Antiviral treatment of BK polyomavirus reactivation

项目总结

Project Summary BK polyomavirus (BKPyV) associated nephropathy (PVAN) is the leading cause of kidney transplant loss (~10%/year). BKPyV infects approximately 80-90% of people during childhood and is kept in check by the host immune system. However, in transplant patients BKPyV reactivation causes PVAN due to suppression of their immune system. The current treatment is reduction of immunosuppression, which increases the risk of graft rejection, but untreated PVAN will result in allograft loss. Patients are routinely monitored for BKPyV in the urine and the plasma, providing an opportunity to treat early with antivirals, before decreasing immunosuppression is required. Based on our mechanistic studies, we have identified two host pathways required for BKPyV production in primary kidney cells that, when inhibited by existing drugs, reduce viral titers. We discovered that bortezomib, a proteasome inhibitor, potently decreases viral titers by 3 logs, at low doses and without affecting cell fitness. We will also test newer generation proteasome inhibitors that are less toxic and/or orally available, carfilzomib and ixazomib. Given that the proteasome is required early during infection, we sought to inhibit a second host target that would reduce viral production late in infection, or could potentially eliminate virally infected cells. BKPyV requires activation of the DNA damage response (DDR) for cell cycle arrest, to prolong S phase for viral replication and assembly. Inhibiting the DDR activating kinases (ATM and ATR), forces BKPyV infected, but not mock infected, cells exit S phase, and viral titers are reduced. Our studies revealed two potent targets, the proteasome and the DDR, which both have known inhibitors, one is already FDA approved, and the other is in clinical trials (both are being used for other indications). The proposed aims will determine the effects of these inhibitors, and combinations of them, on viral titers, cell viability and cell cycle regulation, using clinical viral isolates to infect primary renal proximal tubular epithelial cells, which are the natural cell type infected in humans. We will sequence the virus before and after inhibition studies to determine if there are changes to the viral genome. This proof-of-concept data is required in order to test the inhibitor(s) in clinical trials (beyond the scope of this study) as antivirals that can protect against graft loss caused by BKPyV reactivation. There is an urgent need for antivirals that can either prevent or treat BKPyV reactivation prior to or in conjunction with immunosuppression.