Porcine astrovirus (PAstV) is widespread in swine, yet the role of its conserved Stem-Loop II motif (s2m) remains unclear. Using a PAstV-GX1 reverse-genetics system, we engineered s2m deletions and point mutants and assessed replication and innate sensing in PK 15 cells. All mutants were viable and genetically stable. Compared with wild type, s2m-edited viruses showed attenuated early replication and delayed ORF2 accumulation, with growth converging by ~24 h post-infection. Disruption of s2m also advanced innate responses, increasing IFN-β mRNA and promoter activity at 8 h. Preinfection with an s2m mutant transiently restricted heterologous virus replication. These findings indicate that s2m is non-essential but optimizes early kinetics and tempers interferon activation, supporting its consideration as a structurally constrained, potentially targetable RNA element.

To Cite This Article: Luo Y, Liao Y, Zhang W, Du Y, Yi S, Ouyang K, Chen Y, Wei Z, Dong Q, Qin Y and Huang W, 2025. The conserved stem-loop ii motif is not essential but influences replication of porcine astrovirus. Pak Vet J. http://dx.doi.org/10.29261/pakvetj/2025.305