Background

BK virus (BKV) is a common infection in simultaneous pancreas-kidney (SPK) transplant recipients. Data in kidney transplant recipients suggest that immunosuppression regimens containing an mTORi are associated with a reduced risk of BK viremia but this observation has not been evaluated in SPK recipients.

Methods

Retrospective single center study of incident BK viremia during the first 24-months post-SPK in recipients who received Thymoglobulin induction and were maintained on tacrolimus and MPA with or without the addition of sirolimus (for steroid minimization) at 2-4 weeks post-transplant. BKV screening via urine PCR occurred at months 3, 6, 12, and 24. A result of >100K copies/mL prompted testing for viremia via blood PCR as well as continued blood PCR monitoring. Evalution of the impact on BK viremia risk in patients treated with sirolimus was determined by a univariate Cox proportional hazards model.

Results

27 patients developed BK viremia on an average POD of 484.4 while 98 did not develop viremia. There were no differences in baseline patient characteristics between the two groups. There was no significant difference in the use of maintenance prednisone between those with and without BK viremia at 63% and 46%, respectively (P=0.13). There was a higher mean MPA dose at month 3 in those with BK viremia but a higher mean MPA dose at month 24 in those without BK viremia. There were no differences in tacrolimus troughs at any time point and there was no difference in sirolimus use in viremic vs non-viremic patients (70.4% vs 64.3%; P=0.65). Sirolimus was added on a mean POD of 28.8 and 23 in those with and without viremia, respectively (P=0.23) and troughs were similar between the groups during the two year follow-up. The addition of sirolimus did not impact the risk of BK viremia with a HR of 0.81 (CI 0.35-1.9; P=0.61).

Conclusion

Early post-transplant addition of sirolimus to maintenance immunosuppression is not associated with a reduced risk of BK viremia in SPK recipients. The increase in overall burden of immunosuppression caused by the addition of sirolimus may outweigh any potential anti-BKV activity. Prospective studies are warranted to further evaluate this observation.

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