The search for novel antiviral compounds to prevent or mitigate the losses caused by viral infectious diseases is of great importance since they cause high economic losses in the aquaculture sector . In this work, we evaluated in vivo the antiviral activity of five plant extracts encapsulated in chitosan and administered in the fish feed : Vitis vinifera, Camelia sinensis, Rosmarinus officinalis, Glycyrrhiza glabra and Punica Granatum . These plant extracts have previously shown antiviral activity in vitro against nervous necrosis virus (NNV). This virus affects a large number of wild and farmed fish species and is distributed globally . The disease caused by this virus, the viral nervous necrosis (VNN), is considered a worldwide and disastrous disease that could be classified as one of the most important diseases in marine fish, specially for sea bass (Dicentrarchus labrax) fish farming. In this study, t he therapeutic and prophylactic activity of five plants extracts (encapsulated in chitosan and formulated in the feed) was evaluated in vivo. S ea bass of 5-6 gr were fed with the plant extracts supplemented feeds for up to 10 days and intestine, head kidney, red blood cells (RBCs) and spleen were collected at 3 and 10 days of feeding. We evaluated the impact of in-feed plant extracts on fish health by means of blood biochemistry and hematological analyses. We evaluated the plasma-based biochemical parameters, including plasma proteins (total protein, albumin, globulin, creatine kinase , aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, amylase, and lactate dehydrogenase), plasma metabolites (creatinine, urea, glucose, cholesterol , triglycerides, bicarbonate, bilirubin, and lipopolisacaride ), and plasma ions (Calcium and phosphorus). As well, w e evaluated the hematological parameters, including leukocyte parameters (white blood cells, lymphocytes, neutrophils, monocytes, eosinophils, basophils, and platelets), and erythrocyte parameters (RBCs, haemoglobin, haematocrit, mean corpuscular volume, mean corpuscular haemoglobin). The immune response induced by the plant extracts supplemented feeds was evaluated by means of RT-qPCR and RNA-sequencing . Finally, we evaluated the protection conferred by the plant extracts supplemented feeds against red-spotted grouper nervous necrosis virus (RGNNV) challenge.
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.