BK polyoma viral infection in renal allograft recipients.

BACKGROUND: BK polyoma viral nephropathy (BKVAN) has emerged as a significant cause of renal allograft loss. The literature on BK viral infection from India is scarce. The study was therefore undertaken to evaluate impact of BK polyoma viral (BKV) infection on renal allograft recipients in Indian scenario from a service renal transplantation centre. METHODS: Renal allograft recipients who underwent graft biopsy formed the part of this descriptive cross-sectional study group. The clinicopathological profile of the patients was analysed. The diagnostic modalities employed were histopathology, immunohistochemistry using antibody for Simian virus 40 large T antigen along with real time quantification of the BK viral DNA load in the urine and the serum. RESULTS: One hundred forty seven renal allograft recipients were evaluated. 73.47 percent (108/147) patients presented with graft dysfunction and rest were protocol biopsies. There were 53 cases of rejection related diagnosis, 8 cases of graft pyelonephritis, 64 cases showed normal histology and rest exhibited miscellaneous causes. Nineteen percent (28/147) cases were positive for BKV DNA (viruria 26/147, 17.6% and viraemia 8/147, 5.44%. 3.4 percent (5/147) exhibited histological and immunohistochemical evidence of BKVAN. Nuclear enlargement, smudging and intranuclear inclusions along with plasma cell rich interstitial nephritis were important features observed on histopathology. Concomitant acute rejection was seen in 4/5 cases of BKVAN. All cases of BKVAN exhibited viraemia (> 2500 copies/mL), though cut-off values could not be defined statistically due to small sample size. Positive statistical correlation was observed between use of anti-thymocyte globulin (induction therapy and/or treatment of steroid resistant rejection, Pearson ×(2) value 6.9, P=0.008) and rejection episodes (Pearson ×(2) value 9.8, P = 0.007) with BKV infection. CONCLUSION: BK polyoma nephropathy should be added to the list of differential diagnosis considered for a renal allograft dysfunction. Renal biopsy remains the gold standard for diagnosis supplemented by non-invasive molecular techniques for screening and monitoring of BKV infection.