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.

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Francisella tularensis in Swedish predators and scavengers
Hestvik, G. ; Uhlhorn, H. ; Koene, M. ; Åkerström, S. ; Malmsten, A. ; Dahl, F. ; Åhlén, P.A. ; Dalin, A.M. ; Gavier-Widén, D. - \ 2019
Epidemiology and Infection 147 (2019). - ISSN 0950-2688 - p. e293 - e293.
Agglutination - predator - serology - tularaemia - wildlife

Tularaemia is a zoonotic disease, in Europe caused by Francisella tularensis subsp. holarctica. Many lagomorphs and a variety of small rodents are wildlife species prone to develop clinical disease, while predators and scavengers are relatively resistant and may serve as sentinels. Blood samples from 656 Swedish wild predators and scavengers were serologically investigated using slide agglutination and microagglutination. In the slide agglutination test, 34 seropositive animals were detected, and they were found among all species investigated: brown bear (Ursus arctos), Eurasian lynx (Lynx lynx), raccoon dog (Nyctereutes procyonoides), red fox (Vulpes vulpes), wild boar (Sus scrofa), wolf (Canis lupus) and wolverine (Gulo gulo). Due to haemolysis the microagglutination test was more difficult to read at low titres, and only 12 animals were classified as seropositive. F. tularensis subsp. holarctica was detected by a polymerase chain reaction in lymphatic tissues of the head in one brown bear, one red fox and one wolf. The significance of this finding regarding possible latency of infection is not clear. In conclusion, the results of this study indicate that all predator and scavenger species included in this study may serve as sentinels for tularaemia in Sweden. Their role as reservoirs is unclear.

A bead-based suspension array for the detection of Salmonella antibodies in pig sera
Wal, F.J. van der; Achterberg, R.P. ; Maassen, Catharina B.M. - \ 2018
Salmonella - serology - pig - swine - bead-based suspension array - LPS - triazine chemistry
Background Slaughter pigs are monitored for the presence of the zoonotic pathogen Salmonella, using both serology and bacteriology. ELISAs used to investigate pig herds are based on the detection of antibodies against components of the Salmonella cell envelope. Nearly all Salmonella isolates in food-producing animals are serovars of Salmonella enterica subspecies enterica, distributed over various serogroups as determined by the composition of their lipopolysaccharide (LPS). ELISAs for Salmonella serology are usually based on serogroup B and C1 LPS, often combined with serogroup D or E LPS. Although C2 LPS may improve serology, use of C2 LPS in a broad ELISA was never achieved. Results To enable detection of serum antibodies against Salmonella in pigs, a bead-based suspension array was developed with five LPS variants (B, 2Ă— C1, C2, D1), each conjugated to a different bead set using triazine chemistry. Reactivity of the beads was confirmed with rabbit agglutination sera and with experimental pig sera. With a mixture of bead sets, 175 sera from slaughter pigs were investigated for the presence of antibodies against Salmonella. With a combination of ROC analysis (B and D LPS) and a prevalence estimation based on historic data (C LPS), individual cut-offs were defined for each LPS-conjugated bead set, and assay performance was evaluated. Results of the suspension array (BC1C1C2D) suggest that more pigs are seroconverted than indicated by a commercial BC1D1-ELISA, and that most of these extra seropositive samples give a signal on one of the beads with C LPS. These results show that expansion of a standard panel with more C LPS variants improves antibody detection. Conclusions A suspension array for Salmonella serology in pigs was developed, that detects more seropositive sera than ELISA, which is achieved by expanding the panel of Salmonella LPS variants, including C2 LPS. The results demonstrate that bead-based suspension arrays allow for testing of pig sera, with the advantage of being able to set cut-offs per antigen. Ultimately, this type of assay can be applied in routine veterinary serology to test for antibodies against multiple Salmonella serovars (or other pathogens) in one single serum sample, using up-to-date antigen panels.
Schmallenberg virus : technical and scientific studies
Poel, W.H.M. van der - \ 2014
Lelystad : Central Veterinary Institute of Wageningen UR - 67
dierpathologie - schmallenbergvirus - epidemiologie - pathogenese - transmissie - vectoren - diagnose - reverse transcriptase pcr - serologie - wilde dieren - huisdieren - kalveren - lammeren - koeien - schapen - animal pathology - schmallenberg virus - epidemiology - pathogenesis - transmission - vectors - diagnosis - serology - wild animals - domestic animals - calves - lambs - cows - sheep
Schmallenberg virus primarily infects domestic and wild ruminants. Cattle and sheep seem to be the most susceptible species. Goats, pigs and camelids seem to be less susceptible. In pregnant cattle and sheep, the virus can infect multiple organs of the un-borne fetus. However, this infection often does not cause major lesions and infrequently leads to malformations.
Serologie en diagnostiek: een oud verbond in een nieuw jasje
Beckhoven, J.R.C.M. van; Piron, P.G.M. ; Vink, J. ; Vlugt, R.A.A. van der - \ 2006
Gewasbescherming 37 (2006)5 (september 2006). - ISSN 0166-6495 - p. 239 - 244.
serologie - pathogenen - plantmateriaal - vermeerderingsmateriaal - detectie - technieken - elisa - enzymimmunoassay - innovaties - serology - pathogens - planting stock - propagation materials - detection - techniques - enzyme immunoassay - innovations
Diagnostiek van plant pathogenen met behulp van serologische diagnostica is in Nederland al vele tientallen jaren een standaard technologie. Het is een van de pijlers onder ons intensieve en hoogstaande keurings- en kwaliteitssysteem en heeft als zodanig duidelijk bijgedragen heeft aan de vooraanstaande positie die Nederland op agrarisch gebied inneemt. Ondanks de toenemende belangstelling voor moleculair biologische detectiemethoden in de laatste tien jaar, vindt het merendeel van de keuringen bij de Nederlandse Keuringsdiensten en bedrijven nog steeds plaats met behulp van detectiemethoden gebaseerd op antisera. Prime Diagnostics®, onderdeel van Plant Research International BV, is binnen Nederland een van de grootste leveranciers van deze serologische reagentia. Het producten pakket bestaat op dit moment voornamelijk uit polyclonale antisera gericht tegen plantenvirussen (58) en plantpathogene bacteriën (32). Voor meer informatie zie ook de website op www.primediagnostics. nl
Snelle toetsen op Erwinia geven steeds beter zicht op aantasting
Doorn, J. van; Hollinger, T.C. ; Vreeburg, P.J.M. ; Leeuwen, P.J. van; Wolf, J.M. van der; Speksnijder, A.G.C.L. - \ 2006
BloembollenVisie 4 (2006)87. - ISSN 1571-5558 - p. 22 - 23.
bloembollen - erwinia - enterobacteriaceae - methodologie - tests - bereikt resultaat - dna - serologie - landbouwkundig onderzoek - ornamental bulbs - methodology - achievement - serology - agricultural research
Om rot en snot in bloembollen als gevolg van Erwinia goed te kunnen aantonen, zijn diverse toetsen ontwikkeld. Op verschillende fronten is PPO in samenwerking met PRI bezig om snelle en betrouwbare methoden te ontwikkelen
Quantification of Actinobacillus pleuropneumoniae transmission
Velthuis, A. - \ 2002
Wageningen University. Promotor(en): M.C.M. de Jong; J.H.M. Verheijden; N. Stockhofe-Zurwieden. - S.l. : S.n. - ISBN 9789058086792 - 166
varkens - actinobacillus pleuropneumoniae - transmissie - ademhalingsziekten - infectieziekten - longen - serologie - diergeneeskunde - pigs - actinobacillus pleuropneumoniae - transmission - respiratory diseases - infectious diseases - lungs - serology - veterinary science

More insight into the transmission dynamics of bacteria between animals is gained with help of transmission experiments. In a transmission experiment various aspects of transmission can be studied. For example, more insight into the transmission dynamics can be gained, transmission can be quantified, or the effect of interventions on transmission can be quantified so that better-directed intervention strategies can be devised. The main goal of the research described in this thesis was the development of methods to quantify bacterial transmission in an experimental setting. We restricted the research to the transmission of one specific bacterium, i.e. Actinobacillus pleuropneumoniae serotype 9 in pigs. A. pleuropneumoniae is regarded as a primary pathogen that causes pleuropneumonia in pigs and brings considerable economic losses about world-wide. Direct transmission from pig to pig is believed to be the most important transmission route of this bacterium, therefore, prevention or reduction of transmission in direct animal to animal contact should in principle lead to eradication. By conducting several transmission experiments we got a better understanding of the transmission dynamics of the bacterium. It was concluded that an infectious state is related to an A. pleuropneumoniae positive tonsil at necropsy. Another conclusion was that the infectivity of a pig is a tenfold higher on days where more than ten A. pleuropneumoniae bacteria were isolated from the nasal swab than on the other days. Furthermore, new statistical and mathematical methods were developed to estimate or test hypothesis about the level of transmission. Statistical methods were based on the transient state (TS) algorithm. The TS algorithm is based on the stochastic susceptible-infectious-removed (SIR) model and provides a time-dependent probability distribution over the number of infected individuals during an epidemic. TS methods are difficult to calculate due to numerical limitations. Therefore, one would probably resort to the easily applicable but less appropriate final size (FS) methods. So, we investigated the error made when FS methods are used instead of TS methods. This error was generally not substantial. Furthermore, a new method to find a difference in transmission between two treatment groups ( MaxDiff test) has been developed and compared to tests based on FS and TS algorithms and a test based on a Generalised Linear Model (GLM). The GLM test was most powerful in finding a difference in transmission. Next were the TS test and the MaxDiff test, which were approximately equally powerful, but more powerful than the FS test especially when the R 0 in both treatment groups are larger than 1. At the end, we tested the effect of vaccination on the transmission of A. pleuropneumoniae in the newly developed experimental design. The effect of vaccination was quantified with a method based on a generalised linear model, which appeared to be most appropriate for the quantification of A. pleuropneumoniae transmission. The effect of vaccination on the susceptibility could not been demonstrated.

Development of a vaccine for the prevention of hemorrhagic enteritis in turkeys
Hurk, J.V.J.M. van den - \ 1988
Agricultural University. Promotor(en): R.W. Goldbach, co-promotor(en): D. Peters. - S.l. : Van den Hurk - 134
diergeneeskunde - kalkoenen - enteritis - gastro-enteritis - adenoviridae - virusziekten - vaccinatie - immunisatie - immunotherapie - vaccins - serologie - serologische overzichten - taxonomie - veterinary science - turkeys - enteritis - gastroenteritis - adenoviridae - viral diseases - vaccination - immunization - immunotherapy - vaccines - serology - serological surveys - taxonomy
Hemorrhagic enteritis (HE) in turkeys is an acute infectious disease characterized by depression, intestinal bleeding, and death. HE occurs worldwide affecting 6 to 12 week-old turkeys and lasting 4 to 6 days. This economically important disease is caused by hemorrhagic enteritis virus (HEV), a turkey adenovirus which is tentatively classified as a member of the group II avian adenoviruses. Serologically related HEV strains with marked differences in pathogenicity for turkeys have been described. Until recently, only 2 vaccines were available for the prevention of HE in turkeys. Both are live virus vaccines containing avirulent HEV (HEV-A) and both elicit protective immunity in turkeys. However, since the first vaccine is a crude extract prepared from spleens of turkeys infected with HEV-A, and the second vaccine is propagated in a transformed cell line contaminated with Marek's disease virus, their safety features are questionable.

HEV is unique among the adenoviruses because it is not antigenically related with the mammalian or group I avian adenoviruses. Its classification as an adenovirus is based upon common physical, chemical, morphological and structural properties. An adenovirus is composed of 240 hexons and 12 pentons, outer capsid proteins which give the virus its characteristic icosahedral shape, capsid associated proteins, and core proteins associated with the double-stranded linear DNA genome with a molecular weight of 17 - 30 x 10 6. Until recently, HEV and its structural proteins had been poorly characterized due to the lack of a suitable invitro system for virus propagation. In summary, there was a need for an improved vaccine for HE in turkeys, and the development of a such a vaccine would be facilitated by the discovery of a cell type suitable for HEV replication and by a more basic knowledge of the virus itself.

The major goal of the research described in this dissertation was the development and testing of a safe and efficient vaccine for HE in turkeys. In order to achieve this goal, a cell culture system for virus propagation as well as methods to measure virus replication invitro and protection in immunized birds had to be developed. In addition, the knowledge of virus and viral components had to be expanded.

The development and application of sensitive and specific enzyme-linked immunosorbent assays (ELISAs) for the quantitation of HEV antibodies in turkey sera and HEV antigen in tissue extracts is described in Chapter 2. The presence and decline of maternal antibody titers in sera of poults and seroconversion and induction of protective antibody titers in turkeys following immunization with HEV-A were determined by ELISA (Chapters 2 and 6). The ELISA for the titration of antigen was used to monitor protection in turkeys following immunization with HEV-A and challenge with virulent HEV (HEV-V) (Chapter 6). A strong antigenic relationship between HEV-A and HEV-V was measured with both ELISAs.

The characterization of both HEV-A and HEV-V and their structural proteins, purified from spleens of infected turkeys is described in the Chapters 3 and 4. The electron microscopic data on the size (72nm) and structure of the virion and its density in CsCl (ρ= 1.34 g/cm3 ), as well as the profile of the viral polypeptides in polyacrylamide gels showing molecular weights ranging from 96,000 to 9,500, justified the classification of HEV as an adenovirus. The major structural proteins were identified as hexon, penton, penton base, fiber, IIIa, and core proteins based on their structure observed by electron microscopy and/or recognition by specific antibodies. Free hexon and penton proteins, purified by immunoaffinity chromatography using monoclonal antibodies, had identical properties as their counterparts in the virus. The hexon was an important neutralizing antigen. The penton of HEV consisted of a single fiber attached to its penton base, a feature shared with the mammalian adenoviruses and the avian egg drop syndrome 1976 virus, but not with the fowl adenoviruses which have double fibers. In contrast to the many common properties of HEV-A and HEV-V, serological differences between the fibers of and differences in electrophoretic migration between the penton bases of both strains were observed. The IIIa, proteins of HEV and human adenovirus type 2 shared a common epitope. This is the first antigenic relationship detected between avian and mammalian adenoviruses.

The propagation of HEV-A and HEV-V in turkey blood leukocyte cells is escribed in Chapter 5. The presence of HEV in the nuclei of non- adherent as well as in adherent cells was revealed by electron microscopy and by light microscopy, using a fluorescent antibody test. The non-adherent infected cells had the characteristics of immature mononuclear leukocytes while the adherent cells had monocyte-macrophage characteristics. HEV-A could be serially passed in turkey leukokcytes at least seven times. optimum conditions for virus propagation in turkey leukocyte cultures and harvest times were determined. HEV could not be produced in chicken leukocytes.

HEV-A, propagated in turkey leukocyte cell cultures, was tested as a vaccine to prevent HE in turkeys in experimental and field trials (Chapter 6). Immunization of turkeys with live HEV-A resulted in protection against a challenge with HEV-V as measured by the serological response and the absence of clinical disease and HEV antigen in spleens. In the field trials, 19 out of 20 flocks seroconverted within 21 days after vaccination with live HEV-A distributed in the drinking water. The overall immune response of the turkeys in these flocks was 96%. Most importantly, neither clinical nor other adverse effects caused by HEV-A vaccination were observed in any of the vaccinated turkeys in the experimental and field trials. The optimum time of the vaccination of poults was determined in relation to interference with maternal antibodies.

A serological approach to the identification of potato cyst nematodes
Schots, A. - \ 1988
Agricultural University. Promotor(en): A.F. van der Wal; E. Egberts; F.J. Gommers. - S.l. : Schots - 118
heteroderidae - pratylenchus - serologische overzichten - serologie - taxonomie - tylenchidae - globodera - heteroderidae - pratylenchus - serological surveys - serology - taxonomy - tylenchidae - globodera

The potato cyst nematode species G.rostochiensis and G.pallida are a threat to the cultivation of potatoes. Their presence in the soil embodies a potential financial loss to the farmer either because of harvest reduction, or because of rejection of seed potatoes, and other crops with adhering soil, for certification. Together with crop rotation and the use of nematicides, resistant potato varieties are essential for the control of these parasites. A reliable, simple and quick screening test to characterize and monitor field infestations of potato cyst nematodes according to species should improve possibilities for control, by means of cultivating resistant potato varieties. Both parasites are hard to distinguish, and considerable attention has been paid to the identification of these nematode species by methods other than those based on morphological characteristics. Such methods have mostly been based on biochemical entities, but have not proven suitable for routine applications. In this thesis, the outlines are presented of an immunoassay, which is based on species-differentiating monoclonal antibodies, and which can be used for routine purposes.

To raise species-differentiating (monoclonal) antibodies, species-specific antigens must be available. In chapter II the purification of two major groups of heat-stable proteins from homogenates of eggs of G.rostochiensis and G.pallida is described. SDS-polyacrylamide gel electrophoresis revealed two bands specific for G.rostochiensis with apparent molecular weights of 20.7 kD and 18.0 kD, and three bands specific for G.pallida with apparent molecular weights of 21.0 kD, 20.5 kD and 17.0 kD. Two-dimensional gel electrophoresis revealed that actually four thermostable proteins are present in either nematode species, of which two (present in the 17.0 kD and 18.0 kD band respectively) have the same apparent molecular weight but differ in iso-electric point. Conventional antisera made against proteins of either one of the Globodera species were shown to exhibit a strong cross-reactivity with these species-specific proteins.

Monoclonal antibodies (McAbs) hold the promise of better differentiating reagents since they recognize a single epitope with a possible reduction in the extent of cross-reactivity. The development of such antibodies using thermostable proteins of either nematode species as an antigen source is described in chapter IV. The antibodies produced by three of the hybridomas (WGP 1, WGP 2 and WGP 3) bind preferentially to thermostable protein antigens of G.pallida while two other hybridomas (WGR 11 and WGR 12) produce antibodies which prefer binding to proteins of G.rostochiensis . Most of the hybridomas which were isolated, however, produce antibodies which bind to thermostable proteins from both potato cyst nematode species. To quantitate the differences in affinity, binding constants were determined (chapter IV) according to the method as described in chapter III. In immunoblotting experiments, it was demonstrated that all G.pallida specific, and some aspecific, McAbs bind to the same two proteins in a mixture of four thermostable proteins from either G.pallida alone, or G.rostochiensis and G.pallida . Besides their very similar physico-chemical characteristics this can be interpreted as another indication that these proteins are homologous. In addition, the reactivity with thermostable proteins from other commonly occurring cyst nematodes was also investigated. Three categories of McAbs could be distinguished: i) WGP 2 and WGP 3, which only bind to thermostable proteins from G.pallida , ii) WGP 1, which binds to proteins of both G.pallida and G.rostochiensis , and iii) all other McAbs, which bind to thermostable proteins of potato cyst, and other cyst nematodes. In chapter V, the topological relationship between the antigenic sites on the G.rostochiensis and G.pallida antigens as defined by six of these McAbs was determined with a competition ELISA.

From the McAbs so far characterized, a deliberate choice was made with respect to the development of a routine test for the identification of the potato cyst nematodes G.rostochiensis and G.pallida . In chapter VI, the reactivity of these McAbs in a direct ELISA was predicted and verified with the use of the formerly established binding constants.

Thus, the McAbs obtained and characterized in this study establish a basis for the serological identification of the potato cyst nematode species G.rostochiensis and G.pallida by an immunoassay. In chapter VII, the implications of such an assay for the reduction of nematicide applications, and the utilization of resistant potato varieties is discussed.

Purification and serology of GE36 virus from apple and pear
Maat, D.Z. ; Vink, J. - \ 1971
Wageningen : [s.n.] (Mededeling / Instituut voor plantenziektenkundig onderzoek no. 576) - 10
plantenziekten - plantenvirussen - appels - peren - serologie - serologische overzichten - taxonomie - plant diseases - plant viruses - apples - pears - serology - serological surveys - taxonomy
Serologisch onderzoek bij Fusarium oxysporum
Tempel, A. - \ 1959
Wageningen University. Promotor(en): A.J.P. Oort. - Wageningen : Veenman - 60
plantenziekteverwekkende schimmels - deuteromycotina - serologie - serologische overzichten - taxonomie - tuberculariaceae - plant pathogenic fungi - deuteromycotina - serology - serological surveys - taxonomy - tuberculariaceae
Rabbits were immunized with different preparations of F. oxysporum.
Antibodies against culture fluid, homogenized mycelium, mycelial extracts and microconidial suspensions reacted in precipitin tests with both culture fluids and mycelium extracts.

Cross reactions between formae speciales were very common. The gel diffusion precipitin test proved most suitable to differentiate formae speciales . Most sera did not specifically differentiate formae speciales . However some reacted highly specifically.

Concerning the character of the antigens it was concluded that the mycelium contained glycoproteins. The glycoproteins split up into polysaccharides and various proteins both during autolysis in the cultures and during extraction of the mycelium.

Rabbits only produced antibodies against proteins after injection with culture liquids or with saline extracts of mycelium. These proteins varied widely in physical properties and it was very difficult to reproduce the same proteins, even by the same extraction procedure. The polysaccharides were much more stable

but antibodies against them could be obtained only by immunization with microconidia. Probably these polysaccharides were present on the surface of the cell wall of the microconidia.

The study demonstrated that the polysaccharides from the glycoproteins of Fusarium oxysporum were haptens.
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