|O'Donnell, Vivian -|
|Burrage, Thomas -|
|Jackson, William -|
Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 29, 2010
Publication Date: November 26, 2010
Citation: O'Donnell, V., Pacheco Tobin, J., Larocco, M.A., Burrage, T., Jackson, W., Rodriguez, L.L., Borca, M.V., Baxt, B. 2010. Foot-and-mouth disease virus utilizes an autophagic pathway during viral replication. Virology. 410:142-150. Interpretive Summary: Foot-and-mouth disease (FMD) is a highly contagious viral disease of cloven-hoofed livestock caused by foot-and-mouth disease virus (FMDV), which results in large economic losses to countries where it occurs. It has been shown that after initiation of picornavirus infection, a number of changes take place in the cell, which includes the rearrangement of intracellular membranes into vesicular structures where viral genome replication takes place. Characterization of these double membrane vesicular structures suggests an autophagic origin. Autophagy is a cell regulated pathway designed to degrade and recycle long-lived proteins and cellular components, which are important in organelle turnover and management of starvation. Recent studies have shown that a number of positive-strand RNA viruses, including picornaviruses, induce the formation of autophagic membranes. In this study, we determine the role of autophagy in FMDV replication by using confocal microsopy and monitoring the co-localization of specific autophagosome and viral proteins in infected cells. To extend our studies, we explore the effect of biochemical compounds that inhibit or induce autophagy, and RNA interference, on FMDV replication. Our results suggest that, although autophagy has both antiviral and antibacterial functions, it appears to play an important role in the replication of FMDV. Understanding better the mechanisms that are involved during viral replication, let us examine the role of drugs which inhibit these processes as possible anti-viral agents.
Technical Abstract: Foot-and-mouth disease virus (FMDV) is the type species of the Aphthovirus genus, of the family Picornaviridae. Infection of cells with positive-strand RNA viruses results in a rearrangement of intracellular membranes into viral replication complexes. However, the origin of these membranes remains unknown; the induction of the cellular process of autophagy, in which a portion of the cytoplasm is sequestered within double-membrane vesicles, called autophagosomes, and then mature to degrade their cytoplasmic contents, has been shown to be beneficial for the replication of poliovirus, and might also apply for other picornaviruses. To determine if autophagy plays a role during FMDV replication, we analyzed the localization of hallmarks of the cellular autophagic pathway with different viral proteins by using confocal microscopy. Here, we show that non-structural viral proteins, 2B, 2C and 3A, colocalize with the autophagosome marker microtubule-associated protein light-chain kinase 3 (LC3). A colocalization of LC3 with the lysosomal membrane protein 1 (LAMP-1), characteristic of autophagosome formation, was also observed in FMDV infected cells. Stimulation of autophagy by rapamycin, resulted in an increase in FMD viral yield which was manifest to a greater degree in extracellular virus. Moreover, inhibition of autophagy by 3-methyladenine or by small-interfering RNA targeting mRNAs that encoded two proteins known to be required for autophagy (LC3 and the Autophagy-related protein 12, ATG12), decreased FMD viral replication. These studies suggest that, although autophagy has both antiviral and antibacterial functions, it may play an important role during FMDV replication. Moreover, autophagy may represent a possible mechanism for the virus to maintain the “carrier state” and, under certain circumstances, possibly enable the non-lytic release of the virion from persistently infected cells.