Early monitoring of the human polyomavirus BK replication and sequencing analysis in a cohort of adult kidney transplant patients treated with basiliximab.

BACKGROUND: Nowadays, better immunosuppressors have decreased the rates of acute rejection in kidney transplantation, but have also led to the emergence of BKV-associated nephropathy (BKVAN). Therefore, we prospectively investigated BKV load in plasma and urine samples in a cohort of kidney transplants, receiving basiliximab combined with a mycophenolate mofetil-based triple immunotherapy, to evaluate the difference between BKV replication during the first 3 months post-transplantation, characterized by the non-depleting action of basiliximab, versus the second 3 months, in which the maintenance therapy acts alone. We also performed sequencing analysis to assess whether a particular BKV subtype/subgroup or transcriptional control region (TCR) variants were present. METHODS: We monitored BK viruria and viremia by quantitative polymerase chain reaction (Q-PCR) at 12 hours (Tx), 1 (T1), 3 (T2) and 6 (T3) months post-transplantation among 60 kidney transplant patients. Sequencing analysis was performed by nested-PCR with specific primers for TCR and VP1 regions. Data were statistically analyzed using χ² test and Student's t-test. RESULTS: BKV was detected at Tx in 4/60 urine and in 16/60 plasma, with median viral loads of 3.70 log GEq/mL and 3.79 log GEq/mL, respectively, followed by a significant increase of both BKV-positive transplants (32/60) and median values of viruria (5.78 log GEq/mL) and viremia (4.52 log GEq/mL) at T2. Conversely, a significantly decrease of patients with viruria and viremia (17/60) was observed at T3, together with a reduction of the median urinary and plasma viral loads (4.09 log GEq/mL and 4.00 log GEq/mL, respectively). BKV TCR sequence analysis always showed the presence of archetypal sequences, with a few single-nucleotide substitutions and one nucleotide insertion that, interestingly, were all representative of the particular subtypes/subgroups we identified by VP1 sequencing analysis: I/b-2 and IV/c-2. CONCLUSIONS: Our results confirm previous studies indicating that BKV replication may occur during the early hours after kidney transplantation, reaches the highest incidence in the third post-transplantation month and then decreases within the sixth month, maybe due to induction therapy. Moreover, it might become clinically useful whether specific BKV subtypes or rearrangements could be linked to a particular disease state in order to detect them before BKVAN onset.

Polyomavirus JC reactivation and noncoding control region sequence analysis in pediatric Crohn's disease patients treated with infliximab.

The recent introduction of monoclonal antibodies in Crohn's disease (CD) management has been associated with the development of serious complications, such as the progressive multifocal leukoencephalopathy (PML), caused by JC polyomavirus (JCV) reactivation. Therefore, the aims of our study have been the investigation of the possible JCV reactivation in pediatric CD patients treated or not with infliximab, performing quantitative PCR in urine, plasma, and intestinal biopsies at the time of recruitment (t0) and every 4 months in 1 year of follow-up (t1, t2, and t3), and the analysis of the JCV noncoding control region (NCCR) to detect cellular transcription factors binding site mutations. Results obtained showed that, in urine and ileal specimens, JCV load significantly increased in infliximab-treated patients after 1 year of treatment (t3), while viremia was significantly higher at t1. JCV NCCR sequence analysis showed a structure similar to CY archetype in 65/80 analyzed sequences, but the remaining 15/80, obtained exclusively from plasma and biopsies, evidenced a CY NCCR organization with two recurrent nucleotide changes, the 37-T to G transversion in box A Spi-B binding site and the 217-G to A transition in box F, and a box D deletion. These rearrangements were always found at t3 within seven infliximab-treated CD patients, who presented a very severe disease at t0. We can conclude that our rearranged NCCR sequences could be considered a marker of JCV virulence during mAb treatment, although none of our examined patients developed PML, and further studies on a larger cohort of patients should be performed.