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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    Potential of Integrated Mangrove - Shrimp Farming in Bangladesh
    Bosma, Roel - \ 2019
    aquaculture - shrimp - Bangladesh - Mangrove
    Invited key-note speaker for the Trade Delegation at the Bangladesh Embassy, The Hague
    Quantitative analysis of the dose–response of white spot syndrome virus in shrimp
    Ngo, Thuy T.N. ; Senior, Alistair M. ; Culina, Antica ; Santos, Eduardo S.A. ; Vlak, Just M. ; Zwart, Mark P. - \ 2018
    Journal of Fish Diseases 41 (2018)11. - ISSN 0140-7775 - p. 1733 - 1744.
    dose–response - infection - meta-analysis - modelling - shrimp - white spot syndrome virus

    White spot syndrome virus (WSSV) is an important cause of mortality and economic losses in shrimp farming. Although WSSV-induced mortality is virus dose dependent and WSSV infection does not necessarily lead to mortality, the relationships between virus-particle dose, infection and mortality have not been analysed quantitatively. Here, we explored WSSV dose–response by a combination of experiments, modelling and meta-analysis. We performed dose–response experiments in Penaeus vannamei postlarvae, recorded host mortality and detected WSSV infection. When we fitted infection models to these data, two models—differing in whether they incorporated heterogeneous host susceptibility to the virus or not—were supported for two independent experiments. To determine the generality of these results, we reanalysed published data sets and then performed a meta-analysis. We found that WSSV dose–response kinetics is indeed variable over experiments. We could not clearly identify which specific infection model has the most support by meta-analysis, but we argue that these results also are most concordant with a model incorporating varying levels of heterogeneous host susceptibility to WSSV. We have identified suitable models for analysing WSSV dose–response, which can elucidate the most basic virus–host interactions and help to avoid underestimating WSSV infection at low virus doses.

    Effect of copper exposure on histamine concentrations in the marbled crayfish
    Soedarini, B. ; Klaver, L. ; Giesen, D. ; Roessink, I. ; Widianarko, B. ; Straalen, N.M. van; Gestel, C.A.M. van - \ 2013
    Animal Biology 63 (2013)2. - ISSN 1570-7555 - p. 139 - 147.
    metal bioaccumulation - accumulation - toxicity - metallothionein - hepatopancreas - crustacea - decapoda - kinetics - clarkii - shrimp
    Crustaceans can store excess copper in the hepatopancreas, an organ playing a role in digestive activity as well as in neurosecretory control. Here, we studied the effect of copper exposure on the level of histamine, an indicator of food spoilage in edibl
    Low numbers of repeat units in variable number of tandem repeats (VNTR) regions of white spot syndrome virus are correlated with disease outbreaks
    Tran Thi Tuyet, H. ; Zwart, M.P. ; Phuong, N.T. ; Jong, M.C.M. de; Vlak, J.M. - \ 2012
    Journal of Fish Diseases 35 (2012)11. - ISSN 0140-7775 - p. 817 - 826.
    repetitive dna-sequences - complete genome sequence - ribonucleotide reductase - penaeus-monodon - in-vivo - shrimp - virulence - wssv - identification - pathogenicity
    White spot syndrome virus (WSSV) is the most important pathogen in shrimp farming systems worldwide including the Mekong Delta, Vietnam. The genome of WSSV is characterized by the presence of two major 'indel regions' found at ORF14/15 and ORF23/24 (WSSV-Thailand) and three regions with variable number tandem repeats (VNTR) located in ORF75, ORF94 and ORF125. In the current study, we investigated whether or not the number of repeat units in the VNTRs correlates with virus outbreak status and/or shrimp farming practice. We analysed 662 WSSV samples from individual WSSV-infected Penaeus monodon shrimp from 104 ponds collected from two important shrimp farming regions of the Mekong Delta: Ca Mau and Bac Lieu. Using this large data set and statistical analysis, we found that for ORF94 and ORF125, the mean number of repeat units (RUs) in VNTRs was significantly lower in disease outbreak ponds than in non-outbreak ponds. Although a higher mean RU number was observed in the improved-extensive system than in the rice-shrimp or semi-intensive systems, these differences were not significant. VNTR sequences are thus not only useful markers for studying WSSV genotypes and populations, but specific VNTR variants also correlate with disease outbreaks in shrimp farming systems.
    Temperature fluctuation, low salinity, water microflora: Risk factors for WSSV outbreaks in Penaeus monodon
    Tendencia, E. ; Verreth, J.A.J. - \ 2011
    Israeli Journal of Aquaculture-Bamidgeh 63 (2011). - ISSN 0792-156X - 7 p.
    white-spot-syndrome - syndrome-virus-infection - marsupenaeus-japonicus - litopenaeus-vannamei - immune-responses - shrimp - system - aquaculture - crustacea - disease
    White spot syndrome virus (WSSV) has been devastating the shrimp industry for almost a decade. This study compares water parameters, alkalinity, and microflora in three ponds on a farm on Negros Island (Philippines) during two production cycles where WSSV infection resulted in an outbreak in 2006 but not in 2005. The total bacterial count of the pond water in 2005 was about twice as high as in 2006. However, luminous bacterial counts were twice as high in 2006 than in 2005 and total presumptive Vibrio, as counted on Vibrio selective thiosulfate citrate bilesalt sucrose (TCBS) agar, was over ten times higher, with a greater percentage of green colonies. More green colonies might indicate a higher concentration of harmful Vibrio bacteria. Total alkalinity for both production cycles was within the normal range while temperature, salinity, pH, and dissolved oxygen varied and sometimes fell below or exceeded the acceptable range. In 2006, there were more instances during which the temperature fluctuated 3-4 degrees C within the period of 07: 00-17: 00, and salinity more often dropped below 15 ppt. Our survey suggests that WSSV outbreak are triggered by water temperature fluctuations of 3-4 degrees C, coupled with low salinity and a high presumptive Vibrio count.
    Identification of Stressors that Affect White Spot Syndrome Virus (WSSV) Infection and Outbreak in Pond Cultured Penaeus monodon
    Tendencia Alapide, E. ; Verreth, J.A.J. - \ 2011
    Israeli Journal of Aquaculture-Bamidgeh 63 (2011)5. - ISSN 0792-156X - p. 616 - 616.
    polymerase-chain-reaction - fresh-water prawn - litopenaeus-vannamei - macrobrachium-rosenbergii - immune-response - temperature - salinity - shrimp - juveniles - 33-degrees-c
    White spot syndrome virus (WSSV) has been a big problem to the worldwide shrimp industry. Exposure to stressors related to physicochemical water parameters affect WSSV infection but not all WSSV infections result in outbreaks. This paper describes a detailed monitoring of important physicochemical water parameters on a farm with 11 ponds that had WSSV infection. The virus was detected in shrimp exposed to two or more simultaneous stress factors (temperature, pH, water level) or multiple stressors for a number of days. Exposure to more than three stressors resulted in an outbreak of the disease within 3-6 days. Outbreaks were experienced in ponds with a temperature of 26-27°C, a pH lower than 8.0, pH fluctuation of 1.0, and a water depth of less than 1 m. Shrimp stocked in eight of the ponds were successfully harvested after 128-173 days of culture.
    WSSV risk factors related to water physico-chemical properties and microflora in semi-intensive P .monodon culture ponds in the Philippines
    Tendencia Alapide, E. ; Bosma, R.H. ; Verreth, J.A.J. - \ 2010
    Aquaculture 302 (2010)3-4. - ISSN 0044-8486 - p. 164 - 168.
    white-spot-syndrome - syndrome virus wssv - litopenaeus-vannamei juveniles - marsupenaeus-japonicus - immune-responses - shrimp - temperature - salinity - hyperthermia - infection
    Whitespot syndrome virus, WSSV, is the most important among the shrimp diseases. One of the suggested WSSV risk factors is the occurrence of stress since stressors could compromise the shrimp defence system thus increasing the risk of WSSV infection. Stressors are usually related to the physico-chemical properties of both water and pond bottom. This paper investigates the effect of some biotic and abiotic components of the pond ecosystem on WSSV infection and outbreak. Water physico-chemical properties and microflora of 91 production cycles of 8 semi-intensive shrimp farms were analyzed to determine WSSV risk factors, using factor analysis and logistic regression. Fluctuations of temperature and pH are important risk factors that will result to an infection but not necessarily to an outbreak. Exposure to high salinity and high temperature are important factors for an infection to result to an outbreak. The risk of an infection is reduced when the water temperature is high, salinity fluctuations are small, and percentage of yellow Vibrio colonies is greater than the green ones. Further studies are needed to clarify the effects of water depth, water transparency, and various bacterial counts; these factors could be individual or interactive.
    Can VNTRs be used to study genetic variation within white spot syndrome virus isolates?
    Bui Thi Minh Dieu, ; Zwart, M.P. ; Vlak, J.M. - \ 2010
    Journal of Fish Diseases 33 (2010)8. - ISSN 0140-7775 - p. 689 - 693.
    nuclear polyhedrosis-virus - tandem repeats - shrimp - sequence - number
    Evaluation of white spot syndrome virus variable DNA loci as molecular markers of virus spread at intermediate spatiotemporal scales
    Bui Thi Minh Dieu, ; Marks, H. ; Zwart, M.P. ; Vlak, J.M. - \ 2010
    Journal of General Virology 91 (2010)5. - ISSN 0022-1317 - p. 1164 - 1172.
    penaeus-monodon - geographic-distribution - genetic-variation - genome sequence - syndrome wsbv - shrimp - epidemiology - virulence - wssv - evolution
    Variable genomic loci have been employed in a number of molecular epidemiology studies of white spot syndrome virus (WSSV), but it is unknown which loci are suitable molecular markers for determining WSSV spread on different spatiotemporal scales. Although previous work suggests that multiple introductions of WSSV occurred in central Vietnam, it is largely uncertain how WSSV was introduced and subsequently spread. Here, we evaluate five variable WSSV DNA loci as markers of virus spread on an intermediate (i.e. regional) scale, and develop a detailed and statistically supported model for the spread of WSSV. The genotypes of 17 WSSV isolates from along the coast of Vietnam – nine of which were newly characterized in this study – were analysed to obtain sufficient samples on an intermediate scale and to allow statistical analysis. Only the ORF23/24 variable region is an appropriate marker on this scale, as geographically proximate isolates show similar deletion sizes. The ORF14/15 variable region and variable-number tandem repeat (VNTR) loci are not useful as markers on this scale. ORF14/15 may be suitable for studying larger spatiotemporal scales, whereas VNTR loci are probably suitable for smaller scales. For ORF23/24, there is a clear pattern in the spatial distribution of WSSV: the smallest genomic deletions are found in central Vietnam, and larger deletions are found in the south and the north. WSSV genomic deletions tend to increase over time with virus spread in cultured shrimp, and our data are therefore congruent with the hypothesis that WSSV was introduced in central Vietnam and then radiated out
    Haemocyte reactions in WSSV immersion infected Penaeus monodon
    Arts, J.A.J. ; Taverne-Thiele, J.J. ; Savelkoul, H.F.J. ; Rombout, J.H.W.M. - \ 2007
    Fish and Shellfish Immunology 23 (2007)1. - ISSN 1050-4648 - p. 164 - 170.
    spot syndrome virus - monoclonal-antibodies - baculovirus wsbv - shrimp - emphasis - organs
    White spot syndrome virus (WSSV) has been a major cause of shrimp mortality in aquaculture worldwide in the past decades. In this study, WSSV infection (by immersion) and behaviour recruitment of haemocytes is investigated in gills and midgut, using an antiserum against the viral protein VP28 and a monoclonal antibody recognising haemocytes (WSH8) in a double immunohistochemical staining and in addition transmission electron microscopy was applied. More WSH 8+ haemocytes were detected at 48 and 72 h post-infection in the gills of infected shrimp compared to uninfected animals. Haemocytes in the gills and midgut were not associated with VP28-immunoreactivity. In the gills many other cells showed virus replication in their nuclei, while infected nuclei in the gut cells were rare. Nevertheless, the epithelial cells in the midgut showed a clear uptake of VP28 and accumulation in supranuclear vacuoles (SNV) at 8 h post-infection. However, epithelial nuclei were never VP28-immunoreactive and electron microscopy study suggests degradation of viral-like particles in the SNV. In contrast to the gills, the midgut connective tissue shows a clear increase in degranulation of haemocytes, resulting in the appearance of WSH8-immunoreactive thread-like material at 48 and 72 h post-infection. These results indicate recruitment of haemocytes upon immersion infection in the gills and degranulation of haemocytes in less infected organs, like the midgut.
    The potential of producing heterotrophic bacteria biomass on aquaculture waste
    Schneider, O. ; Sereti, V. ; Machiels, M.A.M. ; Eding, E.H. ; Verreth, J.A.J. - \ 2006
    Water Research 40 (2006)14. - ISSN 0043-1354 - p. 2684 - 2694.
    high-intensity - shrimp - mariculture - nutrients - biofilms - culture - systems - growth - ponds
    The effluent from the drumfilter of a recirculation aquaculture system was used as substrate to produce heterotrophic bacteria in suspended growth reactors. The effects of organic carbon supplementation (0, 3, 6, 8 g/l sodium acetate) and of hydraulic retention times (11¿1 h) on bacteria biomass production and nutrient conversion were investigated. Bacteria production, expressed as volatile suspended solids (VSS), was enhanced by organic carbon supplementation, resulting in a production of 55¿125 g VSS/kg fish feed (0.2¿0.5 g VSS/g carbon). Maximum observed crude protein production was 100 g protein/kg fish feed. The metabolic maintenance costs were 0.08 Cmol/Cmol h, and the maximum growth rate was 0.25¿0.5 h¿1. Ninety percent of the inorganic nitrogenous and 80% of ortho-phosphate were converted. Producing bacteria on the drumfilter effluent results in additional protein retention and lowers overall nutrient discharge from recirculation aquaculture systems
    Effects of crushed conspecifics on growth and survival of Penaeus monodon Fabricius post larvae
    Nga, B.T. ; Lürling, M.F.L.L.W. ; Peeters, E.T.H.M. ; Roijackers, R.M.M. ; Scheffer, M. ; Nghia, T.T. - \ 2006
    Aquaculture Research 37 (2006)3. - ISSN 1355-557X - p. 224 - 232.
    different salinity levels - released chemical cues - low dissolved-oxygen - juvenile blue crabs - stocking density - acute toxicity - tiger prawn - culture-systems - nursery system - shrimp
    In the present study, the hypothesis tested was that Penaeus monodon post-larvae (PL) experience lower growth when exposed to crushed conspecifics, which was achieved by exposing individual P. monodon PL with abundant food for 4 weeks to a gradient from 0 to 100 crushed conspecific PL L1. Both dry weight (48.5±7.2 mg) and body size (28.0±1.3 mm) of animals exposed to 1 macerated PL L1 were significantly (P¿0.011) higher than those of animals in treatments with 0, 5 and 10 crushed PL L1 (average over treatments: 25.6±3.2 mg; 23.4±0.5 mm). All animals died within 1 week when exposed to 70 and 100 crushed PL L1, and within 3¿4 weeks when exposed to 50 and 30 crushed PL L1. Exposure time affected mortality and it appeared that LC50 values decreased from 60 to 13 crushed PL L1 from 1 to 4 weeks' exposure. Survival of P. monodon PL was negatively correlated to pH, biological oxygen demand, ammonia and nitrate. In conclusion, low dose of crushed conspecifics has a stimulatory effect on P. monodon PL, as larvae were heavier and larger, while high doses cause high mortality.
    In silico identification of putative promoter motifs of White Spot syndrome virus
    Marks, H. ; Ren, X.Y. ; Sandbrink, H. ; Hulten, M.C.W. van; Vlak, J.M. - \ 2006
    BMC Bioinformatics 7 (2006)309. - ISSN 1471-2105 - 13 p.
    swine-fever virus - nuclear polyhedrosis-virus - virion protein genes - transcriptional analysis - penaeus-monodon - structural proteins - proteomic analysis - genome sequence - shrimp - baculovirus
    Background: White Spot Syndrome Virus, a member of the virus family Nimaviridae, is a large dsDNA virus infecting shrimp and other crustacean species. Although limited information is available on the mode of transcription, previous data suggest that WSSV gene expression occurs in a coordinated and cascaded fashion. To search in silico for conserved promoter motifs (i) the abundance of all 4 through 8 nucleotide motifs in the upstream sequences of WSSV genes relative to the complete genome was determined, and (ii) a MEME search was performed in the upstream sequences of either early or late WSSV genes, as assigned by microarray analysis. Both methods were validated by alignments of empirically determined 5' ends of various WSSV mRNAs. Results: The collective information shows that the upstream region of early WSSV genes, containing a TATA box and an initiator, is similar to Drosophila RNA polymerase II core promoter sequences, suggesting utilization of the cellular transcription machinery for generating early transcripts. The alignment of the 5' ends of known well-established late genes, including all major structural protein genes, identified a degenerate motif (ATNAC) which could be involved in WSSV late transcription. For these genes, only one contained a functional TATA box. However, almost half of the WSSV late genes, as previously assigned by microarray analysis, did contain a TATA box in their upstream region. Conclusion: The data may suggest the presence of two separate classes of late WSSV genes, one exploiting the cellular RNA polymerase II system for mRNA synthesis and the other generating messengers by a new virus-induced transcription mechanism
    Gene-expression profiling of White spot syndrome virus in vivo
    Marks, H. ; Vorst, O.F.J. ; Houwelingen, A.M.M.L. van; Hulten, M.C.W. van; Vlak, J.M. - \ 2005
    Journal of General Virology 86 (2005)7. - ISSN 0022-1317 - p. 2081 - 2100.
    transcriptional analysis - proteomic analysis - dna microarrays - genome sequence - cell-lines - shrimp - identification - baculovirus - infection - proteins
    White spot syndrome virus, type species of the genus Whispovirus in the family Nimaviridae, is a large, double-stranded DNA (dsDNA) virus that infects crustaceans. The genome of the completely sequenced isolate WSSV-TH encodes 184 putative open reading frames (ORFs), the functions of which are largely unknown. To study the transcription of these ORFs, a DNA microarray was constructed, containing probes corresponding to nearly all putative WSSV-TH ORFs. Transcripts of 79 % of these ORFs could be detected in the gills of WSSV-infected shrimp (Penaeus monodon). Clustering of the transcription profiles of the individual genes during infection showed two major classes of genes: the first class reached maximal expression at 20 h post-infection (p.i.) (putative early) and the other class at 2 days p.i. (putative late). Nearly all major and minor structural virion-protein genes clustered in the latter group. These data provide evidence that, similar to other large, dsDNA viruses, the WSSV genes at large are expressed in a coordinated and cascaded fashion. Furthermore, the transcriptomes of the WSSV isolates WSSV-TH and TH-96-II, which have differential virulence, were compared at 2 days p.i. The TH-96-II genome encodes 10 ORFs that are not present in WSSV-TH, of which at least seven were expressed in P. monodon as well as in crayfish (Astacus leptodactylus), suggesting a functional but not essential role for these genes during infection. Expression levels of most other ORFs shared by both isolates were similar. Evaluation of transcription profiles by using a genome-wide approach provides a better understanding of WSSV transcription regulation and a new tool to study WSSV gene function
    Molecular epidemiology of white spot syndrome virus within Vietnam
    Bui Thi Minh Dieu, ; Marks, H. ; Siebenga, J.J. ; Goldbach, R.W. ; Zuidema, D. ; Duong, T.P. ; Vlak, J.M. - \ 2004
    Journal of General Virology 85 (2004)12. - ISSN 0022-1317 - p. 3607 - 3618.
    prawn penaeus-monodon - experimental-infection - genome sequence - fragment-length - syndrome wsbv - shrimp - baculovirus - wssv - proteins - gene
    White spot syndrome virus (WSSV), the sole member of the virus family Nimaviridae, is a large double-stranded DNA virus that infects shrimp and other crustaceans. By alignment of three completely sequenced isolates originating from Taiwan (WSSV-TW), China (WSSV-CN) and Thailand (WSSV-TH), the variable loci in the genome were mapped. The variation suggests the spread of WSSV from a common ancestor originating from either side of the Taiwan Strait to Thailand, but support for this hypothesis through analysis of geographical intermediates is sought. RFLP analysis of eight Vietnamese WSSV isolates, of which six were collected along the central coast (VN-central) and two along the south coast (VN-south), showed apparent sequence variation in the variable loci identified previously. These loci were characterized in detail by PCR amplification, cloning and sequencing. Relative to WSSV-TW, all VN-central isolates showed a similar to8.5 kb deletion in the major variable region ORF23/24, whereas the VN-south isolates contain a deletion of similar to11(.)5 or similar to12(.)2 kb, compared to a similar to1(.)2 or similar to13(.)2 kb deletion in WSSV-CN and WSSV-TH, respectively. The minor variable region ORF14/15 showed deletions of various sizes compared with WSSV-TH for all eight VN isolates. The data suggest that the VN isolates and WSSV-TH have a common lineage, which branched off from WSSV-TW and WSSV-CN early on, and that WSSV entered Vietnam by multiple introductions. A model is presented for the spread of WSSV from either side of the Taiwan Strait into Vietnam based on the gradually increasing deletions of both 'variable regions'. The number and order of repeat units within ORF75 and ORF125 appeared to be suitable markers to study regional spread of WSSV.
    Protection of Penaeus monodon against White Spot Syndrome Virus by oral vaccination
    Witteveldt, J. ; Cifuentes, C. ; Vlak, J.M. ; Hulten, M.C.W. van - \ 2004
    Journal of Virology 78 (2004)4. - ISSN 0022-538X - p. 2057 - 2061.
    major structural proteins - genome sequence - shrimp - infection - identification - japonicus - gene - wssv - resistance - fabricius
    White spot syndrome virus (WSSV) occurs worldwide and causes high mortality and considerable economic damage to the shrimp farming industry. No adequate treatments against this virus are available. It is generally accepted that invertebrates such as shrimp do not have an adaptive immune response system such as that present in vertebrates. As it has been demonstrated that shrimp surviving a WSSV infection have higher survival rates upon subsequent rechallenge, we investigated the potential of oral vaccination of shrimp with subunit vaccines consisting of WSSV virion envelope proteins. Penaeus monodon shrimp were fed food pellets coated with inactivated bacteria overexpressing two WSSV envelope proteins, VP19 and VP28. Vaccination with VP28 showed a significant lower cumulative mortality compared to vaccination with bacteria expressing the empty vectors after challenge via immersion (relative survival, 61%), while vaccination with VP19 provided no protection. To determine the onset and duration of protection, challenges were subsequently performed 3, 7, and 21 days after vaccination. A significantly higher survival was observed both 3 and 7 days postvaccination (relative survival, 64% and 77%, respectively), but the protection was reduced 21 days after the vaccination (relative survival, 29%). This suggests that contrary to current assumptions that invertebrates do not have a true adaptive immune system, a specific immune response and protection can be induced in P. monodon. These experiments open up new ways to benefit the WSSV-hampered shrimp farming industry.
    Protection of Penaeus monodon against white spot syndrome virus using a WSSV subunit vaccine
    Witteveldt, J. ; Vlak, J.M. ; Hulten, M.C.W. van - \ 2004
    Fish and Shellfish Immunology 16 (2004)5. - ISSN 1050-4648 - p. 571 - 579.
    major structural proteins - innate immunity - genome sequence - shrimp - infection - japonicus - identification - baculovirus - resistance - hemocytes
    Although invertebrates lack a true adaptive immune response, the potential to vaccinate Penaeus monodon shrimp against white spot syndrome virus (WSSV) using the WSSV envelope proteins VP19 and VP28 was evaluated. Both structural WSSV proteins were N-terminally fused to the maltose binding protein (MBP) and purified after expression in bacteria. Shrimp were vaccinated by intramuscular injection of the purified WSSV proteins and challenged 2 and 25 days after vaccination to assess the onset and duration of protection. As controls, purified MBP- and mock-vaccinated shrimp were included. VP19-vaccinated shrimp showed a significantly better survival (p <0.05) as compared to the MBP-vaccinated control shrimp with a relative percent survival (RPS) of 33% and 57% at 2 and 25 days after vaccination, respectively. Also, the groups vaccinated with VP28 and a mixture of VP19 and VP28 showed a significantly better survival when challenged two days after vaccination (RPS of 44% and 33%, respectively), but not after 25 days. These results show that protection can be generated in shrimp against WSSV using its structural proteins as a subunit vaccine. This suggests that the shrimp immune system is able to specifically recognize and react to proteins. This study further shows that vaccination of shrimp may be possible despite the absence of a true adaptive immune system, opening the way to new strategies to control viral diseases in shrimp and other crustaceans. (C) 2003 Elsevier Ltd. All rights reserved.
    Genetic variation among isolates of White Spot Syndrome Virus
    Marks, H. ; Goldbach, R.W. ; Vlak, J.M. ; Hulten, M.C.W. van - \ 2004
    Archives of Virology 149 (2004)4. - ISSN 0304-8608 - p. 673 - 697.
    nuclear polyhedrosis-virus - major structural proteins - polymerase-chain-reaction - monoclonal-antibodies - envelope protein - penaeus-monodon - genome sequence - dna-sequences - syndrome wsbv - shrimp
    White spot syndrome virus (WSSV), member of a. new virus family called Nimaviridae, is a major scourge in worldwide shrimp, cultivation. Geographical isolates of WSSV identified so far are very similar in morphology and proteome, and show little difference in restriction fragment length polymorphism (RFLP) pattern. We have mapped the genomic differences between three completely sequenced WSSV isolates, originating from Thailand (WSSV-TH), China (WSSV-CN) and Taiwan (WSSV-TW). Alignment of the genomic sequences of these geographical isolates revealed an overall nucleotide identity of 99.32%. The major difference among the three isolates is a deletion of approximately 13 kb (WSSV-TH) and 1 kb (WSSV-CN), present in the same genomic region, relative to WSSV-TW. A second difference involves a genetically variable region of about 750 bp. All other variations >2 bp between the three isolates are located in repeat regions along the genome. Except for the homologous regions (hrl, hr3, hr8 and hr9), these variable repeat regions are almost exclusively located in ORFs, of which the genomic repeat regions in ORF75, ORF94 and ORF125 can be used for PCR based classification of WSSV isolates in epidemiological studies. Furthermore, the comparison identified highly invariable genomic loci, which may be used for reliable monitoring of WSSV infections and for shrimp health certification.
    Transcriptional analysis of the white spot syndrome virus major virion protein genes
    Marks, H. ; Mennens, M. ; Vlak, J.M. ; Hulten, M.C.W. van - \ 2003
    Journal of General Virology 84 (2003). - ISSN 0022-1317 - p. 1517 - 1523.
    structural proteins - genome sequence - late promoters - shrimp - baculovirus - identification - wssv - expression - infection - encodes
    White spot syndrome virus (WSSV) is a member of a new virus family (Nimaviridae) infecting crustaceans. The regulation of transcription of WSSV genes is largely unknown. Transcription of the major WSSV structural virion protein genes, vp28, vp26, vp24, vp19 and vp15, was studied to search for common promoter motifs for coordinate expression. The temporal expression of these genes and both 5' and 3' ends of the mRNA were determined, using infected crayfish gill tissue as a RNA source. RT-PCR showed that all five genes are expressed late in infection compared to the early ribonucleotide reductase large subunit gene. 5' RACE studies revealed a consensus late transcription initiation motif for only two of the five major virion protein genes. This motif was only found in one other upstream region of the putative translational start site of a gene with unknown function (ORF 158). No other conserved sequence motifs could be detected in the sequences surrounding the transcriptional start sites of the five major virion protein genes. All 5' ends were located about 25 nt downstream of an A/T rich sequence, including the consensus TATA-box sequence for vp15. The absence of a consensus motif is distinct from gene regulation of other large dsDNA viruses and suggests a unique regulation of WSSV transcription, in line with its unique taxonomic position.
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