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    ABSTRACT: The introduction of Highly Active Anti-retroviral Therapy (HAART) has resulted in significant decreases in morbidity and mortality for subjects infected with HIV. The brain is a major target organ for HIV resulting in significant neuropathological changes in most HIV infected subjects and a wide range of clinical neurological symptoms including HIV associated dementia. In the pre-HAART era HIV associated dementia was a common complication of AIDS. However, since the introduction of HAART the incidence of HIV associated dementia has fallen, but the prevelance has actually risen due to the increasing number of infected subjects and increased life expectancy. HIV associated dementia correlates most closely with neuroinflammation rather than directly with viral load or HIV encephalitis. HIV related clinical and neuropathological disorders are more prevalent in drug abusers than in other risk groups. This review focuses on the shifting pathology observed in HIV infected subjects since the introduction of HAART, discussing the clinical manifestations of these and the influence of confounding factors such as drug abuse and Hepatitis C co-infection.
    International Review of Psychiatry 03/2008; 20(1):15-24. DOI:10.1080/09540260701862037
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    Developmental Medicine & Child Neurology 02/2008; 50(1):6-7. DOI:10.1111/j.1469-8749.2007.00006.x
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    ABSTRACT: There are many excellent reviews of HIV infection of the nervous system. However these all assume that the reader has a working knowledge of the structure and cellular architecture of the brain. It may be that specialised brain vocabulary represents an unwelcome hurdle for those scientists with expert knowledge of the effects of HIV in other cell systems and who wish to extend that interest to the brain. This review provides an introduction to the component structures and cells of the brain and an overview of their involvement in HIV/AIDS. HIV infection leads to death through its capacity to progressively devastate the immune system. Current anti-HIV therapy has achieved considerable success in halting and partially reversing this process. In the absence of treatment, the breakdown of immunity is marked by declining CD4 counts and increasing vulnerability to opportunistic infections. In parallel with these effects on the lymphoid system, the nervous system is frequently the site of an initially stealthy infection which leads ultimately to symptomatic disease in a significant proportion of HIV infected individuals. The most feared manifestation of central nervous system (CNS) involvement is dementia. Unfortunately, serial CD4 counts and measurement of blood viral load do not serve to identify or monitor early infection of brain tissue. Since effective anti-HIV therapy has not achieved eradication of virus from lymphoid tissues, and anti-HIV drugs do not enter the nervous system easily, it is hardly surprising that HIV infection of the nervous system continues to cause clinical problems. Even in treatment-compliant patients, a measurable degree of cognitive impairment may develop, signalling previous or present HIV-related brain injury. The cause of HIV associated dementia and cognitive disability remains poorly understood. Perhaps most significantly, the long-term consequences of clinically occult brain infection are unknown and will require further investigation.
    Current HIV Research 08/2006; 4(3):249-57. DOI:10.2174/157016206777709401
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    ABSTRACT: Despite two decades of research, certain aspects of HIV-related central nervous system (CNS) disease remain poorly understood. HIV targets microglia and macrophages within the CNS and enters the brain compartment early. However, HIV is there held in check apparently until the onset of significant immune compromise, when viral replication, microglial activation, neuronal damage, and cognitive impairment are likely to ensue. Illicit drug abuse continues to be a significant risk factor for HIV transmission worldwide. Whether HIV-related CNS disease is more prevalent or more severe in this risk group has long been debated. Drugs of abuse can of themselves cause immune suppression, blood-brain barrier breakdown, microglial activation, and neuronal injury. This review presents evidence that HIV associated CNS disorders are indeed accentuated in drug abusers. However, the advent of effective therapy has added a new dimension, which must be taken into consideration. Treated individuals are surviving much longer and HIV encephalitis and HIV-associated dementia have become much less common. However, more subtle forms of CNS damage are emerging. Examination of the brains of individuals who have been treated long term with highly active antiretroviral therapy (HAART) reveals a surprising degree of microglial activation, comparable at times to that seen formerly in milder cases of HIV encephalitis. In addition, these individuals show evidence of increased deposition of neurodegenerative proteins, particularly hyperphosphorylated tau. Similar observations have been made in young opiate abusers who are HIV negative. Taken together, these results suggest that neuroinflammation and neurodegeneration, which are clinically silent at present, may cause problems in the future in HAART-treated subjects.
    Journal of Neuroimmune Pharmacology 07/2006; 1(2):182-91. DOI:10.1007/s11481-006-9018-2
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    ABSTRACT: This study aims to investigate the influence of human immunodeficiency virus (HIV) infection on the neurodegenerative processes normally associated with ageing. We have looked for evidence of beta amyloid and hyperphosphorylated Tau deposition in HIV-infected subjects before and after the advent of highly active anti-retroviral therapy (HAART). In addition we have looked for evidence of axonal damage. We have compared these HIV-positive cases with age-matched controls and with older non-demented controls. We find no evidence of significant premature beta amyloid deposition in HIV-infected cases; however, we do observe elevated levels of hyperphosphorylated Tau in the hippocampus of many HIV-infected subjects, compared with age-matched controls. The greatest levels of hyperphosphorylated Tau are noted in HAART-treated subjects. Axonal damage marked by expression of beta amyloid pre-cursor protein (BAPP) was highly variable in all groups including control subjects. We surmise that HIV infection and/or the use of anti-retroviral therapy may predispose to accelerated neuroageing in the form of hyperphosphorylated Tau deposition in the hippocampus. Within the age groups studied these significant neuropathological changes remained subclinical and were not yet associated with cognitive impairment.
    Acta Neuropathologica 07/2006; 111(6):529-38. DOI:10.1007/s00401-006-0037-0
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    ABSTRACT: Although descriptive classifications of meningioma subtypes are well established, there has been inconsistency in the categorization of meningiomas into benign, atypical and anaplastic groups. The aim of this study was to reassess the incidence of atypical (grade II) meningiomas over a 10-year period by applying the World Health Organization (WHO) 2000 classification system. A secondary aim was to determine if grade II and III tumours were becoming more common. Sections of 314 meningiomas resected between 1994 and 2003 were retrieved from the archives of the Western General Hospital's neuropathology unit in Edinburgh. They were reassessed and graded by using the WHO 2000 classification system. The reviewers were blind to the original classification and grading. There was a gradual increase in the numbers of meningiomas being resected annually over the 10-year period. On reclassification, 78% of the meningiomas were classified as grade I, 20.4% as grade II and 1.6% as grade III. With regard to grade II meningiomas classified by using the WHO 2000 classification system, 38.1% had originally been classified as grade I prior to 2000, whereas 13.6% had originally been classified as grade I after 2000. In most cases, reclassification was due to formal counts of mitotic figures. Atypical meningiomas are diagnosed more frequently under the current WHO classification system than they were under the previous classification systems. Although the current WHO (2000) classification is more prescriptive than its predecessors, interobserver variability is likely to remain because of the subjective nature of some of the criteria.
    Neuropathology and Applied Neurobiology 05/2005; 31(2):141-9. DOI:10.1111/j.1365-2990.2004.00621.x
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    ABSTRACT: This review compares the neuropathology of highly active antiretroviral therapy (HAART)-treated HIV+ individuals with the reported central nervous system (CNS) findings from the pre-HAART era. HAART has had considerable success in combating HIV-related immune collapse and has prevented many of the former end-stage complications of AIDS. However, with increased survival times the prevalence of minor HIV-associated cognitive impairment appears to be rising among treated patients and this may be a particular risk for older individuals. HIV encephalitis (HIVE) is still prevalent in treated patients although attenuated forms of HIVE and CNS opportunistic disorders are also observed. Some subjects show very significant CNS lymphocytic infiltrates in the context of HAART-induced immune reconstitution. HIV-associated cognitive impairment correlates best with the increased presence of activated, though not necessarily infected, microglia and CNS macrophages. This suggests that indirect mechanisms of neuronal injury and loss occur in HIV/AIDS as a basis for dementia since neurones are not themselves productively infected. Research to elucidate the mechanisms of neuronal injury in HIV/AIDS may contribute to the understanding of CNS function not only in HAART-treated subjects but also in other neurodegenerative disorders.
    Histopathology 01/2005; 45(6):549-59. DOI:10.1111/j.1365-2559.2004.02004.x
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    ABSTRACT: We aimed to assess the effects of human immunodeficiency virus (HIV) encephalitis (HIVE) on the B-lymphocyte population of the brain. We also tested the effects of intravenous opiate drug abuse because this is a major risk factor for infection, with known immunosuppressive properties. Immunohistochemistry was used to identify B lymphocytes in the brains of clinically well-characterized HIV-negative drug abusers, individuals with HIVE, and, for comparison, HIV-negative individuals with encephalitis. Perivascular and parenchymal B lymphocytes were studied in 11 regions of each brain. We found that despite a small apparent rise, the abuse of opiate drugs had no significant effect on the B-lymphocyte population of the brain. Individuals with HIVE were found to have a greater number of B lymphocytes in brain tissue than individuals with acquired immunodeficiency syndrome (AIDS) who had no central nervous system (CNS) pathology. However, in comparison to nonimmunocompromised individuals with encephalitis, the B-lymphocyte population of HIVE brains was greatly reduced. We suggest that this latter finding may be linked to declining CD4 T-lymphocyte levels in end-stage AIDS, and that CD4 T lymphocytes may be required for efficient entry of B lymphocytes to the CNS. The brain B-lymphocyte population correlated well with CD4 T-lymphocyte level in the blood, in cases with viral encephalitis. These findings suggest that systemic immune competence is required to mount a full B-lymphocyte response to viral CNS infections. Furthermore, we suggest that CD4 T lymphocytes may play a key role in the humoral immune response to viral infection of the brain.
    Journal of NeuroVirology 07/2004; 10(3):181-8. DOI:10.1080/13550280490444100
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    ABSTRACT: To investigate the pathological evidence for a possible interaction between drugs of abuse and HIV infection in terms of microglial responses in early and late HIV/AIDS, and to discuss the possible long-term consequences of microglial activation in chronic HIV infection. This brain pathology study compared age and sex-matched control patients with HIV-negative intravenous drug users, and with HIV-positive drug users both in the presymptomatic stage and with AIDS. A further group of non-drug-using AIDS patients was included. All the AIDS patients had HIV encephalitis (HIVE) but no other significant HIV-associated brain pathology. Microglia/macrophages were identified in the grey and white matter of the frontal and temporal lobes and the thalamus, using antibodies to CD68 and MHCII. Objective quantitation was used to compare subjects in the different groups. AIDS patients showed a significant increase in activated microglia/macrophages in both the grey and white matter of all areas compared with non-AIDS patients. Drug users with HIVE tended to have more activated microglia than non-drug-using comparison groups, but this difference was not found in all brain areas studied. Drug misuse appears to enhance the microglial activation resulting from HIV infection in some individuals. Other factors such as the severity of HIVE, or systemic immune factors, are also likely to affect the degree of microglial activation. The implications for drug-using patients who survive long term with HIV/AIDS are discussed, particularly in relation to premature neurodegeneration.
    AIDS 02/2004; 18 Suppl 1(Supplement 1):S69-74. DOI:10.1097/00002030-200418001-00010
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    ABSTRACT: The Edinburgh cohort of intravenous drug users (IVDUs) became infected with HIV between 1983 and 1984. Before the era of effective therapy, many of these infected IVDUs displayed cognitive impairments on progressing to AIDS and were found to have HIV encephalitis (HIVE). Full autopsies were conducted on these patients, providing an opportunity to study the intersecting pathology of pure HIVE and drug use. High proviral load in the brain correlated well with the presence of giant cells and HIV p24 positivity. In presymptomatic HIV infection, IVDUs were found to have a lymphocytic infiltrate in the central nervous system (CNS). Apart from the expected microglial activation in the presence of HIV infection of the CNS, drug use in its own right was found to be associated with microglial activation. Examination of HIV-negative IVDUs revealed a number of neuropathologic features, including microglial activation, which may underpin HIV-related pathology in the CNS. HIV isolated from different regions of the brain was exclusively of R5-tropic type throughout the course of infection. Detailed studies of p17 and V3 sequences suggest that viral sequestration occurs in the CNS before the onset of AIDS and that increasing diversity of HIV variants within the brain is associated with increasing severity of HIVE. Because brain isolates have proved to be different from those in lymphoid tissue (and blood), it is likely that selective neuroadaptive pressures operate before HIVE supervenes. Drug abuse may be synergistic in this process through activation of microglia, breakdown of the blood-brain barrier, and direct neurotoxicity. Collections of clinically well-characterized HIV-infected tissues such as those in the Edinburgh Brain Bank are a vital resource to support ongoing studies of viral pathogenesis in the CNS and interactions with drug abuse.
    JAIDS Journal of Acquired Immune Deficiency Syndromes 11/2002; 31 Suppl 2:S35-42. DOI:10.1097/00126334-200210012-00003
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BMC Immunology 03/2010; 11(1):12. DOI:10.1186/1471-2172-11-12
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