To identify the key molecules involved in ALOX15-mediated K63-linked ubiquitination of MAVS, we performed LC-MS/MS-based proteomics analysis of MAVS-interacting proteins in H1N1-infected A549 cells transfected with Flag-ALOX15 or plasmid vector. This analysis identified USP19, a deubiquitinase, as a potential candidate, as its interaction with MAVS was significantly reduced in ALOX15-overexpressing cells. This suggests that ALOX15 and USP19 might compete for binding to MAVS.