Largemouth bass ranavirus (LMBRaV), also known as largemouth bass virus (LMBV), is a highly damaging viral pathogen that causes widespread mortality in cultured largemouth bass and poses a significant threat to the farming industry in China. However, there is a paucity of effective preventive methods for this disease by LMBRaV. Research has established that herbal extracts possess antiviral activity, potentially exerting a controlling effect on viruses in aquaculture. Therefore, the identification of simple and structurally safe herbal extract immunomodulators is critical for largemouth bass health and development. Rhein, an herbal compound, exhibits a broad spectrum of pharmacological effects in herbal medicine. This study aimed to evaluate the properties and effects of rhein against LMBRaV in epithelioma papilloma cyprinid (EPC) and largemouth bass. In vitro CCK-8 assays were performed to determine the highest safe concentrations. Significantly, 50 mg/L rhein effectively inhibited cytopathic effects (CPE) in EPC induced by LMBRaV, resulting in a 97 % reduction in viral replication rates. Furthermore, a six-point dose-response experiment revealed that rhein doses as low as 6.4 mg/L inhibited LMBRaV and suppressed LMBRaV infection with a dose-dependent manner. Subsequent experiments demonstrated that sustained rhein activity effectively alleviated CPE and nuclear damage caused by LMBRaV infection. Additionally, rhein exerted protective effects against declines in LMBRaV-induced mitochondrial membrane potential. In vivo experiments validated that largemouth bass diets supplemented with 0.075 % rhein exerted a protective effect against LMBRaV infection. Moreover, LMBRaV MCP gene expression levels were lower in several organs of fish in the rhein supplementation group. Immunogene analysis determined that rhein upregulated relevant gene expression levels in multiple organs of largemouth bass, with higher activities observed for the Mx, INF-γ, and IRF3 genes. Histopathological results displayed that a supplemental dosage of 0.075 % rhein significantly mitigated LMBRaV infection-induced pathological damage in the liver, spleen, and kidney. Taken together, these in vivo and in vitro results support the effective use of rhein as a promising candidate for the development of antiviral treatment against LMBRaV infection, highlighting its role in aquatic animal husbandry as a wide-spectrum antiviral and immune response booster.

Mengmeng Chen

Mingyang Xue

Yong Zhou

Chen Xu

Nan Jiang

Yuding Fan

Yan Meng

Fish & Shellfish Immunology

Fish and Shellfish Immunology rapidly publishes high-quality, peer-refereed contributions in the expanding fields of fish and shellfish immunology. It presents studies on the basic mechanisms of both the specific and non-specific defense systems, the cells, tissues, and humoral factors involved, their dependence on environmental and intrinsic factors, response to pathogens, response to vaccination, and applied studies on the development of specific vaccines for use in the aquaculture industry.

The journal "Fish and Shellfish Immunology" rapidly publishes high-quality, peer-reviewed contributions in the expanding fields of fish and shellfish immunology. It presents studies on the basic mechanisms of both specific and non-specific defense systems, the cells, tissues, and humoral factors involved, their dependence on environmental and intrinsic factors, responses to pathogens, responses to vaccination, and applied studies on the development of specific vaccines for use in the aquaculture industry.

《Fish and Shellfish Immunology》期刊快速发表高质量、经过同行评审的研究成果，涵盖鱼类和贝类免疫学的广泛领域。期刊内容包括对特异性和非特异性防御系统基本机制的研究，涉及相关细胞、组织和体液因子，以及它们对环境和内在因素的依赖性、对病原体的反应、对疫苗的反应，以及针对水产养殖行业特定疫苗开发的应用研究。

Category	Quartile
农林科学	2
农林科学, 渔业	1
农林科学, 海洋与淡水生物学	1
农林科学, 兽医学	1
农林科学, 免疫学	3

Antiviral effects of rhein on largemouth bass ranavirus (LMBRaV)

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Journal Info

Category	Quartile
VETERINARY SCIENCES	1