Maria Elisa Moraes

Interleukin-10 promoter single-nucleotide polymorphisms as markers for disease susceptibility and disease severity in leprosy

We have determined IL-10 promoter genotypes of five single-nucleotide polymorphisms (SNPs): T−3575A, A−2849G, C−2763A, -A−1082G and C−819T. The haplotype frequencies were defined in healthy subjects compared to leprosy patients, and analyzed for their occurrence in multi- (MB) vs paucibacillary (PB) as severe and mild forms of leprosy, respectively. Haplotypes defined by three SNP positions (−3575, −2849 and −2763) captured significant differences between controls and patients (P=0.04). The haplotype carrying −3575A, −2849G and −2763C was associated with resistance to leprosy and to the development of severe forms of the disease using either a binomial (controls vs cases, P=0.005, OR=0.35, CI=0.13–0.91) or ordinal (controls vs PB vs MB, P=0.006, OR=0.32, CI=0.12–0.83) model. By contrast, the IL-10 haplotype −3575T/−2849A/−2763C was found to be associated with susceptibility to leprosy per se (P=0.027, OR=2.37, CI=1.04–5.39), but not leprosy type. The data suggest that the IL-10 locus contributes to the outcome of leprosy.

HLA-DRB1 * 04 and DRB1 * 10 are associated with resistance and susceptibility, respectively, in Brazilian and Vietnamese leprosy patients

The host genetic background has been considered one of the factors that influence leprosy outcome, a chronic infectious disease caused by Mycobacterium leprae. Genome scans demonstrated that the 6p21 region is associated with leprosy and a substantial number of population-based studies analyzing human leukocyte antigen (HLA) class II loci suggested association of HLA-DR with leprosy. However, some studies lacked robustness as they had limited power. Indeed, experimental designs require increased sample size to achieve adequate power, as well as replication studies with independent samples for confirmation of previous findings. In this work, we analyzed the influence of the HLA-DRB1 locus on leprosy susceptibility per se and disease type using a case–control design carried out in Brazilians (578 cases and 691 controls) and a replication study based on a family design in a Vietnamese population (n=194 families). The results showed that HLA-DRB1*10 is associated with susceptibility to leprosy and HLA-DRB1*04 is associated with resistance, both in the Brazilian and Vietnamese populations suggesting that these alleles play an important role in the activation of cellular immune responses against M. leprae.

Tracking human migrations by the analysis of the distribution of HLA alleles, lineages and haplotypes in closed and open populations

The human leucocyte antigen (HLA) system shows extensive variation in the number and function of loci and the number of alleles present at any one locus. Allele distribution has been analysed in many populations through the course of several decades, and the implementation of molecular typing has significantly increased the level of diversity revealing that many serotypes have multiple functional variants. While the degree of diversity in many populations is equivalent and may result from functional polymorphism(s) in peptide presentation, homogeneous and heterogeneous populations present contrasting numbers of alleles and lineages at the loci with high-density expression products. In spite of these differences, the homozygosity levels are comparable in almost all of them. The balanced distribution of HLA alleles is consistent with overdominant selection. The genetic distances between outbred populations correlate with their geographical locations; the formal genetic distance measurements are larger than expected between inbred populations in the same region. The latter present many unique alleles grouped in a few lineages consistent with limited founder polymorphism in which any novel allele may have been positively selected to enlarge the communal peptide-binding repertoire of a given population. On the other hand, it has been observed that some alleles are found in multiple populations with distinctive haplotypic associations suggesting that convergent evolution events may have taken place as well. It appears that the HLA system has been under strong selection, probably owing to its fundamental role in varying immune responses. Therefore, allelic diversity in HLA should be analysed in conjunction with other genetic markers to accurately track the migrations of modern humans.

Alloantibodies against donor epidermis and early kidney transplant rejection

We have previously observed that transplant recipient sera with endothelial antibodies are bound to epidermal cells, as shown by immunofluorescence on sections of skin. It was also reported that early kidney failures that occurred despite negative T cell crossmatches were associated with, and could have been predicted by, a crossmatch with donor skin. Ninety patients undergoing kidney transplantation have now been evaluated using this technique. A few other patients were excluded from the analysis because of the presence of autoantibodies staining autologous skin. In 12 the crossmatch with donor skin was positive, and 9 of them had severe rejection within the first 10 days after transplantation. The three patients with a positive skin crossmatch and a benign course had not been tested with autologous skin and therefore autoantibodies could not be excluded. Only 7 of the 78 patients with negative skin crossmatches had early rejection. The correlation between skin crossmatch and early rejection was statistically highly significant (P less than 0.0001). Studies by flow cytometry have shown that these antigens are found on the surface of epidermal and endothelial cells, and are modulated by gamma interferon. When tested against a panel of skin donors, skin alloantibodies gave different patterns of positive and negative reactions, suggesting polymorphism.

HLA imputation in an admixed population: An assessment of the 1000 Genomes data as a training set.

Methods to impute HLA alleles based on dense single nucleotide polymorphism (SNP) data provide a valuable resource to association studies and evolutionary investigation of the MHC region. The availability of appropriate training sets is critical to the accuracy of HLA imputation, and the inclusion of samples with various ancestries is an important pre-requisite in studies of admixed populations. We assess the accuracy of HLA imputation using 1000 Genomes Project data as a training set, applying it to a highly admixed Brazilian population, the Quilombos from the state of São Paulo. To assess accuracy, we compared imputed and experimentally determined genotypes for 146 samples at 4 HLA classical loci. We found imputation accuracies of 82.9%, 81.8%, 94.8% and 86.6% for HLA-A, -B, -C and -DRB1 respectively (two-field resolution). Accuracies were improved when we included a subset of Quilombo individuals in the training set. We conclude that the 1000 Genomes data is a valuable resource for construction of training sets due to the diversity of ancestries and the potential for a large overlap of SNPs with the target population. We also show that tailoring training sets to features of the target population substantially enhances imputation accuracy.

HLA in Brazilian Ashkenazic Jews with chronic dermatophytosis caused by Trichophyton rubrum

The frequency of HLA (Human Leucocyte Antigens) was analyzed in 25 non-consanguineous Brazilian Ashkenazic Jews, resident in the city of Sao Paulo, Brazil, suffering from chronic dermatophytosis caused by T. rubrum, and in 25 non-infected individuals belonging to the same ethnic group. Statistically significant values (p<0.05) were observed for HLA-B14 associated with resistance to chronic dermatophytosis and HLA-DQB1*06 (p=0.05) possibly related to susceptibility. These findings suggest that genes on the chromosome 6, in the region of the major histocompatibility complex, may influence the development of chronic dermatophytosis.

Seleção de doador de medula óssea ou sangue periférico

A compatibilidade HLA e o fator mais valorizado na escolha do doador de medula ossea voluntario, preconizando-se a realizacao de HLA de alta resolucao nos locos HLA-A,B,C, DRB1 e DQB1. Tem sido dado preferencia para o doador com consanguinidade alelica 8x8 (A,B,C, DRB1). Na presenca de incompatibilidade na classe-I sugere-se a busca de doador com compatibilidade DQB1 (9x10). Ja as incompatibilidades dos locos DPB1 nao constituem criterio de exclusao de doador, exceto quando existir presenca de anticorpo contra o loco HLA-DP do doador.

Population variation of HLA genes in rural communities in Brazil, the Quilombos from the Vale do Ribeira, São Paulo – Brazil

In the present study, we characterized the allelic and haplotypic profile of the genes HLA-A, -B, -C and -DRB1 (PCR-SBT) in a population sample of 144 highly admixed individuals, coming from rural communities in Brazil (Quilombos from Vale do Ribeira, in the State of São Paulo). Furthermore, we identified three individuals with a new null allele in the HLA-C gene (HLA-C(∗)02:105N), associated with the haplotype HLA-A(∗)80: 01∼B(∗)18: 01:01G∼DRB1(∗) 07:01.

Determination of an unrelated donor pool size for human leukocyte antigen-matched platelets in Brazil

Background Successful transfusion of platelet refractory patients is a challenge. Many potential donors are needed to sustain human leukocyte antigen matched-platelet transfusion programs because of the different types of antigens and the constant needs of these patients. For a highly mixed population such as the Brazilian population, the pool size required to provide adequate platelet support is unknown. Methods A mathematical model was created to estimate the appropriate size of an unrelated donor pool to provide human leukocyte antigen-compatible platelet support for a Brazilian population. A group of 154 hematologic human leukocyte antigen-typed patients was used as the potential patient population and a database of 65,500 human leukocyte antigen-typed bone marrow registered donors was used as the donor population. Platelet compatibility was based on the grading system of Duquesnoy. Results Using the mathematical model, a pool containing 31,940, 1710 and 321 donors would be necessary to match more than 80% of the patients with at least five completely compatible (no cross-reactive group), partial compatible (one cross-reactive group) or less compatible (two cross-reactive group) donors, respectively. Conclusion The phenotypic diversity of the Brazilian population has probably made it more difficulty to find completely compatible donors. However, this heterogeneity seems to have facilitated finding donors when cross-reactive groups are accepted as proposed by the grading system of Duquesnoy. The results of this study may help to establish unrelated human leukocyte antigen-compatible platelet transfusions, a procedure not routinely performed in most Brazilian transfusion services.

Nomenclature for factors of the HLA system.

The Nomenclature Committee for Factors of the HLA System of the World Health Organization standardizes the nomenclature of the HLA system and meets regularly during the International Histocompatibility Workshops. During the 15th International Histocompatibility Workshop in Buzios (RJ), Brazil, in September 2008, there was a meeting of the nomenclature committee when new rules were established, which were implemented in April 2010.A Nomenclature Committee composed of geneticists and immunologists, including specialists in tissue typing, has met after each of the Histocompatibility Workshops beginning with the Third Workshop in 1967. The Committee, in part under the auspices of the World Health Organization and the International Union of Immunological Societies (WHO/IUIS), met after the Sixth Workshop in Aarhus in July 1975. The expanding knowledge of the genetics of the major histocompatibility system of man has necessitated a revision of the terminology for the HLA region following the principles established in previous reports. This has been done with as few changes as possible.