HLA-A, -B, -C, -DQA1, -DQB1, -DRB1, -E, -F and -G genotyping of 130 individuals from Terceira Island, Azores, Portugal

Association Study Identified HLA-DQA1 as a Novel Genetic Risk of Systemic Lupus Erythematosus-Associated Pulmonary Arterial Hypertension

OBJECTIVE

Pulmonary arterial hypertension (PAH) is a severe complication of systemic lupus erythematosus (SLE). However, the genetic signatures of SLE-associated PAH have not been well studied. We aimed to identify genetic variants implicated in SLE-associated PAH susceptibility within the major histocompatibility complex (MHC) region and assess the contribution to clinical outcomes.

METHODS

A total of 172 patients with SLE-associated PAH confirmed by right heart catheterization, 1,303 patients with SLE without PAH, and 9,906 healthy controls were included. Deep sequencing of the MHC region was performed to identify alleles, single-nucleotide polymorphisms, and amino acids. We compared patients with SLE-associated PAH with patients with SLE without PAH and healthy controls. Clinical association study was conducted to explore the contribution to phenotypes.

RESULTS

A total of 19,881 genetic variants were identified within the MHC region. HLA-DQA1*03:02 was identified as a novel genetic variant associated with SLE-associated PAH in the discovery cohort (P = 5.68 × 10-12 ) and authenticated in an independent replication cohort (P = 1.30 × 10-9 ). The strongest associated amino acid position was mapped to HLA-DQα1 in the region affecting MHC/peptide-CD4+ T cell receptor affinity and antigen binding. Clinical association study demonstrated that patients with SLE-associated PAH with HLA-DQA1*03:02 had significantly lower rates of target role achievement (P = 0.005) and survival (P = 0.04).

CONCLUSION

This study, based on the largest cohort of SLE-associated PAH, is the first to investigate how MHC region genetic variants contribute to SLE-associated PAH susceptibility. HLA-DQA1*03:02 is a novel genetic risk factor and a prognostic factor in SLE-associated PAH. Patients with SLE with this allele require regular monitoring and careful follow-up for early diagnosis and interventions for potential PAH.

High-resolution characterization of 12 classical and non-classical HLA loci in Southern Brazilians

The human leukocyte antigen (HLA) are the most polymorphic genes in the human genome. Because of their importance for antigen recognition, HLA molecules play a central role in host defense and graft rejection upon transplantation. The aim of this study was to characterize allelic diversity of the classical HLA genes HLA-A, -B, -C, -DRA, -DRB1, -DQA1, -DQB1, -DPA1, -DPB1, and the non-classical class I genes HLA-E, -F and -G at high-resolution for a population of predominantly European ancestry from Curitiba, Brazil. Genotyping of 108 individuals was performed by next-generation sequencing on the MiSeq platform and also by Sanger sequencing. The genotype distributions of all loci were in accordance with Hardy-Weinberg equilibrium (P > 0.05) and a total of 202 HLA variants at second field resolution were observed for the 12 loci. The strongest linkage disequilibrium (r² = 1.0, P < 10^-5 ) was observed for the following pairs of alleles: HLA-B*42:01:01 ~ HLA-DRB1*03:02:01; HLA-B*14:02:01 ~ HLA-C*08:02:01; B*42:01:01 ~ HLA-C*17:01:01; HLA-DRB1*03:01:01 ~ HLA-DQB1*02:01:01 ~ DRB1*03:01:01 ~ HLA-DQB1*02:01:01; DRB1*13:01:01~ HLA-DQB1*06:03:01 and HLA-DRB1*09:01:02 ~ HLA-DQA1*03:02. This is the first study to characterize all 12 HLA genes at high resolution in a single population. On the basis of the allelic frequencies of worldwide populations and principal component analysis, we confirmed the similarity of the study population to European and other Euro-descendant populations.