PCR assays for the early detection of BKV infection in 125 Spanish kidney transplant patients

BK virus (BKV) reactivation arises from immunocompromised conditions and can produce a tubulointerstitial nephropathy (BKVN) in kidney transplant recipients (KTR). Approximately 5% of KTR develop BKVN, and about 45% of these lose their graft. Therefore, using molecular tools to test for BKV may be helpful in early detection. A series of 125 Spanish KTR, originating from a single transplant center, were studied in relation to BKV infection in the first post-transplant year. First, we carried out a urinary cytological study, looking for decoy cells as a possible marker of virus replication. Secondly, in all positive cytological samples and in some negative cytological samples (selected at random), we performed qualitative polymerase chain reaction (PCR) assays in serum and urine amplifying two different genome regions (LT and VP1). A transcription control region (TCR)-BK polymorphism sequence analysis was also performed in those BK PCR positive cases. Twenty-three of 125 (18.4%) KTR presented decoy cells in at least one urinary cytological sample. Molecular studies revealed that 10 of 125 (8%) KTR were BK PCR-serum positive cases (seven LT+/VP1- and three LT+/VP1+); and 13 of 40 (32.5%) KTR were BK PCR-urine positive cases (five LT+/VP1- and eight LT+/VP1+). When we compared PCR-urine and cytological results in 40 KTR, only 15% (six cases) revealed simultaneous positivity in both studies. In the context of clinical graft dysfunction, three patients demonstrated BK DNA presence in the renal biopsy. Finally, sequence analysis of the TCR was performed in 13 BK-PCR positive cases determining the AS, JL, WW, and WW-like viral variants. TCR sequence analysis, allows us to demonstrate the possible implication of the donor in BK infection studying four BK-PCR positive patients paired by donor.

Renal Donor Implication in the Origin of BK Infection: Analysis of Genomic Viral Subtypes

BK virus (BKV) reactivation in immunocompromised kidney transplant patients can produce a tubulointerstitial nephropathy (BKVN). Molecular tools that test for DNA-BKV provide early detection and assist in management, but some aspects of the pathogenesis of this infection, such as donor causality, remain unclear.

MATERIALS AND METHODS

Between November 2004 and January 2006, 55 Spanish kidney donors were studied for BK infection. A quantitative PCR assay was performed on urine and serum to detect BKV. To determine the origin of the viral infection, a transcription control region of the BK polymorphism sequence was designed to identify the viral subtype.

RESULTS

Fifteen of 55 (27%) donors were BK-PCR positive: 13 in urine and 2 in serum and urine. Moreover, monitoring of recipient pairs detected BK-PCR positivity in 14 of 73 recipients. We studied eight BK-PCR positive recipients (corresponding to four pairs) and their respective donors. The same viral genome was observed in the four pairs, namely, the A250-1-a, WW-like, AS, and JL genotypes. Interestingly, one of the four pairs showed the donor and the two recipients to display exactly the same JL genotype.

CONCLUSION

On the basis of our preliminary results analyzing the molecular fingerprints of donor and recipient pairs, we have presented new data implicating the donor, in at least some cases, as the source of BK infection.