Diverse Genetic Markers Concordantly Identify Bovine Origin Escherichia coli O157 Genotypes Underrepresented in Human Disease

Genetic markers previously reported to occur at significantly different frequencies in isolates of Escherichia coli O157:H7 obtained from cattle and from clinically affected humans concordantly delineate at least five genetic groups. Isolates in three of these groups consistently carry one or more markers rarely found among clinical isolates.Escherichia coli serotype O157:H7 is an important zoonotic pathogen that may cause diarrhea, bloody diarrhea, and hemolytic-uremic syndrome (3, 10, 14). E. coli O157 is transmitted to humans by direct contact with the animal reservoir (which includes cattle and other ruminant animals) or indirectly by ingestion of contaminated food or water (3, 10). Genetic analyses of bovine isolates of E. coli O157 from diverse geographic origins have provided evidence for the global dissemination of genotypes and also for significant regional differences in the relative prevalence of some genotypes (5, 8, 18, 19).Several research groups have identified genetic markers that occur at different relative frequencies among E. coli O157 isolates from human clinical cases and from cattle. One group initially used octamer-based genomic scanning to identify two lineages of U.S. origin E. coli O157 (7), of which lineage I was composed mostly (36/44) of clinical isolates and lineage II was composed mostly (25/32) of cattle isolates. Subsequently, a simpler multiplex PCR-based assay (Table ​(Table1),1), the lineage-specific polymorphism assay (LSPA), was developed to indentify these lineages (19). Six LSPA loci with alleles characteristic of lineage I, lineage II, or neither lineage I nor lineage II are, respectively, classified with the digit 1, 2, or 3, and these digits are concatenated to an LSPA code: 111111 indicates lineage I, and 211111 indicates a genetically intermediate group termed lineage I/II (20), whereas all other genotype variations are considered to belong to lineage II. More recently, a typing assay based on Shiga toxin-encoding bacteriophage insertion (SBI) sites grouped 91 of 92 clinical E. coli O157 isolates from the northwestern United States into three clusters, of which clusters 1 and 3 predominated (>90%) (16). SBI consists of six PCRs (Table ​(Table1)1) that amplify the Stx toxin genes and the insertion site junctions of the Stx1- and Stx2-encoding bacteriophages of E. coli O157. In a subsequent study, the predominance (92.6%) of clusters 1 and 3 was confirmed in 190 additional human (clinical) isolates (1). In contrast, many (48.8%) E. coli O157 isolates from cattle in the northwestern United States and western Canada demonstrated SBI patterns rarely found among human (clinical) isolates (1).

TABLE 1.

Oligonucleotides used in this study

Cyclosporin A-treated dendritic cells may affect the outcome of organ transplantation by decreasing CD4+CD25+ regulatory T cell proliferation

One of the mechanisms for generation of tolerance involves immature dendritic cells (DCs) and a subpopulation of regulatory CD4+ CD25+ T lymphocytes (T REG). The purpose of this work was to analyze how Cyclosporine A (CsA), a widely used immunosuppressive drug, may affect T REG proliferation. Purified and activated murine DCs obtained from bone marrow precursors differentiated with rGMCSF were co-cultured with purified CFSE-labeled T REG from OTII mice, and their phenotype and proliferation analyzed by flow cytometry. Our data indicate that DCs differentiated in the presence of CsA show an altered phenotype, with a lower expression of MHC-II and a lower activating capacity. Additionally, these CsA-treated DCs show decreased production of IL-2 and IL-12 and increased IL-10 secretion when stimulated with LPS, indicating an effect on the polarization of the immune response. Interestingly, CsA-treated DCs show an anti-tolerogenic effect since they reduce the proliferation of T REG cells from 72 to 47%. Further inhibition to a 24% of T REG proliferation was obtained as a direct effect of CsA on T REG. In conclusion, the anti-tolerogenic effect of CsA should be considered in the planning of immunosuppression in the context of clinical transplantation.     

Generation of tissue-specific and promiscuous HLA ligand databases using DNA microarrays and virtual HLA class II matrices.

Most pockets in the human leukocyte antigen-group DR (HLA-DR) groove are shaped by clusters of polymorphic residues and, thus, have distinct chemical and size characteristics in different HLA-DR alleles. Each HLA-DR pocket can be characterized by "pocket profiles," a quantitative representation of the interaction of all natural amino acid residues with a given pocket. In this report we demonstrate that pocket profiles are nearly independent of the remaining HLA-DR cleft. A small database of profiles was sufficient to generate a large number of HLA-DR matrices, representing the majority of human HLA-DR peptide-binding specificity. These virtual matrices were incorporated in software (TEPITOPE) capable of predicting promiscuous HLA class II ligands. This software, in combination with DNA microarray technology, has provided a new tool for the generation of comprehensive databases of candidate promiscuous T-cell epitopes in human disease tissues. First, DNA microarrays are used to reveal genes that are specifically expressed or upregulated in disease tissues. Second, the prediction software enables the scanning of these genes for promiscuous HLA-DR binding sites. In an example, we demonstrate that starting from nearly 20,000 genes, a database of candidate colon cancer-specific and promiscuous T-cell epitopes could be fully populated within a matter of days. Our approach has implications for the development of epitope-based vaccines.     

Peripheral benzodiazepine receptor agonists exhibit potent antiapoptotic activities

The peripheral benzodiazepine receptor (PBR) has been implicated in several mitochondrial functions but the exact physiological role of this receptor is still under debate. Since the mitochondria have been attributed a central role in cell death, we have determined the effects of various PBR agonists and antagonists on the apoptosis of the human lymphoblastoid cell line U937. On this cell type, the PBR agonist Ro5-4864 was found to strongly protect the cells against apoptosis induced by TNFalpha. The antiapoptotic effect of PBR agonists was due to a selective interaction with the PBR as demonstrated by: (1) a close correlation between the antiapoptotic activity of various PBR agonists and their respective affinity for the PBR determined on the same cells, (2) a lack of effect of central benzodiazepine receptors agonists such as clonazepam on cell survival, (3) the lack of an antiapoptotic activity of Ro5-4864 on wild-type Jurkat cells (lacking the PBR receptor) and the reappearance of this effect on PBR-transfected Jurkat cells, and (4) the blockade of the antiapoptotic effect of PBR agonists by a selective PBR antagonist. The present results therefore indicate that PBR agonists are potent antiapoptotic compounds and show that this effect might represent a major function for this enigmatic receptor.     

Heterodimerization with vascular endothelial growth factor receptor-2 (VEGFR-2) is necessary for VEGFR-3 activity

VEGFR-3 is essential for vascular development and maintenance of lymphatic vessel's integrity. Little is known about its cooperative effect with other receptors of the same family. Contrary to VEGFR-2, stimulation of VEGFR-3 by VEGF-C and -D failed to enhance its phosphorylation either in HEK293T or in PAE cells. These ligands were unable to induce angiogenesis of PAEC expressing VEGFR-3 alone. In the presence of VEGFR-2, VEGF-C and -D induced heterodimerization of VEGFR-3 with VEGFR-2. This heterodimerization was associated with enhanced VEGFR-3 phosphorylation and subsequent cellular responses as evidenced by the formation of capillary-like structures in PAE cells and proliferation of primary human endothelial cells expressing both receptors. Taken together, these results show for the first time that VEGFR-3 needs to be associated to VEGFR-2 to induce ligand-dependent cellular responses.     

A genomewide scan identifies novel early-onset primary open-angle glaucoma loci on 9q22 and 20p12

Glaucoma is a leading cause of blindness worldwide. The disease is characterized by a degeneration of the optic nerve, which is usually associated with elevated intraocular pressure. The common form of adult-onset primary open-angle glaucoma is inherited as a complex trait, whereas the rarer early-onset juvenile open-angle glaucoma (JOAG) exhibits autosomal dominant inheritance. Of all cases of JOAG, approximately 10%-20% are caused by mutations in the myocilin gene. We have identified 25 pedigrees that are affected with typical JOAG and that demonstrate autosomal dominant inheritance. We sequenced the myocilin gene in probands from each family and found mutations in 8% of this population. To identify novel genes responsible for JOAG, we used families that did not have myocilin mutations for a genomewide screen. Markers located on chromosomes 9q22 and 20p12 showed evidence for linkage, identifying two novel loci for early-onset open-angle glaucoma.     

Aminoacid profile and oxidative status in children affected by Down syndrome before and after supplementary nutritional treatment

Down syndrome is the most common autosomal aberration among liveborns, characterised by several clinical features and metabolic disturbances. Aminoacid pathways abnormalities and defective oxidative balance are the most common metabolic problems in Down Syndrome. To evaluate the biochemical responses of children with Down Syndrome to a nutritional regimen supplemented with aminoacids, vitamins and polyunsaturated fatty acids, we submitted 86 subjects divided in two groups (0-6 and 6-12 years) to the dosage of plasma levels of aminoacids, antioxidant enzymes activities and reactive oxygen species, before and after 12 months of such nutritional supplementation and in relation to normal controls. The results obtained showed a tendency towards the values of normal subjects with statistically significant differences. Although other studies must be performed to confirm and define such report, our experience supports the usefulness of a nutritional supplementation with aminoacids, vitamins and polyunsaturated fatty acids, also considering the absence of side effects.     

Mycobacterium tuberculosis chaperonin 10 is secreted in the macrophage phagosome: is secretion due to dissociation and adoption of a partially helical structure at the membrane?

To confirm that Mycobacterium tuberculosis chaperonin 10 (Cpn10) is secreted outside the live bacillus, infected macrophages were examined by electron microscopy. This revealed that the mycobacterial protein accumulates both in the wall of the bacterium and in the matrix of the phagosomes in which ingested mycobacteria survive within infected macrophages. To understand the structural implications underlying this secretion, a structural study of M. tuberculosis Cpn10 was performed under conditions that are generally believed to mimic the membrane environment. It was found that in buffer-organic solvent mixtures, the mycobacterial protein forms two main species, namely, a partially helical monomer that prevails in dilute solutions at room temperature and a dimer that folds into a beta-sheet-dominated structure and prevails in either concentrated protein solutions at room temperature or in dilute solutions at low temperature. A partially helical monomer was also found and was completely associated with negatively charged detergents in a micelle-bound state. Remarkably, zwitterionic lipids had no effect on the protein structure. By using N- and C-truncated forms of the protein, the C- and N-terminal sequences were identified as possessing an amphiphilic helical character and as selectively associating with acidic detergent micelles. When the study was extended to other chaperonins, it was found that human Cpn10 is also monomeric and partially helical in dilute organic solvent-buffer mixtures. In contrast, Escherichia coli Cpn10 is mostly dimeric and predominately beta-sheet in both dilute and concentrated solutions. Interestingly, human Cpn10 also crosses biological membranes, whereas the E. coli homologue is strictly cytosolic. These results suggest that dissociation to partially helical monomers and interaction with acidic lipids may be two important steps in the mechanism of secretion of M. tuberculosis Cpn10 to the external environment.