Residue 188 of the Hexon protein governs FAdV-4 pathogenicity by activating PINK1/Parkin-mediated mitophagy.

Fowl adenovirus serotype 4 (FAdV-4) infection causes significant economic losses to the global poultry industry. Viruses often hijack host cellular machinery to facilitate their replication; however, the mechanisms by which FAdV-4 manipulates host pathways remain poorly defined. Mitochondria, the central hubs for energy metabolism and innate immunity in hepatocytes and cardiomyocytes, are critical targets for viral manipulation, yet their role in FAdV-4 pathogenesis remains unexplored. Here, we demonstrated that FAdV-4 infection caused direct mitochondrial damage and induced PINK1/Parkin-dependent mitophagy both in vitro and in vivo. Moreover, the virus actively hijacked the PINK1/Parkin-mediated mitophagy to enhance viral replication in LMH cells. Inhibition of mitophagy led to an average tenfold reduction in viral replication of pathogenic FAdV-4 in LMH cells (p < 0.05). Strikingly, residue 188 in the Hexon protein, a key virulence determinant, differentially regulated mitophagy: the R188I mutation in the pathogenic FAdV-4 attenuated mitophagy, whereas the I188R mutation in nonpathogenic FAdV-4 enhanced this process. This study elucidated the viral exploitation of mitophagy by FAdV-4 to promote viral replication, and established Hexon residue 188 and the mitophagy pathway as prime targets for developing novel therapeutics against avian adenoviral diseases.