RESUMO
Microglia in human post-mortem tissue in schizophrenia patients' brains engulf synaptic material, but not differently to age-matched non-neurological control brains. Also, schizophrenia brains display similar levels of microgliosis to control brains.
Assuntos
Microglia/patologia , Córtex Pré-Frontal/patologia , Esquizofrenia/patologia , Sinapses/patologia , HumanosRESUMO
Motor Neuron Disease (MND) is a fatal neurodegenerative condition, which is characterized by the selective loss of the upper and lower motor neurons. At the sites of motor neuron injury, accumulation of activated microglia, the primary immune cells of the central nervous system, is commonly observed in both human post mortem studies and animal models of MND. Microglial activation has been found to correlate with many clinical features and importantly, the speed of disease progression in humans. Both anti-inflammatory and pro-inflammatory microglial responses have been shown to influence disease progression in humans and models of MND. As such, microglia could both contribute to and protect against inflammatory mechanisms of pathogenesis in MND. While murine models have characterized the microglial response to MND, these studies have painted a complex and often contradictory picture, indicating a need for further characterization in humans. This review examines the potential role microglia play in MND in human and animal studies. Both the pro-inflammatory and anti-inflammatory responses will be addressed, throughout the course of disease, followed by the potential of microglia as a target in the development of disease-modifying treatments for MND.
Assuntos
Microglia/patologia , Doença dos Neurônios Motores/patologia , Animais , HumanosRESUMO
Alzheimer's disease (AD) pathology is multi-faceted, including extracellular accumulation of amyloid-ß (Aß), accumulation of tau within neurons, glial activation and loss of neurons and synapses. From a neuropathological perspective, usually at a single time-point and often at the end-stage of the disease, it is challenging to understand the cause and effect relationships between these components. There are at least four ways of trying to unravel these relationships. First, genetic studies demonstrate mutations that influence Aß production, but not tau, can initiate AD; whereas genetic variants influencing AD risk are related to innate immunity and lipid metabolism. Second, studies at early time points show that pathology begins decades before the onset of dementia and indicate different anatomical locations for initiation of Aß and tau accumulation. Third, cause and effect can be studied in experimental models, but most animal models do not fully replicate AD pathology. However, induced pluripotent stem cells (iPSCs) to study live human neurons has introduced a new perspective. Fourth, clinical trials may alter AD pathology giving insights into cause and effect relationships. Therefore, a sequence of (i) neocortical Aß accumulation followed by (ii) a microglial inflammatory reaction to Aß, causing neuritic dystrophy which promotes (iii) spread of tau from the limbic system to the neocortex with (iv) progressive tau accumulation and spread resulting in (v) neurodegeneration, explains the evidence. It is proposed that different therapeutic targets are required for different stages of the disease process: Aß for primary prevention, microglia for secondary prevention, and tau for established disease.
Assuntos
Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Microglia/patologia , Emaranhados Neurofibrilares/patologia , Neurônios/patologia , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/fisiopatologia , Animais , Humanos , Microglia/metabolismo , Neurônios/metabolismo , Placa Amiloide/patologiaAssuntos
Neoplasias Encefálicas , Formaldeído , Glioblastoma , Sequenciamento Completo do Genoma , Humanos , Glioblastoma/genética , Glioblastoma/diagnóstico , Sequenciamento Completo do Genoma/métodos , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/patologia , Neoplasias Encefálicas/diagnóstico , Fixação de Tecidos/métodos , DNA de Neoplasias/genética , Masculino , FemininoRESUMO
Current tissue-clearing protocols for imaging in three dimensions (3D) are typically applied to optimally fixed, small-volume rodent brain tissue - which is not representative of the tissue found in diagnostic neuropathology laboratories. We present a method to visualise the cerebral cortical vasculature in 3D in human post-mortem brain tissue which had been preserved in formalin for many years. Tissue blocks of cerebral cortex from two control cases, two Alzheimer's brains and two cases from Alzheimer's patients immunised against Aß42 were stained with fluorescent Lycopersicon esculentum agglutinin (Tomato lectin), dehydrated and cleared using an adapted three-dimensional imaging of solvent cleared organs (3DISCO) protocol to visualise the vascular endothelium. Tissue was imaged using light sheet and confocal microscopy and reconstructed in 3D using amira software. The method permits visualisation of the arrangement of the parallel penetrating cortical vasculature in the human brain. The presence of four vascular features including anastomosis, U-shaped vessels, spiralling and loops were revealed. In summary, we present a low cost and simple method to visualise the human cerebral vasculature in 3D compatible with prolonged fixation times (years), allowing study of vascular involvement in a range of normative and pathological states.
Assuntos
Córtex Cerebral/irrigação sanguínea , Circulação Cerebrovascular , Técnicas de Preparação Histocitológica , Imageamento Tridimensional/métodos , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , MasculinoRESUMO
Rapid and effective clearance of cell-free haemoglobin after subarachnoid haemorrhage (SAH) is important to prevent vasospasm and neurotoxicity and improve long-term outcome. Haemoglobin is avidly bound by haptoglobin, and the complex is cleared by CD163 expressed on the membrane surface of macrophages. We studied the kinetics of haemoglobin and haptoglobin in cerebrospinal fluid after SAH. We show that haemoglobin levels rise gradually after SAH. Haptoglobin levels rise acutely with aneurysmal rupture as a result of injection of blood into the subarachnoid space. Although levels decline as haemoglobin scavenging occurs, complete depletion of haptoglobin does not occur and levels start rising again, indicating saturation of CD163 sites available for haptoglobin-haemoglobin clearance. In a preliminary neuropathological study we demonstrate that meningeal CD163 expression is upregulated after SAH, in keeping with a proinflammatory state. However, loss of CD163 occurs in meningeal areas with overlying blood compared with areas without overlying blood. Becauses ADAM17 is the enzyme responsible for shedding membrane-bound CD163, its inhibition may be a potential therapeutic strategy after SAH.
Assuntos
Antígenos CD/líquido cefalorraquidiano , Antígenos de Diferenciação Mielomonocítica/líquido cefalorraquidiano , Haptoglobinas/líquido cefalorraquidiano , Hemoglobinas/líquido cefalorraquidiano , Hemorragia Subaracnóidea/líquido cefalorraquidiano , Vasoespasmo Intracraniano/líquido cefalorraquidiano , Humanos , Cinética , Ligação Proteica , Receptores de Superfície Celular , Hemorragia Subaracnóidea/complicações , Bancos de Tecidos , Regulação para Cima , Vasoespasmo Intracraniano/etiologia , Vasoespasmo Intracraniano/prevenção & controleRESUMO
Microglia in the central nervous system are usually maintained in a quiescent state. When activated, they can perform many diverse functions which may be either beneficial or harmful depending on the situation. Although microglial activation may be accompanied by changes in morphology, morphological changes cannot accurately predict the function being undertaken by a microglial cell. Studies of peripheral macrophages and in vitro and animal studies of microglia have resulted in the definition of specific activation states: M1 (classical activation) and M2 (sometimes subdivided into alternative activation and acquired deactivation). Some authors have suggested that these might be an overlapping continuum of functions rather than discrete categories. In this review, we consider translational aspects of our knowledge of microglia: specifically, we discuss the question as to what extent different activation states of microglia exist in the human central nervous system, which tools can be used to identify them and emerging evidence for such changes in ageing and in Alzheimer's disease.
Assuntos
Encéfalo/citologia , Encéfalo/imunologia , Inflamação/imunologia , Microglia/citologia , Microglia/imunologia , Animais , Encéfalo/metabolismo , Humanos , Inflamação/metabolismo , Microglia/metabolismoRESUMO
AIM: Microglia form a high proportion of cells in glial tumours but their role in supporting or inhibiting tumour growth is unclear. Here we describe the establishment of an in vitro model to investigate their role in astrocytomas. METHODS: Rat hippocampal slices were prepared and, after 7 days to allow microglia to become quiescent, rat C6 astrocytic tumour cells were added. Over the following 7 days, infiltration and cell death were studied using fluorescent C6 tumour cells and confocal microscopy; immunophenotyping of microglia was performed using CD68 (phagocytosis), MHCII (antigen-presentation) and Iba1 (microglial marker regardless of functional state). Cell proliferation was assessed using Ki67 and qPCR to detect cytokine expression. Sham and control groups were included. RESULTS: Microscopy showed proliferation of C6 tumour cells with both infiltration of tumour cells into the hippocampal tissue and of microglia among the tumour cells. Confocal experiments confirmed increasing tumour cell infiltration into the hippocampal slice with time (P<0.001), associated with cell death (σ=0.313, P=0.022). Ki67 showed increased proliferation (P<0.001), of both tumour cells and Iba1+ microglia and increased microglial phagocytosis (CD68: P<0.001). Expression of pro-inflammatory cytokines IL1, IL6 and TNFα were downregulated with expression of the anti-inflammatory cytokine TGFß1 maintained. CONCLUSION: This model allows study of the proliferation and infiltration of astrocytic tumour cells in central nervous system tissue and their interaction with microglia. Our data suggest that microglial function is altered in the presence of tumour cells, putatively facilitating tumour progression. Manipulation of the microglial functional state may have therapeutic value for astrocytic tumours.
Assuntos
Astrocitoma/patologia , Neoplasias Encefálicas/patologia , Comunicação Celular/fisiologia , Microglia/imunologia , Animais , Astrocitoma/imunologia , Neoplasias Encefálicas/imunologia , Citocinas/biossíntese , Imuno-Histoquímica , Microglia/citologia , Microscopia Confocal , Técnicas de Cultura de Órgãos , Fenótipo , Ratos , Ratos Wistar , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
AIMS: In Alzheimer's disease (AD), microglial activation prompted by the presence of amyloid has been proposed as an important contributor to the neurodegenerative process. Conversely following Aß immunization, phagocytic microglia have been implicated in plaque removal, potentially a beneficial effect. We have investigated the effects of Aß42 immunization on microglial activation and the relationship with Aß42 load in human AD. METHODS: Immunostaining against Aß42 and microglia (CD68 and HLA-DR) was performed in nine immunized AD cases (iAD - AN1792, Elan Pharmaceuticals) and eight unimmunized AD (cAD) cases. RESULTS: Although the Aß42 load (% area stained of total area examined) was lower in the iAD than the cAD cases (P=0.036), the CD68 load was higher (P=0.046). In addition, in the iAD group, the CD68 level correlated with the Aß42 load, consistent with the immunization upregulating microglial phagocytosis when plaques are present. However, in two long-surviving iAD patients in whom plaques had been extensively cleared, the CD68 load was less than in controls. HLA-DR quantification did not show significant difference implying that the microglial activation may have related specifically to their phagocytic function. CD68 and HLA-DR loads in the pons were similar in both groups, suggesting that the differences in microglial activation in the cortex were due to the presence of AD pathology. CONCLUSION: Our findings suggest that Aß42 immunization modifies the function of microglia by increasing their phagocytic activity and when plaques have been cleared, the level of phagocytosis is decreased below that seen in unimmunized AD.
Assuntos
Doença de Alzheimer/imunologia , Doença de Alzheimer/terapia , Vacinas contra Alzheimer/imunologia , Precursor de Proteína beta-Amiloide/metabolismo , Microglia/imunologia , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/imunologia , Peptídeos beta-Amiloides/uso terapêutico , Antígenos CD/imunologia , Antígenos CD/metabolismo , Antígenos de Diferenciação Mielomonocítica/imunologia , Antígenos de Diferenciação Mielomonocítica/metabolismo , Encéfalo/imunologia , Encéfalo/metabolismo , Encéfalo/patologia , Ensaios Clínicos Fase I como Assunto , Feminino , Humanos , Imuno-Histoquímica , Masculino , Microglia/metabolismo , Microscopia Confocal , Pessoa de Meia-Idade , Placa Amiloide/patologia , Placa Amiloide/terapiaRESUMO
A major feature of Alzheimer's disease is the accumulation of amyloid-beta peptide (Abeta) in the brain both in the form of plaques in the cerebral cortex and in blood vessel as cerebral amyloid angiopathy (CAA). Experimental models and human clinical trials have shown that accumulation of Abeta plaques can be reversed by immunotherapy. In this study, we hypothesized that Abeta in plaques is solubilized by antibodies generated by immunization and drains via the perivascular pathway, detectable as an increase in cerebrovascular Abeta. We have performed a follow up study of Alzheimer's disease patients immunized against Abeta42. Neuropathological examination was performed on nine patients who died between four months and five years after their first immunization. Immunostaining for Abeta40 and Abeta42 was quantified and compared with that in unimmunized Alzheimer's disease controls (n = 11). Overall, compared with these controls, the group of immunized patients had approximately 14 times as many blood vessels containing Abeta42 in the cerebral cortex (P<0.001) and seven times more in the leptomeninges (P = 0.013); among the affected blood vessels in the immunized cases, most of them had full thickness and full circumference involvement of the vessel wall in the cortex (P = 0.001), and in the leptomeninges (P = 0.015). There was also a significantly higher level of cerebrovascular Abeta40 in the immunized cases than in the unimmunized cases (cortex: P = 0.009 and leptomeninges: P = 0.002). In addition, the immunized patients showed a higher density of cortical microhaemorrhages and microvascular lesions than the unimmunized controls, though none had major CAA-related intracerebral haemorrhages. The changes in cerebral vascular Abeta load did not appear to substantially influence the structural proteins of the blood vessels. Unlike most of the immunized patients, two of the longest survivors, four to five years after first immunization, had virtually complete absence of both plaques and CAA, raising the possibility that, given time, Abeta is eventually cleared from the cerebral vasculature. The findings are consistent with the hypothesis that Abeta immunization results in solubilization of plaque Abeta42 which, at least in part, exits the brain via the perivascular pathway, causing a transient increase in the severity of CAA. The extent to which these vascular alterations following Abeta immunization in Alzheimer's disease are reflected in changes in cognitive function remains to be determined.
Assuntos
Doença de Alzheimer/terapia , Vacinas contra Alzheimer/uso terapêutico , Peptídeos beta-Amiloides/imunologia , Angiopatia Amiloide Cerebral/terapia , Fragmentos de Peptídeos/imunologia , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Vasos Sanguíneos/metabolismo , Angiopatia Amiloide Cerebral/metabolismo , Angiopatia Amiloide Cerebral/patologia , Córtex Cerebral/irrigação sanguínea , Córtex Cerebral/metabolismo , Hemorragia Cerebral/etiologia , Feminino , Seguimentos , Humanos , Imunoterapia Ativa/métodos , Masculino , Meninges/irrigação sanguínea , Meninges/metabolismo , Pessoa de Meia-Idade , Fragmentos de Peptídeos/metabolismo , SolubilidadeRESUMO
Early HIV-1 invasion of the central nervous system has been demonstrated by many cerebrospinal fluid studies; however, most HIV-1 carriers remain neurologically unimpaired during the so called "asymptomatic" period lasting from seroconversion to symptomatic AIDS. Therefore, neuropathological studies in the early pre-AIDS stages are very few, and the natural history of central nervous system changes in HIV-1 infection remains poorly understood. Examination of brains of asymptomatic HIV-1 positive individuals who died accidentally and of rare cases with acute fatal encephalopathy revealing HIV infection, and comparison with experimental simian immunodeficiency virus and feline immunodeficiency virus infections suggest that, invasion of the CNS by HIV-1 occurs at the time of primary infection and induces an immunological process in the central nervous system. This includes an inflammatory T-cell reaction with vasculitis and leptomeningitis, and immune activation of brain parenchyma with increased number of microglial cells, upregulation of major histocompatibility complex class II antigens and local production of cytokines. Myelin pallor and gliosis of the white matter are usually found and are likely to be the consequence of opening of the blood brain barrier due to vasculitis; direct damage to oligodendrocytes by cytokines may also interfere. These white matter changes may explain, at least partly, the early cerebral atrophy observed, by magnetic resonance imaging, in asymptomatic HIV-1 carriers. In contrast, cortical damage seems to be a late event in the course of HIV-1 infection. There is no significant neuronal loss at the early stages of the disease, no accompanying increase in glial fibrillary acid protein staining in the cortex, and only exceptional neuronal apoptosis. Although HIV-1 proviral DNA may be demonstrated in a number of brains, viral replication remains very low during the asymptomatic stage of HIV-1 infection. This makes it likely that, although opening of the blood brain barrier may facilitate viral entry into the brain, specific immune responses including both neutralising antibodies and cytotoxic T-lymphocytes, continuously inhibits viral replication at that stage.
Assuntos
Síndrome da Imunodeficiência Adquirida/patologia , Encéfalo/patologia , HIV-1 , Animais , Portador Sadio , Síndrome de Imunodeficiência Adquirida Felina/patologia , Humanos , Síndrome de Imunodeficiência Adquirida dos Símios/patologia , Fatores de TempoRESUMO
Prion diseases are chronic, fatal neurodegenerative conditions of the CNS. We have investigated the role of monocyte chemoattractant protein-1 (MCP-1) in the ME7 model of murine prion disease. MCP-1 expression increased in the CNS throughout disease progression and was positively correlated with microglial activation. We subsequently compared the inflammatory response, pathology and behavioural changes in wild-type (wt) mice and MCP-1 knockout mice (MCP-1-/-) inoculated with ME7. Late-stage clinical signs were delayed by 4 weeks in MCP-1-/- mice, and survival time increased by 2-3 weeks. By contrast, early changes in affective behaviours and locomotor activity were not delayed in onset. There was also no difference in microglial activation or neuronal death in the hippocampus and thalamus of wt mice and MCP-1-/- mice. These results highlight an important dissociation between prolonged survival, early behavioural dysfunction and hippocampal/thalamic pathology when considering therapeutic intervention for human prion diseases and other chronic neurodegenerative conditions.
Assuntos
Quimiocina CCL2/genética , Encefalite/metabolismo , Gliose/metabolismo , Microglia/metabolismo , Degeneração Neural/metabolismo , Doenças Priônicas/metabolismo , Animais , Comportamento Animal/fisiologia , Morte Celular/genética , Modelos Animais de Doenças , Encefalite/genética , Encefalite/fisiopatologia , Feminino , Gliose/genética , Gliose/fisiopatologia , Hipocampo/metabolismo , Hipocampo/patologia , Hipocampo/fisiopatologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Degeneração Neural/genética , Degeneração Neural/fisiopatologia , Proteínas PrPSc/toxicidade , Doenças Priônicas/genética , Doenças Priônicas/fisiopatologia , Taxa de Sobrevida , Tálamo/metabolismo , Tálamo/patologia , Tálamo/fisiopatologiaRESUMO
Mouse-adapted scrapie strains have been characterized by vacuolation profiles and incubation times, but the behavioral consequences have not been well studied. Here, we compared behavioral impairments produced by ME7, 79A, 22L, and 22A strains in C57BL/6J mice. We show that early impairments on burrowing, glucose consumption, nesting and open field activity, and late stage motor impairments show a very similar temporal sequence in ME7, 79A, and 22L. The long incubation time of the 22A strain produces much later impairments. However, the strains show clear late stage neuropathological differences. All strains showed clear microglial activation and synaptic loss in the hippocampus, but only ME7 and 79A showed significant CA1 neuronal death. Conversely, 22L and 22A showed significant cerebellar Purkinje neuron loss. All strains showed marked thalamic neuronal loss. These behavioral similarities coupled with clear pathological differences could serve to identify key circuits whose early dysfunction underlies the neurological effects of different prion strains.
Assuntos
Comportamento Animal/fisiologia , Sistema Nervoso Central/patologia , Sistema Nervoso Central/fisiopatologia , Doenças Priônicas/patologia , Doenças Priônicas/fisiopatologia , Príons/metabolismo , Animais , Córtex Cerebelar/patologia , Córtex Cerebelar/fisiopatologia , Modelos Animais de Doenças , Progressão da Doença , Comportamento Alimentar/fisiologia , Feminino , Gliose/patologia , Glucose/metabolismo , Hipocampo/patologia , Hipocampo/fisiopatologia , Camundongos , Camundongos Endogâmicos C57BL , Microglia/fisiologia , Comportamento de Nidação/fisiologia , Proteínas PrPSc/metabolismo , Tálamo/patologia , Tálamo/fisiopatologia , Fatores de TempoRESUMO
Previous studies from our laboratory have shown the ME7 model of murine scrapie to be accompanied by an atypical inflammatory response that is characterized by marked astroglial and microglial activation but also by the lack of significant expression of the pro-inflammatory cytokines interleukin (IL)-1beta and IL-6. The aim of this study was to determine whether, in the absence of IL-1beta and IL-6, tumour necrosis factor (TNF)-alpha may play an equivalent pro-inflammatory role, or if an anti-inflammatory cytokine profile dominates. We have used competitive polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) to determine the levels of TNF-alpha, IL-10 and transforming growth factor (TGF)-beta1 in the ME7 model, using their expression in lipopolysaccharide (LPS)-induced acute inflammation as a positive control. Levels of mRNA were elevated for all three cytokines during acute inflammation, while TGF-beta1 mRNA alone was significantly elevated in ME7-injected brains. Similarly, by ELISA, we detected elevated IL-10, TNF-alpha and TGF-beta1 in LPS-injected animals but only significant elevation of TGF-beta1 in ME7-injected animals. An increase in laminin and collagen IV deposition around blood vessels was also observed and is consistent with up-regulation by active TGF-beta1. These findings suggest that TGF-beta1 may play a central role in maintenance of an atypical microglial phenotype and may also be involved in vascular and extracellular matrix changes.
Assuntos
Doenças Priônicas/metabolismo , Fator de Crescimento Transformador beta/metabolismo , Animais , Vasos Sanguíneos/metabolismo , Citocinas/genética , Ensaio de Imunoadsorção Enzimática , Matriz Extracelular/metabolismo , Feminino , Mediadores da Inflamação/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Reação em Cadeia da Polimerase , RNA Mensageiro/metabolismo , Fator de Crescimento Transformador beta1RESUMO
Nitric oxide (NO) has been implicated in neurotoxicity and cerebral blood flow changes in chronic neurodegeneration, but its activity in the mammalian prion diseases has not been studied in detail. Nicotine adenine dinucleotide phosphate (NADPH)-diaphorase (NADPH-d) histochemistry is a simple and robust histochemical procedure that allows localization of the tissue distribution of NO synthases. The aim of the present study is to assess whether NADPH-d histochemical activity is altered in the hippocampus in the ME7 model of prion disease in C57BL/6J mice. At early and late stages after the initiation of the disease we assessed features of the NADPH-d positive cells and the neuropil histochemical activity in CA1 and dentate gyrus using densitometric analysis. In C57BL/6J mice 13 weeks postinjection of the prion agent ME7, when behavioural changes first become apparent, neuropil NADPH-d histochemical staining increases, whereas at late stages it decreases dramatically. Both type I and type II NADPH-d positive cells were found to survive throughout the hippocampal formation into the late stages of the disease, but diaphorase activity was reduced in dendritic branches and abnormal varicosities were present in both dendritic and axonal processes of NADPH-d positive type I cells. The pathophysiological implications of the results remain to be investigated but both blood flow alteration and NO neurotoxicity may be features of the disease.
Assuntos
Hipocampo/patologia , NADPH Desidrogenase/metabolismo , Neurônios/patologia , Neurópilo/patologia , Doenças Priônicas/patologia , Algoritmos , Animais , Contagem de Células , Dendritos/metabolismo , Dendritos/patologia , Densitometria , Hipocampo/metabolismo , Imuno-Histoquímica , Camundongos , Camundongos Endogâmicos C57BL , Neurônios/metabolismo , Neurópilo/metabolismo , Óxido Nítrico/metabolismo , Óxido Nítrico Sintase/biossíntese , Óxido Nítrico Sintase Tipo I , Doenças Priônicas/metabolismo , Fluxo Sanguíneo Regional/fisiologia , Sinapses/fisiologia , Fixação de TecidosRESUMO
To investigate neuropathological processes involved in HIV infection, a longitudinal analysis of central nervous system (CNS) changes was performed using the SIV-infected macaque model. Five animals were studied during the early phase and 13 during the asymptomatic and symptomatic phases. Histopathological analyses were performed on one cerebral fixed hemisphere whereas on the other frozen hemisphere in situ hybridisation, immunohistochemistry and RT-PCR were performed. Viral load was quantified by in situ hybridisation, CD4 and CD8 T cell infiltration by immunohistochemistry and mRNA cytokine expression (IL1beta, IL2, IL6, TNFalpha, IFNgamma and TGF-beta1) by semiquantitative RT-PCR. As reported for HIV-infected humans, the neuropathological analysis of SIV infected animals revealed four distinct lesion profiles: minimal changes, early encephalitis, leukoencephalopathy and encephalitis. No relationship was found between neuropathological findings, numbers of SIV replicating cells and T cell infiltration. CNS infection was found to be an early event characterised by glial activation, an increase in the level of IL1beta, TNFalpha and IL6 mRNA expression. During the asymptomatic and symptomatic phases, IL6 and IL1beta mRNAs increase coincided with gliosis and the development of myelin lesions. The absence of relationship between neuropathological findings and viral load suggests that cerebral lesions are caused by an indirect mechanism. Inflammatory cytokine pattern associated with severe lesions show the key role of glial activation in the SIV neuropathological process.
Assuntos
Complexo AIDS Demência/patologia , Complexo AIDS Demência/virologia , Síndrome de Imunodeficiência Adquirida dos Símios/patologia , Síndrome de Imunodeficiência Adquirida dos Símios/virologia , Vírus da Imunodeficiência Símia , Complexo AIDS Demência/imunologia , Animais , Relação CD4-CD8 , Citocinas/genética , Citocinas/metabolismo , Encefalite/patologia , Encefalite/virologia , Hibridização In Situ , Leucoencefalopatia Multifocal Progressiva/patologia , Leucoencefalopatia Multifocal Progressiva/virologia , Macaca mulatta , Reação em Cadeia da Polimerase , RNA Mensageiro/metabolismo , Síndrome de Imunodeficiência Adquirida dos Símios/imunologiaRESUMO
To assess the susceptibility of resident microglia to simian immunodeficiency virus (SIV) infection, we analysed the brains of rhesus macaques after intracerebral (i.c.) inoculation of the virus into the central region at 7 days, 1, 2 and 3 months post-inoculation (p.i.). The brains of animals showed the same moderate neuropathological changes in central, frontal and parietal regions of the brain, characterized by gliosis, microglial nodules, perivascular infiltrates and occasional white matter pallor and similar low numbers of infected cells detected by in situ hybridization. These results, showing that i.c. inoculation did not lead to preferential infection of brain tissue, even near the inoculation point at 7 days p.i., provide evidence for the low susceptibility of resident microglia to SIV replication during the early stages of infection.
Assuntos
Encéfalo/virologia , Microglia/virologia , Síndrome de Imunodeficiência Adquirida dos Símios/fisiopatologia , Vírus da Imunodeficiência Símia/fisiologia , Replicação Viral , Animais , Encéfalo/patologia , Demência/patologia , Demência/virologia , Imuno-Histoquímica , Hibridização In Situ , Macaca mulatta , Masculino , Microglia/patologia , Síndrome de Imunodeficiência Adquirida dos Símios/patologia , Fatores de TempoRESUMO
The neuropathology associated with HIV (Human Immunodeficiency Virus) infection is one of the major complications of this disease. The virological and cellular mechanisms by which HIV infection induces motor and cognitive disorders remain unknown. This lack of understanding of the pathophysiology is partly due to the difficulty of experimental analysis in man because only post-mortem samples from terminal phases of the disease and cerebrospinal fluid samples are available. Two animal models, very closely resembling human HIV infection, are available: the cat model infected by FIV (Feline Immunodeficiency Virus) and the macaque model infected by the SIVmac (Simian Immunodeficiency Virus) which have enabled us to conduct a longitudinal study of encephalopathy during primo-infection and the asymptomatic and pre-AIDS (Acquired Immune Deficiency Syndrome) phases. In the cat-FIV model, which presents the advantage of being non-infectious to man, and therefore easier to manipulate, it was shown that infected cats develop behavioural abnormalities and a neuropathology which resemble HIV dementia. Central nervous system lesions induced by FIV are similar to those of HIV infection apart from the absence of multinucleated giant cells. This model was used to analyse the relationship between CNS lesions and the viral load of the brain and showed that the severity of the lesions contrasted with a low viral load. The pathophysiology of SIVmac infection in the rhesus macaque is almost identical to human infection with a more rapid course, since the duration of the asymptomatic phase is 6 months to 5 years, depending on the animal. We studied the relationship between lesions, viral load and cytokine production (IL-1 beta, IL-2, IL-6, TNF alpha, INF gamma, TGF-beta 1) within the CNS. Our results show early, low-grade and constant infection of the brain. The dissociation between the viral load and the lesions observed is our favour of an indirect mechanism for the pathogenesis of these lesions. The relationship between lesions and the cytokine profile studied shows the importance of glial cells in the pathogenesis of the lesions.
Assuntos
Complexo AIDS Demência/fisiopatologia , Síndrome da Imunodeficiência Adquirida/complicações , Modelos Animais de Doenças , Complexo AIDS Demência/patologia , Animais , Gatos , Síndrome de Imunodeficiência Adquirida Felina/patologia , Síndrome de Imunodeficiência Adquirida Felina/fisiopatologia , Vírus da Imunodeficiência Felina , Macaca , Síndrome de Imunodeficiência Adquirida dos Símios/patologia , Síndrome de Imunodeficiência Adquirida dos Símios/fisiopatologia , Vírus da Imunodeficiência SímiaRESUMO
The FIV (feline immunodeficiency virus) induces in cats brain changes presenting similarities with those observed in human immunodeficiency virus infection. This FIV model was used to study the relationship between viral load in brain, in lymphoid organs and central nervous system (CNS) changes during the early and late stages of infection. Early brain changes were analyzed in animals experimentally infected with two different FIV isolates and sacrificed at 7 and 15 days, 1, 2, 6, and 12 months post inoculation (p.i.). Late CNS abnormalities were analyzed in naturally FIV-infected cats referred to the Veterinary School of Nantes. For each animal, one cerebral hemisphere was fixed and examined using routine techniques. The characterization of FIV replicating cells by in situ hybridization was performed on the other half frozen hemisphere on sections performed in the anterior and the median regions of the brain. During the early stages of infection, moderate gliosis with glial nodules and sometimes white matter pallor and meningitis were associated with few infected cells scattered in the brain. Infection was an early event as infected cells could be detected in brain at 7 p.i. For each cat, these findings were found identical in the two analyzed areas. During the late stages, brain lesions and the number of virus replicating cells increased especially in animals with perivascular infiltrates. The multinucleated giant cells encephalitis was never observed and the number of FIV replicating cells scattered in the whole brain was always low. This discrepancy between the number of replicating cells and the brain lesions, corroborates the hypotheses suggesting that brain injuries may be mediated via diffusive factors and amplification processes through cytokine cascades and cell activations.