Research into the penaeid prawn viral response has resulted in the identification of various genes with antiviral roles along with antiviral response pathways such as immune priming from prior exposure to virus and RNAi silencing. Although the components of these pathways continue to be elucidated, the underlying mechanisms of some major viral defences are still unknown. The penaeid immune response to Gill-associated virus has been studied here, including investigation of the potential for immune priming with protein subunits and observation of the regulation of genes with expected immune function. Gill-associated virus is extremely prevalent in farmed and wild-caught prawns in North-eastern Australia, responsible for disease and mortality similar to that of the closely related Yellow-head virus.
To date, antiviral response research has focused almost exclusively on White spot syndrome virus; the study of immune pathways, and characterisation of immune genes in response to other viruses such as Gill-associated virus will provide a method for comparison and potential for investigation of the mechanisms involved. The generality of the protection response observed in penaeid prawns pre-exposed to White spot syndrome virus proteins has been investigated in response to Gill-associated virus proteins. Fragments of the nucleocapsid and envelope glycoproteins were expressed bacterially and eukaryotically and injected intramuscularly before viral challenge. No evidence for protection was observed but the vaccination trials were greatly hindered by high levels of mortality and unavailability of disease-free animals. As well as investigation of immune priming, genes differentially regulated in response to White spot syndrome virus and believed to have roles in viral trafficking were analysed in response to Gill-associated virus. This includes Ras superfamily GTPases and proteins with C-type lectin-like domains. The expression response was compared with the response to WSSV as well as development of dsRNA to attempt to knockdown expression of these genes and observe the impact on infection.
Investigation of the penaeid response to Gill-associated virus therefore has the potential to improve the control strategies utilised in protecting farmed prawns from this economically significant virus as well as add to the understanding of the mechanisms involved in penaeid viral response.