Investigating the interplay between Cryptocaryon irritans ectoparasite infection and the immune responses of the head kidney in silver pomfret (Pampus argenteus)

Cryptocaryoniasis is one of the devastating protozoal diseases present in marine fish species, leading to high mortality in the fish aquaculture. Recently, white spot disease caused by Cryptocaryon irritans was found to infect the fins and skin of silver pomfret (Pampus argenteus). To better understand the innate immune effects underlying the host response against C. irritans, transcriptome analysis of head kidney (HK) in silver pomfret between non-infected group (sham control) and C. irritans infected was performed. In total, 5141, 3678, and 3895 differentially expressed genes (DEGs) were identified between the control and either 3, 7 or 14 days post infection (dpi), respectively. KEGG enrichment analysis results showed that C. irritans infection induced a complex immune response regulated by the cooperation of various immune related pathways, including ECM-receptor interactions, p53 signaling pathway, cytokine-cytokine receptor interaction, and Jak-STAT signaling pathway. Additionally, the histopathological structure of the HK underwent dynamic changes characterized by renal structure damage and focal necrosis throughout the course of the infection. Furthermore, the levels of the immune-related enzyme (LZM, SOD, ACP and AKP) activities were significantly increased at various time points after infection. Taken together, the findings of this study will not only provide novel insights into the essential first line defense mechanisms involved in the host-C. irritans interaction but also contribute to advance research efforts aimed at developing disease prevention strategies for silver pomfret aquaculture industry.