Glycoprotein-mediated induction of apoptosis limits the spread of attenuated rabies viruses in the central nervous system of mice

Induction of apoptosis by rabies virus (RV) has been reported to be associated with the expression of the glycoprotein (G), but inversely correlated with pathogenicity. To further delineate the association between the expression of the G and the induction of apoptosis, recombinant RVs with replacement of only the G gene were used to infect mice by the intracerebral route. Recombinant viruses expressing the G from attenuated viruses expressed higher level of the G and induced more apoptosis in mice than recombinant RV expressing the G from wild-type (wt) or pathogenic RV, demonstrating that it is the G gene that determines the level of G expression and, consequently, the induction of apoptosis. Likewise, recombinant viruses expressing the G from wt or pathogenic RV are more pathogenic in mice than those expressing G from attenuated RV, confirming the inverse correlation between RV pathogenicity and the induction of apoptosis. To investigate the mechanism by which induction of apoptosis attenuates viral pathogenicity, mice were infected with wt or attenuated RV by the intramuscular route. It was found that low doses of attenuated RV induced apoptosis in the spinal cord and failed to spread to the brain or produce neurological disease. On the other hand, apoptosis was not observed in the spinal cord of mice infected with the same doses of wt RV and the virus spread to various parts of the brain and induced fatal neurologic disease. These results suggest that glycoprotein-mediated induction of apoptosis limits the spread of attenuated rabies viruses in the central nervous system (CNS) of mice.     

Airborne rabies encephalitis: demonstration of rabies virus in the human central nervous system

A veterinarian contracted rabies in the course of laboratory work with homogenates of rabid goat brain. Epidemiologic study determined a respiratory mode of transmission. After a fulminant encephalitic illness, formed rabies virions were identified in the synaptic zones of the olfactory glomeruli. Identification, isolation, experimental disease production, and tissue cytopathic effects of virus recovered from the brain fulfilled Koch's postulates in this unusual instance of virus disease of the nervous system.     

Treating autoimmune demyelination by augmenting lymphocyte apoptosis in the central nervous system

The elimination of autoreactive T cells from the central nervous system (CNS) by apoptosis plays an important role in switching off autoimmune attack. B-cell apoptosis in the CNS probably also has a key role in downregulating autoimmunity. Augmenting lymphocyte apoptosis in the CNS is a potential strategy for treating autoimmune CNS diseases such as multiple sclerosis. These strategies involve modulation of the physiological pro-apoptotic and anti-apoptotic pathways that control lymphocyte fate in the CNS. In the case of T cells, apoptosis can be augmented by enhancing activation-induced T-cell apoptosis through the CD95 (Fas) pathway and by inhibiting costimulation-induced anti-apoptotic pathways mediated through BCL-2 and BCL-X L.     

Early events in rabies virus infection of the central nervous system in skunks (Mephitis mephitis)

Twenty-four striped skunks were inoculated intramuscularly (long digital extensor muscle of right pelvic limb) with street rabies virus. Groups of two clinically normal skunks were killed at various times after inoculation; skunks that developed rabies were killed in early stages of the clinical signs. Four clinically normal skunks (numbered 1–4) had slight infection in lumbar spinal ganglia, spinal cord and brain. These four skunks were used for detailed immunohistochemical (rabies antigen) studies that included examination of sections from every segment of the spinal cord, most of the spinal ganglia from the 2nd cervical to the 2nd coccygeal (sections at 25-μm intervals of lumbar, sacral and coccygeal ganglia) and brain (sections at 50-μm intervals). In skunks 1–4, there was increasing distribution of antigen-containing neurons that was not correlated with the time elapsed since inoculation. In three skunks (nos. 1, 2 and 3), antigen-containing neurons were predominantly in caudal regions of the spinal cord, caudal right lumbar and sacral spinal ganglia and certain nuclei/regions of the brain (medial reticular formation, right interpositus and lateral vestibular nuclei, left red nucleus, left motor cortex, and left reticular nucleus of the thalamus). Skunk 4 had more extensive infection than skunks 1–3, but the previous pattern was still evident. The results are consistent with viral entrance into the lumbar spinal cord, initial replication mainly at the L2 and L3 levels, local spread in the cord by propriospinal neurons and early transit to the brain via long ascending and descending fiber tracts (bypassing the grey matter of the rostral spinal cord). These mechanisms could provide for early and rapid dissemination in the brain before a significant immune response develops and could induce behavioral changes before the animal is incapacitated by extensive spinal cord infection. Based on the distribution of antigen-containing neurons, the tracts considered most likely to serve as viral transitways from spinal cord to brain include: rubrospinal, corticospinal, spinothalamic, spino-olivary, vestibulospinal and/or spinovestibular, reticulospinal and/or spinoreticular, cerebellospinal and/or spinocerebellar, and dorsal column pathways. Received: 21 April 1995 / Revised: 24 July 1995 / Accepted: 2 August 1995     

Inhibition of the transport of rabies virus in the central nervous system

The effect of colchicine, an inhibitor of axonal transport, on the spread of rabies virus in the central nervous system was investigated using Wistar rats. Colchicine was inoculated into the striatum at various times before and after inoculation of rabies virus into the same site. Rats were killed at various times after viral inoculation and the spread of rabies virus was monitored by rabies immunofluorescence of selected areas of brain. The most effective inhibitory effect was obtained by colchicine treatment applied two days before virus inoculation. Under these conditions, no fluorescent foci could be detected until day 3 post-infection whereas control rats exhibited infected cells as soon as two days post-infection. This inhibitory effect is reversible and the general consequence seems to be a delay in the rate of viral spread. However, five days after the virus challenge, some major brain areas were still partially preserved from infection (striatum, frontal cortex, pyriform cortex). Ten days after colchicine treatment, the microtubules have recovered their capacity to transport the virus. At the onset of paralysis, the general pattern of infection in brain sections from colchicine-treated rats was not significantly different from that of control rats. This inhibitory effect on the transport of rabies virus can be prolonged by administration of additional colchicine.     

Early T cell response in the central nervous system in canine distemper virus infection

The initial demyelinating lesions in canine distemper virus (CDV) infection develop during a period of severe immunosuppression in the absence of inflammation. In vitro and in vivo studies suggest that early demyelination is due to directly virus-induced oligodendroglial changes. In the present spatiotemporal study in experimentally CDV-infected dogs we observed diffuse up-regulation of T cells throughout the central nervous system (CNS) and T cell invasion in early demyelinating lesions. Invasion of T cells in the CNS occurred despite severe immunosuppression and without any perivascular cuffing. However, the major fraction of invading T cells correlated with sites of viral replication and coincided with the demonstration of an early immune response against the nucleocapsid protein of CDV. Activation of microglial cells was thought to have elicited the migration of T cells to the CNS by secretion of chemokines: marked IL-8 activity was found in the CSF of dogs with acute lesions. In areas of early demyelination, large numbers of CD3⁺ cells accumulated in the tissue in the absence of any morphological sign of inflammation. Whether the T cells at lesion sites contribute to the development of acute demyelination remains uncertain at this stage. Antiviral cytotoxicity was not apparent since viral clearance in demyelinating lesions is only effective when B cells and concurring antiviral antibody production appeared in the subacute and chronic inflammatory stage of the disease. CD3⁺ cells appear to persist for several weeks after infection since they were also found in recovered dogs that did not develop demyelination. Accumulation of immune cells, including a significant proportion of resting T cells (CD45RA⁺) in the CNS in the early stages of the disease may facilitate the later development of the intrathecal immune response and associated immunopathological complications. Received: 16 March 1998 / Revised, accepted: 6 July 1998     

Axonal transport of rabies virus in the central nervous system of the rat

Stereotaxic inoculation of rabies virus into specific nuclei in the central nervous system has been used for the investigation of the central neural transport mechanisms of viral information. The infection was monitored by specific fluorescence and peroxidase studies and the titration of viral infectivity in dissected brain areas. Twenty-four hours after inoculation into the striatum, cortex, or substantia nigra, infected neurons were detected only in cells from areas and nuclei which were related to the site of inoculation. The distribution of infected neurons showed that retrograde axoplasmic flow plays a determining role in the transport of rabies virus 24 hours after delivery of virus to specific target nuclei. Local destruction of neurons by kainic acid at the site of viral inoculation did not prevent the uptake and subsequent retrograde axonal transport of virus. There was an overall correlation between the major neural connections of the inoculated areas (e.g. the striatum) and the infected areas 24 hours later (e.g. the substantia nigra).     

On the replication and spread of rabies virus in the human central nervous system

Ultrastructural and immunohistochemical studies on the brains of two autopsy cases of human rabies revealed: By the peroxidase-antiperoxidase method, viral antigens were present in all eosinophilic inclusions detected in formalin fixed paraffin sections. Numerous antigenic masses, which apparently corresponded to the matrices and cylindrical particles in neurites revealed by electron microscopy, were present in the neuropil remote from neuronal perikarya. There were virions in the intercellular spaces and virus-budding from the plasma membrane into the extracellular space in the absence of a matrix, strongly indicating that rabies virus in the human central nervous system could spread through the intercellular spaces and that the replication of the virus was not necessarily accompanied by the formation of inclusion bodies. The synapse was involved in rabies as indicated by virions in the synaptic terminals. The implications of these observations are discussed in conjunction with the results of previous in vitro and animal experiments.     

Differential induction of apoptosis in demyelinating and nondemyelinating infection by mouse hepatitis virus

The role of apoptosis in mouse hepatitis virus (MHV) infection is still controversial. To better assess the role of apoptosis in MHV infection, we used three different biologic phenotypes of MHV to examine their differential effect on the induction of apoptosis. MHV-A59 produces acute hepatitis, meningoencephalitis, and chronic demyelination. MHV-2 causes only acute hepatitis and meningitis, whereas Penn98-1 produces acute hepatitis and meningoencephalitis without demyelination. We detected TdT-mediated dUTP nick-end labeling (TUNEL) staining in the livers and meninges of MHV-A59-, MHV-2-, and Penn98-1-infected mice. TUNEL staining in brain parenchyma was only detected in MHV-A59- and Penn98-1-infected mice. We detected apoptosis by electronmicroscopy in olfactory neurons during acute infection with MHV-A59. The kinetics and distribution of TUNEL staining correlated with the pathologic damage and colocalized with viral antigen in some cells. At 1 month, TUNEL staining was found exclusively in areas of demyelination in the spinal cord of MHV-A59-infected mice; however, it was not found in nondemyelinated mice infected with MHV-2 or Penn98-1, or in mock-infected mice. TUNEL-positive cells were identified as macrophage/microglial cells, some astrocytes, and some oligodendrocytes, by colabeling with cell-specific markers. The presence of TUNEL staining in oligodendrocytes suggests that apoptosis may play an important role in MHV-induced demyelination.     

Lipopolysaccharide-induced tumor necrosis factor-alpha release is controlled by the central nervous system.

OBJECTIVE: Lipopolysaccharide (LPS) injection in mammals orchestrates the release of many proinflammatory and anti-inflammatory cytokines. Intravenous administration of 0.2 mg/kg of LPS into unanesthetized rats with indwelling jugular catheters provoked a rapid, 50-fold increase in plasma tumor necrosis factor (TNF)-alpha within 30 min, which declined by 60% by 120 min. To test our hypothesis that such a rapid increase of TNF-alpha would be either neurally or hormonally controlled, the effect on TNF-alpha release of anesthesia (ketamine/acepromazine/xylazine) and catecholaminergic agonists and antagonists, either alone or in the presence of LPS, was determined. METHODS: Rats bearing indwelling external jugular catheters were injected with the test drug or saline after removal of 0.6 ml of blood (-10 min). At time zero, LPS or saline was administered. Thereafter, blood samples were drawn at 15, 30, 120, 240 and 360 min. TNF-alpha was measured by immunoassay. RESULTS: Among all the drugs tested, only propranolol increased plasma TNF-alpha. Anesthesia significantly blunted the LPS-induced TNF-alpha peak by 50%. Isoproterenol, a beta-adrenergic agonist, also blocked LPS-induced TNF-alpha release by 70% at 30 min and 90% at 120 min. On the contrary, propranolol, a beta-receptor blocker, induced a highly significant 3-fold increase in plasma TNF-alpha concentrations at 30 min and augmented the response to LPS 2-fold after endotoxin injection. Phentolamine, an alpha-receptor blocker, decreased the LPS-induced TNF-alpha release by 57% at 30 min. Similarly, alpha-bromoergocryptine, a dopamine D2 receptor agonist, decreased the LPS-induced TNF-alpha peak by 70% at 30 min and 50% at 120 min. CONCLUSIONS: We conclude that TNF-alpha is at least in part neurally controlled since the anesthetic blocked its response to LPS. The fact that isoproterenol decreased the LPS-induced TNF-alpha release, whereas propranolol augmented basal and LPS-induced release suggests that the sympathetic nervous system inhibits basal and LPS-stimulated TNF-alpha release via beta-adrenergic receptors. Since phentolamine blocked LPS-induced release, this release may be induced, in part at least, by LPS-stimulated adrenergic drive acting on alpha-adrenergic receptors. The suppressive action of bromoergocryptine, a dopamine D2 receptor agonist, on LPS-induced TNF-alpha release may be mediated in part by suppression of prolactin release, which triggers TNF-alpha release.     

Serine residues at positions 162 and 166 of the rabies virus phosphoprotein are critical for the induction of oxidative stress in rabies virus infection

Our previous work in a mouse model of experimental rabies showed neuronal process (dendrites and axons) degeneration in association with severe clinical disease. Cultured adult rodent dorsal root ganglion (DRG) neurons infected with the challenge virus standard-11 (CVS) strain of rabies virus (RABV) showed axonal swellings and reduced axonal growth with evidence of oxidative stress. We have shown that CVS infection alters a variety of mitochondrial parameters and increases mitochondrial complex I activity and reactive oxygen species (ROS) production. Expression of a peptide from amino acid 139–172 of the CVS phosphoprotein (P) increased complex I activity and ROS generation similar to expression of the entire P. Site-directed mutational analyses illustrated the importance of the 145–151 and 157–169 regions of P and that serine residues at 162 and 166 are important single amino acid sites. Two CVS recombinant viruses with serine to alanine mutations at positions 162 (A162r) and 166 (A166r) did not increase complex I activity or ROS generation and also did not induce axonal swellings or inhibit axonal growth in DRG neurons. RABV infection is a mitochondrial disorder initiated by interaction of the RABV P and complex I; S162 and S166 are critical sites in the P for this interaction. The resulting mitochondrial dysfunction produces oxidative stress in neurons causing acute degenerative changes affecting neuronal processes resulting in a severe and fatal clinical disease. This information will be important for the future development of novel therapies for rabies.     

Recurrent demyelination in chronic central nervous system infection produced by Theiler's murine encephalomyelitis virus

A morphologic study of demyelination produced by Theiler's encephalomyelitis virus (TMEV) infection in C3H/He mice was performed. Demyelination in this strain of mouse was less intense and had a milder gliomesodermal response than that observed in SJL mice. As early as 80 days after infection numerous remyelinated axons were present in C3H/He mice, and later, extensive remyelination was observed and was mainly by Schwann cells. About one-third of remyelinated plaques showed recurrent demyelinating activity at 200 days. The best evidence of recurrent demyelination was the loss of myelin by abons which had been previously remyelinated by Schwann cells. In addition, acute areas of demyelination were also seen in spinal cords which contained chronic or quiescent plaques. The demonstration of recurrent demyelination in TMEV infection is important for it increases the relevance of this model to multiple sclerosis (MS). In addition TMEV infection of C3H/He mice appears to be an excellent model for further studies of Schwann cell remyelination and recurrent demyelination in the central nervous system (CNS).     

Endogenous gamma interferon produced in central nervous system by systemic infection infection with Theiler's virus in mice

Theiler's virus GD VII strain causes acute encephalomyelitis by intracerebral inoculation. We established acute encephalomyelitis in mice by the intravenous (i.v.) inoculation of Theiler's virus GD VII strain. Replication of Theiler's virus injected i.v. could be observed in both the brain and spinal cord of mice, and interferon (IFN)-γ could be detected in the extracts of brain and spinal cord in parallel with viral replication. Furthermore, by the injection of anti-IFN-γ monoclonal antibody (mAb) on Day 1 post-infection (p.i.), mortality and virus titres in the spinal cord increased compared with the control mice treated with normal rat globulin. The histological exacerbation of inflammation was observed in spinal cord of anti-IFN-γ mAb-treated mice. These results indicate that endogenous IFN-γ, produced locally in the brain and spinal cord of mice through both antiviral action and anti-inflammatory action of IFN-γ in central nervous system, plays an important role in Theiler's virus infection.     

JC virus infection and lympho-plasmocytic infiltration of the central nervous system revealed by a cerebellar syndrome

We report the case of a 74 year-old woman who had been treated since 8 years for a Waldenstr?m's disease. She also was affected by a progressive multi-focal leukoencephalopathy. The interest of this case lies in two principal features. On the one hand, the clinical and radiological signs were restricted to the cerebellum and to the brainstem, on the other hand, brain examination revealed lymphocytes and plasma cells infiltration suggestive of an associated Bing and Neel syndrome.     

Enhancement of central nervous system pathology in early simian immunodeficiency virus infection by dopaminergic drugs

Human immunodeficiency virus infection (HIV) at late stages of the disease is accompanied by neurological complications, including motor, behavioral and cognitive impairment. Using simian immunodeficiency virus (SIV)-infected rhesus monkeys, an animal model of HIV infection, we found that during the asymptomatic SIV infection dopamine (DA) deficits are early components of central nervous system (CNS) dysfunction. To investigate the role of the DA system in SIV infection and to restore the DA deficiency, we administered selegiline, an agent with DAergic and neuroprotective properties, to SIV-infected monkeys. Selegiline increased DA availability but induced CNS vacuolization, SIV encephalitic lesions, and enhanced CNS viral replication during early SIV infection. The pathological changes seem to be mediated by DA, as treatment with L-DOPA, the precursor of DA, had similar effects. We propose that any natural or induced DAergic dysregulation which results in increased DA availability may potentiate HIV-associated neurological disease (ND). Our findings raise new questions regarding the pathogenesis of HIV-ND and generate concerns about the safety of dopaminergic drugs in the clinical management of HIV-infected patients.     

Persistence of Theiler's virus infection following promotion of central nervous system remyelination

Chronic infection of SJL/J mice with the Daniel's strain of Theiler's virus develop primary demyelination, viral persistence but minimal central nervous system (CNS)-type remyelination. In contrast, treatment of virus-infected mice with sera or immunoglobulin G (IgG) from mice immunized with homogenized spinal cord (SCH) emulsified in incomplete Freund's adjuvant promotes CNS remyelination. We measured levels of infectious virus, virus antigen and virus-specific antibody to determine if treatments which promote CNS remyelination are able to modulate infection. Levels of virus-specific antibody were higher in mice treated with SCH/IgG than control treatment groups and correlated positively with extent of remyelination. Although number of virus antigen-positive cells in spinal cord was less in mice treated with SCH/IgG than mice treated with phosphate buffered saline (PBS)/IgG, there was only a slight negative correlation with extent of remyelination by regression analysis. Titers of infectious virus isolated three to six months following infection were not different among treatment groups. Even though treatment of mice with SCH/IgG reduced number of virus antigen-positive cells and enhanced levels of virus-specific antibody, CNS remyelination can occur despite presence of infectious virus.     

Involvement of the central nervous system in patients with dengue virus infection

The findings of a neurological evaluation in 85 patients with confirmed, acute, dengue virus infection are described. Signs of central nervous system involvement were present in 18 patients (21.2%). The most frequent neurological symptom was mental confusion. The frequency of neurological involvement did not differ between patients with primary and secondary dengue infection, and the prevalence of central nervous system involvement in dengue fever and dengue hemorrhagic fever also did not differ significantly. The presence of CNS involvement did not influence the prognosis of dengue infection. Dengue viral CSF RNA was found in 7 of 13 patients submitted to a spinal tap, the CSF viral load being less than 1000 copies/ml. PCR was negative in serum samples obtained from three patients on the same day as the CSF samples, suggesting that the dengue virus actively enters the CNS and that the presence of the virus in the CNS does not result from passive crossing of the blood-brain barrier.     

Regional distribution of rabies viral antigen in central nervous system of human encephalitic and paralytic rabies

We studied the distribution of rabies viral antigen in the brain and spinal cord of 7 patients with rabies by immunohistochemical techniques. Four patients presented with encephalitis, the remaining 3 had paralysis. Neither the rabies viral antigen distribution nor inflammation paralleled clinical presentations. Patients who had survival times of 7 days or less (4/7) had a greater amount of antigen-positive neurons in brainstem and spinal cord regardless of the clinical type. Neuroglial cells were also found to contain rabies antigen. Our findings suggest that virus localization may not account for the difference in clinical manifestations.     

Facial palsy and central nervous system infection with varicella virus following adult chickenpox

INTRODUCTION: VZV virus-related peripheral neuropathies usually occur after shingles in adults and more rarely after chickenpox in childhood. CASE REPORT: A 54-year-old patient presented with a right VIIth nerve palsy following a chickenpox rash and recovered after antiviral treatment. CSF analysis revealed lymphocytic meningitis and the virus was identified by PCR. CONCLUSIONS: Although previous chickenpox was not found in the patient's past history, the probability of reinfection is likely. The virus can be assumed to affect the nervous system directly; the axonal or demyelinating mechanism of the neuropathy may be discussed.