RÉSUMÉ
The exotoxins TcdA and TcdB are the major virulence factors of Clostridium difficile. Circulating neutralizing antitoxin antibodies are protective in C. difficile infection (CDI), as demonstrated, in part, by the protective effects of actoxumab and bezlotoxumab, which bind to and neutralize TcdA and TcdB, respectively. The question of how systemic IgG antibodies neutralize toxins in the gut lumen remains unresolved, although it has been suggested that the Fc receptor FcRn may be involved in active antibody transport across the gut epithelium. In this study, we demonstrated that genetic ablation of FcRn and excess irrelevant human IgG have no impact on actoxumab-bezlotoxumab-mediated protection in murine and hamster models of CDI, suggesting that Fc-dependent transport of antibodies across the gut wall is not required for efficacy. Tissue distribution studies in hamsters suggest, rather, that the transport of antibodies depends on toxin-induced damage to the gut lining. In an in vitro two-dimensional culture system that mimics the architecture of the intestinal mucosal epithelium, toxins on the apical side of epithelial cell monolayers are neutralized by basolateral antibodies, and antibody transport across the cell layer is dramatically increased upon addition of toxin to the apical side. Similar data were obtained with F(ab')2 fragments, which lack an Fc domain, consistent with FcRn-independent paracellular, rather than transcellular, transport of antibodies. Kinetic studies show that initial damage caused by apical toxin is required for efficient neutralization by basolateral antibodies. These data may represent a general mechanism of humoral response-mediated protection against enteric pathogens.
Sujet(s)
Anticorps antibactériens/immunologie , Anticorps neutralisants/immunologie , Antitoxines/immunologie , Protéines bactériennes/toxicité , Toxines bactériennes/toxicité , Entérotoxines/toxicité , Animaux , Anticorps antibactériens/métabolisme , Anticorps antibactériens/usage thérapeutique , Anticorps neutralisants/métabolisme , Anticorps neutralisants/usage thérapeutique , Antitoxines/métabolisme , Antitoxines/usage thérapeutique , Protéines bactériennes/immunologie , Toxines bactériennes/immunologie , Clostridioides difficile/immunologie , Infections à Clostridium/thérapie , Modèles animaux de maladie humaine , Entérotoxines/immunologie , Femelle , Antigènes d'histocompatibilité de classe I , Immunisation passive , Immunoglobuline G/immunologie , Immunoglobuline G/métabolisme , Immunoglobuline G/usage thérapeutique , Mâle , Mesocricetus , Souris de lignée C57BL , Souris knockout , Techniques de culture d'organes , Récepteur Fc/déficitRÉSUMÉ
Mellamide, a novel indole amide, was isolated from a fermentation of Aspergillus melleus using silica gel and high-performance liquid chromatographic methods. This allowed its separation from three known antiparasitic compounds (ochratoxin A, viomellin and xanthomegnin) also present in the potent extract. The structure was elucidated by (1)H, (13)C, COSY, DEPT, HMQC and HMBC NMR experiments. HR-FTMS aided in the molecular weight and formula determination. Mellamide showed in vitro insecticidal activity in bioassays against larvae of Lucilia sericata and Aedes egypti with LD(90) of 1,000 and 50 micro g/ml, respectively.
Sujet(s)
Amides/isolement et purification , Aspergillus/composition chimique , Indoles/isolement et purification , Insecticides/isolement et purification , Amides/composition chimique , Animaux , Dosage biologique , Culicidae/effets des médicaments et des substances chimiques , Culicidae/croissance et développement , Diptera/effets des médicaments et des substances chimiques , Diptera/croissance et développement , Indoles/composition chimique , Microbiologie industrielle , Insecticides/composition chimique , Larve/effets des médicaments et des substances chimiquesRÉSUMÉ
During the course of our screening for natural products from fungi, extracts of several cultures were found to make a family of related resorcylic acid lactone compounds, which are potent inhibitors of MEK kinase. Comparative and empirical studies of fermentation conditions improved the titers of the compounds of interest. Striking changes in the ratios and amounts of the major and minor compounds in some cases were achieved by manipulations of media composition.
Sujet(s)
Antienzymes/métabolisme , Fermentation , Champignons/métabolisme , Lactones/métabolisme , Protein-Serine-Threonine Kinases/antagonistes et inhibiteurs , Milieux de cultureRÉSUMÉ
Farnesyl-protein transferase (FPTase) is a critical enzyme that participates in the post-translational modification of the Ras protein. Inhibitors of this enzyme have the potential of being novel anticancer agents for tumors in which the ras oncogene is found mutated and contributes to cell transformation. Continued screening of natural product extracts led to the isolation of kampanols, which are novel and specific inhibitors of FPTase. The most active kampanols exhibited IC50 values between 7 to 13 microM against human recombinant FPTase. The isolation, structure determination, and biological activity of these compounds are described.
Sujet(s)
Alkyl et aryl transferases/antagonistes et inhibiteurs , Antinéoplasiques/composition chimique , Antienzymes/composition chimique , Terpènes/composition chimique , Antinéoplasiques/isolement et purification , Antinéoplasiques/pharmacologie , Antienzymes/isolement et purification , Antienzymes/pharmacologie , Gènes ras , Humains , Spectroscopie par résonance magnétique , Modèles moléculaires , Conformation moléculaire , Structure moléculaire , Protéines recombinantes/antagonistes et inhibiteurs , Terpènes/isolement et purification , Terpènes/pharmacologieRÉSUMÉ
A novel fungal metabolite, apicidin [cyclo(N-O-methyl-L-tryptophanyl-L -isoleucinyl-D-pipecolinyl-L-2-amino-8-oxodecanoyl)], that exhibits potent, broad spectrum antiprotozoal activity in vitro against Apicomplexan parasites has been identified. It is also orally and parenterally active in vivo against Plasmodium berghei malaria in mice. Many Apicomplexan parasites cause serious, life-threatening human and animal diseases, such as malaria, cryptosporidiosis, toxoplasmosis, and coccidiosis, and new therapeutic agents are urgently needed. Apicidin's antiparasitic activity appears to be due to low nanomolar inhibition of Apicomplexan histone deacetylase (HDA), which induces hyperacetylation of histones in treated parasites. The acetylation-deacetylation of histones is a thought to play a central role in transcriptional control in eukaryotic cells. Other known HDA inhibitors were also evaluated and found to possess antiparasitic activity, suggesting that HDA is an attractive target for the development of novel antiparasitic agents.
Sujet(s)
Antiprotozoaires/pharmacologie , Antienzymes/pharmacologie , Eucaryotes/effets des médicaments et des substances chimiques , Inhibiteurs de désacétylase d'histone , Paludisme/traitement médicamenteux , Peptides cycliques/pharmacologie , Plasmodium berghei , Animaux , Eimeria tenella/effets des médicaments et des substances chimiques , Femelle , Humains , Cinétique , Souris , Souris de lignée BALB C , Neospora/effets des médicaments et des substances chimiques , Peptides cycliques/usage thérapeutique , Plasmodium falciparum/effets des médicaments et des substances chimiques , Liaison aux protéines , Protozooses/traitement médicamenteux , Relation structure-activité , Toxoplasma/effets des médicaments et des substances chimiquesRÉSUMÉ
Two new zaragozic acids, D and D2, have been isolated from the keratinophilic fungus Amauroascus niger. Zaragozic acids D [4] and D2 [5] are related to the previously described zaragozic acids A [1], B [2], and C [3] and are potent inhibitors of squalene synthase. Furthermore, all the zaragozic acids (A, B, C, D, and D2) are also active against farnesyl transferase. Zaragozic acids D and D2 inhibit farnesyl transferase with IC50 values of 100 nM, while zaragozic acids A and B are less potent.
Sujet(s)
Alkyl et aryl transferases , Ascomycota/métabolisme , Composés hétérocycliques bicycliques , Composés bicycliques pontés/pharmacologie , Farnesyl-diphosphate farnesyltransferase/antagonistes et inhibiteurs , Transferases/antagonistes et inhibiteurs , Triacides carboxyliques/pharmacologie , Composés bicycliques pontés/isolement et purification , Fermentation , Spectroscopie par résonance magnétique , Triacides carboxyliques/isolement et purificationRÉSUMÉ
In screening for antifungal inhibitors from fungi, four related antifungal agents have been isolated from the cultivation of Aspergillus fumigatus ATCC 20857. These agents were initially produced by the microorganism growing on a solid millet-based medium. A liquid medium containing both glucose and glycerol has also been developed in which these antibiotics are produced in two phases. These novel compounds, sphingofungins A, B, C, and D, show a limited spectrum of antifungal activity but were especially effective against Cryptococcus species.