Quantification of BK Viral Load in Asymptomatic Renal Allograft Recipients

Abstract

Introduction: Polyoma BK virus (BKV) has recently been identified to cause renal allograft dysfunction, which manifests as polyomavirus-associated nephropathy (PVAN). However, the presence and level of BKV DNA in renal allograft patients with good and stable renal function have remained undetermined. Methods: In this prospective study, serum samples were collected from a total of 45 renal allograft recipients with serum creatinine <155 μmol/L. In 17 patients, whose duration of transplantation was under 2 years, samples were collected at 3–4-month intervals for up to 2 years after transplantation. BK viral load was quantified using quantitative polymerase chain reaction (Q-PCR). Results: The BK viral load in asymptomatic renal allograft recipients was independent of the duration of transplantation and did not correlate with allograft function. The mean (± SD) level of viremia was 552.80 ± 1931.00 genome copies/mL, with 92.9% of patients having low levels of viremia corresponding to <1 × 10³ copies/mL. In contrast, patients with proven PVAN had levels in the range of 10⁶ copies/mL. Conclusions: The prevailing BK viral load in asymptomatic renal allograft patients is quantifiably low. Our findings may guide optimal immunosuppressive modulation in PVAN cases, where judicious manipulation of immunosuppression is required without inciting allograft rejection.

• polyoma BK virus
• renal transplantation
• quantitative PCR
• immunosuppression
• nephropathy

ACKNOWLEDGMENTS

This study was supported by the S.K. Yee Medical Foundation. Part of the data contained in this study was presented in abstract form at the XXII International Congress of The Transplantation Society, Sydney, Australia, 10–14 August 2008. The authors are grateful to Ms. Sandra Luen for coordination of sample collection.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.