ATG9A is an essential host factor for parechovirus RNA replication

ABSTRACT Parechoviruses (PeVs) are single-stranded, positive-sense RNA viruses in the Picornaviridae family. Although most genotypes are not typically associated with severe disease, PeV-A3 has emerged as an important cause of sepsis and meningoencephalitis in newborns. Despite its clinical relevance, the life cycle and pathogenesis of PeV-A3 remain poorly understood. To identify critical host factors for PeV-A3 replication, we performed a genome-wide CRISPR screen. Our results reveal a set of Golgi-localized proteins important for viral infection, among which the lipid scramblase ATG9A (autophagy-related protein 9A) was determined to be essential across different PeV genotypes. Notably, this requirement appears to be independent of canonical autophagy. We further demonstrate that ATG9A is necessary for viral RNA replication, but not entry or translation, and co-localizes with double-stranded RNA, a marker of viral replication organelles (ROs) during infection. ATG2, a lipid transfer protein known to interact with ATG9A, is also required for optimal viral replication. Therefore, the ATG2-ATG9A complex may function by delivering key lipids into the ROs to support viral replication. IMPORTANCE Parechovirus (PeV) is a widespread but understudied human pathogen capable of causing severe neurologic disease and sepsis in neonates and infants. Through a CRISPR-based screen, we identified key host factors required for PeV-A3 infection and uncovered a novel, critical role of ATG9A in viral RNA replication that is independent of canonical autophagy. These findings provide new insight into the molecular pathogenesis of the virus and establish a foundation for future antiviral therapeutic development.