| Crucian carp is the fifth largest aquaculture species in freshwater aquaculture in our country,and the infection of crucian carp with Cyprinid herpesvirus 2(CyHV-2)has caused huge economic losses.Preliminary studies have shown that CyHV-2 can infect the intestinal tract of crucian carp and damage the intestinal mucosa.In order to further explore the mechanism of CyHV-2-induced intestinal injury,this study revealed the intestinal pathological changes and molecular mechanism caused by CyHV-2 infection through histopathology,in situ hybridization and intestinal transcriptome analysis.Elucidating the effect of intestinal injury on CyHV-2 infection provides a scientific basis for exploring the mechanism of intestinal bacterial translocation after viral infection,and also provides a good tool for the study of the pathological mechanism of fish enteritis and the development of enteral nutrition technology.The main results are as follows:1.CyHV-2 was used for intraperitoneal injection and immersion infection of crucian carp respectively.The results showed that CyHV-2 infection could infect the foregut,midgut and hindgut.HE staining and in situ hybridization were performed on the intestinal tract of the diseased fish.HE staining showed that the virus infection led to the reduction of intestinal mucosal layer thickness,the destruction of intestinal folds and the digestion of intestinal villi.In situ hybridization showed that CyHV-2 was mainly enriched in the submucosa of crucian carp intestine,and the lymphocytes and neutrophils in it may be sensitive cells of CyHV-2.2.Transcriptome sequencing analysis of CyHV-2-infected intestinal tissue revealed a total of 6239 differential genes,of which 3345 genes were significantly up-regulated and2894 genes were significantly down-regulated.The results of KEGG enrichment analysis showed that the apoptosis pathway was significantly up-regulated.In the analysis of differentially expressed genes,apoptosis-related genes TRAIL,TRAIL-R,Fas,caspase 8and caspase 7 were significantly up-regulated;RIPK3,the main gene of necroptosis was also significantly up-regulated;the main gene of tight junction protein,Occludin was significantly down-regulated.It is suggested that the apoptosis caused by CyHV-2 may be the main cause of intestinal injury in crucian carp,and RIPK3-dependent necroptosis and tight junction Occludin may also be involved.3.5% dextran sodium sulfate(DSS)was used to perform oral and intestinal lavage on crucian carp to construct an intestinal injury model.The intestinal injury model of crucian carp was successfully established by histopathological observation,the expression of inflammatory-related cytokines,and the verification of intestinal MPO activity.Then,CyHV-2 was used for immerse infection of the intestinal injury model of crucian carp.The results showed that the death process of the DSS treatment group was faster than that of the control group,and the final survival rate was lower.It indicated that the intestinal injury of crucian carp would exacerbate CyHV-2 infection. |
