The Immune Priming in Aquaculture Invertebrates: Inspiration From Cellular Perspective and Future Investigation

Aquatic invertebrates account for more than 33.4% of global aquaculture production and are important aquaculture animals worldwide. Although the frequent outbreaks of diseases and the lack of disease prevention strategies have greatly hindered further development of the invertebrate aquaculture industry. Immune priming is a phenomenon that invertebrates mount a faster and stronger secondary response than that of the primary response when encountered with a given microbe. It has been demonstrated to be present in a wide range of aquaculture species and would provide a fresh idea for disease prevention. As the main executors of immune defense in invertebrates, the circulating hemocytes are short-lived, and the solution for the paradox of keeping a long-lasting immune protection might lie in the formation of long-lived memory cells in immune priming. As a reference for the access of memory cell formation processes in aquaculture invertebrates, the cellular kinetics including expansion, contraction, and memory formation of lymphocytes in the adaptive immunity of vertebrates are discussed. Then the features of hemocytes in aquaculture invertebrates, and their kinetic changes of cell number and immune capacity during immune priming are summarized for the knowledge of a stronger secondary immune response. The regulatory roles of epigenetic modification and metabolic reprogramming in immune priming and their possible functions in memory cell formation and identification are proposed to be preferentially investigated for further clarifying the mechanism of immune priming, which might provide a novel entrance for understanding the mechanisms of immune priming and developing disease prevention strategy in aquaculture invertebrates.