Transcriptomic analysis and discovery of genes involving in enhanced immune protection of Pacific abalone (Haliotis discus hannai) in response to the re-infection of Vibrio parahaemolyticus.

Traditionally, invertebrates were thought to lack immune memory owing to a lack of acquired immune-related factors such as immunoglobulin. Nonetheless, with the in-depth consideration of invertebrate immune priming, scholars have gradually realized that the immune defenses of invertebrates are more complex than previously imagined. In the current investigation, the survival rate of Vibrio parahaemolyticus re-infected Haliotis discus hannai (VV group) was significantly different from the other groups (p < 0.05), indicating that an enhanced immune response may commence after first exposure to the same strain of V. parahaemolyticus. The transcriptome profiles of hemocytes obtained 102,052 unigenes, and 27,449 of them were annotated successfully. Venn diagram analysis showed that 2832 DEGs commonly responded to the first and second immune responses. 1734 "immune response genes" and 1460 "potential immune-enhancing genes" were also identified. A comparison of both "immune response genes" and "potential immune-enhancing genes" revealed 1019 immune-enhancing regulatory genes and 281 essential immune-enhancing genes. According to the KEGG enrichment analysis results of ERGs and EEGs, classical immune-related signaling pathways, such as NF-kappa B signaling pathway, NOD-like receptor signaling pathway, IL-17 signaling pathway, and TLR signaling pathway were significantly enriched, indicating that they were all involved in the response to V. parahaemolyticus re-infection and were likely dominant in the immune enhancement process of H. discus hannai hemocytes. The intermolecular interactions generated by Cytoscape after re-infection of V. parahaemolyticus appear more intuitively to demonstrate that hemocytes regulation was not an independent process, but rather an intricate regulatory network. H. discus hannai demonstrated enhanced immunological activity after re-infection with V. parahaemolyticus, showing immune memory in hemocytes. The current study's findings have broadened the study of immune enhancement in invertebrates and laid the framework for future research into the molecular mechanism of immune enhancement in abalones.