Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Molecular and chemical dialogues in bacteria-protozoa interactions
Song, C. ; Mazzola, M. ; Cheng, X. ; Oetjen, J. ; Alexandrov, T. ; Dorrestein, P. ; Watrous, J. ; Voort, M. van der; Raaijmakers, J.M. - \ 2015
Scientific Reports 5 (2015). - ISSN 2045-2322 - 13 p.
imaging mass-spectrometry - pseudomonas-fluorescens cha0 - dictyostelium-discoideum - caenorhabditis-elegans - spatial segmentation - tetr family - aeruginosa - biosynthesis - rhizosphere - strain
Protozoan predation of bacteria can significantly affect soil microbial community composition and ecosystem functioning. Bacteria possess diverse defense strategies to resist or evade protozoan predation. For soil-dwelling Pseudomonas species, several secondary metabolites were proposed to provide protection against different protozoan genera. By combining whole-genome transcriptome analyses with (live) imaging mass spectrometry (IMS), we observed multiple changes in the molecular and chemical dialogues between Pseudomonas fluorescens and the protist Naegleria americana. Lipopeptide (LP) biosynthesis was induced in Pseudomonas upon protozoan grazing and LP accumulation transitioned from homogeneous distributions across bacterial colonies to site-specific accumulation at the bacteria-protist interface. Also putrescine biosynthesis was upregulated in P. fluorescens upon predation. We demonstrated that putrescine induces protozoan trophozoite encystment and adversely affects cyst viability. This multifaceted study provides new insights in common and strain-specific responses in bacteria-protozoa interactions, including responses that contribute to bacterial survival in highly competitive soil and rhizosphere environments.
Development of a Multiplexed Bead-Based Suspension Array for the Detection and Discrimination of Pospiviroid Plant Pathogens
Brunschot, S.L. van; Bergervoet, J.H.W. ; Pagendam, D.E. ; Weerdt, M. de; Geering, A.D.W. ; Drenth, A. ; Vlugt, R.A.A. van der - \ 2014
PLoS ONE 9 (2014)1. - ISSN 1932-6203
rt-pcr assay - 1st report - greenhouse tomatoes - natural infection - viroid disease - potato - identification - transmission - technology - strain
Efficient and reliable diagnostic tools for the routine indexing and certification of clean propagating material are essential for the management of pospiviroid diseases in horticultural crops. This study describes the development of a true multiplexed diagnostic method for the detection and identification of all nine currently recognized pospiviroid species in one assay using Luminex bead-based suspension array technology. In addition, a new data-driven, statistical method is presented for establishing thresholds for positivity for individual assays within multiplexed arrays. When applied to the multiplexed array data generated in this study, the new method was shown to have better control of false positives and false negative results than two other commonly used approaches for setting thresholds. The 11-plex Luminex MagPlex-TAG pospiviroid array described here has a unique hierarchical assay design, incorporating a near-universal assay in addition to nine species-specific assays, and a co-amplified plant internal control assay for quality assurance purposes. All assays of the multiplexed array were shown to be 100% specific, sensitive and reproducible. The multiplexed array described herein is robust, easy to use, displays unambiguous results and has strong potential for use in routine pospiviroid indexing to improve disease management strategies.
Polycistronic expression of a ß-carotene biosynthetic pathway in Saccharomyces cerevisiae coupled to ß-ionone production
Beekwilder, J. ; Rossum, H.M. ; Koopman, F. ; Sonntag, F. ; Buchhaupt, M. ; Schrader, J. ; Hall, R.D. ; Bosch, H.J. ; Pronk, J.T. ; Maris, A.J.A. van; Daran, J.M. - \ 2014
Journal of Biotechnology 192 (2014)partB. - ISSN 0168-1656 - p. 383 - 392.
cleavage dioxygenase - yeast - genes - sequences - transformation - translation - polyprotein - versatile - genome - strain
The flavour and fragrance compound ß-ionone, which naturally occurs in raspberry and many other fruits and flowers, is currently produced by synthetic chemistry. This study describes a synthetic biology approach for ß-ionone production from glucose by Saccharomyces cerevisiae that is partially based on polycistronic expression. Experiments with model proteins showed that the T2A sequence of the Thosea asigna virus mediated efficient production of individual proteins from a single transcript in S. cerevisiae. Subsequently, three ß-carotene biosynthesis genes from the carotenoid-producing ascomycete Xanthophyllomyces dendrorhous (crtI, crtE and crtYB) were expressed in S. cerevisiae from a single polycistronic construct. In this construct, the individual crt proteins were separated by T2A sequences. Production of the individual proteins from the polycistronic construct was confirmed by Western blot analysis and by measuring the production of ß-carotene. To enable ß-ionone production, a carotenoid-cleavage dioxygenase from raspberry (RiCCD1) was co-expressed in the ß-carotene producing strain. In glucose-grown cultures with a second phase of dodecane, ß-ionone and geranylacetone accumulated in the organic phase. Thus, by introducing a polycistronic construct encoding a fungal carotenoid pathway and an expression cassette encoding a plant dioxygenase, a novel microbial production system has been established for a fruit flavour compound.
Wolbachia infection does not alter attraction of the mosquito Aedes (Stegomyia) aegypti to human odours
Turley, A.P. ; Smallegange, R.C. ; Takken, W. ; Zalucki, M.P. ; O'Neill, S.L. ; McGraw, E.A. - \ 2014
Medical and Veterinary Entomology 28 (2014)4. - ISSN 0269-283X - p. 457 - 460.
life-shortening wolbachia - diptera-culicidae - dengue - populations - strain
The insect endosymbiont Wolbachia pipientis (Rickettsiales: Rickettsiaceae) is undergoing field trials around the world to determine if it can reduce transmission of dengue virus from the mosquito Stegomyia aegypti to humans. Two different Wolbachia strains have been released to date. The primary effect of the wMel strain is pathogen protection whereby infection with the symbiont limits replication of dengue virus inside the mosquito. A second strain, wMelPop, induces pathogen protection, reduces the adult mosquito lifespan and decreases blood feeding success in mosquitoes after 15 days of age. Here we test whether Wolbachia infection affects mosquito attraction to host odours in adults aged 5 and 15 days. We found no evidence of reduced odour attraction of mosquitoes, even for those infected with the more virulent wMelPop. This bodes well for fitness and competitiveness in the field given that the mosquitoes must find hosts to reproduce for the biocontrol method to succeed.
Association between transmission rate and disease severity for Actinobacillus pleuropneumoniae infection in pigs
Tobias, T.J. ; Bouma, A. ; Daemen, A.J.J.M. ; Wagenaar, J.A. ; Stegeman, A. ; Klinkenberg, D. - \ 2013
Veterinary Research 44 (2013). - ISSN 0928-4249
serotype 9 - herd - parahaemolyticus - epidemiology - influenza - virulence - bacteria - design - strain
A better understanding of the variation in infectivity and its relation with clinical signs may help to improve measures to control and prevent (clinical) outbreaks of diseases. Here we investigated the role of disease severity on infectivity and transmission of Actinobacillus pleuropneumoniae, a bacterium causing respiratory problems in pig farms. We carried out transmission experiments with 10 pairs of caesarean-derived, colostrum-deprived pigs. In each pair, one pig was inoculated intranasally with 5 x 10(6) CFUs of A. pleuropneumoniae strain 1536 and housed together with a contact pig. Clinical signs were scored and the course of infection was observed by bacterial examination and qPCR analysis of tonsillar brush and nasal swab samples. In 6 out of 10 pairs transmission to contact pigs was observed, but disease scores in contact infected pigs were low compared to the score in inoculated pigs. Whereas disease score was positively associated with bacterial load in inoculated pigs and bacterial load with the transmission rate, the disease score had a negative association with transmission. These findings indicate that in pigs with equal bacterial load, those with higher clinical scores transmit A. pleuropneumoniae less efficiently. Finally, the correlation between disease score in inoculated pigs and in positive contact pigs was low. Although translation of experimental work towards farm level has limitations, our results suggest that clinical outbreaks of A. pleuropneumoniae are unlikely to be caused only by spread of the pathogen by clinically diseased pigs, but may rather be the result of development of clinical signs in already infected pigs.
Brevibacterium siliguriense sp nov., a facultatively oligotrophic bacterium isolated from river water
Kumar, A. ; Ince, I.A. ; Kati, A. ; Chakraborty, R. - \ 2013
International Journal of Systematic and Evolutionary Microbiology 63 (2013)Pt 2. - ISSN 1466-5026 - p. 511 - 515.
thin-layer-chromatography - rapid method - genus - corynebacteria - identification - alignment - strain - acid
A Gram-positive-staining, rod-shaped, facultatively oligotrophic bacterial strain, designated MB18(T), was isolated from a water sample collected from the River Mahananda at Siliguri (26 degrees 44' 23.20' N, 88 degrees 25' 22.89' a West-Bengal, India. On the basis of 16S rRNA gene sequence similarity, the closest relative of this strain was Brevibacterium epidermidis NCDO 2286(T) (96% similarity). The DNA G+C content of strain MB18(T) was 64.6 molo/o. Chemotaxonomic data [MK-8(H-2) as the major menaquinone, galactose as the sole cell-wall sugar, meso-diaminopimelic acid as the diagnostic cell-wall diamino acid, phosphatidylglycerol and diphosphatidylglycerol as constituents of the polar lipids, anteiso-C-15:0, anteiso-C-17:0 and iso-C-15:0 as the major fatty acids] supported the affiliation of strain MB18T to the genus Brevibacterium. The results of DNA G +C content, 16S rRNA gene sequence analysis and biochemical and physiological analyses allowed genotypic and phenotypic differentiation of strain MB18(T) from its nearest neighbour B. epidermidis. The isolate therefore represents a novel species, for which the name Brevibacterium siliguriense sp. nov. is proposed; the type strain is MB18(T) (=DSM 23676(T)=LMG 25772(T)).
Increased pathogenicity of European porcine reproductive and respiratory syndrome virus is associated with enhanced adaptive responses and viral clearance
Morgan, S.B. ; Graham, S.P. ; Salguero, F.J. ; Sánchez Cordón, P.J. ; Mokhtar, H. ; Rebel, J.M.J. ; Weesendorp, E. ; Bodman-Smith, K.B. ; Steinbach, F. ; Frossard, J.P. - \ 2013
Veterinary Microbiology 163 (2013). - ISSN 0378-1135 - p. 13 - 22.
classical swine-fever - infection - prrsv - definition - diversity - subtypes - vr-2332 - isolate - strain - model
Porcine reproductive and respiratory syndrome (PRRS) is one of the most economically important diseases of swine worldwide. Since its first emergence in 1987 the PRRS virus (PRRSV) has become particularly divergent with highly pathogenic strains appearing in both Europe and Asia. However, the underlying mechanisms of PRRSV pathogenesis are still unclear. This study sets out to determine the differences in pathogenesis between subtype 1 and 3 strains of European PRRSV (PRRSV-I), and compare the immune responses mounted against these strains. Piglets were infected with 3 strains of PRRSV-I: Lelystad virus, 215-06 a British field strain and SU1-bel from Belarus. Post-mortem examinations were performed at 3 and 7 days post-infection (dpi), and half of the remaining animals in each group were inoculated with an Aujeszky's disease (ADV) vaccine to investigate possible immune suppression resulting from PRRSV infection. The subtype 3 SU1-bel strain displayed greater clinical signs and lung gross pathology scores compared with the subtype 1 strains. This difference did not appear to be caused by higher virus replication, as viraemia and viral load in broncho-alveolar lavage fluid (BALF) were lower in the SU1-bel group. Infection with SU1-bel induced an enhanced adaptive immune response with greater interferon (IFN)-¿ responses and an earlier PRRSV-specific antibody response. Infection with PRRSV did not affect the response to vaccination against ADV. Our results indicate that the increased clinical and pathological effect of the SU1-bel strain is more likely to be caused by an enhanced inflammatory immune response rather than higher levels of virus replication.
Bluetongue virus serotype 6 in Europe in 2008 - Emergence and disappearance of an unexpected non-virulent BTV
Rijn, P.A. van; Geurts, Y. ; Spek, A.N. van der; Veldman, D. ; Gennip, H.G.P. van - \ 2012
Veterinary Microbiology 158 (2012)1-2. - ISSN 0378-1135 - p. 23 - 32.
proteins - strain - goats - time
Bluetongue viruses (BTVs) could invade N-W Europe similar to BTV serotype 8 (BTV8/net06), since the source and route of introduction of this virus has not been solved. Therefore, the Dutch survey for Bluetongue by PCR testing was extended by further analysis of PCR positives to identify the involved BTV. In late August 2008, BTV was reported with 12 nucleotide differences in the S10 amplicon (S10 genotyping). This virus was identified as serotype 6, here named BTV6/net08. Promptly, serotype specific real-time PCR tests were developed for serotypes 1, 6, and 8 (S2 genotyping). Agreement was found between results by S10- and S2 genotyping. Further, BTV1 was identified by both S10- and S2 genotyping in one imported animal. After initial discovery of BTV6 in the Netherlands, animals from 18 holdings tested PCR positive for BTV6/net08 in 2008. Remarkably only one or two PCR positive animals per holding were found. Serum neutralization tests did not result in the discovery of more BTV6 infected animals. Retrospective studies indicated no evidence for infections by BTV6/net08 prior to the first discovery. Experimental infections with BTV6/net08 did not cause clinical disease in sheep, calves and cattle, except for a very short fever in some animals. This clearly showed that the vaccine-related BTV6/net08 is not virulent. BTV6/net08 was not found by passive and active surveys in the years after its discovery. Apparently, BTV6/net08 was not efficiently transmitted by endemic species of Culicoides in N-W Europe, and disappeared without the need of any control measure.
EU-Approved Rapid Tests for Bovine Spongform Encephalopathy Detect Atypical Forms: A Study for Their Sensitivities
Meloni, D. ; Davidse, A. ; Langeveld, J.P.M. ; varello, K. ; Casalone, C. ; Corona, C. ; Balkema-Buschmann, A. ; Groschup, M. ; Ingravalle, F. ; Bozzetta, E. - \ 2012
PLoS ONE 7 (2012)9. - ISSN 1932-6203 - 12 p.
creutzfeldt-jakob-disease - bse-affected cattle - prion protein - scrapie - transmission - switzerland - primate - strain - prp
Since 2004 it become clear that atypical bovine spongiform encephalopthies (BSEs) exist in cattle. Whenever their detection has relied on active surveillance plans implemented in Europe since 2001 by rapid tests, the overall and inter-laboratory performance of these diagnostic systems in the detection of the atypical strains has not been studied thoroughly to date. To fill this gap, the present study reports on the analytical sensitivity of the EU-approved rapid tests for atypical L-and H-type and classical BSE in parallel. Each test was challenged with two dilution series, one created from a positive pool of the three BSE forms according to the EURL standard method of homogenate preparation (50% w/v) and the other as per the test kit manufacturer's instructions. Multilevel logistic models and simple logistic models with the rapid test as the only covariate were fitted for each BSE form analyzed as directed by the test manufacturer's dilution protocol. The same schemes, but excluding the BSE type, were then applied to compare test performance under the manufacturer's versus the water protocol. The IDEXX HerdChek (R) BSE-scrapie short protocol test showed the highest sensitivity for all BSE forms. The IDEXX (R) HerdChek BSE-scrapie ultra short protocol, the Prionics (R) - Check WESTERN and the AJ Roboscreen (R) BetaPrion tests showed similar sensitivities, followed by the Roche (R) PrionScreen, the Bio-Rad (R) TeSeE (TM) SAP and the Prionics (R) - Check PrioSTRIP in descending order of analytical sensitivity. Despite these differences, the limit of detection of all seven rapid tests against the different classes of material set within a 2 log(10) range of the best-performing test, thus meeting the European Food Safety Authority requirement for BSE surveillance purposes. These findings indicate that not many atypical cases would have been missed surveillance since 2001 which is important for further epidemiological interpretations of the sporadic character of atypical forms.
Characterization of bacterial isolates from rotting potato tuber tissue showing antagonism to Dickeya sp. biovar 3 in vitro and in planta
Czajkowski, R.L. ; Boer, W.J. de; Veen, J.A. van; Wolf, J.M. van der - \ 2012
Plant Pathology 61 (2012)1. - ISSN 0032-0862 - p. 169 - 182.
acyl-homoserine-lactone - biological-control - soft-rot - erwinia-carotovora - colonization - rhizosphere - strain - soilborne - blackleg - growth
Possibilities for biocontrol of biovar 3 Dickeya sp. in potato were investigated, using bacteria from rotting potato tissue isolated by dilution plating on nonselective agar media. In a plate assay, 649 isolates were screened for antibiosis against Dickeya sp. IPO2222 and for the production of siderophores. Forty-one isolates (6Æ4%) produced antibiotics and 112 isolates (17Æ3%) produced siderophores. A selection of 41 antibiotic-producing isolates and 41 siderophore-producing isolates were tested in a potato slice assay for control of the Dickeya sp. Isolates able to reduce rotting of potato tuber tissue by at least 50% of the control were selected. Isolates were characterized by 16S rDNA analysis as Bacillus, Pseudomonas, Rhodococcus, Serratia, Obesumbacterium and Lysinibacillus genera. Twenty-three isolates belonging to different species and genera, 13 producing antibiotics and 10 producing siderophores, were further characterized by testing acyl-homoserine lactone (AHL) production, quorum quenching, motility, biosurfactant production, growth at low (4Æ0) and high (10Æ0) pH, growth at 10_C under aerobic and anaerobic conditions and auxin production. In replicated greenhouse experiments, four selected antagonists based on the in vitro tests were tested in planta using wounded or intact minitubers of cv. Kondor subsequently inoculated by vacuum infiltration with an antagonist and a GFP (green fluorescent protein)-tagged biovar 3 Dickeya sp. strain. A potato endophyte A30, characterized as S. plymuthica, protected potato plants by reducing blackleg development by 100% and colonization of stems by Dickeya sp. by 97%. The potential use of S. plymuthica A30 for the biocontrol of Dickeya sp. is discussed
Maternal immunity against avian influenza H5N1 in chickens: limited protection and interference with vaccine efficacy
Maas, H.A. ; Rosema, S. ; Zoelen-Bos, D.J. van; Kemper-Venema, S. - \ 2011
Avian Pathology 40 (2011)1. - ISSN 0307-9457 - p. 87 - 92.
inactivated vaccines - virus-infection - antibody - susceptibility - transmission - excretion - strain - ducks - cats - h7n7
After avian influenza (AI) vaccination, hens will produce progeny chickens with maternally derived AI-specific antibodies. In the present study we examined the effect of maternal immunity in young chickens on the protection against highly pathogenic AI H5N1 virus infection and on the effectiveness of AI vaccination. The mean haemagglutination inhibition antibody titre in sera of 14-day-old progeny chickens was approximately eight-fold lower than the mean titre in sera of vaccinated hens. After H5N1 infection at the age of 14 days, chickens with maternal antibody titres lived a few days longer than control chickens. However, only a low proportion of chickens with maternal immunity survived challenge with H5N1. In most progeny chickens with maternal immunity, high virus titres (104 median embryo infective dose) were present in the trachea during the first 4 days after H5N1 infection. In the cloaca, only low virus titres were present in most chickens. In 14-day-old progeny chickens with maternal immunity, the induction of antibody titres by vaccination was severely inhibited, with only a few chickens showing responses similar to the control chickens. It is concluded that high maternal antibody titres are required for clinical protection and reduction of virus titres after infection of chickens, whereas low antibody titres already interfere with vaccine efficacy.
Financial problems and psychological distress: Investigating reciprocal effects among business owners
Gorgievski, M.J. ; Bakker, A.B. ; Schaufeli, W.B. ; Veen, H.B. van der; Giesen, C.W.M. - \ 2010
Journal of Occupational and Organizational Psychology 83 (2010)2. - ISSN 0963-1798 - p. 513 - 530.
dynamic equilibrium-model - negative affectivity - job characteristics - farm operators - stress process - self - performance - depression - health - strain
Building on conservation of resources theory and the dynamic equilibrium model, this three-wave longitudinal study among 260 Dutch agricultural business owners (1-year time intervals) investigated reciprocal relationships between the financial situation of the business and psychological distress. Results of structural equation modelling analyses revealed a negative spiral of farm decline, in which psychological variables played a key role. Experiencing financial problems predicted psychological distress, and acted as a self-fulfilling prophecy by strengthening intentions to quit the business, which predicted a deterioration of the objective financial situation of the business 1 year later. Moreover, farmers experiencing more psychological distress were more likely to get caught in this negative spiral than business owners with better mental health, because they experienced more financial problems, irrespective of their objective financial situation. Long-term psychological distress rather than temporary fluctuations in distress levels accounted for this effect.
How widespread is resistance to invermectin among gastrointestinal nematodes in sheep in The Netherlands? = Hoe wijd verspreid is resistentie tegen ivermectine van maagdarmwormen bij het schaap in Nederland?
Borgsteede, F.H.M. ; Verkaik, J.C. ; Moll, L. ; Dercksen, D. ; Vellema, P. ; Bavinck, G. - \ 2010
Tijdschrift voor Diergeneeskunde 135 (2010)21. - ISSN 0040-7453 - p. 782 - 785.
ivermectine - schapen - maagdarmziekten - wormen - schapenhouderij - haemonchus contortus - ivermectin - sheep - gastrointestinal diseases - helminths - sheep farming - anthelmintic resistance - teladorsagia-circumcincta - haemonchus-contortus - moxidectin - ostertagia - efficacy - benzimidazole - association - strain
In Autumn 2009, a faecal egg count reduction test (FERCT) was carried out on three sheep farms. Groups of 8-11 lambs were treated with ivermectin or moxidectin, with a 14-day interval between treatment and sampling. Ivermectin resistance was present on all three farms. Treatment with ivermectin resulted in a reduction in faecal egg numbers of 94.6%, 63%, and 59%. On two farms, 14 days after treatment pooled faecal samples yielded predominantly larvae of Hamonchus contortus (100% and 98%, respectively). On the third farm, H. contortus and (probably) Teladorsagia circumcincta were resistant to ivermectin (64% and 36% of the larvae, respectively). Treatment with moxidectin resulted in a 100% reduction in egg output in sheep on all three farms. More sensitive culture techniques failed to detect any larvae in samples taken from two farms, but a few Ostertagia-type larvae, probably of T. circumcincta, were detected in samples from the third farm. It can be concluded that gastrointestinal nematodes in sheep from these three farms were resistant to ivermectin, whereas resistance to moxidectin was not detected.
Effects of inbreeding and genetic modification on Aedes aegypti larval competition and adult energy reserves
Koenraadt, C.J.M. ; Kormaksson, M. ; Harrington, L.C. - \ 2010
Parasites & Vectors 3 (2010). - ISSN 1756-3305 - 11 p.
yellow-fever mosquito - environment interactions - transgenic mosquitos - rapid-determination - borne diseases - fitness - diptera - culicidae - strain - interference
Background - Genetic modification of mosquitoes offers a promising strategy for the prevention and control of mosquito-borne diseases. For such a strategy to be effective, it is critically important that engineered strains are competitive enough to serve their intended function in population replacement or reduction of wild mosquitoes in nature. Thus far, fitness evaluations of genetically modified strains have not addressed the effects of competition among the aquatic stages and its consequences for adult fitness. We therefore tested the competitive success of combinations of wild, inbred and transgenic (created in the inbred background) immature stages of the dengue vector Aedes aegypti in the presence of optimal and sub-optimal larval diets. Results - The wild strain of Ae. aegypti demonstrated greater performance (based on a composite index of survival, development rate and size) than the inbred strain, which in turn demonstrated greater performance than the genetically modified strain. Moreover, increasing competition through lowering the amount of diet available per larva affected fitness disproportionately: transgenic larvae had a reduced index of performance (95-119%) compared to inbred (50-88%) and wild type larvae (38-54%). In terms of teneral energy reserves (glycogen, lipid and sugar), adult wild type mosquitoes had more reserves directly available for flight, dispersal and basic metabolic functions than transgenic and inbred mosquitoes. Conclusions - Our study provides a detailed assessment of inter- and intra-strain competition across aquatic stages of wild type, inbred, and transgenic mosquitoes and the impact of these conditions on adult energy reserves. Although it is not clear what competitive level is adequate for success of transgenic strains in nature, strong gene drive mechanisms are likely to be necessary in order to overcome competitive disadvantages in the larval stage that carryover to affect adult fitness
PrP Conformational Transitions Alter Species Preference of a PrP-specific antibody
Zou, W.Q. ; Langeveld, J.P.M. ; Xiao, X. ; Chen, S. ; McGeer, P.L. ; Yuan, J. ; Payne, M.C. ; Kang, H.E. ; McGeehan, J.M. ; Sy, M.S. ; Greenspan, N.S. ; Kaplan, D. ; Wang, G.X. ; Parchi, P. ; Hoover, E.A. ; Kneale, G. ; Telling, G. ; Surewicz, W. ; Kong, Q. ; Guo, J. - \ 2010
Journal of Biological Chemistry 285 (2010). - ISSN 0021-9258 - p. 13874 - 13884.
creutzfeldt-jakob-disease - pathological prion protein - monoclonal-antibody - n-terminus - scrapie - epitope - binding - brain - recognition - strain
The epitope of the 3F4 antibody most commonly used in human prion disease diagnosis is believed to consist of residues Met-Lys-His-Met (MKHM) corresponding to human PrP-(109–112). This assumption is based mainly on the observation that 3F4 reacts with human and hamster PrP but not with PrP from mouse, sheep, and cervids, in which Met at residue 112 is replaced by Val. Here we report that, by brain histoblotting, 3F4 did not react with PrP of uninfected transgenic mice expressing elk PrP; however, it did show distinct immunoreactivity in transgenic mice infected with chronic wasting disease. Compared with human PrP, the 3F4 reactivity with the recombinant elk PrP was 2 orders of magnitude weaker, as indicated by both Western blotting and surface plasmon resonance. To investigate the molecular basis of these species- and conformer-dependent preferences of 3F4, the epitope was probed by peptide membrane array and antigen competition experiments. Remarkably, the 3F4 antibody did not react with MKHM but reacted strongly with KTNMK (corresponding to human PrP-(106–110)), a sequence that is also present in cervids, sheep, and cattle. 3F4 also reacted with elk PrP peptides containing KTNMKHV. We concluded that the minimal sequence for the 3F4 epitope consists of residues KTNMK, and the species- and conformer-dependent preferences of 3F4 arise largely from the interactions between Met112 (human PrP) or Val115 (cervid PrP) and adjacent residues.
Selection on feather pecking affects response to novelty and foraging behaviour in laying hens
Haas, E.N. de; Nielsen, B. ; Rodenburg, T.B. ; Buitenhuis, A.J. - \ 2010
Applied Animal Behaviour Science 124 (2010)3-4. - ISSN 0168-1591 - p. 90 - 96.
open-field - domestic chicks - ground-pecking - gallus-gallus - fear - poultry - insights - strain - model - young
Feather pecking (FP) is a major welfare problem in laying hens, influenced by multiple factors. FP is thought to be redirected foraging behaviour, however fearful birds are also known to be more sensitive to develop FP. The relationship between fear-responses, foraging and FP is not well understood, therefore we studied the behaviour of 16 birds from a high feather pecking (HFP) line and 16 birds from a low feather pecking (LFP) line at 35 weeks of age inside a plus-maze. Birds were from the 10th generation of selection for either high or low FP. First exposure to the maze was used to measure birds’ fear-responses to a novel barren environment. Hereafter, birds were trained three times in the maze with four different food-items that were offered in one of the four arms (i.e. regular food-pellets, feathers, grass, and mealworms hidden in wood-shavings). On the fifth day, birds were tested in the maze for 10 min during which they could choose to eat from all available food-items. When exposed for the first time in the maze HFP birds walked a longer distance, vocalized sooner and had more exploratory pecks compared to LFP birds who showed more wing-movements and defecations. When given a choice of food inside the maze both lines preferred eating worms, but HFP birds had more worm-eating bouts and ate faster than LFP birds. The results of this study indicate that HFP birds respond actively to fear-eliciting situations, which may originate from a proactive coping style. Instead of a clear preference for eating feathers, this study supports earlier findings that HFP birds have a stronger pecking motivation than LFP birds
The use of attenuated isolates of Pepino mosaic virus for cross-protection
Schenk, M.F. ; Hamelink, R. ; Vlugt, R.A.A. van der; Vermunt, A.M.W. ; Kaarsemaker, R.C. ; Stijger, C.C.M.M. - \ 2010
European Journal of Plant Pathology 127 (2010)2. - ISSN 0929-1873 - p. 249 - 261.
genomic rna - tomato - sequence - population - resistance - potyvirus - disease - strain - range - spain
Pepino mosaic virus (PepMV) has recently emerged as a highly infectious viral pathogen in tomato crops. Greenhouse trials were conducted under conditions similar to commercial tomato production. These trials examined whether tomato plants can be protected against PepMV by a preceding infection with an attenuated isolate of this virus. Two potential attenuated isolates that displayed mild leaf symptoms were selected from field isolates. Two PepMV isolates that displayed severe leaf symptoms were also selected from field isolates to challenge the attenuated isolates. The isolates with aggressive symptoms were found to reduce bulk yields by 8 and 24% in single infections, respectively. Yield losses were reduced to a 0–3% loss in plants that were treated with either one of the attenuated isolates, while no effects were observed on the quality of the fruits. After the challenge infection, virus accumulation levels and symptom severity of the isolates with aggressive symptoms were also reduced by cross-protection. Infection with the attenuated isolates alone did neither affect bulk yield, nor quality of the harvested tomato fruits.
Dose response effects of avian influenza (H7N7) vaccination of chickens: Serology, clinical protection and reduction of virus excretion
Maas, H.A. ; Tacken, M.G.J. ; Zoelen-Bos, D.J. van; Oei, H.L. - \ 2009
Vaccine 27 (2009)27. - ISSN 0264-410X - p. 3592 - 3597.
inactivated vaccines - efficacy - antibodies - infection - elisa - quantification - susceptibility - nucleoprotein - turkeys - strain
Knowledge of the relation between the antigen content of inactivated avian influenza (Al) vaccines, the serological response after vaccination and protection of vaccinated animals is important for the choice of optimal vaccines and vaccination regimes as well as for the assessment of criteria for the licensing of new Al-vaccines. We studied this relation in a dose response study using inactivated H7N7 avian influenza vaccines with varying antigen content. The serological response depended on the antigen content of the vaccines. Anti-Al antibodies were detected most frequently with ELISA, followed by the virus neutralisation test and the haemagglutination inhibition (HI) assay. Chickens with measurable HI-antibody titers, using homologous H7N7 antigen. were all protected against clinical disease after challenge with highly pathogenic A/chicken/Netherlands/621557/03 H7N7 virus. However, in these chickens high levels of virus could still be present on days 2-4 after challenge. The reduction of virus titers after challenge, depended on the antigen content of the vaccines as well as on the serum antibody titers. While 10 haemagglutinating units (HAU), equivalent to 0.8 mu g haemagglutinin (HA) protein, per vaccine dose was sufficient for prevention of clinical disease, 128 HAU (9 mu g HA) per dose was required for reduction of virus titers in all chickens to 10(3) egg-infectious dose 50% (EID50) or less. In order to reduce virus titers below 10(3) EID50 per swab a HI-antibody titer of 64 was required. After use of the vaccine with the highest antigen content, challenge still induced a booster of antibody titers which is indicative of replication of challenge virus.
Co-existence of scrapie prion protein types 1 and 2 in sporadic Creutzfeldt-Jakob disease: its effect on the phenotype and prion-type characteristics
Cali, I. ; Castellani, R. ; Alshekhlee, A. ; Cohen, Y. ; Blevins, J. ; Yuan, J. ; Langeveld, J.P.M. ; Parchi, P. ; Safar, J.G. ; Zou, W.Q. ; Gambetti, P. - \ 2009
Brain 132 (2009). - ISSN 0006-8950 - p. 2643 - 2658.
monoclonal-antibody - prpsc - strain - cjd - classification - conformations - heterogeneity - determinants - cooccurrence - adaptation
Five phenotypically distinct subtypes have been identified in sporadic Creutzfeldt-Jakob disease (sCJD), based on the methionine/valine polymorphic genotype of codon 129 of the prion protein (PrP) gene and the presence of either one of the two protease K-resistant scrapie prion protein (PrPSc) types identified as 1 and 2. The infrequent co-existence of both PrPSc types in the same case has been known for a long time. Recently, it has been reported, using type-specific antibodies, that the PrPSc type 1 is present in all cases of sCJD carrying PrPSc type 2. The consistent co-occurrence of both PrPSc types complicates the diagnosis and the current classification of sCJD, and has implications for the pathogenesis of naturally occurring prion diseases. In the present study, we investigated the prevalence of PrPSc types 1 and 2 co-occurrence, along with its effects on the disease phenotype and PrPSc strain characteristics, comparatively analysing 34 cases of sCJD, all methionine homozygous at codon 129 of the PrP gene (sCJDMM). To minimize overestimating the prevalence of the sCJDMM cases carrying PrPSc types 1 and 2 (sCJDMM1-2), we used proteinase K concentrations designed to hydrolyse all fragments resulting from an incomplete digestion, while preserving the protease-resistant PrPSc core. Furthermore, we used several antibodies to maximize the detection of both PrPSc types. Our data show that sCJDMM cases associated exclusively with either PrPSc type 1 (sCJDMM1) or PrPSc type 2 (sCJDMM2) do exist; we estimate that they account for approximately 56% and 5% of all the sCJDMM cases, respectively; while in 39% of the cases, both PrPSc types 1 and 2 are present together (sCJDMM1-2) either mixed in the same anatomical region or separate in different regions. Clinically, sCJDMM1-2 had an average disease duration intermediate between the other two sCJDMM subtypes. The histopathology was also intermediate, except for the cerebellum where it resembled that of sCJDMM1. These features, along with the PrP immunostaining pattern, offer a diagnostic clue. We also observed a correlation between the disease duration and the prevalence of PrPSc type 2 and sCJDMM2 phenotypes. The use of different antibodies and of the conformational stability immunoassay indicated that the co-existence of types 1 and 2 in the same anatomical region may confer special conformational characteristics to PrPSc types 1 and 2. All of these findings indicate that sCJDMM1-2 should be considered as a separate entity at this time.
Pepino mosaic virus isolates and differential symptomatology in tomato
Hanssen, I.M. ; Paeleman, A. ; Vandewoestijne, E. ; Bergen, L. Van; Bragard, C. ; Lievens, B. ; Vanachter, A.C.R.C. ; Thomma, B.P.H.J. - \ 2009
Plant Pathology 58 (2009)3. - ISSN 0032-0862 - p. 450 - 460.
genomic rna - genetic-structure - sequence - protein - replication - variability - population - distinct - quality - strain
Based on a survey conducted in commercial tomato production in Belgium in 2006, four Pepino mosaic virus (PepMV) isolates that differed in symptom expression in the crop of origin were selected for greenhouse trials. The selected isolates were inoculated onto tomato plants grown in four separate plastic tunnels. PepMV symptom development was assessed regularly and extensive sampling followed by ELISA analyses, genotyping and sequencing was performed to study viral presence and variation in PepMV sequences throughout the trial period. Two isolates (EU-mild and CH2-mild) that were selected based on mild symptom expression in the crop of origin caused only mild symptoms in the trial, while two other isolates (CH2-aggressive and EU + CH2) that were selected for severe symptom display, caused considerably more severe symptoms. Sequence homology between CH2-mild and CH2-aggressive was as high as 99·4%. Results of this study show that differential symptom expression can, at least partially, be attributed to the PepMV isolate, which may be related to minor differences at the nucleotide level between isolates.
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