Induction and potential molecular mechanism of the enhanced immune response in Procambarus clarkii after secondary encountered with Aeromonas veronii

For a long time, it was believed that invertebrates do not possess acquired immunity and mainly rely on innate immunity for protection against pathogens infection. However, an increasing number of studies have suggested that some form of immune memory can be initiated in invertebrates after primary exposure to the pathogen, which was defined as specific immune priming. In the present study, two experiments were carried out to determine whether specific immune priming can be induced in crayfish (Procambarus clarkii) by Aeromonas veronii, if so, to identify the underlying mechanism. Once being preimmunization by formalin-killed A. veronii, the survival rate, in vitro antibacterial activity and haemocyte phagocytosis rate of crayfish were enhanced, which indicated that better immune protection was obtained. Furthermore, at some time points, the expression of antimicrobial peptide (AMP) and Down syndrome cell adhesion molecule (Dscam) genes was significantly higher in P. clarkii individuals that underwent stimulation twice than in those that were only stimulated once. Taken together, the results suggest that enhanced specific immune protection can be obtained in primed crayfish and that the Dscam molecule, haemocyte phagocytosis function, and AMPs may be involved in this immune priming. The present study provides a better understanding of the molecular mechanism of immune priming in invertebrates.

Automated summary

For a long time, it was believed that invertebrates do not possess acquired immunity and mainly rely on innate immunity for protection against pathogen infection. However, recent studies have shown that invertebrates can exhibit specific immune priming after prior exposure to pathogens, suggesting the presence of immune memory. In this study, crayfish were preimmunized with a formalin-killed pathogen, which resulted in enhanced immune protection and increased expression of certain immune-related genes. These findings contribute to our understanding of the molecular mechanism underlying immune priming in invertebrates.