Disease is a major threat to the sustainable growth and profitability of lobster aquaculture, with periodic disease outbreaks leading to significant mortalities in commercial species. Due to the absence of an antibody-mediated adaptive system in invertebrates, true vaccination against commercially important diseases is not possible. However, trained immunity (TI) may offer a potential disease management strategy for the emerging commercial species, Panulirus ornatus. Trained immunity is a process by which the innate immune system of an organism can develop a memory-like response to certain pathogens or stimuli, resulting in an enhanced response upon secondary exposure. While there is evidence to suggest that trained immunity exists for P. ornatus, the mechanisms by which it works are not yet fully understood. Current thinking is that the process involves epigenetic reprogramming of innate immune cells, leading to changes in their gene expression profiles and functional responses. However, the specific molecular pathways and mechanisms involved in this process are poorly understood..
We present initial results that highlight specific changes in immune gene expression and the production of the antimicrobial peptide defensin in P. ornatus from initial and secondary exposure to a formalin-killed bacterial pathogen. Haemolymph samples were collected from an experiment conducted over a 10-week period. Groups received either a single exposure to the bacterin or an initial followed by a secondary exposure at differing time points. Circulating haemocytes were separated from plasma and immune gene expression profiles assessed while the antimicrobial activity of the remaining plasma was assessed as a measure of an immune response likely to improve disease resistance.