Incidence and prevalence of neurological disorders associated with HIV since the introduction of highly active antiretroviral therapy (HAART)

Impact of highly active antiretroviral therapy on organ-specific manifestations of HIV-1 infection

In the last 10 years, interesting results have been reported concerning the impact of highly active antiretroviral therapy (HAART) on the changing pattern of organ‐specific manifestations of HIV‐1 infection. There has been a clear step‐wise reduction in the incidence of several opportunistic infections (OIs), particularly Pneumocystis carinii pneumonia, whereas a nonsignificant reduction in incidence has been observed for other organ‐specific diseases, including invasive cervical cancer and Hodgkin disease. In addition, several organ‐specific manifestations, including HIV‐associated nephropathy, wasting syndrome and cardiomiopathy, are a direct consequence of damage by HIV‐1, and so HAART may have a therapeutic effect in improving or preventing these manifestations. Finally, the introduction of HAART has seen the emergence of several complications, termed immune reconstitution inflammatory syndrome, which includes OIs such as cytomegalovirus vitritis, Mycobacterium avium complex lymphadenitis, paradoxical responses to treatment for tuberculosis, and exacerbation of cryptococcosis. Because not all HIV‐1 organ‐specific manifestations are decreasing in the HAART era, this review will analyse the influence of HAART on several organ‐specific manifestations, and in particular OIs related to several organs, cerebral disorders and HIV‐1‐related neoplasia.

Cross talk between growth factors and viral and cellular factors alters neuronal signaling pathways: implication for HIV-associated dementia

HIV-associated dementia (HAD) is a serious neurological disorder affecting about 7% of people with AIDS. In the brain, HIV-1 infects a restricted number of cell types, being primarily present in macrophages and microglial cells, less abundant in astrocytes, and rarely seen in oligodendrocytes and neurons. Lack of a productive HIV-1 infection of neuronal cells suggests the presence of an indirect pathway by which the virus may determine the brain pathology and neuronal dysfunction seen in AIDS patients. Among the participants in this event, viral proteins including gp120 and Tat, along with host factors including cytokines, chemokines, and several signaling pathways have received considerable attention. In this article, we discuss the most recent concepts pertaining to the mechanisms of HIV-1-induced neuronal dysfunction by highlighting the interplay between signal transduction pathways activated by viral and host factors and their consequences in neuronal cell function.

Heavy alcohol consumption in individuals with HIV infection: effects on neuropsychological performance

Higher rates of alcohol use have been reported in HIV+ individuals compared to the general population. Both heavy alcohol use and HIV infection are associated with increased risk of neuropsychological (NP) impairment. We examined effects of heavy active alcohol use and HIV on NP functioning in a large sample of community-residing HIV+ individuals and HIV- controls. The four main study groups included 72 HIV- light/non-drinkers, 70 HIV- heavy drinkers (>100 drinks per month), 70 HIV+ light/non-drinkers, and 56 HIV+ heavy drinkers. The heavy drinking group was further subdivided to assess effects of the heaviest levels of active alcohol use (>6 drinks per day) on NP functioning. A comprehensive NP battery was administered. Multivariate analysis of covariance was employed to examine the effect of HIV and alcohol on NP functioning after adjusting for group differences in age and estimated premorbid verbal intellectual functioning. The analyses identified main effects of heavy drinking and HIV on NP function, with greatest effects involving the contrast of HIV+ heavy drinkers and the HIV- light drinkers. Synergistic effects of heaviest current drinking and HIV infection were identified in analyses of motor and visuomotor speed. Supplementary analyses also revealed better NP function in the HIV+ group with antiretroviral treatment (ART) and lower level of viral burden, a finding that was consistent across levels of alcohol consumption. Finally, heavy alcohol use and executive functioning difficulties were associated with lower levels of self-reported medication adherence in the HIV+ group. The findings suggest that active heavy alcohol use and HIV infection have additive adverse effects on NP function, that they may show synergistic effects in circumstances of very heavy active alcohol use, and that heavy drinking and executive functioning may mediate health-related behaviors in HIV disease.

Role of activated astrocytes in neuronal damage: potential links to HIV-1-associated dementia

HIV-1-associated dementia (HAD) is an important complication of HIV-1 infection. Reactive astrogliosis is a key pathological feature in HAD brains and in other central nervous system (CNS) diseases. Activated astroglia may play a critical role in CNS inflammatory diseases such as HAD. In order to test the hypothesis that activated astrocytes cause neuronal injury, we stimulated primary human fetal astrocytes with HAD-relevant pro-inflammatory cytokine IL-1beta. IL-1beta-activated astrocytes induced apoptosis and significant changes in metabolic activity in primary human neurons. An FITC-conjugated pan-caspase inhibitor peptide FITC-VAD-FMK was used for confirming caspase activation in neurons. IL-1beta activation enhanced the expression of death protein FasL in astrocytes, suggesting that FasL is one of the potential factors responsible for neurotoxicity observed in HAD and other CNS diseases involving glial inflammation. Our data presented here add to the developing picture of role of activated glia in HAD pathogenesis.

HIV-1 expression protects macrophages and microglia from apoptotic death

Macrophages and microglia are the predominant cells infected with HIV-1 in the brain, yet the effects of productive HIV infection on the fate of these cells are poorly understood. In this study, we tested the hypothesis that HIV-1 expression influences cell death in infected macrophages and microglial cells. We detected apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) in the cerebral white matter of control and HIV encephalitis (HIVE) brains, and quantitatively analysed apoptotic cells with respect to their location (vessel-associated vs. parenchymal), CD68 expression, and HIV-1 p24 expression. There were more vessel-associated, but not more parenchymal, TUNEL+ cells in HIVE cases as compared to controls. Vessel-associated TUNEL+ cells were primarily endothelial cells (von Willebrand factor+) or macrophages (CD68+). TUNEL+/CD68+ cells were present in both control and HIVE cases in similar frequencies (2.1 +/- 0.7% vs. 1.9 +/- 0.7% of total CD68+ populations, respectively). In HIVE, TUNEL+/p24+ cells were 0.4 +/- 0.2% of the total p24+ cell population, which was lower than the frequency of TUNEL+/CD68+ cells (1.9 +/- 0.7%) in the total CD68+ macrophage population. These results suggest that HIV-1-infected macrophages and microglia are resistant to apoptosis, and may contribute to the formation of a central nervous system viral reservoir.

An update on the neuropathology of HIV in the HAART era

This review compares the neuropathology of highly active antiretroviral therapy (HAART)-treated HIV+ individuals with the reported central nervous system (CNS) findings from the pre-HAART era. HAART has had considerable success in combating HIV-related immune collapse and has prevented many of the former end-stage complications of AIDS. However, with increased survival times the prevalence of minor HIV-associated cognitive impairment appears to be rising among treated patients and this may be a particular risk for older individuals. HIV encephalitis (HIVE) is still prevalent in treated patients although attenuated forms of HIVE and CNS opportunistic disorders are also observed. Some subjects show very significant CNS lymphocytic infiltrates in the context of HAART-induced immune reconstitution. HIV-associated cognitive impairment correlates best with the increased presence of activated, though not necessarily infected, microglia and CNS macrophages. This suggests that indirect mechanisms of neuronal injury and loss occur in HIV/AIDS as a basis for dementia since neurones are not themselves productively infected. Research to elucidate the mechanisms of neuronal injury in HIV/AIDS may contribute to the understanding of CNS function not only in HAART-treated subjects but also in other neurodegenerative disorders.

Neuro-ophthalmological disorders in HIV infected subjects with neurological manifestations

AIMS

To determine the frequency and features of neuro-ophthalmological manifestations in neurologically symptomatic HIV infected patients and to assess whether or not the visual evoked potential (VEP) features in these patients differ from those of neurologically asymptomatic HIV infected patients.

METHODS

Neuro-ophthalmological evaluation was performed in 166 neurologically symptomatic confirmed HIV positive patients, of whom 75 with normal ophthalmological examination were further studied by means of VEPs. The VEPs values were compared to those obtained from 53 other confirmed HIV positive subjects with neither ophthalmological nor neurological manifestations, who served as a comparison group and to the references values of our laboratory.

RESULTS

An abnormal neuro-ophthalmological examination was noted in 99/166 patients (60%). Eye movement disorders were present in 99 patients (51%). Visual field defects were detected in 39% of the patients. Optic neuropathy was noted in 31%, papilloedema in 27% and ocular motor nerve palsies in 26% of the patients. Toxoplasmosis and cryptococcosis were the most frequent associated pathologies, though in some patients the HIV itself was the presumed cause. VEPs were abnormal in 57% and 42% of patients with and without neurological manifestations, respectively. Compared to asymptomatic patients, symptomatic patients had a significantly increased mean latency; however, both groups had significant increase in mean latency compared to reference values.

CONCLUSION

Neuro-ophthalmological manifestations are common in neurologically symptomatic HIV infected patients. Subclinical dysfunction in the visual pathways is a common phenomenon in both HIV infected patients with and without neurological symptoms, but neurologically symptomatic patients seem to have more damage in their visual pathways.

Movement disorders and AIDS: a review

Movement disorders are a potential neurologic complication of acquired immune deficiency syndrome (AIDS), and may sometimes represent the initial manifestation of HIV infection. Dopaminergic dysfunction and the predilection of HIV infection to affect subcortical structures are thought to underlie the development of movement disorders such as parkinsonism in AIDS patients. In this review, we will discuss the clinical presentations, etiology and treatment of the various AIDS-related hypokinetic and hyperkinetic movement disorders, such as parkinsonism, chorea, myoclonus and dystonia. This review will also summarize current concepts regarding the pathophysiology of parkinsonism in HIV infection.

Update on neuroimaging in infectious central nervous system disease

PURPOSE OF REVIEW

Neuroimaging constitutes an important component in the diagnosis of the underlying infectious agents in central nervous system infection. This review summarizes progress in the neuroimaging of infectious central nervous system disease since January 2003. It focuses on imaging of viral encephalitis, including that caused by exotic and emerging viruses, and on imaging in immunodeficient patients.

RECENT FINDINGS

Diffusion-weighted imaging has been shown to be superior to conventional magnetic resonance imaging for the detection of early signal abnormalities in herpes simplex virus encephalitis but also in enterovirus 71 encephalitis and in West Nile encephalitis. Several studies defined the pattern of magnetic resonance imaging signal changes in endemic diseases such as West Nile encephalitis, Murray Valley encephalitis, enterovirus 71 encephalitis and Japanese encephalitis, but also in encephalitides due to ubiquitous viruses such as measles virus and Lyssavirus (rabies). In patients with HIV infection, apparent diffusion coefficient ratios obtained by diffusion-weighted imaging were significantly greater in lesions due to Toxoplasma encephalitis than in primary central nervous system lymphomas.

SUMMARY

The diagnosis of unclear infectious central nervous system diseases remains a challenge. More recent magnetic resonance imaging techniques, such as diffusion-weighted imaging and magnetic resonance spectroscopy, provide additional helpful information. However, the mainstay of diagnosis remains the detection of viral DNA or serological markers of specific infectious agents within the cerebrospinal fluid.

Role of microglia in central nervous system infections

The nature of microglia fascinated many prominent researchers in the 19th and early 20th centuries, and in a classic treatise in 1932, Pio del Rio-Hortega formulated a number of concepts regarding the function of these resident macrophages of the brain parenchyma that remain relevant to this day. However, a renaissance of interest in microglia occurred toward the end of the 20th century, fueled by the recognition of their role in neuropathogenesis of infectious agents, such as human immunodeficiency virus type 1, and by what appears to be their participation in other neurodegenerative and neuroinflammatory disorders. During the same period, insights into the physiological and pathological properties of microglia were gained from in vivo and in vitro studies of neurotropic viruses, bacteria, fungi, parasites, and prions, which are reviewed in this article. New concepts that have emerged from these studies include the importance of cytokines and chemokines produced by activated microglia in neurodegenerative and neuroprotective processes and the elegant but astonishingly complex interactions between microglia, astrocytes, lymphocytes, and neurons that underlie these processes. It is proposed that an enhanced understanding of microglia will yield improved therapies of central nervous system infections, since such therapies are, by and large, sorely needed.

Human immunodeficiency virus type 1 infection of human brain-derived progenitor cells

Although cells of monocytic lineage are the primary source of human immunodeficiency virus type 1 (HIV-1) in the brain, other cell types in the central nervous system, including astrocytes, can harbor a latent or persistent HIV-1 infection. In the present study, we examined whether immature, multipotential human brain-derived progenitor cells (nestin positive) are also permissive for infection. When exposed to IIIB and NL4-3 strains of HIV-1, progenitor cells and progenitor-derived astrocytes became infected, with peak p24 levels of 100 to 500 pg/ml at 3 to 6 days postinfection. After 10 days, virus production was undetectable but could be stimulated by the addition of tumor necrosis factor alpha (TNF-alpha). To bypass limitations to receptor entry, we compared the fate of infection in these cell populations by transfection with the infectious HIV-1 clone, pNL4-3. Again, transfected progenitors and astrocytes produced virus for 7 days but diminished to low levels beyond 8 days posttransfection. During the nonproductive phase, TNF-alpha stimulated virus production from progenitors as late as 5 weeks posttransfection. Astrocytes produced 5- to 20-fold more infectious virus (27 ng of p24/10(6) cells) than progenitors at the peak of 3 days posttransfection. Differentiation of infected progenitors toward an astrocyte phenotype increased virus production to levels consistent with infected astrocytes, suggesting a phenotypic difference in viral replication. Using this cell culture system of multipotential human brain-derived progenitor cells, we provide evidence that progenitor cells may be a reservoir for HIV-1 in the brains of AIDS patients.

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.

Correlation of acute humoral response with brain virus burden and survival time in pig-tailed macaques infected with the neurovirulent simian immunodeficiency virus SIVsmmFGb

Infection of pig-tailed macaques with the simian immunodeficiency virus (SIV) isolate SIVsmmFGb frequently results in SIV encephalitis (SIVE) in addition to immunodeficiency and acquired immune deficiency syndrome. We used in situ hybridization to quantitate the number of SIV-infected cells in brain parenchyma, choroid plexus, and meninges from 17 macaques that developed acquired immune deficiency syndrome after infection with SIVsmmFGb. SIV-infected cells and histopathological lesions of SIVE were identified in 15 of 17 animals (88.2%), including 12 of 12 rapid progressors (RP) and 3 of 5 slow progressors (SP). The parenchymal virus burden was much greater in RP macaques than in the three SP macaques with SIVE (median values of 24.3 versus 0.3 infected cells/mm(2), respectively; P < 0.05). Viral load differences between RP and SP with SIVE were less marked in choroid plexus (29.6 versus 12.8 infected cells/mm(2), respectively) and meninges (133.0 versus 34.2 infected cells/mm(2), respectively). A significant negative correlation was observed between the magnitude of the anti-SIV antibody titer at 1 month after inoculation and brain virus burden at necropsy (r = -0.614; P < 0.01). The close association between immune response and SIVE in this model should prove useful for identifying correlates of immune protection against primate lentiviral encephalitis.

Changing incidence of central nervous system diseases in the EuroSIDA cohort

A drastic decrease in incidence has been observed for most human immunodeficiency virus (HIV)-related opportunistic manifestations after use of highly active antiretroviral therapy (HAART). We assessed the trend of incidence of central nervous system (CNS) diseases in a prospective multicenter observational study involving 9,803 patients across Europe in the period 1994 to 2002 and analyzed patient and treatment variables associated with these conditions. Overall, 568 patients (5.8%) received a diagnosis of a new CNS disease. Incidence decreased significantly from 5.9 per 100 person-year in 1994 to 0.5 in 2002. Overall, the decrease was 40% per calendar year, and it was similar to that of non-CNS diseases and less evident after year 1998. In multivariable models, low CD4 cell count and high plasma viral load, but not HAART or calendar year, were significantly associated with risk to develop CNS disease, indicating that the effect of HAART was likely mediated by both improved immunological conditions and inhibition of viral replication. In contrast, use of nucleoside reverse transcriptase inhibitors, irrespective of use of protease inhibitors or non-nucleoside reverse transcriptase inhibitors, appeared to protect specifically against acquired immunodeficiency disease syndrome dementia complex, suggesting that, in this condition, therapy might have a direct, additive effect in the CNS.

Mononuclear phagocyte immunity and the neuropathogenesis of HIV-1 infection

Human immunodeficiency virus type 1 (HIV-1)-associated dementia is a neuroinflammatory brain disorder that is fueled by viral infection and immune activation of brain mononuclear phagocytes (MP; macrophages and microglia). MP serve as a reservoir for persistent viral infection, a vehicle for viral dissemination throughout the brain, and a major source of neurotoxic products that when produced in abundance, affect neuronal function. Such neurotoxic substances secreted by MP lead to clinical neurological impairment (cognitive, behavior, and motor abnormalities), which occurs usually years after the initial viral infection. How HIV-1 evades the immune function characteristic for MP as a first line of defense, including phagocytosis and intracellular killing, is not well understood despite more than two decades of study. In this report, we review the complex role(s) played by MP in the neuropathogenesis of HIV-1 infection. The clinical manifestations, pathology and pathogenesis, and treatment options are discussed in relationship to innate and adaptive immunity. Particular emphasis is given to the diversity of MP functions and how it may affect the disease process and manifestations. New insights into disease mechanisms are provided by advances in enhanced magnetic resonance imaging and proteomics to identify cell movement and genetic profiles of disease. New therapeutic strategies are discussed based on current knowledge of HIV-1-associated dementia pathogenesis.

Methamphetamine dependence increases risk of neuropsychological impairment in HIV infected persons

Both HIV infection and methamphetamine dependence can be associated with brain dysfunction. Little is known, however, about the cognitive effects of concurrent HIV infection and methamphetamine dependence. The present study included 200 participants in 4 groups: HIV infected/methamphetamine dependent (HIV+/METH+), HIV negative/methamphetamine dependent (HIV-/METH+), HIV infected/methamphetamine nondependent (HIV+/METH-), and HIV negative/methamphetamine nondependent (HIV-/METH-). Study groups were comparable for age, education, and ethnicity, although the HIV-/METH- group had significantly more females. A comprehensive, demographically corrected neuropsychological battery was administered yielding a global performance score and scores for seven neurobehavioral domains. Rates of neuropsychological impairment were determined by cutoff scores derived from performances of a separate control group and validated with larger samples of HIV+ and HIV- participants from an independent cohort. Rates of global neuropsychological impairment were higher in the HIV+/METH+ (58%), HIV-/METH+ (40%) and HIV+/METH- (38%) groups compared to the HIV-/METH- (18%) group. Nonparametric analyses revealed a significant monotonic trend for global cognitive status across groups, with least impairment in the control group and highest prevalence of impairment in the group with concurrent HIV infection and methamphetamine dependence. The results indicate that HIV infection and methamphetamine dependence are each associated with neuropsychological deficits, and suggest that these factors in combination are associated with additive deleterious cognitive effects. This additivity may reflect common pathways to neural injury involving both cytotoxic and apoptotic mechanisms.

HIV-1 and IL-1 beta regulate Fas ligand expression in human astrocytes through the NF-kappa B pathway

Reactive astrogliosis is a prominent pathological feature of HIV-1-associated dementia (HAD). We hypothesized that in HAD, astrocytes activated with proinflammatory stimuli such as IL-1beta express Fas ligand (FasL), a death protein. IL-1beta and HIV-1-activated astrocytes expressed FasL mRNA and protein. Luciferase reporter constructs showed that IL-1beta and HIV-1 upregulated FasL promoter activity (p<0.001). The NF-kappaB pathway was involved as shown by inhibition with SN50 and dominant negative IkappaBalpha mutants. Brain extracts from HAD patients had significantly elevated FasL levels compared to HIV-seropositive (p<0.001) and seronegative individuals (p<0.01). We propose that astrocyte expression of FasL may participate in neuronal injury in HAD.

Progressive multifocal leukoencephalopathy in acquired immunodeficiency syndrome: explaining the high incidence and disproportionate frequency of the illness relative to other immunosuppressive conditions

In the era of the AIDS pandemic, progressive multifocal leukoencephalopathy (PML) has ceased being a rare disease. Prevalence estimates from clinical and pathological series suggest that up to 5% of all HIV-infected persons will develop PML. The extraordinary frequency with which PML attends HIV infection vastly exceeds its appearance in association with other predisposing conditions and has resulted in it no longer being considered a rare disorder. Why PML appears to be far more common with AIDS than with other underlying immunosuppressive conditions remains unexplained. Potential explanations include an alteration of the CNS milieu by HIV facilitating JC viral entry into the brain and activation of the JCV by HIV proteins, e.g., tat, and by inflammatory byproducts of HIV infection. It is quite likely that multiple diverse mechanisms are at play.

The changing pattern of HIV neuropathology in the HAART era

Highly active antiretroviral treatment (HAART), which has been available for most AIDS patients in France since 1996, has resulted in a dramatic improvement of the progression of the disease. From the survey of our series of 343 brains with acquired immunodeficiency syndrome (AIDS) from patients who died between 1985 and 2002, we found both quantitative and qualitative changes in the pattern of human immunodeficiency virus (HIV) neuropathology. Quantitatively, despite a dramatic decrease in the number of autopsies, brain involvement remained a major cause of death. There was an overall decrease in incidence of cerebral toxoplasmosis, cytomegalovirus encephalitis (CMVE), and HIV encephalitis (HIVE), for which successful treatment is available. This contrasted with the unchanged incidence of progressive multifocal leukoencephalopathy (PML) and malignant non-Hodgkin lymphomas (MNHL). However, when looking closer at the 3 last years, the incidence of diseases affecting patients with severe immunodepression (CMVE, PML, and MNHL) decreased between 2000 and 2002, whereas infections occurring in patients with milder immunodeficiency, toxoplasmosis, varicella-zoster encephalitis (VZVE), or herpes simplex virus encephalitis (HSVE) became more frequent. In addition, we found uncommon types of brain infection such as BK virus encephalitis or general paresis. Finally, we described new variants of HIVE: severe leukoencephalopathy with intense perivascular macrophage and lymphocyte infiltration, possibly due to an exaggerated response from a newly reconstituted immune system, and chronic "burnt out" forms of HIVE as VZVE, toxoplasmosis, or PML, possibly associated with prolonged survival, in which neither inflammation nor organisms could be detected. These findings are compared with those reported in other neuropathological studies from different developed countries.

Polyomavirus JCV excretion and genotype analysis in HIV-infected patients receiving highly active antiretroviral therapy

OBJECTIVE

To assess the frequency of shedding of polyomavirus JC virus (JCV) genotypes in urine of HIV-infected patients receiving highly active antiretroviral therapy (HAART).

METHODS

Single samples of urine and blood were collected prospectively from 70 adult HIV-infected patients and 68 uninfected volunteers. Inclusion criteria for HIV-infected patients included an HIV RNA viral load < 1000 copies, CD4 cell count of 200-700 x 106 cells/l, and stable HAART regimen. PCR assays and sequence analysis were carried out using JCV-specific primers against different regions of the virus genome.

RESULTS

JCV excretion in urine was more common in HIV-positive patients but not significantly different from that of the HIV-negative group [22/70 (31%) versus 13/68 (19%); P = 0.09]. HIV-positive patients lost the age-related pattern of JCV shedding (P = 0.13) displayed by uninfected subjects (P = 0.01). Among HIV-infected patients significant differences in JCV shedding were related to CD4 cell counts (P = 0.03). Sequence analysis of the JCV regulatory region from both HIV-infected patients and uninfected volunteers revealed all to be JCV archetypal strains. JCV genotypes 1 (36%) and 4 (36%) were the most common among HIV-infected patients, whereas type 2 (77%) was the most frequently detected among HIV-uninfected volunteers.

CONCLUSION

These results suggest that JCV shedding is enhanced by modest depressions in immune function during HIV infection. JCV shedding occurred in younger HIV-positive persons than in the healthy controls. As the common types of JCV excreted varied among ethnic groups, JCV genotypes associated with progressive multifocal leukoencephalopathy may reflect demographics of those infected patient populations.

Pathogenesis of human immunodeficiency virus-induced neurological disease

Infection of the central nervous system by the type 1 human immunodeficiency virus (HIV-1) commonly results in a number of neurological impairments known, in their most severe form, as HIV-associated dementia (HAD). The persistence of HIV encephalitis (HIVE), the pathological correlate of HAD, in spite of highly active antiretroviral therapy (HAART) underscores the importance of continued research focused on the neurobiology of HIV. To elucidate direct and indirect mechanisms of HIV neuropathogenesis, current investigation is focused on neuroinvasion, HIV-1-mediated mechanisms of neuronal damage and apoptosis, and compartmentalized evolution of virus in the brain. The aim of this review is to provide a selective overview of the most recent research on the neurobiology of HIV, adding only a brief introduction regarding established principles.

Neurologic aspects of HIV infection in infants and children: therapeutic approaches and outcome

Central nervous system (CNS) HIV-related disorders frequently have devastating consequences. Significant progress has been made in the early diagnosis and treatment of the HIV-infected patient. As a result, the prevalence and natural history of neurologic illnesses have changed. This paper reviews the epidemiology, clinical manifestations, and neuropathogenesis of HIV-related CNS disorders. Advances in antiretroviral therapy, neuroprophylaxis, and neuroprotective strategies are also discussed.

Medication-induced peripheral neuropathy

Although not very common, medication-induced neuropathy is a treatable condition and, therefore, is important to identify. Medications continue to grow in number and expand in usage; consequently, toxic neuropathy continues to be relevant to neurologists. Many agents have toxicities that are tolerated because the treatments are necessary, such as therapies for HIV and malignancy. Additional agents to prevent or ameliorate the toxic neuropathy are being sought and trials are ongoing. Certain patients, however, may be at high risk for peripheral nerve toxicity due to genetic factors or another underlying neuropathy. Newer drug-delivery methods, such as viral transfection, may produce less toxicity in the future. The underlying pathomechanisms remain incompletely elucidated; however, apoptosis is emerging as an important final pathway in some forms of toxic neuropathy. Although most cases demonstrate acute or subacute onset after exposure, recent experiences with statin drugs raise the possibility of occult toxic causes of chronic idiopathic neuropathy.

HIV-related movement disorders: epidemiology, pathogenesis and management

Clinically relevant movement disorders are identified in 3% of patients with HIV infection seen at tertiary referral centres. In the same setting, prospective follow-up shows that 50% of patients with AIDS develop tremor, parkinsonism or other extrapyramidal features. Hemiballism-hemichorea and tremor are the most common hyperkinesias seen in patients who are HIV positive, but other movement disorders diagnosed in these patients include dystonia, chorea, myoclonus, tics, paroxysmal dyskinesias and parkinsonism. Patients with movement disorders usually present with other clinical features such as peripheral neuropathy, seizures, myelopathy and dementia. In the vast majority of patients, hyperkinesias result from lesions caused by opportunistic infections, particularly toxoplasmosis, which damage the basal ganglia connections. On the other hand, parkinsonism and tremor can result from dopaminergic dysfunction resulting from HIV itself or the use of antidopaminergic drugs. The management of patients who are HIV positive who present with movement disorders involves recognition and treatment of opportunistic infections, symptomatic treatment of the movement disorder and the use of highly active antiretroviral therapy (HAART). The most effective treatment of cerebral toxoplasmosis in patients with HIV infection is the combination of sulfadiazine and pyrimethamine. Symptomatic treatment of the movement disorder is often disappointing: hemiballism improves with antipsychotics, but tremor, parkinsonism and other phenomena usually fail to respond to available therapies. Preliminary data suggest that HAART may be helpful in the symptomatic control as well as prevention of movement disorders in patients who are HIV positive.

HIV and the central nervous system

Neurological complications of HIV infection are common with clinically recognized disorders ultimately affecting between 40% and 75% of patients. The spectrum of neurological disease is broad. This article highlights the common disorders of the central nervous system associated with HIV/AIDS.

CNS manifestations of cytomegalovirus infections: diagnosis and treatment

Cytomegalovirus (CMV) infection of the CNS occurs most commonly in patients with severe immunosuppression such as those with advanced HIV infection (i.e. AIDS) or those who have undergone bone marrow or solid organ transplantation. Immunocompetent patients are affected very rarely. The infection of the CNS may affect the brain (diffuse encephalitis, ventriculoencephalitis, cerebral mass lesions) or the spinal cord (transverse myelitis, polyradiculomyelitis). Diagnosis is very difficult and should be based on clinical presentation, results of imaging and virological markers. The most specific diagnostic tool is the detection of CMV DNA by polymerase chain reaction in the CSF. Treatment should be initiated promptly if CMV infection is suspected. Antiviral therapy consists of intravenous ganciclovir, intravenous foscarnet or a combination of both. Cidofovir is the treatment of second choice. Patients who experience clinical improvement or stabilisation during induction therapy should be given maintenance therapy. After immune reconstitution (in HIV-positive patients) or discontinuation of immunosuppressive therapy (in transplant recipients), maintenance therapy may be stopped. Despite therapy, the prognosis for long-term survival is very poor, especially in patients with AIDS.

HIV-related morbidity and mortality in patients starting protease inhibitors in very advanced HIV disease (CD4 count of < 50 cells/microL): an analysis of 338 clinical events from a randomized clinical trial

BACKGROUND

AIDS defining events occur infrequently in the presence of CD4 counts above 200 cells/microL. It is, however, uncertain for most of the AIDS defining conditions whether this threshold can be considered equally safe in patients with a previously very low CD4 nadir.

METHODS

We evaluated in detail all the AIDS defining events observed during a 48-week clinical trial in 1251 nucleoside reverse transcriptase inhibitor-experienced patients who started protease inhibitors (PIs) at CD4 counts below 50 cells/microL. The type of event, immunological status at the moment of event and time between start of PI treatment and event occurrence were analysed cumulatively and by event type; event rates were calculated.

RESULTS

Concomitant data on CD4 counts were available for 338 AIDS defining events (81% of total events). Median time between start of treatment with PI and event was 94.5 days and median absolute CD4 value at the occurrence of event was 20 per microL. Only 14 events (in 12 patients) were observed above the threshold of 200 CD4 cells/microL. An analysis of the 67 deaths with concomitantly available CD4 counts (57%) showed a median CD4 count of 10 cells/microL, with only four deaths occurring in the presence of a CD4 count above 100 cells/microL.

CONCLUSIONS

Very few clinical AIDS defining conditions were observed in patients who start PIs at very low CD4 counts and with treatment restore absolute values in CD4 counts above 200 cells/microL. This threshold can therefore be considered a clinically effective goal of treatment with respect to occurrence of all AIDS defining conditions in patients starting PIs in very advanced HIV disease.

Impaired spatial cognition and synaptic potentiation in a murine model of human immunodeficiency virus type 1 encephalitis

Injection of human immunodeficiency virus type 1 (HIV-1)-infected human monocyte-derived macrophages (MDMs) into the basal ganglia of severe combined immunodeficient mice recapitulates histopathologic features of HIV-1 encephalitis (HIVE). Here, we show that the neural damage in HIVE mice extends beyond the basal ganglia and is associated with cognitive impairment. Morris water maze tests showed impaired spatial learning 8 d after MDM injection. Moreover, impaired synaptic potentiation in the hippocampal CA1 subregion was demonstrated at 8 and 15 d. By day 15, post-tetanic, short-term, and long-term potentiation were reduced by 14.1, 29.5, and 45.3% in HIVE mice compared with sham-injected or control animals. Neurofilament (NF) and synaptophysin (SP) antigens were decreased significantly in the CA2 hippocampal subregion of HIVE mice with limited neuronal apoptosis. By day 15, the CA2 region of HIVE mice expressed 3.8- and 2.6-fold less NF and SP than shams. These findings support the notion that HIV-1-infected and immune-competent brain macrophages can cause neuronal damage at distant anatomic sites. Importantly, the findings demonstrate the value of the model in exploring the physiological basis and therapeutic potential for HIV-1-associated dementia.

Impaired spatial cognition and synaptic potentiation in a murine model of human immunodeficiency virus type 1 encephalitis

Injection of human immunodeficiency virus type 1 (HIV-1)-infected human monocyte-derived macrophages (MDMs) into the basal ganglia of severe combined immunodeficient mice recapitulates histopathologic features of HIV-1 encephalitis (HIVE). Here, we show that the neural damage in HIVE mice extends beyond the basal ganglia and is associated with cognitive impairment. Morris water maze tests showed impaired spatial learning 8 d after MDM injection. Moreover, impaired synaptic potentiation in the hippocampal CA1 subregion was demonstrated at 8 and 15 d. By day 15, post-tetanic, short-term, and long-term potentiation were reduced by 14.1, 29.5, and 45.3% in HIVE mice compared with sham-injected or control animals. Neurofilament (NF) and synaptophysin (SP) antigens were decreased significantly in the CA2 hippocampal subregion of HIVE mice with limited neuronal apoptosis. By day 15, the CA2 region of HIVE mice expressed 3.8- and 2.6-fold less NF and SP than shams. These findings support the notion that HIV-1-infected and immune-competent brain macrophages can cause neuronal damage at distant anatomic sites. Importantly, the findings demonstrate the value of the model in exploring the physiological basis and therapeutic potential for HIV-1-associated dementia.

HIV-1 and the brain: connections between HIV-1-associated dementia, neuropathology and neuroimmunology

AIDS patients frequently exhibit neurological disorders due to the neurotoxic events that result from HIV-1 and/or opportunistic infections in the brain. This review examines recent clinical findings related to HIV-1-associated dementia, and outlines current areas of basic research that may clarify how HIV-1-associated encephalopathy produces clinical symptoms of brain dysfunction.

Central nervous system infection during immunosuppression

Suppression of the immune system by human immunodeficiency virus (HIV) infection or immunosuppressive therapy following transplantation increases susceptibility to CNS infection. Examination of the level and type of immunosuppression, in addition to the clinical and radiologic findings at the time of diagnosis can aid the clinician in determining the most likely etiology of infection. This article discusses how suppression of the host immune status modifies the presentation and diagnosis of selected CNS infections and the recommended treatment for these infections.

Pulmonary manifestations of HIV infection in the era of highly active antiretroviral therapy

STUDY OBJECTIVES

To determine whether the spectrum of HIV-related pulmonary disease seen by a university medical center Pulmonary and Critical Care Medicine Service has changed since the introduction of highly active antiretroviral therapy (HAART).

DESIGN

Retrospective chart review.

SETTING

A tertiary care university hospital.

PATIENTS

All HIV-infected patients referred to the Pulmonary and Critical Care Medicine Service from January 1, 1993, through December 31, 1995 (era 1) and from July 1, 1997, through June 30, 2000 (era 2).

INTERVENTIONS

Inpatient and outpatient charts were reviewed for data regarding patient demographics, CD4 cell counts, viral load levels, duration of HIV seropositivity, history of opportunistic infections, and final diagnosis.

RESULTS

Pneumocystis carinii pneumonia (PCP) was less common in the HAART era than in the pre-HAART era, whereas bacterial pneumonia and non-Hodgkin's lymphoma (NHL) were more common in the HAART era than in the pre-HAART era. HAART was protective against PCP (odds ratio [OR], 0.37; confidence interval [CI], 0.16 to 0.89) in a manner dependent on the CD4 cell count. Patients receiving HAART were at increased risk for the development of bacterial pneumonia (OR, 2.41; CI, 1.12 to 5.17) and NHL (OR, 15.11; CI, 3.14 to 28.32). A history of PCP indicated a risk factor for bacterial pneumonia (OR, 2.14; CI, 1.13 to 4.04). A history of cytomegalovirus infection indicated a risk factor for NHL (OR, 6.0; CI, 1.27 to 28.32).

CONCLUSIONS

There have been significant changes in the spectrum of HIV-related pulmonary complications seen by our Pulmonary and Critical Care Medicine Service in the HAART era.

Improvement of anemia among HIV-infected injection drug users receiving highly active antiretroviral therapy

Although anemia is common during HIV infection, it is unclear whether potent antiretroviral therapy would improve or worsen anemia. We conducted a study to examine the impact of highly active antiretroviral therapy (HAART) on anemia in a cohort of HIV-positive injection drug users (IDUs) in Baltimore, Maryland. At baseline, the overall prevalence of anemia was 40%. During mean follow-up of one year, among 102 subjects who received HAART, there was a mean increase in hemoglobin of 3.6 +/- 1.7 g/L (p =.0003) [corrected] and a mean decrease in log(10) plasma HIV load of 0.25 +/- 0.06 copies/ml (p <.0002) [corrected]. Among 103 control subjects who were not receiving antiretroviral medications, there was a mean decrease in hemoglobin of 4.2 +/- 1.1 g/L (p <.04) [corrected] and mean increase in log(10) plasma HIV load of 0.78 +/- 0.17 copies/ml (p <.0001) [corrected]. Multivariate analysis using mixed linear models showed that HAART was associated with an increase of hemoglobin of 0.223 g/L per month (p <.0001) after adjusting for body mass index, opportunistic infections, and gender. HAART was associated with an improvement in anemia, and potential mechanisms that may be involved include a reduction in opportunistic infections and the anemia of chronic disease and an improvement in nutritional status.

Peripheral neuropathy and antiretroviral drugs

Patients treated with nucleoside analogue reverse transcriptase inhibitors (NRTIs) develop a varying degree of myopathy or neuropathy after long-term therapy. Zidovudine (AZT) causes myopathy; zalcitabine (ddC), didanosine (ddl) and lamuvidine (3TC) cause neuropathy; stavudine (d4T) and fialuridine (FIAU) cause neuropathy or myopathy and lactic acidosis. The tissue distribution of phosphorylases responsible for phosphorylation of NRTIs relates to their selective tissue toxicity. The myopathy is characterized by muscle wasting, myalgia, fatigue, weakness and elevation of CK. The neuropathy is painful, sensory and axonal. In vitro, NRTIs inhibit the gamma-DNA polymerase, responsible for replication of mtDNA, and cause mtDNA dysfunction. In vivo, patients treated with AZT, the best studied NRTI, develop a mitochondrial myopathy with mtDNA depletion, deficiency of COX (complex IV), intracellular fat accumulation, high lactate production and marked phosphocreatine depletion, as determined with in vivo MRS spectroscopy, due to impaired oxidative phosphorylation. Animals or cultured cells treated with NRTIs develop neuropathy, myopathy, or cell destruction with similar changes in the mitochondria. There is evidence that the NRTI-related neuropathy is also due to mitochondrial toxicity. The NRTIs (AZT, ddC, ddl, d4T, 3TC) contain azido groups that compete with natural thymidine triphosphate as substrates of DNA pol-gamma and terminate mtDNA synthesis. In contrast, FIAU that contains 3'-OH groups serves as an alternate substrate for thymidine triphosphate with DNA pol-gamma and is incorporated into the DNA causing permanent mtDNA dysfunction. The NRTI-induced mitochondrial dysfunction has an influence on the clinical application of these agents, especially at high doses and when combined. They have produced in humans a new category of acquired mitochondrial toxins that cause clinical manifestations resembling the genetic mitochondrial disorders.

Epidemiology and clinical features of HIV-1 associated neuropathies

Peripheral neuropathy is common in human immunodeficiency virus type-1 (HIV-1) infection. Peripheral neuropathies complicate all stages of the HIV-1 disease and cause considerable morbidity and disability in HIV-1 infected individuals and acquired immunodeficiency syndrome (AIDS) patients. Whereas symptomatic neuropathies occur in approximately 10% to 15% of HIV-1-infected patients overall, pathologic evidence of peripheral nerve involvement is present in virtually all end-stage AIDS patients. There are 6 major clinical types of HIV-associated neuropathies that are regularly seen in large HIV-1 clinics. Distal sensory polyneuropathy (DSP) is the most common among the HIV-1-associated neuropathies. DSP generally occurs in later stages of HIV-1 infection and it follows an indolent and protracted clinical course. The dominant clinical features in DSP include distal pain, paresthesia and numbness in a typical length-dependent fashion with proximal to distal gradient. Whereas toxic neuropathies--secondary to certain antiretroviral agents--are clinically similar to DSP, their temporal relation to neurotoxic medication helps distinguish them from other HIV-1-associated neuropathies. DSP and toxic neuropathy may coexist in a single patient. Acute and chronic inflammatory demyelinating polyradiculoneuropathies (AIDP and CIDP) produce global limb weakness. AIDP may occur at seroconversion and it can therefore be the initial manifestation of HIV-1 infection. CIDP generally occurs in the mid to late stages of HIV-1 infection. Progressive polyradiculopathy (PP) occurs in patients with advanced immunodeficiency and is generally caused by the opportunist cytomegalovirus (CMV) infection. Mononeuropathy multiplex (MM) in early stages of HIV-1 infection is immune mediated, whereas in advanced AIDS it is caused by the CMV infection. Finally, subclinical autonomic nervous system involvement is common in all stages of HIV-1 infection. Because HIV-1-associated neuropathies are diverse in their etiology and pathogenesis, a precise clinical diagnosis is required to formulate a rational therapeutic intervention.