Effect of Thymoglobulin on the Development of BK Virus Viruria and Viremia in Renal Transplant Recipients: A Case-Control Study

Purpose: BK virus infection is an emerging complication in renal transplant recipients. Viruria or viremia can precede BK nephropathy, which can contribute to graft loss. Studies have described a relationship between immunosuppressive therapy and BK virus reactivation. The purpose of this study is to determine risk factors for the development of BK virus infection in renal transplant recipients over a 12 month period. We hypothesize that larger doses of thymoglobulin (>5mg/kg) will increase the incidence of BK virus infection in renal transplant recipients.

Methods: A retrospective, single center, unmatched case-control study. Patients included were >18 years of age, received a renal transplant at our institution from 2007-2010, received rabbit-derived thymoglobulin for induction therapy with frequent monitoring of BK virus available. Data collected included: maintenance immunosuppression and drug concentrations, time to BK virus detection, renal function measurements, biopsy results, and BK virus infection treatment.

Results: Seventy seven met inclusion criteria for the study. Patients that received a high dose of thymoglobulin (>5mg/kg) during induction therapy, had a 10% lower odds of developing BK virus infection compared to patients that received a low thymoglobulin dose (OR 0.90 95% 0.29-2.79). The incidence of BK nephropathy was 4 of 307 (1.3%) and zero progressed to graft loss over the study period. Treatment of BK virus infection was frequently not documented (67.6%); discontinuation of mycophenolate mofetil (20.5%); reduction in total immunosuppressive therapy (8.8%); and leflunomide treatment (5.8%).

Conclusions: Our study demonstrated no single risk factor for the development of BK virus viruria/viremia 12 months post renal transplantation. The incidence of BK virus was 11%, BK nephropathy was 1.3%, and graft loss due to BK nephropathy was 0%. Larger studies must be performed to determine if the total thymoglobulin dose for induction therapy is a risk factor for the development of BK virus infection.