· Regarding JCV viremia in the renal transplant recipients, it seems to be uncommon (maybe 10-15%), transient and low level. Rates may not be different to immunocompetent individuals and it does not appear to correlate with renal dysfunction. Viremia appears to be even less common in other solid organ recipients.
· In the few reported cases of apparent JC Nephropathy, there has been poor correlation with JC viremia in contrast to the relationship with BK viremia and BK nephropathy. A prospective cohort of 980 renal transplant patients reported >40% JC viruria, 14.5% JC viremia with 0.9% developing JC Nephropathy. The patients who were biopsied with JC shedding mostly had stable renal function and were biopsied due to decoy cell shedding. The few who had a bump in creatinine which prompted biopsy had other reasons to explain the allograft dysfunction (e.g. ATN). Reduction of immunosuppression did not clear viral replication but no graft loss occurred.
· Many people in the 1950s-60s were exposed to contaminated vaccines containing the SV-40 (Simian Virus 40) virus, another Polyoma virus. The immunohistochemical stain used to diagnose Polyoma Virus nephropathy on biopsy uses antibodies mostly specific to SV-40 and cannot distinguish between BK, JC and SV-40 viruses. There is speculation that SV-40 may also potentially cause nephropathy.
Ok enough already, does JC Virus Nephropathy exist? …..Probably! Certainly it appears to be rare and not correlated with BK Nephropathy. It has a different relationship with immunosuppression from BK Nephropathy and appears to have a favorable outcome. So what is the significance of JC Virus replication post renal transplant? Very little, at least for viruria. In fact, patients seem to have less BK replication when JC viruria is present and there is even a suggestion of a better outcome in patients shedding JC, which is independent of the lower incidence of BK replication. Should we screen for JC Virus replication post kidney transplant? I don’t see a compelling reason based on our current knowlegde.