The largemouth bass ranavirus (LMBRaV) caused significant mortality and economic loss in the largemouth bass aquaculture industry around the world, including China. Vaccination is an efficient method for virus defense. In this study, an inactivated LMBRaV vaccine was prepared, and the prevention effect as well as the immune responses were analyzed after the primary and the secondary immunization. Compared to the control group, the counts of leucocytes and erythrocytes increased and peaked at day 14 after the primary immunization, and the proportions of leucocytes, including lymphocytes, monocytes, and neutrophils, were also up-regulation after the primary immunization. Serum neutralizing antibody titers increased and peaked (1:128) at day 28 after the primary immunization. Following the secondary immunization, antibody titers were increased to a higher level (1:512) at 28 days after the secondary immunization. Quantitative real-time PCR analysis demonstrated varying degrees of up-regulation of mhc II, igM, il-1β, and cd8α transcriptions in the head kidney, which showed that innate and adaptive immune responses were both induced after the primary and the secondary immunization. After challenge with LMBRaV, the relative percent survival rates (RPS) for primary and secondary immunization with inactivated LMBRaV vaccine were determined to be 62.92% and 95.51%, respectively. Therefore, this study suggests that utilizing an inactivated LMBRaV vaccine could induce efficient immune responses and antibody, which might provide a potential efficient countermeasure for LMBRaV prevention.

In recent years, the potent influence of tocotrienol (T3) on diminishing blood glucose and lipid concentrations in both Mus musculus (rats) and Homo sapiens (humans) has been established. However, the comprehensive exploration of tocotrienol’s hypolipidemic impact and the corresponding mechanisms in aquatic species remains inadequate. In this study, we established a zebrafish model of a type 2 diabetes mellitus (T2DM) model through high-fat diet administration to zebrafish. In the T2DM zebrafish, the thickness of ocular vascular walls significantly increased compared to the control group, which was mitigated after treatment with T3. Additionally, our findings demonstrate the regulatory effect of T3 on lipid metabolism, leading to the reduced synthesis and storage of adipose tissue in zebrafish. We validated the expression patterns of genes relevant to these processes using RT-qPCR. In the T2DM model, there was an almost two-fold upregulation in pparγ and cyp7a1 mRNA levels, coupled with a significant downregulation in cpt1a mRNA (p < 0.01) compared to the control group. The ELISA revealed that the protein expression levels of Pparγ and Rxrα exhibited a two-fold elevation in the T2DM group relative to the control. In the T3-treated group, Pparγ and Rxrα protein expression levels consistently exhibited a two-fold decrease compared to the model group. Lipid metabolomics showed that T3 could affect the metabolic pathways of zebrafish lipid regulation, including lipid synthesis and decomposition. We provided experimental evidence that T3 could mitigate lipid accumulation in our zebrafish T2DM model. Elucidating the lipid-lowering effects of T3 could help to minimize the detrimental impacts of overfeeding in aquaculture.

Background: Epizootics of largemouth bass ranavirus (LMBRaV) in largemouth bass (Micropterus salmoides) populations are associated with elevated mortality and significant financial losses. Given the lack of effective and safe medication to treat this disease, oral vaccination, which directly targets the intestinal mucosal immune system, is crucial for disease resistance. Methods: This study utilized carboxymethyl cellulose (CMC) to coat LMBRaV inactivated vaccine (LIV) (micro-CMC@LIV). The morphology and characteristics of the CMC microcapsules were determined. In vitro simulated gastric and intestinal conditions were used to validate that the microcapsules could tolerate gastric conditions and subsequently release their contents in the intestinal tract. This was confirmed using CMC-coated coumarin 6 (C6) fluorescence microcapsules. Results: After the oral administration of micro-CMC@LIV, the detection of LMBRaV major capsid protein confirmed effective antigen release and absorption in the midgut and hindgut. Neutralizing antibody titers were significantly higher (1:81.71) in the micro-CMC@LIV group compared to the uncoated vaccine group (1:21.69). The expression of genes linked to the innate and adaptive immune systems was upregulated post-micro-CMC@LIV treatment. Following the LMBRaV challenge, the micro-CMC@LIV group exhibited a relative percent survival (RPS) of 82.14%, significantly higher than the uncoated vaccine group (61.61%). Droplet digital PCR analysis revealed significantly lower viral loads in the liver, spleen, and head kidney of the micro-CMC@LIV group compared to the control group and the uncoated vaccine group. Conclusions: These results collectively suggest that the CMC-coated LIV can be effectively delivered to the intestinal tract and induce robust antibody and immune responses, providing a reliable method for preventing and controlling LMBRaV disease in the largemouth bass industry.

• The MCP of LMBRaV was successfully expressed through Bac-to-Bac baculovirus expression system. • AcMNPV-MCP enhanced the length and weight of largemouth bass. • AcMNPV-MCP can significantly reduce the LMBRaV viral load in the target tissues. • AcMNPV-MCP activated the anti-viral immune responses in largemouth bass.

Chinese rice-field eel rhabdovirus (CrERV), an emerging viral pathogen, causes massive death in rice-field eels (Monopterus albus), thus threatening the industry’s development. There is currently no established treatment strategy for CrERV. This study evaluated the anti-CrERV effects of schisandrin B (Sch B) in vitro and in vivo. The results indicated that Sch B at 20 mg/L could inhibit the expression of the CrERV G protein, with a maximum inhibition rate of 69.5%. Additionally, Sch B mitigated the nuclear damage and mitochondrial membrane potential decline induced by CrERV, thereby preserving cellular morphology. A time-of-addition study suggested that Sch B might exert its antiviral effects during the mid-stage of viral replication. In vivo, Sch B exhibited promising preventive and therapeutic effects against CrERV infection in rice-field eels, enhancing their survival rate by 57% and 51%, when added at 0.075% and 0.025%, respectively. Overall, the natural product Sch B was proven to have excellent anti-CrERV activity, with broad prospects for application in aquaculture.

The Chinese rice-field eel rhabdovirus (CrERV) is an emerging pathogen that causes hemorrhagic disease in Chinese rice-field eels (Monopterus albus), leadi