Novel 6p21.3 Risk Haplotype Predisposes to Acute Coronary Syndrome

Abstract

Background-The HLA-DRB1*01 allele of the human leukocyte antigen has been associated with acute coronary syndrome.Genome-wide association studies have revealed associations with human leukocyte antigen and non-human leukocyte antigen genes of 3 major histocompatibility complex gene classes but not at allelic level. Methods and Results-We conducted a large-scale genetic analysis on a case-control cohort comprising 5376 acute coronary syndrome cases and 4852 unrelated controls from 4 populations of 2 European countries. We analyzed the risk candidate allele of HLA-DRB1*01 by genomic real-time polymerase chain reaction together with high-density single nucleotide polymorphisms of the major histocompatibility complex to precisely identify risk loci for acute coronary syndrome with effective clinical implications. We found a risk haplotype for the disease containing single nucleotide polymorphisms from BTNL2 and HLA-DRA genes and the HLA-DRB1*01 allele. The association of the haplotype appeared in 3 of the 4 populations, and the direction of the effect was consistent in the fourth. Coronary samples from subjects homozygous for the disease-associated haplotype showed higher BTNL2 mRNA levels (r=0.760; P<0.00001).We localized, with immunofluorescence staining, BTNL2 in CD68-positive macrophages of the coronary artery plaques. In homozygous cases, BTNL2 blocking, in T-cell stimulation assays, enhanced CD4 10,11 This may explain why the HLA-DRB1*01 association has emerged only in studies with direct HLA allele typing, but in no GWA studies.2,4 HLA-DRB1*01 may play a role in promoting coronary artery disease by affecting antigen presentation.12 Presentation of peptide fragments of oxidized low-density lipoprotein cholesterol may connect the cholesterol pathway to inflammation and immunology in atherosclerosis progression. Clinical Perspective on p 63Because of the promising results from previous GWA and candidate gene studies and the fact that the MHC contains many genes with putative immune functions, we hypothesized that analysis of other MHC genes using high-density SNPs stratified according to the HLA-DRB1*01 allele will show novel associations with acute coronary syndrome (ACS) with effective clinical implications. Materials and Methods Patient PopulationsOur entire study comprised 1 discovery population (from Finland) and 3 replication populations (I and II from Finland and III from Spain) for a total of 5376 cases and 4852 control subjects. The discovery population included 2090 ACS cases. 13 Replication population I included 742 cases either with ST-elevation myocardial infarction or non-ST-elevation myocardial infarction.14 Replication population II included 762 either ST-elevation myocardial infarction or non-STelevation myocardial infarction cases. 15 Replication population III included 1768 first myocardial infarction cases. 16,17 Control subjects for discovery and replication populations I and II were selected from The National FINRISK Study (FINRISK) 1992(FINRISK) , 1997(FINRISK) , 2002(FINRISK) , and ...

The complexity and diversity of major histocompatibility complex challenge disease association studies

“…Considering the genetic architecture of the region, also non‐HLA genes and more subtle genetic polymorphisms such as SNPs and copy number variation may play an important part in the haplotype structure and function. HLA‐SNP haplotypes have been only very recently studied …”

“…The conformation of HLA‐DRB1*01 presenting immunodominant autoreactive peptide prefers interaction with regulatory T cells. In coronary artery disease, the increased disease risk mediated by HLA‐DRB1*01 was linked with BTNL2 and their inhibitory effect on regulatory T cell proliferation …”

“…HLA-SNP haplotypes have been only very recently studied. 25,26 In a given population, the observed haplotypes are extremely polymorphic and are present in variable frequencies between different geographical regions. Usually, there are a relatively small number of common, conserved haplotypes and a very large number of rare haplotypes (Table 3), making the disease association studies challenging.…”

“…69 We have challenged the drawbacks of the HLA-DRB1 imputation in combining GWA SNP results with the allele copy numbers of HLA-DRB1*01 determined by genomic quantitative polymerase chain reaction (PCR) as a priori candidate gene associated with the complex disease of coronary artery disease. 26 However, combining SNP results with HLA-typing results has just started to be acknowledged by the GWA research community. 25 In T1D, a connection between protective HLA class II expression and the intestinal microbiome has been found.…”

“…In coronary artery disease, the increased disease risk mediated by HLA-DRB1*01 was linked with BTNL2 and their inhibitory effect on regulatory T cell proliferation. 26,[70][71][72] 5.1 | MHC is a strong risk factor for type 1 diabetes…”