A multicenter prospective study to define the natural history of BK viral infections in kidney transplantation.

BACKGROUND: BK polyomavirus (BKV) can cause permanent loss of allograft function due to BKV-associated nephropathy (BKVN) in kidney transplant recipients. Besides immunosuppression reduction, there are no consistently effective interventions for BKV infection. Study purpose was to define natural history of BKV infection, identify risk factors for BKV reactivation and BKVN in kidney transplant recipients, and inform the design/conduct of future clinical trials of BKV-targeted therapeutics. METHODS: We conducted a multicenter prospective observational study of incident kidney transplant recipients at six U.S. transplant centers. Participants were monitored every 4 weeks for BKV reactivation and followed for up to 24 months post-transplant. We used regression models (logistic, survival, mixed models) to study relationships between BK viremia/BKVN, clinical characteristics, and allograft function. RESULTS: We enrolled 335 participants. Fifty-eight (17%) developed BK viremia, 6 (2%) developed biopsy-proven BKVN, and 29 (9%) developed suspected/presumed BKVN (defined as BKV viral load > 10,000 copies/mL without biopsy). Male donor sex was associated with lower odds for BK viremia, whereas recipient Black race was associated with two-fold increased odds for BK viremia. Recipient female sex was associated with more rapid clearance of BK viremia. Persistent BK viremia/BKVN was associated with poorer allograft function by 24 months post-transplant. CONCLUSIONS: We identified multiple donor and recipient demographic factors associated with risk for BKV infection and poorer allograft function by 24 months post-transplant. This may help design future clinical trials of therapies to prevent or mitigate the deleterious impact of BKV reactivation on kidney transplant outcomes.

Detection of Subclinical Rejection in Pediatric Kidney Transplantation: Current and Future Practices.

INTRODUCTION: The successes in the field of pediatric kidney transplantation over the past 60 years have been extraordinary. Year over year, there have been significant improvements in short-term graft survival. However, improvements in longer-term outcomes have been much less apparent. One important contributor has been the phenomenon of low-level rejection in the absence of clinical manifestations-so-called subclinical rejection (SCR). METHODS: Traditionally, rejection has been diagnosed by changes in clinical parameters, including but not limited to serum creatinine and proteinuria. This review examines the shortcomings of this approach, the effects of SCR on kidney allograft outcome, the benefits and drawbacks of surveillance biopsies to identify SCR, and new urine and blood biomarkers that define the presence or absence of SCR. RESULTS: Serum creatinine is an unreliable index of SCR. Surveillance biopsies are the method most utilized to detect SCR. However, these have significant drawbacks. New biomarkers show promise. These biomarkers include blood gene expression profiles and donor derived-cell free DNA; urine gene expression profiles; urinary cytokines, chemokines, and metabolomics; and other promising blood and urine tests. CONCLUSION: Specific emphasis is placed on studies carried out in pediatric kidney transplant recipients. TRIAL REGISTRATION: ClinicalTrials.gov: NCT03719339.