Structural Studies of West Nile Virus in Complex with Neutralizing Antibodies.

West Nile virus (WNV) is a positive strand RNA virus in the family Flaviviridae, which includes members such as dengue, Japanese encephalitis, tick-borne encephalitis, yellow fever and Hepatitis C. As with other members of the genus, it is arthropod transmitted and has recently established itself as an endemic virus in the United States. Although most infections are asymptomatic, clinical manifestations of WNV include encephalitis and death. We have been interested in investigating the nature of the immune response with particular emphasis on the role of antibodies in reducing the level of infection. We have used a combination of techniques, but primarily structure, as a tool to probe the nature of antibody-mediated virus neutralization. Our results suggest that neutralization of virus particles is more complex than originally envisioned, with multiple mechanisms utilized. Using a combination of X-ray crystallography and cryo-electron microscopy, several virus-antibody complexes have been determined at pseudo-atomic resolution. These studies suggest the following: 1) flavivirus particles exhibit dynamic motions or breathing that transiently expose cryptic epitopes; 2) although there are 180 potential binding sites for each monoclonal antibody the quasi-equivalent nature of the virion usually permits only a subset of sites to be utilized; 3) the availability of these sites, the epitope itself, and the avidity of antibody directly influence the mechanism of neutralization; and 4) particles thought to be incapable of infecting cells, so-called immature viruses, may play a critical role in immune surveillance and reactivity. The structure of the flavivirus virion and complexes of monoclonal antibodies will be presented along with data to support mechanisms antibody-mediated flavivirus neutralizatio

Capturing a Flavivirus Pre-Fusion Intermediate

During cell entry of flaviviruses, low endosomal pH triggers the rearrangement of the viral surface glycoproteins to a fusion-active state that allows the release of the infectious RNA into the cytoplasm. In this work, West Nile virus was complexed with Fab fragments of the neutralizing mAb E16 and was subsequently exposed to low pH, trapping the virions in a pre-fusion intermediate state. The structure of the complex was studied by cryo-electron microscopy and provides the first structural glimpse of a flavivirus fusion intermediate near physiological conditions. A radial expansion of the outer protein layer of the virion was observed compared to the structure at pH 8. The resulting ∼60 Å-wide shell of low density between lipid bilayer and outer protein layer is likely traversed by the stem region of the E glycoprotein. By using antibody fragments, we have captured a structural intermediate of a virus that likely occurs during cell entry. The trapping of structural transition states by antibody fragments will be applicable for other processes in the flavivirus life cycle and delineating other cellular events that involve conformational rearrangements

Mapping of mitochondrial mRNA termini in Arabidopsis thaliana: t-elements contribute to 5′ and 3′ end formation

With CR–RT–PCR as primary approach we mapped the 5′ and 3′ transcript ends of all mitochondrial protein-coding genes in Arabidopsis thaliana. Almost all transcripts analyzed have single major 3′ termini, while multiple 5′ ends were found for several genes. Some of the identified 5′ ends map within promoter motifs suggesting these ends to be derived from transcription initiation while the majority of the 5' termini seems to be generated post-transcriptionally. Assignment of the extremities of 5′ leader RNAs revealed clear evidence for an endonucleolytic generation of the major cox1 and atp9 5′ mRNA ends. tRNA-like structures, so-called t-elements, are associated either with 5′ or with 3′ termini of several mRNAs. These secondary structures most likely act as cis-signals for endonucleolytic cleavages by RNase Z and/or RNase P. Since no conserved sequence motif is evident at post-transcriptionally derived ends, we suggest t-elements, stem–loops and probably complex higher order structures as cis-elements for processing. This analysis provides novel insights into 5′ and 3′ end formation of mRNAs. In addition, the complete transcript map is a substantial and important basis for future studies of gene expression in mitochondria of higher plants

Multicultural Interdisciplinary Handbook: tools for learning history and geography in a multicultural perspective (MIH)

[ES] MIH project (Multicultural Interdisciplinary Handbook: tools for learning History and Geography in a multicultural perspective) is a Comenius Multilateral Project funded with support from the European Commission that has been developed from 2009 to 2011.Conceived from the idea of educating lower and upper Secondary School pupils in a process of construction of a European identity by involving them in the culture of other countries, MIH project meets this need by providing new methodological and ICT tools that could help teachers and pupils to plunge deeper into both cultures and languages of another nations via their History and Geography, and opens the way to introduce a European perspective in History and Geography school curricula and classroom activities

Salmonella enterica Serovar Typhimurium Exploits Inflammation to Compete with the Intestinal Microbiota

Most mucosal surfaces of the mammalian body are colonized by microbial communities (“microbiota”). A high density of commensal microbiota inhabits the intestine and shields from infection (“colonization resistance”). The virulence strategies allowing enteropathogenic bacteria to successfully compete with the microbiota and overcome colonization resistance are poorly understood. Here, we investigated manipulation of the intestinal microbiota by the enteropathogenic bacterium Salmonella enterica subspecies 1 serovar Typhimurium (S. Tm) in a mouse colitis model: we found that inflammatory host responses induced by S. Tm changed microbiota composition and suppressed its growth. In contrast to wild-type S. Tm, an avirulent invGsseD mutant failing to trigger colitis was outcompeted by the microbiota. This competitive defect was reverted if inflammation was provided concomitantly by mixed infection with wild-type S. Tm or in mice (IL10−/−, VILLIN-HACL4-CD8) with inflammatory bowel disease. Thus, inflammation is necessary and sufficient for overcoming colonization resistance. This reveals a new concept in infectious disease: in contrast to current thinking, inflammation is not always detrimental for the pathogen. Triggering the host's immune defence can shift the balance between the protective microbiota and the pathogen in favour of the pathogen

"Oppositionswissenschaft" mit Privileg. Kulturgeschichte und Geschichtsdidaktik im Kaiserreich

Deile L. "Oppositionswissenschaft" mit Privileg. Kulturgeschichte und Geschichtsdidaktik im Kaiserreich. In: Kuhn B, Popp S, eds. Kulturgeschichtliche Traditionen der Geschichtsdidaktik. Historica et didactica : Forschung Geschichtsdidaktik. Vol 1. St. Ingbert: Röhrig Univ.-Verl.; 2011: 71-99