A proteomic approach to assess the host response in gills of farmed Atlantic salmon Salmo salar L. affected by amoebic gill disease

Amoebic gill disease (AGD), caused by the marine ectoparasite Neoparamoeba perurans, is one of the most significant infectious diseases for Atlantic salmon (Salmo salar) aquaculture. Upon colonisation of the host gills, the parasite induces a marked hyperplasia and fusion of the lamellar epithelium, which can severely compromise the host if left untreated. In order to investigate the host response during the disease at a protein level, sequential gill samples were collected and analysed using two-dimensional electrophoresis (2DE), with peptides of interest subjected to LC-MS/MS. Samples were obtained from an experimental challenge using naïve Atlantic salmon smolts and cultured N. perurans. Sampling points were set at 1, 2, 3, 7, 14 and 21 days post-infection, and included both sub-clinical and clinical stages of the disease. A total of 23 proteins differentially expressed between non-infected and infected individuals were successfully identified by LC-MS/MS. Findings included upregulation of prohibitin, cyclophilin A, apolipoprotein A1, ictacalcin, RhoGDP dissociation inhibitor α, components of the heat shock proteins 70 family and histones H3a and H4, and downregulation of peroxiredoxin-5 and cofilin. Among the most significant protein functions identified were cell cycle regulation, cytoskeletal regulation, oxidative metabolism and immunity. This is the first sequential proteomic analysis of gills during N. perurans infection. It is believed that the use of non-target screening techniques can contribute to the knowledge of gill responses to injury and pathogenic insults, including AGD.