Coxsackievirus B3 (CVB3), an enterovirus in the picornavirus family, is a frequent infectious cause of pancreatitis, a common, serious, and costly disease. Some forms of pancreatitis are known to involve the autophagy pathway; e.g., toxins that block late steps in the pathway can trigger the disease, perhaps because the blockade causes activation of intracellular trypsinogen. Paradoxically, complete inactivation of autophagy protects against those types of pancreatitis. Therefore, at least those forms of pancreatitis require that the pathway be both (i) active and (ii) blocked at a late stage. Autophagy is upregulated during, and often combats, many viral and bacterial infections. Predictably, evolution has led to several viruses developing mechanisms by which to evade the inhibitory effects of the pathway, and studies have suggested that some viruses - including CVB3 - have gone one step further, actively exploiting autophagy to enhance their replication. My lab has shown that, in acinar cells in vivo, CVB3 interrupts a late stage of the autophagy pathway. We therefore hypothesized that there might be a link between this effect of CVB3 on the autophagy pathway, and the virus' ability to cause pancreatitis. We wished to test this idea in vivo, (i.e., n the living animal, not only in tissue culture cells). To achieve this goal, we have recently developed conditional KO mice (Atg5f/f/Cre+ mice) in which a key protein in the autophagy pathway, Atg5, has been deleted only in pancreatic acinar cells. Using these mice, we have shown that CVB3 benefits from an intact autophagy pathway without which CVB3 replication in the pancreas is severely curtailed. Furthermore, virus-induced pancreatitis is dramatically reduced in the Atg5f/f/Cre+ mice. Thus, like some other types of pancreatitis, CVB pancreatitis requires that autophagy be active (as it is in wt mice), but dysfunctional (because the virus blocks the pathway). Furthermore, our unpublished data show that CVB3 infection induces autophagy-dependent trypsin activity inside acinar cells. These and other data lead me to propose that there is a common cause for all pancreatitides, viral and non- viral; I propose that they result from a late blockade of the autophagy pathway, which leads to cleavage of intracellular trypsinogen, unleashing trypsin activity inside the cell. These issues will be investigated in Aims 1 & 2. I further hypothesize that the trypsin-initiated damage can be exacerbated by T1IFN signaling into acinar cells; this will be investigated in Aim 3. If these concepts are validated, autophagy and T1IFNs would become key therapeutic targets for all forms of this currently-untreatable disease. There are three Specific Aims.
Aim 1. To better define interactions among CVB3, autophagy, and trypsinogen in acinar cells in vivo.
Aim 2. To evaluate how T1IFN signaling directly into acinar cells affects viral pancreatitis.
Aim 3. To evaluate the role of T1IFNs in recruiting immune cells to the virus-infected pancreas.
Pancreatitis (inflammation of the pancreas) affects more than 200,000 Americans each year, and costs the USA more than $2 billion. This grant is aimed at understanding how viral pancreatitis develops, and identifying potential therapies for this currently-untreatable disease.
|Alirezaei, Mehrdad; Flynn, Claudia T; Wood, Malcolm R et al. (2015) Coxsackievirus can exploit LC3 in both autophagy-dependent and -independent manners in vivo. Autophagy 11:1389-407|