Cellular hypersensitivity to a synthetic dodecapeptide derived from human adenovirus 12 which resembles a sequence of A-gliadin in patients with coeliac disease

Respiratory virus-induced heterologous immunity: Part of the problem or part of the solution?

Purpose

To provide current knowledge on respiratory virus-induced heterologous immunity (HI) with a focus on humoral and cellular cross-reactivity. Adaptive heterologous immune responses have broad implications on infection, autoimmunity, allergy and transplant immunology. A better understanding of the mechanisms involved might ultimately open up possibilities for disease prevention, for example by vaccination.

Methods

A structured literature search was performed using Medline and PubMed to provide an overview of the current knowledge on respiratory-virus induced adaptive HI.

Results

In HI the immune response towards one antigen results in an alteration of the immune response towards a second antigen. We provide an overview of respiratory virus-induced HI, including viruses such as respiratory syncytial virus (RSV), rhinovirus (RV), coronavirus (CoV) and influenza virus (IV). We discuss T cell receptor (TCR) and humoral cross-reactivity as mechanisms of HI involving those respiratory viruses. Topics covered include HI between respiratory viruses as well as between respiratory viruses and other pathogens. Newly developed vaccines, which have the potential to provide protection against multiple virus strains are also discussed. Furthermore, respiratory viruses have been implicated in the development of autoimmune diseases, such as narcolepsy, Guillain-Barré syndrome, type 1 diabetes or myocarditis. Finally, we discuss the role of respiratory viruses in asthma and the hygiene hypothesis, and review our recent findings on HI between IV and allergens, which leads to protection from experimental asthma.

Conclusion

Respiratory-virus induced HI may have protective but also detrimental effects on the host. Respiratory viral infections contribute to asthma or autoimmune disease development, but on the other hand, a lack of microbial encounter is associated with an increasing number of allergic as well as autoimmune diseases. Future research might help identify the elements which determine a protective or detrimental outcome in HI-based mechanisms.

Respiratory virus-induced heterologous immunity: Part of the problem or part of the solution?

Purpose

To provide current knowledge on respiratory virus-induced heterologous immunity (HI) with a focus on humoral and cellular cross-reactivity. Adaptive heterologous immune responses have broad implications on infection, autoimmunity, allergy and transplant immunology. A better understanding of the mechanisms involved might ultimately open up possibilities for disease prevention, for example by vaccination.

Methods

A structured literature search was performed using Medline and PubMed to provide an overview of the current knowledge on respiratory-virus induced adaptive HI.

Results

In HI the immune response towards one antigen results in an alteration of the immune response towards a second antigen. We provide an overview of respiratory virus-induced HI, including viruses such as respiratory syncytial virus (RSV), rhinovirus (RV), coronavirus (CoV) and influenza virus (IV). We discuss T cell receptor (TCR) and humoral cross-reactivity as mechanisms of HI involving those respiratory viruses. Topics covered include HI between respiratory viruses as well as between respiratory viruses and other pathogens. Newly developed vaccines which have the potential to provide protection against multiple virus strains are also discussed. Furthermore, respiratory viruses have been implicated in the development of autoimmune diseases, such as narcolepsy, Guillain–Barré syndrome, type 1 diabetes or myocarditis. Finally, we discuss the role of respiratory viruses in asthma and the hygiene hypothesis, and review our recent findings on HI between IV and allergens, which leads to protection from experimental asthma.

Conclusion

Respiratory-virus induced HI may have protective but also detrimental effects on the host. Respiratory viral infections contribute to asthma or autoimmune disease development, but on the other hand, a lack of microbial encounter is associated with an increasing number of allergic as well as autoimmune diseases. Future research might help identify the elements which determine a protective or detrimental outcome in HI-based mechanisms.

Coeliac disease and alopecia areata in childhood

Coeliac disease is a genetic, immunologically mediated small bowel enteropathy that causes malabsorption. The immune inflammatory response to gluten frequently causes damage to many other tissues of the body. We report the association of coeliac disease and alopecia areata in two children, a 13-year-old girl and a 29-month-old girl. Both of our patients had immunoglobulin A (IgA) class endomysial antibodies, IgA and immunoglobulin G (IgG) antigliadin antibodies and subtotal villous atrophy on jejunal biopsy. Administration of a gluten-free diet to our patients resulted in complete hair growth and improved the gastrointestinal symptoms.

31-43 amino acid sequence of the alpha-gliadin induces anti-endomysial antibody production during in vitro challenge

BACKGROUND

Wheat gliadin is the culprit antigen of coeliac disease (CD). Two short sequences of NH2-terminal portion of gliadin seem to be responsible for CD. Antiendomysial antibodies (EMA), highly sensitive and specific for CD, are detectable in the culture media from treated CD patients, after in vitro challenge with peptic-tryptic (PT) digest of gliadin. In this study we detected EMA production after in vitro challenge with 31-43 peptide. We used 56-68 peptide, lacking toxic sequences, as a negative control.

METHODS

Duodenal samples from 11 treated CD patients and 9 control patients were cultured with 31-43 and 56-68 peptides and PT gliadin. Indirect immunofluorescence analysis was used for EMA detection.

RESULTS

EMA were detected in culture media of 10 of 11 specimens challenged with PT-gliadin and in the media of all specimens challenged with 31-43 peptide. No EMA were detectable in any treated patients cultured with 56-68 peptide or with medium alone. No EMA were observed in cultures of control specimens.

DISCUSSION

The ability of the 31-43 sequence of the alpha-gliadin to induce EMA production suggests its involvement in the pathogenesis of CD. Furthermore, it may be a more useful antigenic substance than PT gliadin for both in vitro and in vivo studies of CD.

Glutenin is involved in the gluten-driven mucosal T cell response

Gluten ingestion causes coeliac disease in susceptible individuals. Gluten is a heterogeneous mixture of glutenin and gliadin, the latter of which is considered responsible for disease induction. By combining high-performance liquid chromatography purification steps of gluten with a T cell bioassay and mass spectral analyses, we have identified a glutenin peptide (glt04 707-742) that activates T cells from the small intestine of a coeliac disease patient and results in the secretion of large amounts of IFN-gamma. The minimal T cell stimulatory core of the peptide (residues 724-734) is repetitively present in glutenin molecules. Moreover, it was observed that a large number of naturally occurring variants of this peptide are recognized by the T cells. These data suggest that the large heterogeneity of glutenin proteins dramatically increases the number of available T cell epitopes. Together, the results provide new insight into the nature of the gluten antigens that lead to coeliac disease and suggest that glutenin, next to gliadin-derived antigens, may be involved in the disease process.

In vitro screening of food peptides toxic for coeliac and other gluten-sensitive patients: a review

Experience gained through investigations on coeliac disease makes it possible to propose a screening method based on agglutination of isolated K562(S) cells to evaluate the occurrence in food protein of amino acid sequences that are able to adversely affect coeliac and related gluten-sensitive patients. The method consists of in vitro sequential peptic and tryptic digestion of food protein fractions under optimal pH, temperature and time conditions and in vitro incubation of the digest with K562(S) cells; the toxic potential is detected as an agglutination of K 562 (S) cells after a short incubation. Other in vitro test systems, including atrophic coeliac intestinal mucosa and rat fetal intestine, can be used to confirm the results obtained with the isolated cells. A fractionation step of the proteolytic digest on a sepharose-mannan column before exposure of the in vitro systems to the separated peptide fractions adds to the sensitivity of the method. This screening method is not only very useful to investigate action mechanisms in coeliac disease, but also to assess the safety of genetically-modified plant foods and novel foods for gluten-sensitive patients.

Use of Complete Eluted Peptide Sequence Data from HLA-DR and -DQ Molecules to Predict T Cell Epitopes, and the Influence of the Nonbinding Terminal Regions of Ligands in Epitope Selection

In diseases with a strong association with an HLA haplotype, identification of relevant T cell epitopes may allow alteration of the pathologic process. In this report we use a reverse immunogenetic approach to predict possible HLA class II-restricted T cell epitopes by using complete pool sequencing data. Data from HLA-DR2(B1*1501), -DR3(B1*0301), -DQ2(A1*0501, B1*0201), and -DQ8(A1*0301, B1*0302) alleles were used by a computer program that searches a candidate protein to predict ligands with a relatively high probability of being processed and presented. This approach successfully identified both known T cell epitopes and eluted single peptides from the parent protein. Furthermore, the program identified ligands from proteins in which the binding motif of the HLA molecule was unable to do so. When the information from the nonbinding N- and C-terminal regions in the pool sequence was removed, the ability to predict several ligands was markedly reduced, particularly for the HLA-DQ alleles. This suggests a possible role for these regions in determining ligands for HLA class II molecules. Thus, the use of complete eluted peptide sequence data offers a powerful approach to the prediction of HLA-DQ and -DR peptide ligands and T cell epitopes.

Is celiac disease due to molecular mimicry between gliadin peptide-HLA class II molecule-T cell interactions and those of some unidentified superantigen?

This paper presents a new hypothesis for the etiology and pathogenesis of celiac disease (CD). It is our contention that CD is triggered by the binding of one or more gliadin peptides to CD-associated HLA class II molecules. Furthermore, we propose that these putative CD peptides bind to oligosaccharide residues on HLA class II molecules distal to the peptide-binding groove invoking recognition and binding by specialized subsets of gamma delta T cell receptor-bearing lymphocytes. The binding of these gamma delta T cells serves as a signal for abrogation of oral tolerance to ingested proteins setting in motion a series of immune responses directed against the small intestinal epithelium of CD patients. CD patients are victimized by this self-distructed immune response because of inheritance of certain combinations of HLA-DQ and DR haplotypes. Dimers encoded by HLA-DR haplotypes may be the primary restriction elements for lectin-like, gliadin peptides while the degree of immune suppression (or lack thereof) to ingested gliadins is governed by inherited HLA-DQ haplotypes. Finally, we speculate that molecular mimicry between one or more gliadin peptides and some, as yet unidentified, bacterial or viral superantigen plays a role in disease pathogenesis.

Relation between gliadin structure and coeliac toxicity

Gliadin, the alcohol-soluble protein fraction of wheat, contains the factor toxic for coeliac patients. The numerous components of gliadin can be classified according to their primary structure into omega 5-, omega 1,2-, alpha- and gamma-type. Both omega-types have almost entirely repetitive amino acid sequences consisting of glutamine, proline and phenylalanine. alpha- and gamma-type gliadins contain four and five different domains, respectively, and are homologous within the domains III and V. Unique for each alpha- and gamma-type is domain I, which consists mostly of repetitive sequences rich in glutamine, proline and aromatic amino acids. Coeliac toxicity of gliadin is not destroyed by digestion with gastropancreatic enzymes. In vivo testing established the toxicity of alpha-type gliadins and in vitro testing of gliadin peptides revealed that domain I of alpha-type gliadins is involved in activating coeliac disease. The sequences -Pro-Ser-Gln-Gln- and -Gln-Gln-Gln-Pro- were demonstrated to be common for toxic gliadin peptides. Most of the in vivo and in vitro studies of synthetic peptides confirmed the importance of one or both of these sequences. Cultivated hexaploid, tetraploid and diploid wheat species do not differ significantly in potential toxic sequences of alpha-type gliadins.

In vitro toxicity of gluten peptides in coeliac disease assessed by organ culture

BACKGROUND

We have used organ culture to investigate the in vitro toxicity of three oligopeptides corresponding to amino acids 31-49 (peptide A), 202-220 (peptide B), and 3-21 (peptide C) of A-gliadin, Frazer's fraction III (FFIII), and ovalbumin.

METHODS

Eight to 14 jejunal biopsy specimens were obtained from each of 8 treated and 7 untreated coeliac patients and 5 normal controls and cultured for 18 h in organ culture with test peptide (1 mg/ml) or medium alone. Mean enterocyte cell heights (ECH) were compared with paired values for specimens grown in medium alone.

RESULTS

A significant reduction in the mean of the ECH values for each of the patient groups was observed with peptide A and FFIII in both treated (p = 0.01 and 0.02, respectively) and untreated (p = 0.03 and 0.01) coeliac patients when compared with tissue incubated with medium alone. No significant changes in the mean ECH value were noted in any of the patient groups in tissue incubated with peptide B, peptide C, or ovalbumin as compared with those with medium alone.

CONCLUSIONS

These results suggest that peptide A is toxic in vitro to the jejunal mucosa of both treated and untreated coeliac patients, correlating with recent findings that this peptide exacerbates coeliac disease in vivo.

T-cell responses and cellular immunity in coeliac disease

Increasing evidence points to a direct role for T cells in the mediation of the coeliac intestinal lesion. There is good evidence for increased local T-cell reactivity, manifest as increased in T-cell activation in the lamina propria and T-cell proliferation in the epithelial compartment. A likely scenario is that gluten elicits antigen-specific responses by lamina propria T helper cells, probably of the Th1 (inflammatory-mediator) subtype, leading to secretion of pro-inflammatory cytokines. Such cytokines may have direct effects on intestinal enterocytes, as well as mediating indirect effects by upregulation of MHC antigens and by enhancing the activity of cytolytic T cells. Although gluten-specific IEL responses have not been demonstrated by intraepithelial T lymphocytes (IELs), increasing evidence suggests that IELs can act as cytolytic effector cells and hence are likely to exert enteropathic effects under the influence of pro-inflammatory cytokines.

The precipitating factor in coeliac disease

In recent years, remarkable progress has been made in the elucidation of cereal protein structure and its relation to coeliac toxicity. Gluten proteins of wheat can be classified according to their primary structure into high-, medium- and low-molecular-weight (HMW, MMW, LMW) groups. Each of these groups contains two or three different protein types having partly homologous, partly unique, structural elements: chi- and gamma-type HMW subunits of glutenin (HMW group), omega 5 and omega 1,2-type gliadins (MMW group) and alpha-type gliadins, gamma-type gliadins and LMW subunits of glutenin (LMW group). Numerous proteins from the same type do exist with only a few modifications of the amino-acid sequence. The structure of the HMW and LMW group proteins can be divided into three and five domains, respectively. Most typical for each type and unique for cereals are the glutamine- and proline-rich domains containing repetitive sequences (HMW group: domain B; LMW group: domain I). omega-type gliadins consist almost entirely of repetitive sequences. Rye and barley, closely related to wheat, have protein types homologous to those of wheat. Early investigations showed that wheat gluten and, in particular, the alcohol-soluble gliadin fraction contained the factor toxic for coeliac patients. Equivalent protein fractions of rye, barley and probably oats were also considered to be toxic. The effects of toxic proteins were not destroyed by digestion with pepsin, trypsin and pancreatin. In-vivo (instillation) testing established the toxicity of alpha-type gliadins, and in-vitro (organ culture) testing of gliadin peptides demonstrated that the N-terminal region (domain I) of alpha-type gliadins is involved in activating coeliac disease. The longest sequences common for toxic peptides were found to be -Pro-Ser-Gln-Gln- and -Gln-Gln-Gln-Pro-. Various in-vitro tests and two in-vivo studies on synthetic peptides support the importance of one or both of these sequences. They do not occur in non-toxic food proteins and are characterized by their ability to form a beta-turn conformation. Although these sequences are probably not sufficient for toxicity in themselves, and other amino-acid residues are additionally required, they could serve as the starting point for further investigation.

Coeliac disease: characterisation of monoclonal antibodies raised against a synthetic peptide corresponding to amino acid residues 206-217 of A-gliadin

A dodecapeptide of A-gliadin, which shares amino acid homologies with the E1b protein of adenovirus 12, was used to produce murine monoclonal antibodies. Five monoclonal antibodies were produced and were screened by enzyme linked immunosorbant assay, immunodot assay, and immunoblotting. The antibodies were tested against whole wheat gliadin and its alpha, beta, gamma, and omega subfractions, and the prolamins of rye, barley, oats, maize, millet, rice, and sorghum. Four of the five antibodies cross reacted with one or more of the coeliac non-toxic cereals--maize, millet, sorghum, and rice. The monoclonal antibody that did not cross react with these non-toxic cereals, did not recognize Frazer's fraction III, a peptic-tryptic digest of wheat gluten which is known to be toxic. The results suggest that the A-gliadin dodecapeptide shares a region of homology with cereals that do not exacerbate coeliac disease. This study does not support the hypothesis that prior infection with adenovirus 12 is a precipitating factor in coeliac disease.

Is persistent adenovirus 12 infection involved in coeliac disease? A search for viral DNA using the polymerase chain reaction

It has been shown that partial amino acid sequence homology between alpha gliadin and an early region protein (E1B-58 kDa) of adenovirus 12 results in immunological cross reaction. This led to the proposal that prior infection by adenovirus 12 could be associated with the development of coeliac disease. To examine this hypothesis, evidence was sought of persistent adenovirus 12 infection in the small intestinal mucosa of patients with coeliac disease. DNA isolated from biopsy samples from 24 control and 18 coeliac disease patients was analysed by the polymerase chain reaction for adenovirus 12 DNA encoding the E1B-58 kDa protein. Four of 18 coeliac disease and two of 24 control patients were positive. There is thus a low prevalence of this infection on both groups of patients but certainly no significantly increased incidence in coeliac disease. These results suggest that persistent adenovirus 12 infection is not a major element in the pathogenesis of coeliac disease.

In vivo toxicity of a synthetic dodecapeptide from A gliadin in patients with coeliac disease

A single dose of a synthetic peptide of A gliadin (residues 206-217) sharing homology with the E1b protein of adenovirus 12 was instilled intraduodenally in two treated coeliac patients. Biopsy specimens were taken before and repeatedly up to 24 h after the instillation by means of a Quinton hydraulic multiple biopsy instrument and processed for histology, morphometry (intraepithelial lymphocyte counts, crypt-to-villus ratio), immunocytochemistry, electron microscopy, and disaccharidase assays. Two subjects with irritable bowel syndrome served as controls. In the coeliac group disaccharidase activities decreased at 24 h, and abnormalities were seen on light and electron microscopy and in morphometric measurements. The lamina propria became infiltrated with mononuclear cells after 2 h, and there was also a rise in IgA-containing cells in one patient. No such abnormalities were seen in the control group. The serum concentrations of C3, C4, and C1 esterase inhibitor remained unchanged. Thus, the dodecapeptide may be one epitope of gliadin mediating the pathogenesis of coeliac disease.