Conversion to mTOR-inhibitors with calcineurin inhibitor elimination or minimization reduces urinary polyomavirus BK load in kidney transplant recipients

J Formos Med Assoc. 2016 Jul;115(7):539-46. doi: 10.1016/j.jfma.2016.01.008. Epub 2016 Mar 16.


Background/purpose: Polyomavirus BK (BKV) reactivation causes allograft dysfunction in some kidney transplant recipients. The use of mammalian target of rapamycin (mTOR) inhibitor-based immunotherapy is associated with a lower incidence of polyomavirus-associated nephropathy compared with other immunosuppressants. This retrospective study assessed whether conversion to mTOR inhibitor-based immunotherapy directly reduced urinary BKV load.

Methods: A total of 63 kidney recipients were divided into mTOR inhibitor-conversion (21 patients) and nonconversion (42 patients) groups. Urinary BKV loads were determined before and at least 6 months after the conversion.

Results: The results demonstrated that urinary BKV titer was significantly reduced in the conversion group (3.94 ± 0.43 copies (log)/mL to 2.49 ± 0.19 copies (log)/mL) and remained unaltered in the nonconversion group (3.19 ± 0.20 copies (log)/mL to 2.90 ± 0.20 copies (log)/mL). In addition, the percentage of patients with reduced urinary BKV load was significantly higher in the conversion group (76.2% vs. 42.9%). The estimated glomerular filtration rate after 24 months mTOR inhibitor conversion was significantly increased compared with that in the nonconversion group. Conversion to mTOR-inhibitor-based immunotherapy was the only factor associated with an increase in estimated glomerular filtration rate.

Conclusion: This study reveals an association of conversion to mTOR-inhibitor-based immunotherapy with the reduction of urinary BKV load.

Keywords: kidney transplantation; mammalian target of rapamycin; polyomavirus BK; viruria.

Publication types

  • Observational Study

MeSH terms

  • Adult
  • BK Virus / drug effects*
  • Creatinine / blood
  • Everolimus / therapeutic use
  • Female
  • Glomerular Filtration Rate
  • Humans
  • Immunosuppressive Agents / therapeutic use
  • Immunotherapy*
  • Kidney Diseases / epidemiology*
  • Kidney Diseases / virology
  • Kidney Transplantation*
  • Logistic Models
  • Male
  • Middle Aged
  • Polyomavirus Infections / drug therapy*
  • Postoperative Complications / drug therapy
  • Postoperative Complications / virology
  • Retrospective Studies
  • Sirolimus / therapeutic use
  • TOR Serine-Threonine Kinases / antagonists & inhibitors*
  • Taiwan
  • Viral Load / drug effects


  • Immunosuppressive Agents
  • Everolimus
  • Creatinine
  • TOR Serine-Threonine Kinases
  • Sirolimus