Isolation of HTLV-III from cerebrospinal fluid and neural tissues of patients with neurologic syndromes related to the acquired immunodeficiency syndrome

Neuropsychiatric aspects of HIV infection

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Feline immunodeficiency virus as a model for study of lentivirus infection of the central nervous system

Feline immunodeficiency virus infects the CNS and results in predictable pathophysiology strikingly similar to that seen with HIV-1 infection of humans. The observed pathophysiology is mimicked in several physiologically assessed modalities, further supporting the validity of the feline model. Peripheral and control evoked potential findings and the occurrence of the sleep architecture changes in both cat and human disease provide an intriguing focus for further investigation. Although structurally diverse in an absolute sense, FIV and HIV-1 share basic structural features and commonalities of their life cycle. It is likely that by understanding the common mechanisms by which these lentiviruses influence CNS function, a more complete understanding of the neurological deficits seen in HIV-1 infected patients will be obtained. The cat model is particularly valuable for study of CNS disease, since it allows detailed analyses of events during the acute phase of infection, under circumstances in which the nature and timing of the infection are carefully controlled. The availability of molecular clones for mutational analysis will facilitate mapping of genomic regions critical to the perturbation of CNS function. It is suggested that development of intervention strategies in the cat model will yield treatment modalities directly applicable to HIV-1 infection of humans.

Anticardiolipin antibodies in HIV infection: association with cerebral perfusion defects as detected by 99mTc-HMPAO SPECT

Anticardiolipin antibodies (ACA) belong to a heterogeneous group of antibodies directed against negatively charged phospholipids. In patients with rheumatic disorders, their presence has been correlated to the occurrence of thromboembolic complications, thrombocytopenia, abortions and other disease manifestations. Several studies have revealed the detection of mostly high-titre ACA in a significant proportion of HIV-infected patients without any known clinical relationship. In our study, ACA were detected in 17/34 HIV-infected patients, and their presence was significantly associated with the detection of cerebral perfusion abnormalities by 99mTc-HMPAO SPECT. SPECT scans were classified as normal or as focal or diffuse defects in uptake. Most patients (13/16) with cerebral perfusion defects had elevated ACA titres in contrast to 4/18 patients with normal SPECT findings (P = 0.002). Focal uptake defects were always associated with the presence of ACA. No correlation to clinical features or other laboratory parameters was evident. Our results suggest a possible implication of autoimmune mechanisms in the pathogenesis of cerebral perfusion abnormalities detected by SPECT scanning in HIV-infected patients. However, further studies are needed to evaluate the clinical significance and to develop possible therapeutic consequences.

Depression in patients with HIV and AIDS

In this paper we review studies of depression in patients with HIV/AIDS. Methodological issues of importance in understanding and evaluating depression in this patient population are described, and methodological variations between studies, particularly in reference to methods of case detection, diagnostic criteria used and characteristics of the populations studied, are identified. The findings reported in the current literature in general are contrary to what would be expected from an examination of the significant biological and psychosocial stresses of individuals with HIV, and are inconsistent with those of other life-threatening illnesses and CNS diseases. Clear conclusions regarding the prevalence of depression and its effect in patients with HIV/AIDS cannot yet be made.

Expression of human immunodeficiency virus type 1 in the nervous system of transgenic mice leads to neurological disease

Patients infected with the human immunodeficiency virus type 1 (HIV-1) frequently develop central and peripheral nervous system complications, some of which may reflect the effect of the virus itself. In order to elucidate the pathogenic mechanisms of HIV in neurological disease in a small animal model, we generated transgenic mice expressing the entire HIV genome under control of the promoter for the human neurofilament NF-L gene. The transgene was predominantly expressed in anterior thalamic and spinal motor neurons. Animals developed a neurological syndrome characterized by hypoactivity and weakness and by axonal degeneration in peripheral nerves. These results provide evidence for a role of HIV in affecting both the central and peripheral nervous systems. This animal model may also facilitate the development of therapeutic agents against the human disease.

Killing of primary CD4+ T cells by non-syncytium-inducing macrophage-tropic human immunodeficiency virus type 1

Understanding the mechanism by which human immunodeficiency virus type 1 (HIV-1) kills CD4+ T lymphocytes is important to the development of therapeutic and prophylactic strategies. Recent studies have indicated that, in some cases, progression to AIDS is associated with the appearance of syncytium-inducing, T cell line-tropic HIV-1 variants. Nevertheless, approximately 50% of subjects with AIDS harbor only non-syncytium-inducing, macrophage-tropic (NSI-M) variants of HIV-1. In most asymptomatic patients, NSI-M HIV-1 isolates are the predominant virus type found. We report here that cytopathicity of NSI-M HIV-1 for primary CD4+ T lymphocytes can be directly detected in vitro. The extent of CD4+ T-cell killing was not completely correlated with the rate of viral replication, suggesting that other characteristics of HIV-1 contribute to its cytopathicity. Our findings suggest that: (i) direct killing by NSI-M HIV-1 may contribute to CD4+ T-lymphocyte depletion in vivo, and (ii) the determinants of HIV-1 cytopathicity for CD4+ T lymphocytes and cell tropism or syncytia-forming ability are not necessarily tightly linked.

Aetiology and pathogenesis of hormonal and metabolic disorders in HIV infection

Many hormonal and metabolic disturbances are documented in HIV infection, the most important of which is the wasting syndrome associated with progressive HIV infection. We are only now beginning to understand the pathogenesis of these disturbances. In rare cases, infiltration of endocrine tissue by secondary infectious or malignant processes is the underlying cause of hormonal insufficiency. In most instances, however, hypofunction is secondary to the well-known effects of severe illness. Similarly, hyperfunction of the adrenal axis along with many of the derangements in substrate metabolism are also likely to be secondary to severe illness, perhaps through activation of cytokines and other molecules. Specific disturbances in asymptomatic patients are more difficult to document and may represent unique and as yet unexplained manifestations of HIV disease. Hypermetabolism and depletion of lean body mass are most profound in the acutely ill patient with active secondary infection. At this stage, the HIV-infected patient is in a catabolic state and adaptive mechanisms which normally decrease energy expenditure and preserve lean body mass are either overridden or not operative. Strategies to reverse the catabolic state and diminish wasting are only now being developed.

Hypothalamic and pituitary function in AIDS

Clinically relevant HP dysfunction occurs infrequently in the course of HIV infection and AIDS, and is usually due to destruction or infiltration of the region by opportunistic infections. However, more subtle defects occur with much greater frequency. Since these impairments, especially in the gonadotrophic and corticotrophic axes, are observed in HIV patients before the development of ARC or AIDS, direct involvement of the hypothalamus or pituitary by the neurotropic HIV virus or by other HIV-mediated factors is possible. Further investigation of hypothalamic and pituitary hormones by provocative means, in addition to assessment of the pulsatile secretion of these hormones, at all stages of HIV infection will be needed to clarify the role of the virus in these individuals.

Human immunodeficiency virus type 1 evolution in vivo tracked by DNA heteroduplex mobility assays

High mutation rates and strong selective pressures imposed on human immunodeficiency viruses in vivo result in the formation of pools of genetic variants known as quasispecies. DNA heteroduplex mobility and tracking analyses were used to monitor the generation of HIV sequence diversity, to estimate quasispecies complexity, and to assess the turnover of genetic variants to approach an understanding of the relationship between viral quasispecies evolution in vivo and disease progression. Proviral DNA pools were nearly homogeneous soon after sexual transmission. The emergence and clearance of individual variants then occurred at different rates in different individuals. High quasispecies complexity was found in long-term-infected, asymptomatic individuals, while rapid CD4+ cell decline and AIDS were often, but not always, associated with lower quasispecies complexity. Proviral genetic variation was often low following in vitro culture, because of the outgrowth of one or a few variants that often became more abundant only later as proviruses in peripheral blood mononuclear cells. These studies provide insight into the dynamics of human immunodeficiency virus sequence changes in vivo and illustrate the utility of heteroduplex analysis for the study of phenomena associated with rapid genetic changes.

High cerebrospinal fluid and serum levels of tumor necrosis factor-alpha in asymptomatic HIV-1 seropositive individuals. Correlation with interleukin-2 and soluble IL-2 receptor

The relationship between tumour necrosis factor-alpha (TNF-alpha) and the interleukin-2 (ILL-2) system in HIV-1 infection is important in understanding the dynamics of early immune response before the development of acquired immunodeficiency syndrome. Levels of TNF-alpha, IL-2 and soluble IL-2 receptor (sIL-2R) in serum and cerebrospinal fluid (CSF) samples from 31 asymptomatic HIV-1 seropositive individuals were measured. High levels of TNF-alpha were detected in CSF of 17 (55%) and serum of 22 (71%) subjects, 15 (88%) of whom had elevated CSF IL-2 levels and 16 (94%) had high sIL-2R levels. Moreover, CSF levels of TNF-alpha significantly correlated with CSF levels of IL-2 and sIL-2R. TNF-alpha, IL-2 and sIL-2R seem to be released within the intrathecal compartment early in the course of HIV-1 infection. In view of the known cytotoxic effects of TNF-alpha, an early release may contribute to subsequent development of neurological complications.

Tryptophan concentrations increase in cerebrospinal fluid and blood after zidovudine treatment in patients with HIV type 1 infection

Cerebrospinal fluid (CSF) and blood concentrations of indoleamines and catecholamines were analyzed in 14 HIV-1-seropositive individuals before antiviral treatment with zidovudine, after 3-14 months of treatment, and, in 8 of the patients, also after 14-30 months. The median pretreatment concentrations of tryptophan in CSF and blood were low (224 ng/ml and 6.0 micrograms/ml, respectively), but an increase in these values by an average of 40% in CSF and 23% in blood was seen after 3-14 months of zidovudine treatment (p < 0.01) and remained undiminished after 14-30 months of treatment. No significant change was observed in the 5-hydroxytryptamine (5-HT, serotonin) level in blood or in the CSF concentrations of the 5-HT metabolite 5-hydroxyindoleacetic acid (5-HIAA) and the dopamine metabolite homovanillic acid (HVA). The CSF concentrations of the noradrenalin metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG) had decreased by 12% on average (p < 0.01) by the time of the second follow-up, that is, after 14-30 months of zidovudine treatment. A decrease in neopterin during antiretroviral treatment correlated with an increase in tryptophan (p < 0.01). The data suggest that an association between decreased immune stimulation and reduced tryptophan degradation in patients treated with zidovudine.

Cerebral glial tumors and human immunodeficiency virus-1 infection. More than a coincidental association

BACKGROUND

The authors describe the clinical and morphologic patterns in four patients with acquired immune deficiency syndrome (AIDS) who developed intracranial glial tumors.

METHODS

This retrospective study reports 70 patients at various stages of human immunodeficiency virus-1 (HIV-1) infection who underwent stereotactic brain biopsy for an intracerebral space-occupying lesion.

RESULTS

Of these patients, four had glial tumors: one astroblastoma, two astrocytomas, and one glioblastoma. Glial tumors probably arise from a complex interplay of factors; possibilities include the activation of a dominant oncogene or viral inactivation of a tumor suppressor gene by a viral promoter (like the tat protein), impairment of immune defenses (which facilitates the growth of astrocytomas in acute lymphoblastic leukemia), production of cellular growth factors, cytokines, possible infection of glial cells by HIV, and the potentiation of a coinfectious agent.

CONCLUSIONS

These cases illustrate that glial tumors should be considered in the differential diagnosis of brain masses in HIV-1 infection, especially because specific treatment for these tumors is available. Moreover, the occurrence of glial tumors in AIDS patients is not only an important event from a clinical point of view, but may also have implications for the pathogenesis of tumors in AIDS.

Cerebrospinal fluid HIV-1 p24 antigen and culture: sensitivity and specificity for AIDS-dementia complex

We prospectively evaluated 94 patients with AIDS-dementia complex (ADC) and a smaller group of 27 patients with other HIV-1 related neurological conditions to determine the usefulness of cerebrospinal fluid (CSF) p24 antigen and HIV-1 culture in the diagnosis of ADC. The presence of ADC correlated with detectable CSF p24, but not with a positive culture. However, only 54% of the patients with severe or end stage (stages 3 and 4) ADC had detectable CSF p24 and only 25% had a positive culture. Among those with detectable CSF p24, there was no discernible relationship between the severity of ADC and the amount of CSF p24. The diagnostic sensitivity of CSF p24 in ADC was 21% whereas the specificity was 98%. CSF HIV-1 culture had a sensitivity of 30% and a specificity of 80%. To address the possibility of binding of p24 in immune complexes, thereby escaping detection, an acid hydrolysis procedure was performed on the CSF and serum samples. This did not, however, make an appreciable difference in the detection rate of p24. To delineate whether the finding of cell free virus in the CSF was associated with ADC, CSF culture for HIV-1 was performed on both cell depleted and cell associated fractions. It was uncommon for CSF to be culture positive in only the cell free fraction and there was no relationship to the presence or severity of ADC.

Cerebrospinal fluid human immunodeficiency virus type 1 (HIV-1) p24 antigen levels in HIV-1-related dementia

Human immunodeficiency virus type 1 (HIV-1) p24 antigen, a putative marker of virus load, was assayed in 79 blood and 83 cerebrospinal fluid (CSF) samples from 90 HIV-1-seropositive individuals with or without dementia. Twenty-eight subjects had no evidence of neuropsychological impairment, 17 had mild impairment without objective evidence of dementia, and 45 were demented. HIV-1 p24 antigen was detected more frequently in CSF samples from demented (19/40) than normal (1/26) or mildly impaired (1/17) subjects and in 67% of individuals with significant dementia (MSK stages 2-4). p24 Antigen was detected less frequently in CSF from demented subjects on antiretroviral drugs than untreated demented individuals. Overall, the sensitivity of the antigen capture assay in CSF among demented individuals was 47.5%; the specificity, 95.0%; positive predictive value, 90.4%; negative predictive value, 66.1%; and the efficiency, 72.2%. A direct relationship was also noted between the degree of cognitive impairment and blood p24 antigen detection frequency and antigen concentration. CD4+ blood lymphocyte counts were lower for demented individuals, and HIV-1 p24 antigen was detected more frequently and p24 antigen concentration was higher in blood and CSF from individuals with low CD4+ blood lymphocyte counts. beta 2-Microglobulin levels were higher in CSF from demented subjects and correlated directly with CSF p24 antigen concentration. However, in contrast to CD4+ blood lymphocyte counts and beta 2-microglobulin levels, only p24 antigen concentration correlated with dementia severity. Therefore, p24 antigen can be a useful marker for dementia related to HIV-1 infection.

Ophthalmoplegia associated with AIDS

A 34-year-old man with AIDS was admitted to the hospital with a one-week history of cough, chest pain, and fever. Radiography revealed a cavitating left upper lobe lesion. Two weeks later he developed a headache associated with a contrast enhancing lesion in the right parietal lobe. The patient had a progressive downhill course, developing atrioventricular block and hypernatremia. Neuro-ophthalmologically, there was a mild facial droop, "hand motions" vision with presumed bilateral cytomegalic inclusion retinitis, and signs of a mesencephalic syndrome, including lid retraction. Discussions center on the differential diagnosis of the central nervous system disease and the obligative recommendations the neuro-ophthalmologist must be willing to make.

Early detection of distal symmetrical polyneuropathy during HIV infection by paired stimulation of sural nerve

In 203 HIV infected patients in various clinical stages neurological examination, paired stimulation (LPSS), nerve conduction velocity (NCVS) and amplitude (AMPS) of the sural nerve, distal latency (DLP), nerve conduction velocity (NCVP), amplitude (AMPP) and F waves of the peroneal nerve were recorded. Neurological examination revealed symptoms and clinical signs of polyneuropathy in 67 (33%) (WR 1-6) of the patients. LPSS after paired stimulation was abnormal in 25.5%, NCVS in 14.2%, AMPS in 9.8%, NCVP in 11.8%, DLP in 11.2%, AMPP in 5.9% and FWP in 14.6%. Our findings indicate a high incidence of peripheral nerve system involvement during HIV infection. In 11.5% of all patients only LPSS proved polyneuropathy. Neurophysiological results from HIV infected patients with symptoms and clinical signs of polyneuropathy were statistically significantly different from HIV infected patients without symptoms and clinical signs of polyneuropathy. The delay of LPSS represents the most sensitive neurophysiological indicator of polyneuropathy during HIV infection and announces the onset of peripheral nerve disease even in early stages of infection, according to Walter Reed staging classification 1 and 2 (approx. 20%).

The Soriano Award Lecture. Emerging infections of the nervous system

The epidemic of acquired immunodeficiency disease [AIDS] has focused interest on the origins of "new" infectious agents. Great plagues are well known from the distant past, but a number of novel diseases affecting the nervous system infections have emerged in recent years. The causes of such new disorders are diverse: whereas rapid mutations of microbes allow the evolution of truly novel agents, the appearance of new diseases is more often due to changes in human or vector populations or changes in societal mores that result in dissemination of preexistent microbes. Examples of recently emerging infections that involve the nervous system include the enterovirus 70 epidemics with poliomyelitis-like disease, the appearance of California virus encephalitis in the midwestern United States, the rapid spread of Lyme disease with its many neurological complications in the eastern United States, and the outbreak of bovine spongiform encephalopathy in the United Kingdom, in addition to the devastating epidemic of human immunodeficiency virus (HIV), which will cause nervous system disease in over half of those infected. As the world population increases and modern transportation brings us closer into a "global village" more new agents will emerge and more will be sustained. Knowledge of the molecular biology and ecology of the agents and awareness of how our actions can alter their behavior are our best defense.

HIV-1 infection of the developing nervous system: central role of astrocytes in pathogenesis

Recent studies in our laboratory and that of Dr. Howard Gendelman have revealed two important pathways for neuronal damage during HIV-1 encephalopathy in children. First, substantial numbers of astrocytes are actively or latently infected with HIV-1. Astrocyte infection may lead to neuronal dysfunction through loss of supporting growth factors, excitotoxicity due to dysregulation of neurotransmitter reuptake, and loosening of the blood-brain barrier permitting further seeding of HIV-1 in the CNS. Significantly, infection of astrocytes is marked by near-exclusive synthesis of early regulatory gene products of HIV-1, while structural proteins characteristic of productive infection are found in macrophages, microglia and multinucleated giant cells. We propose the term 'restricted' to denote the non-productive infection found in astrocytes. Second, HIV-1-infected macrophages initiate inflammatory processes which are amplified through cell-cell interactions with astrocytes. Macrophage-astrocyte interactions produce arachidonic metabolites and potentially neurotoxic cytokines (TNF-alpha and IL-1 beta), leading to astroglial activation and proliferation which then amplifies these cellular processes. These new findings suggest that two major pathways leading to neurotoxicity in pediatric AIDS encephalopathy are linked to HIV-1 infection through astrocyte-mediated processes, and help explain how small numbers of productivity infected cells indirectly cause widespread tissue pathology and elicit profound neurological impairment.

Adamantane as a brain-directed drug carrier for poorly absorbed drug. 2. AZT derivatives conjugated with the 1-adamantane moiety

Five AZT (azidothymidine) prodrugs conjugated with the 1-adamantane moiety via an ester bond were synthesized to improve the transport of AZT into the central nervous system (CNS). In in vitro degradation studies with rat and human plasma, it was demonstrated that the prodrugs were degraded enzymatically and converted quantitatively to their parent drug. AZT. As assessed by octanol-buffer partitioning, the prodrugs were much more lipophilic than AZT and were expected to penetrate the blood-brain barrier (BBB) readily. In in vivo studies, in which the prodrugs were administered intravenously to rat, the prodrugs in brain tissue were detected at 7-18 times higher concentrations than AZT in spite of the negligible amount of the prodrug in the cerebrospinal fluid. These results indicate that the introduction to AZT of the 1-adamantane moiety results in the enhancement of the BBB penetration. This pharmaceutical approach would be beneficial for the efficient treatment of the CNS infection by human immunodeficiency virus.

HIV infection and the dentist. 1. The presence of HIV in saliva and its implications to dental practice

The human immunodeficiency virus (HIV) has been detected in all body fluids. The presence and the detection of HIV virus in human saliva are reviewed. Modes of HIV transmission are discussed with particular reference to the possibility and risk of virus transmission via saliva. This risk is considered to be extremely low. The relevance of this information to the practising dentist is discussed and some practical suggestions in infection control are made.

Impact of dosing schedule upon suppression of a retrovirus in a murine model of AIDS encephalopathy

We studied the impact of zidovudine (AZT) in Cas-Br-M murine leukemia virus-infected NFS-N mice after administration by once-daily bolus or continuous infusion. While higher peak concentrations of AZT were achieved by once-daily dosing, continuous AZT infusion at 25 micrograms/h maintained levels > 1 microM in plasma and > 0.2 microM in the brain. Continuous infusion provided significantly better viral inhibition, even though total doses were only one-third that of the once-daily therapy group.

A pathologically distinct new form of HIV associated encephalopathy

We present the clinical, morphological and neuropathological findings in a 44-year-old male suffering from the acquired immunodeficiency syndrome (AIDS) (CDC stage IV C2) who presented with rapidly progressive right-side hemiparesis and developed hemianopia and aphasia. Scans showed multiple, not contrast-enhancing, not space-occupying echo-intensive lesions in T2-weighted MR-imaging. No hint for an opportunistic infection, necrotizing vasculitis or vascular disease was found. All therapeutic regimens failed and 8 weeks after onset of neurological symptoms the patient died because of cardiorespiratory arrest. Post-mortem examination excluded opportunistic infection, progressive multifocal leukoencephalopathy, lymphoma, vasculitis and ischemia of the brain. In the presence of an unusually high amount of HIV-infected macrophages at immunohistochemical examination, the overall pathological findings were atypical both for HIV encephalitis and HIV leukoencephalopathy. We describe a pathologically distinct new form of HIV associated encephalopathy.

AAEM minimonograph #41: neuromuscular diseases associated with HIV-1 infection

Neuromuscular diseases occur in as many as 50% of patients infected with human immunodeficiency virus type 1 (HIV-1). All forms of neuromuscular disease have been reported, including axonal neuropathy, demyelinating neuropathy, mononeuropathy multiplex, polyradiculitis, ALS-like syndromes, disorders of neuromuscular transmission, myopathy, and toxic neuropathies due to medication side effects. Neuromuscular disease is often the presenting manifestation of HIV-1 infection. Infection with cytomegalovirus (CMV) is associated with different types of neuropathy including mononeuritis multiplex and polyradiculopathy. There is effective treatment for many of the associated disorders including chronic inflammatory demyelinating neuropathy, CMV-mediated neuropathies, and myopathy. Treatment of CMV-mediated mononeuropathy multiplex may be life saving. The different neuromuscular syndromes associated with different stages of HIV-1 infection may be due, in part, to different levels of immunocompetence.

AIDS and the neurosurgeon--an update

Over the past decade, acquired immunodeficiency syndrome (AIDS) has become the leading public health crisis in the United States, Western Europe, and Africa. Despite improvements in the diagnosis and treatment of AIDS-related disorders, the number of people infected with the human immunodeficiency virus (HIV-1) continues to grow, requiring a greater proportion of limited financial, medical, and human resources. Since nearly one half of symptomatic AIDS patients have neuropathologic disease, clinicians must be aware of the myriad neurologic manifestations of AIDS and use the most effective methods to diagnose and treat them. The work-up of the AIDS patient with neurologic symptoms includes a careful history and physical examination, laboratory studies, and radiographic imaging. Gadolinium-enhanced magnetic resonance (MR) imaging has become the radiographic screening study of choice. MR imaging can be used to predict which patients should undergo stereotactic biopsy before an empirical trial of antitoxoplasmosis therapy. Any patient with a mass lesion that does not respond to empirical therapy for toxoplasmosis should also undergo biopsy to exclude another treatable disorder. While the number of patients with neurological complications can be expected to increase in the near future, better imaging techniques may obviate the need for biopsy in many of these patients. The increasing threat of HIV-1 infection in the workplace requires meticulous care both in and out of the operating room to minimize accidental exposure of health-care workers.

The virology of demyelinating diseases

Infectious agents have been postulated as causes of multiple sclerosis for over a century. The possible role of a virus or viruses is supported by data that (1) a childhood exposure is involved and "viral" infections may precipitate exacerbations of disease, (2) experimental infections in animals and natural infections in humans can cause diseases with long incubation periods, remitting and relapsing courses, and demyelination, and (3) patients with multiple sclerosis have abnormal immune responses to viruses. The pathogenesis of three human demyelinating diseases of known viral etiology is discussed. In progressive multifocal leukoencephalopathy, a papovavirus selectively infects oligodendrocytes and causes focal areas of demyelination. In postmeasles encephalomyelitis, the virus is lymphotrophic and disrupts immune regulation that can result in an autoimmune perivenular demyelinating illness without evidence of infection of the central nervous system. In human immunodeficiency virus-encephalopathy and myelopathy virus is present in macrophages and microglia and the myelin abnormalities apparently are caused by soluble factors such as viral proteins, cytokines, or neurotoxins. These findings may have implications on how, when, and where to seek viruses in multiple sclerosis.

Post mortem examinations of HIV infected patients: a nationwide survey

AIMS

To identify the number and geographical distribution of post mortem examinations performed on HIV infected cadavers; to identify the areas that perform post mortem examinations so that, by invitation and discussion, a national post mortem network could be initiated.

METHODS

A nationwide survey of Royal College of Pathologists' district tutors (n = 216) was done by postal questionnaire. These were completed by the district tutors or passed on to their histopathologist colleagues. The results were collated after three months. After one follow up letter, an 86% response rate, which is a significant sample, was achieved.

RESULTS

Twenty eight per cent of respondents were performing HIV post mortem examinations. Of those who were not performing them (30%), the lack of clinical or coroner requests was the most common explanation. All regions provide facilities for HIV post mortem examinations, as judged by the responses.

CONCLUSIONS

These findings are of singular importance as it is the first United Kingdom survey investigating the distribution of post mortem examinations on HIV infected cadavers. Studying post mortem material using a systemic, coordinated collection of brain tissue is essential to increase knowledge of a new disease of pandemic proportions.

Human immunodeficiency virus infection of human brain capillary endothelial cells occurs via a CD4/galactosylceramide-independent mechanism

Neuropathologic studies of AIDS patients have shown that brain capillary endothelial cells are a cellular target for human immunodeficiency virus (HIV) in vivo. We have established in vitro cultures of primary human brain capillary endothelial (HBCE) cells. Using this model system, we have shown a significant HIV infection of HBCE cells that is productive yet noncytopathic. The infection is mediated by a cellular interaction with gp120 that does not involve CD4 or galactosylceramide. HIV infection of HBCE cells may contribute to AIDS-associated neuropathology by disturbing the physiology of the endothelium and directly or indirectly facilitating dissemination of virus to the central nervous system.

Neuropathological studies in the brains of AIDS patients with opportunistic diseases

The brains of 70 fatal cases with AIDS were studied by means of immunohistochemistry and in-situ hybridization in a consecutive autopsy series (1985-July 1992). In addition, the neuropathological changes were correlated with the neurological and neuroimaging findings. Opportunistic infections included toxoplasmosis (15 cases), cytomegalovirus (CMV)-encephalitis (6), progressive multifocal leucoencephalopathy (2) and fungal infections (3). Malignant lymphomas were found in 7 patients; 6 involved primarily the CNS, one was metastatic. In 14 cases the neuropathological changes were consistent with HIV encephalitis and HIV leucoencephalopathy. Non-specific lesions occurred in 31 cases. The clinical diagnosis in patients with opportunistic diseases (n = 27) diverged in 15 cases (55%) from the underlying pathology. Toxoplasma gondii, CMV and JC viruses were identified by immunohistochemistry and in-situ hybridization on serial paraffin sections. In addition, antibodies against lymphocyte subsets, tissue macrophages, the glial fibrillary acid protein (GFAP) and myelin basic protein were used to characterize the phenotype of cells and to highlight the degree of gliosis and demyelination. Our results show that the distribution and degree of morphological changes might be helpful for the differential diagnosis antemortem. Since neurological complications may represent the first or sole manifestation of AIDS and risk factors for AIDS are often not known, it should be taken into account that CNS manifestations of AIDS may contribute to a sudden and unexpected death or accident. Opportunistic diseases should be considered as a possible differential diagnosis in cases mimicking the clinical picture of apoplexia or dementia. Furthermore, CNS lesions may be detected postmortem in patients who were not known to suffer from Neuro-Aids during life, indicating that CNS involvement is more widespread than assumed.

Low levels of specific T cell activation marker CD27 accompanied by elevated levels of markers for non-specific immune activation in the cerebrospinal fluid of patients with AIDS dementia complex

Concentrations of soluble receptors for tumor necrosis factor (sTNFR-p55 and sTNFR-p75) and soluble T cell antigens CD25 and CD27 (sCD25 and sCD27) were measured in paired serum/cerebrospinal fluid (CSF) samples of 15 patients with AIDS dementia complex (ADC) and 15 HIV-infected control subjects (11 with other central nervous system (CNS) infections and four without CNS infection). In this study levels of sTNFR-p55, sTNFR-p75 and sCD25 were elevated in the CSF of ADC patients and of the 11 patients with other CNS infections, whereas CSF-levels of the specific T cell marker sCD27 were lower in patients with ADC as compared to the control subjects with and without other CNS infections. This pattern suggests a relative failure of eliciting a T cell-mediated immune response intrathecally in patients with ADC.

Central nervous system pathology in pediatric AIDS

Children with AIDS frequently have neurological manifestations due to complications of immunodeficiency or intrinsic effects of human immunodeficiency virus type 1 (HIV-1) on the central nervous system (CNS). The most common neurological disorders not directly related to HIV-1 infection include cerebrovascular disease and lymphoma. Global anoxic-ischemic and necrotizing encephalopathies are frequent, while CNS hemorrhages and arteriopathies are less frequent. Opportunistic CNS infections are uncommon, limited predominantly to monilial and cytomegaloviral encephalitides. Only a few cases of CNS toxoplasmosis have been reported in children. CNS lymphomas often occur in the setting of systemic polymorphous, polyclonal B-cell proliferations that have been associated with Epstein-Barr virus infection. Intrinsic effects of HIV-1 on the CNS include microcephaly, diffuse gliosis, basal ganglia mineralization, HIV encephalitis, and corticospinal tract degeneration. Although viral antigens can be detected in microglia and multinucleated cells in HIV encephalitis, most of the CNS effects of HIV-1 infection cannot be attributed to detectable levels of viral antigen, suggesting that the pediatric CNS is unusually susceptible to low-level HIV-1 infection or to systemic effects of HIV-1 infection, possibly mediated by soluble factors, including the inflammatory cytokines, interleukin-1 beta, and tumor necrosis factor-alpha, which have been shown to be increased in serum and cerebrospinal fluid of children with AIDS.

Neurologic syndromes

It is now well recognized that HIV-1 associated CNS disease may complicate the course of HIV-1 infection and AIDS in infants and children. It is also well recognized that the neurologic dysfunction in these young patients adds significantly to the morbidity of the disease and is often a devastating complication. It is apparent that HIV-1 CNS infection in infants and young children is complicated by numerous developmental issues. The effects, direct and indirect, of HIV-1 on the developing nervous system must be considered. The effects of HIV-1 on the immature immune system must also be considered. Moreover, the possible effects of HIV-1 on the many complex interactions between these two systems during development will clearly also require investigation. In order to care for these children and to design rational approaches for treatment and prevention, it is now critical to develop a better understanding of how HIV-1 affects the developing nervous system.

Human immunodeficiency virus type 1 infection of the brain

Direct infection of the central nervous system by human immunodeficiency virus type 1 (HIV-1), the causative agent of AIDS, was not appreciated in the early years of the AIDS epidemic. Neurological complications associated with AIDS were largely attributed to opportunistic infections that arose as a result of the immunocompromised state of the patient and to depression. In 1985, several groups succeeded in isolating HIV-1 directly from brain tissue. Also that year, the viral genome was completely sequenced, and HIV-1 was found to belong to a neurotropic subfamily of retrovirus known as the Lentivirinae. These findings clearly indicated that direct HIV-1 infection of the central nervous system played a role in the development of AIDS-related neurological disease. This review summarizes the clinical manifestations of HIV-1 infection of the central nervous system and the related neuropathology, the tropism of HIV-1 for specific cell types both within and outside of the nervous system, the possible mechanisms by which HIV-1 damages the nervous system, and the current strategies for diagnosis and treatment of HIV-1-associated neuropathology.

Mechanisms of immune activation of human immunodeficiency virus in monocytes/macrophages

Monocytes/macrophages (M/M) are the major host of human immunodeficiency virus (HIV) in solid tissues. However, blood monocytes are nonpermissive for HIV infection, indicating that M/M activation or differentiation is necessary for HIV replication. Since M/M are activated during immune responses, we investigated the effect of T-cell activation on HIV expression in M/M derived from peripheral blood of HIV-infected individuals. Previously, we reported that coculture of monocytes from HIV-infected donors with T cells and mitogens resulted in M/M differentiation and HIV expression. Production of HIV by M/M from infected donors required direct contact between monocytes and T cells (for the first 24 h), and the response to alloantigens, but not mitogens, was restricted to HLA-DR. In this study, we found that HIV was more readily recovered from M/M of asymptomatic HIV seropositive donors (69%) than from M/M of symptomatic donors (57%). Viral antigens (e.g., inactivated herpes simplex virus) could initiate the immune response and HIV expression. The ability of noninfected T cells to activate HIV expression in M/M and observations that treatments of M/M with antibodies to deplete T cells did not reduce HIV expression suggested that the monocytes were endogenously infected. To define the aspects of immune activation specifically involved in initiating HIV expression in M/M, interactions of M/M and T cells and participation of cytokines were investigated. The T cell which activated M/M was CD4+ CD8-. Fixed allogeneic cells are known to induce T-cell activation but were not able to serve as antigen for M/M differentiation, suggesting that M/M may need to function as antigen-presenting cells to receive the signal to differentiate and express HIV. Blocking of M/M-T-cell interaction with antibodies directed against LFA-1 or interleukin-1 prevented HIV expression. However, inhibition of later stages of T-cell activation, such as blocking of interleukin-2 receptors, did not diminish HIV expression in M/M. Consistent with the requirement for cell-cell contact between M/M and T cells, a variety of cytokines were unable to initiate HIV replication in M/M. The ability of T cells to induce cellular differentiation and HIV replication in M/M in vitro suggests that initiation of an immune response to an antigen, such as an opportunistic pathogen, could be a mechanism by which HIV disseminates to tissues in vivo.

Muscle disease, HIV and zidovudine: the spectrum of muscle disease in HIV-infected individuals treated with zidovudine

Eleven patients with AIDS or AIDS-related complex who developed muscle-related symptoms whilst taking zidovudine were investigated. The clinical details of a further ten patients who did not undergo muscle biopsy are also outlined. The clinical features, quantitative muscle strength testing, electromyographic findings, serial creatine kinase levels, muscle biopsy appearance on light microscopy and the effects of zidovudine withdrawal and rechallenge are described. The spectrum of muscle disease encountered included four cases of frank myopathy diagnosed using clinical, electrophysiological and histological criteria, four patients with mild weakness and myalgia in whom muscle biopsies were normal, three patients with myalgia only and a mild increase in the interstitial cell infiltrate shown by biopsy. The patients presenting with myopathy showed no improvement on withdrawal of zidovudine but responded to immunosuppressive therapy with steroids and, in one case, thalidomide prescribed incidentally. At present, it is not yet possible to clinically define a specific zidovudine-induced myopathy that is distinct from the other effects of HIV infection on muscle structure and function. Our experience suggests that zidovudine may be implicated as a myotoxin in some patients, particularly those with myalgia and mild weakness. In those patients with severe weakness, and with biopsy findings of necrosis and inflammation, the drug effects may be difficult to separate from the primary effects of HIV.

Intravascular distribution of zidovudine: role of plasma proteins and whole blood components

Knowledge of drug protein-binding and blood cell partitioning may be important for evaluating the pharmacokinetic parameters of zidovudine, particularly because of its intracellular site of action and potential to induce side effects. Equilibrium dialysis studies of zidovudine were performed over 2 h to identify the extent and site of binding. Zidovudine was added to anticoagulated whole blood to study blood cell distribution over a 24 h period at 37 degrees C and at 21 degrees C. Concurrent plasma and whole blood samples were determined at various time-points and blood partitioning was determined by application of a mass balance equation. All samples were analyzed using radioimmunoassay. The free fraction of zidovudine at a concentration of 500 ng/ml (1.7 microM) was 0.77 +/- 0.05 in plasma, 0.78 +/- 0.03 in serum, 0.88 +/- 0.03 in 4 g/dl albumin solution, and 1.0 in 100 mg/dl alpha 1-acid glycoprotein solution. A free fraction of 0.72 +/- 0.10 was observed in plasma from HIV-infected patients with zidovudine concentrations ranging from 16 to 91 ng/ml. Zidovudine equilibration between plasma and blood cells occurred rapidly, being complete within 10 min. After equilibrium was complete, the mean whole blood:plasma ratio was 0.86 +/- 0.02 and 0.80 +/- 0.04 (P = 0.20) and mean blood cell Partitioning ratio, [cell]/[plasma-free], was 0.85 +/- 0.06 and 0.66 +/- 0.14 (P = 0.25) for studies at 37 degrees C and 21 degrees C, respectively. The partitioning ratio was relatively consistent over the study period, suggesting no accumulation in blood cells. These results suggest that zidovudine binds to a small extent primarily to albumin. The free concentration equilibrates readily between blood cells and plasma independent of concentration and without signs of accumulation.

Antisense phosphorothioate oligodeoxynucleotides targeted to the vpr gene inhibit human immunodeficiency virus type 1 replication in primary human macrophages

The replication of human immunodeficiency viruses (HIV) in human macrophages is influenced by genetic determinants which have been mapped predominantly to the viral envelope. However, in HIV-2, the vpr gene has also been suggested as an important modulator of viral expression in human macrophages. We synthesized five antisense phosphorothioate oligodeoxynucleotides complementary to the vpr mRNA of HIV-1Ba-L, a highly macrophage-tropic viral strain, and measured their effect on HIV-1Ba-L replication in primary human macrophages. All of the oligodeoxynucleotides displayed some level of non-sequence-specific inhibition of viral replication; however, only the antisense one had an additional effect on viral production in primary macrophages. Of the five antisense oligodeoxynucleotides tested, only one did not show any additional effect on viral production, whereas all the others inhibited viral replication to a similar degree (70 to 100%). Variation in the degree of inhibition was observed by using five different donors of human primary macrophages. The phosphorothioate oligonucleotides, targeted to the initiating methionine of the Vpr protein, had an inhibitory effect at both 20 and 10 microM only when the size was increased from 24 to 27 bases. Thus, HIV-1 replication in human macrophages is modulated by the expression of the vpr gene, and it is conceivable that vpr antisense oligodeoxynucleotides could be used in combination with antisense oligodeoxynucleotides against other HIV-1 regulatory genes to better control viral expression in human macrophages.

Human submandibular saliva aggregates HIV

Incubation of HIV with human whole, parotid, or submandibular saliva leads to a decrease in viral infectivity in Sup-T1 cells. The effect is most pronounced with submandibular saliva. Inhibition is seen within 2 min, and increases with time. There is little inhibition seen after incubation of saliva with HSV, and no effect with adenovirus, suggested that there is some viral specificity. Electron microscopic studies revealed that HIV-saliva aggregates are trapped in 0.45-microns pore size nitrocellulose filters. If these inhibitory effects are manifest in vivo, this could account for the low level of virus detected in oral secretions.

Antibodies to recombinant gp160 in mucosal secretions and sera of persons infected with HIV-1 and seronegative vaccine recipients

An enzyme immunoassay (EIA) was developed to detect secretory IgA (sIgA) antibodies to HIV-1 envelope glycoprotein, using a mouse monoclonal antibody and a highly purified, baculovirus-expressed recombinant gp160 (rgp160) as antigen. Detection of sIgA was enhanced by prior immunoprecipitation of IgG. IgG and sIgA rgp160 antibodies were measured in parotid saliva and nasal wash samples of 18 HIV-1-seropositive volunteers and 14 HIV-1-seronegative adult volunteers immunized 3 times with HIV-1 IIIB rgp160 vaccine at 1 of 4 dosage levels: 40 micrograms (N = 3), 80 micrograms (N = 3), 160 micrograms (N = 4), and 640 micrograms (N = 4). We detected rgp160-specific IgG antibody in the nasal wash samples of all HIV-1-seropositive volunteers and 4/8 vaccinees (50%) immunized with the two highest doses of rgp160 vaccine. All infected volunteers tested had rgp160-specific sIgA in their nasal wash samples. None of the vaccinees and very few of infected volunteer specimens had detectable antibody in the parotid saliva samples (5/8 had IgG and 1/8 had sIgA). We also detected IgG antibody to rgp160 in the sera of all infected volunteers and 13/14 vaccinees (93%). With this EIA, sIgA antibody can be measured in mucosal secretions of recipients of appropriate candidate HIV-1 vaccines.

Cranial computed tomography in the emergency department evaluation of HIV-infected patients with neurologic complaints

STUDY OBJECTIVE

To demonstrate the usefulness of cranial computed tomography (CT) in the emergency department evaluation of HIV-infected patients and patients with risk factors for HIV infection who present with neurologic complaints.

DESIGN

Retrospective review of imaging reports and medical records of patients who visited the ED from March 1991 through March 1992.

SETTING

Urban university ED.

PARTICIPANTS

Patients with HIV infection or risk factors for infection who underwent emergency cranial CT after presenting to the ED with headache, altered mental status, focal deficits, or other neurologic signs or symptoms.

RESULTS

One hundred forty-six patients visited the ED 169 times. Of the 169 cranial CTs obtained, 85 (50%) were normal, 49 (29%) showed atrophy only, and 35 (21%) demonstrated focal lesions, with mass effect noted in ten (6%). Enhancing lesions were present in 13 scans. In 21 (12%) cases, CT revealed either an indication for admission, a contraindication to lumbar puncture, or both. In 25 instances, patients with lesions had nonfocal presentations and no papilledema. Two presentations--focal deficit and altered mental status--were each statistically significantly associated with lesions on CT. In seven patients with multiple ED visits, repeat CT showed new findings. Among patients who had risk factors but were of unknown HIV status, there was the same proportion of abnormal scans as in known HIV-infected patients.

CONCLUSION

CT detected clinically significant neuropathology among our study patients. Because lesions and mass effect were associated with nonfocal as well as focal presentations, CT is indicated in every neurologically symptomatic patient with HIV infection or risk factors for infection. Because HIV-related diseases can progress rapidly, repeat CT is recommended even in patients with recent scans.