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F Vartdal

Publications and source records attributed to F Vartdal.

At least 37 records · Page 2Linked to original sources
PubMed1996

The peptide binding motif of the disease associated HLA-DQ (alpha 1* 0501, beta 1* 0201) molecule.

To identify the binding motifs of peptides which bind to the celiac disease and insulin-dependent-diabetes-mellitus (IDDM)-associated DQ2 molecule, peptides were eluted from affinity-purified DQ2 molecules. The eluted peptides were separated by reverse-phase HPLC. Prominent peptide peaks and the remaining pool of peptides were sequenced by Edman degradation. Truncated variants of eight different peptides with a length of 9-19 amino acids were identified; among them class II-associated invariant chain peptides (CLIP) and peptides that stem from HLA class I alpha, HLA-DQ alpha 1*0501, Ig and CD20 molecules. Data from the pool sequencing and the biochemical binding analyses of synthetic variants of an eluted high-affinity ligand (HLA class I alpha 46-60), indicate that the side chains of amino acid residues at relative position P1 (bulky hydrophobic), P4 (negatively charged or aliphatic), P6 (Pro or negatively charged), P7 (negatively charged) and P9 (bulky hydrophobic) are important for binding of peptides to DQ2. Computer modeling of the DQ2 with variants of the high-affinity ligand in the groove suggests that peptides bind to DQ2 through the primary anchors P1, P7 and P9 and making additional advantageous interactions using the P4 and P6 positions.

Alleles↗
PubMed1996

Binding of peptides from the N-terminal region of alpha-gliadin to the celiac disease-associated HLA-DQ2 molecule assessed in biochemical and T cell assays.

Celiac disease (CD) is most probably an immunological disease, precipitated in susceptible individuals by ingestion of wheat gliadin and related proteins from other cereals. The disease shows a strong HLA association predominantly to the cis- or trans-encoded HLA-DQ(alpha1*0501, beta1*02) (i.e., DQ2) heterodimer. T cell recognition of gliadin peptides presented by DQ2 in the intestinal mucosa is central in the immunopathogenesis of CD. Here we describe a study where overlapping peptides from the N-terminal region of alpha-gliadin have been tested in biochemical assays for binding to affinity-purified DQ2 and DR3 (i.e., DR(alpha, beta1*0301)) molecules. The peptides were also tested for binding to DQ2 in a functional binding assay, where binding was measured as the capacity to inhibit the stimulation of a gliadin-specific, DQ2-restricted T lymphocyte clone RNnTalpha33. In both assay systems the overlapping gliadin peptides were found to bind with weak or intermediate affinity to DQ2. No or only very weak binding was found to DR3 in the biochemical binding assay. Overall, the results question the role of these peptides in the T-cell-mediated immunopathogenesis of CD. The in vitro assays described here provide new methods for the screening of potentially toxic peptides.

Amino Acid Sequence↗
PubMed1996

Both alpha and beta chain polymorphisms determine the specificity of the disease-associated HLA-DQ2 molecules, with beta chain residues being most influential.

We compared the peptide binding specificity of three HLA-DQ molecules; HLA-DQ(alpha1(*)0501, beta1(*)0201), HLA-DQ(alpha1(*)0201, beta1(*)0202), and HLA-DQ(alpha1(*)0501, beta1(*)0301). The first of these molecules confers susceptibility to celiac disease and insulin-dependent diabetes mellitus, while the two latter molecules, which share either the alpha chain or the nearly identical beta chain with HLA-DQ(alpha1(*)0501, beta1(*)0201), do not predispose to these disorders. The binding of peptides was detected in biochemical binding assays as inhibition of binding of radiolabeled indicator peptides to affinity-purified HLA-DQ molecules. Binding experiments with several peptides demonstrated a clear difference in peptide binding specificity between the three HLA-DQ molecules. Further, single amino acid substitution analyses indicated that the HLA-DQ molecules have different peptide binding motifs. The experimental data were corroborated by computer modelling analysis. Our data suggest that the three HLA-DQ molecules prefer large hydrophobic residues in P1 of peptides with subtle differences in side-chain preferences. HLA-DQ(alpha1(*)0501, beta1(*)0201) and HLA-DQ(alpha1(*)0201, beta1(*)0202) both prefer large hydrophobic residues in P9, whereas HLA-DQ(alpha1(*)0501, beta1(*)0301) prefers much smaller residues in this position. HLA-DQ(alpha1(*)0501, beta1(*)0201) and HLA-DQ(alpha1(*)0201, beta1(*)0202), in contrast to HLA-DQ(alpha1(*)0501, beta1(*)0301), prefer negatively charged residues in P4 and P7. A less prominent P6 pocket also appears to differ between the three HLA-DQ molecules. Our results indicate that polymorphic residues of both the alpha and the beta chain determine the peptide binding specificity of HLA-DQ(alpha1(*)0501, beta1(*)0201), but that the beta chain polymorphisms appears to play the most important role. The information on peptide residues which are advantageous and deleterious for binding to these HLA-DQ molecules may make possible the prediction of characteristic features of peptide that bind to HLA-DQ(alpha1(*)0501, beta1(*)0201) and precipitate celiac disease.

Amino Acid Sequence↗
PubMed1996

Identification of a putative motif for binding of peptides to HLA-DQ2.

To understand the rules determining peptide binding to the celiac disease and type 1 diabetes mellitus associated HLA-DQ2 molecule, we have studies in detail the binding of a peptide OVA 258-276Y (IINFEKLTEWTSSNVMEERY) which exhibits strong binding to DQ2. First we tested a set of N- and C-terminal truncated variants, and found the core binding region to comprise residues 267-276Y. Single alanine substitution analysis of the OVA 267-276Y peptide revealed that replacements of V272, E275 and the C-terminal Y had negative effects whereas the substitution of N271 had a positive effect. A polyalanine analogue of the OVA 267-276Y peptide with V272, E275 and a C-terminal Y bound at least as well as the original peptide. A variant peptide with a deletion of R276 displayed decreased binding, suggesting that the anchor residues were out of frame in this analogue. To further characterize the residues playing a role in the binding of the OVA 267-276Y peptide to DQ2 we tested the binding of several analogues with substitutions for V272, E275 and the C-terminal Y residue. Our results indicate that peptides binding to DQ2 have anchor residues in relative positions 4, 7 and (P4, P7 and P9). Residues with negatively charged or hydrophobic aliphatic but not positively charged side chains are preferred in P4 and P7, whereas residues with bulky hydrophobic side chains are preferred in P9.

Amino Acids↗
PubMed1994

Heterogeneity of T cells specific for a particular peptide/HLA-DQ complex.

Whether T cells specific for a particular peptide/HLA-DQ complex are restricted with respect to TCR usage has not been fully established. TCR usage of T cells specific for a peptide presented by a given HLA-DQ molecule has not been studied before. We therefore sequenced the TCR genes of five different TCCs derived from the same donor, which were specific for a p21 ras-derived synthetic peptide presented by the HLA-DQ(alpha 1*0102,beta*0602) (DQ6) molecule. We found that these T cells which recognized the same peptide/HLA-DQ complex used highly diverse TCRs. However, dose-response experiments using various truncations of the p21 ras-derived peptide revealed that the peptide fine specificities of the five TCCs were not completely identical. This may explain the heterogeneity in TCR usage.

Amino Acid Sequence↗
PubMed1994

No association of multiple sclerosis to alleles at the TAP2 locus.

MS is associated with genes in the HLA complex. We have previously proposed that the primary HLA-associated susceptibility may be conferred by particular DQ alleles. Furthermore, we have previously found that there is no association of MS to DP alleles. This study shows that MS is not associated to alleles of the TAP2 locus, which is located close to DQ on its centromeric side. This observation provides further support to the notion that HLA-associated susceptibility to MS maps telomeric to the TAP2 locus.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Binding of peptides to HLA-DQ molecules: peptide binding properties of the disease-associated HLA-DQ(alpha 1*0501, beta 1*0201) molecule.

Peptide binding to DQ molecules has not previously been described. Here we report a biochemical peptide-binding assay specific for the DQ2 [i.e. DQ(alpha 1*0501, beta 1*0201)] molecule. This molecule was chosen since it shows a strong association to diseases such as celiac disease and insulin-dependent diabetes mellitus. Initially we radiolabelled some selected peptides and tested them for binding to affinity-purified DQ2 molecules. One of the peptides, a Mycobacterium bovis (MB) 65 kDa 243-255Y peptide, displayed a good signal-to-noise ratio and was thus chosen as an indicator peptide in the DQ2 binding assay. The MB 65 kDa 243-255Y peptide bound to DQ2 in a strictly pH-dependent fashion, with optimal binding around pH 5 and only weak binding at pH 7.4. The association of the MB 65 kDa 243-255Y peptide to DQ2 was slow, but once formed, the peptide-HLA complexes were very stable. The binding of peptides to DQ2 was specific, as shown in inhibition experiments with a panel of 47 peptides, differing in length, sequence, and origin. The binding of peptides to DR3 was tested in a similar assay with a Mycobacterium tuberculosis 65 kDa 3-13 peptide as the binding indicator. DQ2 and DR3 molecules bound to different sets of peptides. However, the peptide binding to DQ2 and DR3 showed, in general, similar characteristics with respect to pH dependence and kinetic parameters, indicating that the overall rules for peptide binding to DQ molecules are the same as those previously shown for human DR and murine I-A and I-E molecules.

Amino Acid Sequence↗
PubMed1994

Binding of ras oncogene peptides to purified HLA-DQ(alpha 1*0102,beta 1*0602) and -DR(alpha,beta 1*0101) molecules.

Mutated oncogene peptides may be presented to T cells by HLA molecules. To be able to design the optimal peptides for stimulation of T cells in individuals with different HLA molecules, it is important to analyse the binding characteristics of oncogene peptides to HLA. HLA-DQ6 (DQ(alpha 1*0102,beta 1*0602)) and HLA-DR1 (DR(alpha,beta 1*0101)) molecules were purified from lysates of homozygous EBV-transformed cell lines. Purified HLA molecules were then tested for their ability to bind synthetic peptides in gel filtration assays. A p21 ras oncogene peptide (previously found to stimulate DQ6-restricted T-cell clones) and an influenza matrix peptide were labelled with 125I and served as indicator peptides for binding to DQ6 and DR1 respectively. Binding of homologous truncated and mutated p21 ras peptides and unrelated peptides was then evaluated by their capacity to inhibit binding of the indicator peptides. p21 ras-derived peptides were found to bind to both DQ6 and DR1 molecules indicating the existence of a promiscuous binding motif in these peptides. The binding affinities seemed to vary between the different peptides, but the amino acid substitutions resulting from natural mutations were not critical for binding. Notably, the results obtained for DQ6 in the biochemical peptide binding assay correlated well with results obtained in a functional assay using T-cell clones as probes.

Amino Acid Sequence↗
PubMed1993

HLA class II alleles and heterogeneity of juvenile rheumatoid arthritis. DRB1*0101 may define a novel subset of the disease.

OBJECTIVE: To examine the distribution of HLA class II alleles in clinically distinct juvenile rheumatoid arthritis (JRA) subsets. METHODS: We typed 298 patients and 181 controls for HLA-DRB1, DQA1, DQB1, and DPB1 alleles using polymerase chain reaction and oligonucleotide probe techniques. RESULTS: Each JRA subset was characterized by a distinct distribution of HLA class II alleles. For the persistently pauciarticular and rheumatoid factor-negative polyarticular JRA subsets, certain combinations of DRB1 and DPB1 alleles were characteristic. In patients without antinuclear antibodies and chronic iridocyclitis, there was an increase of DRB1*0101/02 and DQA1*0101. CONCLUSION: Findings of HLA typing support clinical subdivisions of the disease and suggest the existence of a novel DRB1*0101/02 and DQA1*0101 associated disease subset.

Aging↗
PubMed1993

HLA matching of unrelated bone marrow transplant pairs: direct sequencing of in vitro amplified HLA-DRB1 and -DQB1 genes using magnetic beads as solid support.

Sequencing of HLA genes can offer complete information on the HLA class II genes relevant for the outcome of bone marrow transplantation (BMT). Genomic HLA matching of unrelated BMT patient/donor pairs is often based on PCR-SSO typing of HLA class II alleles. Typing a small number of samples by this approach is both expensive and time-consuming, due to the large number of SSO probes required to perform a complete class II typing. Moreover, only polymorphisms explicitly tested for will be found. We now provide the first report of the use of direct sequencing of HLA-DRB1 and -DQB1 genes, using PCR-amplified genomic DNA attached to magnetic beads, for clinical routine HLA matching. Sequencing ladders obtained by this procedure are easily readable, the patterns can be interpreted in HLA homozygous as well as heterozygous individuals, and sequence differences or similarities between the BMT donor and recipient can be directly identified. This genomic typing method is informative, relatively fast and therefore well-suited for the small number of samples usually analyzed in matching of BMT pairs. Furthermore, this technique has the potential for automation.

Base Sequence↗
PubMed1992

HLA-DR and -DQ genotypes of celiac disease patients serologically typed to be non-DR3 or non-DR5/7.

The susceptibility to develop celiac disease (CD) seems to be primarily associated to a particular HLA-DQ alpha/beta heterodimer encoded by the DQA1*0501 and DQB1*0201 alleles, in cis position on the DR3-DQ2 haplotype or in trans position by DR5-DQ7/DR7-DQ2 heterozygotes. However, exceptional patients exist who are neither DR3 nor DR5/DR7, particularly among Southern European populations. We therefore examined the DRB1, DQA1, and DQB1 alleles of 13 Spanish CD patients who were serologically typed to be neither DR3 nor DR5/DR7. Five patients were found to carry the DQA1*0501 and DQB1*0201 alleles either in cis or in trans position, three of them had previously been serologically mistyped. However, two of these patients carried DQA1*0501 and DQB1*0201 on haplotypes other than DR3 or DR5 in combination with DR7. One of the latter patients carried an unusual DR4-DQ2 haplotype, while another had an unusual DR8-DQ2 haplotype. Four of the remaining eight patients carried DR4-DQ8 haplotypes. Taken together, our findings provide further evidence that the DQ alpha/beta heterodimer encoded by the DQA1*0501 and the DQB1*0201 alleles confers the primary HLA-associated susceptibility to develop CD. However, our studies also corroborate that a second (and "weaker") HLA-associated CD susceptibility gene may be present on some DR4-carrying haplotypes.

Adolescent↗
PubMed1992

Linkage disequilibrium between DPA1 and DPB1 alleles among Norwegian Caucasoids and Japanese.

Associations between alleles at the DPA1 and DPB1 loci were analyzed in 181 Norwegian caucasoids. Associations were observed between the DPA1*0201 and the DPB1*0101, *0901, *1001 and *1101 alleles. An association between DPA1*0201 and the DPB1*0901 allele was also observed among 23 healthy Japanese and 24 Japanese MS patients. In addition, it appeared that among Japanese the DPA1*0201 allele may be associated to the DPB1*0501. In conclusion, alleles at the DPA1 and DPB1 loci display different associations among Norwegian caucasoids and Japanese.

Alleles↗
PubMed1992

Staphylococcal exotoxin superantigens induce human immunodeficiency virus type 1 expression in naturally infected CD4+ T cells.

A high proportion of Staphylococcus aureus strains of human origin produce one or more exotoxins. In vivo, these toxins may give rise to a variety of clinical syndromes. In vitro, staphylococcal exotoxins have been shown to bind both to human leukocyte antigen (HLA) class II molecules on antigen-presenting cells and to the T-cell receptors on large fractions of T cells. The result of this interaction may be proliferation of the T cells, T-cell anergy, or apoptosis, depending on several factors, including the state of the responding cells and the presence of accessory molecules. Using naturally infected peripheral blood mononuclear cells depleted of CD8+ T cells, we have shown that staphylococcal exotoxins are powerful inducers of human immunodeficiency virus type 1 expression and that they induce expression at low concentrations and with greater efficiency than other T-cell mitogens. Human immunodeficiency virus type 1 was produced entirely by CD4+ T cells in this model; monocytes were expendable both as a source of virus and as a source of HLA class II molecules as long as other cells expressing HLA class II molecules were present. The results suggest that infection by S. aureus may be a cofactor in the immunopathogenesis of AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1991

[Quantification of T-lymphocyte subpopulations. Immunological marker in human immunodeficiency virus infections].

The absolute number of CD4+ and CD8+ T cells was counted directly in the blood of 75 healthy controls and 223 individuals infected with human immunodeficiency virus (HIV). The HIV-seropositive individuals were also classified clinically according to the system recommended by the Centers for Disease Control. We observed a pattern of changes in the T cell subset counts of the patient group. This pattern could be defined by five T cell stages ranging from normal T cell subset values to values representing severe T cell immunodeficiency. A close correlation was observed between the immunological and clinical classification of the patients. Quantification of T cell subsets may provide useful information in the follow-up of individuals infected with HIV, particularly in assessing the indications for antiviral therapy, and its effects.

HIV Infections↗