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Biomedical subjects

K E Lundin

Publications and source records attributed to K E Lundin.

At least 19 recordsLinked to original sources

Adding functional entities to plasmids.

Non-viral gene therapy constitutes an alternative to the more common use of viral-mediated gene transfer. Most gene transfer methods using naked DNA are based upon non-sequence-specific interactions between the nucleic acid and cationic lipids (lipoplex) or polymers (polyplex). We have developed a technology in which functional entities hybridize in a sequence-specific manner to the nucleic acid (bioplex). This technology is still in its infancy, but has the potential to become a useful tool, since it allows the construction of highly defined complexes containing a variety of functional entities. In its present form the bioplex technology is based upon the use of peptide/nucleic acids (PNA) as anchors. Single, or multiple, functional entities are directly coupled to the anchors. By designing plasmids, or oligonucleotides, with the corresponding anchor target sequence, complexes with desired composition can easily be generated. The long-term aim is to combine functional entities in order to achieve optimal, synergistic interactions allowing enhanced gene transfer in vivo.

Cell Nucleus↗

Staining of celiac disease-relevant T cells by peptide-DQ2 multimers.

Gluten-specific T cells in the small intestinal mucosa are thought to play a central role in the pathogenesis of celiac disease (CD). The vast majority of these T cells recognize gluten peptides when presented by HLA-DQ2 (DQA1*05/DQB1*02), a molecule which immunogenetic studies have identified as conferring susceptibility to CD. We have previously identified and characterized three DQ2-restricted gluten epitopes that are recognized by intestinal T cells isolated from CD patients, two of which are immunodominant. Because almost all of the gluten epitopes are restricted by DQ2, and because we have detailed knowledge of several of these epitopes, we chose to develop peptide-DQ2 tetramers as a reagent to further investigate the role of these T cells in CD. In the present study, stable soluble DQ2 was produced such that it contained leucine zipper dimerization motif and a covalently coupled peptide. We have made four different peptide-DQ2 staining reagents, three containing the gluten epitopes and one containing a DQ2-binding self-peptide that provides a negative control for staining. We show in this study that peptide-DQ2 when adhered to plastic specifically stimulates T cell clones and that multimers comprising these molecules specifically stain peptide-specific T cell clones and lines. Interestingly, T cell activation caused severe reduction in staining intensities obtained with the multimers and an Ab to the TCR. The problem of TCR down-modulation must be taken into consideration when using class II multimers to stain T cells that may have been recently activated in vivo.

Baculoviridae↗

T cells from celiac disease lesions recognize gliadin epitopes deamidated in situ by endogenous tissue transglutaminase.

Celiac disease is an HLA-DQ2-associated disorder characterized by intestinal T cell responses to ingested wheat gliadins. Initial studies used gliadin that had been subjected to non-enzymatic deamidation during pepsin/trypsin digestion to enrich for the gliadin-specific T cells in small intestinal celiac biopsies. These T cells recognized synthetic gliadin peptides only after their deamidation in vitro by purified tissue transglutaminase (tTG). However, as these studies used a deamidated antigen for re-stimulation prior to testing for antigen specificity, this raised the possibility that T cells specific for native epitopes had not been expanded in vitro and had thus been overlooked. To address this possibility and to look for more direct evidence that endogenous tTG mediates deamidation of gluten in the celiac lesions, we have here used a minimally deamidated chymotrypsin-digest of gliadin to challenge biopsies and then investigated the specificity of the T cell lines derived from them. Interestingly, these T cell lines only barely responded to the chymotrypsin-digested gliadins, but efficiently recognized the in vitro tTG-treated variants of the same gliadins. Moreover, the addition of a tTG-inhibitor during the gliadin challenge often resulted in T cell lines with abolished or reduced responses to deamidated gliadin. These data demonstrate that DQ2-restricted T cells within adult celiac lesions predominantly recognize deamidated gliadin epitopes that are formed in situ by endogenous tTG.

Amides↗

Genes and environment in celiac disease.

Celiac disease is an intestinal disorder that develops as a result of interplay between genetic and environmental factors. HLA genes along with non-HLA genes predispose to the disease. Linkage studies have failed to identify chromosomal regions other than the HLA region which have major effects, indicating the existence of multiple non-HLA predisposing genes with modest effects. Association studies have shown that CTLA4 or a closely located gene is one of these genes. The primary HLA association in the majority of celiac disease patients is with DQ2 (DQA1*05/DQB1*02) and in the minority of patients with DQ8 (DQA1*0301/DQB1*0302). Gluten reactive CD4+ T cells can be isolated from small intestinal biopsies of celiac patients but not from controls. DQ2 or DQ8, but not other HLA molecules carried by patients, present peptides to these T cells. A number of distinct T cell gluten epitopes exist, most of them posttranslationally modified by deamidation. DQ2 and DQ8 bind the epitopes such that the glutamic acid residues created by deamidation are accommodated in pockets that have a preference for negatively charged side chains. There is evidence that deamidation in vivo is mediated by the enzyme tissue transglutaminase (tTG). Overall, the results point to control of the immune response to gluten by intestinal T cells restricted by the DQ2 or DQ8 molecules. This is likely to be a critical checkpoint for the development of celiac disease and could explain the dominant genetic role of HLA in this disorder. The products of the other predisposing genes may participate in pathway(s) that lead(s) to lesion formation. The minor genetic effects of the non-HLA genes could indicate a lack of critical checkpoints along these pathways, or that there are several pathways leading to the lesion formation.

Abatacept↗

Keratinocyte growth factor and coeliac disease.

BACKGROUND: Coeliac disease is characterised by increased epithelial renewal associated with a mucosal T cell response to gliadin. Keratinocyte growth factor (KGF) is produced by cytokine activated gut stromal cells and may be a link between mucosal T cell activation in untreated coeliac disease and epithelial hyperplasia. AIMS: To characterise expression of KGF in coeliac disease. METHODS: KGF transcripts in coeliac disease were measured by quantitative competitive reverse transcription-polymerase chain reaction (RT-PCR) and localised using in situ hybridisation. KGF production by gluten reactive CD4+ T cell clones was examined. In addition, KGF transcripts were measured following ex vivo challenge of coeliac biopsies with a peptic-tryptic digest of gliadin. RESULTS: KGF transcripts were elevated in coeliac biopsies compared with normal controls but were not different from non-coeliac disease controls. By in situ hybridisation, KGF mRNA containing cells were present in the upper half of the lamina propria, most abundantly just under the epithelium. There was no signal from cells within the epithelium. Gluten reactive T cell clones did not make KGF. In vitro challenge of coeliac biopsies generated a strong interferon gamma response but a specific KGF response could not be detected because of an extremely high number of KGF transcripts in all cultured biopsies. CONCLUSIONS: KGF is overexpressed in coeliac biopsies and in tissues with non-coeliac enteropathy. No evidence was found for KGF production by intraepithelial lymphocytes or lamina propria T cells.

Adolescent↗

The intestinal T cell response to alpha-gliadin in adult celiac disease is focused on a single deamidated glutamine targeted by tissue transglutaminase.

The great majority of patients that are intolerant of wheat gluten protein due to celiac disease (CD) are human histocompatibility leukocyte antigen (HLA)-DQ2(+), and the remaining few normally express HLA-DQ8. These two class II molecules are chiefly responsible for the presentation of gluten peptides to the gluten-specific T cells that are found only in the gut of CD patients but not of controls. Interestingly, tissue transglutaminase (tTG)-mediated deamidation of gliadin plays an important role in recognition of this food antigen by intestinal T cells. Here we have used recombinant antigens to demonstrate that the intestinal T cell response to alpha-gliadin in adult CD is focused on two immunodominant, DQ2-restricted peptides that overlap by a seven-residue fragment of gliadin. We show that tTG converts a glutamine residue within this fragment into glutamic acid and that this process is critical for T cell recognition. Gluten-specific T cell lines from 16 different adult patients all responded to one or both of these deamidated peptides, indicating that these epitopes are highly relevant to disease pathology. Binding studies showed that the deamidated peptides displayed an increased affinity for DQ2, a molecule known to preferentially bind peptides containing negatively charged residues. Interestingly, the modified glutamine is accommodated in different pockets of DQ2 for the different epitopes. These results suggest modifications of anchor residues that lead to an improved affinity for major histocompatibility complex (MHC), and altered conformation of the peptide-MHC complex may be a critical factor leading to T cell responses to gliadin and the oral intolerance of gluten found in CD.

Adult↗

Cross-reactive epitopes and HLA-restriction elements in human T cell recognition of the Mycobacterium leprae 18-kD heat shock protein.

We have previously demonstrated that the Mycobacterium leprae 18-kD heat shock protein (HSP18) is represented among the antigenic targets of human T cell responses induced by M. leprae immunization and that the peptide 38-50 serves as an immunodominant epitope recognized by CD4+ T cell clones. By using peripheral blood mononuclear cells and T cell lines from the same donor group, we have in this study shown that the M. leprae HSP18 and peptide 38-50 were recognized by memory T cells 8 years after immunization with M. leprae. The finding that M. bovis BCG-induced T cell lines responded to M. leprae HSP18, but not to the peptide 38-50, suggested the existence of additional T cell epitopes of a cross-reactive nature. Consistent with this, testing of the T cell lines for proliferative responses to the complete HSP18 molecule, truncated HSP18 (amino acid (aa) residues 38-148) and overlapping synthetic peptides, made it possible to identify two cross-reactive epitope regions defined by aa residues 1-38 and 41-55. While peptide 38-50-reactive T cell clones showed limited cross-reactivity by responding to M. leprae, M. avium and M. scrofulaceum, the T cell lines specific to the epitopes 1-38 and 41-55 were broadly cross-reactive, as demonstrated by their response to M. leprae, M. tuberculosis complex, M. avium and other mycobacteria. MHC restriction analysis of the HSP18-responding T cell lines showed that the epitopes 1-38 and 38-50 were presented by one of the two HLA-DR molecules expressed from self HLA-DRB1 genes, whereas the epitope 41-55 was recognized in the presence of autologous as well as HLA-DR and HLA-DQ mismatched allogeneic antigen-presenting cells. The results obtained in this study made it possible to identify cross-reactive T cell epitopes of the M. leprae HSP18, and provide an explanation for T cell recognition of this antigen in individuals infected with species of the M. tuberculosis complex or environmental mycobacteria.

Amino Acid Sequence↗

Identification and HLA restriction of naturally derived Th1-cell epitopes from the secreted Mycobacterium tuberculosis antigen 85B recognized by antigen-specific human CD4(+) T-cell lines.

Antigen 85B (Ag85B/MPT59) is a major secreted protein from Mycobacterium tuberculosis which is a promising candidate antigen for inclusion in novel subunit vaccines against tuberculosis (TB). The present study was undertaken to map naturally derived T-cell epitopes from M. tuberculosis Ag85B in relation to major histocompatibility complex (MHC) class II restriction. Antigen-specific CD4(+) T-cell lines were established from HLA-typed TB patients and Mycobacterium bovis BCG vaccinees by stimulation of peripheral blood mononuclear cells with purified Ag85B in vitro. The established T-cell lines were then tested for proliferation and gamma interferon (IFN-gamma) secretion in response to 31 overlapping synthetic peptides (18-mers) covering the entire sequence of the mature protein. The results showed that the epitopes recognized by T-cell lines from TB patients were scattered throughout the Ag85B sequence whereas the epitopes recognized by T-cell lines from BCG vaccinees were located toward the N-terminal part of the antigen. The T-cell epitopes represented by peptides p2 (amino acids [aa] 10 to 27), p3 (aa 19 to 36), and p11 (aa 91 to 108) were frequently recognized by antigen-specific T-cell lines from BCG vaccinees in both proliferation and IFN-gamma assays. MHC restriction analysis demonstrated that individual T-cell lines specifically recognized the complete Ag85B either in association with one of the self HLA-DRB1, DRB3, or DRB4 gene products or nonspecifically in a promiscuous manner. At the epitope level, panel studies showed that peptides p2, p3, and p11 were presented to T cells by HLA-DR-matched as well as mismatched allogeneic antigen-presenting cells, thus representing promiscuous epitopes. The identification of naturally derived peptide epitopes from the M. tuberculosis Ag85B presented to Th1 cells in the context of multiple HLA-DR molecules strongly supports the relevance of this antigen to subunit vaccine design.

Acyltransferases↗

Human T cell recognition of the Mycobacterium leprae LSR antigen: epitopes and HLA restriction.

We have in this work mapped epitopes and HLA molecules used in human T cell recognition of the Mycobacterium leprae LSR protein antigen. HLA typed healthy subjects immunized with heat killed M. leprae were used as donors to establish antigen reactive CD4+ T cell lines which were screened for proliferative responses against overlapping synthetic peptides covering the C-terminal part of the antigen sequence. By using this approach we were able to identify two epitope regions represented by peptide 2 (aa 29-40) and peptide 6 (aa 49-60), of which the former was mapped in detail by defining the N- and C-terminal amino acid positions necessary for T cell recognition of the core epitope. MHC restriction analysis showed that peptide 2 was presented to T cells by allogeneic cells coexpressing HLA-DR4 and DRw53 or DR7 and DRw53. In contrast, peptide 6 was presented to T cells only in the context of HLA-DR5 molecules. In conclusion, the M. leprae LSR protein antigen can be recognized by human T cells in the context of multiple HLA-DR molecules, of which none are reported to be associated with the susceptibility to develop leprosy. The results obtained are in support of using the LSR antigen in subunit vaccine design.

Amino Acid Sequence↗

Identification of promiscuous epitopes from the Mycobacterial 65-kilodalton heat shock protein recognized by human CD4(+) T cells of the Mycobacterium leprae memory repertoire.

By using a synthetic peptide approach, we mapped epitopes from the mycobacterial 65-kDa heat shock protein (HSP65) recognized by human T cells belonging to the Mycobacterium leprae memory repertoire. A panel of HSP65 reactive CD4(+) T-cell lines and clones were established from healthy donors 8 years after immunization with heat-killed M. leprae and then tested for proliferative reactivity against overlapping peptides comprising both the M. leprae and Mycobacterium tuberculosis HSP65 sequences. The results showed that the antigen-specific T-cell lines and clones established responded to 12 mycobacterial HSP65 peptides, of which 9 peptides represented epitopes crossreactive between the M. tuberculosis and M. leprae HSP65 (amino acids [aa] 61 to 75, 141 to 155, 151 to 165, 331 to 345, 371 to 385, 411 to 425, 431 to 445, 441 to 455, and 501 to 515) and 3 peptides (aa 343 to 355, 417 to 429, and 522 to 534) represented M. leprae HSP65-specific epitopes. Major histocompatibility complex restriction analysis showed that presentation of 9 of the 12 peptides to T cells were restricted by one of the 2 HLA-DR molecules expressed from self HLA-DRB1 genes, whereas 3 peptides with sequences completely identical between the M. leprae and M. tuberculosis HSP65 were presented to T cells by multiple HLA-DR molecules: peptide (aa 61 to 75) was presented by HLA-DR1, -DR2, and -DR7, peptide (aa 141 to 155) was presented by HLA-DR2, -DR7, and -DR53, whereas both HLA-DR2 and -DR4 (Dw4 and Dw14) were able to present peptide (aa 501 to 515) to T cells. In addition, the T-cell lines responding to these peptides in proliferation assays showed cytotoxic activity against autologous monocytes/macrophages pulsed with the same HSP65 peptides. In conclusion, we demonstrated that promiscuous peptide epitopes from the mycobacterial HSP65 antigen can serve as targets for cytotoxic CD4(+) T cells which belong to the human memory T-cell repertoire against M. leprae. The results suggest that such epitopes might be used in the peptide-based design of subunit vaccines against mycobacterial diseases.

Bacterial Proteins↗

[Cytomegalovirus as the cause of toxic dilatation of the colon].

Toxic dilatation of the colon is sometimes a complication which occurs during exacerbations of inflammatory bowel disease. It often requires immediate surgical intervention. We describe here a male patient with known ulcerative colitis who was investigated for fever of unknown cause, diarrhoea, and general illness. Upon admission he had only modest symptoms of colitis and received no immunosuppressive treatment. The condition worsened considerably, and subsequent colonoscopy demonstrated widespread lesions compatible with viral disease, but not with ulcerative colitis. Antiviral treatment for cytomegalovirus was started immediately, but progression of the condition with toxic dilatation called for a rapid colectomy. Histological examination showed widespread lesions compatible with cytomegalovirus infection. This clinical picture is rarely seen in immunocompetent patients.

Colectomy↗

Small intestinal T cells of celiac disease patients recognize a natural pepsin fragment of gliadin.

Celiac disease is a common severe intestinal disease resulting from intolerance to dietary wheat gluten and related proteins. The large majority of patients expresses the HLA-DQ2 and/or DQ8 molecules, and gluten-specific HLA-DQ-restricted T cells have been found at the site of the lesion in the gut. The nature of peptides that are recognized by such T cells, however, has been unclear so far. We now report the identification of a gliadin-derived epitope that dominantly is recognized by intestinal gluten-specific HLA-DQ8-restricted T cells. The characterization of such epitopes is a key step toward the development of strategies to interfere in mechanisms involved in the pathogenesis of celiac disease.

Amino Acid Sequence↗

Gluten induces an intestinal cytokine response strongly dominated by interferon gamma in patients with celiac disease.

BACKGROUND & AIMS: Celiac disease appears to be a T cell-mediated enteropathy induced by gluten in genetically predisposed individuals. Duodenal biopsy specimens from patients with celiac disease and histologically normal controls were investigated to see if cytokine expression is related to disease activity. METHODS: Cytokine messenger RNA (mRNA) expression was determined by quantitative reverse-transcription polymerase chain reaction and in situ expression by immunohistochemistry. RESULTS: In normal controls, mRNA levels were usually below the quantitative limit, even after in vitro gluten stimulation. By contrast, interferon (IFN)-gamma mRNA was increased more than 1000-fold in untreated disease. In vitro gluten stimulation of specimens from treated patients (gluten-free diet) increased IFN-gamma mRNA to the levels of untreated patients. In addition, increased mRNA levels for interleukin (IL)-2, IL-4, IL-6, and tumor necrosis factor alpha were found after such stimulation, whereas mRNA for IL-5, IL-10, and IL-12p40 was usually below the quantitative level. Biopsy specimens from untreated patients contained on average 10-fold more lamina propria cells positive for IFN-gamma than normal controls, whereas cells containing IL-4 were rare in both subject groups. CONCLUSIONS: The results show that mucosal gluten exposure in patients with celiac disease rapidly elicits high levels of IFN-gamma expression and lower levels of IL-2, IL-4, IL-6, and tumor necrosis factor alpha even in the virtual absence of IL-12.

Adolescent↗

CD4+ T cells with specific reactivity against astrovirus isolated from normal human small intestine.

BACKGROUND & AIMS: The gut is the largest immunologic organ in the human body, but little is known about the antigen specificity of mucosal T cells. This study sought to determine whether T cells resident in the duodenal mucosa could recognize astrovirus, a common and clinically important gastroenteritis virus. Serum antibodies against astrovirus are prevalent, indicating frequent viral exposure and postinfectious induction of systemic immune responses. Mucosal immune responses may conceivably mediate protection on astroviral reinfections. METHODS: Small intestinal biopsy specimens with normal histology were obtained from 8 adults and challenged in an organ culture system with inactivated human astrovirus. T cells activated by the viral challenge were isolated either by immunomagnetic positive selection of mucosal resident cells or by collecting cells emigrating into the culture supernatant. RESULTS: Astrovirus-specific, mucosal T-cell lines were isolated from all 8 subjects. Analysis of 29 CD4+ T-cell clones from 3 subjects showed predominant HLA-DR restriction of astrovirus responses. Most of the T-cell clones showed a Th1-like cytokine profile when restimulated with astrovirus. CONCLUSIONS: Helper T cells residing in normal, duodenal mucosa of adult subjects recognize a common enteropathogenic virus. These mucosal CD4+ T cells are presumably important in mucosal defense against recurrent astroviral infections.

Adult↗

Tissue transglutaminase selectively modifies gliadin peptides that are recognized by gut-derived T cells in celiac disease.

The action of tissue Transglutaminase (TGase) on specific protein-bound glutamine residues plays a critical role in numerous biological processes. Here we provide evidence for a new role of this enzyme in the common, HLA-DQ2 (and DQ8) associated enteropathy, celiac disease (CD). The intestinal inflammation in CD is precipitated by exposure to wheat gliadin in the diet and is associated with increased mucosal activity of TGase. This enzyme has also been identified as the main target for CD-associated anti-endomysium autoantibodies, and is known to accept gliadin as one of its few substrates. We have examined the possibility that TGase could be involved in modulating the reactivity of gliadin specific T cells. This could establish a link between previous reports of the role of TGase in CD and the prevailing view of CD as a T-cell mediated disorder. We found a specific effect of TGase on T-cell recognition of gliadin. This effect was limited to gliadin-specific T cells isolated from intestinal CD lesions. We demonstrate that TGase mediates its effect through an ordered and specific deamidation of gliadins. This deamidation creates an epitope that binds efficiently to DQ2 and is recognized by gut-derived T cells. Generation of epitopes by enzymatic modification is a new mechanism that may be relevant for breaking of tolerance and initiation of autoimmune disease.

Amino Acid Sequence↗