Introduction: BK virus continues to be a significant post-transplant complication with increasing incidence in the current era of potent immunosuppression. Mammalian target of rapamycin inhibitors (mTORi) have been reported to have antiviral effect in vitro and reduced incidence of BK viremia in clinical studies. Our center uses mTORi based immunosuppression in combination with calcinurine inhibitors (CNI) or antimetabolites for maintenance immunosuppression post-transplantation. We aimed to study the incidence of Bk viremia in patients who were on mTORI based therapy during the first year post transplant vs patients who were not. Methods: A retrospective analysis of BK viremia defined at blood pcr >500 copies/ml in 1127 patients who received a kidney transplant from a living or deceased donor between January of 2010 and December of 2015. Patients received induction therapy with thymoglobulin and rapid steroid taper followed by maintenance immunosuppression therapy with either mTORi based therapy (everolimus or sirolimus + cyclosporine or antimetabolites) or CNI only based therapy (cyclosporine + antimetabolites). Results: BK viremia occurred in 209 (18.5%) patients. There were no difference in the occurrence of Bk viremia between patients on mTORi based therapy vs patients on CNI based therapy (18.4 vs 19.5%, P= 0.157). Patient's age, BMI, delayed graft function, and ureteral stent placement were not associated with increased risk for Bk infection (P>0.5). Conclusion: Antiviral activity of mTORi in vitro does not seem to translate into a protective effect against BK infection in clinical practice. The risk of BK infection is most importantly related to the overall degree of immunosuppression rather than the individual choice of immunosuppression therapy.

CITATION INFORMATION: Daloul R., Pelletier R., Rajab A., Bumgardner G., Alebrahim M., Akateh C., Washburn K., El-Hinnawi A. mTOR Inhibitor Based Immunosuppression Regimens Are Not Associated with Lower Risk for BK Infection Am J Transplant. 2017;17 (suppl 3).

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