In aquaculture, viruses are one of the major concern related to infectious diseases, since they cause high economic losses. Therefore, the search for new antiviral compounds to prevent or mitigate these losses is of great importance. In this work, we evaluated the antiviral activity of four plant extracts: Vitis vinifera, Rosmarinus officinalis, Glycyrrhiza glabra and Punica Granatum, to search for new antiviral compounds, since the use of plant extracts as antimicrobials is known to have certain benefits, for example, they do not contaminate the aquatic environment and generally do not produce viral resistance. Therefore, we evaluated the antiviral activity of these plant extracts against red spotted grouper nervous necrosis virus (RGNNV). This virus is one of the most important viruses in aquaculture, as it affects a large number of wild and farmed fish species and is distributed globally.
This work was carried out using the E-11 cell line (clone of SNN-1 (striped snakehead whole fry cells)), since it is a cell line highly susceptible to RGNNV. As mentioned above, Vitis vinifera, Rosmarinus officinalis, Glycyrrhiza glabra and Punica Granatum plant extracts were chosen because of their potential antiviral capacity. For that, the working concentrations of the extracts were determined by a cytotoxicity assay. Then, the evaluation of the antiviral activity was performed as follows. First, the antiviral capacity of the plant extracts was evaluated by pretreating the cell monolayer with the extracts 24 hours prior to infection. Second, the virucidal capacity of the extracts was evaluated by pretreating the virus for 2 hours before infection. Finally, the antiviral activity of the extracts was evaluated by treating the cells during the course of infection, 2 hours after infection. The viral load was analyzed by RT-qPCR by means of the expression of RGNNV polymerase (RdRP). The results obtained showed the high antiviral activity of the plant extracts, some of them reducing up to 90% the expression of RdRP. These results demonstrated the potential of these extracts as antivirals against RGNNV. The final aim of this work will be to include these extracts in animal feed to reduce or mitigate the effect of this virus in aquaculture.
Acknowledgements: This study was funded by ThinkInAzul programme, GVA-THINKINAZUL/2021/020, supported by MCIN with funding from European Union NextGenerationEU (PRTR-C17.1) and by Generalitat Valenciana.