Epirus Institute of Technology

Árta, Greece

Epirus Institute of Technology

Árta, Greece
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Chow I.-T.,Benaroya Research Institute | James E.A.,Benaroya Research Institute | Gates T.J.,Benaroya Research Institute | Tan V.,Benaroya Research Institute | And 4 more authors.
Journal of Immunology | Year: 2013

DRB1*08:01 (DR0801) and DRB1*11:01 (DR1101) are highly homologous alleles that have opposing effects on susceptibility to primary biliary cirrhosis (PBC). DR0801 confers risk and shares a key feature with other HLA class II alleles that predispose to autoimmunity: a nonaspartic acid at beta57. DR1101 is associated with protection from PBC, and its sequence includes an aspartic acid at beta57. To elucidate a mechanism for the opposing effects of these HLA alleles on PBC susceptibility, we compared the features of epitopes presented by DR0801 and DR1101. First, we identified DR0801- and DR1101-restricted epitopes within multiple viral Ags, observing both shared and distinct epitopes. Because DR0801 is not well characterized, we deduced its motif by measuring binding affinities for a library of peptides, confirming its key features through structural modeling. DR0801 was distinct from DR1101 in its ability to accommodate charged residues within all but one of its binding pockets. In particular, DR0801 strongly preferred acidic residues in pocket 9. These findings were used to identify potentially antigenic sequences within PDC-E2 (an important hepatic autoantigen) that contain a DR0801 motif. Four peptides bound to DR0801 with reasonable affinity, but only one of these bound to DR1101. Three peptides, PDC-E2145-159, PDC-E2249-263, and PDC-E2629-643, elicited high-affinity T cell responses in DR0801 subjects, implicating these as likely autoreactive specificities. Therefore, the unique molecular features of DR0801 may lead to the selection of a distinct T cell repertoire that contributes to breakdown of self-tolerance in primary biliary cirrhosis, whereas those of DR1101 promote tolerance. Copyright © 2013 by The American Association of Immunologists, Inc.

Van Heemst J.,Leiden University | Jansen D.T.S.L.,Leiden University | Polydorides S.,University of Cyprus | Moustakas A.K.,Alexander Technological Educational Institute of Thessaloniki | And 13 more authors.
Nature Communications | Year: 2015

The HLA locus is the strongest risk factor for anti-citrullinated protein antibody (ACPA) + rheumatoid arthritis (RA). Despite considerable efforts in the last 35 years, this association is poorly understood. Here we identify (citrullinated) vinculin, present in the joints of ACPA + RA patients, as an autoantigen targeted by ACPA and CD4 + T cells. These T cells recognize an epitope with the core sequence DERAA, which is also found in many microbes and in protective HLA-DRB1∗13 molecules, presented by predisposing HLA-DQ molecules. Moreover, these T cells crossreact with vinculin-derived and microbial-derived DERAA epitopes. Intriguingly, DERAA-directed T cells are not detected in HLA-DRB1∗13 + donors, indicating that the DERAA epitope from HLA-DRB1∗13 mediates (thymic) tolerance in these donors and explaining the protective effects associated with HLA-DRB1∗13. Together our data indicate the involvement of pathogen-induced DERAA-directed T cells in the HLA-RA association and provide a molecular basis for the contribution of protective/predisposing HLA alleles.

Delli A.J.,Lund University | Vaziri-Sani F.,Lund University | Lindblad B.,Gothenburg University | Elding-Larsson H.,Lund University | And 12 more authors.
Diabetes | Year: 2012

We examined whether zinc transporter 8 autoantibodies (ZnT8A; arginine ZnT8-RA, tryptophan ZnT8-WA, and glutamine ZnT8-QA variants) differed between immigrant and Swedish patients due to different polymorphisms of SLC30A8, HLA-DQ, or both. Newly diagnosed autoimmune (≥1 islet autoantibody) type 1 diabetic patients (n = 2,964, <18 years, 55% male) were ascertained in the Better Diabetes Diagnosis study. Two subgroups were identified: Swedes (n = 2,160, 73%) and immigrants (non-Swedes; n = 212, 7%). Non-Swedes had less frequent ZnT8-WA (38%) than Swedes (50%), consistent with a lower frequency in the non-Swedes (37%) of SLC30A8 CT+TT (RW+WW) genotypes than in the Swedes (54%). ZnT8-RA (57 and 58%, respectively) did not differ despite a higher frequency of CC (RR) genotypes in non-Swedes (63%) than Swedes (46%). We tested whether this inconsistency was due to HLA-DQ as 2/X (2/2; 2/y; y is anything but 2 or 8), which was a major genotype in non-Swedes (40%) compared with Swedes (14%). In the non-Swedes only, 2/X (2/2; 2/y) was negatively associated with ZnT8-WA and ZnT8-QA but not ZnT8-RA. Molecular simulation showed nonbinding of the relevant ZnT8-R peptide to DQ2, explaining in part a possible lack of tolerance to ZnT8-R. At diagnosis in non-Swedes, the presence of ZnT8-RA rather than ZnT8-WA was likely due to effects of HLA-DQ2 and the SLC30A8 CC (RR) genotypes. © 2012 by the American Diabetes Association.

Van Lummel M.,Leiden University | Van Veelen P.A.,Leiden University | Zaldumbide A.,Leiden University | De Ru A.,Leiden University | And 6 more authors.
Journal of Biological Chemistry | Year: 2012

HLA-DQ2 and HLA-DQ8 are strongly predisposing haplotypes for type 1 diabetes (T1D). Yet HLA-DQ2/8 heterozygous individuals have a synergistically increased risk compared with HLA-DQ2 or HLA-DQ8 homozygote subjects that may result from the presence of a transdimer formed between the α-chain of HLA-DQ2 (DQA1*05:01) and the β-chain of HLA-DQ8 (DQB1*03:02). We generated cells exclusively expressing this transdimer (HLA-DQ8trans), characterized its peptide binding repertoire, and defined a unique transdimer-specific peptide binding motif that was found to be distinct from those of HLA-DQ2 and HLA-DQ8. This motif predicts an array of peptides of islet autoantigens as candidate T cell epitopes, many of which selectively bind to the HLA transdimer, whereas others bind to both HLA-DQ8 and transdimer with similar affinity. Our findings provide a molecular basis for the association between HLA-DQ transdimers and T1D and set the stage for rational testing of potential diabetogenic peptide epitopes. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc.

James E.A.,Benaroya Research Institute | Moustakas A.K.,Technological Educational Institute of the Ionian Islands | Bui J.,Benaroya Research Institute | Papadopoulos G.K.,Epirus Institute of Technology | And 3 more authors.
Arthritis and Rheumatism | Year: 2010

Objective. HLA-DRB1*1001 (DR1001) is a shared epitope allele associated with rheumatoid arthritis (RA). The present study was undertaken to assess the capacity of DR1001 to accommodate citrulline in its binding pockets and to identify citrullinated T cell epitopes derived from joint-associated proteins. Methods. The binding of peptide derivatives containing citrulline, arginine, and other amino acid substitutions was measured. A prediction algorithm was developed to identify arginine-containing sequences from joint-associated proteins that preferentially bind to DR1001 upon citrullination. Unmodified and citrullinated versions of these sequences were synthesized and were utilized to stimulate CD4+ T cells from healthy subjects and RA patients. Responses were measured by class II major histocompatibility complex tetramer staining and confirmed by isolating CD4+ T cell clones. Results. DR1001 accepted citrulline, but not arginine, in 3 of its anchoring pockets. The prediction algorithm identified sequences that preferentially bound to DR1001 with arginine replaced by citrulline. Three of these sequences elicited CD4+ T cell responses. T cell clones specific for these sequences proliferated only in response to citrullinated peptides. Conclusion. Conversion of arginine to citrulline generates "altered-self" peptides that can be bound and presented by DR1001. Responses to these peptides implicate the corresponding proteins (fibrinogen α, fibrinogen β, and cartilage intermediate-layer protein) as relevant antigens. The finding of preferential responses to citrullinated sequences suggests that altered peptide binding affinity due to this posttranslational modification may be an important factor in the initiation or progression of RA. As such, measuring responsiveness to these peptides may be useful for immunologic monitoring. © 2010, American College of Rheumatology.

Behrens M.,Mayo Medical School | Papadopoulos G.K.,Epirus Institute of Technology | Moustakas A.,Technological Educational Institute of the Ionian Islands | Smart M.,Mayo Medical School | And 3 more authors.
Arthritis and Rheumatism | Year: 2011

Objective Certain HLA class II alleles are associated with susceptibility to the development of arthritis. However, the development of arthritis in some persons carrying non-rheumatoid arthritis (RA)-associated alleles remains unexplained. An individual who is heterozygous for the DQA1 and DQB1 genes can express the DQ molecule in cis or trans heterodimers. In a cis heterodimer, the α-chain interacts with the β-chain coded by the same chromosome, while in a trans heterodimer it interacts with the β-chain on the other chromosome. In this study, we used a humanized mouse model of arthritis in an attempt to determine whether a trans heterodimer of 2 nonassociated alleles, DQB1*0601 and DQB1*0604, can predispose to arthritis. Methods DQB1*0601 and*0604 occur in linkage with DQA1*0103 and*0102, respectively. To understand the role of trans heterodimers, we generated DQB1*0604/DQA1*0103-transgenic mice lacking endogenous HLA class II molecules. Results Severe arthritis developed in the DQB1*0604/A1*0103-trangenic mice, and an antigen-specific response was generated in vitro. DQB1*0604/DQA1*0103 presented type II collagen-derived peptides that were not presented by the arthritis-resistant DQB1*0601 allele, suggesting that trans heterodimer molecules between 2 DQB1 and DQA1 molecules may result in the presentation of unique antigens and susceptibility to the development of arthritis. Molecular modeling of type II collagen peptides showed that DQB1*0604/DQA1*0103 shares a p4 pocket with the arthritis-susceptible DQB1*0302 allele, suggesting a critical role of the p4 and p9 pockets in susceptibility to arthritis. Conclusion These results provide a possible explanation for the parental inheritance of nonsusceptibility alleles in some patients with RA and a mechanism by which they can predispose to the development of arthritis. Copyright © 2011 by the American College of Rheumatology.

Eerligh P.,Leiden University | Van Lummel M.,Leiden University | Zaldumbide A.,Leiden University | Moustakas A.K.,Technological Education Institute of Ionian Islands | And 6 more authors.
Genes and Immunity | Year: 2011

Human leukocyte antigen (HLA) class II haplotypes are established risk factors in type 1 diabetes (T1D). The heterozygous DQ2/8 genotype confers the highest risk, whereas the DQ6/8 genotype is protective. We hypothesized that DQ2/8 trans-molecules composed of α and Β chains from DQ2 and DQ8 express unique Β-cell epitopes, whereas DQ6 may interfere with peptide binding to DQ8. Here we show that a single insulin epitope (InsB13-21) within the T1D prototype antigenic InsB6-22 peptide can bind to both cis-and trans-dimers, although these molecules display different peptide binding patterns. DQ6 binds a distinct insulin epitope (InsB6-14). The phenotype of DQ8-restricted T cells from a T1D patient changed from proinflammatory to anti-inflammatory in the presence of DQ6. Our data provide new insights into both susceptible and protective mechanism of DQ, where protecting HLA molecules bind autoantigens in a different (competing) binding register leading to epitope stealing, thereby inducing a regulatory, rather than a pathogenic immune response. © 2011 Macmillan Publishers Limited All rights reserved.

Chow I.-T.,Benaroya Research Institute | James E.A.,Benaroya Research Institute | Tan V.,Benaroya Research Institute | Moustakas A.K.,Technological Education Institute of Ionian Islands | And 3 more authors.
Molecular Immunology | Year: 2012

This study characterized the unique peptide-binding characteristics of HLA-DRB1*12:01 (DR1201), an allele studied in the context of various autoimmune diseases, using a peptide competition assay and structural modeling. After defining Influenza A/Puerto Rico/8/34 Matrix Protein M1 (H1MP) 40-54 as a DR1201 restricted epitope, the critical anchor residues within this sequence were confirmed by measuring the relative binding of peptides with non-conservative substitutions in competition with biotin labeled H1MP 40-54 peptide. Based on this information, a set of peptides was designed with single amino acid substitutions at these anchor positions. The overall peptide binding preferences for the DR1201 allele were deduced by incubating these peptides in competition with the reference H1MP 40-54 to determine the relative binding affinities of each to recombinant DR1201 protein. As expected, pocket 1 preferred methionine and aliphatic residues, and tolerated phenylalanine. Pocket 4 was mostly composed of hydrophobic residues, thereby preferentially accommodating aliphatic residues, but could also weakly accommodate lysine due to its slightly acidic environment. Pocket 6 accepted a wide range of amino acids because of the diverse residues that comprise this pocket. Pocket 9 accepted aliphatic and negatively charged amino acids, but showed a remarkable preference for aromatic residues due to the conformation of the pocket, which lacks the typical salt bridge between β57Asp and α76Arg. These binding characteristics contrast with the closely related DR1104 allele, distinguishing DR1201 among the alleles of the HLA-DR5 group. These empirical results were used to develop an algorithm to predict peptide binding to DR1201. This algorithm was used to verify T cell epitopes within novel antigenic peptides identified by tetramer staining and within peptides from published reports that contain putative DR1201 epitopes. © 2011 Elsevier Ltd.

Pavlidis I.V.,University of Ioannina | Vorhaben T.,University of Greifswald | Gournis D.,University of Ioannina | Papadopoulos G.K.,Epirus Institute of Technology | And 2 more authors.
Journal of Nanoparticle Research | Year: 2012

The interaction of enzymes with carbonbased nanomaterials (CBN s) is crucial for the functionof biomolecules and therefore for the design and development of effective nanobiocatalytic systems. In this study, the effect of functionalized CBN s, such as graphene oxide (GO) and multi-wall carbon nanotubes (CNT s), on the catalytic behaviour of various hydrolases of biotechnological interest was monitored and the interactions between CBN s and proteins were investigated. The enzyme-nanomaterial interactionssignificantly affect the catalytic behaviour of enzymes, resulting in an increase up to 60 % of the catalyticefficiency of lipases and a decrease up to 30 % of the esterase. Moreover, the use of CNT s and GO derivatives, especially those that are amine-functionalized, led to increased thermal stability of most the hydrolases tested. Fluorescence and circular dichroism studies indicated that the altered catalytic behaviour of enzymes in the presence of CBN s arises from specific enzyme-nanomaterial interactions, which can lead to significant conformational changes. In the case of lipases, the conformational changes led to a more active and rigid structure, while in the case of esterases this led to destabilization and unfolding. Kinetic and spectroscopic studies indicated that the extent of the interactions between CBN s and hydrolases can bemainly controlled by the functionalization of nanomaterials than by their geometry. © 2012 Springer Science+Business Media B.V.

PubMed | Leiden University, Epirus Institute of Technology and Technological Education Institute of Ionian Islands
Type: Journal Article | Journal: Arthritis research & therapy | Year: 2016

Presentation of citrullinated neo-epitopes by HLA-DRB1 molecules that carry the shared epitope (SE) sequence was proposed to explain the association between HLA and seropositive RA. Although it is shown that several HLA-DRB1-SE molecules display enhanced binding affinities for citrullinated ligands, the ability of other HLA molecules to present citrullinated epitopes has not been investigated in a systematic manner. To better understand the HLA-RA connection, we aimed to investigate if the enhanced capacity to present arginine-to-citrulline-converted peptides is unique for HLA-SE alleles.We selected four HLA molecules (one HLA-DR and three HLA-DQ molecules) that could potentially prefer citrulline over arginine residues in specific pockets and in addition two HLA-SE alleles as a method validation control. The affinity of peptides containing arginine/citrulline residues at positions interacting with the various peptide-binding pockets was compared by HLA class II peptide affinity assays.Pocket 4 of HLA-DRB1*04:04 and -DRB1*04:05 displayed a preference for citrulline over arginine, a property found in other pockets as well. HLA-DRB1*03:01 did not display an enhanced affinity for peptides containing a citrulline. In contrast, several peptide-binding pockets of the analyzed HLA-DQ molecules showed enhanced affinities for citrulline compared to arginine residues: i.e., pockets 4, 6, 7, and 9 of HLA-DQ2 and pockets 1, 6, and 9 of HLA-DQ7 and HLA-DQ8.Arginine-to-citrulline conversion of peptides can also enhance the binding affinity for non-HLA-SE molecules. Hence the capacity to present citrullinated neo-epitopes is not confined to HLA-SE molecules, opening the possibility that also other HLA molecules could potentiate a possible breach of T cell tolerance toward citrullinated antigens.

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