Chronic cocaine exposure in the SCID mouse model of HIV encephalitis

Clinical and preclinical evidence suggests that cocaine exposure hastens progression of the HIV disease process. An established active, euphoric dose of cocaine (20 mg/kg) was administered to SCID mice according to a regimen consistent with exposure to the drug by cocaine-abusing HIV-infected patients to determine the effects of cocaine on four previously established pathological characteristics of HIV encephalitis: cognitive deficits, fatigue, astrogliosis, and microgliosis. Mice were intracranially inoculated with either HIV-infected, or uninfected macrophages and then injected with either cocaine or saline in a 2 (Infection)x2 (Cocaine) factorial design. Cognition was assessed by acquisition and retention of a spatially cued learning task. Fatigue was assessed by monitoring motor activity following a 2 min forced swim. Mice were then sacrificed to determine the extent of astrogliosis and microgliosis in the four groups. Results indicated that in comparison to uninfected controls, HIV positive mice had increased astrogliosis and microgliosis, cognitive deficits, and recovered more slowly from fatigue. However, despite evidence that the cocaine exposure regimen activated the central nervous system and had long-term CNS effects, the drug did not alter the behavioral or the neuropathological deficits noted in HIV-infected SCID mice.

Potential relationships between the presence of HIV, macrophages, and astrogliosis in SCID mice with HIV encephalitis

The pathogenesis of HIV encephalitis (HIVE) has not been determined although increased numbers of mononuclear phagocytes (macrophages and microglia), some of which are HIV-infected, and reactive astrogliosis are important pathological findings in this condition. For this experiment, fifty-one SCID mice were inoculated intracerebrally either with human cells and HIV-1, human cells only or HIV only and then sacrificed at various time points. HIV gag mRNA was detected by reverse transcriptase polymerase chain reaction (PCR) distant from the site of inoculation in 73% of mouse brains inoculated with HIV and human cells attesting to the pervasiveness of HIV infection in SCID brain. HIV mRNA was detected as long as 91 days after inoculation of human cells and virus and the presence of HIV gag, nef, and tat/rev mRNA in HIV-infected SCID brains indicates ongoing HIV mRNA synthesis. Brain tissue sections were immunostained for HIV, human macrophages, and astrocytes from a subset of mice (n = 29) from the above groups and qualitatively assessed. PCR data for HIV mRNA was correlated with staining results and these data suggested that the greatest astrogliosis was present in mice inoculated with HIV and human cells, consistent with previously reported data. The data further suggest that astrogliosis is greater when HIV is detected. Taken together the data are consistent with a synergistic effect between macrophages and HIV in the development of astrogliosis.

Molecular targets of opiate drug abuse in neuroAIDS

Opiate drug abuse, through selective actions at mu-opioid receptors (MOR), exacerbates the pathogenesis of human immunodeficiency virus-1 (HIV-1) in the CNS by disrupting glial homeostasis, increasing inflammation, and decreasing the threshold for pro-apoptotic events in neurons. Neurons are affected directly and indirectly by opiate-HIV interactions. Although most opiates drugs have some affinity for kappa (KOR) and/or delta (DOR) opioid receptors, their neurotoxic effects are largely mediated through MOR. Besides direct actions on the neurons themselves, opiates directly affect MOR-expressing astrocytes and microglia. Because of their broad-reaching actions in glia, opiate abuse causes widespread metabolic derangement, inflammation, and the disruption of neuron-glial relationships, which likely contribute to neuronal dysfunction, death, and HIV encephalitis. In addition to direct actions on neural cells, opioids modulate inflammation and disrupt normal intercellular interactions among immunocytes (macrophages and lymphocytes), which on balance further promote neuronal dysfunction and death. The neural pathways involved in opiate enhancement of HIV-induced inflammation and cell death, appear to involve MOR activation with downstream effects through PI3-kinase/Akt and/or MAPK signaling, which suggests possible targets for therapeutic intervention in neuroAIDS.

Update on viral encephalitis

Over 100 viruses have been associated with acute central nervous system infections. The present review focuses on some of the most common agents of viral encephalitis, as well as important emerging viral encephalitides. In this context, the initial detection of West Nile virus in the Western Hemisphere during the 1999 New York City outbreak, the first description of Nipah virus in Malaysia, and the appearance in Asia of a new neurovirulent enterovirus 71 strain that causes severe neurologic disease are highlighted. In addition, advances regarding diagnosis, neuroimaging and treatment of Japanese and herpes simplex encephalitis are presented.

Acute multiple sclerosis characterized by extensive mononuclear phagocyte infiltration

In this study, we examine the clinical, neuroradiological, and immunohistochemical findings of a 51 year old white female who died 27 months after onset of acute multiple sclerosis despite treatment with interferon-beta, azathioprine, corticosteroids, and cyclophosphamide. Immunohistochemical studies revealed extensive gliosis and mononuclear phagocyte infiltration with corresponding upregulation of proinflammatory cytokines (eg. IFN-alpha, TNF-alpha). The significance of immunohistochemical findings with respect to clinical presentation is discussed.

Immunohistochemical localization of kininogen in rat spinal cord and brain

Kininogen localization has been determined by immunocytochemistry in rat spinal cord and brain using a kinin-directed kininogen monoclonal antibody. In the spinal cord, there were immunostained neurons and fibers in laminae I, II, VII, and IX, intensely stained fibers in the superficial layers of the dorsal horn, and immunoreactive glial and endothelial cells. Small neurons, satellite cells, and Schwann cells immunostained distinctly in the dorsal root ganglion. In the brain stem, there were immunoreactive neurons and fibers in the tractus solitarius and nucleus, trigeminal spinal tract and nuclei, periaqueductal gray matter, vestibular nuclei, cochlear nuclei, trapezoid body, medial geniculate nucleus, and red nucleus. Immunostained neurons and fibers were also found in cerebellum (dentate nucleus), cerebral cortex (layers III and V), hippocampus (pyramidal cell layer), and corpus callosum. Glia and endothelial cells stained in all brain regions. The widespread location of kininogen in neurons and their processes, as well as in glial and endothelial cells, indicates more than one functional role, including those proposed as a mediator, a calpain inhibitor, and a kinin precursor, in a variety of neural activities and responses.

Interferon beta-1b and childhood multiple sclerosis

The long-term treatment with interferon beta-1b of a 7-year-old male with relapsing-remitting multiple sclerosis is documented. Thirty-two months after initiating treatment, he demonstrates dramatic clinical improvement, without relapse, despite high titers of neutralizing antibodies to interferon beta-1b. It appears reasonable to attribute a role in his improvement to interferon beta-1b.

Do alcohol and cocaine abuse alter the course of HIV-associated dementia complex?

Although psychoactive drugs are commonly used by AIDS patients, it is unclear whether commonly abused drugs, such as cocaine and ethanol, affect the course of HIV-associated dementia (HADC). Epidemiological studies have resulted in conflicting conclusions as to what role, if any, abused drugs play in HADC. In this review we discuss the clinical and pathological evidence that cocaine and ethanol might exacerbate the detrimental effects of HIV infection on the brain. We also review studies of cocaine and ethanol effects on various components of the immune system both in the presence and absence of retroviral infection. Data from these studies indicate that cocaine and ethanol have profound effects on the immune system that, in many respects, are enhanced by retroviral infection. We conclude that abused drugs likely affect the course of HADC but that proof awaits an examination of their interactive effects in an appropriate in vivo system of retroviral encephalitis.

Increased calpain expression in activated glial and inflammatory cells in experimental allergic encephalomyelitis

In demyelinating diseases such as multiple sclerosis (MS), myelin membrane structure is destabilized as myelin proteins are lost. Calcium-activated neutral proteinase (calpain) is believed to participate in myelin protein degradation because known calpain substrates [myelin basic protein (MBP); myelin-associated glycoprotein] are degraded in this disease. In exploring the role of calpain in demyelinating diseases, we examined calpain expression in Lewis rats with acute experimental allergic encephalomyelitis (EAE), an animal model for MS. Using double-immunofluorescence labeling to identify cells expressing calpain, we labeled rat spinal cord sections for calpain with a polyclonal millicalpain antibody and with mAbs for glial (GFAP, OX42, GalC) and inflammatory (CD2, ED2, interferon gamma) cell-specific markers. Calpain expression was increased in activated microglia (OX42) and infiltrating macrophages (ED2) compared with controls. Oligodendrocytes (galactocerebroside) and astrocytes (GFAP) had constitutive calpain expression in normal spinal cords whereas reactive astrocytes in spinal cords from animals with EAE exhibited markedly increased calpain levels compared with astrocytes in adjuvant controls. Oligodendrocytes in spinal cords from rats with EAE expressed increased calpain levels in some areas, but overall the increases in calpain expression were small. Most T cells in grade 4 EAE expressed low levels of calpain, but interferon gamma-positive cells demonstrated markedly increased calpain expression. These findings suggest that increased levels of calpain in activated glial and inflammatory cells in EAE may contribute to myelin destruction in demyelinating diseases such as MS.

SCID mice with HIV encephalitis develop behavioral abnormalities

Severe combined immunodeficient (SCID) mice inoculated intracerebrally (i.c.) with HIV-infected human monocytes develop brain pathology similar to that in humans with HIV encephalitis. This includes HIV-positive macrophages and multinucleated giant cells, astrogliosis, microglial nodules, and neuronal dropout. These xenografts survive about 1 month. To develop a model of chronic HIV encephalitis and to assay the resulting behavioral abnormalities, we reinoculated SCID mice i.c. every 4 weeks for 3 months with either HIV-infected human monocytes (n = 5) or uninfected human macrophages (n = 4) or administered no inoculation (n = 6); these three groups were monitored for behavioral abnormalities. Tests of cognitive function in a Morris water maze 3.5 months after the first inoculation suggested that HIV-infected mice performed poorly compared with controls. Following testing in the water maze on days 4 and 5 of acquisition, motor activity of infected mice was reduced in comparison with that of controls. Retention of goal location when tested 1 week later was impaired in HIV-infected mice compared with controls. Histopathologic analysis of brains revealed significant astrogliosis and strongly suggested higher numbers of major histocompatibility complex (MHC) class II-positive multinucleated macrophages in HIV-infected compared with control mice. Thus, our preliminary studies indicate that SCID mice with HIV encephalitis develop behavioral abnormalities reminiscent of human disease. These behavioral abnormalities are associated with significantly increased astrogliosis, the presence of HIV, and probably multinucleated giant cells. These studies further support the use of this SCID animal model system for studies of the pathogenesis of HIV encephalitis and for drug interventions.

Increased calpain expression in experimental demyelinating optic neuritis: an immunocytochemical study

Since calcium activated neutral proteinase (calpain) is present in the central nervous system (CNS) and degrades myelin proteins, this endopeptidase has been suggested to play a role in myelin destruction in demyelinating diseases such as multiple sclerosis (MS). In the present study, calpain immunocytochemical expression was examined in Lewis rats with acute experimental allergic encephalomyelitis (EAE), an animal model for MS and optic neuritis. To identify cells expressing calpain, we labeled rat optic nerve sections for calpain with a polyclonal myelin calpain antibody and with monoclonal antibodies for glial (GFAP, OX42) and inflammatory (CD2, ED2, ED1, IFN-gamma) cell-specific markers. The results showed increased calpain expression in microglia (OX42) and infiltrating macrophages (ED1,2) in EAE compared to normal controls. Astrocytes constitutively expressed calpain in controls and acute EAE. Reactive astrocytes in EAE located in or near inflammatory foci, exhibited markedly increased calpain expression. Most T cells in acute EAE showed low level calpain expression while activated IFN-gamma-producing lymphocytes in inflammatory foci exhibited elevated levels of calpain expression. Thus, our results demonstrate increased calpain expression (at transcriptional and/or translational levels) in a rat model of optic neuritis. A role for calpain in myelin destruction during optic neuritis may be relevant to the pathogenesis of this disorder.

Long-term intracranial cannula stabilization in mice with light cured resin composites

A simple and rapid method is described for the introduction and stabilization of chronic indwelling cannulae in mice. Materials and adhesive bonding techniques commonly used in restorative dentistry were used to stabilize the cannulae. The effectiveness of this method was evaluated by shear strength testing across time and histological evaluation of coronal brain sections. Shear strength increased during the first week post surgery and remained stable for up to 60 days. The force required to dislodge the cannulae from skulls ranged from 0.70 to 2.45 kg. Histological evaluation revealed no significant infection or inflammatory response due to the materials used. Cannulae stabilization by this technique appears to be suitable for most experimental conditions.

Transforming growth factor-beta1 in adult human microglia and its stimulated production by interleukin-1

Ameboid microglia express human immunodeficiency virus 1 (HIV-1) more frequently than do ramified microglia. These two microglial subtypes might also differ in the frequency with which they express transforming growth factor-beta1 (TGF-beta1), a cytokine that regulates HIV-1 expression in monocytes. Results described here show that ameboid and ramified microglia express TGF-beta1. In brain tissues from HIV-1-infected individuals as compared with seronegative controls, ameboid rather than ramified microglia more frequently expressed TGF-beta1. Ameboid microglia, isolated and cultured from postmortem adult human brain more frequently expressed TGF-beta1 in presence of interleukin-1(IL-1), a cytokine that is elevated in brains of HIV-1-infected individuals when compared with seronegative controls. The stimulation of TGF-beta1 by IL-1 was dose and time dependent, occurring with ameboid microglia isolated from either frontal cortex or globus pallidus but not midbrain pons. Ameboid microglia are similar to the RCA-1-positive cells that form clusters, called microglial nodules, in the brain of HIV-1-infected individuals. Pathologic conditions, such as disseminated microglial nodules, are associated with HIV-1 encephalitis, direct infection of the brain, and moderate to severe neurologic impairment. TGF-beta1 expression in ameboid microglia may play a role in HIV-1 neuropathogenesis.

Cocaine/sex type effects on T lymphocytes: a preliminary report

The influence of gender on the effects of cocaine (5 or 40 mg/kg) on immune function of sexually immature (35-day-old) C57BL/6J mice was assessed. The proliferation of T cells in thymus and spleen stimulated with phytohemagglutinin (PHA) and concanavalin-A(Con-A) was determined by 3H thymidine incorporation 24 hours after cocaine injections. The drug produced a dose-dependent reduction (25-51%) of Con-A and PHA-stimulated T cell proliferation in thymus from both male and female mice. Additionally, the impairment occurred at a lower cocaine dose for female than for male mice when the T cells were challenged with PHA. Under the experimental conditions, cocaine did not alter weights or cell numbers of thymus and spleen or T cell proliferation in spleen.

A potential role for interferon-alpha in the pathogenesis of HIV-associated dementia

Previous studies in patients receiving interferon-alpha (IFN-alpha) therapy and patients with systemic lupus erythematosus have demonstrated that elevated cerebrospinal fluid (CSF) levels of IFN-alpha are associated with cognitive dysfunction. We measured IFN-alpha levels in CSF and blood by ELISA in human immunodeficiency virus (HIV)-positive patients with (n = 21) and without (n = 23) dementia and HIV-negative controls (n = 48). IFN-alpha was significantly elevated in the CSF of HIV-positive patients with dementia compared to those without dementia and controls. An increasing amount of IFN-alpha in the CSF was correlated with the clinical parameter of increasing Memorial Sloan Kettering scores; although these correlations were not statistically significant, they further suggest an association of increased CSF IFN-alpha with neurocognitive dysfunction in AIDS. Immunocytochemical staining of brains demonstrated IFN-alpha-positive macrophages and astrocytes in frontal cortex and white matter and IFN-alpha mRNA was detected by reverse transcriptase-polymerase chain reaction, further indicating that IFN-alpha is made by cells within the brain and suggesting that the significant increases of IFN-alpha protein found in the CSF of patients with HIV-associated dementia complex are derived from intrinsic brain cells such as macrophages and astrocytes. Increased local production of IFN-alpha during HIV infection may contribute directly or indirectly to the pathogenesis of HIV-associated dementia.

Unifying hypothesis for the pathogenesis of HIV-associated dementia complex, vacuolar myelopathy, and sensory neuropathy

Neurological diseases associated with HIV infection include dementia, vacuolar myelopathy, and sensory neuropathy. Although in vitro studies suggest that other nervous system cell types could harbor HIV, immunohistochemical and in situ hybridization studies have indicated that only macrophages/microglia are significantly infected in the central nervous system. In the peripheral nervous system, even HIV-infected macrophages are rare. Therefore, theories regarding the pathogenesis of HIV-associated neurologic disorders have centered around the elaboration of substances that may be toxic to neurons, oligodendrocytes or myelin. These potential toxins include HIV proteins, cellular metabolites, and cytokines. In this review we present evidence that there are large numbers of macrophages/microglia present in the nervous system of patients with these diseases and that they produce tumor necrosis factor (TNF)-alpha. The large increase in macrophage activity late in HIV infection may be due to the diminution in production by CD4-positive T cells of cytokines such as interleukin (IL)-4 and IL-10 which are inhibitors of macrophage activities. We hypothesize that HIV-associated dementia complex, vacuolar myelopathy, and sensory neuropathy are directly or indirectly related to the increased numbers of macrophages found in brain, spinal cord, and peripheral nerve. Future therapies may be directed towards inhibition of macrophage functions.

Age-dependent susceptibility to fatal encephalitis: alphavirus infection of neurons

Sindbis virus encephalitis in mice provides a model for studying age-dependent susceptibility to acute viral encephalitis. The AR339 strain of SV causes fatal encephalitis in newborn mice, but weanling mice recover uneventfully. Increased virulence for older mice is associated with a single amino acid change from Gln to His at position 55 of the E2 glycoprotein. Weanling mice with normal immune systems clear infectious virus from neurons through an antibody-mediated mechanism. This does not happen in newborn mice because the infected neurons die soon after they are infected. Death in immature neurons, as well as most other mammalian cells infected with Sindbis virus, occurs by induction of apoptosis. This can be prevented by cellular expression of bcl-2, an inhibitor of apoptosis, which is expressed by mature neurons in culture. We conclude that mature neurons are resistant to induction of apoptosis after infection with SV through expression of cellular inhibitors of apoptosis. This provides the opportunity for antibody to clear virus by a noncytolytic mechanism.

Control of astrocytosis by interleukin-1 and transforming growth factor-beta 1 in human brain

Astrocytosis is a common neurocellular manifestation of brain pathology in individuals with a variety of diseases. It is comprised of astrocytic hyperplasia (an increase in number of astrocytes) and astrocytic hypertrophy (an increase in size of astrocytes). The precise cause(s) of astrocytosis remains unknown. We morphometrically measured the relative extent of astrocytosis in brains of 22 individuals who died with seven different diseases. The relative amounts of interleukin-1 (IL-1) and transforming growth factor-beta 1 (TGF-beta 1) immunoreactive products (IRPs) were next assessed in sections serial to those in which astrocytosis was measured because these cytokines were shown in animal and in vitro experiments to be associated with astrocytosis. The data demonstrate that astrocytosis and these cytokines were co-localized in all examined human tissues. Relative increase in density of astrocytes was correlated with the increase in total IL-1 but not TGF-beta 1. In contrast, the increase in size of astrocytes was correlated with TGF-beta 1 associated only with astrocytes but not with total IL-1. Both IL-1 and TGF-beta 1 IRPs were present in GFAP IRP-containing and other cells, as assessed by double label immunocytochemistry. These observations suggest that IL-1 acts on astrocytes by both, paracrine and autocrine mechanisms whereas, TGF-beta 1 only acts by an autocrine mechanism. Because these correlations were statistically significant and also because a change in number and size of astrocytes constitutes the most frequent response of astrocytes to several diseases or injury, we conclude that these cytokines may mediate the most common pathological change in human brain.

Virus specificity and isotype expression of intraparenchymal antibody-secreting cells during Sindbis virus encephalitis in mice

To study the generation of specific antibody responses within the central nervous system (CNS), we have utilized a murine model of acute viral encephalitis. When Sindbis virus (SV) is injected intracerebrally into weanling mice it causes an acute non-fatal encephalitis and recovery is primarily dependent on the development of antiviral antibody. We used a modified enzyme-linked immunoassay to determine the number of antibody-secreting cells (ASC) specific for SV and their Ig isotype in brain, spleen and cervical lymph nodes over the course of the acute encephalitis. The numbers of SV-specific ASC peak early in spleen and lymph nodes and then begin to increase in brain, suggesting that initial stimulation of B cells occurs primarily in peripheral lymphoid tissue followed by B cell entry into the circulation and appearance in the brain. The pattern for each individual isotype was similar with peak numbers of SV-specific cells present in the spleen 5-7 days after infection, while numbers in the brain continue to rise through day 20 when most ASC were secreting IgG2a or IgA SV-specific antibody. The data suggest therefore that most isotype switching from IgM to IgG and IgA occurs in peripheral lymphoid tissue. An exception to this pattern is IgG1, where numbers of ASC producing IgG1 do not show a peak in spleen and continue to rise in brain through the course of acute encephalitis. The data also indicate that early in infection a large proportion of ASC in the brain are not specific for SV and demonstrate that recruitment of ASC into the CNS is non-specific.(ABSTRACT TRUNCATED AT 250 WORDS)

A model of human immunodeficiency virus encephalitis in scid mice

Human immunodeficiency virus (HIV)-associated dementia complex is a common and devastating manifestation of the late phases of HIV infection. The pathogenesis of dementia complex is poorly understood and effective treatments have not been developed, in part because of the lack of an appropriate animal model. Mice with severe combined immunodeficiency (scid mice), which accept xenografts without rejection, were intracerebrally inoculated with human peripheral blood mononuclear cells and HIV. One to 4 weeks after inoculation, the brains of these mice contained human macrophages (some of which were HIV p24 antigen positive), occasional multinucleated cells, and striking gliosis by immunocytochemical staining. Human macrophages also were frequently positive for tumor necrosis factor type alpha and occasionally for interleukin 1 and VLA-4. Cultures of these brains for HIV were positive. Generally, human macrophages were not present in the brains of control mice, nor was significant gliosis, and HIV was not recovered from mice that received HIV only intracerebrally. Pathologically, this model of HIV encephalitis in scid mice resembles HIV encephalitis in humans and the data suggest that the activation of macrophages by infection with HIV results in their accumulation and persistence in brain and in the development of gliosis. This model of HIV encephalitis should provide insights into the pathogenesis and treatment of this disorder.

Intracerebral cytokine messenger RNA expression in acquired immunodeficiency syndrome dementia

The pathogenesis of the dementia associated with human immunodeficiency virus (HIV) infection is unclear, but has been postulated to be due to indirect effects of HIV infection including the local production of cytokines. To determine which cytokines are produced in the nervous system and to identify any correlations with dementia, cytokine and HIV messenger RNA expression was analyzed by reverse transcriptase-polymerase chain reaction in the brains from 24 HIV-infected patients with and without dementia and 9 HIV-uninfected control subjects. Levels of tumor necrosis factor-alpha messenger RNA were significantly higher and levels of interleukin (IL)-4 messenger RNA were significantly lower in demented compared to nondemented HIV-infected patients. Demented patients also had lower IL-1 beta levels than did nondemented patients. No significant differences were detected in the amounts of leukemia inhibitory factor, IL-6, transforming growth factor-beta 1 and -beta 2, monokine induced by gamma interferon-2 (MIG-2), or interferon-gamma messenger RNAs. IL-10 and IL-2 messenger RNAs were undetectable in all brains examined. Cytokine messenger RNA levels in nondemented HIV-positive patients were similar to those in HIV-negative control subjects. HIV transcripts were more abundant in subcortical white matter than in the basal ganglia, cortex, or deep white matter. Our findings suggest a possible role for tumor necrosis factor-alpha in the development of neurological dysfunction. Increased levels of tumor necrosis factor-alpha messenger RNA were not associated with increased levels of IL-1 beta messenger RNA, suggesting differential regulation of these monokines in acquired immunodeficiency syndrome dementia.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytokine expression of macrophages in HIV-1-associated vacuolar myelopathy

Macrophages are frequently present within the periaxonal and intramyelinic vacuoles that are located primarily in the posterior and lateral funiculi of the thoracic spinal cord in HIV-associated vacuolar myelopathy. But the role of these macrophages in the formation of the vacuoles is unclear. One hypothesis is that cytokines, such as interleukin-1 (IL-1) and tumor necrosis factor (TNF)-alpha, are produced locally by macrophages and have toxic effects on myelin or oligodendrocytes. The resulting myelin damage eventually culminates in the removal of myelin by macrophages and vacuole formation. We studied thoracic spinal cord specimens taken at autopsy from HIV-positive (+) and HIV-negative individuals. The predominant mononuclear cells present in HIV+ spinal cords are macrophages. They are located primarily in the posterior and lateral funiculi regardless of the presence or absence of vacuolar myelopathy. Macrophages and microglia are more frequent in HIV+ than HIV-negative individuals and these cells frequently stain for class I and class II antigens, IL-1, and TNF-alpha. Activated macrophages positive for IL-1 and TNF-alpha are great increased in the posterior and lateral funiculi of HIV+ individuals with and without vacuolar myelopathy, suggesting they are present prior to the development of vacuoles. Cytokines, such as TNF-alpha, may be toxic for myelin or oligodendrocytes, leading to myelin damage and removal by macrophages and vacuole formation.

Gliosis in human brain: relationship to size but not other properties of astrocytes

Gliosis is the most frequent and therefore important neurocellular reaction to brain insult occurring in diseases ranging from AIDS to infarction. Neuropathological diagnosis of gliosis is based on morphological changes of brain glial cells. Changes commonly agreed to reflect gliosis are qualitative increases in size, number and glial fibrillary acidic protein (GFAP) immunoreactivity of astrocytes. These parameters were morphometrically quantified in brain tissues of 22 individuals who died with 7 diseases and statistically compared to the extent of gliosis independently determined by 3 qualified observers. The data indicate that the extent of gliosis correlated with the increase in size of astrocytes in white matter (p = 0.67) and this relationship was statistically significant (P = 0.0006). In contrast, the extent of gliosis was not correlated with the density of astrocytes nor the intensity of GFAP staining.

Long term intraparenchymal Ig secretion after acute viral encephalitis in mice

Oligoclonal bands in the cerebrospinal fluid indicate intrathecal synthesis of Ig of restricted heterogeneity and are associated with a number of central nervous system inflammatory diseases. To gain better insight into the persistence of oligoclonal bands found in the central nervous system we studied mice infected with Sindbis virus (SV), a RNA virus that causes an acute, nonfatal encephalitis in mice. SV was inoculated intracerebrally into weanling mice and brains and spleens were harvested at various time points long after the acute encephalitis had resolved. A modified enzyme-linked immunoassay was used to study cultured B cells separated from the brain and spleen for their Ig isotype expression and specificity for SV. We used the polymerase chain reaction technique to detect SV RNA in brain. Three mo after inoculation 47% of the B cells found in brain are secreting antibody specific for SV structural proteins. By 1 yr 62% are SV specific. B cells secreting IgG2a predominate. Polymerase chain reaction data indicate that despite complete clearance of infectious virus by 7 days SV RNA is still present in brain at least 6 mo after infection. The data indicate that B cells in brain secrete antibody to SV long after the acute encephalitis has resolved. The persistence of SV RNA suggests that viral protein may continue to be made, providing the impetus for the continued presence of SV-specific B cells in the brain.

Long term intraparenchymal Ig secretion after acute viral encephalitis in mice

Oligoclonal bands in the cerebrospinal fluid indicate intrathecal synthesis of Ig of restricted heterogeneity and are associated with a number of central nervous system inflammatory diseases. To gain better insight into the persistence of oligoclonal bands found in the central nervous system we studied mice infected with Sindbis virus (SV), a RNA virus that causes an acute, nonfatal encephalitis in mice. SV was inoculated intracerebrally into weanling mice and brains and spleens were harvested at various time points long after the acute encephalitis had resolved. A modified enzyme-linked immunoassay was used to study cultured B cells separated from the brain and spleen for their Ig isotype expression and specificity for SV. We used the polymerase chain reaction technique to detect SV RNA in brain. Three mo after inoculation 47% of the B cells found in brain are secreting antibody specific for SV structural proteins. By 1 yr 62% are SV specific. B cells secreting IgG2a predominate. Polymerase chain reaction data indicate that despite complete clearance of infectious virus by 7 days SV RNA is still present in brain at least 6 mo after infection. The data indicate that B cells in brain secrete antibody to SV long after the acute encephalitis has resolved. The persistence of SV RNA suggests that viral protein may continue to be made, providing the impetus for the continued presence of SV-specific B cells in the brain.

Macrophage responses and myelin clearance during Wallerian degeneration: relevance to immune-mediated demyelination

Macrophages are important effector cells in immune-mediated demyelination. Current concepts regarding their entry and activation focus on the effects of T-cell-derived cytokines. This presentation describes the responses of macrophages and microglia to a non-inflammatory, non-immune injury, Wallerian degeneration. During Wallerian degeneration in the peripheral nervous system (PNS), macrophages are promptly and abundantly recruited from the circulation, and myelin clearance is prompt. In the central nervous system (CNS), the appearance of macrophages is markedly slower, and entry from the circulation is modest or absent. Myelin clearance is similarly delayed. The nature of the factors promoting macrophage entry and activation in Wallerian degeneration, and the bases for the differences between PNS and CNS, are relevant to current issues in immune-mediated demyelination.

Chronic demyelinating polyneuropathy associated with eosinophilia-myalgia syndrome

Eosinophilia-myalgia syndrome (EMS) is a newly described syndrome associated with use of L-tryptophan. A neuropathy with features of axonal degeneration has also been described in conjunction with EMS. Demyelinating polyneuropathy is not a well recognised association of the syndrome. The two patients with EMS reported presented with profound weakness and sensory loss and were found to have clinical, electrophysiological and pathological evidence of a chronic demyelinating polyneuropathy. The concurrence of this neuropathy with EMS, as well as several other features of their illness, is suggestive of an immune mediated mechanism in the pathophysiology of EMS.

The immune response in viral encephalitis

The central nervous system (CNS) offers a unique organ system in which to study viral immunopathogenesis. The presence of the blood-brain barrier that restricts entry of cells and protein, the restricted expression of MHC antigens and the nonrenewable nature of the neuronal cell population offer challenges to the immune system for viral clearance and increase the chances for viral persistence. We have used Sindbis virus encephalitis in mice as a model system for the study of the development of immune reactions in the CNS and clearance of virus from neurons. The immune response to this and other viral infections of the CNS probably are initiated in peripheral lymphoid tissue followed by entry of activated T cells into the cerebrospinal fluid, meninges, and brain parenchyma. During Sindbis virus infection class I and II MHC antigens are expressed extensively on microglia which may present viral antigen produced by the infected neurons. Full development of the inflammatory response requires virus-specific T cells, but participating cells include NK cells, gamma delta T cells, monocytes and B cells. The entry of Ig-secreting B cells corresponds with the appearance of increased amounts of IgG and IgA in the cerebrospinal fluid. Clearance of Sindbis virus from the brain was studied using persistently infected severe combined immunodeficient (scid) mice. Passive transfer of immune serum or immune T cells to these infected mice demonstrated that antibody to a surface glycoprotein of the virus eliminated virus by a noncomplemented-mediated, noncytolytic mechanism. Immune T cells had no effect on virus replication.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytokine expression in the brain during the acquired immunodeficiency syndrome

The pathogenesis of central nervous system (CNS) disease in acquired immunodeficiency syndrome (AIDS) is poorly understood but may be related to specific effects of the immune system. Cytokines such as tumor necrosis factor and interleukin-1 may have toxic effects on CNS cells and have been postulated to contribute to the pathogenesis of the neurological complications of human immunodeficiency virus (HIV) infection. To characterize viral and immunological activity in the CNS, frozen specimens taken at autopsy from the cerebral cortex and white matter of HIV-seropositive and -seronegative individuals were stained immunocytochemically for mononuclear cells, major histocompatibility complex (MHC) antigens, HIV, astrocytes, and the cytokines interleukin-1 and -6, tumor necrosis factor-alpha and -beta, and interferon gamma. Levels of soluble CD4, CD8, and interleukin-2 receptor, as well as interferon gamma, tumor necrosis factor-alpha, beta 2-microglobulin, neopterin, and interleukin-6 and -1 beta were assayed in the cerebrospinal fluid and plasma of many of these individuals during life. The HIV-seropositive group included individuals without neurological disease, those with CNS opportunistic infections, and those with HIV encephalopathy. Perivascular cells, consisting primarily of macrophages with some CD4+ and CD8+ T cells and rare B cells, were consistently MHC class II positive. MHC class II antigen was also present on microglial cells, which were frequently positive for tumor necrosis factor-alpha. HIV p24 antigen, when present, was found on macrophages and microglia. Endothelial cells were frequently positive for interleukin-1 and interferon gamma and less frequently for tumor necrosis factor and interleukin-6. There were gliosis and significant increases in MHC class II antigen, interleukin-1, and tumor necrosis factor-alpha in HIV-positive patients compared to HIV-negative brains. Cerebrospinal fluid from most of the patients tested had increased levels of tumor necrosis factor, beta 2-microglobulin, and neopterin. There was no correlation in HIV-positive individuals between levels of cytokines and the presence or absence of CNS disease. These data indicate that there is a relative state of "immune activation" in the brains of HIV-positive compared to HIV-negative individuals, and suggest a potential role for the immune system in the pathogenesis of HIV encephalopathy.

The characterization of Ia expression during Sindbis virus encephalitis in normal and athymic nude mice

To characterize the expression of Ia systemically and locally on mononuclear cells during acute viral encephalitis, weanling mice were inoculated intracerebrally with Sindbis virus (SV), an alphavirus. Peripheral blood mononuclear cells, splenocytes and perivascular inflammatory cells in frozen brain sections were examined immunocytochemically for the presence of Ia. Ia expression increased in the spleen, blood and brain during SV encephalitis. The majority of the cells in the central nervous system (CNS) expressing Ia were perivascular mononuclear cells but Ia was also found on stellate parenchymal cells. Using one micrometer cryopreserved serial sections we identified these parenchymal cells as macrophages and microglia but not astrocytes. We also identified rare Ia-positive cells resembling endothelial cells. Frozen brain sections of SV-infected T cell-deficient nu/nu mice were also examined for Ia expression. The number and percentage of Ia-positive cells in perivascular inflammatory cells were markedly decreased compared to normal mice and Ia-positive stellate parenchymal cells were less numerous. This suggests that immunocompetent T cells are necessary for "normal" infiltration of inflammatory cells and for Ia expression in the CNS during SV encephalitis.

Characterization of the local and systemic B cell response of normal and athymic nude mice with Sindbis virus encephalitis

During Sindbis virus (SV) encephalitis in mice B cells are an important component of the mononuclear inflammatory response and recovery depends primarily on the development of antiviral antibody. To begin to characterize various parameters of the local B cell response during SV encephalitis we have defined B cell isotype expression in brain sections, splenocytes and peripheral blood mononuclear cells (PBMC) in normal and athymic nude mice using an immunoperoxidase technique. Early (days 3-5) in SV encephalitis brain perivascular B cells are IgM or IgM/IgD-bearing lymphocytes, later (days 10-14) most B cells express one of the IgG isotypes or IgA. The pattern of isotype expression seen in the brain during the course of the encephalitis is reflected in the spleen and blood. The data suggest that progressive isotype switching results in an increasingly higher percentage of certain isotypes, especially IgG2a. Isotype switching of most B cells may occur outside of the brain, or may arise in situ from the IgM/IgD-bearing B cells found in the brain throughout the course of encephalitis. In athymic nude mice numbers of B cells in brain were markedly decreased and the cells present were primarily IgM-bearing, although IgG isotypes and IgA did appear late (day 14). The data suggest that T cells are required for recruitment of B cells into the inflammatory response as well as for normal isotype switching and peripheral B cell maturation during SV encephalitis.