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L G Epstein

Publications and source records attributed to L G Epstein.

At least 55 records · Page 3Linked to original sources
PubMed1995

HIV-1 encephalopathy in children.

HIV-1 infection is a worldwide pandemic, with an estimate of one to two million children infected by the end of the decade. The neurologic manifestations of primary HIV-1 infection in children are a major cause of morbidity and contribute to the fatal outcome in this condition. In the United States, HIV-1 is the most frequent cause of dementia in young adults. Because antiretroviral therapies and treatment for opportunistic infections have lengthened the survival time but not eradicated the virus from the central nervous system, it is likely that the incidence of neurologic dysfunction, including HIV-1 dementia, will increase. Available evidence suggests that the HIV-1 virus does not productively infect neurons but rather induces programmed cell death (apoptosis) in neurons by production of neurotoxic factors, including cytokines, phospholipid mediators, and eicosanoids, and HIV-1 gene products from HIV-1-infected macrophages in the brain. Understanding the mechanisms involved in neuronal cell injury and death may lead to new therapeutic interventions for the neurologic dysfunction associated with HIV-1 infection of the developing central nervous system.

AIDS Dementia Complex↗
PubMed1995

Apoptotic neurons in brains from paediatric patients with HIV-1 encephalitis and progressive encephalopathy.

The pathogenesis of human immunodeficiency virus type 1 (HIV-1) associated dementia in adults involves neuronal loss from discrete areas of the neocortex and subcortical regions, but the mechanism for neuronal death is poorly understood. Gene-directed cell death resulting in apoptosis is thought to be a normal feature of neuronal development, but little is known about neuronal apoptosis in disease states. We investigated whether HIV-1 infection of the central nervous system is spatially associated with apoptosis of neurons. Using an in situ technique to identify newly cleaved 3'-OH ends of DNA as a marker for apoptosis, we demonstrate the presence of apoptotic neurons in cerebral cortex and basal ganglia of children that had HIV-1 encephalitis with progressive encephalopathy. Furthermore, an association was observed between the localization of apoptotic neurons and perivascular inflammatory cell infiltrates containing HIV-1 infected macrophages and multinucleated giant cells. Apoptotic neurons and p24-positive macrophages were observed infrequently in cerebral cortex and basal ganglia in children with HIV-1 infection without encephalitis or clinical encephalopathy. In nine control (HIV-1 negative) brains, ranging from the first post-natal month of life to 16.5 years of age, infrequent neuronal apoptosis was observed in three cases. These findings suggest that neuronal apoptosis is unlikely to be associated with post-natal development except in early post-natal germinal matrix, and that it may instead represent the end result of specific pathological processes, such as HIV-1 encephalitis.

Adolescent↗
PubMed1995

Activation of nuclear factor kappa B in brains from children with HIV-1 encephalitis.

Human immunodeficiency virus type 1 (HIV-1) infection of the central nervous system is associated with decreased neuronal density in discrete areas of the brain. Neuronal loss may occur via apoptosis, initiated by soluble neurotoxic factors secreted from HIV-1 infected macrophages and microglia. To examine further the molecular events involved in HIV-1 neuropathogenesis, we assessed the activity of NF kappa B, an inducible transcription factor involved in the activation of multiple proinflammatory, and potentially neurotoxic, genes. NF kappa B was analysed by immunocytochemistry using specific antisera to the NF kappa B p. 50 and p. 65 subunits. Brains from children with HIV-1 encephalitis and progressive encephalopathy were found to contain increased numbers of NF kappa B immunoreactive cells, relative to control brains (HIV-1 negative, or HIV-1 positive without encephalitis). Double-labelling studies using antibodies to CD68, or RCA-1 lectin, markers for cells of monocyte/macrophage lineage, revealed an increase in the number of microglia and macrophages with nuclear immunoreactivity for NF kappa B in association with HIV-1 encephalitis. NF kappa B positive multinucleated giant cells were also detected, as were cells which contained both NF kappa B and HIV-1 antigen. In contrast, the number of neurons and GFAP-positive astrocytes that were immunoreactive for NF kappa B was approximately the same in all groups of subjects. These data are consistent with the hypothesis that persistent, high-level activation of NF kappa B may promote the sustained production of neurotoxins by microglia and macrophages during HIV-1 encephalitis.

AIDS Dementia Complex↗
PubMed1995

Tumor necrosis factor alpha-induced apoptosis in human neuronal cells: protection by the antioxidant N-acetylcysteine and the genes bcl-2 and crmA.

Tumor necrosis factor alpha (TNF-alpha) is a candidate human immunodeficiency virus type 1-induced neurotoxin that contributes to the pathogenesis of AIDS dementia complex. We report here on the effects of exogenous TNF-alpha on SK-N-MC human neuroblastoma cells differentiated to a neuronal phenotype with retinoic acid, TNF-alpha caused a dose-dependent loss of viability and a corresponding increase in apoptosis in differentiated SK-N-MC cells but not in undifferentiated cultures. Importantly, intracellular signalling via TNF receptors, as measured by activation of the transcription factor NF-kappa B, was unaltered by retinoic acid treatment. Finally, overexpression of bcl-2 or crmA conferred resistance to apoptosis mediated by TNF-alpha, as did the addition of the antioxidant N-acetylcysteine. These results suggest that TNF-alpha induces apoptosis in neuronal cells by a pathway that involves formation of reactive oxygen intermediates and which can be blocked by specific genetic interventions.

AIDS Dementia Complex↗
PubMed1995

Cellular localization of human herpesvirus-6 in the brains of children with AIDS encephalopathy.

Human herpesvirus-6, the etiologic agent of exanthem subitum, is a ubiquitous virus that infects almost all children by the age of 2 years and that has previously been shown to be neuroinvasive. These characteristics suggest that human herpesvirus-6 may be important in the neuropathogenesis of acquired immune deficiency syndrome (AIDS) in children. To address this hypothesis, we evaluated postmortem pediatric brain tissues for the presence of human herpesvirus-6 infection. Using in situ hybridization with a digoxigenin-labeled DNA probe for the large tegument protein gene of human herpesvirus-6, we detected nuclear signals in postmortem brain tissue from 4/5 children with human immunodeficiency virus-1 encephalitis. Human herpesvirus-6 DNA was found in numerous oligodendrocytes of the white matter and less frequently in astrocytes, macrophages, microglia and neurons. The human herpesvirus-6 positive cells detected by in situ hybridization were not immunoreactive either for human herpesvirus-6 early nuclear phosphoproteins or for surface glycoproteins associated with productive infection. Only rare human herpesvirus-6 infected cells were found in age-matched control brain tissues. No human herpesvirus-6 infected cells were found in human fetal brain tissue. These data suggest that human herpesvirus-6 is more extensively disseminated in neural cells in the presence of human immunodeficiency infection and immunodeficiency in pediatric AIDS patients, and it may contribute to the pathogenesis of AIDS encephalopathy.

AIDS Dementia Complex↗
PubMed1995

The development of animal model systems for HIV-1 encephalitis and its associated dementia.

The human immunodeficiency virus (HIV) is neuroinvasive and can be neurovirulent. Indeed, 20-30% of individuals with the acquired immune deficiency syndrome (AIDS) develop cognitive and motor dysfunction (termed the AIDS dementia complex or HIV dementia) coincident with advanced immunosuppression. Despite massive research efforts to discern viral neuropathogenic mechanisms, much remains incompletely understood. Recently, we and others developed animal model systems to elucidate how HIV infection within the brain can lead to impairment of central nervous system function. In this report, we evaluate each of the published animal models for their ability to mirror HIV dementia. Ease of handling and expense were also under consideration. Ultimately, studies in animal systems should permit a better understanding of the nature of HIV-1-induced neurological injury and aid in the development of effective treatments for this dreaded complication of HIV infection.

AIDS Dementia Complex↗
PubMed1994

Human herpesvirus-6 infection in children. A prospective study of complications and reactivation.

BACKGROUND: Infection with human herpesvirus-6 (HHV-6) is nearly universal in infancy or early childhood. However, the course of this infection, its complications, and its potential for persistence or reactivation remain unclear. METHODS: We studied infants and children under the age of three years who presented to our emergency department with acute illnesses. Infants and young children without acute illness were studied as controls. HHV-6 infection was identified by blood-mononuclear-cell culture, serologic testing, and the polymerase chain reaction (PCR). RESULTS: No primary HHV-6 infection was found among 582 infants and young children with acute nonfebrile illnesses or among 352 controls without acute illness. Of 1653 infants and young children with acute febrile illnesses, 160 (9.7 percent) had primary HHV-6 infection, as documented by viremia and seroconversion. They ranged in age from 2 weeks to 25 months; 23 percent were under the age of 6 months. HHV-6 infections accounted for 20 percent of 365 visits to the emergency department for febrile illnesses among children 6 to 12 months old. Of the 160 infants and young children with acute HHV-6 infections, 21 (13 percent) were hospitalized, and 21 had seizures. Often the seizures appeared late and were prolonged or recurrent. HHV-6 infections accounted for one third of all febrile seizures in children up to the age of two years. In follow-up studies over a period of one to two years, the HHV-6 genome persisted in blood mononuclear cells after primary infection in 37 of 56 children (66 percent). Reactivation, sometimes with febrile illnesses, was suggested by subsequent increases in antibody titers in 16 percent (30 of 187) and by PCR in 6 percent (17 of 278). No recurrent viremia was detected. Of 41 healthy newborns studied, 12 (29 percent) had the HHV-6 genome in their blood mononuclear cells; nevertheless, 6 of these newborns subsequently had primary HHV-6 infections. CONCLUSIONS: In infants and young children HHV-6 infection is a major cause of visits to the emergency department, febrile seizures, and hospitalizations. Perinatal transmission may occur, with possible asymptomatic, transient, or persistent neonatal infection.

Acute Disease↗
PubMed1994

HIV-1 infection of the developing nervous system: central role of astrocytes in pathogenesis.

Recent studies in our laboratory and that of Dr. Howard Gendelman have revealed two important pathways for neuronal damage during HIV-1 encephalopathy in children. First, substantial numbers of astrocytes are actively or latently infected with HIV-1. Astrocyte infection may lead to neuronal dysfunction through loss of supporting growth factors, excitotoxicity due to dysregulation of neurotransmitter reuptake, and loosening of the blood-brain barrier permitting further seeding of HIV-1 in the CNS. Significantly, infection of astrocytes is marked by near-exclusive synthesis of early regulatory gene products of HIV-1, while structural proteins characteristic of productive infection are found in macrophages, microglia and multinucleated giant cells. We propose the term 'restricted' to denote the non-productive infection found in astrocytes. Second, HIV-1-infected macrophages initiate inflammatory processes which are amplified through cell-cell interactions with astrocytes. Macrophage-astrocyte interactions produce arachidonic metabolites and potentially neurotoxic cytokines (TNF-alpha and IL-1 beta), leading to astroglial activation and proliferation which then amplifies these cellular processes. These new findings suggest that two major pathways leading to neurotoxicity in pediatric AIDS encephalopathy are linked to HIV-1 infection through astrocyte-mediated processes, and help explain how small numbers of productivity infected cells indirectly cause widespread tissue pathology and elicit profound neurological impairment.

AIDS Dementia Complex↗
PubMed1994

Human neural xenografts: progress in developing an in-vivo model to study human immunodeficiency virus (HIV) and human cytomegalovirus (HCMV) infection.

Human immunodeficiency virus type 1 (HIV-1) infection is highly specific for its human host. In order to study HIV-1 infection of the human nervous system, we have established a small animal model in which second-trimester (11-17.5 weeks) human fetal brain or neural retina is transplanted into the anterior chamber of the eye of immunosuppressed adult rats (Epstein et al., 1992; Cvetkovich et al., 1992), and more recently in immunodeficient (SCID) mice. The human xenografts survive for many months, vascularize and form a blood-brain barrier. Immunohistochemistry with PGP 9.5 identified neuronal cell bodies and neuritic processes. Electron microscopy revealed axonal growth cones and synaptic junctions. Infection of these xenografts with cell-free HIV-1 proved difficult, however co-engraftment with HIV-1-infected human monocytes resulted in characteristic pathological changes, including the formation of syncytial giant cells, neuronal loss, and astroglial proliferation, supporting the hypothesis that these cells can mediate neurotoxicity. In other studies, xenografts of human fetal retinal tissue were readily infected with cell-free human cytomegalovirus (HCMV) strain AD169. These grafts contained cells with intracytoplasmic and intranuclear inclusions typical of HCMV infection. Productive infection within these grafts was demonstrated by the presence of immediate early, and late (capsid) HCMV antigens, by recovery of HCMV on human fibroblast cultures, and by serial passage of virus to additional retinal xenografts (DiLoreto et al., 1994).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Detection of HIV-1 DNA in pediatric AIDS brain tissue by two-step ISPCR.

In order to detect latent infection in neurons or other cell types in formalin-fixed brain tissue, we performed polymerase chain reaction amplification with incorporation of digoxigenin-conjugated deoxynucleotides, followed by in situ hybridization with biotinylated probes. The use of this two-step technique in brain tissue from a child with severe HIV-1 encephalitis revealed signal in both nuclear and perinuclear regions of cells identified as monocytes and astrocytes, and also in perineuronal satellite cells of glial morphology, but HIV-1 infection of neurons was not detected.

AIDS Dementia Complex↗
PubMed1994

Neuroinvasion and persistence of human herpesvirus 6 in children.

Human herpesvirus 6 (HHV-6) causes a febrile illness in children and has been implicated as a cause of encephalitis and recurrent seizures. Paired samples of cerebrospinal fluid (CSF) and peripheral blood mononuclear cells (PBMC) from 487 children were evaluated by nested polymerase chain reaction (PCR) for evidence of current or past infection with HHV-6. PBMC were also cultured for isolation of HHV-6. These data were correlated with the patients' clinical information. HHV-6 DNA was detected in 72 (14.8%) of 487 CSF samples. HHV-6 persistence was documented in 142 children by PCR detection of HHV-6 DNA in PBMC or CSF (or both) in the absence of primary HHV-6 infection; the central nervous system was the only site of HHV-6 DNA persistence in 28.9%. HHV-6 DNA can be detected in the CSF of children during and after primary infection, and the central nervous system may be the sole site of persistence.

Child, Preschool↗
PubMed1994

Overexpression of nef as a marker for restricted HIV-1 infection of astrocytes in postmortem pediatric central nervous tissues.

In previous studies, using polymerase chain reaction amplification of HIV-1 genes directly from pathologic tissues of children who died with AIDS encephalopathy, we showed that the reading frame of the HIV-1 regulatory nef gene is open, suggesting that the nef protein was expressed. We now show, using immunocytochemistry and in situ hybridization with nef-specific probes in postmortem pediatric CNS tissues, that nef mRNA and protein are present in up to 20% of astrocytes in tissue sections selected for extensive histopathology. By contrast, HIV-1 structural proteins such as gag and their coding mRNAs are present in multinucleated giant cells that harbor productive infection and are the hallmark of HIV-1 infection in the CNS. These findings are consistent with the nonproductive infection of glial cells observed in vitro, and imply that HIV-1 infection of astrocytes is restricted to early regulatory gene products, of which nef is the best target as it is expressed at high levels and is membrane-anchored. In developing central nervous tissues of children, restricted and latent HIV-1 infection of astrocytes may be extensive and contribute significantly to HIV-1 neuropathogenesis.

Aged↗
PubMed1994

Cytomegalovirus infection of human retinal tissue: an in vivo model.

BACKGROUND: Cytomegalovirus (CMV) retinitis is a common, devastating complication of AIDS. Strict host specificity of human CMV (HCMV), has limited the study of the virus. The purpose of this research was to create a model that allowed the in vivo infection of human retinal tissue with HCMV. EXPERIMENTAL DESIGN: Small fragments of 13-week human fetal retina were transplanted into the anterior chambers of immune-deficient mice. One week later, 15 of 30 grafts were inoculated with HCMV. Infected and noninfected specimens were compared for histopathologic changes at 14, 30, and 60 days at light and electron microscopic levels. Histochemistry was performed to characterize: level of graft differentiation, range of viral replication cycle, and effects on neuronal, glial, and monocytic elements of the retina. RESULTS: At 30 and 60 days, grafts were well differentiated histologically and histochemically. The infected grafts showed numerous large cells containing intranuclear and intracytoplasmic inclusions. Ultrastructural examination revealed viral particles within cytoplasm and nuclei. Infected cells expressed proteins representative of all phases of the HCMV replication cycle. Most HCMV-infected cells expressed the neuronal marker, protein gene product 9.5. In a second series of experiments, tissue from one graft harvested at 45 days postinfection was used to recover HCMV in fibroblast cultures and also used successfully to passage the virus to two control grafts. CONCLUSIONS: This model allows HCMV to actively infect and replicate within highly differentiated human neural tissue. It produces pathology characteristic of CMV-infected neural tissue in a time course suitable for long-term study. The nature of this model will allow the study of: the replication properties of HCMV in nervous tissue, the specific effects of HCMV on the human retina, the interaction of HCMV with other viruses, e.g., HIV, and various anti-viral therapies.

Animals↗
PubMed1994

Interaction of HIV-1 and human salivary mucins.

Previous studies have suggested that salivary secretions may act as inhibitors of HIV-1 replication in vitro. This inhibitory activity was determined to be associated mainly with secretions obtained from the human submandibular-sublingual glands, and subsequent electron micrographs revealed the association of viral particles with the salivary sediment. Fractionation of human submandibular-sublingual (HSMSL) saliva by size-exclusion chromatography was initiated, and resulting fractions were tested for their ability to modulate the replication of HIV-1 using a plaque assay on HeLa CD4+ cell monolayers. Results indicated that the filtration-sensitive inhibitory activity was primarily associated with the mucin-rich fractions, and the inhibitory activity was found to reduce the number of infectious units by 75%. To determine the identity of the salivary components involved, adsorption experiments involving the interaction of HIV particles with immobilized salivary components were performed. Immunological counter staining revealed an interaction of HIV particles as well as recombinant gp120 with the lower-molecular-weight mucin. Electron microscopic examination of the mucin-rich fractions-HIV incubates revealed the aggregation of virus particles by salivary components. These results suggest that human salivary mucins may have a role in modulating the infectivity of HIV-1.

Adult↗
PubMed1994

Neurological manifestations of perinatally acquired HIV-1 infection.

Infection with the human immunodeficiency virus type 1 (HIV-1) remains a major potential cause of neurological disorders in children and adults throughout the world. This article provides an overview regarding the epidemiology, clinical manifestations, and neuropathogenesis of perinatally acquired HIV-1 infection. Insights regarding the mechanisms of neuroinvasion and neuropathogenesis may allow novel strategies for treating or preventing the devastating consequences of HIV-1 infection of the central nervous system (CNS).

AIDS Dementia Complex↗
PubMed1993

Human immunodeficiency virus type 1 infection of the nervous system: pathogenetic mechanisms.

Human immunodeficiency virus type 1 (HIV-1) infection of the central nervous system is associated with characteristic virological, clinical, and neuropathological findings in adults and children. Productive infection in the brain and spinal cord occurs in blood-derived macrophages, resident microglia, and multinucleated giant cells. Previous work implicated indirect mechanisms for neurotoxicity by HIV-1 gene products or by factors secreted from HIV-1--infected macrophages. However, this cannot explain the paradox between the small numbers of infected cells and the widespread tissue pathology. Based on recent studies from our laboratories, we suggest that HIV-1--infected macrophages can initiate neurotoxicity, which is then amplified through cell-to-cell interactions with astrocytes. Macrophage-astrocyte interactions produce cytokines tumor necrosis factor-alpha and interleukin-1 beta and arachidonic metabolites that cause astroglial proliferation and neuronal injury. Inevitably, the astrogliosis serves to amplify these cellular processes while brain infection maintains itself in macrophage and microglia and possibly in astrocytes (by restricted infection). These findings, taken together, provide fresh insights into how low numbers of productively infected cells could elicit progressive and devastating neurological impairment during HIV-1 disease, and suggest therapeutic strategies to interrupt the pathological process.

AIDS Dementia Complex↗
PubMed1993

Neurotoxic effects of tumor necrosis factor alpha in primary human neuronal cultures are mediated by activation of the glutamate AMPA receptor subtype: implications for AIDS neuropathogenesis.

Human immunodeficiency virus type 1 (HIV) infection of the central nervous system is characterized by neuronal loss in discrete areas of the central nervous system. We have previously demonstrated that HIV-infected monocytes in culture with astroglial cells produce high levels (> or = 200 pg/ml) of the cytokine tumor necrosis factor-alpha (TNF alpha). We now demonstrate that TNF alpha (> or = 200 pg/ml) is neurotoxic to cultured primary human fetal cortical neurons at both light and electron microscopic levels. Subtoxic doses of TNF alpha (50 pg/ml) are neurotoxic in combination with the glutamate (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-proprionic acid (AMPA) subtype receptor agonist AMPA (100 microM). The neurotoxic effects of TNF alpha (200 pg/ml) are blocked in part by the AMPA receptor antagonist, 6-cyano-7-nitroquinoxaline-2, 3-dione (10 microM). This suggests that TNF alpha may exert neurotoxic effects on human neurons by indirect activation of AMPA receptors, which may be important in the pathogenesis and treatment of HIV-mediated encephalopathy.

6-Cyano-7-nitroquinoxaline-2,3-dione↗