The Modulation of Immune Responses in Tilapinevirus tilapiae-Infected Fish Cells through MAPK/ERK Signalling

Proteomic and phosphoproteomic profilings reveal distinct cellular responses during Tilapinevirus tilapiae entry and replication

Background

Tilapia Lake virus (TiLV) poses a significant threat to global tilapia aquaculture, causing high mortality rates and severe economic losses. However, the molecular mechanisms underlying TiLV-host interactions remain largely unexplored.

Methodology

We investigated the proteomic and phosphoproteomic changes in two piscine cell lines, E-11 and RHTiB cells, following TiLV inoculation at different time points. Differential protein expressions at 10-min and 24-h post infection were selected for constructing protein-protein interactions and analyzing enriched pathways related to the viral entry and replication.

Results

Our findings revealed significant alterations in protein expression and phosphorylation states, highlighting distinct responses between the cell lines. In E-11 cells, TiLV infection suppressed proteins involved in the Janus kinase-signal transducer and activator of transcription and Fas-associated death domain protein-tumor necrosis factor receptor-associated factor pathways, leading to activation of nucleotide oligomerization domain signaling and apoptosis. In RHTiB cells, TiLV suppressed host cellular metabolism by reducing protein phosphatase activity to facilitate early viral entry, while later stages of infection showed increased activity of myosin heavy chain 9 and enhanced host immune responses via phosphorylation of ribosomal protein L17 and GTPase immunity-associated protein 7 (GIMAP7).

Conclusion

Our study suggested that TiLV employs different strategies to manipulate host cellular pathways depending on the cell type. Further studies are essential to validate these findings and ultimately facilitate the development of effective antiviral strategies.

Knowns and unknowns of TiLV-associated neuronal disease

Tilapia Lake Virus (TiLV) is associated with pathological changes in the brain of infected fish, but the mechanisms driving the virus's neuropathogenesis remain poorly characterized. TiLV establishes a persistent infection in the brain of infected fish even when the virus is no longer detectable in the peripheral organs, rendering therapeutic interventions and disease management challenging. Moreover, the persistence of the virus in the brain may pose a risk for viral reinfection and spread and contribute to ongoing tissue damage and neuroinflammatory processes. In this review, we explore TiLV-associated neurological disease. We discuss the possible mechanism(s) used by TiLV to enter the central nervous system (CNS) and examine TiLV-induced neuroinflammation and brain immune responses. Lastly, we discuss future research questions and knowledge gaps to be addressed to significantly advance this field.

Efficacy of Feed Additives on Immune Modulation and Disease Resistance in Tilapia in Coinfection Model with Tilapia Lake Virus and Aeromonas hydrophila

Coinfections by multiple pathogens, including viruses and bacteria, have severely impacted tilapia aquaculture globally. This study evaluated the impacts of dietary supplementation on red hybrid tilapia (Oreochromis spp.) coinfected with Tilapia lake virus (TiLV) and Aeromonas hydrophila. Fish were divided into three groups: a control group on a normal diet, and two experimental groups received diets supplemented with strategy A, an organic acid blend combined with a lyso-phospholipid-based digestive enhancer, and strategy B, an organic acid blend combined with natural immunostimulants and nutrients. Following exposure to both pathogens, the fish supplemented with strategies A and B showed lower cumulative mortality rates of 50.0% and 41.7%, respectively, compared to 76.3% in the control group. Notably, fish fed with strategy B-supplemented diet displayed a stronger immune response, with a lower expression of il-8, mx, and rsad2, and showed less pathological changes in the liver, spleen, and intestines, suggesting enhanced resistance to coinfection. In contrast, fish receiving strategy A did not exhibit significant changes in the immune-related gene expression or pathogen load, but demonstrate less pathological alterations, indicating intestinal protection. These findings highlight the potential of feed additives, particularly strategy B, to reduce the impact of virus-bacterial coinfections and improve outcomes in tilapia farming.

Tilapia lake virus causes mitochondrial damage: a proposed mechanism that leads to extensive death in fish cells

Background

Tilapia lake virus (TiLV), also known as Tilapinevirus tilapiae, poses a significant threat to tilapia aquaculture, causing extensive mortality and economic losses. Understanding the mechanisms and pathogenesis of TiLV is crucial to mitigate its impact on this valuable fish species.

Methodology

In this study, we utilized transmission electron microscopy to investigate the ultrastructural changes in E-11 cells following TiLV infection. We also examined the presence of TiLV particles within the cells. Cellular viability and mitochondrial functions were assessed using MTT and ATP measurement assays and mitochondrial probes including JC-1 staining and MitoTracker™ Red.

Results

Our findings provide novel evidence demonstrating that TiLV causes cytotoxicity through the destruction of mitochondria. Transmission electron micrographs showed that TiLV particles were present in the cytoplasm of E-11 cells as early as 1 h after infection. Progressive swelling of mitochondria and ultrastructural damage to the cells were observed at 1, 3 and 6 days post-infection. Furthermore, losses of mitochondrial mass and membrane potential (MMP) were detected at 1 day after TiLV inoculation, as determined by mitochondrial probes. The results of the MTT assay also supported the hypothesis that the cell deaths in E-11 cells during TiLV infection may be caused by the disruption of mitochondrial structure and function.

Conclusions

Our study reveals the significant role of mitochondrial disruption in contributing to cellular death during the early stages of TiLV infection. These findings advance the understanding of TiLV pathogenesis and further enhance our knowledge of viral diseases in fish.