Immune defence White Spot Syndrome Virus infected shrimp, Penaeus monodon

White spot syndrome virus (WSSV) is the most important viral pathogen of cultured penaeid shrimp worldwide. Since the initial discovery of the virus inTaiwanin 1992, it has spread to shrimp farming regions in Southeast Asia, theAmericas, Europe and theMiddle Eastcausing major economic losses. The virus has a wide host range among crustaceans and induces distinctive clinical signs (white spots)on the inner surface of the exoskeletonof penaeid shrimps.Limited data is available about the immune response genes of P. monodon upon a WSSV infection. This thesis describes the results of our study into the generation of tools, like the generation of a dedicated microarray enabling the analysis of induction and regulation of (innate) immune defence genes in the host that are activated upon infection. Moreover, a putative vaccination strategy to protect shrimp against lethal WSSV infections has been developed previously. We have also analysed the induction of protective vaccination for induction and regulation of gene expression using this microarray.The first focus had been on the haemocyte response of the shrimp upon an immersion infection (chapter 2). Immunocytochemistry and electron microscopy has been used to study the infection route of WSSV in gills and gut up to 3 days after immersion infection. Using a mouse haemocyte specific monoclonal antibody (WSH8) and a rabbit VP28 polyclonal antibody, double immunoreactivity could be observed. Differential haemocyte characteristics in the gills and the midgut of P. monodon were determined.An invasion of haemocytes in the gills was observed in Penaeus monodon upon WSSV-infection, possibly caused by the adherence of haemocytes to the haemolymph vessels. Although many infected cells were found in the gills, haemocytes were not WSSV-infected in this organ. Gills appear to be an important site of haemocyte invasion after immersion infection. In the midgut, uptake of WSSV in the epithelium could be detected, however, infected nuclei