Progressive multifocal leukoencephalopathy after natalizumab monotherapy.

We describe progressive multifocal leukoencephalopathy (PML) caused by infection with human polyomavirus JC virus in a patient with multiple sclerosis who was treated with natalizumab. The first PML symptoms appeared after 14 monthly infusions of the drug. Magnetic resonance imaging (MRI) showed a presumed multiple sclerosis lesion, and JC virus DNA was not detected on polymerase-chain-reaction (PCR) assay of cerebrospinal fluid. The patient's symptoms worsened, and the diagnosis of PML was established with a more sensitive quantitative PCR assay after 16 infusions of natalizumab. Plasma exchange was used to accelerate clearance of natalizumab. Approximately 3 weeks after plasma exchange, an immune-reconstitution inflammatory syndrome appeared. JC virus DNA was no longer detectable on quantitative PCR assay, and the patient's symptoms improved.

A case of posterior reversible encephalopathy syndrome associated with gilenya(®) (fingolimod) treatment for multiple sclerosis.

We describe posterior reversible encephalopathy syndrome (PRES) in a woman with multiple sclerosis treated with Gilenya(®) (Fingolimod). The first symptoms appeared after 21 months of fingolimod treatment. She experienced headache, altered mental status, cognitive deficits, seizures, and visual disturbances. Not at any time during the course of the disease could any signs of infection or rheumatic disorder be detected. Test for anti-neuronal antibodies was also negative. Her blood pressure was normal. MRI showed widespread cortical and subcortical changes with some mass-effect in the temporo-occipital-parietal lobes in the left hemisphere. Contrast enhancement was seen in the leptomeninges and, in addition, there were no areas with restricted diffusion and no signs of hemorrhage. Her condition deteriorated until fingolimod was discontinued. Slowly her condition improved and after 8 months, the only symptoms that remained were two small, non-corresponding, right inferior scotomas. We believe that all symptoms, the clinical course, and the MRI findings in this case can all be explained by considering PRES, a probably rare, but serious, side effect of fingolimod treatment.

On the Distribution of GAP-43 and its Relation to Serotonin in Adult Monkey and Cat Spinal Cord and Lower Brainstem.

By use of a monoclonal antibody, the distribution of growth-associated protein (GAP)-43-like immunoreactivity (LI) has been studied in the spinal cord of adult grey monkeys (Macaca fascicularis) and adult cats by use of immunofluorescence and peroxidase - antiperoxidase techniques. The brainstem was also studied with in situ hybridization histochemistry. In both monkeys and cats, a dense innervation of GAP-43-immunoreactive (IR) fibres was seen in close apposition to large cell bodies and their processes in the motor nucleus of the ventral horn. Double-labelling experiments revealed a high degree of coexistence between GAP-43- and 5-hydroxytryptamine (5-HT, serotonin)-LI in the monkey motor nucleus, while in the cat no such colocalization could be verified. At the electron microscopic level, GAP-43 labelling was seen as a coating of vesicles and axolemma inside the terminals. In both monkey and cat, cell bodies expressing mRNA encoding GAP-43 were demonstrated in the medullary midline raphe nuclei. A similar location was also encountered for mRNA for aromatic l-amino acid decarboxylase, an enzyme found in both catecholamine- and serotonin-containing neurons. The present results suggest that GAP-43 is present in the 5-HT bulbospinal pathway of the monkey. In the cat, GAP-43 mRNA-expressing cell bodies were demonstrated in areas where descending 5-HT neurons are located, but no convincing colocalization of 5-HT- and GAP-43-LI was found at spinal cord levels, despite the existence of extensive fibre networks containing either of the two compounds. Possible explanations for this species discrepancy are discussed. The function of GAP-43 in nerve terminals impinging on the motoneurons is unknown. However, it may play a role in transmitter release and/or plasticity, since such roles have been proposed for this protein in other systems.

Presymptomatic diagnosis with MRI and adequate treatment ameliorate the outcome after natalizumab-associated progressive multifocal leukoencephalopathy.

Natalizumab (Tysabri(®)) is a monoclonal antibody that prevents inflammatory cells from binding to brain endothelial cells and passing into the brain parenchyma. Natalizumab is a highly effective treatment for relapsing-remitting multiple sclerosis (MS). Progressive multifocal leukoencephalopathy (PML) is an opportunistic brain JC virus infection that has been shown to be associated with natalizumab treatment. We describe PML in a patient with MS after 44 monthly infusions of natalizumab. With the aid of a routine Magnetic resonance imaging (MRI) scan, PML was detected before any unambiguous clinical manifestations had emerged. PML was treated with plasma exchange to accelerate removal of natalizumab. Mirtazapine and mefloquine was promptly added and approximately 1 month after plasma exchange, when an immune-reconstitution-inflammatory-syndrome appeared, steroid treatment was initiated. Steroid treatment was then continued until no virus could be detected in the cerebrospinal fluid. The outcome was favorable. We believe that this case clearly illustrates the importance of an early, presymptomatic, detection of PML, and an adequate treatment. We also propose that surveillance with MRI scans, every 3 months after 24 months of treatment, should be performed in JC virus antibody positive natalizumab-treated MS patients in order to detect PML in an early phase.

Activating transcription factor 3, a useful marker for regenerative response after nerve root injury.

Activating transcription factor 3 (ATF3) is induced in various tissues in response to stress. In this experiment, ATF3 expression was studied in adult rats subjected either to a dorsal or ventral root avulsion (VRA; L4-6), or sciatic nerve transection (SNT). Post-operative survival times varied between 1.5 h and 3 weeks. In additional experiments an avulsed ventral root was directly replanted to the spinal cord. Dorsal root ganglias (DRGs) from humans exposed to traumatic dorsal root avulsions were also examined. After SNT ATF3 immunoreactivity (ATF3 IR) was detected in a few DRG neurons already 6 h after the lesion. After 24 h the number had clearly increased and still at 3 weeks DRG neurons remained labeled. In the ventral horn, ATF3 IR in motoneurons (MN) was first detected 24 h after the SNT, and still 3 weeks post-operatively lesioned MN showed ATF3 labeling. After a VRA many spinal MN showed ATF3 IR already after 3 h, and after 6 h all MN were labeled. At 3 weeks a majority of the lesioned MN had died, but all the remaining ones were labeled. When an avulsed ventral root was directly replanted, MN survived and were still labeled at 5 weeks. In DRG, a few neurons were labeled already at 1.5 h after a dorsal root avulsion. At 24 h the number had increased but still only a minority of the neurons were labeled. At 3 days the number of labeled neurons was reduced, and a further reduction was at hand at 7 days and 3 weeks. In parallel, in humans, 3 days after a traumatic dorsal root avulsion, only a few DRG neurons showed ATF3 IR. At 6 weeks no labeled neurons could be detected. These facts imply that ATF3 response to axotomy involves a distance-dependent mechanism. ATF3 also appears to be a useful and reliable neuronal marker of nerve lesions even in humans. In addition, ATF3 up-regulation in both motor and sensory neurons seems to be linked to regenerative competence.

On acute gene expression changes after ventral root replantation.

Replantation of avulsed spinal ventral roots has been show to enable significant and useful regrowth of motor axons in both experimental animals and in human clinical cases, making up an interesting exception to the rule of unsuccessful neuronal regeneration in central nervous system. Compared to avulsion without repair, ventral root replantation seems to rescue lesioned motoneurons from death. In this study we have analyzed the acute response to ventral root avulsion and replantation in adult rats with gene arrays combined with cluster analysis of gene ontology search terms. The data show significant differences between rats subjected to ventral replantation compared to avulsion only. Even though number of genes related to cell death is similar in the two models after 24 h, we observed a significantly larger number of genes related to neurite growth and development in the rats treated with ventral root replantation, possibly reflecting the neuroregenerative capacity in the replantation model. In addition, an acute inflammatory response was observed after avulsion, while effects on genes related to synaptic transmission were much more pronounced after replantation than after avulsion alone. These data indicate that the axonal regenerative response from replantation is initiated at an earlier stage than the possible differences in terms of neuron survival. We conclude that this type of analysis may facilitate the comparison of the acute response in two types of injury.

Functional energetics of CD4+-cellular immunity in monoclonal antibody-associated progressive multifocal leukoencephalopathy in autoimmune disorders.

BACKGROUND: Progressive multifocal leukoencephalopathy (PML) is an opportunistic central nervous system- (CNS-) infection that typically occurs in a subset of immunocompromised individuals. An increasing incidence of PML has recently been reported in patients receiving monoclonal antibody (mAb) therapy for the treatment of autoimmune diseases, particularly those treated with natalizumab, efalizumab and rituximab. Intracellular CD4(+)-ATP-concentration (iATP) functionally reflects cellular immunocompetence and inversely correlates with risk of infections during immunosuppressive therapy. We investigated whether iATP may assist in individualized risk stratification for opportunistic infections during mAb-treatment. METHODOLOGY/PRINCIPAL FINDINGS: iATP in PHA-stimulated, immunoselected CD4(+)-cells was analyzed using an FDA-approved assay. iATP of mAb-associated PML (natalizumab (n = 8), rituximab (n = 2), efalizumab (n = 1)), or other cases of opportunistic CNS-infections (HIV-associated PML (n = 2), spontaneous PML, PML in a psoriasis patient under fumaric acids, natalizumab-associated herpes simplex encephalitis (n = 1 each)) was reduced by 59% (194.5±29 ng/ml, mean±SEM) in comparison to healthy controls (HC, 479.9±19.8 ng/ml, p<0.0001). iATP in 14 of these 16 patients was at or below 3(rd) percentile of healthy controls, similar to HIV-patients (n = 18). In contrast, CD4(+)-cell numbers were reduced in only 7 of 15 patients, for whom cell counts were available. iATP correlated with mitochondrial transmembrane potential (ΔΨ(m)) (iATP/ΔΨ(m)-correlation:tau = 0.49, p = 0.03). Whereas mean iATP of cross-sectionally analysed natalizumab-treated patients was unaltered (448.7±12 ng/ml, n = 150), iATP was moderately decreased (316.2±26.1 ng/ml, p = 0.04) in patients (n = 7) who had been treated already during the pivotal phase III trials and had received natalizumab for more than 6 years. 2/92 (2%) patients with less than 24 months natalizumab treatment revealed very low iATP at or below the 3(rd) percentile of HC, whereas 10/58 (17%) of the patients treated for more than 24 months had such low iATP-concentrations. CONCLUSION: Our results suggest that bioenergetic parameters such as iATP may assist in risk stratification under mAb-immunotherapy of autoimmune disorders.

A role for MHC class I molecules in synaptic plasticity and regeneration of neurons after axotomy.

Recently, MHC class I molecules have been shown to be important for the retraction of synaptic connections that normally occurs during development [Huh, G.S., Boulanger, L. M., Du, H., Riquelme, P. A., Brotz, T. M. & Shatz, C. J. (2000) Science 290, 2155-2158]. In the adult CNS, a classical response of neurons to axon lesion is the detachment of synapses from the cell body and dendrites. We have investigated whether MHC I molecules are involved also in this type of synaptic detachment by studying the synaptic input to sciatic motoneurons at 1 week after peripheral nerve transection in beta2-microglobulin or transporter associated with antigen processing 1-null mutant mice, in which cell surface MHC I expression is impaired. Surprisingly, lesioned motoneurons in mutant mice showed more extensive synaptic detachments than those in wild-type animals. This surplus removal of synapses was entirely directed toward inhibitory synapses assembled in clusters. In parallel, a significantly smaller population of motoneurons reinnervated the distal stump of the transected sciatic nerve in mutants. MHC I molecules, which traditionally have been linked with immunological mechanisms, are thus crucial for a selective maintenance of synapses during the synaptic removal process in neurons after lesion, and the lack of MHC I expression may impede the ability of neurons to regenerate axons.

Induction of HIF1alpha but not HIF2alpha in motoneurons after ventral funiculus axotomy-implication in neuronal survival strategies.

Spinal cord injury is frequently associated with local tissue hypoxia. As neuronal cells are susceptible to damage caused by low oxygen levels, hypoxia-induced activation of tissue-protective factors could represent an endogenous mechanism for neuron survival following injury. We studied in vivo, in a rat model of intraspinal axotomy of motoneurons, the cell- and time-dependent regulation of the hypoxia-inducible transcription factors (HIFs), HIF1alpha and HIF2alpha, as well as one of their target genes, vascular endothelial growth factor (VEGF). VEGF is a potent hypoxia-regulated angiogenic growth factor with recently discovered neuroprotective and neurotrophic activities. While neither HIF1alpha, HIF2alpha, nor VEGF mRNA were detected in noninjured motoneurons, we found a strong induction of HIF1alpha, but not HIF2alpha mRNA in axotomized motoneurons. HIF1alpha expression peaked at about 7 days after injury. Moreover, we found increased VEGF mRNA and protein expression around and within the scar but also within motoneurons, peaking around 3 days after axotomy. In addition, increased survival of cultured motoneurons after treatment with VEGF could also be shown. We conclude that axotomized motoneurons in this model respond to injury by specific induction of HIF1alpha and VEGF expression that may provide an endogenous mechanism with the potential to promote motoneuron survival after injury.