Role of the Early Association of a mTOR Inhibitor and Tacrolimus in BK Polyomavirus Infection in Kidney Transplant Recipients

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Abstract

Introduction

BK polyomavirus (BKV) replication can be detected in up to 60% of kidney transplant recipients, with an incidence of nephropathy of 5-10%, leading to graft loss in as many as 70% of cases. An early therapeutic intervention, reducing immunosuppression, is key in these cases. mTOR inhibitors (mTOR-I) can play an important role due to their antiviral effect.

Material and Methods

This retrospective study with a longitudinal follow-up included 20 recipients of a kidney transplant between February 2014 and September 2016. After detecting BKV replication the MMF was replaced by an mTOR-I with minimization of tacrolimus. The course of their clinical and laboratory variables was analysed during the follow-up period.

Results

The mean age of the patients was 55±14 years (80% male) and that of the donors was 58±13 years (50% male); 30% had had a previous transplant. All had received triple therapy with tacrolimus, MMF and prednisone; 85% received induction (six patients with anti-CD25 and 11 thymoglobulin). At the time of conversion (17±6 weeks post-transplant), all had BK viruria and 17 also had viremia. A kidney biopsy was done in 14 patients due to suspected nephropathy (BKVN), confirming the diagnosis in 11. The median postconversion follow-up period was 22±6 months. During this period two patients with BKVN lost graft function. The others conserved stable kidney function at 12 months postconversion (baseline MDRDa: 37±12 vs 1 year: 36±18 ml/min; p=0.7). During follow-up the viremia had become negative in 76% of the patients and the viruria in 50%. No adverse effects attributable to the mTOR-I were noted, except for one patient who required withdrawal due to diarrhea. There were one episode of acute rejection.

Conclusions

Early conversion to treatment based on low doses of tacrolimus and a mTOR-I in patients who develop BKV replication is an efficient and safe strategy, providing adequate control of the infection and very good graft survival, even in patients who develop BKVN.

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