Irreversible inactivation of ISG15 by a viral leader protease enables alternative infection detection strategies

Swatek, Kirby N.; Aumayr, Martina; Pruneda, Jonathan N.; Visser, Linda J.; Berryman, Stephen; Kueck, Anja F.; Geurink, Paul P.; Ovaa, Huib; van Kuppeveld, Frank J. M.; Tuthill, Tobias J.; Skern, Tim; Komander, David

Importantly, Lb pro activity can also be visualized during FMDV infection [e.g., using baby hamster kidney (BHK) cells transfected with FLAG-tagged ISG15 and the ISG15 conjugation system]. Before infection, transfection leads to robust FLAG signals, whereas anti-GlyGly signals are absent. FMDV infection induces collapsing of FLAG signals coinciding with the appearance of GlyGly-modified proteins. Within 4 h of FMDV infection, the anti-GlyGly antibody labels hundreds of proteins across a broad molecular weight range (Fig. 4C) . We are not aware of a similar host cell-derived viralinduced epitope that is detectable with such relative ease. Importantly, this epitope originates from host proteins and cannot acquire mutations due to viral evolution.