White Spot Syndrome Virus Interaction with a Freshwater Crayfish

Sammanfattning: Viruses are very abundant in water and hence diseases caused by viruses are common in marine organisms. These diseases create great problems for the commercial farming of crustaceans and mussels. One of the most common and most disastrous diseases for shrimp is caused by the white spot syndrome virus (WSSV), which is spread all around the world and also is infecting many different species of crustaceans including freshwater crayfish. Although during recent years knowledge has been gathered on the ways in which invertebrates defend themselves against bacteria and fungi virtually nothing is known about the defence processes elicited by virus. The aim of this work was to develop a model to use for studies of virus-host interactions in vivo and in vitro.Temperature was found to be important for the virus infectivity and at lower temperature the virus apparently did not replicate, but if animals kept at low temperature for more than 40 days were transferred to higher temperatures they died quickly due to an increased virus replication. In crayfish infected with the virus it was found that hemocytes did not degranulate and the melanization reaction was also inhibited in the hemocyes. Thus it is apparent that this virus interacts with the immune system and hemocytes in particular and to be able to study this in some greater detail it was necessary to develop a cell culture to study virus-host interactions at the molecular level. Hence, we have developed a stem cell culture from the hematopoietic tissue (hpt) that will differentiate and mature into hemocytes and which can be used to replicate the WSSV in the presence of an endogenous cytokine, astakine. Astakine is the first cytokine like-factor described which is directly involved in hematopoiesis in an invertebrate.