LD with the alleles A29, B44, and with A29-B44 HLA haplotype.

The HLA polymorphism in five Brazilian populations

A total of 977 White individuals living in five Brazilian cities, as well as 173 Black individuals from two of these cities have been studied in relation to HLA-A and HLA-B. Allele frequency similarities among these populations are much more impressive than dissimilarities, and the differences, considering putative ancestors, are not remarkable. This limited variability can be only partially explained in terms of racial admixture, estimates of the latter using different alleles in the various populations showing disparate results. Linkage disequilibrium values vary between groups, that for A1-B8 being the most consistent, independent of sample or race. But four other haplotypes observed to be in significant disequilibrium in Portugal showed the same pattern in at least one of the five Brazilian White samples.

HLA-A,B,C and DR antigens in a sample of the Tunisian population

The HLA-A, B and DR phenotypes of 109 unrelated Tunisian individuals have been determined. The HLA-A and B antigen frequencies were compared with data reported for European Caucasoids and various Arab populations. Most similarities in antigen frequencies were seen between Tunisians and Kabyles from North Africa. A high frequency of HLA-A23 and HLA-Bw50 was observed in Tunisians and all Arab populations. A very close similarity in HLA-DR antigen frequencies exists between Tunisians and European Caucasoids. Linkage disequilibria between alleles of HLA loci were examined; many instances of previously reported antigen associations were seen in Tunisians, together with a number of associations which have not been described elsewhere. Aw34B8 and A2DRw14 are suggested as being common haplotypes in Tunisians.