Viral (polyomavirus) cystitis heralding cytomegalovirus infection

Human polyoma virus-associated interstitial nephritis in the allograft kidney

BACKGROUND

Asymptomatic polyoma virus infection documented by urine cytology or serology is well known, but the clinical course of biopsy-proven interstitial nephritis is not well defined.

METHODS

Twenty-two cases were identified by histology, immunostaining, in situ hybridization, electron microscopy, or polymerase chain reaction.

RESULTS

The clinical features mimicked acute rejection (n=19), chronic rejection with incidental diagnosis at nephrectomy (n=2), or drug toxicity (n=1). Histology showed homogenous intranuclear inclusions. In situ hybridization showed BK virus (BKV) to be the predominant species, but polymerase chain reaction documented JC virus co-infection in one of five cases so tested. Electron microscopy in seven cases showed 20-51-nm virions. The two cases diagnosed at nephrectomy received no therapy. Initial antirejection therapy in 12 cases led to clearance of the virus in 1/12 (8%), partial therapeutic response in 3/12 (25%), and graft loss in 8/12 (67%) cases. The last recorded creatinine in patients with functional grafts ranged from 1.9 to 7.0 (median: 4.5) mg/dl, 0.4-45 (median: 4.0) months after initial diagnosis. The remaining eight cases treated by reduction of immunosuppression at the outset have been free of graft loss for 0.2-10.0 (median: 4.8) months since diagnosis, and clearance of virus has been documented in three of six (50%) cases. The serum creatinine in these patients is 1.7-6.0 (median: 2.4) mg/dl, 0.2-10 (median: 4.8) months after diagnosis. Follow-up biopsies performed 1-23.5 months after diagnosis show chronic allograft nephropathy.

CONCLUSIONS

Polyoma virus tubulo-interstitial nephritis-associated graft dysfunction usually calls for judicious decrease in immunosuppression and monitoring for acute rejection. Development of methods to serially quantify the viral load in individual patients could potentially improve clinical outcome.

Association between polyomaviruria and microscopic haematuria in bone marrow transplant recipients

The association of polyomaviruria and microscopic haematuria was studied by the use of electron microscopy (EM) and the polymerase chain reaction (PCR) in bone marrow transplant (BMT) recipients. The incidence of BK virus (BKV) and JC virus (JCV) excretion was further elucidated by means of restriction enzyme analysis of the PCR products. Polyomaviruses were detected in 43 (51.2%) of the 84 samples, 13 (30.2%) of which had a virus concentration detectable by EM. By typing with BamHI cleavage, 29 (67.4%) of the 43 positive patients were found to be excreting only BKV and the remaining 14% (32.6%) were excreting both BKV and JCV. Microscopic haematuria was present in 17 (20.2%) of 84 urine samples collected from different patients within 4 months post-transplant. The incidence of microscopic haematuria was significantly higher, 34.9% (P < 0.01), in patients with polyomaviruria than in those without (4.9%) but no difference was observed between the BKV-excreting and BKV/JCV-co-excreting patients. Microscopic haematuria was not present, however, in 53.8 and 65.2% of polyomavirus-excreting patients when virus was detected by EM and PCR respectively. While most episodes of microscopic haematuria observed were self-limiting and asymptomatic, three patients excreting polyomavirus had symptoms of cystitis and one of them had renal impairment that was otherwise unexplained. We thus conclude that polyomaviruses probably contribute to damage of urinary tract tissue in some BMT recipients.