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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    Vaccinatie van lelies tegen LMoV: een haalbare of ongewenste resistentiestrategie?
    Kock, M.J.D. de - \ 2009
    Lisse : PPO Bloembollen en Bomen - 27
    leliemozaïekvirus - lilium - lelies - plantenziekten - bloembollen - snijbloemen - plantenziektebestrijding - vaccinatie - immunisatie - nederland - lily mottle virus - lilium - lilies - plant diseases - ornamental bulbs - cut flowers - plant disease control - vaccination - immunization - netherlands
    Virusinfecties veroorzaken opbrengstverliezen en beperken tevens het internationale handelsverkeer tussen landen die strikte regelgeving hebben met betrekking tot de aanwezigheid van virussen in het plantenmateriaal. Wanneer een plant met een mild virusisolaat wordt geïnfecteerd, komt het vaak voor dat deze plant niet meer vatbaar (of minder vatbaar) is voor virusisolaten die heftige virussymptomen veroorzaken. Deze natuurlijke manier van geïnduceerde resistentie tegen agressieve virussen wordt cross: protectie genoemd. Het actief besmetten van een plant met een virusisolaat dat milde symptomen laat zien, wordt ook wel ‘vaccineren’ genoemd. Het vaccineren van planten wordt door het Japanse bedrijf Nippon Del Monte (NDM) in de praktijk reeds toegepast. NDM is in het bezit van een mild isolaat van Lilly mottle virus (leliemozaïekvirus, LMoV) dat geen of nauwelijks virussymptomen veroorzaakt en is op zoek naar partners in Nederland om voor dit isolaat de mogelijkheden van cross:protectie te bestuderen. Omdat de vaccinatietechnologie positieve verwachtingen heeft, maar ook onzekerheden, beperkingen en potentiële risico’s kent, wordt in dit rapport toegewerkt naar een collectief besluit of de vaccinatietechnologie in Nederland voeten aan de grond kan gaan krijgen. PPO:BBF heeft een stakeholder: en ketenanalyse gemaakt waarin aangegeven is welke nationale en internationale partijen in de keten betrokken zijn bij de implementatie van de vaccinatie technologie. Tevens is samen met Nederlandse lelieveredelingsbedrijven een lijst met criteria opgesteld waaraan een plantenvaccin (in algemene zin) moet voldoen. In een workshop is de vaccinatietechnologie van NDM getoetst aan deze criteria en vraagstellingen zijn geformuleerd die door middel van vervolgonderzoek beantwoord moeten worden of onderdeel kunnen zijn van validatieonderzoek van de vaccinatietechnologie tegen LMoV onder Nederlandse teeltomstandigheden. Er wordt vooral veel waarde gehecht aan de criteria dat de vaccinatietechnologie niet mag leiden tot teeltbeperkingen, niet mag leiden tot risico:inperkende maatregelen en niet mag leiden tot handelsbeperkingen. Juist omdat introductie van de door NDM voorgestelde vaccinatietechnologie volledig van toepassing is op deze criteria, en deze bezwaren niet eenvoudig op te lossen zijn, is gezamenlijk besloten dat er vanuit Nederland geen interesse is in de ontwikkeling van de vaccinatietechnologie tegen LMoV in lelie. Daarmee komt ook een potentiële collectieve samenwerking met NDM voor een gezamenlijke ontwikkeling van de technologie te vervallen. Tevens wordt er geen vervolgonderzoek opgestart waarin aanvullende onderzoeksvragen worden uitgewerkt. Deze conclusie is samengevat in een Memo die aan NDM is toegestuurd.
    Immuuninterventie : 'Drukken op de juiste knoppen van het afweersysteem'
    Schijns, V.E.J.C. - \ 2009
    Wageningen : Wageningen Universiteit - ISBN 9789085852773 - 32
    immunologie - immuniteitsreactie - immuniteit - immuunsysteem - immunisatie - vaccins - vaccinatie - immunology - immune response - immunity - immune system - immunization - vaccines - vaccination
    Eenvoudige remedies voor stress bij weefselkweekplantjes
    Klerk, G.J.M. de - \ 2007
    Onder Glas 8 (2007)4. - p. 24 - 25.
    vermeerderingsmateriaal - weefselkweek - zaailingen - droogte - stress - genetische modificatie - beschermingsmiddelen - trehalose - immunisatie - proeven - glastuinbouw - propagation materials - tissue culture - seedlings - drought - stress - genetic engineering - protectants - trehalose - immunization - trials - greenhouse horticulture
    Als planten in de natuur onder stress staan, bijvoorbeeld door droogte, beschermen ze kwetsbare componenten door speciefieke stoffen, 'protectants', in grote hoeveelheden aan te maken. Deze manier van bescherming is ook bij weefselkweek te gebruiken. Telers kunnen planten voorbehandelen met milde stress. Daardoor kunnen ze daarna een zware stress doorstaan. Onderzoek met de modelplant Arabidopsis en met lelie, roos en appel geeft uitstekende resultaten. De methoden zijn eenvoudig. Op basis van deze resultaten kan de tuinbouw allerlei toepassingen ontwikkelen
    From phage display to plant expression: Fulfilling prerequisites for chicken oral immunotherapy against coccidiosis
    Wieland, W.H. - \ 2004
    Wageningen University. Promotor(en): Martin Verstegen, co-promotor(en): Arjen Schots; D.V. Orzaéz Calatayud. - Wageningen : S.n. - ISBN 9789085040736 - 132
    kippen - coccidiose - immunotherapie - iga - antilichamen - transgene planten - biotechnologie - immunisatie - immuniteit - immunologie - fowls - coccidiosis - immunotherapy - iga - antibodies - transgenic plants - biotechnology - immunization - immunity - immunology
    The frequency and spectrum of infections with pathogens harbouring resistance to antibiotics and other drugs has dramatically increased over the last years. One of the main causes is the extensive use of antibiotics and other drugs in human and veterinary medicine. Parasites, such as Eimeria causing coccidiosis in chicken and pathogenic bacteria like Salmonellae and Campylobacter are examples of pathogens that acquired resistance. Furthermore, continuous use of drugs in diets of animals kept for human consumption increases the risk of residues in food, that possibly affect human health. These drawbacks of antimicrobial drugs have led to a demand for alternative treatments. In this thesis an alternative approach for prevention of coccidiosis in chicken is described, based on immune intervention by passively administered, plant produced, secretory IgA.As a first step, Eimeria binding IgA fragments were selected using the phage display technique. The phage display system was adapted to be used for the display of chicken Fab fragments. A newly constructed vector, named pChick3, allows straightforward cloning of chicken variable antibody domains in frame with the constant domains of the chicken light chain and the first constant domain of the IgA heavy chain. In a following step, new plant expression vectors were designed and constructed. Ten antibodies, selected from the chicken phage antibody library were then transferred to this vector system and subsequently expressed in planta as full size IgA. Upon expression of the ten selected anti- Eimeria antibodies, differences up to 500-fold in yield were observed. Several factors on translational or protein level could cause the observed differences: e.g. processing, stability, assembly and silencing. Two were tested (silencing, chain compatibility i.e. assembly) and both have an influence on the levels of expression. An explanation may be found in the combination of several factors. These observations lead to the conclusion that an extra in planta selection step is inevitable for successful integration of phage display and plant expression systems. Finally, the structure of the chicken polymeric immunoglobulin receptor was elucidated. In a fashion similar to its mammalian counterpart, this receptor transports IgA to the gut lumen forming secretory IgA. This complex is highly stable, and IgA is protected against degradation by proteases or pH-fluctuation, which makes secretory IgA the most suitable form for passive immunization. Interestingly, the chicken SC comprises only four immunoglobulin-like domains compared to five found in mammals. Thus, an integrated system for both selection and expression of immunoglobulins was developed and with the final achievement of the production of Eimeria -specific secretory IgA in plants, the prerequisites for chicken passive immune therapy were fulfilled.
    Seroepidemiology of diphtheria, tetanus, poliomyelitis and pertussis : evaluation of the national immunisation programme in the Netherlands
    Melker, H. de - \ 1999
    Agricultural University. Promotor(en): D. Kromhout; M.A.E. Conyn-van Spaendonck; J.F.P. Schellekens. - S.l. : S.n. - ISBN 9789058081285 - 205
    immunisatie - serologische overzichten - difterie - tetanus - poliomyelitis - kinkhoest - nederland - immunization - serological surveys - diphtheria - tetanus - poliomyelitis - pertussis - netherlands

    In view of the evaluation of the National Immunisation Programme in the Netherlands the main objectives were to obtain insight into the immunity to diphtheria, tetanus and poliomyelitis, into the occurrence of pertussis and to improve serodiagnosis of pertussis.

    In a population-based nationwide sampling, 8359 sera (response 55%) were collected, and to gain access to orthodox reformed individuals refusing vaccination, in a sample from municipalities with low vaccine coverage 1589 sera (response 52.5%). In the nationwide sample, the prevalence of diphtheria and tetanus antibodies (≥0.01 IU/ml in toxin inhibition assay) was 88% and 84%, resp. In at least 90% antibodies (titre≥1:8 in neutralisation assay) against poliovirus types 1, 2 and 3 were measured. For those born after mass vaccination was introduced (<45 years) the prevalence of antibodies to diphtheria, tetanus, poliovirus types 1 and 2 was at least 92.5% and for poliovirus type 3 at least 80%. Diphtheria and tetanus antibodies decreased with age for those born before vaccination was introduced (≥45 years). Only 40% of orthodox reformed individuals had diphtheria and 60% had tetanus antibodies. Less than 70% had poliovirus type 1, 2 and/or 3 antibodies. We concluded that the Dutch immunisation programme induced long-term diphtheria, tetanus and poliomyelitis immunity. While adults are very well protected against poliomyelitis, a great number of adults lack diphtheria or tetanus antitoxin antibodies. These adults might benefit from diphtheria (re)vaccination; however, offering a primary tetanus vaccination to cohorts born before the introduction of vaccination would probably be more effective than routine revaccination. Introduction of C. diphtheriae or poliovirus in socio-geographically clustered orthodox reformed groups might constitute a danger of spread of these pathogens.

    Pertussis surveillance data from notifications, positive serology and hospital admissions (1976-98) showed a sudden increase in the number of pertussis cases in 1996-97. According to notifications and serology data, the increase among, mostly unvaccinated, children less than 1 year was similar to the increase in hospital admissions. For older, mostly vaccinated, individuals the increase in hospital admissions was relatively small. The increase of reported vaccinated patients of all ages was higher than for unvaccinated patients. We postulated that the proportion of pertussis infections resulting in recognizable symptoms has increased among vaccinated individuals due to a mismatch of the vaccine strain and circulating B. pertussis strains.

    To investigate at which level IgG antibodies against pertussis toxin (IgG-PT) in a single serum sample are indicative for recent pertussis, IgG-PT was analysed in 7756 population-based sera, in sera of 3491 patients with at least a fourfold IgG-PT increase, in paired sera of 89 patients with positive cultures or polymerase chain reactions and in sera of 57 pertussis patients with a median follow-up of 1.4 years. IgG-PT levels of at least 100 U/ml were present in less than 1% of the population, are reached by most pertussis patients within 4 weeks after disease onset and persist only temporarily. We concluded that such levels are diagnostic for recent or actual infection with B. pertussis .

    Our results not only show that childhood vaccination should be sustained, but that adult vaccination could be considered. We have to anticipate long-term effects of mass vaccination, such as gaps in immunity as a result of decreased circulation of the pathogens and waning immunity. Epidemiological studies directed towards evaluation of vaccination should continue to provide a scientific basis for vaccination strategy.

    Besmettelijke dierziekten: geintegreerd aanpakken
    Hanekamp, W. ; Snoep, J. - \ 1998
    Praktijkonderzoek Rundvee, Schapen en Paarden. Praktijkonderzoek 11 (1998)4. - ISSN 1386-8470 - p. 25 - 29.
    diergeneeskunde - melkvee - melkveehouderij - infectieziekten - vaccinatie - immunisatie - immunotherapie - vaccins - preventieve geneeskunde - ziektepreventie - preventie - diergezondheid - hygiëne - ziekteoverdracht - dieren - zoönosen - veterinary science - dairy cattle - dairy farming - infectious diseases - vaccination - immunization - immunotherapy - vaccines - preventive medicine - disease prevention - prevention - animal health - hygiene - disease transmission - animals - zoonoses
    Omdat het dier de belangrijkste besmettingsbron is, is aankoop van vee een grote risicofactor en dienen mensen die veel in contact komen met dieren bedrijfskleding aan te trekken.
    Immunological aspects of oral vaccination in fish
    Joosten, P.H.M. - \ 1997
    Agricultural University. Promotor(en): W.B. van Muiswinkel; J.H.W.M. Rombout. - S.l. : Joosten - ISBN 9789054856986 - 134
    vissen - diergeneeskunde - vaccinatie - immunisatie - immunotherapie - vaccins - geneesmiddelen - farmacologie - toedieningswijzen - reticulo-endotheliaal systeem - antilichamen - immunoglobulinen - immunologische technieken - elisa - immunochemie - fishes - veterinary science - vaccination - immunization - immunotherapy - vaccines - drugs - pharmacology - application methods - reticuloendothelial system - antibodies - immunoglobulins - immunological techniques - elisa - immunochemistry

    In this thesis immunological consequences of oral vaccination in fish have been described. The efficacy of oral vaccination can be increased by protection of the antigen against degradation in the foregut, in order to reach the hindgut in sufficient quantities for uptake and subsequent activation of the mucosal and systemic immune system. Using a specific monoclonal antibody, in addition to mucosal B cells, a distinct mucosal T cell population was demonstrated, which may play an important role in local immunity. Furthermore, two approaches to protect antigens against digestive degradation are described: bioencapsulation and microencapsulation. For the first approach antigen is encapsulated in living food, and subsequently fed to juvenile carp and seabream. In carp, oral vaccination at 2 and 4 weeks old resulted in immunological tolerance. However, in older carp (8 weeks old) and seabream (8 and 10 weeks old), immunological memory was induced. It can be concluded that oral vaccination with bioencapsulated bacterial antigens is effective for oral vaccination of juvenile fish, when applied at the right age. For microencapsulation an alginate microparticle system was studied, which may be more suitable for vaccination of older fish. The supernatant appeared to be the most immunogenic fraction of a bacterin, which is taken up in the hindgut and evokes best memory formation. This fraction was encapsulated in alginate microparticles and fed to adult carp and trout. Different microparticle preparations, with respect to release time and antigen concentration, were needed for immunological memory formation in each fish species. Therefore, oral vaccination with bacterial antigens in alginate microparticles can be effective. Oral tolerance against protein antigens was demonstrated in animals fed with ferritin or recombinant VHS G protein. However, the immune response to ovalbumin appeared to be carp strain dependent. A carp strain that produced specific antibodies after injection with OVA was selected and repeated feeding of OVA, prior to injection, resulted in increased antibody titres in serum. Oral tolerance induction in fish therefore appeared to depend on the protein and possibly also on genetic factors.

    Computer simulation to support policy-making in Aujeszky's disease control
    Buijtels, J.A.A.M. - \ 1997
    Agricultural University. Promotor(en): A.A. Dijkhuizen; R.B.M. Huirne; M.C.M. de Jong. - S.l. : Buijtels - ISBN 9789054856528 - 187
    ziekte van marek - ziekte van aujeszky - varkens - diergeneeskunde - vaccinatie - immunisatie - immunotherapie - vaccins - investering - kosten-batenanalyse - economische evaluatie - computersimulatie - simulatie - simulatiemodellen - dynamisch programmeren - markov-processen - economie - gebruikswaarde - economische impact - nederland - marek's disease - aujeszky's disease - pigs - veterinary science - vaccination - immunization - immunotherapy - vaccines - investment - cost benefit analysis - economic evaluation - computer simulation - simulation - simulation models - dynamic programming - markov processes - economics - use value - economic impact - netherlands

    Aujeszky's disease is a contagious viral disease that affects the central nervous system of pigs. Several eradication programs or measures are available, each of them providing different results. Determining the preferred strategy is to a large extent a matter of economic consideration.

    Under the EU rules, countries or regions that are Aujeszky-free can ban imports of breeding animals carrying antibodies of the disease; movements to Aujeszky-free areas from other areas of both breeding and rearing pigs are subject to strict conditions and controls, which differ depending on whether or not the area of origin has an EU-approved eradication program. If important import destinations achieve disease-free status, exporting countries that have failed to eradicate the disease will be severely penalized. Therefore, sterner demands are to be expected considering control and eradication of Aujeszky's disease in the Netherlands in the future. To meet these demands, the objective of this study was to develop a computer simulation environment in which "what-if' scenarios can be performed to explore the epidemiological and economic effects of different Aujeszky's disease control programs. The model can be used to support the choice of the optimal eradication program under various conditions, in particular from an epidemiological and economic point of view.

    First, a flexible economic framework to evaluate Aujeszky's disease eradication programs was developed, and illustrated with an example (Chapter 2). The framework has four elements: changes in percentage of infectious herds, changes in product quantities, changes in product prices and economic integration. Each of these elements is defined as a separate module in the simulation model and has its own input and output data, depending on the control strategy under consideration. With these elements all epidemiological and economic aspects of the disease can be monitored over time.

    In an illustrative example, probability distributions of the number of infectious herds corresponding to each control strategy were compared and the optimal strategy was chosen, according to the risk attitude of the decision maker. The framework can be considered a standardized approach in comparing and selecting animal health control strategies by integrating technical and economic data and principles.

    To obtain epidemiological information with respect to the control of Aujeszky's disease virus, an epidemiological state-transition simulation model was constructed to evaluate the spread of the virus (Chapter 3). In the model, the population of herds in the Netherlands is subdivided into four herd types: great-grandparent stock+multiplier, rearing, farrowing and fattening. Every time step, each herd is in one of 32 states per herd type. The states are based on (1) the reproduction ratio R ind , which is the number of individuals infected by one infectious individual, (2) the prevalence for each value of R ind and (3) the expected number of infectious animals in an infectious herd within each prevalence range of the herds. The different values Of R ind are based as much as possible on field data and experiments, where different vaccination strategies were applied.

    The transition matrix with the probabilities of every possible transition from one state to another was calculated on a weekly base. With this matrix the distribution of herds over states from week to week was derived. To include the non-linearity of the transmission process, the transmission probabilities from non-infectious to either non-infectious or infectious were developed such that they depend on the state vector itself The fraction of herds that becomes infectious equals one minus the fraction of herds that has not been infected by the virus emitted by infectious herds.

    Calculations revealed that infection in the Dutch pig population would not disappear without vaccination, nor with a vaccination scheme in which sows were vaccinated less than 3 times per year and fattening pigs once per cycle (Chapter 4). The infection, however, would be eradicated within 2 to 3 years, if sows were vaccinated 3 or 4 times per year and fattening pigs twice per cycle. The outcome turned out to be sensitive to the impact of other than animal contacts on the number of new effective virus introductions per time unit.

    The structure of the production pyramid and herd density in the affected regions were other important factors which influenced the course of infection. To examine the impact of these factors the total number of herds in the Netherlands were further subdivided into four regions (North, East, West-Middle, South).

    Outcomes showed that the percentage of infectious herds in equilibrium was highest for rearing herds (76.3%) and lowest for great-grandparent stock+multiplier herds (20.0%) if no vaccination was done. The herd type "fattening" had more impact on the effectivity of the different vaccination strategies than the herd type "farrowing". This difference is becoming less if more intensive vaccination strategies are applied. Besides the difference in herd type, also herd density and the percentage of non-vaccinated herds were an important factor in the eradication process.

    After simulating these epidemiological characteristics of Aujeszky's disease virus, market outcomes and pig producers' returns were simulated under different scenarios with respect to closure of export markets for live piglets and fattened pigs (Chapter 5). If the Netherlands fails to eradicate Aujeszky's disease before its trading partners in these markets, live piglet exports would be banned, reducing industry revenue and export earnings by about 9% and 10% respectively in the medium term. If exports of live fattened pigs are also banned, the reductions are 26 and 32% respectively. The piglet-producing sector would be more
    severely affected than the fattening sector. The model also showed that, if export markets for carcasses were also to close for an unspecified food safety reason, capacity of the industry would fall over 50%.

    Lastly four control strategies to eradicate Aujeszky's disease virus in the Netherlands were compared epidemiologically and economically (Chapter 6). Vaccination decreased the number of cases per production loss. The decrease was largest if vaccination strategy changed from "no vaccination" to the less intensive vaccination. Extra vaccinations under more intensive vaccination strategies, however, still had impact. The attendant costs were highest per dead animal (especially for gilts) and per abortion. Growth delay of gilts and piglets turned out to be of minor importance.

    The sales distribution on the piglet markets (import, export and on the domestic markets) was particularly influenced by vaccination, but the decreases in revenues were only less than 4.3%. The only exception was the number of piglets and live animals that were imported into the Netherlands, which decreased by more than 15% and about 9% respectively. The accompanying revenues from piglets and fattened pigs were highest if "no vaccination" was done. Compared with the revenue in this strategy, this difference is greatest on the piglet market, as the decrease in revenue was about 3.6%, while the decrease was about 0.55% on the market of fattened pigs.

    According to the resulting present values over a period of 10 years, "no vaccination" is economically the best solution only if no trade restrictions are to be expected. Economically speaking, however, the most intensive vaccination strategy should be applied, if an export ban of two years on live animals to, for instance, Germany is expected within 10 years after the start of the vaccination strategy. A prolonged export ban makes this strategy even more favourable. From an economic point of view intermediate vaccination strategies are never preferred.

    The main conclusions of this thesis are:
    - State-transition simulation proves to be an appropriate method to evaluate transmission of Aujeszky's disease virus. The epidemiological information obtained can well be used in economic evaluation of different control strategies.
    - Aujeszky's disease is only eradicated in the Netherlands if the most intensive vaccination strategy (≥3 times per year) is applied for breeding sows, and fattening pigs are vaccinated at least once per cycle.
    - If applying the most intensive vaccination strategy, it takes about 200 weeks for an average herd to become non-infectious.
    - The relative impact of other than animal contacts on the number of new virus introductions increases from 4% to 98%, if the vaccination strategy is changed from "no vaccination" to the most intensive vaccination program.
    - Subdivision of the total population into herd types and regions is important to enhance insight into transmission of infection in the pig population and to support decision making at regional level.
    - Price equilibrium models can well estimate the short-term changes in prices as well as those in the medium term. To accomplish this, it is of importance that sufficient historical data about quantities, prices and the infections occurred are available to estimate the required parameters accurately. A monthly data-set of about 10 years turned out to be sufficient.
    - Direct production losses from Aujeszky's disease virus are less than 6% of the vaccination costs when vaccination is carried out. More than 80% of these losses are caused by growth delay of fattening pigs.
    - The most intensive vaccination strategy (i.e., sows are vaccinated 3 or 4 times per year and fattening and rearing pigs twice per cycle) is economically preferred if an export ban on part of the live animals is expected during at least 2 years within 10 years after the start of the vaccination program. If this is not to be expected then "no vaccination" turns out to be the best strategy. The risk of an export ban on live animals should justify the eradication of the virus from the population.
    - For the current situation in the Netherlands it is economically preferred to start blood sampling all sows and remove the gE-positive animals instead of continuing vaccination, provided that the additional risk of new introductions of the virus is sufficiently limited.

    Introductie van virusresistentie in lelie door middel van genetische modificatie : eindverslag van het project 'Inbouw van virusresistentie in lelies via genetische manipulatie'
    Langeveld, S.A. ; Bol, J.F. ; Boonekamp, P.M. - \ 1996
    Lisse : Laboratorium voor Bloembollenonderzoek (Urgentieprogramma Bollenziekte- en veredelingsonderzoek ) - 19
    plantenziekten - plantenvirussen - bloembollen - plantenveredeling - ziekteresistentie - plaagresistentie - genetische modificatie - recombinant dna - planten - immunisatie - geïnduceerde resistentie - onderzoek - lilium - plant diseases - plant viruses - ornamental bulbs - plant breeding - disease resistance - pest resistance - genetic engineering - plants - immunization - induced resistance - research
    Effect van moment van vlekziektevaccinatie op het interval spenen-bronst
    Riel, J. van; Vesseur, P. - \ 1996
    Praktijkonderzoek varkenshouderij 10 (1996)2. - ISSN 1382-0346 - p. 5 - 5.
    erysipelothrix - vruchtbaarheid - immunisatie - immunotherapie - infectieziekten - oestrus - biggen - zeugen - vaccinatie - vaccins - diergeneeskunde - spenen - erysipelothrix - fertility - immunization - immunotherapy - infectious diseases - oestrus - piglets - sows - vaccination - vaccines - veterinary science - weaning
    In de praktijk zijn er vragen over de gevolgen van vlekziektevaccinaties voor de vruchtbaarheid. Een oriënterende studie heeft aanwijzingen opgeleverd dat enten in de eerste week van de lactatie een negatieve invloed heeft op het interval spenen-bronst.
    Het inbrengen van genen coderend voor antibacteriele eiwitten bij wilg ter bescherming tegen de watermerkziekte
    Roest, S. ; Dam, B.C. van; Evers, P.W. - \ 1994
    Wageningen : IBN (IBN - rapport 082)
    bosbouw - genetische modificatie - immunisatie - immunogenetica - geïnduceerde resistentie - plantenziekten - plantenziekteverwekkende bacteriën - planten - recombinant dna - bomen - salix alba - brenneria salicis - forestry - genetic engineering - immunization - immunogenetics - induced resistance - plant diseases - plant pathogenic bacteria - plants - trees
    Een betere diergezondheid door beheersen en vrijwaren van dierziekten!
    Swinkels, H. ; Kemp, B. ; Vesseur, P. - \ 1994
    Praktijkonderzoek varkenshouderij 8 (1994)4. - ISSN 1382-0346 - p. 6 - 8.
    diergezondheid - huisvesting, dieren - ziektebestrijding - bedrijfssystemen - gezondheid - hygiëne - immunisatie - immunotherapie - varkens - screenen - vaccinatie - vaccins - diergeneeskunde - animal health - animal housing - disease control - farming systems - health - hygiene - immunization - immunotherapy - pigs - screening - vaccination - vaccines - veterinary science
    Het is echter zo dat het klant is koning principe ook van kracht is in de varkenssector. Derhalve zullen de Nederlandse varkenshouders met het oog op behoud van de huidige exportpositie moeten blijven streven naar verbetering van de kwaliteit van het eindproduct.
    Her-entingen tegen Pseudo Vogelpest (NCD) op 'Het Spelderholt'
    Voorst, A. van - \ 1993
    Praktijkonderzoek voor de Pluimveehouderij 4 (1993)3. - ISSN 0924-9087 - p. 4 - 6.
    kippen - immunisatie - immunotherapie - pseudovogelpest - pluimvee - vaccinatie - vaccins - diergeneeskunde - fowls - immunization - immunotherapy - newcastle disease - poultry - vaccination - vaccines - veterinary science
    Pseudo Vogelpest of NCD is een gevreesde virusziekte, waartegen een entverplichting geldt. Na het uitbreken van de ziekte in het zuiden van Nederland is al het volwassen pluimvee op Het Spelderholt opnieuw geënt.
    Engineering resistance against potato virus Y
    Vlugt, R.A.A. van der - \ 1993
    Agricultural University. Promotor(en): R.W. Goldbach; H. Huttinga. - S.l. : Van der Vlugt - ISBN 9789054850847 - 111
    plantenziekten - plantenvirussen - solanum tuberosum - aardappelen - potyvirus - planten - immunisatie - geïnduceerde resistentie - genetica - genetische variatie - evolutie - soortvorming - immunogenetica - genetische modificatie - recombinant dna - plant diseases - plant viruses - solanum tuberosum - potatoes - potyvirus - plants - immunization - induced resistance - genetics - genetic variation - evolution - speciation - immunogenetics - genetic engineering - recombinant dna

    Potato virus Y is the type species of the potyvirus genus, the largest genus of the plant virus family Potyviridae. The virus causes serious problems in the cultivation of several Solanaceous crops and although certain poly- and monogenic resistances are available, these can not always be employed, e.g. R y genes in potato cv. 'Bintje'. The aim of the research described in this thesis was to establish new forms of resistance against PVY by genetic modification of host plants. One such form of genetic engineered resistance is 'coat protein-mediated resistance', whereby expression of a viral coat protein (CP) in a transgenic plant may confer resistance against infection with the homologous virus, and some closely related viruses.

    At the start of this investigation no sequence data on the RNA genome of PVY were available, therefore cDNA synthesis and subsequent sequence determination was performed to obtain the necessary PVY CP gene sequence as well as additional sequences from the 3'-terminal region of the viral genome (Chapter 2 and Van der VIugt et al., 1989). This enabled the determination of the exact taxonomic position of the PVY N('tobacco veinal necrosis strain') isolate used in these experiments, among other PVY isolates from at least two different strains. Detailed comparisons of the PVY NCP and 3'-non translated (3'-NTR) sequences with those from a large number of geographically distinct PVY isolates that became available during the course of this investigation, showed that these sequences, in addition to distinguish between different potyvirus species (Ward and Shukla, 1991; Frenkel et al., 1989), can also be used for the distinction between strains of one potyvirus (Chapter 3, Van der VIugt et al., 1992a). Several strain specific amino acid sequences in the CPs and nucleotide sequences in the 3'-NTRs could be discerned, that are possibly involved in virulence and/or symptom expression. Further experiments are required to elucidate the precise biological significance of these sequence motifs. Interestingly the sequence comparisons as complied in Chapter 3 also confirmed the high levels of CP and 3'-NTR sequence identity between the PVY isolates at one hand and one putative isolate of pepper mottle virus (PepMoV, Dougherty et al., 1985) at the other, as described previously (Van der VIugt et al., 1989; Van der Vlugt, 1992). Initially described as an atypical strain of PVY (PVY-S, Zitter, 1972) PepMoV was later found to be serologically and biologically distinct from PVY (Purcifull et al., 1973, 1975; Zitter and Cook, 1973). Recent determination of the complete genomic RNA sequence of a Californian isolate of pepper mottle virus (PepMoV-C; Bowman-Vance et al, 1992a,b) and comparisons between a Florida isolate of PepMoV and PVY (Hiebert and Purcifull, 1992) however, suggest that PepMoV represents a distinct potyvirus though more closely related to PVY than to any other potyvirus. Additional sequence information of other, biologically well characterized, isolates of PepMoV, like a virus isolate apparently intermediate between PepMoV and PVY (Nelson and Wheeler, 1978), will hopefully aid in establishing the exact taxonomic position of this pepper infecting virus in the genus Potyvirus. Generally it is to be recommended that of all virus isolates whose (partial) sequences are under investigation, precise origin and other relevant biological characteristics are also accurately documented.
    In contrast to all other viruses for which 'CP-mediated resistance' has been described sofar, potyviruses do not express their CPs from a distinct, separate gene but through proteolytic cleavage of a polyprotein precursor. This necessitated the
    addition of translational start signals, directly upstream of the CP encoding sequence, in order to enable expression of the PVY NCP in transgenic potato and tobacco plants. Potato tuber disc and tobacco leaf disc transformations with these constructs resulted in large numbers of transgenic plants (Chapters 4 and 5). Despite the fact that a large number of transgenic plants was tested for CP expression, using a highly sensitive enzyme-amplification based ELISA format, in none of the plants significant amounts of viral CP could be detected. Whether this is caused by the extra N-terminal methionine residue, or improper folding of the CP, resulting in decreased stability of the protein, or by inefficient protein extractions, possibly resulting from protein insolubility, is not known. It remains to be tested whether transformation of plants with a construct in which a functional protease domain is coupled to a potyviral CP with an intact protein processing sequence, will result in high levels of expression of the CP. For more practical purposes however, PVY CP expression levels appear not to be of significant importance since the protection against PVY, observed in the transgenic tobacco plants (Chapter 5 and 6), is apparently RNA-mediated, i.e. prima rily based on the presence of the CP encoding RNA rather than on the coat protein itself. Transgenic tobacco lines expressing PVY CP transcripts devoid of a translational start signal (CP -ATG), possess equal levels of protection against both mechanically inoculated virus and virus transmitted by the natural aphid vector Myzuspersicae (Chapter 5 and 6). It seems highly unlikely that the protection in these CP -ATGplants is based on minute amounts (i.e. less then 0.0001 % of the total soluble protein) of a truncated viral polypeptide since the presence of six translational stopcodons preceding the first in-frame AUG startcodon, 162 nucleotides down stream the 5'-end of the CP encoding sequence, will prevent expression of such a polypeptide.

    Analysis of the transgenic potato lines (Chapter 4) showed that most lines, as the transgenic tobacco lines, expressed CP specific RNA transcripts. Under the given greenhouse conditions, however, in none of the transgenic plants protection to PVY could be determined. In view of the results obtained with the transgenic tobacco lines, it may be anticipated that virus challenging of additional transgenic potato lines, under more optimal greenhouse conditions, will reveal similar levels of RNA-mediated virus resistance as observed in tobacco. For all practical purposes genetically engineered resistance based on the presence of RNA molecules is to be preferred over forms of resistance that are based on the expression of a (foreign) protein. Apart from being energetically more favourable for the plant, it is likely to aid in the acceptance of genetically modified crop plants by both politicians and the public, something which might, in the next few years, turn out to be the major obstacle in the successful application of plant transformation techniques.

    At this stage one can only speculate on the mechanism(s) on which this RNAmediated resistance is based. Transformation of plants with partial CP or other PVY Ngenomic sequences will help in identifying the protection mechanism(s) involved and show whether regions other than the CP-encoding domain can be equally effective in conferring virus resistance. If the resistance is based on a 'sense-RNA' effect, i.e. hybridization of the positive sense transgenic RNA to negative-sense viral RNA replication intermediates, thereby blocking further virus replication, the ribozyme technology might prove an efficient expansion of this genetically engineered type of resistance. Ribozymes, RNA sequences capable of specific and catalytic cleavage of other RNA-sequences, are able to cleave target RNAs efficiently and catalytically in vitro . The antiviral application of ribozymes in transgenic plants however has sofar demonstrated not to be very successful and reported protection levels are not yet exceeding those obtained with antisense RNAs (Edington and Nelson, 1992). Chapter 7 describes the design and synthesis of hammerhead ribozymes capable to cleave a highly conserved region from the PVY RNA dependent RNA-polymerase cistron. It was shown that the correct formation of the hammerhead cleavage complex, determined at least in part by the lengths of the antisense arms of the ribozyme, forms an important factor in the efficiency of cleavage. Cellular and full-length viral RNA molecules generally posses extended, unknown secondary structures which are likely to hamper precise formation of hammerhead structures, which requires bimolecular basepairing. Correct hammerhead formation and efficient cleavage of these RNAs will therefore require ribozymes with rather long basepairing arms. These long antisense arms however will make catalytic cleavage rather unlikely since complex dissociation will probably become the rate limiting factor. For this reason one can assume that ribozymes will only be successful when introduced into specific antisense RNA molecules, directed against the less abundant viral complementary strands, rather than as highly efficient RNA cleaving "enzymes".

    Geen effect aujeszky-enting op de technische resultaten
    Bakker, J. - \ 1991
    Praktijkonderzoek varkenshouderij 5 (1991)4. - ISSN 1382-0346 - p. 6 - 7.
    ziekte van Aujeszky - agrarische bedrijfsvoering - immunisatie - immunotherapie - arbeid (werk) - ziekte van Marek - varkens - vaccinatie - vaccins - diergeneeskunde - werkplanning - Aujeszky's disease - farm management - immunization - immunotherapy - labour - Marek's disease - pigs - vaccination - vaccines - veterinary science - work planning
    Op dit moment worden alleen gl-negatieve vaccins gebruikt. Dit om onderscheid te kunnen maken tussen de antistoffen gemaakt door het vaccin en het veldvirus, dat de ziekte van Aujeszky veroorzaakt. Het onderzoek is toen uitgevoerd op het Varkensproefbedrijf te Sterksel om de gevolgen van de vaccinatie op de technische resultaten na te gaan op een bedrijf, waarop geen verschijnselen van de ziekte van Aujeszky voorkomen. Er bleek geen effect van de vaccinatie op de technische resultaten te kunnen worden aangetoond.
    Duurzame resistentie tegen pathogenen via genetische modificatie; utopie of werkelijkheid voor de gewasbescherming in het jaar 2000?
    Wit, P.J.G.M. de - \ 1991
    Wageningen : Landbouwuniversiteit Wageningen - 31
    plantenziektekunde - plantenziekteverwekkende schimmels - plantenziekten - plantenvirussen - plantenziekteverwekkende bacteriën - planten - immunisatie - geïnduceerde resistentie - plantenveredeling - ziekteresistentie - plaagresistentie - colleges (hoorcolleges) - genetische modificatie - recombinant dna - plant pathology - plant pathogenic fungi - plant diseases - plant viruses - plant pathogenic bacteria - plants - immunization - induced resistance - plant breeding - disease resistance - pest resistance - lectures - genetic engineering - recombinant dna
    E. Coli K99 specific B-cell formation in lymphoid tissues of cattle and its significance for bovine monoclonal antibody production : some preliminary results
    Wissink, H.C.G. ; Veerhuis, R. ; Booman, P. - \ 1989
    Zeist : IVO (IVO - report B-321) - 22
    antilichamen - antigenen - rundvee - hybridoma's - immunisatie - immunotherapie - monoclonale antilichamen - vaccinatie - vaccins - diergeneeskunde - antibodies - antigens - cattle - hybridomas - immunization - immunotherapy - monoclonal antibodies - vaccination - vaccines - veterinary science
    Monoclonal antibodies in animal production : their use in diagnostics and passive immunization
    Booman, P. - \ 1989
    Agricultural University. Promotor(en): C.C. Oosterlee; E.J. Ruitenberg. - S.l. : Booman - 149
    zoötechniek - monoclonale antilichamen - hybridoma's - diergeneeskunde - vaccinatie - immunisatie - immunotherapie - vaccins - obstetrie - zwangerschap - immunologische technieken - elisa - zootechny - monoclonal antibodies - hybridomas - veterinary science - vaccination - immunization - immunotherapy - vaccines - obstetrics - pregnancy - immunological techniques - elisa
    One of the landmarks in immunology was the invention and development of monoclonal antibody-secreting hybridomas by Milstein and his coworkers. The enormous promise of monoclonal antibody technology, which became apparent soon after its discovery, may explain the unusual speed with which monoclonal antibodies have been applied to biological and medical sciences.

    In animal production monoclonal antibodies are increasingly finding application in the areas of diagnostics, passive immunization and fundamental research. In Chapter 1 of this thesis some applications of monoclonal antibodies within these areas, with emphasis on reproduction, are discussed. It has been concluded that the particular advantages of monoclonal antibodies can firstly and most easily be shown in immunodiagnosis. Once a hybridoma producing a monoclonal antibody appropriate for a particular application has been obtained, large amounts of a homogeneous and reliable reagent are available for as long as they are needed. As ingredients in test kits, monoclonal antibodies have rapidly replaced conventional polyclonal antibodies.

    An example of a typical diagnostic test in animal production in which monoclonal antibodies might be used is the milk-progesterone test for confirmation of oestrus and pregnancy diagnosis in cattle. In Chapter 2 the production and characterization of monoclonal antibodies against progesterone have been described in order to standardize an enzyme immunoassay for milk-progesterone. The antibodies differed considerably in their binding affinity for progesterone and showed distinct specificities for a variety of steroids. Results show that, although the technique of monoclonal antibody production selects antibodies specific for a single antigenic determinant, this does not always preclude the possibility of cross-reactivity. Moreover, most antibodies produced have affinities far below the corresponding conventional antisera, as has been discussed in Chapter 1. The monoclonal antibody with the highest association constant and relatively good specificity did not detect progesterone with any greater sensitivity than the conventional polyclonal sera. However, since monoclonal antibodies avoid the dependency upon animals producing high quality antisera and improve test standardization, a commercially available rapid progesterone cow-side test has been designed based on the monoclonal antibody with the best characteristics.

    Results of Chapter 2 underline the necessity to evaluate carefully the need of producing monoclonal instead of polyclonal antibodies for a given antigen, as considerable time and effort are required to obtain a monoclonal antibody with suitable properties. Preselection of antibodies on affinity and specificity in an early stage makes the monoclonal antibody technology more efficacious. In our laboratory a cocktail of related steroids was used to enable such an early selection of antibodies against either oestrone or oestrone sulphate. Testing the replacement of oestrone, coupled to horse- radish peroxidase, from the antibodies made it possible to produce high affinity monoclonal antibodies with nearly unique specificities in a relatively short time. Experiments are in progress to develop a test for pregnancy diagnosis in pigs in faecal samples based on those antibodies.

    Another application in diagnostics is the use of monoclonal antibodies against a male-specific protein, the H-Y antigen, for sexing bovine embryos before implantation. H-Y is a weak antigen and immunization with H-Y antigen in an inbred strain of mice usually results in production of low titered, low affinity antisera. Because only a low percentage of mice has a good antibody response and their sera run out quickly, monoclonal antibodies were produced (Chapter 3). Male specificity of the antibodies was tested in a variety of assays including enzyme immunoassays based on various sources of soluble H-Y and indirect immunofluorescence assays based on binding of the antibodies to H-Y antigen on the cell surface of male and female cells obtained from a number of tissues and species. Several monoclonal antibodies appeared to be positive in all assays tested, suggesting that the molecule conferring the H-Y antigenicity lacks speciesspecificity and appears to be identical for soluble and membrane-bound H-Y antigen.

    The most promising monoclonal antibodies reactive with the H-Y antigen have been evaluated for their efficiency in sexing Day 7 bovine preimplantation embryos (Chapter 4). Although in an indirect immunofluorescence assay a discrimination between male and female embryos could be made, evaluation of the staining patterns was fairly subjective because of non-specific binding of the monoclonal antibodies to the embryonic cells. After modifying the technique in order to reduce non-specific binding, the number of false positives after sexing under these conditions was greatly reduced, which suggests that the monoclonal antibodies detect a male-specific antigen. It was concluded that the occurrence of false-negative embryos might be caused by a weak expression of the H-Y antigen and/or a low affinity of the monoclonal antibody for bovine cell-surface H-Y antigen. The antibodies used in our experiments had been selected on basis of their binding to both soluble and cell-surface H-Y antigen originating from different sources. Currently, monoclonal antibodies which are selected on high affinity for protein structural determinants on bovine cell-surface H-Y antigen are being produced in order to be used in a highly discriminating sensitive fluorescence assay.

    In Chapter 1 has been discussed that it will take some time to fully realize the potential of monoclonal antibodies in the area of passive immunization or immunomodulation. The production costs are still relatively high and the reaction of the animal to the injected antibodies may limit the effects of passive immunization. Some such limitations are illustrated in the experiments in which anti- progesterone murine monoclonal antibodies were administered to cyclic pigs (Chapter 5). Intravenous injection of increasing amounts of anti- progesterone antibodies resulted in a concomitant rise in levels of antibody-bound progesterone. At the same time a significant rise in plasma concentrations of total progesterone was observed immediately after administration of higher doses of antibodies. Therefore, the net effect of progesterone binding by the antibody was relatively small and more or less independent of the quantities of antibody administered. It has been suggested that animals maintain adequate levels of free progesterone in their circulation by resorption of progesterone from a pool present in body tissues. The effects of administration of anti-progesterone antibodies on plasma levels of free progesterone are, however, not only influenced by the proposed compensating effect of resorption, but also by the possible initiation of a humoral response of the pigs to the injected antibodies. In the experiments described in Chapter 5 it is shown that a minimum dose of 32 mg anti-progesterone antibody elicited an antimouse response after the first injection, having an neutralizing effect on the anti-progesterone monoclonal antibodies administered with the second injection. When smaller quantities of antibody were used, an anti-mouse reaction was detected after the second or third injection.

    From reports concerning the therapeutic use of monoclonal antibodies in man it is known that such an immune response may be directed partially against the isotypic determinants, partially against the idiotypic determinants of the murine antibodies administered. Although anti- idiotypic responses cannot be excluded as a complicating factor, homologous antibodies might offer some advantages over their murine counterparts in terms of effectiveness for passive immunization.

    In Chapter 6 the construction of a bovine-murine heteromyeloma cell line to be used for the production of bovine monoclonal antibodies has been described. It was anticipated that a heteromyeloma would retain the superior fusion characteristics of the mouse myeloma cells and, because of the presence of bovine chromosomes, would be better able to support stable bovine antibody production than interspecies hybridomas produced by fusing mouse myeloma cells with bovine lymphocytes. First (bovine-murine) and second generation (bovine-[bovine-murine]) fusion partners were compared for fusion efficiency and the generated number of antigen- specific antibody-producing clones. In addition, the optimal time- interval between boosting and harvesting of the lymphocytes for fusion and the source of lymphocytes was studied. It could be concluded that fusion of bovine lymph node cells with the second generation heteromyelomas on Day 7 after the final booster injection resulted in the largest number of specific antibody-producing clones. Experiments with a third generation bovine-murine heteromyeloma cell line indicated that fusion efficiency could be further improved (unpublished data). Studies with anti-rotavirus and anti-pregnant mare serum gonadotrophin (PMSG) bovine monoclonal antibodies, produced with the second generation fusion partners, indicate that the heteromyeloma cell lines are very useful for the production of bovine monoclonal antibodies.

    The availability of such bovine monoclonal antibodies offers the possibility to compare the efficacy of homologous and heterologous antibodies in cattle after repeated passive immunization. The in vivo immunoneutralization of PMSG by murine and bovine monoclonal antibodies was chosen as a model for such a study (Chapter 7). Results indicate that repeated injection of murine monoclonal antibodies against PMSG (mMCA) alone did not, or only to a small degree, elicit an anti-mouse immune response. The simultaneous administration of mMCA and PMSG resulted in relatively high levels of anti-mouse antibodies after the second injection, leading to a decrease in neutralizing activity of mMCA. The results suggest that the neutralizing activity of mMCA is inhibited more by anti- idiotypic than by anti-isotypic antibodies against mMCA. After repeated administration of the bovine monoclonal antibody against PMSG (bMCA), either alone or in combination with PMSG, no anti-bMCA antibodies could be detected. In addition, no change in plasma levels of bMCA and PMSG, compared with levels after the first injection, was observed. Although it has to be confirmed by further experiments whether our findings can be generalized, the present results suggest that for repeated passive immunization in cattle homologous antibodies are to be preferred above heterologous antibodies. As far as we can see now it is necessary to evaluate carefully the need to produce homologous or heterologous antibodies, dependent on the amounts of antibody to be administered and the number of treatments.

    In conclusion, the potential of monoclonal antibodies for diagnostic use, therapy or fundamental research, discussed in Chapter 1, together with the results presented in this thesis indicate that the monoclonal antibody technology will have an important impact on the improvement of animal quality and productivity.

    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.

    Active immunisation against somatostatin increases milk yield in goats
    Garssen, G.J. ; Welling, A.M.A.W. ; Spencer, G.S.G. - \ 1986
    Zeist : I.V.O. (I.V.O.-rapport B-288) - 22
    antilichamen - endocrinologie - geiten - hormonen - immunisatie - immunoglobulinen - immunotherapie - reticulo-endotheliaal systeem - somatotropine - vaccinatie - vaccins - diergeneeskunde - antibodies - endocrinology - goats - hormones - immunization - immunoglobulins - immunotherapy - reticuloendothelial system - somatotropin - vaccination - vaccines - veterinary science
    In dit onderzoek is nagegaan wat het effect is van actieve immunisatie tegen somatostatine op de melkproduktie van de geit, door 6 geiten, halverwege de dracht geimmuniseerd met een conjugaat van somatostatine en humaan alfa-glubuline, te vergelijken met 6 andere geiten van dezelfde jaargang met een vergelijkbare melkproduktie en gewicht die alleen met globuline waren geimmuniseerd. Somatostatine, een 14 aminozuren tellend peptide, is o.a. betrokken bij de regeling van de groeihormoon-afgifte door de hypofyse, waarop het remmend werkt
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