Establishment of an LMBV-infection model in zebrafish larvae and its application in studying virus-host interactions

Abstract

Largemouth bass virus (LMBV) causes high transmission efficiency and mortality in freshwater aquaculture industry. However, the host responses to LMBV infection, particularly the molecular mechanisms involved in vivo, remain largely uncertain. Zebrafish has been developed as a powerful model organism for the study of host inflammation and immune response upon pathogen infections. Here, we evaluated the susceptibility of LMBV to zebrafish larvae and investigated the host response upon virus infection using transcriptomic analysis. LMBV replicated well in larvae by inoculation with LMBV via the brain and the duct of Cuvier, but the later showed more severe systemic infection, evidenced by the cumulative mortality, the increased transcriptions of viral core genes, and the presence of mcp positive signal in infected larvae. After inoculation with LMBV via the duct of Cuvier, we observed numerous viral particles in the head and tail regions of infected larvae. Moreover, ROS and TUNEL positive signaling also significantly increased in LMBV infected larvae. Of note, a great deal of neutrophils migrated towards the virus infected sites during LMBV infection. Transcriptomic analysis showed that a total of 1263 genes were up-regulated and 1039 genes were down-regulated in response to LMBV infection. Enrichment analysis indicated that the majority of the enriched KEGG pathways were associated with metabolism, cell death and immune regulation, such as fatty acid metabolism, steroid hormone biosynthesis, PPAR signaling, apoptosis, necroptosis, phagosome, cytokine-cytokine receptor pathway, NOD-like receptor signaling, and toll-like receptor pathway. For instance, cell death related signaling molecules including casp9,fas,tnfα and sqstm1 were significantly up-regulated, while camk2a,sept4b and akt1 were down-regulated in response to LMBV infection. Thus, our data firstly established LMBV-infected model in zebrafish larvae which could provide an alternative means for investigation of LMBV-host interaction in vivo, and application for high throughput drug screening in the future.