Nineteen percent of the global population may face a high probability of subsidence

Celiac disease, triggered by wheat gliadin and related prolamins from barley and rye, is characterized by a strong association with HLA-DQ2 and HLA-DQ8 genes. Gliadin is a mixture of many proteins that makes difficult the identification of major immunodominant epitopes. To address this issue, we expressed in Escherichia coli a recombinant α-gliadin (r-α-gliadin) showing the most conserved sequence among the fraction of α-gliadins. HLA-DQ8 mice, on a gluten-free diet, were intragastrically immunized with a chymotryptic digest of r-α-gliadin along with cholera toxin as adjuvant. Spleen and mesenteric lymph node T cell responses were analyzed for in vitro proliferative assay using a panel of synthetic peptides encompassing the entire sequence of r-α-gliadin. Two immunodominant epitopes corresponding to peptide p13 (aa 120–139) and p23 (aa 220–239) were identified. The response was restricted to DQ and mediated by CD4+ T cells. In vitro tissue transglutaminase deamidation of both peptides did not increase the response; furthermore, tissue transglutaminase catalyzed extensive deamidation in vitro along the entire r-α-gliadin molecule, but failed to elicit new immunogenic determinants. Surprisingly, the analysis of the cytokine profile showed that both deamidated and native peptides induced preferentially IFN-γ secretion, despite the use of cholera toxin, a mucosal adjuvant that normally induces a Th2 response to bystander Ags. Taken together, these data suggest that, in this model of gluten hypersensitivity, deamidation is not a prerequisite for the initiation of gluten responses.

The cloning and sequence determination is reported of the DNA region of Rhizobium leguminosarum coding for glutamine synthetase II (GSII). An open reading frame (ORF) encoding 326 amino acids was defined as the glnII gene on the basis of its similarity to other glnII genes and the ability of a DNA fragment carrying this ORF to complement the glutamine auxotrophy of a Klebsiella pneumoniae glnA mutant. We find that the glnII gene in R. leguminosarum is transcribed as a monocistronic unit from a single promoter, which shows structural features characteristic of rpoN (ntrA)-dependent promoters. In K. pneumoniae, such promoters require the ntrC and rpoN (ntrA) gene products for transcription. The intracellular level of glnII mRNA changes when R. leguminosarum is grown on different nitrogen sources, as expected for regulation by the nitrogen regulatory system. Promoter deletion analysis has shown that an extensive upstream DNA sequence (316 bp) is essential for in vivo activation of the glnII promoter in different biovars of R. leguminosarum. This DNA region requires a wild-type ntrC gene for activity and includes two conserved putative NtrC-binding site sequences. The results conclusively show that transcription from the R. leguminosarum glnII promoter is fully dependent on positive control by NtrC protein and on an upstream activator sequence (UAS).

In this work, the binding of the recombinant glutamine-binding protein (GlnBP) from Escherichia coli to gliadin peptides, toxic for celiac patients, was investigated by mass spectrometry experiments and optical techniques. Mass spectrometry experiments demonstrated that GlnBP binds the following amino acid sequence: XXQPQPQQQQQQQQQQQQL, present only into the toxic prolamines. The binding of GlnBP to gliadin suggested us to design a new optical biosensor based on nanostructured porous silicon (PSi) for the detection of trace amounts of gliadin in food. The GlnBP, which acts as a molecular probe for the gliadin, was covalently linked to the surface of the PSi wafer by a proper passivation process. The GlnBP-gliadin interaction was revealed as a shift in wavelength of the fringes in the reflectivity spectrum of the PSi layer. The GlnBP, covalently bonded to the PSi chip, selectively recognized the toxic peptide. Finally, the sensor response to the protein concentration was measured in the range 2.0-40.0 microg/L and the sensitivity of the sensor was determined.

Ammonia assimilation in Rhizobium leguminosarum biovar viceae strain RCRlOO 1 (hereafter called R . leguminosarum) appears to take place only through the glutamine synthetase/glutamate synthase pathway since (a) no glutamate dehydrogenase was detected in crude extracts of bacteria grown in different nitrogen sources, and (b) the growth rate on glutamine as a nitrogen source was faster than that observed on NH4Cl. In contrast to reports for other Rhizobium species, R . leguminosarum can definitely utilize NH4C1 for growth. R. Ieguminosarum contains two glutamine synthetase isoenzymes, GSI and GSII, which can be detected in the presence of each other by differential heat stability, or separated by affinity chromatography or immunoabsorption with an antiserum raised against pure GSI. GSII does not cross-react with an anti-GSI antiserum. GSI was shown to be reversibly adenylylated and it was also shown that adenylylation inhibits the biosynthetic activity of this enzyme, in a similar way to that reported for Escherichia coli glutamine synthetase and in contrast to that observed for glutamine synthetase of Rhizobium sp. strain ANU289. The apparent adenylylation level in different growth conditions changes from 21% to 99%, indicating a physiological role of this posttranslational modification in the in vivo regulation of GSI activity. The intracellular concentration of GSI varies very little when R . leguminosarum is grown on different nitrogen sources (twofold when measured by the transferase assay, or fourfold when measured by ELISA). In addition, the concentration of mRNA specific for GSI in different nitrogen sources does not show appreciable differences. The intracellular concentration of GSII varies from a specific activity value higher than 1000 when R . leguminosarum is grown on glutamate or nitrate, to an undetectable level when grown on NH4C1. When NH4C1 is added to a culture growing in glutamate, GSII activity is rapidly diluted out, suggesting a post-translational mechanism of enzyme inhibition or inactivation. Chloramphenicol prevents the disappearance of GSII activity, thus suggesting that protein synthesis is required for this process.

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Gliadin proteins are primarily responsible for celiac disease. As gliadin is a complex mixture of proteins difficult to solubilize and to extract from food, it is difficult to develop an assay capable of accurate quantization of gliadin in food for celiac patients. In this work, we present an advanced fluorescence assay for the detection of traces of gliadin in food. The described assay is based on measurement of the fluctuations of fluorescein-labeled gliadin peptides (GP) in a focused laser beam in the absence and in the presence of anti-GP antibodies. A competitive assay based on the utilization of unlabeled GP was developed. The obtained results indicate that the combination of high-avidity IgG antibodies together with the innovative fluorescence immunoassay strategy resulted in a gluten detection limit of 0.006 ppm, which it is much lower than the values reported in the literature.