Successful outcome of progressive multifocal leukoencephalopathy in a renal transplant patient

Natalizumab treatment for multiple sclerosis: recommendations for patient selection and monitoring

Natalizumab is a new treatment option for patients with active relapsing-remitting multiple sclerosis. In phase III studies, natalizumab was highly effective and well tolerated; however, three cases of progressive multifocal leucoencephalopathy (PML) were identified (estimated incidence of one per 1000; 95% CI 0.2-2.8; mean treatment period 17.9 months). In this Review we summarise the current information on PML, the three confirmed cases of PML, and the results of an extensive safety assessment of all patients treated with natalizumab. On the basis of these reviews, we make recommendations for appropriate selection of candidates for natalizumab and pretreatment assessments. In addition, a three-step diagnostic and management algorithm was developed to monitor natalizumab-treated patients with multiple sclerosis for PML and other opportunistic infections. The algorithm includes strategies for clinical, MRI, and laboratory assessments. Maintaining clinical vigilance allows for early suspension of natalizumab in potential cases of PML, thereby increasing the opportunity for immune reconstitution, which may improve prognosis if PML is confirmed.

Polyomavirus BK-specific cellular immune response to VP1 and large T-antigen in kidney transplant recipients

Polyomavirus BK (BKV) is the primary cause of polyomavirus-associated nephropathy (PVAN) in kidney transplant (KT) recipients. Using ELISpot assays, we compared the frequency of interferon-gamma (IFN-gamma) secreting peripheral blood mononuclear cells (PBMC) after stimulation with overlapping peptide pools covering BKV large T-antigen (LT) and VP1 capsid proteins (VP1). In 10 healthy donors, LT and VP1 responses were low with median 24 (range 15-95) and 25 (7-113) spot-forming units/10(6) PBMC (SFU), respectively. In 42 KT patients with current or recent plasma BKV loads, median LT and VP1 responses of 29 (0-524) and 114 (0-1432) SFU were detected, respectively. In KT patients with decreasing or past plasma BKV loads, significantly higher median BKV-specific IFN-gamma responses were detected compared to KT patients with increasing or persisting BKV loads [LT: 78 (8-524) vs. 22 (0-120) SFU, p=0.003; VP1: 285 (45-1432) vs. 53 (0-423) SFU, p=0.001, respectively]. VP1-specific IFN-gamma responses were higher and more likely to involve CD4(+) T cells, while CD8(+) T cells were more frequently directed against LT. Stimulation with JCV-specific VP1 and LT peptides indicated only low-level cross-recognition. The data suggest that control of BKV replication is correlated with differentiated expansion of BKV-specific cellular immune responses.

Reversible parkinsonism in a patient with progressive multifocal leucoencephalopathy

A case of pathologically confirmed progressive multifocal leucoencephalopathy presenting with unilateral parkinsonism and cognitive decline that significantly improved over a 12-month period without any treatment is described. The patient had a background of chronic lymphocytic leukaemia, but had been in complete remission for 4 years at the time of diagnosis. This case is highly unusual not only in terms of the mode of clinical presentation in an apparently immunocompetent patient but also in that the patient spontaneously improved without any intervention. Progressive multifocal leucoencephalopathy should therefore be considered in the differential diagnosis of movement disorders developing in patients with a history of lymphoproliferative disease, even if they are in remission. Furthermore, such cases may not always require treatment, as the patient's immune system may overcome the viral disease process with spontaneous resolution of their neurological disorder.

Molecular and clinical perspectives of polyomaviruses: emerging evidence of importance in non-kidney transplant populations

JC virus (JCV), BK virus (BKV) and simian virus 40 (SV40) are deoxyribonucleic acid (DNA) viruses, members of the family Polyomaviridae. These viruses establish persistent infections, and reactivate from latency in their host under immunosuppression. During the last few years there has been recognition of the morbidity related to polyomaviruses, particularly BKV in kidney transplant recipients. More importantly, recent studies indicate the potential implication of JCV, BKV, and SV40 in renal dysfunction among nonrenal organ transplant patients. Polyomaviruses are tumor-inducing viruses and animal models have provided evidence of the oncogenicity of these pathogens. Although data are not conclusive, molecular studies suggest an association of BKV and SV40 with malignancies among solid organ transplant patients. As new and potent immunosuppressive agents are introduced into clinical practice, it is believed that the incidence of polyomavirus-related diseases in organ transplantation might increase. This review evaluates the biologic and epidemiologic features of these 3 viruses, the data regarding their infections in nonkidney organ transplant patients and describes future directions in the management and research of these opportunistic pathogens.

Polyomavirus-associated nephropathy: update on BK virus-specific immunity

The human polyomavirus type 1, also called BK virus (BKV), causes polyomavirus-associated nephropathy (PVAN) in 1-10% of renal transplant recipients, with graft loss in over 50% of cases. The risk factors for PVAN are not conclusively defined and likely involve complementing determinants of recipient, graft, and virus. A central element seems to be the failing balance between BKV replication and BKV-specific immune control, which can result from intense triple immunosuppression, HLA-mismatches, prior rejection and anti-rejection treatment, or BKV-seropositive donor/seronegative recipient pairs. Consistent with this general hypothesis, the timely reduction of immunosuppression in kidney transplant recipients reduced graft loss to less than 10% of cases. However, the BKV-specific humoral and cellular immune response is not well characterized. Recent work from several groups suggest that changes in antibody titers and BKV-specific CD4+ and CD8+ T cells may help to better define the risk and the course of PVAN in renal transplant patients.

[Infections after organ transplantation]

Early postoperative infections after transplantation vary according to the transplanted organ. During the subsequent course opportunistic infections such as cytomegalovirus reactivation, Pneumocystis jiroveci pneumonia, invasive pneumococcal infection and mould infections predominate. Reactivated tuberculous infection appears to become more prevalent. Some of the opportunistic infections are preventable by chemoprophylaxis; others can be managed very effectively by monitoring and early preemptive therapy. Physicians caring for patients after organ transplantation need to early consider in the differential diagnosis rare pathogens which are often overlooked with standard diagnostic procedures.