Abstract

Sulfated polysaccharide lambda carrageenan (?-CGN) was evaluated for its antiviral effect against IPNV using the in vitro infection model of CHSE-214 salmonid cells. A plaque reduction lysis assay revealed that ?-CGN has an IC50 of 0.9 ?g?mL?1, CC50 > 128 ?g?mL?1 and a Selectivity Index (SI) > 142. In comparison, iota, kappa carrageenans and lambda oligo-carrageenan (?-OC) were less effective than ?-CGN against IPNV. ?-CGN showed no virucidal activity when applied directly to viral particles. Time of addition experiments showed that pre-treatment, co-treatment, and post-treatment with ?-CGN significantly reduced viral RNA copies in the cell supernatant. Additionally, a decrease in intracellular viral RNA was observed with pre-treatment and post-treatment, indicating an impact on different stages of viral replication. Polyacrylamide gel electrophoresis of IPNV genomic RNA in presence of ?-CGN showed a reduction in the level of viral genomic RNA. Confocal microscopy confirmed the intracellular localization of ?-CGN, suggesting that ?-CGN may inhibit the synthesis of IPNV genomic RNA. Moreover, cells pre-treated with ?-CGN showed an increased expression of innate immunity genes CXCL11, IL1?, IFNa, and IRF3. These findings highlight the need for further research to confirm the in vivo pharmacological potential of ?-CGN as a new antiviral agent in salmonids. © 2024