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Biomedical subjects

Cesare Montecucco

Publications and source records attributed to Cesare Montecucco.

48 records · Page 3Linked to original sources
PubMed2002

Anthrax toxin: a tripartite lethal combination.

Anthrax is a severe bacterial infection that occurs when Bacillus anthracis spores gain access into the body and germinate in macrophages, causing septicemia and toxemia. Anthrax toxin is a binary A-B toxin composed of protective antigen (PA), lethal factor (LF), and edema factor (EF). PA mediates the entry of either LF or EF into the cytosol of host cells. LF is a zinc metalloprotease that inactivates mitogen-activated protein kinase kinase inducing cell death, and EF is an adenylyl cyclase impairing host defences. Inhibitors targeting different steps of toxin activity have recently been developed. Anthrax toxin has also been exploited as a therapeutic agent against cancer.

Animals↗
PubMed2002

Structure of the neutrophil-activating protein from Helicobacter pylori.

Helicobacter pylori is a major human pathogen associated with severe gastroduodenal diseases, including ulcers and cancers. An H.pylori protein that is highly immunogenic in humans and mice has been identified recently. This protein has been termed HP-NAP, due to its ability of activating neutrophils. In order to achieve a molecular understanding of its unique immunogenic and pro-inflammatory properties, we have determined its three-dimensional structure. Its quaternary structure is similar to that of the dodecameric bacterial ferritins (Dps-like family), but it has a different surface potential charge distribution. This is due to the presence of a large number of positively charged residues, which could well account for its unique ability in activating human leukocytes.

Bacterial Proteins↗
PubMed2002

Screening inhibitors of anthrax lethal factor.

The disease anthrax is caused by lethal factor, an enzyme component of the toxin produced by the spore-forming bacterium Bacillus anthracis. Here we describe substrate molecules for this factor that offer a means for high-throughput screening of potential inhibitors for use in anthrax treatment. Our assay should help to answer the urgent call for new and specific therapies to combat this pathogen after its recent emergence as a terrorist bioweapon.

Anthrax↗
PubMed2002

Structure of two iron-binding proteins from Bacillus anthracis.

Bacillus anthracis is currently under intense investigation due to its primary importance as a human pathogen. Particularly important is the development of novel anti-anthrax vaccines, devoid of the current side effects. A novel class of immunogenic bacterial proteins consists of dodecamers homologous to the DNA-binding protein of Escherichia coli (Dps). Two Dps homologous genes are present in the B. anthracis genome. The crystal structures of these two proteins (Dlp-1 and Dlp-2) have been determined and are presented here. They are sphere-like proteins with an internal cavity. We also show that they act as ferritins and are thus involved in iron uptake and regulation, a fundamental function during bacterial growth.

Amino Acid Sequence↗
PubMed2002

The neutrophil-activating protein (HP-NAP) of Helicobacter pylori is a potent stimulant of mast cells.

Infection by Helicobacter pylori causes an acute inflammatory response followed by a chronic infection of the human gastric mucosa. A neutrophil-activating protein (HP-NAP) has been identified in H.pylori, and its role in infection and immune response is currently under investigation. Here, we show that HP-NAP induces beta-hexosaminidase release and interleukin-6 production in peritoneal mast cells, two actions which are completely inhibited by pertussis toxin. We also show that in polarized epithelial cell monolayers HP-NAP translocates from the apical to the basolateral domain, where mast cells are located. These findings characterize HP-NAP as an inflammatory factor of H.pylori that is effective from the beginning of the inflammatory cascade.

Adenocarcinoma↗
PubMed2002

Botulinum neurotoxin serotypes A and C do not affect motor units survival in humans: an electrophysiological study by motor units counting.

OBJECTIVES: Botulinum neurotoxin serotype A (BoNT/A) is a valid therapy for dystonia but repeated BoNT/A injections may induce a clinical immuno-resistance that could be overcome by using other BoNT serotypes. In vitro experiments and our preliminary investigations in vivo, indicate that botulinum neurotoxin serotype C (BoNT/C) could be an effective alternative to BoNT/A. Moreover, in cultured neurons 'in vitro' BoNT/C has been reported to be more toxic than BoNT/A. METHODS: To verify this possibility, we compare the effect of BoNT/C and BoNT/A on the motor units count in humans by using the electrophysiological motor unit number estimation (MUNE) technique ('multiple point nerve stimulation'). Preliminarily, BoNT/C and BoNT/A dosage was calibrated in a mouse hemidiaphragm neuromuscular junction preparation. Subsequently, 8 volunteers were treated with 3IU of BoNT/C in the extensor digitorum brevis muscle of one foot and 3IU of BoNT/A in the contralateral one. Other 4 subjects were similarly injected at higher doses (10IU of BoNT/C or BoNT/A) to detect a possible dose-toxic effect. RESULTS: In both groups, no statistically significant variations in MUNE counting or single motor unit potential size were detected after 4 months from injections, when it was evident a recovery from the BoNTs blockade. CONCLUSIONS: We conclude that BoNT/C, similarly to BoNT/A, is safe and effective in humans and it could be proposed for a clinical use.

Animals↗
PubMed2002

The Vibrio cholerae haemolysin anion channel is required for cell vacuolation and death.

Several strains of Vibrio cholerae secrete a haemolytic toxin of 63 kDa, termed V. cholerae cytolysin (VCC). This toxin causes extensive vacuolation and death of cells in culture and forms an anion-selective channel in planar lipid bilayers and in cells. Here, we identify inhibitors of the VCC anion channel and show that the formation of the anion channel is necessary for the development of the vacuoles and for the cell death induced by this toxin. Using markers of cell organelles, we show that vacuoles derive from different intracellular compartments and we identify the contribution of late endosomes and of the trans-Golgi network in vacuole biogenesis.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2002

The neutrophil-activating protein of Helicobacter pylori.

Infection of the stomach mucosa by the gastric pathogen Helicobacter pylori is accompanied by a large infiltration of neutrophils and monocytes which are believed to contribute substantially to H. pylori-induced gastritis. A protein was identified (HP-NAP for neutrophil-activating protein from H. pylori) that was capable of increasing the adhesion of neutrophils to endothelial cells. We have demonstrated that HP-NAP is a dodecamer composed of identical 17-kDa subunits that induces the production of reactive oxygen radicals (ROIs) by neutrophils via a cascade of intracellular activation events. HP-NAP has also been shown to be chemotactic for neutrophils and monocytes, and a majority of H. pylori-infected patients have been found to produce antibodies specific for HP-NAP making it a strong vaccine candidate. More recently it has been shown that HP-NAP can stimulate tissue factor and plasminogen activator inhibitor-2 production by human monocytes. While structurally similar to the Escherichia coli DNA-binding protein Dps, HP-NAP has characteristics that are more similar to bacterioferritins being capable of binding up to 500 atoms of iron in vitro. Further study, however, has revealed that synthesis of HP-NAP in H. pylori is not altered by the addition or subtraction of metal ions from its growth medium suggesting that the primary role of the protein in vivo is not as a metal-binding protein. A number of other reports have proposed that HP-NAP acts as an adhesin being capable of binding several different compounds in vitro. Sequence analysis of the genomes of several other bacteria reveal that many possess Dps/HP-NAP-like proteins. The preliminary characterisation of some of these proteins will be discussed.

Animals↗
PubMed2002

Characterization and immunogenicity of the CagF protein of the cag pathogenicity island of Helicobacter pylori.

Helicobacter pylori infection causes severe gastroduodenal diseases in humans. Its virulence is strongly increased by the presence of the cag pathogenicity island (cag PAI). It has been shown that CagA, a major antigen in humans, is translocated to the host cell via a secretion system encoded by the cag PAI. The roles of many of the proteins encoded within the cag PAI are not known. Here we report on the cloning and expression of CagF, one of those proteins. We show that CagF is associated to the outer membrane of H. pylori G27 and that the protein is always expressed with electrophoretic mobility variations among the 20 strains tested here. We have also found that natural infection with H. pylori is able to induce antibodies against CagF.

Antibodies, Bacterial↗
PubMed1999

Helicobacter pylori VacA cytotoxin associated with the bacteria increases epithelial permeability independently of its vacuolating activity.

Polarized epithelial monolayers of Madin-Darby canine kidney (MDCK) cells were used to study the pathogenicity of Helicobater pylori, with an emphasis on the effect of VacA. The adherence of H. pylori to MDCK monolayers resulted in a decrease in trans-epithelial resistance (TER) across the cell monolayer. Isogenic vacA mutants did not lower the TER, demonstrating that the effect is strictly linked to the action of the toxin. A similar effect was observed with all VacA-producing strains, including those producing m2 toxins that are inactive in the vacuolating assay. In contrast to that seen with purified toxin, TER decrease was not enhanced by acid pH, which may indicate that the toxin associated to the bacterial surface is possibly in a monomeric state and therefore does not require a pH-induced conformation to be active. These data raise the possibility that one role of VacA in ulcerogenesis may consist of increasing the paracellular permeability of the gastric epithelium.

Animals↗
PubMed1998

SepA, the 110 kDa protein secreted by Shigella flexneri: two-domain structure and proteolytic activity.

Shigellosis is characterized by a strong inflammatory response which is induced by bacteria invading the colonic mucosa. Characterization of a sepA mutant indicated that SepA, the major protein secreted by Shigella flexneri growing in laboratory media, might be involved in invasion and destruction of the host intestinal epithelium. The sequence of the first 500 residues of mature SepA (110 kDa) is homologous to that of the N-terminal region of IgA1 proteases. To investigate the potential proteolytic activity of SepA, the activity of the purified protein on a wide range of synthetic peptides was tested. SepA hydrolysed several of these substrates and the activity was inhibited by PMSF. Several peptides which were hydrolysed by SepA have been described as specific substrates for cathepsin G, a serine protease produced by polymorphonuclear leukocytes that was proposed to play a role in inflammation. However, unlike cathepsin G, SepA degraded neither fibronectin nor angiotensin I and had no effect on aggregation of human platelets. In addition, analysis of SepA hydrolysis by proteinase K suggested that the protein is composed of two domains of about 450 residues separated by a hinge region of 100 residues. The 47 kDa N-terminal domain was stable and endowed with proteolytic activity.

Angiotensin I↗