1. Polyomavirus BK nephropathy
Fabrizio Ginevri
Kidney Transplantation Unit, Department of Nephrology,
Istituto G. Gaslini, Genova, Italy

2. BKV infection: the virus
DNA virus that belongs to the polyomaviridae family:
Polyomavirus BK
Polyomavirus JC
SV40
New: Polyomavirus KI, Polyomavirus WU, Polyomavirus MC
Structure:
The BKV genome comprises three regions:
1. the NCCR
2. the structural region coding for early T proteins
3. the late structural region encoding the viral capsid proteins (VP1-3) and agnoprotein

3. BKV infection: the virus
Infects up to 90% of the general population
Transmitted via aerosol, urinary shedding, allograft
After primary infection, renal tubular epithelial cells and the urothelial cell layer represent the principal sites of viral latency or replication
BKV disease is rare, and almost invariably associated with an immunodeficiency status

4. BKV infection after kidney transplantation
Reactivation/primary infection in KTx recipients:
asymptomatic infection
ureteral stenosis
systemic vasculopathy
interstitial nephropathy (BKVN):
increased prevalence of BKVN in the last decade (from 1% in 1995 to 5-10% in 2001)
the majority of cases occur within the 1st year after Tx, but at least 25% of cases are diagnosed later
10-80% graft loss: but, with increased awareness and improved diagnostic techniques, the rate of graft loss has lowered

5. BKV nephropathy after kidney Tx: risk factors
Patient determinants
age>50 yrs
male gender
diabetes
negative recipient serostatus before Tx
Organ determinants
degree of HLA-matching
prior rejection episodes
renal tissue injury
positive donor serostatus before Tx
Viral determinants
genome mutation and rearrangements
Immune
suppression
major risk factor for BKVN: it is plausible that a state of “over-immunosuppression”, rather than a specific agent is responsible for an increased risk of BKVN development

6. BKV nephropathy after kidney Tx: pathogenesis
Immunosuppression load:
triple vs. double therapy
Binet et al. Transplantation 1999
Hirsch et al. Transplantation 2005
Renal injury +
organ BK load
BKV mutations
PVAN
 BKV
replication
BKV-mediated
tissue damage +
Lack of immune memory:
BK seronegativity
Ginevri et al. Transplantation 2003
Smith et al. Am J Transplant 2004
Failure of immune surveillance

7. Analysis of BKV-specific immunity after KTx: parameters correlated with protection from BK viruria
IFN-g secreting cells
cytotoxicity
300 50
VP1
VP1
225
37,5
SFU/105 cells
% specific lysis
150 25 75
12,5 N
U+/U+P+ N
U+/U+P+ 50 LT
300 LT
p<0.05 *
p<0.005 **
37,5
225
% specific lysis
SFU/105 cells 25
150 75
12,5 N
U+/U+P+ N
U+/U+P+
Ginevri F, Comoli P, et al. manuscript in preparation

8. Analysis of BKV-specific immunity after KTx: parameters correlated with protection from BK viremia
IFN-g secreting cells
SFU/105 cells LT
166
333
500
U+_pre
U+_peak
U+P+_pre
U+P+_peakU
p=0.07
Ginevri F, Comoli P, et al. manuscript in preparation

9. Approach to screening for BKVN diagnosis
Ginevri F, Hirsch HH. BK polyomavirus nephropathy. 2008

10. BKV nephropathy after KTx: diagnosis
BKVN has a focal presentation
as a consequence, negative biopsy results cannot rule out BKVN with certainty
Histological patterns A
Viral cytopathic changes only, in near-normal renal parenchyma. B
Combination of viral cytopathic changes and
focal/multifocal areas of tubular atrophy/interstitial fibrosis/ inflammation C
Very scarce viral cytopathic changes in diffusely scarred renal tissue.
Extensive tubular atrophy/interstitial fibrosis /inflammation involving all the tissue core with no residual areas of non atrophic tubules.
Drachenberg et al. Hum Path 2005; 36:1245

11. Screening for BKVN and therapeutic intervention
Ginevri F, Hirsch HH. BK polyomavirus nephropathy. 2008

12. Treatment of “definitive” BKVN
The therapeutic mainstay is reduction of maintenance immunosuppression
Antivirals and other pharmacologic approaches have been variably associated
Ginevri F, Hirsch HH. BK polyomavirus nephropathy. 2008

13. Treatment of “definitive” BKVN: results
Early diagnosis has allowed a significant amelioration of prognosis
graft outcome:
no screening: % of BKVN treated with any protocol  marked graft dysfunction, with possible progression to graft loss;
screening and early treatment: no graft loss, milder graft dysfunction.
Ginevri F, Hirsch HH. BK polyomavirus nephropathy. 2008

14. Preemptive treatment of BKVN
On the basis of plasma BKV-DNA analysis
DNA threshold for treatment: >104 ge/ml
graft outcome: viremia clearance, no BKVN, no acute rejection
Ginevri F, Hirsch HH. BK polyomavirus nephropathy. 2008

15. BKVN prospective monitoring and preemptive treatment after pediatric KTx
62 pediatric KTx recipients referred between 01/02 and 08/05:
Group 1: BKV-sero+ patients, that did not reactivate after Tx
Group 2: patients with positive viruria after Tx
Group 3: patients with positive viruria and viremia after Tx
Prospective monitoring of BKV DNA, measured by Q-PCR, in urine and plasma.
+1, +3, +6, +9, +12, +18, +24, >24 months after KTX
0.0
0.2
0.4
0.6
0.8
1.0 12 24 36 48 60
MONTHS AFTER TRANSPLANTATION
CUMULATIVE INCIDENCE (95% CI)
Viruria: 64% (53-78)
Viremia: 22% (13-35)
Viruria: N = 62; E = 39
Viremia: N = 62; E = 13
Number of patients at risk:
Ginevri et al. Am J Transplant 2007

16. Results: effect of IS reduction on viral load and outcome
Ginevri et al. Am J Transplant 2007

17. Reconstitution dynamics of BKV-specific immunity after preemptive treatment
IFNg-secreting cells
266
533
800
Pre-BK
viremia
BK viremia
increase
decrease
Post-BK
clearance
Spots/105 cells
VP1 LT ** *
Sero+
controls
KTx-r
no BKV
Ginevri et al. Am J Transplant 2007

18. Reconstitution dynamics of BKV-specific T cells and serology in a patient with BKVN
Comoli, Ginevri, Hirsch. Transplant Infect Dis 2006

19. Monitoring of specific immunity in patients with BK viremia
Modulation of IS reduction according to cellular immunity analysis
100
200
300
400
103
104
105
106 1 2 3
0.5 4 6 9 12
IFN-g SFU/105
 VP1  LT
Plasma BKV load
Months post-Tx
Comoli P, Hirsch HH, Ginevri F. Curr Opin Organ Transplant 2008

20. BKVN after KTx: conclusions and open issues
Outcome of BKVN
when BKVN is advanced (stages B2-3 and C), outcome is still suboptimal
early treatment (stages A and B1) yields better results in terms of graft outcome
preemptive treatment on the basis of BK viremia seems at present the best option, but screening protocol has to be defined
Long term outcome of allografts after BKV infection
data on long-term allograft outcome after successful treatment for BKVN are scarce. However, preliminary results suggest that BKVN is a risk factor for progressive chronic allograft dysfunction
direct virus damage ?
suboptimal IS ?
In case of prevalent direct damage, preemptive treatment may allow to reduce considerably the risk of progressive allograft failure
In the second instance, tailoring of preemptive treatment on the basis of viremia and specific immune reconstitution may avoid excess IS reduction, and thus suboptimal IS

21. A Parodi E Verrina Pediatric Kidney Tx Program Genova, Italy
Pediatric Hematology/Oncology
Fondazione Policlinico S. Matteo, Pavia, Italy
P Comoli
S Basso
A Gurrado
Pediatric Kidney Tx Program
Genova, Italy
Pediatric Nephrology
Istituto G. Gaslini
F Ginevri
A Parodi E Verrina
M Cioni G Barbano
Department of Transplantation Ospedale S Martino
I Fontana
U Valente
Department of Public Health
Università di Firenze, Italy
A Azzi
Department of Transplantation Virology
University of Basel, Switzerland
H H Hirsch
Pediatric Kidney Disease Fund Genova, Italy
R Gusmano

22. Retransplantation
Retransplantation is a feasible option after graft loss to PAN : PAN recurrence in 2/13 reported patients (15%)
In the absence of active BKV infection
Nephrectomy of the original graft may not be necessary
Baseline IS: does not need to be specifically adjusted
In case of failure to reduce viral load or when IS reduction is contraindicated, the administration of antiviral drugs (e.g. cidofovir) and/or the surgical removal of the alloureter and kidney could be considered
Post-transplant follow-up management
Monitor: urine/plasma viral load
general/specific immunity
Therapeutic intervention guided by plasma DNA levels