Role of cytokines and chemokines in prion infections of the central nervous system

Prion infections of the central nervous system (CNS) are characterised by a reactive gliosis and the subsequent degeneration of neuronal tissue. The activation of glial cells, which precedes neuronal death, is likely to be initially caused by the deposition of misfolded, proteinase K-resistant, isoforms (termed PrP(res)) of the prion protein (PrP) in the brain. Cytokines and chemokines released by PrP(res)-activated glia cells may contribute directly or indirectly to the disease development by enhancement and generalisation of the gliosis and via cytotoxicity for neurons. However, the actual role of prion-induced glia activation and subsequent cytokine/chemokine secretion in disease development is still far from clear. In the present work, we review our present knowledge concerning the functional biology of cytokines and chemokines in prion infections of the CNS.

Role of microglia in central nervous system infections

The nature of microglia fascinated many prominent researchers in the 19th and early 20th centuries, and in a classic treatise in 1932, Pio del Rio-Hortega formulated a number of concepts regarding the function of these resident macrophages of the brain parenchyma that remain relevant to this day. However, a renaissance of interest in microglia occurred toward the end of the 20th century, fueled by the recognition of their role in neuropathogenesis of infectious agents, such as human immunodeficiency virus type 1, and by what appears to be their participation in other neurodegenerative and neuroinflammatory disorders. During the same period, insights into the physiological and pathological properties of microglia were gained from in vivo and in vitro studies of neurotropic viruses, bacteria, fungi, parasites, and prions, which are reviewed in this article. New concepts that have emerged from these studies include the importance of cytokines and chemokines produced by activated microglia in neurodegenerative and neuroprotective processes and the elegant but astonishingly complex interactions between microglia, astrocytes, lymphocytes, and neurons that underlie these processes. It is proposed that an enhanced understanding of microglia will yield improved therapies of central nervous system infections, since such therapies are, by and large, sorely needed.

[Soluble CD4 antigens in the cerebrospinal fluid as a marker of lymphocytic infiltration of the central nervous system]

Early diagnosis of the central nervous system (CNS) infections is a precondition of their successful treatment. However, the essential standard examination of the cerebrospinal fluid (CSF) is sometimes neither specific enough to define their basic nature, nor sufficient to differentiate them from processes of non-infectious origin. Supposing that the released surface molecules of activated immunocompetent cells could better define the character of inflammatory reaction, the levels of soluble CD4 antigens (sCD4) were determined with enzyme-immunosorbent test in the CSF of the patients with various CNS diseases. In contrast to cerebrovascular insults, toxic-metabolic, and other conditions in control group, detectable sCD4 concentrations in acute encephalitis (24 +/- 11 U/ml) were verified at the beginning of the disease, being also present in cytologically diagnosed normal CSF findings. They were significantly higher (p<0.05) compared to acute serous meningitis (13.5 +/- 8 U/ml), while in purulent meningitis they were measurable only after the disease progression--in correlation with the disturbed brain system function. The obtained results suggested the significance of CD4 antigen levels in CSF as a sensitive and specific marker of lymphocytic infiltration of the brain parenchyma, the measurement of which could contribute to early identification of the CNS infections, better understanding of their pathogenesis, and the assessment of the actual level of the destruction of neurons.

Monoamine oxidase inhibition and CNS immunodeficiency infection

HIV invades CNS subcortical areas, particularly the dopamine-rich basal ganglia and induces a subcortical dementia. Data suggest that the basal ganglia dysfunction plays a critical role in the neuropsychiatric manifestation of HIV infection. Therefore, therapeutic approaches for HIV dementia nowadays wish to include apart from the highly active antiretroviral therapy (HAART) also adjunctive medication. In this short article, we report briefly on neurotoxicity associated with the immunodeficiency virus and discuss the effects of selegiline, a monoamine oxidase inhibitor which enhances dopamine availability in CNS on immunodeficiency virus-induced neurological disease.

Discriminatory features of acute transverse myelitis: a retrospective analysis of 45 patients

Acute transverse myelitis (ATM) is a pathogenetically heterogeneous inflammatory disorder of the spinal cord. Therefore, the identification of clinical and paraclinical features providing clues of the underlying etiologies is needed. The clinical presentation, blood and cerebrospinal fluid (CSF) findings as well as magnetic resonance imaging (MRI) and neurophysiological features were retrospectively analyzed in 45 unselected consecutive patients with ATM. Parainfectious ATM was diagnosed in 38% of patients. The underlying infectious agent, however, was identified only in a minority of patients. In 36% of patients, the etiology remained uncertain ("idiopathic" ATM) and in 22% ATM was the first manifestation of possible multiple sclerosis (ATM-MS) according to recently published diagnostic criteria. Spinal cord MRI showed signal alterations in 96% of the patients. In ATM-MS, monosegmental involvement of the spinal cord was most frequent while spinal cord involvement of two or more segments was more common in ATM of other etiologies. Of particular note, neurophysiological examinations showed evidence of peripheral nervous system (PNS) involvement in 27% of patients with ATM but not in patients with ATM-MS. Therefore, neurophysiological evidence of PNS involvement may provide additional discriminatory features between ATM-MS and ATM of other etiologies.

Recurrent cerebral fever in the seventeenth and twenty first centuries

The development of modern neuroscience away from the concepts of Hippocrates and Galen can be traced to the writings of some 17th century clinicians, especially Thomas Willis. His exceptional skills in observation and description allow a window into the experiences of our medical forebears. His approach to the management of infection-related coma in a child is amenable to modern interpretation and comparison with modern management because of the clarity of his clinical descriptions. Modern clinicians may benefit from this historical perspective into influences on the origins of neuroscience. The different outcome for a child presenting in the 17th and 21st century encourage grateful reflection on our current privileged position.

Fetal brain infections

INTRODUCTION

Congenital infections can cause severe brain damage. As a result, it is very important to identify them early in their course so that treatment can be administered to the mother, if possible. The role of imaging is to determine the presence, if any, and the extent of brain damage in the infected fetus. Although MRI is most commonly used as an adjunct to sonography, when clinical suspicion is high in the setting of a normal ultrasound or to better define abnormalities detected by ultrasound, MRI is routinely used in toxoplasmosis seroconversion to definitively rule out brain lesions, even when the ultrasound scan is considered normal. MRI is also used serially throughout the pregnancy to check for the development of brain abnormalities; medical treatment results in excellent clinical outcome if the brain is normal.

DISCUSSION

This article describes the indications, techniques, and findings that will allow proper use of fetal MRI in the setting of congenital infections.

Characteristics and mechanisms of isolated rubella virus, strain JR23: infection of the central nervous system of BALB/c mice

OBJECTIVE

To investigate the correlation between rubella virus (RuV) antigen in peripheral lymphocytes, the immune status and RuV infection in the central nervous system (CNS).

METHODS

BALB/c mice were used as a model and treated with immunoaffecting medicines. Then, the mice were infected with RuV via the abdominal cavity, and the antigen level in peripheral lymphocytes was examined 1, 3, 7 and 14 days postinfection. RuV in the CNS was detected by immunohistochemical methods. BALB/c mice were given dexamethasone and cytoxan before infection with the RuV JR23 strain. Immune functions and RuV invasion of the CNS were assayed on day 21 postinfection via the abdominal cavity, and their relationship was analyzed.

RESULTS

The mean antigen detection rates at different times were 3.1, 4.1, 9.6 and 2.4%, respectively, in the dexamethasone group, and 14.2, 12.7, 9.9 and 3.1%, respectively, in the cytoxan group. In the group without any intervention, the detection rates were 4.63, 10.25, 6.88 and 1.75%, respectively. The antigen detection rates in peripheral lymphocytes among the three groups 24 h postinfection were significantly different (F = 0.0317, p < 0.05). Comparisons between groups showed that antigen detection rates in the cytoxan group were much higher than those in other groups, but there was no difference between the dexamethasone and control groups. The animals with persistent presence of antigen were much more susceptible to cerebral infection than those with short-term presence (p < 0.001). T cell functions of the cytoxan group were significantly lower than those of other groups (p < 0.05), as detected by the MTT method. Infection rates of the dexamethasone, cytoxan and control groups were 60, 90 and 50%, respectively. Cell immune functions of the mice with CNS infection were obviously worse than those of the mice without CNS infection (p < 0.001). RuV-specific antibodies were assayed in all groups by ELISA and the results showed that there were no significant differences among groups (p < 0.05) or between the groups with and without CNS infection.

CONCLUSION

Cytoxan can affect virus detection rates in peripheral lymphocytes. At the early phase of infection, the persistent presence of RuV in peripheral lymphocytes increases the incidence of CNS infection. RuV infection in the CNS was related to the cell immune situation before specific antibody was produced in the body.

The changing pattern of HIV neuropathology in the HAART era

Highly active antiretroviral treatment (HAART), which has been available for most AIDS patients in France since 1996, has resulted in a dramatic improvement of the progression of the disease. From the survey of our series of 343 brains with acquired immunodeficiency syndrome (AIDS) from patients who died between 1985 and 2002, we found both quantitative and qualitative changes in the pattern of human immunodeficiency virus (HIV) neuropathology. Quantitatively, despite a dramatic decrease in the number of autopsies, brain involvement remained a major cause of death. There was an overall decrease in incidence of cerebral toxoplasmosis, cytomegalovirus encephalitis (CMVE), and HIV encephalitis (HIVE), for which successful treatment is available. This contrasted with the unchanged incidence of progressive multifocal leukoencephalopathy (PML) and malignant non-Hodgkin lymphomas (MNHL). However, when looking closer at the 3 last years, the incidence of diseases affecting patients with severe immunodepression (CMVE, PML, and MNHL) decreased between 2000 and 2002, whereas infections occurring in patients with milder immunodeficiency, toxoplasmosis, varicella-zoster encephalitis (VZVE), or herpes simplex virus encephalitis (HSVE) became more frequent. In addition, we found uncommon types of brain infection such as BK virus encephalitis or general paresis. Finally, we described new variants of HIVE: severe leukoencephalopathy with intense perivascular macrophage and lymphocyte infiltration, possibly due to an exaggerated response from a newly reconstituted immune system, and chronic "burnt out" forms of HIVE as VZVE, toxoplasmosis, or PML, possibly associated with prolonged survival, in which neither inflammation nor organisms could be detected. These findings are compared with those reported in other neuropathological studies from different developed countries.

Human herpesvirus 6 genome and antigen in acute multiple sclerosis lesions

Evidence for a candidate multiple sclerosis (MS) virus, human herpesvirus 6 (HHV-6), was sought in biopsy specimens of acute lesions that presented clinically as cerebral tumors obtained from 5 patients. Histopathology, magnetic resonance imaging, and clinical course confirmed the diagnosis of MS in each case. A sensitive in situ polymerase chain reaction (ISPCR) method was used to detect HHV-6 genome, in conjunction with immunocytochemical staining (ICC) to detect viral and cellular antigens. ISPCR revealed numerous oligodendrocytes, lymphocytes, and microglia containing HHV-6 genome within all lesions, whereas ICC showed only the HHV-6 glycoprotein 116 antigen in some reactive astrocytes and microglia. High frequencies of neuroglial and inflammatory cells containing HHV-6 genome were present in acute-phase lesion tissue from patients who were free of the effects of chronic MS and had not been received immunomodulatory therapy for MS. The prevalence of HHV-6 genome-containing cells, including oligodendrocytes, in each lesion suggests that HHV-6 plays a role in the demyelinative pathogenesis of MS; the significance of the discrepant expression of viral antigens remains uncertain.

Broad expression of Toll-like receptors in the human central nervous system

The family of Toll-like receptors (TLRs) plays a key role in controlling innate immune responses to a wide variety of pathogen-associated molecules. In this study we investigated expression of TLRs in vitro by purified human microglia, astrocytes, and oligodendrocytes, and in vivo by immunohistochemical examination of brain and spinal cord sections. Cultured primary microglia were found to express mRNA encoding a wide range of different TLR family members while astrocytes and oligodendrocytes primarily express TLR2 and TLR3. Comparisons between microglia derived from a series of control subjects and neurodegenerative cases indicate distinct differences in levels of mRNA encoding the different TLRs indifferent microglia samples. Interestingly, expression of TLR proteins in cultured microglia as revealed by immunocytochemistry was restricted to intracellular vesicles, whereas in astrocytes they were exclusively localized on the cell surface. Finally, in vivo expression of TLR3 and TLR4 was examined by immunohistochemical analysis of brain and spinal cord sections from both control and multiple sclerosis brains, revealing enhanced expression of either TLR in inflamed CNS tissues. Together, our data reveal broad and regulated expression of TLRs both in vitro and in vivo by human glia cells.

Critical role for protein tyrosine phosphatase SHP-1 in controlling infection of central nervous system glia and demyelination by Theiler's murine encephalomyelitis virus

We previously characterized the expression and function of the protein tyrosine phosphatase SHP-1 in the glia of the central nervous system (CNS). In the present study, we describe the role of SHP-1 in virus infection of glia and virus-induced demyelination in the CNS. For in vivo studies, SHP-1-deficient mice and their normal littermates received an intracerebral inoculation of an attenuated strain of Theiler's murine encephalomyelitis virus (TMEV). At various times after infection, virus replication, TMEV antigen expression, and demyelination were monitored. It was found that the CNS of SHP-1-deficient mice uniquely displayed demyelination and contained substantially higher levels of virus than did that of normal littermate mice. Many infected astrocytes and oligodendrocytes were detected in both brains and spinal cords of SHP-1-deficient but not normal littermate mice, showing that the virus replicated and spread at a much higher rate in the glia of SHP-1-deficient animals. To ascertain whether the lack of SHP-1 in the glia was primarily responsible for these differences, glial samples from these mice were cultured in vitro and infected with TMEV. As in vivo, infected astrocytes and oligodendrocytes of SHP-1-deficient mice were much more numerous and produced more virus than did those of normal littermate mice. These findings indicate that SHP-1 is a critical factor in controlling virus replication in the CNS glia and virus-induced demyelination.

Gliomatosis of the brain and spinal cord masquerading as infective lesions

BACKGROUND

Gliomatosis of the brain or spinal cord is an infiltrating glial neoplasm that shows widespread invasion of the central nervous system with relative sparing of the underlying cytoarchitecture. Acceptance of the idea that the condition represents a distinct entity remains controversial in the absence of conclusive pathogenetic data. The clinico-pathological problems and difficulties in the ante-mortem diagnosis as well as the clinical and pathological similarities to infective lesions are evaluated.

METHODS AND RESULTS

Three cases of cerebral and spinal gliomatosis are presented that clinically mimicked infective lesions and were diagnosed and treated as such. The correct diagnosis in each case was only made at post-mortem examination. The ante-mortem diagnosis of this rare tumor remains difficult owing to poor correlation of clinical, neuroradiological, and neuropathological findings.

CONCLUSION

Gliomatosis of the brain and spinal cord may simulate infective lesions owing to difficulty in ante-mortem diagnosis because of vagueness of physical, radiological, and pathological findings. It is a diagnostic pitfall particularly in our setting where there is a high incidence of HIV/AIDS and patients often present with opportunistic infections such as mycobacterial, fungal, and/or viral infections, which show an atypical clinical picture and radiological findings. Multifocal neurologic deficit with noncontrast enhancing lesions that show diffuse contiguous involvement with overall preservation of the spinal or cerebral architecture and do not respond to infective treatment could suggest a diagnosis of gliomatosis cerebri.

Central and peripheral nervous system infection, immunity, and inflammation in the NHP model of Lyme borreliosis

The relationship between chronic infection, antispirochetal immunity, and inflammation is unknown in Lyme neuroborreliosis. In the nonhuman primate model of Lyme neuroborreliosis, we measured spirochetal density in the nervous system and other tissues by polymerase chain reaction and correlated these values to anti-Borrelia burgdorferi antibody in the serum and cerebrospinal fluid, and to inflammation in tissues. Despite substantial presence of Borrelia burgdorferi, the causative agent of Lyme borreliosis, in the central nervous system, only minor inflammation was present there, though skeletal and cardiac muscle, which contained similar levels of spirochete, were highly inflamed. Anti-Borrelia burgdoferi antibody was present in the cerebrospinal fluid but was not selectively concentrated. All infected animals developed anti-Borrelia burgdorferi antibody in the serum, but increased amplitude of antibody was not predictive of higher levels of infection. These data demonstrate that Lyme neuroborreliosis is a persistent infection, that spirochetal presence is a necessary but not sufficient condition for inflammation, and that antibody measured in serum may not predict the severity of infection.

The National NeuroAIDS Tissue Consortium: a new paradigm in brain banking with an emphasis on infectious disease

The National NeuroAIDS Tissue Consortium (NNTC) was founded in 1998, in response to the scientific need for well-characterized central nervous system (CNS) and peripheral nervous system (PNS) tissues and fluids from HIV-infected individuals. In addition to performing the routine functions of non-transplant anatomic tissue banks, the Consortium offers a unique model for the integration of independent research entities in order to provide well-characterized tissues and fluids for the international research community. Herein, we describe the structure of the Consortium, pointing out the inherent strengths of linking together multiple independent sites for the purpose of banking HIV-infected nervous system tissues. We describe the neuropathology protocol that was adopted and successfully implemented at the four participating banks of the Consortium.

[The neuropathology of neonatal period: analysis of 1616 autopsies]

The lesions of the central nervous system represent an important cause of morbid-mortality in the neonatal period. This is due to the vulnerability of the brain to several adverse conditions during gestation and after birth. This study analyses the prevalence and pattern of central nervous system lesions in neonates autopsied at Hospital de Clínicas - Curitiba. There were 5743 pediatric autopsies performed in the Sector of Anatomic Pathology from 1960 to 1995 with 2049 cases corresponding to death during neonatal period. These later autopsies were reviewed and all cases with central nervous system lesions were selected and classified according to sex, age and pattern of central nervous system lesion. The central nervous system was affected in 1616 (78,87%) of neonatal autopsies and there was predominance of intracerebral hemorrhages (73,39%), congenital malformations (4,27%) and infections (3,59%). The hypoxic hemorrhages are the most prevalent central nervous system lesions in the neonatal period, affecting mainly premature babies. There was predominance of central nervous system malformations in the female neonates.

Cellular mechanisms of microbial proteins contributing to invasion of the blood-brain barrier

One of the least understood issues in the pathogenesis and pathophysiology of microbial infection of the central nervous system (CNS) is how microorganisms cross the blood-brain barrier (BBB), which separates brain interstitial space from blood and is formed by the tight junctions of brain microvascular endothelial cells (BMEC). BMEC monolayer and bilayer culture systems have been developed as in vitro models to dissect the mechanisms of adhesion and invasion involved in pathogenesis of CNS infection caused by microbes. Viral, bacterial, fungal and parasitic pathogens may breach the BBB and enter the CNS through paracellular, transcellular and/or Trojan horse mechanisms. Conceivable evidence suggests that microbial proteins are the major genetic determinants mediating penetration across the BBB. Several bacterial proteins including IbeA, IbeB, AslA,YijP, OmpA, PilC and InlB contribute to transcellular invasion of BMEC. Viral proteins such as gp120 of HIV have been shown to play a role in penetration of the BBB. Fungal and parasitic pathothogens may follow similar mechanisms. SAG1 of Toxoplasma gondii has been suggested as a ligand to mediate host-cell invasion. Understanding the fundamental mechanisms of microbial penetration of the BBB may help develop novel approaches to prevent the mortality and morbidity associated with central nervous system (CNS) infectious diseases.

Rotavirus encephalopathy: pathogenesis reviewed

Two cases of rotavirus gastroenteritis associated with neurological involvement, one with encephalitis (defined by abnormal neurological signs, cerebrospinal fluid (CSF) pleocytosis and detection of rotavirus genomic nucleic acid in the CSF) and one with a non-inflammatory encephalopathy (defined by abnormal neurological signs, an entirely normal CSF and detection of rotavirus genomic nucleic acid in the CSF), are presented and used as a basis to review and explore potential pathogenetic mechanisms, including direct viral replication within neurons and indirect effects of the newly described rotavirus 'enterotoxin'.

[Pathogenetic and morphological characteristics of acute inflammation of the central nervous system]

Virus, bacteria, mycoplasma, protozoa can be the causes of acute neuroinfections. The agents can penetrate into the brain by blood, nerve, lymphatic vessels, from the sinuses directly. Peculiarities of manifestations of acute neuroinfections depend on the agent tropism to receptors of nervous cell and specificity of brain immunoreactivity. The brain injuries can be induced by microorganism action or through immunopathologic processes. Dynamics of morphological changes in acute neuroinfections of different etiology are summarized. Histological, cytological, bacteriological, serological, immunofluorescent, histochemical methods are evaluated. Acute neuroinfection pathogenesis has many unresolved problems.

Contributions of Fas-Fas ligand interactions to the pathogenesis of mouse hepatitis virus in the central nervous system

The pathogenesis of the neurotropic strain of mouse hepatitis virus in Fas-deficient mice suggested that Fas-mediated cytotoxicity may be required during viral clearance after the loss of perforin-mediated cytotoxicity. The absence of both Fas- and perforin-mediated cytolysis resulted in an uncontrolled infection, suggesting a redundancy of cytolytic pathways to control virus replication.

Etiology of microglial nodules in brains of patients with acquired immunodeficiency syndrome

Microglial nodules associated with opportunistic and HIV-related lesions are frequently found in the brains of AIDS patients. However, in many cases, the causative agent is only presumptively suspected. We reviewed 199 brains of AIDS patients with micronodular lesions to clarify their etiology by immunohistochemistry (to Toxoplasma gondii, cytomegalovirus, herpes simplex virus I/II, varicella zoster virus and HIV-p24 core protein), PCR (for herpetic viruses and Mycobacterium tuberculosis) and electron microscopy. Productive HIV infection was observed in 110 cases (55.1%): 30 cases with Toxoplasma gondii encephalitis, 30 with cytomegalovirus encephalitis, eight with multiple cerebral diseases, while in the remaining 42 cases HIV was the only pathogenetic agent. Multinucleated giant cells (hallmark of HIV infection) were found in the MGNs of 85/110 cases with HIV-related lesions; the remaining 25 cases had only p24 positive cells but no multinucleated giant cells. In these latter cases the micronodular lesions had been initially attributed to the main opportunistic agent found in the brain, or defined as subacute encephalitis. Individual microglial nodules positive for an opportunistic pathogen were generally negative for HIV antigens. In 13 cases no opportunistic agent or HIV productive infection was found. In these cases, PCR and electron microscopy examination for HIV and other viral infections were negative. Our data suggest that HIV-immunohistochemistry should be used for the etiological diagnosis of micronodular lesions in AIDS brains, even in the presence of other pathogens. After extensive search, the etiology of the microglial nodules remains unknown in only a small percentage of cases.

Imaging of suprasellar and parasellar tumors

A large number of entities can present as a suprasellar or parasellar mass. These include benign and malignant tumors as well as inflammatory and other lesions that can mimic a neoplasm. Imaging features and distinguishing characteristics of juxtasellar masses are described.

Neuropathogenesis of simian immunodeficiency virus in neonatal rhesus macaques

Neonatal human immunodeficiency virus (HIV) infection usually occurs intrapartum or postpartum and results in a higher incidence of neurological dysfunction than is seen in adults. To explore the neuropathogenesis of neonatal HIV infection, we infected neonatal macaques with simian immunodeficiency virus (SIV) and followed the course of infection focusing on early time points. Infected neonates had decreased brain growth and mild histological changes in brain that resembled those seen in pediatric AIDS, including perivascular infiltrates of mononuclear cells, mineralization of vessels in the basal ganglia, and gliosis. The perivascular lesions and gliosis were associated with the presence of occasional infected cells that required in situ hybridization with radiolabeled riboprobes for detection. Using this technique, SIV-infected cells were detected in the brain parenchyma within 7 days of infection. These findings were confirmed by nested PCR for SIVgag DNA in brain and RT-PCR for viral RNA in cerebrospinal fluid. Together, these techniques revealed SIV infection of the CNS in 12 of 13 neonates infected with SIVmac239, 3 of 3 infected with SIVmac251, and 2 of 2 infected with SIVmac239/316. The prevalence of CNS infection was indistinguishable from that of older animals infected with the same dose and stock of virus, but neonates appeared to have fewer infected cells in the CNS and detecting them required more sensitive techniques. This observation was true regardless of inoculum and despite the fact that neonates had equal or greater viral loads in the periphery compared with older animals. These data suggest that maturation-dependent host factors have a major impact on the neuropathogenesis of pediatric AIDS.

Measles virus infection in a transgenic model: virus-induced immunosuppression and central nervous system disease

Measles virus (MV) infects 40 million persons and kills one million per year primarily by suppressing the immune system and afflicting the central nervous system (CNS). The lack of a suitable small animal model has impeded progress of understanding how MV causes disease and the development of novel therapies and improved vaccines. We tested a transgenic mouse line in which expression of the MV receptor CD46 closely mimicked the location and amount of CD46 found in humans. Virus replicated in and was recovered from these animals' immune systems and was associated with suppression of humoral and cellular immune responses. Infectious virus was recovered from the CNS, replicated primarily in neurons, and spread to distal sites presumably by fast axonal transport. Thus, a small animal model is available for analysis of MV pathogenesis.

Central nervous system abnormalities in pediatric human immunodeficiency virus infection

With the recent improvements in treatment of HIV, the disease has become a chronic one. The mean survival time of HIV-infected children is now 9-10 years, which is more than 4 times the mean age of such children who died in 1990. Yet, the prevalence of HIV encephalopathy has not decreased despite use of HAART. Rather, it is expected that as patients live longer, the prevalence of CNS manifestations will actually increase. Thus, more children can be expected to manifest encephalopathy, cerebral aneurysms and CNS lymphoma. As AIDS patients live longer, newer and more effective drugs to combat the neurological effects of HIV infection will be required. There is little evidence that HIV damages neurons directly; rather, the damage appears to occur indirectly via viral proteins or neurotoxic factors causing excessive stimulation by excitatory amino acids such as glutamate and quinolinate. This common pathway is similar to that seen in acute neuronal injury and CNS degenerative diseases and may make HIV encephalopathy amenable to pharmacotherapy. The very complexity of HIV CNS entry mechanisms and neuropathogenesis provides a host of sites for potential therapeutic interventions and hope for the future.

The mumps virus neurovirulence safety test in Rhesus monkeys: a comparison of mumps virus strains

Wild type mumps viruses are highly neurotropic and a frequent cause of aseptic meningitis in unvaccinated humans. To test whether attenuated mumps viruses used in the manufacture of mumps vaccines have neurovirulent properties, a monkey neurovirulence safety test (MNVT) is performed. However, results with several mumps virus MNVTs have raised questions as to whether the test can reliably discriminate neurovirulent from nonneurovirulent mumps virus strains. Here, various mumps virus strains representing a wide range of neuropathogenicity were tested in a standardized MNVT. A trend of higher neurovirulence scores was observed in monkeys inoculated with wild type mumps virus versus vaccine strains, although differences were not statistically significant. Results indicated the need for further examination and refinement of the MNVT or for development of alternative MNVTs.

Persistent neonatal Borna disease virus (BDV) infection of the brain causes chronic emotional abnormalities in adult rats

Neonatal Borna disease virus (BDV) brain infection results in selective developmental damage to the hippocampal dentate gyrus and the cerebellum. When mature, neonatally BDV-infected rats show extreme locomotor hyperactivity and reduced freezing behavior in novel environments. Traditional interpretation of both of these behavioral abnormalities would suggest decreased anxiety in infected rats compared to normal animals. However, it also possible that the locomotor hyperactivity in infected rats reflects higher rather than reduced anxiety, and is the result of increased escape responses to aversive stimuli. The present experiments were undertaken to test a hypothesis about elevated anxiety in neonatally BDV-infected adult Lewis rats by studying their species-specific fear-related responses. Compared to normal subjects, BDV-infected rats exhibited locomotor hyperactivity and elevated defecation in a highly aversive, brightly lit open field. As expected, in a less aversive, dimly lit open field, uninfected controls increased ambulation, whereas infected rats significantly decreased locomotor activity and defecation. Unlike uninfected rats, BDV-infected rats exhibited an attenuated freezing response immediately after loud auditory stimuli. On the contrary, immediate freezing responses following footshock were comparable in the two groups of animals indicating an intact ability to freeze in BDV-infected rats. Despite a decreased baseline startle responsiveness, BDV-infected rats demonstrated increased sensitization of the startle response by preceding footshocks, suggesting a tendency toward elevated escape responses. Compared to normal subjects, BDV-infected rats showed decreased conditional freezing and elevated conditional defecation response in the context previously paired with aversive stimulation indicating sparing of an autonomic component of fear conditioning. The findings indicate that neonatally BDV-infected adult rats are hyperreactive to aversive stimuli, possibly as a result of chronic emotional abnormalities.

[Viral infection of the central nervous system: from experimental model to human application]

The Daniel's strain of Theiler's virus, a murine picorna virus, induces a neurological disease characterized by an acute encephalomyelitis, followed by a persistent infection of the white matter. This late demyelinating disease is studied as a model for multiple sclerosis because of its chronicity and similarity to the histology of the lesions. This mouse model of viral infection allows a review of the various major aspects of the immune response to an infection of the central nervous system. The observation that inbred strains of mice differ in their susceptibility to the demyelinating disease provided the base for genetic studies that were informative for the involved functional immunological mechanisms. A locus in the H-2D region of the major histocompatibility complex was shown to control susceptibility to the persistent infection, leading to approach the key role of CTLs. Non-H-2 genes were also implicated, one of which was mapped close to the IFN-gamma locus on chromosome 10. The key role of IFN-gamma was demonstrated, and led to a further investigation of the function of the potential producers of this cytokine, namely NK, CD8+, and CD4+ Th1 cells. Finally, non-immune factors were also shown to play a role in resistance. A personal view of the antiviral immune responses emerged from this review.

Comparison of the biological characteristics of two isolates of Neospora caninum

This study compared the biological and genetic properties of a bovine (NC-SweB1) and a canine (NC-Liverpool) isolate of Neospora caninum. A mouse model for CNS infection demonstrated marked differences in pathogenicity between the isolates. NC-Liverpool induced severe clinical signs of neosporosis in 57/58 mice including discoordinated movement, hindlimb paralysis and coat ruffling with severe weight loss. In contrast NC-SweB1 induced similar but less severe symptoms in a much smaller proportion of mice over the same time-period. Statistically significant differences were observed between the isolates in the response (mean weight loss) of mice through time to the different doses inoculated. Histopathological effects on brain tissue reflected the isolate-based differences described above. NC-Liverpool infection resulted in intense inflammatory infiltrates and highly necrotic lesions whereas NC-SweB1 induced a milder meningoencephalitis. Passage in cell-culture over a period of 14 months did not affect the pathogenicity of NC-Liverpool. Immunoblots showed that antibodies to N. caninum appeared earlier in mice inoculated with NC-Liverpool than with NC-SweB1. Finally, RAPD-PCR analysis of NC-Liverpool DNA generated profiles distinct from that observed with DNA from NC-SweB1 or Toxoplasma gondii. In summary this study provides evidence for significant biological and genetic differences between 2 isolates of N. caninum.

Perspective: virus infections and the death of neurons

Neuronotropic viruses induce apoptosis in neurons, and Bcl-2-related anti-apoptotic proteins and caspase inhibitors decrease mortality from acute viral encephalitis. Infected neurons develop cytoplasmic blebbing characteristic of apoptosis, but a paucity of apoptotic nuclear changes potentially indicates unique aspects of virus-induced neuronal apoptosis that remain to be discovered.

AIDS-related visceral aspergillosis: an underdiagnosed disease during life?

Five out of nine consecutive patients with HIV-related visceral aspergillosis observed by us since 1984 were diagnosed only at necropsy examination. The histopathological features of these five patients [two with isolated pneumonia, one with central nervous system (CNS) involvement, one with brain abscess and respiratory disease and one with pulmonary, pleural and kidney infection] have been evaluated according to epidemiological, clinical and radiological features. On the basis of our experience, life-threatening aspergillosis, which is often misdiagnosed or missed in the setting of HIV infection and AIDS, should be suspected in patients with far-advanced underlying disease and unexplained signs and symptoms, even in the absence of some presumed risk factors (i.e. neutropenia and prior steroid treatment). Plain chest radiography and bronchoscopy with broncholaveolar lavage may fail to reveal respiratory disease, CNS aspergillosis is not necessarily associated with suggestive neuroradiological features and disseminated disease may present with multiorgan failure. The unfavorable outcome of this emerging AIDS complication can be improved only by earlier diagnosis based on invasive techniques and appropriate and timely treatment.

Rhinocerebral zygomycosis following bone marrow transplantation in chronic myelogenous leukaemia. Report of a case and review of the literature

We report on a man suffering from chronic myelogenous leukaemia treated by allogeneic bone marrow transplantation who, in the late post-transplantation phase, developed a hyperacute fatal invasive rhinocerebral zygomycosis. The origin of the ascending infection was the sinus sphenoidalis from which fungal hyphae spread to the central nervous system via the skull and the dura mater. The first symptoms of this severe infection were cerebral convulsions and a bilateral total amaurosis. The isolation of the pathogen from post mortem tissue was not successful. The present case is compared with previous reports of zygomycoses after bone marrow transplantation.

Isolation and characterization of a neuropathogenic simian immunodeficiency virus derived from a sooty mangabey

Transfusion of blood from a simian immunodeficiency virus (SIV)- and simian T-cell lymphotropic virus-infected sooty mangabey (designated FGb) to rhesus and pig-tailed macaques resulted in the development of neurologic disease in addition to AIDS. To investigate the role of SIV in neurologic disease, virus was isolated from a lymph node of a pig-tailed macaque (designated PGm) and the cerebrospinal fluid of a rhesus macaque (designated ROn2) and passaged to additional macaques. SIV-related neuropathogenic effects were observed in 100% of the pig-tailed macaques inoculated with either virus. Lesions in these animals included extensive formation of SIV RNA-positive giant cells in the brain parenchyma and meninges. Based upon morphology, the majority of infected cells in both lymphoid and brain tissue appeared to be of macrophage lineage. The virus isolates replicated very well in pig-tailed and rhesus macaque peripheral blood mononuclear cells (PBMC) with rapid kinetics. Differential replicative abilities were observed in both PBMC and macrophage populations, with viruses growing to higher titers in pig-tailed macaque cells than in rhesus macaque cells. An infectious molecular clone of virus derived from the isolate from macaque PGm (PGm5.3) was generated and was shown to have in vitro replication characteristics similar to those of the uncloned virus stock. While molecular analyses of this virus revealed its similarity to SIV isolates from sooty mangabeys, significant amino acid differences in Env and Nef were observed. This virus should provide an excellent system for investigating the mechanism of lentivirus-induced neurologic disease.

Central nervous system brucellosis: presentation, diagnosis and treatment

Although neurological symptoms in brucellosis are frequent, central nervous system (CNS) involvement is uncommon. Five patients with neurobrucellosis are presented. Three patients presented with meningoencephalitis, one with polyradiculoneuritis and one with myelitis and an eighth nerve palsy. All patients had lymphocytic pleocytosis, low glucose and elevated levels of protein in the cerebrospinal fluid (CSF). Gamma-globulin and IgG values in the CSF were also increased. Results of agglutination tests for Brucella in serum and CSF were positive for all patients, although titres were less in the CSF. Brucella melitensis was cultured from two patients. Treatment included concurrent administration of three of the following drugs: doxycycline, rifampicin, streptomycin, co-trimoxazole, ceftriaxone or ciprofloxacin. The three patients with meningoencephalitis fully recovered; the other two patients were left with minor disability.

[Central nervous system lesions in fetuses and newborns in intrauterine infection caused by respiratory viruses]

Congenital respiratory viral infection is followed in the CNS of fetuses and newborns by grave dyscirculatory disturbances with glia proliferation and nervous tissue edema. The process is mainly localized in the periventricular regions of the brain ventricles. Neurologic and morphologic consequences of these damages in the CNS of fetuses and newborns need further studies.