prof. dr. H.G.M. (Bert) Niesters

BK virus in kidney transplant patients

BK virus belongs to the family Polyomaviridae. Polyomaviruses are small non-enveloped, double-stranded DNA viruses . Thus far, 6 human polyomaviruses are described; BK and JC virus, WU and KI virus, Merkel cell carcinoma virus and Trichodysplasia spinolosa virus. These viruses are ubiquitous human viruses and known to cause persistent or latent, but primarily asymptomatic, infections. In immunocompromised patients, however, these viruses may cause severe disease.

BK virus is urotheliotropic and its reactivation is linked to two major complications in transplant recipients. Polyomavirus-associated nephropathie (PyVAN) and polyomavirus-associated hemorrhagic cystitis (PyVHC). Most cases of PyVAN occur in kidney transplant patients. BK virus reactivation most likely results from reactivating BK virus in tubular epithelial cell of the donor kidney. Viruria can be detected in up to 80% of renal transplant patients and 5-10% will progress to PyVAN.  Patients with PyVAN present with increasing renal dysfunction. Graft-failure is reported in 50-70% of the patients diagnosed with PyVAN.

Within the UMCG about 120 kidney transplantations are being performed every year. Routinely, urine and plasma samples of these patients will be screened for BK virus by quantitative real-time PCR assay. A BK-virus specific serology assay is being implemented to investigate the serostatus pre-transplant. Four different BK virus genotypes have been identified. For the differentiation of these variants a multiplex RT-PCR will be developed.

The significance of BK virus subtypes and serostatus in relation to particular clinical symptoms or to different groups of immunocompromised patients will be evaluated.