POLYOMA BK VIRUS INFECTION

Fabrizio Ginevri, Genoa, Italy

Chair: Alex M. Davison, Ancrum, United Kingdom

Gerhard Opelz, Heidelberg, Germany

Dr F. Ginevri Nephrology Unit Istituto G. Gaslini Genova, Italy

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Slide 1

I wish to thank the organisers for the kind invitation. Dear Chairs, Dear Colleagues.

Slide 2

Polyomavirus BK is a DNA virus that infects the large majority of the population by the end of childhood. After primary infection, urothelium represents the site of viral latency and replication. In healthy subjects, BKV infection is asymptomatic, while BKV disease mostly develops in immunocompromised hosts.

Slide 3

The virus has been linked to several pathologic conditions, such as haemorrhagic cystitis, frequent after bone marrow transplantation, ureteral stenosis, vasculopathy and multiorgan failure. Lately, BKV-associated nephropathy has received increasing attention as an important cause of renal dysfunction after kidney transplantation. The prevalence is 1-10% with the majority of cases occurring in the first year after transplantation. Graft loss due to polyomavirus nephropathy ranges from 10 to 80%, but in the centres with active screening programs the rate of graft loss is lower.

Slide 4

There is limited information regarding PVAN pathogenesis, which is multifactorial. PVAN determinants related to the host, such as age, gender, diabetes, and negative serostatus, to the graft, such as degree of HLA-matching and prior rejection episodes, and to the virus, such as genome mutations, all concur in creating a permissive environment for BKV replication. In this context, immunosuppression represents the major risk factor for PVAN.

Slide 5

Renal injury due to the transplant procedure favours the replication of BKV in the graft. Intensive immunosuppression inhibits the development of BKV immune response in seronegative patients or inhibits the expansion of T-cell memory in seropositive hosts. Our group was able to demonstrate absence of BKV specific T cell response, measured as IFNγ secreting cells, in patients with BKV nephropathy. As a consequence of immunosuppression and impaired immune function, BKV spreads in the graft and causes direct damage. A late emergence of specific immunity, or of an aspecific immune reaction, may favour the progression of an established nephropathy.

Slide 6

Given the heterogeneity of the risk factors, the only single common feature in patients at risk for BKV nephropathy is the replication of the virus. Therefore, absence of BKV replication in urine measured by cytology or PCR allows to safely exclude BKV nephropathy, while the presence of decoy cells or BKV DNA in urine makes the diagnosis possible. In this case we need an adjunct test of higher specificity for BKV nephropathy, such as Quantitative BKV DNA determination in blood. The positivity for this adjunct test allows to make a diagnosis of presumptive PVAN. To have a definitive diagnosis, we need histology with demonstration of viral cytopathic changes, and evidence of viral material in the kidney by immunohistochemistry or in situ hybridisation. 

Slide 7

PVAN is classified into three histologic patterns, from early grade A lesions, where only viral cytopathic changes are present, to late grade C lesions, where tubular atrophy and interstitial fibrosis are the main dominant features. We have also to add that PVAN has a focal presentation and, as a consequence, a negative biopsy, mainly in the early stages of disease, cannot rule out PVAN with certainty.

Slide 8

If we don’t treat the patients, the prognosis is poor and, as demonstrated by Doctor Ramos in a previously published paper, there is a worse outcome in patients with BK nephropathy as compared to patients with allograft dysfunction of any other cause.

Slide 9

The mainstay of treatment is reduction of immunosuppression. However, control of viral replication has been tried with several therapeutic approaches, including the antiviral drug cidofovir, immunoglobulins, quinolone antibiotics, and, recently, the immunosuppressive drug leflunomide. However, due to the absence of controlled trials, there is no consensus on a standard treatment for this pathology.

Slide 10

Moreover, if we treat PVAN at a late stage, the beneficial effects are limited, as demonstrated in the paper by Doctor Ramos, comparing two populations of patients, treated or not with immunosuppression reduction.

Slide 11

In more recent times, the development of new diagnostic tools and a better understanding of the pathology has led to treatment at earlier stages, with improved outcome. As in the case of other viral infections relevant to transplantation, it would be important to have a surrogate marker of preclinical disease, for early diagnosis and preemptive treatment.

Slide 12

Viral load in plasma could be useful to treat the patients at the pre-emptive stage, since, as demonstrated by the Basel group, positivity of viremia precedes by weeks the onset of PVAN.

Slide 13

Recent data by Doctor Brennan in Saint Louis have shown that pre-emptive reduction of immunosuppression, prompted by BKV DNA positivity in blood, was associated with resolution of viremia and absence of nephropathy development without increasing the risk of acute rejection or graft loss.

Slide 14

We treated with a similar strategy a group of paediatric patients. We monitored on a three-monthly basis the patients, and in case of plasma positivity with negative renal biopsy, we proceeded with immunosuppression reduction, according to the protocol described in the slide. In cases of persistent viremia we tightened the monitoring, and we proceeded with a multistep reduction of immunosuppression, starting with calcinurine inhibitors adjustment, followed by reduction or discontinuation of the third drug, in case of non-response.

Slide 15

In our cohort most of the virurias and viremias occurred in the first 6 months after transplantation. BKV viruria was observed in 72% of the population and viremia in 9% of the total population.

Slide 16

Among the patients with BKV replication, 2 patients cleared viremia only with protocol immunosuppression reduction, while 3 patients required pre-emptive reduction of immunosuppression. All 3 kidney recipients cleared viremia. None of the patients progressed to PVAN or experienced rejection episodes as a result of immunosuppression reduction.

Slide 17

Viremia did not clear immediately, but required a few months. Upon the emergence of BKV specific immunity we observed clearance of viremia and stabilisation of graft function.

Slide 18

Since BKV replication and polyomavirus nephropathy seem to be a consequence of impaired specific immune function, monitoring of BKV specific T cell immunity and restoration of specific immunity in high-risk patients may represent valuable tools in the management of this pathology.

Slide 19

Regarding the possibility of a cell therapy strategy, Doctor Comoli in Pavia developed a method to generate and expand in vitro BKV specific CTLs, employing dendritic cells pulsed with chemically inactivated virus or viral protein-derived peptides as stimulators.

Slide 20

The cells thus generated were specific for the virus and not alloreactive, since they were able to kill autologous BKV-infected cells, while they did not show cytotoxicity against allogeneic uninfected cells. Moreover, these BKV-specific T cell lines include specificities for early and late viral proteins.

Slide 21

In conclusion, in order to limit the risk of polyomavirus associated nephropathy and to improve outcome, future studies will have to address the following issues: define screening strategy that combines efficacy and feasibility; confirm the efficacy of pre-emptive treatment; develop new strategies for prevention and treatment of BKV disease, such as new antiviral drugs or strategies to improve immune surveillance, like vaccination or cell therapy.

Slide 22

Finally I wish to thank the people involved in this study, in particular the immunology expertise of Doctor Comoli and the virology group of Professor Azzi in Firenze. Thank you very much for your attention.

Slide 23

Chairman: Thank you Doctor Ginevri for this very clear presentation. We have time for a couple of questions. Yes please there’s a question over here.

Questions: Although this was not your experience, if a patient suffers from rejection, acute rejection would you treat him or not?

Dr Ginevri: If we demonstrate a rejection episode, we treat rejection with pulse steroids, and reduce maintenance immunosuppression. The problem is to differentiate rejection from virus-related infiltrate. So if you have a vascular rejection, there are no problems to differentiate the histology. If you have cellular rejection grade 1a, differential diagnosis is more difficult, and you need a good expertise to obtain a differential diagnosis.

Question: If there is steroid resistant rejection, would you continue acute rejection treatment or just stop?

Dr Ginevri: In my casistic I did not encounter this particular situation, so I don’t know exactly what to answer to your question. It’s very difficult because you have to be sure that it is rejection and that it is unresponsive to steroids. Probably, it’s better to re-biopsy before deciding on further treatment.

Question: Is it necessary to explant the kidney for the next transplantation?

Dr Ginevri: Removal of the original graft is not a prerequisite to perform a second transplant. After demonstration of viral clearance upon reduction or discontinuation of immunosuppression, there are no problems to re-transplant this patient. Problems arise if there are concomitant combined transplants, such as pancreas, liver or heart allografts, where you need to maintain the immunosuppression. However, I think that if you monitor carefully for BKV and adjust immunosuppression accordingly, probably the outcome will be good without kidney removal.

Question: Thank you for the lecture. There are some types of inclusions for the virus, the inclusions with halo, there is vesicular inclusion, is there any data about the significance of these types of inclusions in terms of response to treatment?

Dr Ginevri: No, there are no real data correlating inclusion types and treatment outcome, Because of lack of data, I think it is difficult to answer your question.

Question: There is some data about the in vitro effect of ciprofloxacin on replication of virus. Ciprofloxacin, Kinolons.

Dr Ginevri: Ciprofloxacin, yes.

Question: Is there any in vitro study?

Dr Ginevri: There are in vitro studies. However, for all therapeutic approaches applied so far, such as cidofovir, leflunomide, and ciprofloxacin, it’s very difficult to dissociate the direct antiviral effect and the effect of reduction of immunosuppression, that is actuated in all patients. Regarding the quinolons, there are only a few anecdoctal data in patients, and no controlled trial, so it’s very difficult to evaluate efficacy.

Chairman: O.k. thank you very much Doctor Ginevri. I think we have exhausted it. We have no more time. I thank everyone for participating and especially the speakers. Thank you very much.