microRNA-146a-5p, Neurotropic Viral Infection and Prion Disease (PrD)

The human brain and central nervous system (CNS) harbor a select sub-group of potentially pathogenic microRNAs (miRNAs), including a well-characterized NF-kB-sensitive Homo sapiens microRNA hsa-miRNA-146a-5p (miRNA-146a). miRNA-146a is significantly over-expressed in progressive and often lethal viral- and prion-mediated and related neurological syndromes associated with progressive inflammatory neurodegeneration. These include ~18 different viral-induced encephalopathies for which data are available, at least ~10 known prion diseases (PrD) of animals and humans, Alzheimer’s disease (AD) and other sporadic and progressive age-related neurological disorders. Despite the apparent lack of nucleic acids in prions, both DNA- and RNA-containing viruses along with prions significantly induce miRNA-146a in the infected host, but whether this represents part of the host’s adaptive immunity, innate-immune response or a mechanism to enable the invading prion or virus a successful infection is not well understood. Current findings suggest an early and highly interactive role for miRNA-146a: (i) as a major small noncoding RNA (sncRNA) regulator of innate-immune responses and inflammatory signaling in cells of the human brain and CNS; (ii) as a critical component of the complement system and immune-related neurological dysfunction; (iii) as an inducible sncRNA of the brain and CNS that lies at a critical intersection of several important neurobiological adaptive immune response processes with highly interactive associations involving complement factor H (CFH), Toll-like receptor pathways, the innate-immunity, cytokine production, apoptosis and neural cell decline; and (iv) as a potential biomarker for viral infection, TSE and AD and other neurological diseases in both animals and humans. In this report, we review the recent data supporting the idea that miRNA-146a may represent a novel and unique sncRNA-based biomarker for inflammatory neurodegeneration in multiple species. This paper further reviews the current state of knowledge regarding the nature and mechanism of miRNA-146a in viral and prion infection of the human brain and CNS with reference to AD wherever possible.

What Kaplan-Meier survival curves don't tell us about CNS disease

Central nervous system consequences of viral infections are rare, but when they do occur, they are often serious and clinically challenging to manage. Our awareness of the perils of neuroinvasion by viruses is growing: the recently appreciated impact of Ebola and Zika virus infections on CNS integrity, decreases in vaccination coverage for potentially neurotropic viruses such as measles, and increased neurovirulence of some influenza strains collectively highlight the need for a better understanding of the viral-neural interaction. Defining these interactions and how they result in neuropathogenesis is paramount for the development of better clinical strategies, especially given the limited treatment options that are available due to the unique physiology of the brain that limits migration of blood-borne molecules into the CNS parenchyma. In this perspective, we discuss some unique aspects of neuronal viral infections and immune-mediated control that impact the pathogenic outcomes of these infections. Further, we draw attention to an often overlooked aspect of neuropathogenesis research: that lack of overt disease, which is often equated with survival post-infection, likely only scratches the surface of the myriad ways by which neurotropic infections can impair CNS function.

Gene Editing for Treatment of Neurological Infections

The study of neurological infections by viruses defines the field of neurovirology, which has emerged in the last 30 years and was founded upon the discovery of a number of viruses capable of infecting the human nervous system. Studies have focused on the molecular and biological basis of viral neurological diseases with the aim of revealing new therapeutic options. The first studies of neurovirological infections can be traced back to the discovery that some viruses have an affinity for the nervous system with research into rabies by Louis Pasteur and others in the 1880s. Today, the immense public health impact of neurovirological infections is illustrated by diseases such as neuroAIDS, progressive multifocal leukoencephalopathy, and viral encephalitis. Recent research has seen the development of powerful new techniques for gene editing that promise revolutionary opportunities for the development of novel therapeutic options. In particular, clustered regulatory interspaced short palindromic repeat-associated 9 system provides an effective, highly specific and versatile tool for targeting DNA viruses that are beginning to allow the development of such new approaches. In this short review, we discuss these recent developments, how they pertain to neurological infections, and future prospects.

Innate immune response gene expression profiles in central nervous system of mice infected with rabies virus

The present study was focused on the modulation of innate immune response genes in CNS of mouse in response to rabies virus (RABV) infection. The global gene expression changes in brains of RABV- or mock-infected mice were investigated using DNA microarray analysis and quantitative real-time PCR. Then functional enrichment of the differentially expressed mRNAs was performed. Microarray analysis showed that 390 genes in brain were significantly (P<0.01) regulated in response to RABV infection, with obviously up-regulated genes like interferon (IFN) stimulated genes (ISGs), IFN inducible transcription factors, cytokines and complement, etc. The significant pathways of differentially expressed genes are mainly involved in JAK-STAT signaling pathway, antigen processing and presentation, ubiquitin mediated proteolysis and complement cascades. The results suggest that the modulated genes in infected CNS were possibly involved in pathogenesis of rabies. Conversely, they may have protective effects.

Advances in pediatric neurovirology

Viral infections of the pediatric central nervous system (CNS) encompass a broad spectrum of both perinatally and postnatally acquired diseases with potentially devastating effects on the developing brain. In children, viral infections have been associated with chronic encephalopathy, encephalitis, demyelinating disease, tumors, and epilepsy. Older diagnostic techniques of biopsy, viral culture, electron microscopy, gel-based polymerase chain reaction (PCR), and viral titer quantification are being replaced with more rapid, sensitive, and specific real-time and microarray-based PCR technologies. Advances in neuroimaging technologies have provided for earlier recognition of CNS injury without elucidation of specific viral etiology. Although the mainstay therapy of many pediatric neurovirologic diseases, aside from HIV, includes intravenous acyclovir, much work is being done to develop novel antiviral immunotherapies aimed at both treating and preventing pediatric CNS viral disease.

Neuroimmunology of central nervous system viral infections: the cells, molecules and mechanisms involved

Viral infections of the central nervous system (CNS) necessitate rapid, yet tightly controlled responses to contain viral spread while limiting tissue damage. All CNS resident cell types are equipped with pattern recognition receptors (PRRs) to respond to viruses. The resulting activation of IFN-alpha/beta, pro-inflammatory cytokines and chemokines is dependent on the virus replication strategy, tropism and PRR distribution. Although IFN-alpha/beta induced antiviral mediators are essential to restrict initial viral spread, adaptive immunity promoted by chemokines, cytokines and metalloproteinases is equally crucial in lowering viral burden. Recognition of viral antigen presented by MHC molecules is crucial for T cell retention and function. Non-lytic clearance mechanisms mediated by IFN-gamma and antibodies prevail in providing protection. Targeted intervention can be achieved by PRR stimulation, chemokine-receptor blockade and immune modulation of T cell function. However, owing to the extensive positive and negative feedback signaling cascades linking innate and adaptive immune responses, enhanced anti-viral functions will have to be counterbalanced to avoid pathology.

Lissencephaly 1 linking to multiple diseases: mental retardation, neurodegeneration, schizophrenia, male sterility, and more

Lissencephaly 1 (LIS1) was the first gene implicated in the pathogenesis of type-1 lissencephaly. More than a decade of research by multiple laboratories has revealed that LIS1 is a key node protein, which participates in several pathways, including association with the molecular motor cytoplasmic dynein, the reelin signaling pathway, and the platelet-activating factor pathway. Mutations in LIS1-interacting proteins, either in human, or in mouse models has suggested that LIS1 might play a role in the pathogenesis of numerous diseases such as male sterility, schizophrenia, neuronal degeneration, and viral infections.

Efficacy of nonviral gene transfer in the canine brain

OBJECT

The purpose of this study was to evaluate the gene transfer capability and tolerability of plasmid DNA/polyethylenimine (PEI) complexes in comparison with adenovirus and naked plasmid DNA in the canine brain.

METHODS

Plasmid or adenoviral vectors encoding firefly luciferase were injected directly into the cerebral parenchyma of five adult dogs at varying doses and volumes. Serial physical and neurological examinations, as well as blood and cerebrospinal fluid (CSF) analyses, were conducted before and after the surgery for 3 days. Three days after gene delivery, a luciferase activity assay and immunofluorescence analysis were used to test the brain tissue for gene expression.

RESULTS

Injection into the brain parenchyma resulted in gene transfer throughout the cerebrum with every vector tested. Luciferase expression was highest when adenovirus vectors were used. Injection of plasmid DNA/PEI complexes and naked DNA resulted in similar levels of luciferase expression, which were on average 0.5 to 1.5% of the expression achieved with adenovirus vectors. Immunofluorescent microscopy analysis revealed that plasmid DNA/PEI complexes transduced mainly neurons, whereas adenovirus transduced mainly astrocytes. No significant acute side effects or neurological complications were observed in any of the dogs. Mononuclear cell counts significantly increased in the CSF after adenovirus injection and modestly increased after injection of plasmid DNA/PEI complexes, suggesting that a mild, acute inflammatory response occurred in the central nervous system (CNS).

CONCLUSIONS

Compared with rodent models that are limited by very small brains, the dog is an excellent preclinical model in which to assess the distribution and safety of emerging gene transfer technologies. In this study, short-term gene transfer was evaluated as a prelude to long-term expression and safety studies. The authors conclude that the viral and nonviral vectors tested were well tolerated and effective at mediating gene transfer throughout a large portion of the canine brain. The nonviral plasmid vectors were less effective than adenovirus, yet they still achieved appreciable gene expression levels. Due to reduced gene transfer efficiency relative to viral vectors, nonviral vectors may be most useful when the expressed protein is secreted or exerts a bystander effect. Nonviral vectors offer an alternative means to genetically modify cells within the CNS of large mammals.

Clinical trials in HIV CNS disease and treatment management

On May 15 and 16, 2006, the National Institute of Mental Health sponsored a workshop designed to facilitate discussion and collaboration between basic and clinical investigators in neuroAIDS. Day 2 of the meeting featured a series of talks by clinical investigators. Three of these (those by J. McArthur, P. Tebas, and C. Flexner) are described in detail here. The remaining four talks (those by R. Ellis, R. Price, S. Letendre, and R. Robertson) are briefly introduced here, and full-length papers may be found elsewhere in this issue of the Journal.

Regulation of Ca2+/calmodulin kinase II inhibitor α (CaMKIINα) in virus-infected mouse brain

The alpha and beta isoforms of rat Ca(2+)/calmodulin kinase II inhibitor (CaMKIINalpha/beta) expressed in brain or brain and testis, respectively, are potent inhibitors of Ca(2+)/calmodulin kinase II (CaMKII) in vitro. However, the regulation or function of CaMKIINalpha/beta in the central nervous system (CNS) is not known. In this study, we demonstrate that mouse CaMKIINalpha gene encodes a 2.9kb brain-specific transcript whose expression is downregulated in mouse brain during Japanese encephalitis virus (JEV) and rabies virus infection. The downregulation is specific for CaMKIINalpha but not CaMKIINbeta mRNA. In addition to these changes in CaMKIINalpha mRNA, distinct changes are also observed in the phosphorylation as well as subcellular localization of CaMKIIalpha leading to an increase in cytosolic CaMKII activity in JEV-infected mouse brain. The differential regulation of CaMKIIalpha and CaMKIINalpha during JEV infection suggests a possible role for these proteins in viral infection and/or virus-induced neuropathogenesis in the CNS.

Altered immune response to CNS viral infection in mice with a conditional knock-down of macrophage-lineage cells

Neuroadapted Sindbis Virus (NSV) is a neuronotropic virus that causes hindlimb paralysis in susceptible mice and rats. The authors and others have demonstrated that though death of infected motor neurons occurs, bystander death of uninfected neurons also occurs and both contribute to the paralysis that ensues following infection. The authors have previously shown that the treatment of NSV-infected mice with minocycline, an inhibitor that has many functions within the central nervous system (CNS), including inhibiting microglial activation, protects mice from paralysis and death. The authors, therefore, proposed that microglial activation may contribute to bystander death of motor neurons following NSV infection. Here, the authors tested the hypothesis using a conditional knock-out of activated macrophage-lineage cells, including endogenous CNS macrophage cells. Surprisingly, ablation of these cells resulted in more rapid death and similar weakness in the hind limbs of NSV-infected animals compared with that of control animals. Several key chemokines including IL-12 and monocyte chemoattractant protein-1 (MCP-1) did not become elevated in these animals, resulting in decreased infiltration of T lymphocytes into the CNS of the knock-down animals. Either because of the decreased macrophage activation directly or because of the reduced immune cell influx, viral replication persisted longer within the nervous system in knock-down mice than in wild type mice. The authors, therefore, conclude that although macrophage-lineage cells in the CNS may contribute to neurodegeneration in certain situations, they also serve a protective role, such as control of viral replication.

High pathogenicity of wild-type measles virus infection in CD150 (SLAM) transgenic mice

Measles virus (MV) infection causes an acute childhood disease, associated in certain cases with infection of the central nervous system and development of a severe neurological disease. We have generated transgenic mice ubiquitously expressing the human protein SLAM (signaling lymphocytic activation molecule), or CD150, recently identified as an MV receptor. In contrast to all other MV receptor transgenic models described so far, in these mice infection with wild-type MV strains is highly pathogenic. Intranasal infection of SLAM transgenic suckling mice leads to MV spread to different organs and the development of an acute neurological syndrome, characterized by lethargy, seizures, ataxia, weight loss, and death within 3 weeks. In addition, in this model, vaccine and wild-type MV strains can be distinguished by virulence. Furthermore, intracranial MV infection of adult transgenic mice generates a subclinical infection associated with a high titer of MV-specific antibodies in the serum. Finally, to analyze new antimeasles therapeutic approaches, we created a recombinant soluble form of SLAM and demonstrated its important antiviral activity both in vitro and in vivo. Taken together, our results show the high susceptibility of SLAM transgenic mice to MV-induced neurological disease and open new perspectives for the analysis of the implication of SLAM in the neuropathogenicity of other morbilliviruses, which also use this molecule as a receptor. Moreover, this transgenic model, in allowing a simple readout of the efficacy of an antiviral treatment, provides unique experimental means to test novel anti-MV preventive and therapeutic strategies.

HIV-TAT protein upregulates expression of multidrug resistance protein 1 in the blood-brain barrier

Central nervous system (CNS) complications of human immunodeficiency virus (HIV) infection remain a serious health risk in HIV/acquired immunodeficiency syndrome despite significant advances in highly active antiretroviral therapy (HAART). Specific drugs used for HAART are substrates for the efflux transport systems, such as the multidrug resistance-associated proteins (MRPs), which are present on brain microvascular endothelial cells (BMEC) and astrocytes, that is, the main cell types that form the blood-brain barrier (BBB). Thus, drugs employed in HAART are actively removed from the CNS and do not efficiently inhibit HIV replication in the brain. To study the potential mechanisms of this process, the aim of the present research was to address the hypothesis that HIV Tat protein can contribute to upregulation of MRP expression at the BBB level. Tat is a protein produced and released by HIV-infected cells, which may play an important role in brain vascular pathology in the course of HIV infection. Among the family of MRPs, exposure to Tat specifically induced MRP1 messenger ribonucleic acid and protein expression both in BMEC and astrocytes. These alterations were accompanied by enhanced MRP1-mediated efflux functions. Furthermore, activation of the mitogen-activated protein kinase signaling cascade was identified as the mechanism involved in Tat-mediated overexpression of MRP1. These results indicate that Tat exposure can lead to alterations of the BBB functions and decrease HAART efficacy in the CNS through overexpression of drug efflux transporters.

Polymerase chain reaction analysis and oligoclonal antibody in the cerebrospinal fluid from 34 patients with varicella-zoster virus infection of the nervous system

OBJECTIVE

To study cerebrospinal fluid (CSF) and serum samples from 34 consecutive patients suspected of having varicella-zoster virus (VZV) infection of the central nervous system (CNS).

POPULATION AND METHODS

The patients were divided into three groups. The first group consisted of 27 patients with a rash in one to three dermatomes and clinical suspicion of meningitis and radiculitis; among them, three subgroups were distinguished according to the affected dermatome: ophthalmicus (n = 9), oticus (n = 11) and cervico-thoraco-lumbar zoster (n = 7). Four cases of zoster sine herpete (ZSH) were included in the second group: these patients presented with either radiculitis (n = 2) or meningoencephalitis (n = 2), without cutaneous eruption. The third group consisted of three patients with a generalised rash and encephalitis. A polymerase chain reaction (PCR) for VZV DNA and antigen-driven immunoblots for oligoclonal anti-VZV antibodies were carried out on all CSF samples.

RESULTS

PCR of the CSF was positive in 44% of the patients from the first group, mainly within the first 7 days after eruption. In addition, intrathecal synthesis of anti-VZV antibodies was detected in 37% of patients, always after an interval of 7 days (p<0.0001). Among the four patients with ZSH, a positive VZV PCR was detected in three patients and CSF-specific oligoclonal anti-VZV antibodies in two. PCR was also positive in the CSF of two of the three patients with generalised rash and encephalitis; local production of anti-VZV antibodies was seen in a second CSF sample in one patient, and was also present in the third patient.

CONCLUSION

Amplification of VZV DNA by PCR in the CSF and antigen-driven immunoblots have important diagnostic value in suspected VZV infection, although their presence depends on the timing of the CSF sampling. VZV is thought to be a causative agent in unexplained cases of meningitis associated with radiculitis or focal CNS symptoms, even in the absence of skin manifestations. In such patients, rapid diagnosis by this combined approach permits early antiviral treatment.

Inverse regulation of inducible nitric oxide synthase (iNOS) and arginase I by the protein tyrosine phosphatase SHP-1 in CNS glia

We have previously shown that the SH2 domain-containing protein tyrosine phosphatase SHP-1 plays a critical role in controlling virus infection in CNS glia in vivo and in vitro. The present study addressed whether increased virus replication in SHP-1-deficient glia in vitro may be a result of altered expression of inducible nitric oxide synthase (iNOS/NOS2). First, we observed a profound reduction in iNOS protein expression and production of nitric oxide (NO) in response to the viral mimic double-stranded RNA (dsRNA), despite the induction of high levels of iNOS mRNA, in SHP-1-deficient motheaten mouse compared to wild type littermate mouse glia. Because both iNOS expression and NO production are suppressed by multiple pathways involving arginase I activity, it was important that we observed abnormally high constitutive expression of arginase I in cultured glia of SHP-1-deficient compared to wild type mice. Further, both constitutive and IL-4/IL-10-induced expression of arginase I correlated with elevated STAT6 nuclear binding activity, decreased NO production, and increased virus replication in motheaten compared to wild type astrocytes. These findings provide the first evidence of an inverse relationship between NO and arginase I activity regulated by SHP-1 in CNS glia that is relevant to modulation of innate anti-viral responses. Thus, we propose that SHP-1 is a critical regulator of innate immunity to virus infections in CNS cells.

Inhibition of interferon-gamma signaling in oligodendroglia delays coronavirus clearance without altering demyelination

Infection of the central nervous system (CNS) by the neurotropic JHM strain of mouse hepatitis virus (JHMV) induces an acute encephalomyelitis associated with demyelination. To examine the anti-viral and/or regulatory role of interferon-gamma (IFN-gamma) signaling in the cell that synthesizes and maintains the myelin sheath, we analyzed JHMV pathogenesis in transgenic mice expressing a dominant-negative IFN-gamma receptor on oligodendroglia. Defective IFN-gamma signaling was associated with enhanced oligodendroglial tropism and delayed virus clearance. However, the CNS inflammatory cell composition and CD8(+) T-cell effector functions were similar between transgenic and wild-type mice, supporting unimpaired peripheral and CNS immune responses in transgenic mice. Surprisingly, increased viral load in oligodendroglia did not affect the extent of myelin loss, the frequency of oligodendroglial apoptosis, or CNS recruitment of macrophages. These data demonstrate that IFN-gamma receptor signaling is critical for the control of JHMV replication in oligodendroglia. In addition, the absence of a correlation between increased oligodendroglial infection and the extent of demyelination suggests a complex pathobiology of myelin loss in which infection of oligodendroglia is required but not sufficient.

Prenatal viral infection in mouse causes differential expression of genes in brains of mouse progeny: a potential animal model for schizophrenia and autism

Schizophrenia and autism are neurodevelopmental disorders with genetic and environmental etiologies. Prenatal viral infection has been associated with both disorders. We investigated the effects of prenatal viral infection on gene regulation in offspring of Balb-c mice using microarray technology. The results showed significant upregulation of 21 genes and downregulation of 18 genes in the affected neonatal brain homogenates spanning gene families affecting cell structure and function, namely, cytosolic chaperone system, HSC70, Bicaudal D, aquaporin 4, carbonic anhydrase 3, glycine receptor, norepinephrine transporter, and myelin basic protein. We also verified the results using QPCR measurements of selected mRNA species. These results show for the first time that prenatal human influenza viral infection on day 9 of pregnancy leads to alterations in a subset of genes in brains of exposed offspring, potentially leading to permanent changes in brain structure and function.

Measles virus infection induces chemokine synthesis by neurons

The role that neurons play in the induction of the immune response following CNS viral infection is poorly understood, largely owing to the belief that these cells are immunologically quiescent. In this report, we show that virus infection of neurons results in the synthesis of proinflammatory chemokines, which are early and important mediators of leukocyte recruitment to sites of viral infection. For these studies, a transgenic mouse model of neuron-restricted measles virus (MV) infection was used. Inoculation of immunocompetent and immunodeficient transgenic adult mice resulted in CNS induction of the mRNAs encoding IFN-gamma inducible protein of 10 kD, monokine inducible by gamma and RANTES. Colocalization of chemokine proteins with MV-infected neurons was detected by immunofluorescence in infected brain sections. Both IFN-gamma inducible protein 10 kD and RANTES were also induced in MV-infected primary hippocampal neurons cultured from transgenic embryos, as shown by RNase protection assay, confocal microscopy, and ELISA. Interestingly, neuronal infection with another RNA virus (lymphocytic choriomeningitis virus) was not associated with induction of these chemokines. In immunocompetent mice, chemokine synthesis preceded the infiltration of T lymphocytes, and chemokine ablation by neutralizing Abs resulted in a 20-50% reduction in the number of infiltrating lymphocytes. Collectively, these data indicate that neurons play an important role in the recruitment of a protective antiviral response to the CNS following viral infection, although such a role may be virus type-dependent.

BAK alters neuronal excitability and can switch from anti- to pro-death function during postnatal development

BAK is a pro-apoptotic BCL-2 family protein that localizes to mitochondria. Here we evaluate the function of BAK in several mouse models of neuronal injury including neuronotropic Sindbis virus infection, Parkinson's disease, ischemia/stroke, and seizure. BAK promotes or inhibits neuronal death depending on the specific death stimulus, neuron subtype, and stage of postnatal development. BAK protects neurons from excitotoxicity and virus infection in the hippocampus. As mice mature, BAK is converted from anti- to pro-death function in virus-infected spinal cord neurons. In addition to regulating cell death, BAK also protects mice from kainate-induced seizures, suggesting a possible role in regulating synaptic activity. BAK can alter neurotransmitter release in a direction consistent with its protective effects on neurons and mice. These findings suggest that BAK inhibits cell death by modifying neuronal excitability.

Perforin-mediated effector function within the central nervous system requires IFN-gamma-mediated MHC up-regulation

CD8(+) T cells infiltrating the CNS control infection by the neurotropic JHM strain of mouse hepatitis virus. Differential susceptibility of infected cell types to clearance by perforin or IFN-gamma uncovered distinct, nonredundant roles for these antiviral mechanisms. To separately evaluate each effector function specifically in the context of CD8(+) T cells, pathogenesis was analyzed in mice deficient in both perforin and IFN-gamma (PKO/GKO) or selectively reconstituted for each function by transfer of CD8(+) T cells. Untreated PKO/GKO mice were unable to control the infection and died of lethal encephalomyelitis within 16 days, despite substantially higher CD8(+) T cell accumulation in the CNS compared with controls. Uncontrolled infection was associated with limited MHC class I up-regulation and an absence of class II expression on microglia, coinciding with decreased CD4(+) T cells in CNS infiltrates. CD8(+) T cells from perforin-deficient and wild-type donors reduced virus replication in PKO/GKO recipients. By contrast, IFN-gamma-deficient donor CD8(+) T cells did not affect virus replication. The inability of perforin-mediated mechanisms to control virus in the absence of IFN-gamma coincided with reduced class I expression. These data not only confirm direct antiviral activity of IFN-gamma within the CNS but also demonstrate IFN-gamma-dependent MHC surface expression to guarantee local T cell effector function in tissues inherently low in MHC expression. The data further imply that IFN-gamma plays a crucial role in pathogenesis by regulating the balance between virus replication in oligodendrocytes, CD8(+) T cell effector function, and demyelination.

Differences in the activation of the GFAP gene promoter by prion and viral infections

The expression of glial fibrillary acidic protein (GFAP), a component of astroglial intermediate filaments, is regulated under developmental and pathological conditions. After surgical injury or viral infections, an increase in this protein reflects reactive gliosis in the brain. We analyzed the activation of the GFAP gene in transgenic mice using a prion and two different viruses (rabies and Theiler viruses). Inoculation of the transgenic mice with the C506M3 mouse prion strain resulted in activation of the GFAP-lacZ transgene. Expression of the GFAP transgene increased concomitantly with the expression of GFAP in astrocytes from the infected mice. In contrast, infection with rabies or Theiler's virus had no effect on the expression of the GFAP transgene, showing that the glial reactions to these infectious agents involved different mechanisms. These findings indicate that the activation of the endogenous GFAP gene as a consequence of viral infection could involve different regulatory pathways than activation as a result of prion infection. The first 2 kb upstream from the start codon of the GFAP gene seems to provide enough activation domains to produce efficient activation of the reporter gene in prion-infected mice.

[Prospects for gene treatment in paediatric neurology]

INTRODUCTION

The current advances in the field of human genetics allow for the development of alternative therapies for the treatment of diseases affecting the central nervous system (CNS). One of the most promising new therapies is the use of therapeutic genes or gene therapy.

OBJECTIVE

To briefly review the recent advances for the treatment of diseases affecting the CNS.

DEVELOPMENT

We consider the therapeutic strategies currently in study for gene therapy of diseases with neurologic symptoms as monogenic diseases, CNS malignancies and neurodegenerative diseases. We describe the pros and cons of viral, non viral vectors and cell based therapy.

CONCLUSIONS

The current gene therapy approaches allow for specific and efficient administration of therapeutic genes to the CNS. Despite the need of optimization of the available vectors, mainly regarding to safety and efficacy, gene therapy has an important potential for the treatment of neuropediatric diseases.

Molecular basis of treatment in motor neurone disease

The pathways leading to motorneuron degeneration in amyotrophic lateral sclerosis (ALS) are complex. Excitotoxicity, oxidative damage and, maybe, abnormal aggregation of neurofilaments are key events on which therapeutical strategies can be designed. This paper reviews current knowledge on these strategies. Even though we should be aware that appropriate management of disease symptoms remains the most effective therapeutical intervention, understanding the pathophysiology of ALS is essential for developing new therapies.

Polymerase chain reaction in the diagnosis and management of central nervous system infections

Polymerase chain reaction (PCR) is a broadly applied laboratory test for the diagnosis of a wide variety of central nervous system (CNS) diseases, including genetic and autoimmune diseases, malignant neoplasms, and infections. With its ability to detect minute amounts of DNA or RNA contained in tissues or fluids, PCR has improved the rapidity and accuracy of diagnosis, enhanced understanding of pathogenesis, and helped identify infectious causes for diseases previously considered idiopathic. In addition, PCR can be performed on a variety of tissues preserved in different ways--even archival specimens can be used to provide important epidemiological information. By making quick and precise diagnoses, appropriate treatments can be instituted, and unnecessary or invasive investigations can be avoided.