Just M Vlak

Publications (769) View all

• Article: Truncated VP28 as oral vaccine candidate against WSSV infection in shrimp; an uptake and processing study in the midgut of Penaeus monodon.

  A Kulkarni, J H W M Rombout, I S B Singh, N S Sudheer, J M Vlak, C M A Caipang, M F Brinchmann, V Kiron
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  ABSTRACT: Several oral vaccination studies have been undertaken to evoke a better protection against white spot syndrome virus (WSSV), a major shrimp pathogen. Formalin-inactivated virus and WSSV envelope protein VP28 were suggested as candidate vaccine components, but their uptake mechanism upon oral delivery was not elucidated. In this study the fate of these components and of infectious WSSV, orally intubated to black tiger shrimp (Penaeus monodon) was investigated by immunohistochemistry, employing antibodies specific for VP28 and haemocytes. The midgut has been identified as the most prominent site of WSSV uptake and processing. The truncated recombinant VP28 (rec-VP28), formalin inactivated virus (IVP) and virulent WSSV follow an identical uptake route suggested as receptor mediated endocytosis that starts with adherence of luminal antigens at the apical layers of gut epithelium. Processing of internalized antigens is performed in endo-lysosomal compartments leading to formation of supra-nuclear vacuoles. However, the majority of WSSV-antigens escape these compartments and are transported to the inter-cellular space via transcytosis. Accumulation of the transcytosed antigens in the connective tissue initiates aggregation and degranulation of haemocytes. Finally the antigens exiting the midgut seem to reach the haemolymph. The nearly identical uptake pattern of the different WSSV-antigens suggests that receptors on the apical membrane of shrimp enterocytes recognize rec-VP28 efficiently. Hence the truncated VP28 can be considered suitable for oral vaccination, when the digestion in the foregut can be bypassed.
  Fish &amp Shellfish Immunology 10/2012; · 3.32 Impact Factor
• Source

  Available from: Mark Peter Zwart

  Article: Low numbers of repeat units in variable number of tandem repeats (VNTR) regions of white spot syndrome virus are correlated with disease outbreaks.

  T T T Hoa, M P Zwart, N T Phuong, M C M de Jong, J M Vlak
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  ABSTRACT: 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.
  Journal of Fish Diseases 08/2012; 35(11):817-26. · 2.00 Impact Factor
• Article: Disease will limit future food supply from the global crustacean fishery and aquaculture sectors.

  G D Stentiford, D M Neil, E J Peeler, J D Shields, H J Small, T W Flegel, J M Vlak, B Jones, F Morado, S Moss, J Lotz, L Bartholomay, D C Behringer, C Hauton, D V Lightner
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  ABSTRACT: Seafood is a highly traded food commodity. Farmed and captured crustaceans contribute a significant proportion with annual production exceeding 10 M metric tonnes with first sale value of $40bn. The sector is dominated by farmed tropical marine shrimp, the fastest growing sector of the global aquaculture industry. It is significant in supporting rural livelihoods and alleviating poverty in producing nations within Asia and Latin America while forming an increasing contribution to aquatic food supply in more developed countries. Nations with marine borders often also support important marine fisheries for crustaceans that are regionally traded as live animals and commodity products. A general separation of net producing and net consuming nations for crustacean seafood has created a truly globalised food industry. Projections for increasing global demand for seafood in the face of level or declining fisheries requires continued expansion and intensification of aquaculture while ensuring best utilisation of captured stocks. Furthermore, continued pressure from consuming nations to ensure safe products for human consumption are being augmented by additional legislative requirements for animals (and their products) to be of low disease status. As a consequence, increasing emphasis is being placed on enforcement of regulations and better governance of the sector; currently this is a challenge in light of a fragmented industry and less stringent regulations associated with animal disease within producer nations. Current estimates predict that up to 40% of tropical shrimp production (>$3bn) is lost annually, mainly due to viral pathogens for which standard preventative measures (e.g. such as vaccination) are not feasible. In light of this problem, new approaches are urgently required to enhance yield by improving broodstock and larval sourcing, promoting best management practices by farmer outreach and supporting cutting-edge research that aims to harness the natural abilities of invertebrates to mitigate assault from pathogens (e.g. the use of RNA interference therapeutics). In terms of fisheries losses associated with disease, key issues are centred on mortality and quality degradation in the post-capture phase, largely due to poor grading and handling by fishers and the industry chain. Occurrence of disease in wild crustaceans is also widely reported, with some indications that climatic changes may be increasing susceptibility to important pathogens (e.g. the parasite Hematodinium). However, despite improvements in field and laboratory diagnostics, defining population-level effects of disease in these fisheries remains elusive. Coordination of disease specialists with fisheries scientists will be required to understand current and future impacts of existing and emergent diseases on wild stocks. Overall, the increasing demand for crustacean seafood in light of these issues signals a clear warning for the future sustainability of this global industry. The linking together of global experts in the culture, capture and trading of crustaceans with pathologists, epidemiologists, ecologists, therapeutics specialists and policy makers in the field of food security will allow these issues to be better identified and addressed.
  Journal of Invertebrate Pathology 03/2012; 110(2):141-57. · 2.06 Impact Factor
• Conference Proceeding: Potential management strategies to suppress salivary gland hypertrophyvirus (SGHV) infection in Glossina pallidipes tsetse flies rearing

  A.M.M. Abd-Alla, H.M. Kariithi, A.G. Parker, B.C. Bonning, J.M. Vlak, M. Bergoin, M.J.B. Vreysen
  Abstract Book of the 44th Annual Meeting of the Society for Invertebrate Pathology, Halifax, Nova Scotia, Canada; 08/2011
• Conference Proceeding: The salivary secretome of salivary gland hypertrophy virus-infected tsetse fly Glossina pallipides (Diptera: Glossinidae)

  H.M. Kariithi, I.A. Ince, S. Boeren, A.M.M. Abd-Alla, M.M. van Oers, S. Aksoy, J.M. Vlak
  Abstract Book of the 44th Annual Meeting of the Society for Invertebrate Pathology, Halifax, Nova Scotia, Canada,; 08/2011