SNP-Density Crossover Maps of Polymorphic Transposable Elements and HLA Genes Within MHC Class I Haplotype Blocks and Junction

The genomic region (~4 Mb) of the human major histocompatibility complex (MHC) on chromosome 6p21 is a prime model for the study and understanding of conserved polymorphic sequences (CPSs) and structural diversity of ancestral haplotypes (AHs)/conserved extended haplotypes (CEHs). The aim of this study was to use a set of 95 MHC genomic sequences downloaded from a publicly available BioProject database at NCBI to identify and characterise polymorphic human leukocyte antigen (HLA) class I genes and pseudogenes, MICA and MICB, and retroelement indels as haplotypic lineage markers, and single-nucleotide polymorphism (SNP) crossover loci in DNA sequence alignments of different haplotypes across the Olfactory Receptor (OR) gene region (~1.2 Mb) and the MHC class I region (~1.8 Mb) from the GPX5 to the MICB gene. Our comparative sequence analyses confirmed the identity of 12 haplotypic retroelement markers and revealed that they partitioned the HLA-A/B/C haplotypes into distinct evolutionary lineages. Crossovers between SNP-poor and SNP-rich regions defined the sequence range of haplotype blocks, and many of these crossover junctions occurred within particular transposable elements, lncRNA, OR12D2, MUC21, MUC22, PSORS1A3, HLA-C, HLA-B, and MICA. In a comparison of more than 250 paired sequence alignments, at least 38 SNP-density crossover sites were mapped across various regions from GPX5 to MICB. In a homology comparison of 16 different haplotypes, seven CEH/AH (7.1, 8.1, 18.2, 51.x, 57.1, 62.x, and 62.1) had no detectable SNP-density crossover junctions and were SNP poor across the entire ~2.8 Mb of sequence alignments. Of the analyses between different recombinant haplotypes, more than half of them had SNP crossovers within 10 kb of LTR16B/ERV3-16A3_I, MLT1, Charlie, and/or THE1 sequences and were in close vicinity to structurally polymorphic Alu and SVA insertion sites. These studies demonstrate that (1) SNP-density crossovers are associated with putative ancestral recombination sites that are widely spread across the MHC class I genomic region from at least the telomeric OR12D2 gene to the centromeric MICB gene and (2) the genomic sequences of MHC homozygous cell lines are useful for analysing haplotype blocks, ancestral haplotypic landscapes and markers, CPSs, and SNP-density crossover junctions.

Mendelian randomization integrating GWAS and eQTL data revealed genes pleiotropically associated with major depressive disorder

ObjectivesTo prioritize genes that are pleiotropically or potentially causally associated with the risk of MDD.MethodsWe applied the summary data-based Mendelian randomization (SMR) method integrating GWAS and expression quantitative trait loci (eQTL) data in 13 brain regions to identify genes that were pleiotropically associated with the risk of MDD. In addition, we repeated the analysis by using the meta-analyzed version of the eQTL summary data in the brain (brain-eMeta).ResultsWe identified multiple significant genes across different brain regions that may be involved in the pathogenesis of MDD. The prime-specific gene BTN3A2 (corresponding probe: ENSG00000186470.9) was the top hit showing pleotropic association with MDD in 9 of the 13 brain regions and in brain-eMeta, after correction for multiple testing. Many of the identified genes are located in the human major histocompatibility complex (MHC) region on chromosome 6 and are mainly involved in immune response.ConclusionsOur SMR analysis revealed that multiple genes showed pleiotropic association with MDD across the brain regions. These findings provide important leads to a better understanding of the mechanism of MDD, and reveals potential therapeutic targets for the prevention and effective treatment of MDD.

Soluble human leukocyte antigen-G evaluation in pregnant women with gestational diabetes mellitus

Background Gestational diabetes mellitus is any degree of glucose intolerance with onset or first recognition occurring late in second trimester and third trimester of pregnancy. It constitutes a greater impact on diabetes epidemic as it carries a major risk for developing type 2 diabetes mellitus to the mother and her fetus later in life. human leukocyte antigen (HLA)-G is a class Ib gene presents in the human major histocompatibility complex (MHC). HLA-G has an important role for mother and fetus tolerance during pregnancy, also in the pancreatic islet cells protection. This is a case-control study, measuring serum HLA-G levels by ELISA in 60 pregnant women with gestational diabetes compared with 36 normal pregnant women. Results HLA-G levels were significantly high in pregnant women with gestational diabetes mellitus (GDM) in contrast to women with normal pregnancy (P = 0.001). Conclusion Women with GDM had significantly higher levels of soluble HLA-G than women without GDM, suggesting that HLA-G molecule is among the factors for regulation and control of the immune response and the induction of tolerance. Soluble HLA-G could be considered an important follow-up investigation for all pregnant primary health care for early detection of gestational diabetes.

Inhibition of Mitochondrial Fission Reverses the Immunoescape of Solid Tumors via IRE1α-XBP-1s-TPP2 axis

Hypoexpression of human major histocompatibility complex (MHC) class I is widely known to be an important strategy of immune evasion in most cases of malignancies that lead to poor prognosis. We demonstrated that mitochondrial dynamics can be exploited as an efficient target in regulating MHC-I expression and cancer immunogenicity. Clinically, MHC-I expression and fragmentation of mitochondria are both closely associated to patient survival but are negatively correlated to one another. Mechanistically, it was observed that endoplasmic reticulum (ER) stress, an integrated signal transduction pathway activated in most rapidly proliferating tumor cells, played a crucial role in connecting mitochondrial fragmentation and cancer cell immunogenicity particularly via the IRE1α-XBP-1 s axis. XBP-1 s, which is activated by imbalanced mitochondrial fission and prolonged oxidative stress, served as a potent transcription factor, promoted the expression of aminopeptidase TPP2 and destructed the applicable antigenic peptide to impede MHC-I complex maturation and the activation of adaptive immune system upon cancer antigen. Our findings highlight the importance of mitochondrial dynamics in determining solid tumor immunogenicity and suggest that mediating mitochondrial fragmentation might provide a novel approach in anti-tumor immunotherapy.

Immunogenic SARS-CoV-2 Epitopes: In Silico Study Towards Better Understanding of COVID-19 Disease—Paving the Way for Vaccine Development

The emergence of the COVID-19 outbreak at the end of 2019, caused by the novel coronavirus SARS-CoV-2, has, to date, led to over 13.6 million infections and nearly 600,000 deaths. Consequently, there is an urgent need to better understand the molecular factors triggering immune defense against the virus and to develop countermeasures to hinder its spread. Using in silico analyses, we showed that human major histocompatibility complex (MHC) class I cell-surface molecules vary in their capacity for binding different SARS-CoV-2-derived epitopes, i.e., short sequences of 8-11 amino acids, and pinpointed five specific SARS-CoV-2 epitopes that are likely to be presented to cytotoxic T-cells and hence activate immune responses. The identified epitopes, each one of nine amino acids, have high sequence similarity to the equivalent epitopes of SARS-CoV virus, which are known to elicit an effective T cell response in vitro. Moreover, we give a structural explanation for the binding of SARS-CoV-2-epitopes to MHC molecules. Our data can help us to better understand the differences in outcomes of COVID-19 patients and may aid the development of vaccines against SARS-CoV-2 and possible future outbreaks of novel coronaviruses.

Investigations of sequencing data and sample type on HLA class Ia typing with different computational tools

Human leukocyte antigen (HLA) can encode the human major histocompatibility complex (MHC) proteins and play a key role in adaptive and innate immunity. Emerging clinical evidences suggest that the presentation of tumor neoantigens and neoantigen-specific T cell response associated with MHC class I molecules are of key importance to activate the adaptive immune systemin cancer immunotherapy. Therefore, accurate HLA typing is very essential for the clinical application of immunotherapy. In this study, we conducted performance evaluations of 4 widely used HLA typing tools (OptiType, Phlat, Polysolver and seq2hla) for predicting HLA class Ia genes from WES and RNA-seq data of 28 cancer patients. HLA genotyping data using PCR-SBT method was firstly obtained as the golden standard and was subsequently compared with HLA typing data by using NGS techniques. For both WES data and RNA-seq data, OptiType showed the highest accuracy for HLA-Ia typing than the other 3 programs at 2-digit and 4-digit resolution. Additionally, HLA typing accuracy from WES data was higher than from RNA-seq data (99.11% for WES data versus 96.42% for RNA-seq data). The accuracy of HLA-Ia typing by OptiType can reach 100% with the average depth of HLA gene regions >20x. Besides, the accuracy of 2-digit and 4-digit HLA-Ia typing based on control samples was higher than tumor tissues. In conclusion, OptiType by using WES data from control samples with the high average depth (>20x) of HLA gene regions can present a probably superior performance for HLA-Ia typing, enabling its application in cancer immunotherapy.

Regulation of Interferon Induction by the Ubiquitin-Like Modifier FAT10

The revelation that the human major histocompatibility complex (MHC) class I locus encodes a ubiquitin-like protein designated HLA-F adjacent transcript 10 (FAT10) or ubiquitin D (UBD) has attracted increasing attention to the function of this protein. Interestingly, the pro-inflammatory cytokines interferon (IFN)-γ and tumor necrosis factor (TNF) α synergize to strongly induce FAT10 expression, thereby suggesting a role of FAT10 in the immune response. Recent reports that FAT10 downregulates type I interferon production while it upregulates IFN-γ pose mechanistic questions on how FAT10 differentially regulates interferon induction. Several covalent and non-covalent binding partners of FAT10 involved in signal transduction pathways leading to IFN synthesis have been identified. After introducing FAT10, we review here recent insights into how FAT10 affects proteins in the interferon pathways, like the virus-responsive pattern recognition receptor RIG-I, the ubiquitin ligase ZNF598, and the deubiquitylating enzyme OTUB1. Moreover, we outline the consequences of FAT10 deficiency on interferon synthesis and viral expansion in mice and human cells. We discuss the need for covalent isopeptide linkage of FAT10 to the involved target proteins and the concomitant targeting for proteasomal degradation. After years of investigating the elusive biological functions of this fascinating ubiquitin-like modifier, we review the emerging evidence for a novel role of FAT10 in interferon regulation.

MHC*IMP – Imputation of Alleles for Genes in the Major Histocompatibility Complex

We report the development of MHC*IMP, a method for imputing non-classical HLA and other genes in the human Major Histocompatibility Complex (MHC). We created a reference panel for 25 genes in the MHC using allele calls from Whole Genome Sequencing data, combined with SNP data for the same individuals. We used this to construct an allele imputation model, MHC*IMP, for each gene. Cross-validation showed that MHC*IMP performs very well, with allele prediction accuracy 93% or greater for all but two of the genes, and greater than 95% for all but four.

Analysis of transporter associated with antigen presentation (TAP) genes polymorphisms with HIV-1 infection

Human leukocyte antigen (HLA) class I molecules of the human major histocompatibility complex (MHC) play an important role in modulating immune response. HLA class I molecules present antigenic peptides to CD8+ T cells and thereby play a role in the immune surveillance of cells infected with viruses. TAP1 and TAP2 are MHC-II-encoded genes necessary for the generation of a cellular immune response and polymorphism of these genes can influence the specificity of peptides preferentially presented by the MHC class I molecules and the outcome of the immune response. Several studies implicated genetic variation in TAP genes to various immune-mediated and infectious diseases. To determine the correlation between HIV-1 infection and the TAP1 and TAP2 genes polymorphisms, we performed PCR–RFLP assay of these genes in 500 HIV-1 seropositives and the matched seronegative individuals. Statistical analysis of the data disclosed no correlation between TAP1 (C/T intron 7) gene polymorphism and HIV-1/AIDS disease. However, the current results demonstrated that the heterozygous A/G [OR (95% CI) 1.39 (1.06–1.83), P = 0.0171] and homozygous G/G [OR (95% CI) 3.38(1.56–7.46), P = 0.0010] variants of TAP2 (A/G exon 11) (T665A) gene are positively associated with an increased risk of HIV-1/AIDS infection. This case–control analysis might suggest a possible role of TAP2 (A/G exon 11) (T665A) gene in the susceptibility to HIV-1 infection and disease outcome among North Indian patients.