Differential Effects Of The NS5A Proteins From Highly Virulent Strain And C-Strain On The Replication Efficiency Of Classical Swine Fever Virus

Classical swine fever virus(CSFV) is the causative agent of Classical swine fever(CSF), which leads to huge economic losses. CSF has been listed as one of the major animal epidem ics in our country and has been also listed as one of five prior ity prevention animal diseases by the National Long- and Middle-Term Animal Disease Control Plan for 2012—2020. Currently, hog cholera lapinized virus(HCLV or C-strain) is the most effective for CSF prevention and control, which induces fever response in rabbits and is able to replicate in rabbits spleen and lymph nodes.The NS5 A protein of CSFV, a component of the viral RNA replication complex, is involved in the replication of the viral genome. In addition, NS5 A also interacts with its host to regulate the viral genome replication. Surprisingly, we found that the NS5 A proteins from Shimen strain and HCLV strain were different in molecular weight by Western blotting in a previous study. Therefore, we are wondering whether the NS5 A proteins from Shimen strain and HCLV strain could affect the replication efficiency of CSFV.We constructed a chemic reporter virus expressing Renilla luciferase(Rluc)(r SM-Rluc-HCLVNS5A) and confirmed that NS5 A proteins had an impact on the CSFV replication efficiency by Rluc assay. Subsequently, we constructed the chemic viruses harboring the exchanged NS5 A based on the backbone of Shimen strain and HCLV, respectively. We found that the replacement with HCLV NS5 A encoding sequences based on Shimen strain(r SM-HCLVNS5A) impaired the replication efficiency by detecting virus titer and quantitative real-t ime PCR. Similarly, the replication efficiency from the replacement with Shimen strain NS5 A in the context of HCLV(r HCLV-SMNS5A) was signif icantly enhanced. Finally, we carried out experiments in rabbits and found that r HCLV-SMNS5 A still induced fever response, replicated in rabbit spleens, as well as retained the immunogenicity of HCLV.Our results showed that the NS5 A proteins from resulted in different in vitro replicat ion levels of CSFV, but did not change the adaptation of HCLV to the rabbit and did not affect the replication efficiency of HCLV in rabbits. This study provides insights on the attenuation of HCLV.