Transcriptomics analysis of the infected tissue of gibel carp (Carassius auratus gibelio) with liver myxobolosis infers the underlying defense mechanisms from the perspective of immune-metabolic interactions

Abstract Liver myxobolosis, caused by Myxobolus wulii severely prevents the sustainable development of gibel carp (Carassius auratus gibelio) aquaculture in China. More insights into the host-parasite interaction will undoubtedly help to develop potential solutions to control this myxobolosis. Liver is an important organ to perform immunological and metabolic functions, changes of gene expression profile involved in fish liver against the local myxosporean infection, however, remain unknown. Here, a comparative transcriptomic analysis of severely infected and mildly infected liver from the same fish individuals, liquefying liver from the just died fish and control liver from the uninfected fish was conducted to investigate the possible involved molecular responses in the liver against the M. wulii infection. Upregulated differentially expressed genes (DEGs) were predominantly involved in adaptive immune responses, including the anti-inflammatory responses resulted from the synergism of Th1, Th17 and Treg cells, and antibody responses mediated by B cells. Downregulated DEGs were mainly involved in metabolic processes. Furthermore, 10 representative DEGs possibly involving in the immune-metabolic interactions were downregulated in the affected liver, demonstrating that the possible synergic mechanism of the suppression of metabolic activities and the facilitation of anti-inflammatory responses occurred in the infected liver. Combining the significant downregulation of cytoskeleton-related genes and upregulation of cell size-related genes, the histopathological, transmission and scanning electron microscopic analysis, it can be suspected that M. wulii is of intracellular infection. This is the first study to elucidate the molecular mechanism of immune-metabolic interactions underlying the fish liver myxobolosis, which will deepen the knowledge of the fish-myxospoean dialogue.