Infection with the gammaherpesvirus EBV occurs in over 90% of humans and leads to lifelong viral latency with intermittent reactivation that is typically controlled through cell-mediated immunity. However, following transplantation, viral reactivation may be poorly controlled, leading to a spectrum of lymphoproliferative disorders that result in significant morbidity and mortality. While EBV infection is common, the mechanisms by which EBV reactivation post-transplant leads to disease remain unclear. The small animal model, gammaherpesvirus 68, allows in depth analysis of viral pathogenesis. Using this model, we and others have previously demonstrated that a viral cyclin is necessary for viral reactivation and pathogenesis, leading to the hypothesis that other components of the cell cycle such as cyclin-dependent kinases (CDKs) are critical in viral pathogenesis. We make use of a latently infected murine cell line, A20-HE2.1, to evaluate viral reactivation in vitro. Using this cell line, we demonstrate that treatment with a combination of the chemicals phorbol-12-myristate-13-acetate (PMA) and sodium butyrate (NaB) leads to potent induction of viral reactivation, as determined by quantitative PCR for the viral gene gB. By utilizing this system, we can study a number of chemical inhibitors of cyclin-dependent kinases to analyze their effect on viral reactivation. We show that treatment with the specific CDK4/6 inhibitor, PD-0332991, potently reduces viral reactivation, as well as cell proliferation and viability in the A20-HE2.1 cell line. However, PD-0332991 treatment does not appear to reduce global viral gene expression, measured using a viral fluorescence indicator. Work is ongoing in the laboratory to determine the effect of other CDK inhibitors and to determine the impact of PD-0332991 on tumor formation in vivo and on EBV latently infected cells. PD-0332991 is currently in clinical trials as an adjunctive chemotherapy for a number of cancers, including leukemia, lymphoma, multiple myeloma, and breast cancer. Our findings suggests that PD-0332991 may be a useful component of treatment for EBV reactivation following transplantation and for EBV-related lymphoproliferative disorders.

CITATION INFORMATION: Hazleton J., van Dyk L. Use of Cyclin-Dependent Kinase Inhibitors to Reduce Gammaherpesvirus Reactivation Am J Transplant. 2017;17 (suppl 3).

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