Shu F. An

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.

Cerebral CD8+ lymphocytosis in HIV-1 infected patients with immune restoration induced by HAART

In HIV infected persons, highly active antiretroviral therapy (HAART) has reduced both the morbidity and incidence of several disorders. Its effects on direct HIV-induced damage to the CNS remain controversial. In addition, HAART may provoke an “immune reconstitution inflammatory syndrome” (IRIS). Herein we report two patients who, despite HAART, developed a diffuse encephalopathy. Their clinical, radiological and neuropathological features are described. Immunohistochemical and PCR analyses were used to detect HIV and to exclude other viruses in brain tissue. The unusual inflammatory reaction in the brain tissue was defined by immunohistochemistry. Both patients had advanced HIV disease with low CD4 counts and high HIV “viral loads” before starting HAART. In both, HAART induced an increase in CD4 count and a marked reduction in HIV viral load, which was accompanied, in patient one, by worsening of pre-existing, and, in patient two, by development of, acute encephalopathy. At post-mortem examination, the brain of patient one showed HIV encephalitis. In addition, the brains of both patients revealed HIV–DNA by PCR, diffuse microglial hyperplasia and massive and diffuse perivascular and intraparenchymal infiltration by CD8+/CD4− lymphocytes. We suggest that the rapid immune reconstitution induced by HAART in these two patients led to a redistribution of lymphocytes into peripheral blood. This was followed by recruitment of CD8+ lymphocytes into the brain, which resulted in the diffuse infiltration described. The appearances in patient two further suggest that HIV brain infection, even without encephalitis, is sufficient to trigger this response.

Detection and localisation of HIV-1 DNA and RNA in fixed adult AIDS brain by polymerase chain reaction/in situ hybridisation technique

Abstract In the brain of patients with AIDS, HIV-1 is localised in a productive form in mononuclear cells. One issue that still needs clarification is whether HIV is localised in cells other than those of mononuclear lineage. Gene amplification by polymerase chain reaction/in situ hybridisation (PCR-IS) could shed light on it. In this study, formalin-fixed, paraffin-embedded brain tissue from ten adult AIDS sufferers was used. Five of them showed evidence of HIV encephalitis (HIVE), five did not show any abnormality. Nested PCR revealed HIV-1 DNA in all HIVE cases and in three of the group without HIVE. HIV-1 DNA and RNA were also detected in situ in seven cases (all seven were also HIV-1 DNA positive in tube). A higher signal was located in the white than in the grey matter. HIV-1 DNA was found in microglia, macrophages, perivascular cells, multinucleated gaint cells (MGC) and in CD68-negative cells. Some of them were identified as endothelial cells, astrocytes and oligodendrocytes. Reverse transcriptase-PCR-IS was positive in macrophages, MGC, endothelial and glial cells. These results confirm infection of endothelial cells and other glial cells and give clues about the route of entry of virus into the central nervous system and the pathogenesis of the disease. This study did not give any convincing evidence supporting an infection of neurons by HIV-1.

Axonal damage revealed by accumulation of β-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 β-amyIoid precursor protein (β-APP), we previously demonstrated frequent and widespread axonal changes in the brains of AIDS patients. In this study, we extended the use of β-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 β-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.

The neuropathology of paraneoplastic syndromes

The term “paraneoplastic neurological syndromes” encompasses a number of uncommon disorders associated with systemic malignancies. In order to be classified a paraneoplastic neurological syndrome, the malignancies must not invade, compress, or metastasize to the nervous system. They can either focally or diffusely involve the central and peripheral nervous system or the neuromuscular junction.

Neuronal loss in Onuf's nucleus in three patients with progressive supranuclear palsy

Disorders of micturition have been reported only sporadically in patients with progressive supranuclear palsy (PSP). We report the results of a clinicopathological study of 3 patients with a definite diagnosis of PSP at various stages of their illness with sphincter abnormalities. Electromyography of the sphincter muscles was performed in all 3 patients and was abnormal in 2. Morphological and morphometric evaluation of Onufs nucleus in the sacral spinal cord, which is involved in sphincter control, showed severe cell loss, presence of neurofibrillary tangles, neuropil threads, and glial inclusions. We conclude that bladder dysfunction and abnormal sphincter electromyographic results are due to pathological changes in Onufs nucleus, and we propose that sphincter abnormalities should be included in the list of possible symptoms of PSP. Ann Neurol 2000;48:97–101

Sporadic fatal insomnia: A case study

A 58‐year‐old man died after a 27‐month illness characterized by insomnia, confirmed by polysomnography. He was homozygous for methionine at codon 129 of the prion gene but had no mutation in the prion gene. Neuropathology showed thalamic and olivary atrophy and no spongiform changes. Paraffin‐embedded tissue blotting demonstrated abnormal prion protein in the brain. This is the first case of the sporadic form of fatal familial insomnia with demonstration of the disorder by polysomnography. Ann Neurol 2000;48:665–668

Detection of infectious agents in brain of patients with acute hemorrhagic leukoencephalitis

Acute hemorrhagic leukoencephalitis (AHL) is a rare and usually fatal disorder characterized clinically by an acute onset of neurologic abnormalities. It may occur in association with a viral illness or vaccination. Radiology and brain biopsy are essential for the diagnosis. The etiology of AHL is unclear. We postulated that viral/bacterial infection might be responsible, directly or through an immune-mediated mechanism, for this acute inflammatory myelinopathy. Fifteen cases of AHL were studied. Infectious agents, including varicella zoster virus (VZV), herpes simplex virus (HSV), human herpes virus-6 (HHV-6), cytomegalovirus, Epstein-Barr virus, and Mycoplasma, were investigated in brain specimens using the polymerase chain reaction (PCR), reverse transcriptase (RT)-PCR, and immunohistochemistry. Using PCR, HSV DNA was found in four cases, VZV DNA in two, and HHV-6 DNA in one. Among the control cases, two were HSV DNA positive. Further investigation to detect HSV RNA and antigens in HSV DNA-positive cases revealed that two cases with AHL were both HSV RNA and antigen positive. AHL is a hyperacute disease, which is considered the most acute form of acute disseminated encephalomyelitis (ADEM). Our findings suggests that a viral infection may be implicated in its pathogenesis, most likely through an indirect mechanism; however, as only a few cases of this rare disease were examined, statistical significance was not achieved. As a number of patients with disorders of the ADEM group may progress to develop multiple sclerosis (MS), we argue that an organism that has produced the former may remain in the brain tissue and be subsequently involved in the production of a self-sustained disorder such as MS.

Neurotrophin-3 administration alters neurotrophin, neurotrophin receptor and nestin mRNA expression in rat dorsal root ganglia following axotomy

In the months following transection of adult rat peripheral nerve some sensory neurons undergo apoptosis. Two weeks after sciatic nerve transection some neurons in the L4 and L5 dorsal root ganglia begin to show immunoreactivity for nestin, a filament protein expressed by neuronal precursors and immature neurons, which is stimulated by neurotrophin-3 (NT-3) administration. The aim of this study was to examine whether NT-3 administration could be compensating for decreased production of neurotrophins or their receptors after axotomy, and to determine the effect on nestin synthesis. The levels of mRNA in the ipsilateral and contralateral L4 and L5 dorsal root ganglia were analyzed using real-time polymerase chain reaction, 1 day, 1, 2 and 4 weeks after unilateral sciatic nerve transection and NT-3 or vehicle administration via s.c. micro-osmotic pumps. In situ hybridization was used to identify which cells and neurons expressed mRNAs of interest, and the expression of full-length trkC and p75NTR protein was investigated using immunohistochemistry. Systemic NT-3 treatment increased the expression of brain-derived neurotrophic factor, nestin, trkA, trkB and trkC mRNA in ipsilateral ganglia compared with vehicle-treated animals. Some satellite cells surrounding neurons expressed trkA and trkC mRNA and trkC immunoreactivity. NT-3 administration did not affect neurotrophin mRNA levels in the contralateral ganglia, but decreased the expression of trkA mRNA and increased the expression of trkB mRNA and p75NTR mRNA and protein. These data suggest that systemically administered NT-3 may counteract the decrease, or even increase, neurotrophin responsiveness in both ipsi- and contralateral ganglia after nerve injury.

Accumulation of Prion Protein in the Peripheral Nervous System in Human Prion Diseases

After the finding that anti-prion antibodies stain sensory and sympathetic ganglia in variant Creutzfeldt-Jakob disease (vCJD), it was suggested that this localization supported the oral route of entry. However, prion accumulation subsequently also appeared in the peripheral nervous system (PNS) in sporadic cases. This study aims at evaluating the extent of prion protein accumulation in the PNS in all clinicopathologic subgroups of the disorder, with the exception of the familial and sporadic forms of fatal insomnia. Patients included 2 vCJD cases, 2 Gerstmann-Sträussler-Scheinker (GSS), 2 iatrogenic (iCJD), and 16 sporadic CJD (sCJD) cases. Gasserian (17) and spinal (9), celiac (2) and thoracic sympathetic (one) ganglia, spinal cord and medulla of one vCJD, 2 GSS, one iCJD, and 5 sCJD cases were examined. Immunostained sensory ganglia were seen in both vCJD, both iCJD, one GSS, and 10 sCJD cases; the celiac ganglion was positive in one of two sCJD cases, and the spinal dorsal horn and the medullary sensory nuclei were positive in one patient with vCJD, one with iCJD, and 3 with sCJD. Western blot demonstrated presence of PrPSc in the gasserian ganglion of one patient with sCJD. Accumulation of prion in ganglia (including autonomic) of the PNS, shared by all subgroups of spongiform encephalopathy, and in the dorsal horns and medullary sensory nuclei, shows that the sensory route is involved in the trafficking of this protein.