oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 59 )

2018 ( 154 )

2017 ( 130 )

2016 ( 164 )

Custom range...

Search Results: 1 - 10 of 94054 matches for " Stefan W. Metz "
All listed articles are free for downloading (OA Articles)
Page 1 /94054
Display every page Item
Effective Chikungunya Virus-like Particle Vaccine Produced in Insect Cells
Stefan W. Metz,Joy Gardner,Corinne Geertsema,Thuy T. Le,Lucas Goh,Just M. Vlak,Andreas Suhrbier,Gorben P. Pijlman
PLOS Neglected Tropical Diseases , 2013, DOI: 10.1371/journal.pntd.0002124
Abstract: The emerging arthritogenic, mosquito-borne chikungunya virus (CHIKV) causes severe disease in humans and represents a serious public health threat in countries where Aedes spp mosquitoes are present. This study describes for the first time the successful production of CHIKV virus-like particles (VLPs) in insect cells using recombinant baculoviruses. This well-established expression system is rapidly scalable to volumes required for epidemic responses and proved well suited for processing of CHIKV glycoproteins and production of enveloped VLPs. Herein we show that a single immunization with 1 μg of non-adjuvanted CHIKV VLPs induced high titer neutralizing antibody responses and provided complete protection against viraemia and joint inflammation upon challenge with the Réunion Island CHIKV strain in an adult wild-type mouse model of CHIKV disease. CHIKV VLPs produced in insect cells using recombinant baculoviruses thus represents as a new, safe, non-replicating and effective vaccine candidate against CHIKV infections.
Low Temperature-Dependent Salmonid Alphavirus Glycoprotein Processing and Recombinant Virus-Like Particle Formation
Stefan W. Metz, Femke Feenstra, Stephane Villoing, Marielle C. van Hulten, Jan W. van Lent, Joseph Koumans, Just M. Vlak, Gorben P. Pijlman
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0025816
Abstract: Pancreas disease (PD) and sleeping disease (SD) are important viral scourges in aquaculture of Atlantic salmon and rainbow trout. The etiological agent of PD and SD is salmonid alphavirus (SAV), an unusual member of the Togaviridae (genus Alphavirus). SAV replicates at lower temperatures in fish. Outbreaks of SAV are associated with large economic losses of ~17 to 50 million $/year. Current control strategies rely on vaccination with inactivated virus formulations that are cumbersome to obtain and have intrinsic safety risks. In this research we were able to obtain non-infectious virus-like particles (VLPs) of SAV via expression of recombinant baculoviruses encoding SAV capsid protein and two major immunodominant viral glycoproteins, E1 and E2 in Spodoptera frugiperda Sf9 insect cells. However, this was only achieved when a temperature shift from 27°C to lower temperatures was applied. At 27°C, precursor E2 (PE2) was misfolded and not processed by host furin into mature E2. Hence, E2 was detected neither on the surface of infected cells nor as VLPs in the culture fluid. However, when temperatures during protein expression were lowered, PE2 was processed into mature E2 in a temperature-dependent manner and VLPs were abundantly produced. So, temperature shift-down during synthesis is a prerequisite for correct SAV glycoprotein processing and recombinant VLP production.
Functional processing and secretion of Chikungunya virus E1 and E2 glycoproteins in insect cells
Stefan W Metz, Corinne Geertsema, Byron E Martina, Paulina Andrade, Jacco G Heldens, Monique M van Oers, Rob W Goldbach, Just M Vlak, Gorben P Pijlman
Virology Journal , 2011, DOI: 10.1186/1743-422x-8-353
Abstract: Expression in the presence of either tunicamycin or furin inhibitor showed that a substantial portion of recombinant intracellular E1 and precursor E3E2 was glycosylated, but that a smaller fraction of E3E2 was processed by furin into mature E3 and E2. Deletion of the C-terminal transmembrane domains of E1 and E2 enabled secretion of furin-cleaved, fully processed E1 and E2 subunits, which could then be efficiently purified from cell culture fluid via metal affinity chromatography. Confocal laser scanning microscopy on living baculovirus-infected Sf21 cells revealed that full-length E1 and E2 translocated to the plasma membrane, suggesting similar posttranslational processing of E1 and E2, as in a natural CHIKV infection. Baculovirus-directed expression of E1 displayed fusogenic activity as concluded from syncytia formation. CHIKV-E2 was able to induce neutralizing antibodies in rabbits.Chikungunya virus glycoproteins could be functionally expressed at high levels in insect cells and are properly glycosylated and cleaved by furin. The ability of purified, secreted CHIKV-E2 to induce neutralizing antibodies in rabbits underscores the potential use of E2 in a subunit vaccine to prevent CHIKV infections.Chikungunya virus (CHIKV) is an arthropod-borne (arbo)virus that causes epidemics in Africa, India and South-East Asia [1]. Recent outbreaks in Italy in 2007 [2] and autochthonous transmission events in France in 2010 [3] exemplify the threat of continued spread of CHIKV in the Western world, which correlates with the concurrent expanding distribution of its insect vector. CHIKV is maintained in a sylvatic transmission cycle of mosquitoes, rodents and primates, with Aedes aegyti as the primary vector. However, the responsible vector causing the severe CHIKV epidemic on the Reunion Islands in 2005/2006 was Ae. albopictus [4]. This vector switch made the virus endemic in more temperate regions and resulted in the first European cases (Italy, 2007) of transmission by local
Longitudinal Single-Spin Asymmetries in Proton-Proton Scattering with a Hadronic Final State
Arnold, S.;Metz, A.;Vogelsang, W.
High Energy Physics - Phenomenology , 2008,
Abstract: We consider longitudinal, parity-violating single-spin asymmetries in proton-proton collisions at RHIC. The focus of this study is on the production of single-inclusive jets, as well as on jets that contain a charm quark. While the asymmetry for inclusive jets turns out to be small, we find considerably larger effects for the case of charm production. We also investigate the role of leading threshold logarithms and find that they increase the polarized and unpolarized cross sections and reduce the spin asymmetry.
Symmetric sequence processing in a recurrent neural network model with a synchronous dynamics
F. L. Metz,W. K. Theumann
Physics , 2009, DOI: 10.1088/1751-8113/42/38/385001
Abstract: The synchronous dynamics and the stationary states of a recurrent attractor neural network model with competing synapses between symmetric sequence processing and Hebbian pattern reconstruction is studied in this work allowing for the presence of a self-interaction for each unit. Phase diagrams of stationary states are obtained exhibiting phases of retrieval, symmetric and period-two cyclic states as well as correlated and frozen-in states, in the absence of noise. The frozen-in states are destabilised by synaptic noise and well separated regions of correlated and cyclic states are obtained. Excitatory or inhibitory self-interactions yield enlarged phases of fixed-point or cyclic behaviour.
Instability of frozen-in states in synchronous Hebbian neural networks
F. L. Metz,W. K. Theumann
Physics , 2008, DOI: 10.1088/1751-8113/41/26/265001
Abstract: The full dynamics of a synchronous recurrent neural network model with Ising binary units and a Hebbian learning rule with a finite self-interaction is studied in order to determine the stability to synaptic and stochastic noise of frozen-in states that appear in the absence of both kinds of noise. Both, the numerical simulation procedure of Eissfeller and Opper and a new alternative procedure that allows to follow the dynamics over larger time scales have been used in this work. It is shown that synaptic noise destabilizes the frozen-in states and yields either retrieval or paramagnetic states for not too large stochastic noise. The indications are that the same results may follow in the absence of synaptic noise, for low stochastic noise.
Pattern reconstruction and sequence processing in feed-forward layered neural networks near saturation
F. L. Metz,W. K. Theumann
Physics , 2005, DOI: 10.1103/PhysRevE.72.021908
Abstract: The dynamics and the stationary states for the competition between pattern reconstruction and asymmetric sequence processing are studied here in an exactly solvable feed-forward layered neural network model of binary units and patterns near saturation. Earlier work by Coolen and Sherrington on a parallel dynamics far from saturation is extended here to account for finite stochastic noise due to a Hebbian and a sequential learning rule. Phase diagrams are obtained with stationary states and quasi-periodic non-stationary solutions. The relevant dependence of these diagrams and of the quasi-periodic solutions on the stochastic noise and on initial inputs for the overlaps is explicitly discussed.
Longitudinal Single-Spin Asymmetries in Proton-Proton Scattering with a Hadronic Final State
S. Arnold,A. Metz,W. Vogelsang
Physics , 2008,
Abstract: We consider longitudinal, parity-violating single-spin asymmetries in proton-proton collisions at RHIC. The focus of this study is on the production of single-inclusive jets, as well as on jets that contain a charm quark. While the asymmetry for inclusive jets turns out to be small, we find considerably larger effects for the case of charm production. We also investigate the role of leading threshold logarithms and find that they increase the polarized and unpolarized cross sections and reduce the spin asymmetry.
Period-two cycles in a feed-forward layered neural network model with symmetric sequence processing
F. L. Metz,W. K. Theumann
Physics , 2007, DOI: 10.1103/PhysRevE.75.041907
Abstract: The effects of dominant sequential interactions are investigated in an exactly solvable feed-forward layered neural network model of binary units and patterns near saturation in which the interaction consists of a Hebbian part and a symmetric sequential term. Phase diagrams of stationary states are obtained and a new phase of cyclic correlated states of period two is found for a weak Hebbian term, independently of the number of condensed patterns $c$.
Feed-forward chains of recurrent attractor neural networks with finite dilution near saturation
F. L. Metz,W. K. Theumann
Physics , 2005, DOI: 10.1016/j.physa.2005.11.049
Abstract: A stationary state replica analysis for a dual neural network model that interpolates between a fully recurrent symmetric attractor network and a strictly feed-forward layered network, studied by Coolen and Viana, is extended in this work to account for finite dilution of the recurrent Hebbian interactions between binary Ising units within each layer. Gradual dilution is found to suppress part of the phase transitions that arise from the competition between recurrent and feed-forward operation modes of the network. Despite that, a long chain of layers still exhibits a relatively good performance under finite dilution for a balanced ratio between inter-layer and intra-layer interactions.
Page 1 /94054
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.