Increasing Net Immunosuppression after BK Polyoma Virus Infection

BACKGROUND Reducing immunosuppression can effectively treat BK viremia (BKV) and BK nephropathy, but has been associated with increased risks for acute rejection and development of donor specific antibodies (DSA). To date there have been no systematic evaluations of re-escalating immunosuppression in transplant patients with resolving BKV. Importantly, the safety of this approach and impact on graft survival is unclear. METHODS We performed a single center retrospective review of kidney transplant recipients between July 2011 and June 2013 who had immunosuppression reduction after developing BKV (plasma PCR ≥1,000 copies/mL). Changes in immunosuppression and patient outcomes were tracked until occurrence of a complication event: biopsy-proven acute rejection (BPAR), detection of de novo DSA, or recurrent BKV. Patients were grouped according to whether or not net immunosuppression was eventually increased. RESULTS Out of 88 patients with BKV, 44 (50%) had net immunosuppression increased while the other 44 did not. Duration of viremia, peak viremia, induction and sensitization status were similar between the two groups. In a Kaplan-Meier analysis, increasing immunosuppression was associated with less BPAR (p=0.001) and a trend towards less de novo DSA development (p=0.06). Death-censored graft survival (p=0.27) was not different between the two groups. In the net immunosuppression increase group, recurrent BKV occurred in 22.7% without any BKV-related graft losses. CONCLUSION These findings support potential benefits of increasing immunosuppression in patients with low-level or resolved BKV, but prospective trials are needed to better understand such an approach.