RESUMO
Background: Rheumatic heart disease (RHD) after group A streptococcus (GAS) infections is heritable and prevalent in Indigenous populations. Molecular mimicry between human and GAS proteins triggers proinflammatory cardiac valve-reactive T cells. Methods: Genome-wide genetic analysis was undertaken in 1263 Aboriginal Australians (398 RHD cases; 865 controls). Single-nucleotide polymorphisms were genotyped using Illumina HumanCoreExome BeadChips. Direct typing and imputation was used to fine-map the human leukocyte antigen (HLA) region. Epitope binding affinities were mapped for human cross-reactive GAS proteins, including M5 and M6. Results: The strongest genetic association was intronic to HLA-DQA1 (rs9272622; P = 1.86 × 10-7). Conditional analyses showed rs9272622 and/or DQA1*AA16 account for the HLA signal. HLA-DQA1*0101_DQB1*0503 (odds ratio [OR], 1.44; 95% confidence interval [CI], 1.09-1.90; P = 9.56 × 10-3) and HLA-DQA1*0103_DQB1*0601 (OR, 1.27; 95% CI, 1.07-1.52; P = 7.15 × 10-3) were risk haplotypes; HLA_DQA1*0301-DQB1*0402 (OR 0.30, 95%CI 0.14-0.65, P = 2.36 × 10-3) was protective. Human myosin cross-reactive N-terminal and B repeat epitopes of GAS M5/M6 bind with higher affinity to DQA1/DQB1 alpha/beta dimers for the 2-risk haplotypes than the protective haplotype. Conclusions: Variation at HLA_DQA1-DQB1 is the major genetic risk factor for RHD in Aboriginal Australians studied here. Cross-reactive epitopes bind with higher affinity to alpha/beta dimers formed by risk haplotypes, supporting molecular mimicry as the key mechanism of RHD pathogenesis.
Assuntos
Predisposição Genética para Doença , Estudo de Associação Genômica Ampla , Antígenos HLA/genética , Mimetismo Molecular , Cardiopatia Reumática/genética , Cardiopatia Reumática/imunologia , Infecções Estreptocócicas/genética , Infecções Estreptocócicas/imunologia , Austrália , Proteínas da Membrana Bacteriana Externa/imunologia , Reações Cruzadas/imunologia , Epitopos/imunologia , Genótipo , Antígenos HLA/imunologia , Antígenos HLA-DQ/química , Antígenos HLA-DQ/classificação , Antígenos HLA-DQ/genética , Antígenos HLA-DQ/imunologia , Cadeias alfa de HLA-DQ/química , Cadeias alfa de HLA-DQ/classificação , Cadeias alfa de HLA-DQ/genética , Cadeias alfa de HLA-DQ/imunologia , Haplótipos , Humanos , Miosinas/imunologia , Razão de Chances , Polimorfismo de Nucleotídeo Único/genética , Cardiopatia Reumática/microbiologia , Fatores de Risco , Streptococcus/patogenicidadeRESUMO
The major histocompatibility complex is one of the best studied systems in vertebrates providing evidence for the long-term action of selection. Here, we examined the intra- and inter-population genetic diversity of the MHC class II DRB locus in European brown hare (Lepus europaeus) and correlated the results with genetic variability already estimated from the MHC DQA locus and from maternally (mitochondrial DNA (mtDNA)) and biparentally (allozymes, microsatellites) inherited loci. L. europaeus showed remarkable genetic polymorphism in both DQA and DRB1 loci. The Anatolian populations exhibited the highest genetic polymorphism for both loci. Balancing selection has established increased variability in the European populations despite the founder effects after the last glaciation. Different evolutionary rates were traced for DRB1 and DQA loci, as evidenced by the higher number of common DRB1 than DQA alleles and the greater differences between DRB1 alleles with common origin in comparison with DQA alleles. The high number of rare alleles with low frequencies detected implies that frequency-dependent selection drives MHC evolution in the brown hare through the advantage of rare alleles. Both loci were under the influence of positive selection within the peptide-binding region. The functional polymorphism, recorded as amino acid substitutions within the binding pockets, fell also within distinct geographic patterns, yet it was much narrower than the genetic polymorphism. We hypothesize that certain structural and functional characteristics of the binding pockets set limitations to the actual shape of genetic polymorphism in MHC.
Assuntos
Variação Genética/imunologia , Cadeias alfa de HLA-DQ/genética , Cadeias HLA-DRB1/genética , Lebres/genética , Filogenia , Alelos , Animais , DNA Mitocondrial/genética , DNA Mitocondrial/imunologia , Europa (Continente) , Evolução Molecular , Frequência do Gene , Cadeias alfa de HLA-DQ/classificação , Cadeias alfa de HLA-DQ/imunologia , Cadeias HLA-DRB1/classificação , Cadeias HLA-DRB1/imunologia , Lebres/imunologia , Padrões de Herança , Repetições de Microssatélites/imunologia , FilogeografiaRESUMO
The human leukocyte antigen (HLA) system has a major role in the regulation of the immune response as it is involved in the defense against pathogens. Some studies have reported that HLA class II genes play a strong role in severe cases of pulmonary tuberculosis (PTB) in several populations. Thus the aim of the study was to compare the HLA-class II alleles of patients with drug resistant tuberculosis with those of healthy controls from the same ethnic group in Kazakhstan. The aim of the present study was to evaluate the correlation of HLA-class II alleles by patients with drug resistant tuberculosis and the healthy controls of the same ethnic group in Kazakhstan. The HLA-class II alleles of 76 patients with tuberculosis (TB) and 157 healthy volunteers were investigated using sequence-based typing (SBT)-method. HLA-DQA1*03:02 HLA-DRB1*08:01 and DRB1*08:03 occurred more frequently (P = 0.05) in patients with drug resistant tuberculosis than in controls. We observed a possible association between certain HLA alleles and TB that are specific for the Kazakh population. Further studies are needed to confirm our findings using a larger number of patients with drug resistant tuberculosis.
