# 3A and 2B proteins of SVA play chess game with host restriction factor DDX23 by apoptotic pathway

## TL;DR

This study reveals how DDX23 restricts SVA replication and how SVA evades this defense, offering new targets for antiviral treatments and vaccines.

## Contribution

First study to elucidate dual mechanisms of DDX23 inhibition and SVA evasion via specific amino acid residues.

## Key findings

- DDX23 inhibits SVA replication by degrading the SVA-3A protein through the Caspase-2/-6 pathway.
- SVA-2B residues W44 and P45 reduce DDX23 protein levels via the Caspase-2/-3 pathway.
- Key amino acids K14 of SVA-3A and W44/P45 of SVA-2B regulate viral activity and host evasion.

## Abstract

Senecavirus A (SVA) is an emerging porcine pathogen that poses a significant threat to the global swine industry and has become an obstacle to its sustainable development. DEAD-box helicase 23 (DDX23), an RNA helicase, is increasingly recognized for its critical role in host antiviral defense mechanisms. However, the precise function of DDX23 in SVA infection remains unclear. In this study, we demonstrated through overexpression and knockout experiments that DDX23 inhibits SVA activity. Notably, compared to uninfected controls, SVA-infected BHK-21 cells exhibited a significant increase in DDX23 transcription levels but a decrease in DDX23 protein levels. Further co-transfection and inhibitor experiments revealed that DDX23 specifically targets leucine 14 (L14) of the SVA-3A protein and degrades SVA-3A protein via the Caspase-2/-6 pathway, thereby suppressing viral replication. Additionally, we identified that tryptophan (W44) and proline (P45) residues at positions 44 and 45 of SVA-2B are critical sites responsible for the reduced expression of DDX23 protein. This occurs through the Caspase-2/-3 pathway, leading to DDX23 degradation. Using reverse genetics, we constructed recombinant viruses and confirmed that K14 of SVA-3A and W44/P45 of SVA-2B are key regulatory amino acids for viral activity. These findings provide new insights into the mechanism by which DDX23 restricts SVA replication and how SVA evades host antiviral defenses, offering potential targets for future antiviral drug development and vaccine design.

The emergence and spread of Senecavirus A (SVA) have affected the healthy development of the global pig industry. In order to develop the pig industry, it is needed to explore the pathogenic mechanism of SVA and the strategies to evade the host antiviral defense. Our study is the first to elucidate the dual mechanisms by which DEAD-box helicase 23 (DDX23) inhibits SVA replication and how SVA counteracts DDX23 to promote its proliferation. By identifying key amino acid residues involved in these interactions, our findings provide a foundation for the development of targeted antiviral therapies and vaccines against SVA. These results have important practical value in alleviating the pressure of SVA on the economic and health development of the pig industry.