iTRAQ-based quantitative proteomic profiling of the immune response of the South African abalone, Haliotis midae

The South African abalone Haliotis midae is a commercially important species farmed at high densities in land-based aquaculture systems. Disease outbreaks have had a severe financial impact on the abalone industry yet the molecular mechanisms underlying the immune response of H. midae remain obscure. In this study, a comparative shotgun proteomics approach using iTRAQ coupled with LC-MS/MS was employed to investigate H. midae proteome changes in response to Vibrio anguillarum challenge. A total of 118 non-redundant, unique haemocyte proteins were identified and quantified, with 16 proteins significantly regulated. Hierarchical clustering and pathway analysis uncovered a coordinated response dominated by calcium and cAMP signalling via activation of MAPK cascades. Early up-regulated biological processes involve phagocytosis, nitric oxide production and ATP-synthesis, whilst down-regulated responses were predominantly involved in the regulation of apoptosis. The late up-regulated response involved protein kinase activity and detoxification processes. Expression of selected proteins was validated by Western blot. A putative allograft inflammatory factor-1 protein was further selected to establish its functional molecular role in haemocytes. Confocal imaging revealed that allograft inflammatory factor-1 regulates phagocytosis via a functional interaction with filamentous actin. This is the first time a high-throughput proteomics approach has been used to investigate the immune response of H. midae. •Comparative shotgun proteomics was used to investigate H. midae immune changes.•118 unique haemocyte proteins were identified by iTRAQ and LC-MS/MS.•Early upregulation involved phagocytosis, endocytosis and ATP-synthesis.•The late immune response involved detoxification processes.•Allograft inflammatory factor-1 regulates phagocytosis and interacts with F-actin.