Leucoencephalopathy with multinucleated giant cells containing human immune deficiency virus-like particles and multiple opportunistic cerebral infections in one patient with AIDS

Polymicrobial brain abscesses: A complex condition with diagnostic and therapeutic challenges

Brain abscesses (BA) are focal parenchymal infections that remain life-threatening conditions. Polymicrobial BAs (PBAs) are complex coinfections of bacteria or bacterial and nonbacterial pathogens such as fungi or parasites, with diagnostic and therapeutic challenges. In this article, we comprehensively review the prevalence, pathogenesis, clinical manifestations, and microbiological, histopathological, and radiological features of PBAs, as well as treatment and prognosis. While PBAs and monomicrobial BAs have some similarities such as nonspecific clinical presentations, PBAs are more complex in their pathogenesis, pathological, and imaging presentations. The diagnostic challenges of PBAs include nonspecific imaging features at early stages and difficulties in identification of some pathogens by routine techniques without the use of molecular analysis. Imaging of late-stage PBAs demonstrates increased heterogeneity within lesions, which corresponds to variable histopathological features depending on the dominant pathogen-induced changes in different areas. This heterogeneity is particularly marked in cases of coinfections with nonbacterial pathogens such as Toxoplasma gondii. Therapeutic challenges in the management of PBAs include initial medical therapy for possibly underrecognized coinfections prior to identification of multiple pathogens and subsequent broad-spectrum antimicrobial therapy to eradicate identified pathogens. PBAs deserve more awareness to facilitate prompt and appropriate treatment.

Toxoplasma encephalitis in a HIV patient: unusual involvement of the corpus callosum

In patients with acquired immuno-deficiency syndrome, the differential diagnosis between primary brain lymphoma and toxoplasma encephalitis is not radiologically always straightforward, especially in the presence of a solitary cerebral lesion. In this context, involvement of the corpus callosum is almost exclusively associated with primary brain lymphoma. We describe here an HIV-infected patient who presented with a single and large cerebral lesion affecting the corpus callosum, suggestive of primary brain lymphoma on MRI-scan but who nonetheless responded clinically and radiologically to an anti-toxoplasma drug trial confirming the diagnosis of toxoplasma encephalitis.

Progressive multifocal leukoencephalopathy (PML) in the acquired immunodeficiency syndrome (AIDS). A neuropathological autopsy study of 21 cases

In a neuropathological autopsy study of 21 cases of AIDS-associated PML no fundamental morphological differences to non-AIDS PML were found. PML in AIDS often showed very large foci as well as necrotizing lesions. Partial involvement of cerebral cortex and deep gray matter were common findings; infratentorial lesions could be observed in more than three quarters of cases. Perivascular mononuclear infiltrates within PML foci were frequent and obviously not associated with a more benign clinical course. Possible reasons for these peculiarities of PML in AIDS are discussed. In 7 cases evidence of concomitant HIV encephalopathy was found; this may be one relevant factor contributing to severity of PML in AIDS. PML has to be regarded as a common complication of HIV infection, which may show atypical morphological and neuroradiological features.

Pathogenesis of virus-induced demyelination

Demyelination is a component of several viral diseases of humans. The best known of these are subacute sclerosing panencephalitis (SSPE) and progressive multifocal leukoencephalopathy (PML). There are a number of naturally occurring virus infections of animals that involve demyelination and many of these serve as instructive models for human demyelinating diseases. In addition to the naturally occurring diseases, many viruses have been shown to be capable of producing demyelination in experimental situations. In discussing virus-associated demyelinating disease, the chapter reviews the architecture and functional organization of the CNS and considers what is known of the interaction of viruses with CNS cells. It also discusses the immunology of the CNS that differs in several important aspects from that of the rest of the body. Experimental models of viral-induced demyelination have also been considered. Viruses capable of producing demyelinating disease have no common taxonomic features; they include both DNA and RNA viruses, enveloped and nonenveloped viruses. The chapter attempts to summarize the important factors influencing viral demyelination, their common features, and possible mechanisms.

Macrophage association of polyomavirus in progressive multifocal leukoencephalopathy: an immunohistochemical and ultrastructural study. Case report

Progressive multifocal leukoencephalopathy (PML) in a patient following autologous bone marrow transplantation for a non-Hodgkin's centroblastic lymphoma was studied by immunohistochemistry and transmission electron microscopy. Our observations indicate that a large amount of polyomavirus, most probably JC virus, is taken up and segregated within vacuoles of macrophages by phagocytosis. A relevant role of macrophages in the pathogenesis of PML is emphasized.

Progressive multifocal leukoencephalopathy in patients with human immunodeficiency virus

Lesions of progressive multifocal leukoencephalopathy (PML) in patients infected with the human immunodeficiency virus (HIV) often have mononuclear cell infiltrates so intense that they obscure the nature of the lesion. This response may be especially prominent in stereotactic biopsies of contrast-enhancing areas. Of 10 consecutive PML lesions biopsied stereotactically, three were markedly, two were moderately, and five were mildly inflamed. There were few to no enlarged oligodendrocytic nuclei with inclusions in the markedly and moderately inflamed lesions. We investigated all biopsies with immunoperoxidase, DNA in situ hybridization, polymerase chain reaction, and Southern immunoblot methodologies for toxoplasmosis and the following viruses: JC, cytomegalovirus, herpes simplex viruses I and II, and human T-cell lymphotropic viruses I, II, and III. We confirmed the presence of JC virus in each lesion; polymerase chain reaction revealed HIV genome only in one. Inflammatory PML lesions in HIV+ patients do not reflect co-infection with toxoplasmosis or viruses commonly seen in these patients. The mononuclear cells are primarily T lymphocytes. Patients with severely inflamed PML lesions, whether HIV+ or not, often show stabilization of symptoms with or without antiviral treatment and have longer lengths of survival than patients with less inflamed lesions.

Relapsing and remitting human immunodeficiency virus-associated leukoencephalomyelopathy

We describe a 33-year-old homosexual man with a steroid-responsive, remitting and relapsing leukoencephalopathy associated with recent human immunodeficiency virus type 1 (HIV-1) seroconversion. Biopsy of a parieto-occipital lesion revealed demyelination and astrogliosis with focal necrosis. Detailed investigations demonstrated no pathogens in the brain other than HIV-1. This patient illustrates that a neurological disorder clinically indistinguishable from multiple sclerosis may be the presenting manifestation of HIV-1 infection and may occur in the absence of clinically significant immunosuppression.

Cerebral lymphoma and HIV encephalitis in a case of paediatric AIDS, with pre-existing multicystic encephalomalacia

A case of intracerebral malignant B cell lymphoma associated with encephalitis typical of Human Immunodeficiency Virus (HIV) infection is described in a 4 year old child, with post-transfusion Acquired Immune Deficiency Syndrome (AIDS) and severe pre-existing cystic encephalomalacia. This report further documents B cell lymphoma as the commonest cause of an intracerebral mass, and an important cause of death in paediatric AIDS. That more than one pathological process may be responsible for neurological symptoms in paediatric AIDS is also emphasised.

JC virus detection by in situ hybridization in brain tissue from elderly patients

Brains from 10 patients aged 68 to 96 years at time of death were studied for JC viral DNA and common papovaviral capsid protein. In situ hybridization of JC viral DNA was performed by affinity cytochemistry using a biotinylated fragment of JC viral DNA. Immunohistochemistry was performed on brain tissue by the avidin DH-biotinylated horseradish peroxidase technique using polyclonal antibody raised against the papovaviral capsid protein. Viral protein and DNA were detected in 4 of 10 patients. JC virus may be present in the brains of aged patients more frequently than previously suspected.

Spinal cord lesions in the acquired immune deficiency syndrome (AIDS)

Spinal cord involvement in AIDS is not uncommon. Different types of lesions corresponding to varying pathogenetic mechanisms have been reported. Vacuolar myelopathy is the most frequently found. The symptoms and pathological changes resemble those of subacute combined degeneration; however, cobalamine or folate levels have always been found normal. Its frequent association with the multi-nucleated giant cells characteristic of HIV encephalitis makes it likely that the virus plays a role in its pathogenesis. Cytomegalovirus may be responsible for acute myeloradiculitis involving the spinal roots of the cauda equina and inferior part of the spinal cord. In cases of Herpes simplex virus myelitis has been reported; they are usually associated with cytomegalovirus infection and are due to herpes simplex virus type II. Secondary spread from systemic lymphomas may involve the subarachnoid space of the cord and the spinal roots. Compression of the spinal cord by epidural lymphomatous masses has also been described. Spinal infarcts may be secondary to acute or chronic vasculitis or to less specific vascular processes such as disseminated intravascular coagulation.

The involvement of the cerebral cortex in human immunodeficiency virus encephalopathy: a morphological and immunohistochemical study

The encephalopathy resulting from direct infection of the brain by human immunodeficiency virus (HIV), which correlates clinically with the AIDS dementia complex, has been reported as being localized to the white matter where it induces myelin loss, gliosis and perivascular infiltration by mononuclear macrophages and multinucleated giant cells. Damage to the cortical grey matter in HIV encephalopathy was investigated in nine randomly selected HIV-positive cases with or without clinical or morphological evidence of encephalopathy and in five age-matched controls, using routine histology and immunohistochemical methods [glial fibrillary acidic protein (GFAP), microglia and HIV antibodies]. Increased numbers of GFAP-expressing astrocytes and Ricinus communis agglutinin 1-120-expressing microglial cells were found in all the HIV-positive cases (including asymptomatic) and their severity could be correlated with the severity of the encephalopathy in the white matter; the increase in number of cells expressing GFAP was diffuse and the intensity of the staining higher than that of microglial cells. The subpial region was the most severely involved. It is suggested that involvement of the cortical grey matter is more common in HIV infection than previously suspected and that clinical evidence of a dementing process in AIDS is not necessarily due only to white matter lesions.

Human immunodeficiency virus: infection of the nervous system

Cynics would say it has taken the scientific community a long time to achieve very little progress in our understanding of HIV-mediated CNS damage. We cannot yet say with surity how neuronal function is affected. However, when viewed through the perspective that retroviral diseases of the human nervous system are newly recognized diseases, significant progress has been made in the 3 years since HIV infection was noted within the CNS. We have a lot to learn about how retroviruses damage the CNS, but at least the questions are better defined.

Diffuse "encephalitic" cerebral toxoplasmosis in AIDS. Report of four cases

Four patients with AIDS presented with a rapidly fatal global neurological illness. CT did not show any focal lesion and gross post mortem examination of the brain was normal in three of the four cases. Microscopic examination revealed numerous widespread microglial nodules in the brain parenchyma, most containing central toxoplama cysts or free tachyzoites. Such diffuse, non-necrotic, "encephalitic" forms of cerebral toxoplasmosis appear unique to AIDS and, to our knowledge, have not been documented previously. They represent a treatable, often misdiagnosed cause of diffuse neurological involvement in AIDS patients.

Human immunodeficiency virus (HIV)-induced disease of the central nervous system: pathology and implications for pathogenesis

Significant contributions from many different groups during the last 2 or 3 years have characterized relatively uniform neuropathological changes of the CNS in AIDS patients. They feature human immunodeficiency virus (HIV)-induced multinucleated giant cells as a histopathological hallmark and HIV demonstrable by electron microscopy, immunocytochemistry, and in situ hybridization. Unfortunately, a varying and confusing terminology is used to designate these changes which have been reported in surprisingly different incidences. Focal lesions have a microgranulomatous appearance and were designated as multifocal giant cell encephalitis or subacute encephalitis, which may be confused with the nodular encephalitis caused by cytomegalovirus. For some authors, the latter designation also covers characteristic diffuse white matter changes which have been termed progressive diffuse leukoencephalopathy by others, and which may overlap with focal lesions. Pathological features of these HIV-induced syndromes and other data do not support a major cytopathic effect of HIV on neural cells; rather, they suggest secondary pathogenetic events involving the predominant cell type in the lesion, the monocyte/macrophage/microglia. However, low-level, latent, and persisting HIV infections of neural cells cannot be excluded at present; the CNS may then serve as an early infected virus reservoir. A detailed correlation of clinical symptoms and stage of the infection to neuropathological changes is currently lacking but urgently needed. The presence of the HIV-receptor (CD4) molecule on brain cells is controversial; similarly, a putative cross-reaction of HIV proteins with trophic substances and transmitters needs to be substantiated.

Pathology of the central nervous system in 40 cases of acquired immune deficiency syndrome (AIDS)

The central nervous system was examined in 40 AIDS patients who died between August 1982 and 1987. The cases included two children born to intravenous drug abusers and 38 male adults. The brains of eight patients who had no clinical or radiological evidence of central nervous system involvement showed non-specific changes which included microglial nodules, perivascular mononuclear cuffs, mineralization of blood vessels and granular ependymitis. In 32 brains from patients with neurological symptoms, toxoplasmosis was the most frequent finding (19 cases) manifested by multifocal, necrotic lesions or a diffuse pseudo-encephalitic process. Other opportunistic infections included cytomegalovirus (eight cases), progressive multifocal leucoencephalopathy (two cases), cryptococcosis (one case), aspergillosis (one case), multiple bacterial microabscesses (one case) and Mycobacterium avium intracellulare (one case). Two patients had cerebral lymphoma. Subacute encephalitis with white matter lesions and multinucleated giant cells characteristic of HIV infection was present in 15 cases. Various combinations of all these infections were encountered in the same brain, sometimes in the same area and, occasionally, in the same cell.

Human immunodeficiency virus (HIV) and JC virus in acquired immune deficiency syndrome (AIDS) patients with progressive multifocal leukoencephalopathy

Of the 93 acquired immune deficiency syndrome (AIDS) patients autopsied between 1983 and 1986, 27 had evidence of viral encephalitis of which 3 had progressive multifocal leukoencephalopathy (PML), confirmed by electron microscopy. Using in situ hybridization with biotinylated JC virus probes, paraffin sections from the brains of these 27 patients were examined. JC virus was found only in those patients with histologically proven PML, while no evidence of JC virus was detected in the brains of the other 24 AIDS patients despite the presence of white matter pathology. Brain biopsies of the PML patients demonstrated human immunodeficiency virus (HIV)-infected macrophages infiltrating regions of demyelination. When the patients died (2 to 6 months after diagnosis of PML), many more macrophages contained HIV antigens and some had fused to form multinucleated giant cells. These findings suggest that in AIDS patients, papovaviruses not only cause damage by directly infecting oligodendroglia but causes additional damage by eliciting the ingress of macrophages latently infected with HIV. As was seen with other infections (e.g., cytomegalovirus) of the CNS this might be a general mechanism of HIV entry into the brain.

Brain pathology induced by infection with the human immunodeficiency virus (HIV). A histological, immunocytochemical, and electron microscopical study of 100 autopsy cases

Neuropathological examination of brain tissue of 100 patients with infection by the human immunodeficiency virus (HIV), including 98 with clinically manifest acquired immune deficiency syndrome (AIDS), revealed distinct multifocal-disseminated and diffuse brain tissue lesions, which can be regarded as HIV-induced brain lesions: multifocal giant cell encephalitis (MGCE; 4) and progressive diffuse leukoencephalopathy (PDL; 25). These lesions were found in 38 brains, and in 17 in absence of infectious, necrotizing or inflammatory changes of other types. In 13 brains, a combination of MGCE with PDL was seen, suggesting a spectrum of HIV-induced brain lesions. MGCE is characterized by perivascular accumulations predominantly of rod cells, monohistiocytes and macrophages, all of which are strongly labeled with a monoclonal antibody to macrophages. Most conspicuous are multinucleated giant cells which are also labeled by anti-macrophage antibody, and which can be regarded as evidence of the local presence of HIV, as confirmed by electron microscopical detection of HIV particles in four MGCE brains, and by immunocytochemical detection of HIV proteins in two MGCE brains. PDL is characterized by a triad: diffuse myelin loss, astroglial proliferation, and infiltration by mono- and multinucleated macrophages. HIV-induced lesions can be morphologically differentiated from histopathological brain lesions known in immunosuppression, including what is called here nodular encephalitis ["subacute encephalitis" of the literature, in most cases attributable to cytomegalovirus (CMV) or toxoplasmosis], by their characteristic histopathology including the hallmark presence of multinucleated giant cells, by direct immunocytochemical and electron microscopical demonstration of HIV in the lesions, and by the absence of opportunistic agents (bacteria, fungi, Toxoplasma, CMV, HSV or papovaviruses). Diffuse poliodystrophy (diffuse proliferation of astroglia with swollen nuclei, occasionally minor neuronal loss and rod cell proliferation) was found in the cerebral cortex and other gray matter in half of all brains, including cases with gyral atrophy, and may be another correlate of HIV damage to the brain. Morphological delineation of HIV-induced brain lesions is a necessary prerequisite for a meaningful clinical definition of HIV-induced cerebral disease.