Early entry and widespread cellular involvement of HIV-1 DNA in brains of HIV-1 positive asymptomatic individuals

There is overwhelming evidence that invasion of the central nervous system (CNS) by HIV-1 takes place at an early stage of the infection. It has been demonstrated that HIV-1 DNA is present in brains of asymptomatic individuals. Evidence of immune activation and increased expression of cytokines suggested that neuropathological changes and neuronal and axonal damage could be the effect of the presence of the virus. The purpose of the study is to ascertain whether target cells for HIV-1 in brain of patients at early stage of the infection are the same as those found in AIDS sufferers or if the distribution seen in AIDS patients results from the late spreading of the infection from cells considered traditionally the reservoir of the virus, i.e. microglial cells. Eighteen brains, all HIV-1 DNA positive, as shown by nested polymerase chain reaction (PCR), were selected among the group of HIV-1 positive asymptomatic cases. In 6 of them, HIV-1 DNA was detected by PCR in situ. Positive cells included astrocytes and endothelial cells, in addition to microglial cells. We conclude that astrocytes and endothelial cells are already infected at an early (asymptomatic) stage of the infection and suggest that they might contribute to the damage of the CNS.

[JC virus infection and lympho-plasmocytic infiltration of the central nervous system revealed by a cerebellar syndrome]

We report the case of a 74 year-old woman who had been treated since 8 years for a Waldenström's disease. She also was affected by a progressive multi-focal leukoencephalopathy. The interest of this case lies in two principal features. On the one hand, the clinical and radiological signs were restricted to the cerebellum and to the brainstem, on the other hand, brain examination revealed lymphocytes and plasma cells infiltration suggestive of an associated Bing and Neel syndrome.

Primary brain lymphoma cell turnover differs in patients with and without AIDS: relationships to bcl-2 expression and host cell reaction

Primary central nervous system lymphomas (PCNSLs) are more resistant to radiotherapy and chemotherapy in AIDS (A-PCNSLs) than in non-AIDS patients (NA-PCNSLs). We investigated 23 A-PCNSLs and 24 NA-PCNSLs. Lymphoma cell kinetics (i.e. proliferation [mitotic index, MIB-1 and PCNA labeling indices], apoptosis and turnover) were determined and compared with bcl-2 and LMP-1 expression, and to the percentage of tumor-infiltrating T-lymphocytes (T-TILs) and macrophages. A-PCNSLs showed lower proliferation (p < 0.005), less apoptosis (p < 0.0001) and slower cell-turnover (p < 0.0001) than NA-PCNSLs. LMP-1 was detected in 90% of A-PCNSLs and 5% of NA-PCNSLs, a finding correlating positively with bcl-2 expression (p < 0.0007). In contrast, T-TIL counts and CD4/CD8 T-TIL ratios were similar in A-PCNSLs and NA-PCNSLs. T-TIL counts correlated negatively with proliferation indices (from p < 0.05 to p < 0.0005) in NA-PCNSLs, but not in A-PCNSLs. Macrophage counts correlated positively with apoptosis in both groups. We concluded the following: (i) A-PCNSLs are characterized by accumulation of slow-cycling, long-lived cells that might be protected from apoptosis by LMP-1 induced bcl-2 expression, and independently from the host response; (ii) NA-PCNSLs are characterized by a faster cell turnover associated with an insufficient antiproliferative host response; and (iii) A-PCNSLs and NA-PCNSLs constitute 2 entities with distinctive morphology and different kinetic profiles that could account for different responses to therapy.

Upregulated expression of Fas and Fas ligand in brain through the spectrum of HIV-1 infection

Apoptosis of neurons and glial cells has been shown to occur in the brain of patients with the acquired immune deficiency syndrome (AIDS) and was postulated as contributing to brain atrophy and white matter damage in these patients. Since apoptotic events may be induced by the Fas-Fas ligand (FasL) system, we analyzed the relevance of these molecules to cell depletion in eight brains from HIV-1-infected patients and nine HIV-1-negative controls all of whom were analyzed histopathologically. The presence of Fas and FasL in brain tissue was analyzed by PCR amplification using Fas- and FasL-specific oligonucleotide primers and immunohistochemistry. The visualization of DNA fragmentation was used to evaluate apoptosis. Fas transcripts were detected in brains from each of four AIDS patients, each of three asymptomatic HIV-1 carriers and each of two HIV-1-negative controls. In the brains from AIDS patients the level of Fas expression was higher than in asymptomatic carriers and uninfected controls. FasL transcripts were seen in three of seven HIV-1-infected brains, two AIDS cases and one asymptomatic HIV-1 carrier. The predominant Fas-expressing cells were reactive astrocytes seen in each of two AIDS patients and one pre-AIDS case, but not in HIV-1-negative controls. Occasional Fas-positive oligodendrocyte-like cells were also seen in AIDS and pre-AIDS cases. No significant expression of Fas and FasL was seen in neurons. Fas-positive reactive astrocytes were more frequent in foci of HIV-1 encephalitis (HIVE). In the same area reactive apoptotic astrocytes were seen in close vicinity to FasL-expressing CD3 T lymphocytes, suggesting that apoptosis of astrocytes is mediated by Fas-FasL. The Fas expression on glial cells in asymptomatic HIV-1 infection may indicate apoptosis already in the asymptomatic stage of HIV-1 disease. In AIDS brains expression of Fas and FasL may contribute to the loss of glial cells and indirectly to the loss of neurons.

[A process of programmed cell death as a mechanisms of neuronal death in prion diseases]

Neuronal loss is a salient feature of prion diseases; however, its cause and mechanism, particularly its relationship with the accumulation of the pathogenic, protease resistant isoform PrPres of the cellular prion protein PrPc, are still unclear. A number of studies suggest that it could occur through a process of programmed cell death which is consistent with the lack of inflammation in these conditions. In this paper, we review the different techniques used to identify apoptosis of neurons, and analyse the studies demonstrating neuronal apoptosis in prion diseases, either experimentally, in animal or in human. Apoptosis of rat hippocampal neurons, in cultures exposed to a synthetic peptide homologous to the prion protein, has been identified on morphological criteria after staining by a fluorescent marker of DNA and by gel electrophoresis of neuronal DNA. Apoptosis of neurons has also been identified in vivo using in situ end labelling and electron microscopy in scrapie infected mice. In human, apoptotic neurons were identified by in situ end labelling in Creutzfeldt-Jakob Disease and in Fatal Familial Insomnia. Apoptotic neurons were mostly found in damaged regions and their presence and abundance seemed to correlate closely with neuronal loss. Neuronal apoptosis also correlated well with microglial activation as demonstrated by the expression of major histocompatibility complex class II, antigens, and with axonal damage as identified by beta-amyloid protein precursor immunostaining. In contrast, there was no clear correlation between the topography and severity of neuronal apoptosis and the type, topography and abundance of prion protein deposits as demonstrated by immunohistochemistry. Similarly, within the framework of comparable phenotypes, there was no difference in the abundance and distribution of apoptotic neurons according to the aetiology whether sporadic, familial, or iatrogenic, of the disease. The pathogenetic mechanism of neuronal apoptosis remains speculative and several hypothesis have been proposed. The lack of a direct association between neuronal damage and PrPres deposition may support models of neuropathogenesis based on "loss of function" of PrPc, such as withdrawal of defined activation signals inducing programmed cell death, rather than neurotoxicity. It is also possible that PrPres is neurotoxic and the dissociation between neuronal damage and the amount of protein only reflects variations in selective neuronal vulnerability. Finally, neuronal apoptosis might be an indirect consequence of PrPres deposition. PrPres-induced dendritic or axonal damage, perhaps enhanced by consequent microglial activation, might contribute to neuronal apoptosis either due to deafferentation or to retrograde neuronal degeneration.

[Fatal familial insomnia]

Since its description in 1986, Fatal Familial Insomnia (FFI) became the third most common inherited prion diseases (23 described families, 3 isolated cases). It is characterized by a mutation at codon 178 of the prion protein gene cosegregating with the methionine polymorphism at codon 129 of the mutated allele. Insomnia, dysautonomia, disruption of circadian rhythms and motor dysfunctions (myoclonus, ataxia, dysarthria, spasticity) are the main clinical symptoms in the homozygote patients (met/met at codon 129). Heterozygotes have motor dysfunctions from onset and cognitive changes. Pheno-typic variability does not appear to be strictly related to codon 129 polymorphism as recently stressed in some reports. Neuropathology shows marked neuronal loss and gliosis in the thalamus, especially in the medio-dorsal and antero-ventral nuclei, without any amyloïd deposits. Some spongiosis may be seen essentially in the cerebral cortex, in patients with longer duration disease. The D178N mutation coupled with the 129 valine codon is linked to a subtype of Creutzfeldt-Jakob disease. However, in these two phenotypically different diseases, two protease resistant fragments of the pathogenic PrP (PrPres) are accumulated. They differ in molecular mass. In FFI PrPres, the unglycosylated form is underrepresented. This particularity does not result from the preferential conversion of the glycosylated forms but from an inaccessibility of non glycosylated form to conversion. PrPres has been shown to be form allelic origin. Neuronal apoptosis was found to contribute to neuronal loss in FFI. Its presence correlates with neuronal loss, being invariably noticed in the thalamus and medullary nuclei. It is not correlated with PrPres accumulation. The quantity of deposits is globally low in FFI brains and rarely immunohistochemically detected. Pathogenesis of lesions and clinical signs remain to be assessed. Protein dysfunction could be hypothesized according to some clinical and experimental data as well as to the discordance between protein accumulation and programmed cell death. Neurotoxicity is also postulated. Studies on this pathology led to consider the existence of "strains" in human prion diseases. Despite remarkable advances, many issues remain unsolved in this non spongiform prion disease.

Prion disease with octapeptide repeat insertion

OBJECTIVE

About 8% of prion disease cases are familial and a few are due to an octapeptide repeat insertion (OPRI) in the prion protein gene. A suitable neuropathological examination has been performed in 20 cases from 9 families and in 3 isolated cases. The number of OPRI ranges from 4 to 9 multiples of 24 base-pair.

METHODS

Results from routine histopathological preparations and from immunohistochemistry performed after special tissue pretreatment were compared with those of molecular genetic investigation.

RESULTS

Eight cases with 4 to 7 multiples of OPRI exhibited characteristic elongated deposits in the cerebellar molecular layer, which were visible on slides prepared with antibodies against the prion protein only. Conversely, 6 cases with 8 or 9 multiples of OPRI presented typical plaques already obvious on routine preparations.

CONCLUSIONS

These variable modifications in the cerebellar molecular layer deserve to be underlined, in particular the elongated deposits which are characteristic for cases presenting 4 to 7 OPRI.

Histological demonstration of haemosiderin deposits in lungs and liver from victims of chronic physical child abuse

In the context of chronic physical child abuse, two entities have been described based on macroscopical and radiological criteria: the battered baby syndrome and the shaken baby syndrome. However, in some autopsy cases, clinico-radiological information may not be available. In these cases, histological examinations are necessary to look for sequelae of repeated haemorrhages, particularly in organs likely to have suffered traumatisms such as the lungs, or in organs belonging to the mononucleated macrophage resorption system, such as the liver and the spleen. We examined a series of 15 young children who died from proven chronic child abuse and compared them with 15 sex and age-matched control subjects who died from natural causes with no history of child abuse. Using Perl's stain for iron, we identified haemosiderin deposits in pulmonary, hepatic and splenic samples and the deposits were evaluated qualitatively and quantitatively. Haemosiderin deposits were significantly (P < 0.001) more abundant in the lungs and liver of the chronic abuse victims than in those of the control subjects. However, they were not significantly more abundant in the spleens of child abuse victims than in controls. We conclude that haemosiderin deposits in lungs and liver could be proposed as a marker for chronic physical child abuse. This study stresses the importance of systematic histological examination to look for pulmonary and hepatic haemosiderin deposits in cases in which chronic child abuse is suspected.

[Neuronal apoptosis in human prion diseases]

Neuronal loss is a salient feature of prion diseases; however, its causes and mechanisms are unclear. The possibility that it could occur through an apoptotic process has been postulated and this is consistent with the lack of inflammation in prion disorders as supported by experimental studies. In order to test this hypothesis in humans, we examined samples of frontal and temporal cerebral cortex, striatum, thalamus and cerebellum from 26 patients who died from prion diseases. They included 16 cases of Creutzfeldt-Jakob disease (5 sporadic cases, 5 familial, 3 iatrogenic, and 3 cases with the new variant), and 10 cases of fatal familial insomnia including 8 homozygotes methionine/methionone at codon 129 of the prion protein gene and 2 heterozygotes. These were compared with age and sex matched controls. Using in situ end labelling, we identified apoptotic neurons in all the cases of Creutzfeldt-Jakob disease. A single labelled neuron was found in the eldest control. Apoptotic neurons were mostly found in damaged regions and their presence and abundance seemed to correlate closely with neuronal loss. This supports the view that apoptosis of neurons is a feature of prion diseases and may contribute to the neuronal loss which is one of the main characteristics of these conditions. Neuronal apoptosis also correlated well with microglial activation as demonstrated by the expression of major histocompatibility complex class II antigens and axonal damage as identified by beta-amyloid protein precursor immunostaining. In contrast, we found no obvious relationship between the topography and severity of neuronal apoptosis and the type, topography and abundance of prion protein deposits as demonstrated by immunohistochemistry.

Viral load and neuropathology in the SIV model

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.

Neuronal apoptosis in Creutzfeldt-Jakob disease

Neuronal loss is a salient feature of prion diseases; however, its causes and mechanisms are unclear The possibility that it could occur through an apoptotic process has been postulated and is consistent with the lack of inflammation in prion disorders as supported by experimental studies. In order to test this hypothesis in humans, we examined samples of frontal and temporal cerebral cortex, striatum, thalamus, and cerebellum from 16 patients who died from Creutzfeldt-Jakob disease. They included 5 sporadic cases, 5 familial, 3 iatrogenic, and 3 cases with the new variant. These were compared with age and sex matched controls. Using in situ end labelling, we identified apoptotic neurons in all the cases of Creutzfeldt-Jakob disease. A single labelled neuron was found in the eldest control. Apoptotic neurons were mostly found in damaged regions and their presence and abundance seemed to correlate closely with neuronal loss. This supports the view that apoptosis of neurons is a feature of prion diseases and may contribute to the neuronal loss which is one of the main characteristics of these conditions. Neuronal apoptosis also correlated well with microglial activation, as demonstrated by the expression of major histocompatibility complex class II antigens, and axonal damage, as identified by beta-amyloid protein precursor immunostaining. In contrast, we found no obvious relationship between the topography and severity of neuronal apoptosis and the type, topography, and abundance of prion protein deposits as demonstrated by immunocytochemistry.

Increased peroxynitrite activity in AIDS dementia complex: implications for the neuropathogenesis of HIV-1 infection

Oxidative stress is suggested to be involved in several neurodegenerative diseases. One mechanism of oxidative damage is mediated by peroxynitrite, a neurotoxic reaction product of superoxide anion and nitric oxide. Expression of two cytokines and two key enzymes that are indicative of the presence of reactive oxygen intermediates and peroxynitrite was investigated in brain tissue of AIDS patients with and without AIDS dementia complex and HIV-seronegative controls. RNA expression of IL-1beta, IL-10, inducible nitric oxide synthase, and superoxide dismutase (SOD) was found to be significantly higher in demented compared with nondemented patients. Immunohistochemical analysis showed that SOD was expressed in CD68-positive microglial cells while inducible nitric oxide synthase was detected in glial fibrillary acidic protein (GFAP)-positive astrocytes and in equal amounts in microglial cells. Approximately 70% of the HIV p24-Ag-positive macrophages did express SOD, suggesting a direct HIV-induced intracellular event. HIV-1 infection of macrophages resulted in both increased superoxide anion production and elevated SOD mRNA levels, compared with uninfected macrophages. Finally, we show that nitrotyrosine, the footprint of peroxynitrite, was found more intense and frequent in brain sections of demented patients compared with nondemented patients. These results indicate that, as a result of simultaneous production of superoxide anion and nitric oxide, peroxynitrite may contribute to the neuropathogenesis of HIV-1 infection.

Neuronal apoptosis does not correlate with dementia in HIV infection but is related to microglial activation and axonal damage

To characterize the distribution of apoptotic neurons and their relationships with the stage of disease, a history of HIV-dementia, and the degree of productive HIV infection, microglial activation and axonal damage, we examined the brains of 40 patients. Samples of frontal and temporal cortex, basal ganglia and brain stem were taken post-mortem from 20 patients with AIDS (including three with HIV-dementia, and eight with cognitive disorders that did not fulfil the criteria for HIV-dementia), 10 HIV-positive asymptomatic cases and 10 seronegative controls. Neuronal apoptosis was demonstrated by in situ end labelling in 18 AIDS cases and two pre-AIDS cases; a single apoptotic neuron was present in the temporal cortex of a control. Semiquantitative evaluation showed that the severity of neuronal apoptosis in the cerebral cortex correlated with the presence of cerebral atrophy, but not with a history of HIV dementia. There was no global quantitative correlation between neuronal apoptosis and HIV encephalitis or microglial activation. However, there was some topographical correlation between these changes. In the basal ganglia, apoptotic neurons were much more abundant in the vicinity of multinucleated giant cells and/or p24 expressing cells. Microglial activation was constantly present in these areas. Axonal damage was identified using beta-amyloid-precursor protein (betaAPP) immunostaining in 17 AIDS and eight pre-AIDS brains. Although no global quantitative correlation could be established between axonal damage and neuronal apoptosis there was an obvious topographic correlation supporting the view that axonal damage, either secondary to local microglial activation or due to the intervention of systemic factors, may also contribute to neuronal apoptosis.

[Dementia and human inmmunodeficiency virus infection]

HIV-associated neurological manifestations: dementia, myelopathy, and neuropathy, have become one of the commonest causes of neurological disorders in young people. Cognitive impairment develops in about 30 p. 100 of patients with AIDS and frank dementia in 15 to 20 p. 100 with an annual incidence after AIDS of approximatively 7 p. 100. Typically, the onset of dementia is relatively abrupt over a few weeks or months. The clinical manifestations of the encephalopathy now termed "HIV-dementia", suggest predominant subcortical or frontal involvement. Typical presentation includes apathy and inertia, memory loss and cognitive slowing, minor depressive symptoms and withdrawal from usual activities. Neurological examination may show hypertonia of lower limbs, tremor, clonus, frontal release signs and hyperactive reflexes. Terminally, the patient is bedbound, incontinent, abulic or mute with decorticate posturing leading to death over 3 to 6 months. However, a stabilisation and even a regression of the cognitive disorders have been observed following antiretroviral treatment. Radiological features of HIV dementia include both central and cortical atrophy and white matter rarefaction. However they are neither invariable nor specific. Together with CSF examination, they are more important to exclude opportunistic infections. Indeed, although a completely normal CSF profile may reasonably exclude the diagnosis; at present, no single test or combination of tests can reliably diagnose HIV dementia. Although the clinical characteristics of HIV-dementia are now clearly established, its pathogenesis is unclear and its pathological counterpart remains a matter of debate. A number of "HIV-induced" lesions may be found in the brain of AIDS patients and their causative role in HIV-dementia has been considered. They include HIV encephalitis due to productive CNS infection by the virus, diffuse white matter pallor "HIV-leukoencephalopathy" reflecting an abnormality of the blood brain barrier, involvement of the grey matter, "diffuse poliodystrophy", with neuronal loss that results, at least partly, from a process of programmed cell death and axonal damage. These changes are variably associated in patients with HIV dementia, however none of them can be closely related to the cognitive disorders. This suggests that the neuronal dysfunction underlying HIV-dementia results from different mechanisms that are variably associated and may interact mutually. These include production of viral proteins, microglial activation with consequent production of neurotoxic factors such as proinflammatory cytokines, free radicals, derivates of arachidonic acid, or quinoleic acid, and blood borne neurotoxic factors in particular cytokines.

DNA breaks detected by in situ end-labelling in dorsal root ganglia of patients with AIDS

Distal sensory axonal polyneuropathy (DSP) is the most frequent HIV-associated peripheral neuropathy. DSPs tend to occur in full-blown AIDS and worsen as CD4 cell counts decrease in blood. To assess a possible role for apoptosis in the pathogenesis of the neuropathy, we used in situ end-labelling (ISEL) detecting DNA strand breaks in DRG neurons of 19 HIV-infected patients, of whom nine had axonal polyneuropathy, and 11 controls. Sensory neurons with ISEL-assessed DNA breaks were observed in 9/19 patients with AIDS, 0/3 patients with pre-AIDS, and 1/11 controls. The prevalence of DNA breaks in neurons was higher in AIDS patients than in controls (P < 0.05). Among AIDS patients, DNA breaks in neurons were more abundant in patients with peripheral neuropathy (P < 0.04). It is possible that DNA breaks of DRG neurons induce the axonopathy and consequently play a role in the pathogenesis of DSP. It cannot be excluded, however, that DNA breaks could represent the result rather than the cause of axonopathy. We suggest that ISEL may detect neurons that were primed to apoptosis before death in relation with the HIV infection, and undergo DNA fragmentation at time of death, rather than neurons that underwent premortem both priming and triggering steps of the apoptotic process. This hypothesis could explain why most ISEL-positive neurons lack typical apoptotic morphology and why normal controls do not show ISEL positive cells.

Acute, relapsing brain oedema with diffuse blood-brain barrier alteration and axonal damage in the acquired immunodeficiency syndrome

A 38-year-old homosexual male with AIDS suffered four neurological episodes including headaches, confusion, visual impairment, memory disturbances, and dysarthria which resolved spontaneously in a few days. He was admitted to hospital during a fifth episode. Neurological examination revealed a cerebellar syndrome. General examination was normal. CD4 count was 90. CSF contained two WBCs/mm(3) and 12.30 mg/dL protein. MRI revealed diffuse ill defined increased signal on T2-weighted images in the white matter. His condition worsened rapidly with vomiting and he died 1 month after admission. Neuropathological examination revealed diffuse brain oedema with ventricular compression, central diencephalic herniation and bilateral tonsilar herniation in the absence of a focal lesion. Microscopical examination revealed predominant involvement of the white matter with diffuse myelin pallor and massive perivascular dilatation containing an exudate expressing serum proteins and occasional macrophages. The same exudate was also diffuse in the leptomeninges. Parenchymal damage predominated around the perivascular spaces and included loosening of tissue, axonal damage with spheroids and reactive astrocytosis. There was no evidence of productive HIV encephalitis, no multinucleated giant cells; p24 immunostaining and RT-PCR for HIV genome were negative. There was neither significant inflammation nor microglial activation. In this illustrative case, the relapsing course of the neurological signs, the diffuse topography of the blood-brain barrier breakdown and the absence of local cause make it likely that the diffuse leak and axonal damage could be related to circulating factors.

HIV-associated brain pathology: a comparative international study

Little is known about the frequency and variation of HIV-associated brain pathology in different geographical centres. To assess whether there is an association between the frequency of disease and demographic factors we examined the neuropathological findings in four European and two American cities. The cities included London, Edinburgh, Paris, Budapest, Baltimore and Newark. Information was collected on a total of 1144 cases. HIV encephalitis was the most common observation in all the centres. although its frequency varied between them (P < 0.01). Furthermore, there were significant differences (P < 0.001) between the various categories of exposure and the frequency of HIV encephalitis in Edinburgh and other centres. The occurrence of toxoplasmosis, progressive multifocal leukoencephalolpathy (PML) and cryptococcal infection also differed between the various centres (P < 0.01). None of the findings was attributable to age, sex, or ethnic origin, but the introduction of anti-retroviral treatment, such as Zidovudine, may have been important. Overall, this study highlights geographical variability and the potential importance for group of exposure and anti-retroviral medication as factors affecting the development of various HIV-associated brain lesions.

Prion encephalopathy with insertion of octapeptide repeats: the number of repeats determines the type of cerebellar deposits

We studied modifications of the molecular layer of the cerebellum in three patients with octapeptide repeat insertion (OPRI). Two brothers carrying a six-OPRI showed only spongiosis in haematoxylin & eosin preparations (H&E), whereas immunocytochemical examination (ICC) with an antiprion protein (PrP) antibody revealed numerous elongated PrP deposits. The third patient from a family with an eight-OPRI had numerous plaques visible in H&E preparations and had been diagnosed as Gerstmann-Straüssler-Scheinker syndrome. So far, 15 other cases from seven families and three individual cases with OPRI have undergone neuropathological examination. Characteristic PrP deposits were seen in six other cases, two isolated cases with a four- and a seven-OPRI, whereas four cases with a six-OPRI came from three different families. Such deposits have never been reported in other cases of prion encephalopathy, without OPRI. Genuine plaques were observed in five out of the 15 other patients. Interestingly, four had an eight-OPRI and one a nine-OPRI. Cases with OPRI are prone to develop different PrP deposits: those only visible on ICC are not to be confused with genuine plaques visible in H&E preparations. Elongated PrP deposits are present in cases with a four- to seven-OPRI, whereas plaques are present when there is an eight- or a nine-OPRI. All these cases should be termed prion encephalopathy with OPRI.

Localization of HIV-1 co-receptors CCR5 and CXCR4 in the brain of children with AIDS

The chemokine receptors CCR5 and CXCR4 are co-receptors together with CD4 for human immunodeficiency virus (HIV)-1 entry into target cells. Macrophage-tropic HIV-1 viruses use CCR5 as a co-receptor, whereas T-cell-line tropic viruses use CXCR4. HIV-1 infects the brain and causes a progressive encephalopathy in 20 to 30% of infected children and adults. Most of the HIV-1-infected cells in the brain are macrophages and microglia. We examined expression of CCR5 and CXCR4 in brain tissue from 20 pediatric acquired immune deficiency syndrome (AIDS) patients in relation to neuropathological consequences of HIV-1 infection. The overall frequency of CCR5-positive perivascular mononuclear cells and macrophages was increased in the brains of children with severe HIV-1 encephalitis (HIVE) compared with children with mild HIVE or non-AIDS controls, whereas the frequency of CXCR4-positive perivascular cells did not correlate with disease severity. CCR5- and CXCR4-positive macrophages and microglia were detected in inflammatory lesions in the brain of children with severe HIVE. In addition, CXCR4 was detected in a subpopulation of neurons in autopsy brain tissue and primary human brain cultures. Similar findings were demonstrated in the brain of adult AIDS patients and controls. These findings suggest that CCR5-positive mononuclear cells, macrophages, and microglia contribute to disease progression in the central nervous system of children and adults with AIDS by serving as targets for virus replication.

Human immunodeficiency virus type 1 and its coat protein gp120 induce apoptosis and activate JNK and ERK mitogen-activated protein kinases in human neurons

Detection of apoptotic neurons and microglial cells in the brains of human immunodeficiency virus type 1 (HIV-1)-infected patients has suggested that programmed cell death may be implicated in the physiopathology of HIV-1 encephalopathy. To analyze in vitro the intracellular signals induced by HIV-1 in human neurons and the associated neuronal death, we tested cultured human central nervous system (CNS) cells for apoptosis induced by HIV-1 and gp120 and for signaling pathways activated by gp120. HIV-1 and gp120 induced apoptosis of neurons and microglial cells but not of astrocytes or transformed microglial cells. Gp120 activated c-Jun N-terminal kinase (JNK) and p42 extracellular-regulated kinase (ERK) in primary CNS cells, with an early peak of activation at 2 to 5 minutes that was not present when pure microglial or astrocyte cultures were tested, followed by a late and sustained activation (10 and 60 minutes) in primary and enriched glial cell cultures as well as in transformed microglial cells. This demonstrates that gp120 could be an effector of HIV-1-induced apoptosis in the CNS and act directly on neuronal and glial cells.

[Lesions of the central nervous system in the early stages of human immunodeficiency virus infection]

Early HIV-1 invasion of the central nervous system has been demonstrated by many cerebrospinal fluid studies; however, most HIV-1 carriers remains neurologically unimpaired during the so called "asymptomatic" period lasting from seroconversion to symptomatic AIDS. Therefore, there are very few neuropathological studies in the early pre-AIDS stages 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 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.

Giant cell arteritis in association with cerebral amyloid angiopathy: immunohistochemical and molecular studies

Giant cell arteritis (GCA) usually manifests as a transmural vascular infiltrate of mononuclear and multinucleated giant cells (MNGC). We describe six patients with GCA associated with severe cerebral amyloid angiopathy (CAA), all with cerebral hemorrhage or varying degrees of cerebral infarct, and histological evidence of Alzheimer's disease (cortical CAA often predominating over senile plaques and neurofibrillary tangles). One case showed mostly cortical involvement (with old microhemorrhages), and the others were primarily leptomeningeal (with involvement of the underlying cortex and extensive encephalomalacia of adjacent brain). Many vessels with CAA exhibited a pronounced adventitial and perivascular infiltrate of lymphocytes, histiocytes, and MNGC. Immunohistochemical staining showed deposition of beta/A4 peptide primarily in the thickened media of CAA vessels, and within the cytoplasm of MNGC--suggesting phagocytosis of insoluble peptide. Cystatin C antibody stained vascular amyloid and diffusely highlighted astrocytic and MNGC cytoplasm. HAM56-positive macrophages were frequently seen around amyloid-laden vessels. Anti-smooth muscle actin immunohistochemistry suggests the occurrence of medial destruction by amyloid, with relative preservation of intimal cells. Ultrastructural studies performed in one case confirmed the presence of intracytoplasmic amyloid in MNGC. The GCA seen in these cases of CAA most likely represents a foreign body response to amyloid proteins, causing secondary destruction of the vessel wall. DNA from brain tissues of five affected patients was examined to assess whether mutations were present in exon 17 of the APP gene or exon 2 of the cystatin C gene, a finding that might explain the foreign body giant cell response to amyloid proteins in these cases. However, restriction fragment mapping of amplified gene segments showed that previously described mutations were not present in these cases.

Axonal damage revealed by accumulation of beta-APP in HIV-positive individuals without AIDS

The presence of neuropsychological disturbances in HIV-positive, pre-symptomatic individuals is a controversial issue. Neuroimaging studies have not shown brain atrophy or hyperintensity in the white matter, whereas proton magnetic resonance spectroscopy has revealed some abnormality of cerebral biochemistry. Using an antibody to beta-amyloid precursor protein (beta-APP), we previously demonstrated frequent and widespread axonal changes in the brains of AIDS patients. In this study, we extended the use of beta-APP to asymptomatic patients in order to establish a possible morphological correlation with neuropsychological disorders. Brain samples from 29 patients were examined. Results showed bundles of beta-APP-positive axons in 8/29 cases (27%). The changes, seen in both superficial and deep white matter, were either focal or diffuse, could not be visualized by silver or ubiquitin stains, and did not coexist with any change in distribution or morphology of astrocytes and microglial cells. We conclude that in HIV-positive asymptomatic individuals, axonal changes: (a) may be related to the state of immune activation with consequent presence of toxic substances, including cytokines, observed in these patients; (b) may represent mild changes that could undergo repair, unless other pathological events, such as the supervening of the AIDS stage and the specific encephalitis, make them permanent.

Pathology of the central nervous system in Chester-Erdheim disease: report of three cases

Chester-Erdheim disease is a rare form of non-Langerhans cell histiocytosis consisting of disseminated xanthogranulomatous infiltration and fibrosis that primarily involves the bones, visceral organs and systemic fatty spaces. Involvement of the central nervous system is variable, and neuropathological features have seldom been documented. We report the neuropathological findings in 3 autopsy cases. One patient had radiological and pathological bone changes characteristic of Chester-Erdheim disease. Neuropathology revealed multiple characteristic xanthogranulomas disseminated in the cerebral hemispheres, hypothalamus, cerebellum, and brainstem. The second patient presented first with cutaneous lesions characteristic of Langerhans cell histiocytosis. She subsequently developed bone abnormalities suggestive of Chester-Erdheim disease, which was confirmed by autopsy, raising the possibility of a common spectrum of histiocytosis including both diseases. Gross examination of the brain was normal, however, microscopy showed infiltration of the brain by characteristic non-Langerhans cell xanthogranulomas. The third patient presented with systemic features characteristic of Chester-Erdheim disease. Neurological signs included gait disturbance, seizures and confusion. Examination of the brain did not show any histiocytic infiltration, but did show changes suggestive of Hallervorden-Spatz syndrome. Association of Chester-Erdheim disease and Hallervorden-Spatz syndrome has not been previously reported. The relationship between both conditions is unclear.

[Central nervous system lesions in the early stages of HIV infection]

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, very few neuropathological studies have been conducted in the early pre-AIDS stages, 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 be involved. 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 inhibit viral replication at this stage.

[Central nervous system infection due to Herpes simplex virus in AIDS]

Infections of the central nervous system by Herpes simplex viruses (Herpes simplex type 1 and Herpes simplex type 2) are uncommon in acquired immune deficiency syndrome and are often clinically and pathologically atypical. We have collected 11 cases of herpes simplex encephalomyelitis in AIDS patients reported in the literature. Only 3 of these cases presented with a typical, necrotizing, limbic encephalitis. Other clinicopathological patterns included ventriculitis, rhombencephalitis and myelitis. Ventriculitis and rhombencephalitis were usually due to infection by HSV-1, whereas myelitis was mostly due to HSV-2 infection. Distinction between the 2 types of virus is often difficult by immunohistochemistry due to frequent cross reactivity and usually requires tissue culture, in situ hybridization, or polymerase chain reaction. Association of HSV encephalomyelitis with productive infection of the central nervous system by the human immunodeficiency virus was only found in one case. In contrast, co-infection with cytomegalovirus was found in 9 of the 11 cases. One case also had had varicella zoster virus vasculitis, and another case also had a cerebral malignant non Hodgkin's lymphoma in which Epstein Barr virus genome was identified. This supports the view that concomitant herpes-virus infections of the central nervous system is a characteristic feature of AIDS.

[Progressive multifocal leukoencephalopathy: virological and neuropathological aspects]

Progressive multifocal leukoencephalopathy is a subacute demyelinating disease of the central nervous system due to an opportunistic infection by a polyomavirus, most often JC virus, which predominantly infects oligodendrocytes. Progressive multifocal leukoencephalopathy used to be a rare condition, usually complicating lymphoproliferative diseases. Since the onset of the AIDS epidemic, its incidence has considerably increased and HIV infection has become, by far, the main risk factor for the disease. In AIDS patients, progressive leukoencephalopathy frequently shows atypical clinical and pathological features. The development of malignant glial tumors, within demyelinating regions, in patients with progressive multifocal leukoencephalopathy, has been reported in exceptional cases. The course of progressive multifocal leukoencephalopathy is invariably fatal. The diagnosis can only be made with certainty by histopathological examination of the brain, on cerebral biopsy or at postmortem. However, neuroradiological features may be extremely suggestive in many cases and PCR seems to be a reliable technique for demonstrating viral genome in the CSF. A few antiviral treatments have been proposed, however their efficacy is difficult to assess due to the low prevalence of the disease and the occurrence of rare cases with spontaneously prolonged survival.

[Neuronal apoptosis in the central and peripheral nervous system in HIV infection]

Apart from the unique changes characteristic of "HIV encephalitis", the productive infection of central nervous system by HIV, which predominantly involves the white matter and basal ganglia, evidence is accumulating that the cerebral cortex may also be affected in AIDS patients. Neuronal loss, suspected at microscopic examination, has been demonstrated by a number of morphometric studies. However, the cause and mechanism of neuronal damage in HIV infection, are still unclear. In an attempt to look for an apoptotic process at the origin of neuronal loss in AIDS, we examined samples of frontal cortex, temporal cortex and basal ganglia from 12 patients who died from AIDS and 4 asymptomatic HIV-positive cases using in situ end labelling to demonstrate characteristic DNA fragmentation. These were compared with 5 asymptomatic seronegative controls, and 2 seronegative patients with Alzheimer's disease. We demonstrated neuronal apoptosis in all AIDS cases and in the Alzheimer's cases. Positive in situ end labelling was usually associated with morphological changes suggestive of neuronal apoptosis. Semiquantitative assessment of the density of apoptotic neurons showed that neuronal apoptosis was more severe in atrophic brains. In contrast, no correlation was found between the density of apoptotic neurons and the presence of HIV-encephalitis or a history of cognitive disorder. Only occasional apoptotic neurons were found in one asymptomatic, HIV-positive case. Apoptosis was never observed in asymptomatic seronegative cases. We also looked for apoptotic neurons in spinal ganglia of 20 AIDS cases, 5 of whom had a terminal sensory distal neuropathy, and 10 seronegative controls devoid of neuropathy. Apoptotic neurons were found in 6 of the AIDS patients and in none of the seronegative controls. However, no correlation was found between the severity of neuronal apoptosis in the spinal root ganglia and the presence of absence of a terminal distal sensory neuropathy. Experimental studies tend to support our in vivo findings. HIV-infection of primary cultures of human embryonic central nervous system induced frequent apoptosis of neurons. No apoptotic cell was identified in non infected control cultures.

[Central nervous system infection due to varicella and zoster virus in AIDS]

We have reviewed 23 cases of varicella-zoster virus infection of the central nervous system in patients with the acquired immunodeficiency syndrome, previously reported in the literature, including 11 from our own series. This allowed us to identify 5 clinico-pathological patterns which could occur simultaneously. In most cases, viral proteins or viral genome were identified using immunocytochemistry or in situ hybridization. Multifocal encephalitis involves predominantly the white matter and is likely to be due to haematogenous spread of the infection. Ventriculitis may have variable appearance according to the course of the disease. In one incipient case, the ependymal lining appeared irregular with foci of infected ependymal cells some of which protruded into the ventricular lumen; in other instances, there was acute or chronic necrosis of the ventricular wall with marked vasculitis. Acute haemorrhagic meningo-myelo-radiculitis with necrotising vasculitis may be associated with ventriculitis and results from shedding of infected ependymal cells into the ventricular lumen and secondary seeding of the cerebrospinal fluid. Focal necrotising encephalitis or myelitis usually follows cutaneous herpes zoster in the corresponding dermatoma and is considered to result from neural spread from the diseased trigeminal or dorsal root ganglion. Vasculopathy involving leptomeningeal arteries and causing cerebral infarcts is associated with meningitis in most cases. These findings are in keeping with the observation in other immunocompromised patients, that varicella-zoster virus spread to the central nervous system may follow different routes. Our study tends to show that varicella-zoster virus infection of the central nervous system is more frequent in the acquired immunodeficiency syndrome than previously suspected and suggests this diagnosis must be considered systematically in cases of encephalitis, ventriculitis, focal myelitis, acute myeloradiculitis and cerebral infarcts in these patients, since an efficient treatment is available.

Diagnostic imaging contribution in the early stages of HIV infection of the brain

The neuropathology of full-blown, symptomatic AIDS, established in many large autopsy series, has been described in great detail and is now universally accepted. In contrast, the natural history of the changes occurring in the central nervous system during the earlier states of HIV-1 infection remains poorly understood. With specific regard to MR imaging, structural abnormalities have been reported early in the course of the illness, with variable incidence, making it difficult to appreciate the significance of these findings, in particular for neurologically asymptomatic individuals. This article analyzes successively neuropathologic studies at the early stages of brain involvement by HIV and shows how imaging techniques contribute to the understanding of what is going on during the so-called "asymptomatic" period, lasting from seroconversion to symptomatic AIDS. The complementary use of clinical imaging and new technical modalities, such as proton spectroscopy MR imaging or functional MR imaging, will provide more specific and sensitive analyses. Animal studies also will contribute in the future by providing a better knowledge of the natural history of the illness and providing a means for testing the efficacy of new medication.

Peripheral neuropathy in human immunodeficiency virus-infected patients with the diffuse infiltrative lymphocytosis syndrome

A subset of human immunodeficiency virus (HIV)-infected patients develop persistent CD8 hyperlymphocytosis and a Sjogren's syndrome-like syndrome associated with multivisceral CD8 T-cell infiltration, known as the diffuse infiltrative lymphocytosis syndrome (DILS). Patients with DILS tend to have higher CD4 cell counts, fewer opportunistic infections, and longer survival times than other HIV-infected patients. Peripheral nerve involvement in DILS has been poorly documented. We studied 12 HIV-infected patients with CD8 hyperlymphocytosis, DILS, and clinical signs of peripheral neuropathy. Two of 4 patients who were HLA typed were HLA-DR5 and 1 was HLA-DR6. All patients had the sicca syndrome and multivisceral involvement. The neuropathy was acute or subacute, always painful, and symmetrical in 8 cases. Electrophysiology was consistent with axonal neuropathy in 10 of 12 patients. Nerve biopsy showed marked angiocentric CD8 infiltrates without mural necrosis (12 of 12), and abundant expression of HIV p24 protein in macrophages (12 of 12). The HIV genome was detected by polymerase chain reaction in nerve homogenates. Zidovudine therapy was associated with improvement in 6 of 6 patients and steroid therapy was beneficial in 4 of 5 patients. No T-cell lymphoma was observed during follow-up, but 2 patients developed a primary B-cell lymphoma. We conclude that DILS neuropathy represents HIV-associated neuropathy, characterized by marked CD8 infiltration and abundant HIV in nerve, that improves with zidovudine or steroid therapy, and probably reflects a systemic host-determined and antigen-driven response to HIV.

JC virus detection in the cerebrospinal fluid of AIDS patients with progressive multifocal leucoencephalopathy and monitoring of the antiviral treatment by a PCR method

Twenty-four cerebrospinal fluid (CSF) samples from 19 AIDS patients with neurological signs were analysed by the polymerase chain reaction (PCR) for the presence of JC virus (JCV). Eleven of the 19 patients tested presented with progressive multifocal leucoencephalopathy (PML). Two specific JCV target sequences were used for the PCR analysis: a sequence specific for the T antigen genes from both BK virus (BKV) and JCV (PCR1) and a sequence specific for the large T antigen gene from JCV (PCR2). The JCV genome was detected in 10 of 11 patients with PML by the PCR1 method and in all 11 patients by the PCR2 method. With samples from the eight patients without PML, one positive result was obtained with the PCR1 method and this sample and another gave positive results with PCR2. Multiple CSF samples were collected from three patients with PML at different times, including after intrathecal cytarabine treatment, and were tested by the PCR2 method for the presence of the JCV genome. The PCR result became negative for two of the three patients during the cytarabine treatment. However, the absence of a PCR signal was not associated with clinical improvement in these patients. The PCR method is useful for the detection of JCV in CSF samples and in the diagnosis of PML. However, the application of PCR for monitoring the effect of treatment remains to be established.

[Central nervous system mycoses in AIDS with the exception of cryptococcosis. Apropos of 3 anatomo-clinical cases]

Fungal infections of the central nervous system are uncommon in human immunodeficiency virus infected patients. The most frequently encountered is cerebromeningeal cryptococcosis. We report 3 clinicopathological cases of rarer fungal infections of the central nervous system in AIDS patients due to Candida and Aspergillus genders. In most cases, a systemic candida infection or aspergillus pulmonary infection preceded the onset of cerebral granulomas or abscesses. These infections usually occurred at the terminal stage of the disease and were associated with other neuropathologies. Neutropenia associated with lymphopenia represents a frequent risk factor along with intravenous catheter.

[Contribution of animal models in the understanding of AIDS encephalopathy]

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.

[Sequences of human herpes virus type 8 and Epstein-Barr virus in AIDS-related primary central nervous system non-Hodgkin's lymphoma]

Presence of human herpes virus type 8 (HHV8), detected by nested PCR, and expression of Epstein-Barr virus (EBV), as assessed by immunochemistry and in situ hybridization, were evaluated in 20 primary non-Hodgkin immunoblastic lymphomas (NHL) of the central nervous system (CNS) from patients who died from AIDS, and in 10 samples of cerebral tissues from patients who died from AIDS, without cerebral lymphoma or Kaposi's sarcoma, as controls. Six lymphomas (30%) contained HHV8 sequences, and 19 (95%) expressed EBV; detection of HHV8 was more frequent in patients with Kaposi's sarcoma, than in other subjects (4/6 versus 2/14). Three (30%) controls contained HHV8 sequences, whereas none expressed EBV. AIDS-related CNS NHL is therefore clearly associated with EBV expression, while the presence of HHV8 appears occasional, probably associated with a low tissue viral load. The high frequency of HHV8 in AIDS-related primary CNS NHL patients with Kaposi's sarcoma suggests that this virus could play a role in the pathogenesis of some cerebral lymphomas.

Virus load and neuropathology in the FIV model

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.

[Neuronal apoptosis in the course of human immunodeficiency virus infection]

Apart from the unique changes characteristic of "HIV encephalitis", the productive infection of central nervous system by HIV, which involves predominantly the white matter and basal ganglia, evidence is accumulating that the cerebral cortex may also be affected in AIDS patients. Neuronal loss, suspected at microscopical examination, has been demonstrated by a number of morphometric studies. However, the cause and mechanism of neuronal damage in HIV infection, are still unclear. In an attempt to look for an apoptotic process at the origin of neuronal loss in AIDS, we examined samples of frontal cortex, temporal cortex and basal ganglia from 12 patients who died from AIDS and 4 HIV-positive asymptomatic cases using in situ end labelling to demonstrate characteristic DNA fragmentation. These were compared with 5 seronegative asymptomatic controls, and 2 seronegative patients with Alzheimer's disease. We demonstrated neuronal apoptosis in all the AIDS cases and in the Alzheimer's cases. Positive in situ end labelling was usually associated with morphological changes suggestive of neuronal apoptosis. Semiquantitative appreciation of the density of apoptotic neurons showed that neuronal apoptosis was more severe in atrophic brains. In contrast, no correlation was found between the density of apoptotic neurons and the presence of HIV encephalitis or a history of cognitive disorder. Only occasional apoptotic neurons were found in one asymptomatic, HIV-positive case. Apoptosis was never observed in asymptomatic seronegative cases. Experimental studies tend to support our in vivo findings. Infection by HIV of primary cultures of human embryonic central nervous system induced frequent apoptosis of neurons. No apoptotic cell was identified in non infected control cultures.

Rabies encephalitis in a patient with AIDS: a clinicopathological study

A 46-year-old man was bitten by a dog in Mali; anti-rabies vaccination was incomplete. Three months later he was admitted to hospital with fever and diarrhea. Human immunodeficiency virus (HIV) serology was positive and CD4 count was 70/mm3. His status worsened rapidly with confusion hydrophobia and hypersialorrhea. Despite anti-rabies serotherapy and vaccination, he died suddenly 12 days after admission. Immunofluorescence on cerebral tissue samples established rabies encephalitis. Neuropathology showed mild encephalitis with occasional Babès nodules and rare perivascular mononuclear cuffs. Intraneuronal Negri inclusion bodies were remarkably diffuse and abundant. They were clearly demonstrated by immunocytochemistry and electron microscopy. Apoptotic neurons were identified in the brain stem and hippocampus in the vicinity of inflammatory foci. In contrast, apoptosis could not be demonstrated in non-inflammatory areas, even where Negri bodies were numerous. There was no associated HIV encephalitis or opportunistic infection. The occurrence of rabies encephalitis in AIDS represents a random association, but is probably not exceptional as rabies is endemic in many countries and the AIDS epidemic is spreading worldwide. In this case, although the incubation duration and clinical presentation were comparable to those in classical rabies the T-cell-mediated immunosuppression may account for the weak inflammatory reaction and unusually abundant viral multiplication. This observation confirms that all those at risk for rabies, particularly immunocompromised patients, should receive complete anti-rabies treatment including vaccines and specific immunoglobulins, as soon as possible after infection.

Herpes simplex virus type 1 encephalitis in acquired immunodeficiency syndrome

Herpes simplex (HSV) infection of the central nervous system is uncommon in AIDS and usually has an atypical topography. This review is centred around the case of a 49-year-old homosexual patient with AIDS who died from diffuse encephalopathy. Neuropathological examination revealed necrotic and haemorrhagic changes involving both temporal lobes, insulae and cingulate gyri. Cowdry type A intranuclear inclusion bodies were abundant but inflammation was minimal. Electron microscopy confirmed characteristic herpes virus particles. Immunocyto-chemistry was positive for HSV type 1 and 2. In situ hybridization and PCR, however, were positive for HSV type 1 but excluded HSV type 2. There was associated cytomegalovirus ventriculitis but clearly separated from HSV encephalitis. There were no histological features of HIV encephalitis and HIV could not be demonstrated by immunocytochemistry or by PCR to demonstrate proviral DNA. Apoptotic neurons were numerous in areas with a severe macrophage reaction. Only two pathological cases with characteristic limbic distribution and necrotic haemorrhagic histologic have been reported previously. The rarity of these reports suggests that in advanced AIDS, the immune reaction causing a typical necrotizing encephalitis cannot be mounted. Distinction between HSV type 1 and 2 infection may be difficult by immunocytochemistry and usually requires in situ hybridization, tissue culture or PCR. In AIDS patients, HSV-1 has been identified as responsible for encephalitis whereas HSV-2 has been more responsible for myelitis. Associated productive HIV infection of the CNS was found in none of the cases. In contrast, cytomegalovirus encephalitis was found in nine of 11 cases of AIDS-associated HSV encephalitis.

Analysis of ENV V3 sequences from HIV-1-infected brain indicates restrained virus expression throughout the disease

The isolation of human immunodeficiency virus type 1 (HIV-1) from the cerebrospinal fluid (CSF) of asymptomatic virus carriers suggests that the viral infection spreading to the brain occurs early during infection. The aim of the present study was to investigate whether HIV-1 infection of the brain parenchyma also occurs during the early phase of infection. We also wished to compare the degree of replication of the virus in the brain at different clinical stages associated with HIV-1 infection. With the use of polymerase chain reaction (PCR), the viral genomes present in seven of eight brain specimens obtained from two asymptomatic HIV-1 carriers and six AIDS patients were amplified. Thereafter, the number of viral copies present in each brain specimen was quantified, the third variable region (V3) of the gp 120 glycoprotein was sequenced and these results compared with the histopathological findings in the tissue. The HIV-1 DNA genome was amplified from seven of the eight brain tissues, including the specimens obtained from the two asymptomatic carriers. An increased number of viral copies in the brain was found in association with histopathological findings of HIV-1 encephalitis. The analysis of the V3 sequences, however, revealed the presence of a homogeneous virus population in the brain at every clinical stage of the disease. These results suggest that, although entry of the virus in the parenchyma may occur early during infection, HIV-1 replication in the brain is constrained until the terminal phase of AIDS encephalitis.

Investigation on the expression of major histocompatibility complex class II and cytokines and detection of HIV-1 DNA within brains of asymptomatic and symptomatic HIV-1-positive patients

Among the various mechanisms proposed to explain the pathogenesis of cerebral lesions in human immunodeficiency virus (HIV)-induced encephalitis, a cytokine-mediated action has found most favour. Indeed, elevated expression of cytokines such as interleukin (IL)-1 and tumor necrosis factor-alpha (TNF-alpha), thought to be neurotoxic, has been found in AIDS patients. As a previous study had demonstrated the presence of HIV proviral DNA in brain tissue of a number of HIV-positive non-AIDS patients, we undertook this present investigation using morphological, immunohistochemistry (IHC) and polymerase chain reaction (PCR) methods to detect the expression of major histocompatibility complex (MHC) class II molecules, the presence of HIV-1 proviral DNA and of the cytokines TNF-alpha, IL-1 alpha, IL-4 and IL-6 in brains of the same group of individuals. The study included brains of 36 asymptomatic HIV-1 positive patients and the results were compared with those of AIDS patients either affected by HIV encephalitis (n = 8) or exempt from any neuropathological changes (n = 10) as well as of normal controls (n = 5). Results show that: HIV proviral DNA could be detected by PCR in 17 out of the 36 brains from HIV-positive pre-AIDS cases; most (15 of 17) of PCR-positive brains showed minimal to severe expression of MHC class II antigen; and cytokines could be detected predominantly within white matter even at this early stage. The data demonstrated that the state of immune activation described in AIDS is already present at the pre-AIDS stage and suggest that the presence of cytokines may already trigger the cascade of events leading to brain damage.

HIV type 1 V3 sequences and the development of dementia during AIDS

The most frequent neurological complication of AIDS is a dementia-like syndrome. Power and collaborators (J Virol 1994; 68:4643-4649) have reported an association between the clinical signs of AIDS dementia and the amino acid composition of two positions (305 and 329) within the V3 region of HIV-1 strains amplified from brain tissue. Similarly, we analyzed position 305 in the V3 region of HIV-1 present in the brain or cerebrospinal fluid of 25 nondemented subjects at different clinical stages of HIV-1 infection. Our results are, however, at variance with the findings presented by Power and colleagues. Histidine, found to be common among sequences derived from demented patients, was also present in the majority (16 of 25) of nondemented patients analyzed by us. In the hands of Power and colleagues, sequences derived from nondemented patients contained proline at position 305. None of our patients had proline in this position. We also asked the question whether the presence of a specific amino acid at position 305 of the V3 loop is linked to an increased capacity of HIV-1 isolates to infect primary microglial cells, the major target cell for HIV-1 infection in the brain. Primary HIV-1 isolates derived from blood and cerebrospinal fluid of five patients, two asymptomatic and three AIDS patients, were used to infect microglia cell cultures. Infection was monitored by syncytium formation and by p24 antigen release in the culture supernatant. All but one of the paired blood/CSF isolates replicated in human brain cultures. Replication occurred independently from the amino acid present at position 305 of the V3 region of the viral envelope. Our results indicate that the majority of HIV-1 isolates, even derived during the asymptomatic stage, have the capacity to infect microglial cells. The relevance of viral envelope sequences in determining tropism for microglial cells and development of neurological symptoms remains an open question.

Programmed cell death in brains of HIV-1-positive AIDS and pre-AIDS patients

Neuropathological studies have revealed that the brains of HIV-1-infected AIDS patients show the typical encephalitis and, in addition, neuronal loss. More recently, this neuronal cell loss has been thought to take place via programmed cell death (apoptosis) which has been demonstrated by an in situ end labelling (ISEL) technique. In this study 54 brains of HIV-1-positive patients were investigated by the ISEL technique to investigate whether apoptosis is also present in the brains of patients at the asymptomatic stage. Of these, 10 patients suffered from HIV encephalitis (HIVE), 8 had AIDS without neuropathological disorders and 36 were HIV-1-positive pre-AIDS patients. Apoptotic cells were detected in 6 of the 10 HIVE, 1 of the 8 AIDS without central nervous system (CNS) disease and 4 of the 36 asymptomatic individuals. A difference seen between the AIDS and pre-AIDS cases was that, in the latter, apoptotic cells were found in the white matter in all 4 cases, while only 2 of these 4 showed apoptotic neurons. The presence of apoptotic cells in a number, albeit small, of brains of HIV-1-positive pre-AIDS individuals, combined with abnormalities described previously in the same group of patients gives further support to the opinion that brain damage already occurs during the early stages of HIV infection.