Dataset Information

The HLA-DRB1*03:01 ligandome is highly conserved on N- and C-terminal residues outside the peptide-binding cleft

ABSTRACT: Human CD4+ T lymphocytes play an important role in inducing potent immune responses. They are activated and stimulated by peptides presented in Major Histocompatibility Complex Class II molecules. These MHC class II molecules typically present peptides of between 12 and 20 amino acids in length. The region that interacts with the MHC molecule, designated as the binding core, is highly conserved in the residues which anchor the peptide to the molecule. In addition, as these peptides are the product of proteolytic cleavages, certain conserved residues may be expected at the N- and C-termini outside the binding core. To study whether similar conserved residues are present in different types of cells , the ligandomes of HLA-DRB1*03:01 derived from two different cell types (dendritic cells and EBV-transformed B-cells) were identified with mass spectrometry and the binding core and N- and C-terminal residues were analysed using the frequencies of the amino acids in the human proteome. Similar binding motifs were found as well as comparable conservations in the N- and C-terminal residues. Furthermore, these terminal conservations of the HLA-DRB1*03:01 ligandome were compared to the N- and C-terminal conservations of the HLA-DRB1*04:01 ligandome acquired from dendritic cells. Again, comparable conservations were evident with only minor differences. Taken all together, these analyses show that there are conservations in the terminal residues of peptides, presumably the result of the activity of proteases involved in antigen processing.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): B Cell, Dendritic Cell, Cell Culture

DISEASE(S): Disease Free

SUBMITTER: G Janssen

LAB HEAD: Peter A van Veelen

PROVIDER: PXD014253 | Pride | 2019-09-16

REPOSITORIES: Pride

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Ligandomes obtained from different HLA-class II-molecules are homologous for N- and C-terminal residues outside the peptide-binding cleft.

Kampstra Arieke S B ASB van Heemst Jurgen J Janssen George M GM de Ru Arnoud H AH van Lummel Menno M van Veelen Peter A PA Toes René E M REM

Immunogenetics 20190913 8-9

Human CD4+ T lymphocytes play an important role in inducing potent immune responses. T cells are activated and stimulated by peptides presented in human leucocyte antigen (HLA)-class II molecules. These HLA-class II molecules typically present peptides of between 12 and 20 amino acids in length. The region that interacts with the HLA molecule, designated as the peptide-binding core, is highly conserved in the residues which anchor the peptide to the molecule. In addition, as these peptides are t ...[more]

PMID: 31520135

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Project description:Infection or reactivation with human cytomegalovirus (HCMV) is still a major cause of morbidity and mortality in patients undergoing solid organ transplantation or allogeneic stem cell transplantation (alloSCT). Recent studies have shown that protection against latent HCMV infection relies on a much broader antigen spectrum than previously expected. The identification of novel immunogenic HCMV-derived peptides that facilitate HCMV control is therefore essential to improve immune monitoring of HCMV-specific T cells and HCMV vaccine development. In particular, only a few HCMV-derived peptides have been described for less common HLA alleles, such as HLA-A*03:01 and HLA-B*15:01, limiting the implementation of these techniques for a substantial number of patients. Here, we identified novel HCMV-derived HLA-A*03:01- and HLA-B*15:01-restricted immunogenic peptides by an innovative combined in vitro and in silico approach. We utilized the computational tools Peptide-PRISM (1) and PRICE (2) to analyze mass spectrometric (MS) and ribosome sequencing (ribo-seq) datasets, respectively. To refine our in silico approach, we utilized machine learning to rate the identified peptide candidates based on their translational activity, binding affinity and positioning within the small open reading frames (sORFs), with the goal of assessing their likelihood to be presented on HLA-A*03:01 and HLA-B*15:01 molecules. After identifying the highest-scoring 49 canonical and 49 cryptic potentially immunogenic peptides for each HLA allele, we assessed their immunogenicity by screening HCMV-seropositive and -seronegative healthy donors, as well as alloSCT patients for their peptide-specific T-cell responses. We used a stimulation procedure in two consecutive steps: peripheral blood cells (PBMCs) were stimulated starting with peptide pools and subsequently with potentially reactive single peptides. In vitro T-cell stimulation resulted in the direct identification of three canonical and one cryptic HLA-A*03-restricted immunogenic peptides as well as five canonical and one cryptic HLA-B*15-restricted immunogenic peptide, with a specific IFNγ+/CD8+ T cell response of ≥ 0.02%. Highest T-cell responses were identified against two HLA-A*03-restricted and three HLA-B*15-restricted canonical peptides with up to 3.42% of IFNγ+/CD8+ T cells in patients 180 days post alloSCT. In conclusion, we identified specific T-cell responses against eight canonical and two cryptic HLA-A*03:01- and HLA-B*15:01-restricted peptides in healthy individuals and post-transplanted patients and which were classified as immunogenic. Of these, six peptides are novel HCMV-derived, immunogenic peptides according to the UniProt database, broadening the spectrum of immunogenic HCMV-derived peptides for personalized immune monitoring and vaccine development.

Project description:Human leukocyte antigen (HLA) - B*51:01 and endoplasmic reticulum aminopeptidase 1 (ERAP1) are two strong predisposing genetic factors to Behçet's disease (BD). Previous studies have focused on two subgroups of HLA-B*51 peptidome containing Proline (Pro) or Alanine (Ala) at position 2 (P2). Little is known about the unconventional non-Pro/Ala2 HLA-B*51-bound peptides. We aimed to study the features of this novel sub-peptidome, and investigate its regulation by ERAP1. CRISPR-Cas9 was used to generate an HLA-ABC-knockout HeLa cell line (HeLa.ABC-KO), which was subsequently transduced to express HLA-B*51:01 (HeLa.ABC-KO.B51). ERAP1 was silenced using lentiviral shRNA. Peptides bound to HLA-B*51:01 were eluted and analyzed by Mass Spectrometry. The characteristics of non-Pro/Ala2, Pro2 and Ala2 peptides, and their alteration by ERAP1 silencing were investigated. Effects of ERAP1 silencing on cell surface expression of HLA-B*51:01 were studied using flow cytometry. More than 20% of peptides eluted from HLA-B*51:01 lacked Proline or Alanine at P2. This unconventional group of HLA-B*51:01-bound peptides was enriched for 8-mers (with fewer 9-mers) compared to Pro2 and Ala2 sub-peptidomes, and had similar N-terminal and C-terminal residue usages to Ala2 peptides with the exception of the less abundant Leucine at position Ω. Knockdown of ERAP1 increased the percentage of non-Pro/Ala2 to approximately 40%, increased the percentage of longer (10-mer and 11-mer) peptides eluted from HLA-B*51:01 complexes, and abrogated the predominance of Leucine at P1. Interestingly knockdown of ERAP1 altered the length and N-terminal residue usage of non-Ala2&Pro2 and Ala2 but not the Pro2 peptides. Finally, ERAP1 silencing regulated the expression levels of cell surface HLA-B*51 in a cell type - dependent manner. The HLA-B*51:01 peptidome includes a surprisingly high proportion of unconventional non-Pro/Ala2 peptides which are increased by ERAP1 silencing, mimicking the loss-of-function BD risk variant.

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	DR3homo.msf	Msf
	DR4homo.msf	Msf
	DUCAF.msf	Msf
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	Q2133252b.raw	Raw