Emodin modulates the host antiviral response of fish against spring viremia of carp virus infection

As a natural small molecule monomer widely found in various traditional Chinese herbs, emodin has garnered substantial attention due to its pharmacological properties. Its widespread exploration for application such as growth enhancement, immune modulation, and antimicrobial activity in aquaculture. In the present study, our focus centers on investigate the anti-spring viremia of carp virus (SVCV) activity of emodin, thereby facilitate the development of commercially viable methods for the prevention and treatment of SVCV infection. We assessed the inhibitory effects of emodin against SVCV through both in vitro and in vivo paradigms. In the in vitro assay, cells were firstly infected with emodin mixed with SVCV to impact of emodin on viral replication, apoptosis, and mitochondrial depolarization. Notably, the results underscore that emodin, at a concentration of 16 μM, engenders a remarkable 99.99% suppression of SVCV infection. Interestedly, it distinctly influences the internalization of viral particles into the cells as well as modulate the antiviral response. Furthermore, in the in vivo assay, zebrafish (Danio rerio) fed with an emodin-supplemented commercial diet exhibited a notably elevated survival rate, surpassing that SVCV-exposed group which fed with only commercial diet (up to 22%), a significant reduction in viral load in host was also discerned. Emodin supplementation elicited substantial upregulation of host antiviral related genes, such as interferon-φ (IFN-φ), retinoic acid inducible gene I (RIG-I), and IFN-stimulated gene product 15 (ISG15), by 4.98-, 3.97-, and 7.42-fold on day 7, respectively. In summation, our results indicate that emodin has anti-SVCV activity, and the confluence of emodin's well-established extraction protocol, environmental friendliness, and multiple bioactivities collectively predict it has the potential for commercial application as an antiviral disease additive in aquaculture.