Genome-wide CRISPR screening identifies Annexin A1 as a facilitator of porcine astrovirus entry

Porcine astrovirus (PAstV) is an important and widespread pathogen in swine, linked to diarrheal outbreaks and extraintestinal disease. How PAstV enters host cells has remained unclear, and no cellular factor has been defined for PAstV entry. Here, a genome-wide CRISPR-Cas9 loss-of-function screen in porcine epithelial cells identifies Annexin A1 (ANXA1) as a host factor that facilitates PAstV entry. Genetic ablation or pharmacological/antibody blockade of ANXA1 reduces binding, lowers early viral RNA and capsid signals, and delays the rise of progeny, whereas re-expression restores susceptibility. Biochemical assays and surface plasmon resonance indicate a direct interaction between ANXA1 and the acidic C-terminal domain of the PAstV ORF2 capsid protein, and imaging shows ANXA1 co-localizes with incoming particles at the cell surface and supports attachment and uptake. Loss of ANXA1 does not alter infection by the non-astrovirus panel tested, indicating selectivity for PAstV under our conditions. Notably, infection is reduced but not abolished in ANXA1-deficient cells, consistent with additional entry factors acting alongside ANXA1. These findings position ANXA1 as an entry cofactor for PAstV and provide a mechanistic basis to refine models of astrovirus host-cell recognition.