Inhibition of red seabream iridovirus (RSIV) replication by small interfering RNA (siRNA) in a cell culture system.

Small interfering RNAs (siRNAs), mediators of a process of sequence-specific gene silencing called RNA interference, have been shown to have activity against a wide range of viruses and are considered to be potential antiviral tools. Here, we describe an antiviral activity of a siRNA that targets the major capsid protein (MCP) gene of red seabream iridovirus (RSIV), a marine fish-pathogenic virus, in a cell culture system. Inhibition of RSIV replication was demonstrated by reduced MCP expression level and reduced RSIV titer. MCP-targeted siRNA (siR-MCP) dose-dependently inhibited the expression of MCP gene in cells that either transiently expressed or stably expressed the MCP gene. At 84 and 96h after viral infection, siR-MCP reduced the expression of MCP gene by 55.2% and 97.1%, respectively. Transfection with siR-MCP reduced the production of RSIV particles in supernatants of samples infected with RSIV, while the corresponding mismatched siR-MCP (MsiR-MCP) and nsRNA controls did not exhibit this effect. These results show that MCP-targeted siRNA can effectively and specifically inhibit the expression of the target gene and hinder RSIV replication during an in vitro infection, providing a potential approach for the control of viral diseases in aquaculture.