Neurological complications of HIV infection

HIV-associated neurological disorders: a guide to pharmacotherapy

In the era of highly active antiretroviral therapy (HAART), HIV-1-associated neurocognitive disorder (HAND) continues to be a common and significant morbidity among individuals infected with HIV. The term HAND encompasses a spectrum of progressively severe CNS involvement, ranging from asymptomatic neurocognitive impairment and minor neurocognitive disorder through to the most severe form of HIV-associated dementia (HAD). While the incidence of HAD has declined significantly with HAART, the milder forms of HAND persist. In addition, HAND now develops in individuals with less advanced immunosuppression. The reasons for the persistence of milder forms of HAND in individuals treated with HAART are not entirely known. There are several hypotheses to explain this phenomenon that include the legacy effect, a failure of antiretroviral agents to reverse neurological damage, poor access of antiretroviral agents to the CNS, chronic systemic immune activation associated with microbial translocation products, sustained CNS inflammation, the improved survival of HIV-seropositive individuals and the possible contribution from aging, amyloid deposition and other co-morbidities. In contrast, the incidence of HIV-associated CNS opportunistic processes including progressive multifocal leukoencephalopathy, tuberculosis, CNS toxoplasmosis, cytomegalovirus encephalitis, cryptococcosis and primary CNS lymphoma has declined dramatically with the introduction of HAART. This review briefly summarizes our current understanding of HAND and the pathological mechanisms involved, namely direct injury from HIV-1 and viral proteins, indirect neurotoxicity from proinflammatory cytokines and chronic, sustained immune activation in the CNS. To date, only HAART has been shown to benefit HAND despite numerous controlled trials of adjunctive 'anti-inflammatory' agents. Although HAART has a profound impact on the incidence and severity of HAND, there exists a 'therapeutic gap' as even HAART that is effective at inducing durable virological suppression may only partially reverse HAND. In addition, there may be potential CNS adverse effects of antiretroviral agents. There is an ongoing multicentre clinical trial to investigate the role of the CNS Penetration-Effectiveness index, an indicator of drug permeability and availability in the CNS, to help guide the choice of antiretroviral agents in the treatment of HAND. With recent recommendations for earlier treatment intervention with HAART for HIV-1 infection, it remains to be seen the effects of this on HAND. There is an urgent need to better define the therapeutic guidelines for the prevention and treatment of HAND.

Blood-brain barrier abnormalities caused by HIV-1 gp120: mechanistic and therapeutic implications

The blood-brain barrier (BBB) is compromised in many systemic and CNS diseases, including HIV-1 infection of the brain. We studied BBB disruption caused by HIV-1 envelope glycoprotein 120 (gp120) as a model. Exposure to gp120, whether acute [by direct intra-caudate-putamen (CP) injection] or chronic [using SV(gp120), an experimental model of ongoing production of gp120] disrupted the BBB, and led to leakage of vascular contents. Gp120 was directly toxic to brain endothelial cells. Abnormalities of the BBB reflect the activity of matrix metalloproteinases (MMPs). These target laminin and attack the tight junctions between endothelial cells and BBB basal laminae. MMP-2 and MMP-9 were upregulated following gp120-injection. Gp120 reduced laminin and tight junction proteins. Reactive oxygen species (ROS) activate MMPs. Injecting gp120 induced lipid peroxidation. Gene transfer of antioxidant enzymes protected against gp120-induced BBB abnormalities. NMDA upregulates the proform of MMP-9. Using the NMDA receptor (NMDAR-1) inhibitor, memantine, we observed partial protection from gp120-induced BBB injury. Thus, (1) HIV-envelope gp120 disrupts the BBB; (2) this occurs via lesions in brain microvessels, MMP activation and degradation of vascular basement membrane and vascular tight junctions; (3) NMDAR-1 activation plays a role in this BBB injury; and (4) antioxidant gene delivery as well as NMDAR-1 antagonists may protect the BBB.

Study of compartmentalization in the visna clinical form of small ruminant lentivirus infection in sheep

BACKGROUND

A central nervous system (CNS) disease outbreak caused by small ruminant lentiviruses (SRLV) has triggered interest in Spain due to the rapid onset of clinical signs and relevant production losses. In a previous study on this outbreak, the role of LTR in tropism was unclear and env encoded sequences, likely involved in tropism, were not investigated. This study aimed to analyze heterogeneity of SRLV Env regions--TM amino terminal and SU V4, C4 and V5 segments--in order to assess virus compartmentalization in CNS.

RESULTS

Eight Visna (neurologically) affected sheep of the outbreak were used. Of the 350 clones obtained after PCR amplification, 142 corresponded to CNS samples (spinal cord and choroid plexus) and the remaining to mammary gland, blood cells, bronchoalveolar lavage cells and/or lung. The diversity of the env sequences from CNS was 11.1-16.1% between animals and 0.35-11.6% within each animal, except in one animal presenting two sequence types (30% diversity) in the CNS (one grouping with those of the outbreak), indicative of CNS virus sequence heterogeneity. Outbreak sequences were of genotype A, clustering per animal and compartmentalizing in the animal tissues. No CNS specific signature patterns were found.

CONCLUSIONS

Bayesian approach inferences suggested that proviruses from broncoalveolar lavage cells and peripheral blood mononuclear cells represented the common ancestors (infecting viruses) in the animal and that neuroinvasion in the outbreak involved microevolution after initial infection with an A-type strain. This study demonstrates virus compartmentalization in the CNS and other body tissues in sheep presenting the neurological form of SRLV infection.

Neuromuscular complications in HIV: effects of aging

There has been speculation that chronic HIV infection is a condition of accelerated aging that may lead to early onset of disease in multiple organ systems. The neuromuscular disorders of HIV, in particular distal symmetric polyneuropathy and myopathies, are also seen in the general population among older patients. As the HIV-infected population ages, there may be deleterious synergistic effects of age and chronic HIV infection on the brain, peripheral nerve, and muscle. In this review, we explore commonalities between the clinical features and putative mechanisms of neuromuscular disorders and HIV.

Early minocycline treatment prevents a decrease in striatal dopamine in an SIV model of HIV-associated neurological disease

HIV-infected individuals, even with antiretroviral therapy, often display cognitive, behavioral and motor abnormalities and have decreased dopamine (DA) levels. Minocycline prevents encephalitis and neurodegeneration in SIV models, suggesting that it might also protect against nigrostriatal dopaminergic system dysfunction. Using an SIV/macaque model of HIV-associated CNS disease, we demonstrated that striatal levels of DA were significantly lower in macaques late in infection and that levels of the metabolite DOPAC also tended to be lower. DA levels declined more than its metabolites, indicating a dysregulation of DA production or catabolism. Minocycline treatment beginning at 12 but not 21 days postinoculation prevented striatal DA loss. DA decline was not due to direct loss of dopaminergic projections to the basal ganglia as there was no difference in tyrosine hydroxylase, dopamine transporter, vesicular monoamine transporter 2 or synaptophysin between minocycline-treated and untreated macaques. SIV-infected macaques had significantly higher monoamine oxidase (MAO) activity than uninfected macaques, although MAO activity was not affected by minocycline. Oxidative/nitrosative stress was examined by nitrotyrosine staining in the deep white matter and was lower in SIV-infected, minocycline-treated macaques compared with untreated macaques. These data suggest that minocycline, which has antioxidant activity, has a protective effect on DA homeostasis when administered at an appropriate time in SIV neuropathogenesis.

Tolerability of NGX-4010, a capsaicin 8% patch for peripheral neuropathic pain

BACKGROUND/PURPOSE

NGX-4010 (QUTENZA(™); NeurogesX Inc, San Mateo, CA), a capsaicin 8% dermal patch, is licensed in the European Union for the treatment of peripheral neuropathic pain (PNP) in nondiabetic adults and in the United States for the treatment of neuropathic pain associated with postherpetic neuralgia (PHN). While NGX-4010 treatment is associated with a low risk of systemic adverse events, patch application-related pain is common and may be managed with local cooling and/or oral analgesics. This article characterizes the tolerability of NGX-4010 and will help to guide any pain management.

METHODS

This integrated analysis of tolerability data collected from the NGX-4010 clinical study program included 1696 patients with PNP. Patch application-related pain on the treatment day was captured as Numeric Pain Rating Scale (NPRS) "pain now" scores while "average pain for the past 24 hours" NPRS scores were analyzed for 7 days following treatment. Other tolerability assessments included the percentage of patients completing ≥90% of the intended treatment duration and patients using medication for patch application-related pain.

RESULTS

The mean maximum change in "pain now" NPRS scores from pretreatment levels during and after patch application was 2.6 for all patients. This pain was transient and resolved following patch removal. Mean "average pain for the past 24 hours" NPRS scores returned to baseline by the evening of the treatment day for patients with PHN, and the evening of day 2 for patients with human immunodeficiency virus-associated distal sensory polyneuropathy or painful diabetic neuropathy. Repeated NGX-4010 applications did not affect the intensity of patch application-related pain. Almost all patients (≥98%) completed ≥90% of the full treatment duration, regardless of the number of treatments received.

CONCLUSION

Transient patch application-related pain with NGX-4010 can be managed with local cooling and/or oral analgesics in nearly all cases. Patient adherence to the full intended treatment duration indicated that patch application-related pain was not a barrier to NGX-4010 use.

HIV-1 Tat neurotoxicity: a model of acute and chronic exposure, and neuroprotection by gene delivery of antioxidant enzymes

HIV-associated neurocognitive disorder (HAND) is an increasingly common, progressive disease characterized by neuronal loss and progressively deteriorating CNS function. HIV-1 gene products, particularly gp120 and Tat elicit reactive oxygen species (ROS) that lead to oxidant injury and cause neuron apoptosis. Understanding of, and developing therapies for, HAND requires accessible models of the disease. We have devised experimental approaches to studying the acute and chronic effects of Tat on the CNS. We studied acute exposure by injecting recombinant Tat protein into the caudate-putamen (CP). Ongoing Tat expression, which more closely mimics HIV-1 infection of the brain, was studied by delivering Tat-expression over time using an SV40-derived gene delivery vector, SV(Tat). Both acute and chronic Tat exposure induced lipid peroxidation and neuronal apoptosis. Finally, prior administration of recombinant SV40 vectors carrying antioxidant enzymes, copper/zinc superoxide dismutase (SOD1) or glutathione peroxidase (GPx1), protected from Tat-induced apoptosis and oxidative injury. Thus, injection of recombinant HIV-1 Tat and the expression vector, SV(Tat), into the rat CP cause respectively acute or ongoing apoptosis and oxidative stress in neurons and may represent useful animal models for studying the pathogenesis and, potentially, treatment of HIV-1 Tat-related damage.

Effects of highly active antiretroviral therapy on cognitive functions in severely immune-compromised HIV-seropositive patients

OBJECTIVE

This study assessed the effects of highly active antiretroviral therapy on the cognitive performances of HIV seropositive patients with severe immune depression.

METHODS

It is a prospective longitudinal interventional study of 69 anti-retroviral naïve HIV-seropositive adult patients with CD4 levels ≤ 350/μl. The cognitive assessment was done at initiation and 12 months after anti-retroviral treatment using the Community Screening Instrument for Dementia (CSID) and the computer-assisted Iron Psychology (FePsy). The impact of therapy on CD4 levels and cognitive scores of the patients before and after therapy were compared and tested for statistical significance using Student t test and one-way ANOVA.

RESULTS

The mean age of the patients was 36.6 ± 8.8 years. There was a significant increase in CD4 levels of the patients from 144.75 ± 88.92 at baseline to 295.91 ± 148.79 after 12 months of HAART (p<0.0001). There were significant improvements in their cognitive scores (p<0.05) in all cognitive domains tested but the finger tapping task (motor speed) did not show any improvement (p>0.05). Combination ARV drugs with efavirenz did not significantly improve attention and choice reaction time.

CONCLUSION

Highly active antiretroviral therapy significantly improved the CD4 levels and cognitive performances of treated HIV positive patients in all tested domains with the exception of motor speed.

HIV-1gp120 induces neuronal apoptosis through enhancement of 4-aminopyridine-senstive outward K+ currents

Human immunodeficiency virus type 1 (HIV-1)-associated dementia (HAD) usually occurs late in the course of HIV-1 infection and the mechanisms underlying HAD pathogenesis are not well understood. Accumulating evidence indicates that neuronal voltage-gated potassium (Kv) channels play an important role in memory processes and acquired neuronal channelopathies in HAD. To examine whether Kv channels are involved in HIV-1-associated neuronal injury, we studied the effects of HIV-1 glycoprotein 120 (gp120) on outward K+ currents in rat cortical neuronal cultures using whole-cell patch techniques. Exposure of cortical neurons to gp120 produced a dose-dependent enhancement of A-type transient outward K+ currents (IA). The gp120-induced increase of IA was attenuated by T140, a specific antagonist for chemokine receptor CXCR4, suggesting gp120 enhancement of neuronal IA via CXCR4. Pretreatment of neuronal cultures with a protein kinase C (PKC) inhibitor, GF109203X, inhibited the gp120-induced increase of IA. Biological significance of gp120 enhancement of IA was demonstrated by experimental results showing that gp120-induced neuronal apoptosis, as detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and caspase-3 staining, was attenuated by either an IA blocker 4-aminopyridine or a specific CXCR4 antagonist T140. Taken together, these results suggest that gp120 may induce caspase-3 dependent neuronal apoptosis by enhancing IA via CXCR4-PKC signaling.

Mass spectrometry based proteomic studies on viruses and hosts--a review

In terms of proteomic research in the 21st century, the realm of virology is still regarded as an enormous challenge mainly brought by three aspects, namely, studying on the complex proteome of the virus with unexpected variations, developing more accurate analytical techniques as well as understanding viral pathogenesis and virus-host interaction dynamics. Progresses in these areas will be helpful to vaccine design and antiviral drugs discovery. Mass spectrometry based proteomics have shown exceptional display of capabilities, not only precisely identifying viral and cellular proteins that are functionally, structurally, and dynamically changed upon virus infection, but also enabling us to detect important pathway proteins. In addition, many isolation and purification techniques and quantitative strategies in conjunction with MS can significantly improve the sensitivity of mass spectrometry for detecting low-abundant proteins, replenishing the stock of virus proteome and enlarging the protein-protein interaction maps. Nevertheless, only a small proportion of the infectious viruses in both of animal and plant have been studied using this approach. As more virus and host genomes are being sequenced, MS-based proteomics is becoming an indispensable tool for virology. In this paper, we provide a brief review of the current technologies and their applications in studying selected viruses and hosts.

Delineating HIV-associated neurocognitive disorders using transgenic models: the neuropathogenic actions of Vpr

HIV-associated neurocognitive disorders (HAND) represent a constellation of neurological disabilities defined by neuropsychological impairments, neurobehavioral abnormalities and motor deficits. To gain insights into the mechanisms underlying the development of these disabilities, several transgenic models have been developed over the past two decades, which have provided important information regarding the cellular and molecular factors contributing to the neuropathogenesis of HAND. Herein, we concentrate on the neuropathogenic effects of HIV-1 Vpr expressed under the control of c-fms, resulting transgene expression in myeloid cells in both the central and peripheral nervous systems. Vpr's actions, possibly through its impact on cell cycle machinery, in brain culminate in neuronal and astrocyte injury and death through apoptosis involving activation of caspases-3, -6 and -9 depending on the individual target cell type. Indeed, these outcomes are also induced by soluble Vpr implying Vpr's effects stem from direct interaction with target cells. Remarkably, in vivo transgenic Vpr expression induces a neurodegenerative phenotype defined by neurobehavioral deficits and neuronal loss in the absence of frank inflammation. Implantation of another viral protein, hepatitis C virus (HCV) core, into Vpr transgenic animals' brains stimulated neuroinflammation and amplified the neurodegenerative disease phenotype, thereby recapitulating HCV's putative neuropathogenic actions. The availability of different transgenic models to study HIV neuropathogenesis represents exciting and innovative approaches to understanding disease mechanisms and perhaps developing new therapeutic strategies in the future.

Macrophage-mediated dorsal root ganglion damage precedes altered nerve conduction in SIV-infected macaques

Peripheral neuropathy is the most common neurological complication of HIV-1 infection, affecting over one-third of infected individuals, including those treated with antiretroviral therapy. To study the pathogenesis of HIV-induced peripheral nervous system disease, we established a model in which SIV-infected macaques developed changes closely resembling alterations reported in components of the sensory pathway in HIV-infected individuals. Significant declines in epidermal nerve fiber density developed in SIV-infected macaques, similar to that of HIV-infected individuals with neuropathy. Changes in dorsal root ganglia (DRG) included macrophage infiltration, SIV replication in macrophages, immune activation of satellite cells, and neuronal loss. To determine whether dorsal root ganglion damage was associated with altered nerve function, we measured unmyelinated C-fiber conduction velocities (CV) in nerves of SIV-infected macaques and compared CV changes with DRG alterations. Twelve weeks postinoculation, SIV-infected macaques had significantly lower C-fiber conduction velocity in sural nerves than uninfected animals and the magnitude of conduction velocity decline correlated strongly with extent of DRG macrophage infiltration. Thus, injury to neurons in the DRG-mediated by activated macrophages-preceded altered conduction of unmyelinated nerve fibers in SIV-infected macaques, suggesting that macrophage-mediated DRG damage may be the initiating event in HIV-induced sensory neuropathy.

HIV-associated dementia in older adults: clinical and tomographic aspects

BACKGROUND

Elderly adults with human immunodeficiency virus (HIV) are at greater risk of developing cognitive impairment. The purpose of this study was to describe clinical and tomographic characteristics of HIV-1 associated dementia (HIVD) in older adults.

METHODS

A descriptive study was carried out involving eight HIVD patients. Seven tests were employed for cognitive assessment and transformed to whole number z-scores using appropriate normative sets.

RESULTS

The average age of the patients was 71 years; seven cases described the route of HIV infection as being heterosexual; and mean schooling was 6.5 years. Six subjects were using highly active anti-retroviral therapy (HAART), with an average CD4 count of 407.8 cells/mm3. Mild dementia was detected in most cases (87.5%). Deficits on neuropsychological tests showed results similar to multi-center transversal studies on HIVD. The classic HIVD triad observed in younger adults was also seen in this population: i.e. cognitive changes, psychiatric changes and motor impairment. Cortical injury shown by dyscalculia, visual-spatial change and language deficits were frequent. Brain images showed cortical atrophy in all patients but was restricted to frontal lobes in five cases.

CONCLUSION

The findings on brain imaging were non-specific, revealing images similar to those of the elderly brain and to HIVD in younger adults. HIVD in the elderly is a challenge and become an increasingly significant differential diagnosis for cognitive loss in old age. This dementia must be clinically suspected and image exams are useful in excluding other central disorders. Prospective studies of HIV-positive elderly people are warranted to better understand HIVD.

Recent clinical history and cognitive dysfunction for attention and executive function among human immunodeficiency virus-infected patients

This study examined the association between recent trends in CD4 and viral loads and cognitive test performance with the expectation that recent history could predict cognitive performance. Eighty-three human immunodeficiency virus (HIV)-infected patients with a mean CD4 count of 428 copies/ml were examined in this study (62% with undetectable plasma viral load [PVL]). We investigated the relationships between nadir CD4 cell count, 1-year trends in immunologic function/PVLs, and cognitive performance across several domains using linear regression models. Nadir CD4 cell count was predictive of current executive function (p = .004). One year clinical history for CD4 cell counts and/or PVLs were predictive of executive function, attention/working memory, and learning/memory measures (p < .05). Models that combined recent clinical history trends and nadir CD4 cell counts suggested that recent clinical trends were more important in predicting current cognitive performance for all domains except executive function. This research suggests that recent CD4 and viral load history is an important predictor of current cognitive function across several cognitive domains. If validated, clinical variables and cognitive dysfunction models may improve our understanding of the dynamic relationships between disease evolution and progression and CNS involvement.

Immunomodulatory properties of kappa opioids and synthetic cannabinoids in HIV-1 neuropathogenesis

Anti-retroviral therapy (ART) has had a tremendous impact on the clinical outcomes of HIV-1 infected individuals. While ART has produced many tangible benefits, chronic, long-term consequences of HIV infection have grown in importance. HIV-1-associated neurocognitive disorder (HAND) represents a collection of neurological syndromes that have a wide range of functional cognitive impairments. HAND remains a serious threat to AIDS patients, and there currently remains no specific therapy for the neurological manifestations of HIV-1. Based upon work in other models of neuroinflammation, kappa opioid receptors (KOR) and synthetic cannabinoids have emerged as having neuroprotective properties and the ability to dampen pro-inflammatory responses of glial cells; properties that may have a positive influence in HIV-1 neuropathogenesis. The ability of KOR ligands to inhibit HIV-1 production in human microglial cells and CD4 T lymphocytes, demonstrate neuroprotection, and dampen chemokine production in astrocytes provides encouraging data to suggest that KOR ligands may emerge as potential therapeutic agents in HIV neuropathogenesis. Based upon findings that synthetic cannabinoids inhibit HIV-1 expression in human microglia and suppress production of inflammatory mediators such as nitric oxide (NO) in human astrocytes, as well as a substantial literature demonstrating neuroprotective properties of cannabinoids in other systems, synthetic cannabinoids have also emerged as potential therapeutic agents in HIV neuropathogenesis. This review focuses on these two classes of compounds and describes the immunomodulatory and neuroprotective properties attributed to each in the context of HIV neuropathogenesis.

Non-traumatic myelopathy at the Chris Hani Baragwanath Hospital, South Africa--the influence of HIV

BACKGROUND

Non-traumatic myelopathy from developing regions has been described widely. In these regions infections, mainly tuberculosis, followed by acute transverse myelitis and neoplasms, dominate. These are also regions of high HIV prevalence. In developed regions, the most prominent reported spinal cord disease in HIV/AIDS is vacuolar myelopathy (VM). Other myelopathy causes in HIV/AIDS include opportunistic infections, neoplasms, vascular lesions and metabolic disease. In developing regions, opportunistic infections are more commonly encountered with VM occurring less frequently.

AIM

To determine the influence of HIV on the myelopathy spectrum in an HIV endemic region.

DESIGN

Prospective case series.

METHODS

Hundred unselected consecutive in-patients admitted with myelopathy were studied. Myelopathy aetiologies were established by collating information obtained from magnetic resonance imaging (MRI) scans, CSF and blood studies, CXR findings, non-neurological illness and response to treatment. Data were analysed in terms of two cohorts, HIV positive and HIV negative.

RESULTS

Approximately 50% of the patients presenting and admitted to our hospital with non-traumatic myelopathy are HIV positive. The HIV positive myelopathy patients were younger (20-40 years) and had infectious aetiologies. Tuberculosis was the most frequently identified cause of myelopathy. The majority of HIV-positive patients had advanced HIV infection. Anti-retroviral treatment did not influence myelopathy aetiologies. The HIV-negative patients were older and had neoplasms, followed by degenerative spondylosis as the main myelopathy causes.

CONCLUSION

HIV influences the non-traumatic myelopathy spectrum in regions with high HIV prevalence. Empiric treatment of HIV-myelopathy patients with anti-tuberculous medications where resources are severely limited has merit.

Characterization of HIV-Associated Neurocognitive Disorders among individuals starting antiretroviral therapy in South Africa

HIV-Associated Neurocognitive Disorders (HAND) exert an impact on everyday functions, including adherence. The prevalence of and risk factors for HAND in patients commencing anti-retroviral therapy in Southern Africa are unknown. Participants from primary care clinics in Cape Town, South Africa underwent detailed neuropsychological, neuropsychiatric, and neuromedical evaluation. Using the updated American Academy of Neurology (AAN) criteria, participants were classified into categories of HAND, and demographic and clinical risk factors for HIV-dementia (HIV-D) were assessed. The prevalence of mild neurocognitive disorder (MND) and HIV-D were 42.4 and 25.4%, respectively. There were significant associations between lower levels of education and older age with HIV-D, and a trend to association with HIV-D and lower CD4 count. In a regression model, a lower level of education and male gender were predictive of HIV-D. These findings suggest that HAND are highly prevalent in primary care settings in South Africa where clade C HIV is predominant.

Schwann cell mitochondrial metabolism supports long-term axonal survival and peripheral nerve function

Mitochondrial dysfunction is a common cause of peripheral neuropathies. While the role of neuron and axonal mitochondria in peripheral nerve disease is well appreciated, whether Schwann cell (SC) mitochondrial deficits contribute to peripheral neuropathies is unclear. Here, we examine how SC mitochondrial dysfunction affects axonal survival and contributes to the decline of peripheral nerve function by generating mice with SC-specific mitochondrial deficits. These mice (Tfam-SCKOs) were produced through the tissue-specific deletion of the mitochondrial transcription factor A gene (Tfam), which is essential for mitochondrial DNA (mtDNA) transcription and maintenance. Tfam-SCKOs were viable, but as they aged, they developed a progressive peripheral neuropathy characterized by nerve conduction abnormalities as well as extensive muscle denervation. Morphological examination of Tfam-SCKO nerves revealed early preferential loss of small unmyelinated fibers followed by prominent demyelination and degeneration of larger-caliber axons. Tfam-SCKOs displayed sensory and motor deficits consistent with this pathology. Remarkably, the severe mtDNA depletion and respiratory chain abnormalities in Tfam-SCKO mice did not affect SC proliferation or survival. Mitochondrial function in SCs is therefore essential for maintenance of axonal survival and normal peripheral nerve function, suggesting that SC mitochondrial dysfunction contributes to human peripheral neuropathies.

Neurological complications in late-stage hospitalized patients with HIV disease

BACKGROUND AND OBJECTIVE

The nervous system is the most frequent and serious targets of human immunodeficiency virus (HIV) infection. In spite of a wide prevalence of neurological manifestations in HIV there are not many studies to look into it, especially from this part of the world. We investigated various neurological manifestations of HIV and their association with CD4 and CD8 counts at the time of presentation.

MATERIALS AND METHODS

All HIV-infected patients who presented to 750 bedded teaching hospital in North India were subjected to thorough neurological and neuropsychological evaluation. Wherever indicated, neuroimaging, cerebrospinal fluid study, electromyography, and nerve-conduction studies were performed to confirm the diagnosis. CD4 and CD8 counts were calculated.

RESULTS

A total of 416 HIV-positive patients were seen. Of them 269 were males. A total of 312 neurological events were identified in 268 patients having evidence of neurological involvement. HIV-associated dementia (HAD) was the most common cause of morbidity (33.65%), followed by CNS infections (21.63%). Most common CNS infection was tuberculosis (65.56%). CD4 counts in CNS infections and HAD were 64.8/μl and 83.52/μl, respectively. Most of the patients in our study had low scores on MMSE (22.32).

CONCLUSIONS

Even in the absence of overt neurological disease, subclinical involvement in the form of subtle cognitive and motor decline is found to occur with greater frequency. Most of these patients have lower CD4 and CD8 counts, thus substantiating the proposition that neuroAIDS is a late manifestation. Significant correlation exists between CD4 counts and type of neurological manifestation. We concluded that neuropsychological assessment should be mandatory for all HIV-positive patients.

High prevalence of distal sensory polyneuropathy in antiretroviral-treated and untreated people with HIV in Tanzania

OBJECTIVES

To describe the prevalence of distal sensory polyneuropathy (DSP), a complication of both advanced HIV disease and of antiretroviral therapy (ART), amongst Tanzanians with HIV, on and off ART (including stavudine) with CD4 counts above and below 200 cells/μl.

METHODS

We recruited participants attending ART clinic into four groups: >6 months ART exposure and (i) CD4 < 200 cells/μl or (ii) CD4 > 200 cells/μl (ART/CD4 < 200 and ART/CD4 > 200, respectively); ART-naïve and (iii) CD4 < 200 cells/μl or iv)CD4 > 200 cells/μl (noART/CD4 < 200 and noART/CD4 > 200, respectively). Primary outcome was DSP, as defined by presence of at least one symptom and one sign.

RESULTS

Of 326 evaluable participants, 81 (32 men, median age 38 years, median CD4 142 cells/μl) were enrolled in the ART/CD4 < 200 group, 78 (17 men, median age 37 years, median CD4 345 cells/μl) in ART/CD4 > 200, 81 (30 men, median age 37 years, median CD4 128 cells/μl) in noART/CD4 < 200 and 86 (22 men, median age 33 years, median CD4 446 cells/μl) in noART/CD4 > 200. Numbness was the most commonly reported symptom. DSP prevalence ranged from 43.2% in ART/CD4 < 200 to 20.9% in noART/CD4 > 200. DSP was more common among men (adjusted odds ratio [aOR] 1.9, 95% confidence interval [CI] 1.2-3.3) and older participants (aOR 2.7, 95% CI 1.1-6.2 for age 40 + vs. <30 years).

CONCLUSION

Distal sensory polyneuropathy is common amongst those attending this clinic, even those with no ART exposure and a CD4 count above 200 cells/μl. Stavudine and didanosine expose HIV-infected patients to an additional avoidable risk of DSP. Access to non-neurotoxic ART regimes as well as earlier HIV diagnosis and initiation of ART is needed.

Interactions between human immunodeficiency virus (HIV)-1 Vpr expression and innate immunity influence neurovirulence

BACKGROUND

Viral diversity and abundance are defining properties of human immunodeficiency virus (HIV)-1's biology and pathogenicity. Despite the increasing availability of antiretroviral therapy, HIV-associated dementia (HAD) continues to be a devastating consequence of HIV-1 infection of the brain although the underlying disease mechanisms remain uncertain. Herein, molecular diversity within the HIV-1 non-structural gene, Vpr, was examined in RNA sequences derived from brain and blood of HIV/AIDS patients with or without HIV-associated dementia (HAD) together with the ensuing pathobiological effects.

RESULTS

Cloned brain- and blood-derived full length vpr alleles revealed that amino acid residue 77 within the brain-derived alleles distinguished HAD (77Q) from non-demented (ND) HIV/AIDS patients (77R) (p < 0.05) although vpr transcripts were more frequently detected in HAD brains (p < 0.05). Full length HIV-1 clones encoding the 77R-ND residue induced higher IFN-α, MX1 and BST-2 transcript levels in human glia relative to the 77Q-HAD encoding virus (p < 0.05) but both viruses exhibited similar levels of gene expression and replication. Myeloid cells transfected with 77Q-(pVpr77Q-HAD), 77R (pVpr77R-ND) or Vpr null (pVpr(-))-containing vectors showed that the pVpr77R-ND vector induced higher levels of immune gene expression (p < 0.05) and increased neurotoxicity (p < 0.05). Vpr peptides (amino acids 70-96) containing the 77Q-HAD or 77R-ND motifs induced similar levels of cytosolic calcium activation when exposed to human neurons. Human glia exposed to the 77R-ND peptide activated higher transcript levels of IFN-α, MX1, PRKRA and BST-2 relative to 77Q-HAD peptide (p < 0.05). The Vpr 77R-ND peptide was also more neurotoxic in a concentration-dependent manner when exposed to human neurons (p < 0.05). Stereotaxic implantation of full length Vpr, 77Q-HAD or 77R-ND peptides into the basal ganglia of mice revealed that full length Vpr and the 77R-ND peptide caused greater neurobehavioral deficits and neuronal injury compared with 77Q-HAD peptide-implanted animals (p < 0.05).

CONCLUSIONS

These observations underscored the potent neuropathogenic properties of Vpr but also indicated viral diversity modulates innate neuroimmunity and neurodegeneration.

Pathogenesis of HIV in the central nervous system

HIV can infect the brain and impair central nervous system (CNS) function. Combination antiretroviral therapy (cART) has not eradicated CNS complications. HIV-associated neurocognitive disorders (HAND) remain common despite cART, although attenuated in severity. This may result from a combination of factors including inadequate treatment of HIV reservoirs such as circulating monocytes and glia, decreased effectiveness of cART in CNS, concurrent illnesses, stimulant use, and factors associated with prescribed drugs, including antiretrovirals. This review highlights recent investigations of HIV-related CNS injury with emphasis on cART-era neuropathological mechanisms in the context of both US and international settings.

Intracisternal rSV40 administration provides effective pan-CNS transgene expression

Potential genetic treatments for many generalized central nervous system (CNS) diseases require transgene expression throughout the CNS. Using oxidant stress and apoptosis caused by HIV-1 envelope gp120 as a model, we studied pan-CNS neuroprotective gene delivery into the cisterna magna (CM). Recombinant SV40 vectors carrying Cu/Zn superoxide dismutase or glutathione peroxidase were injected into rat CMs following intraperitoneal administration of mannitol. Sustained transgene expression was seen in neurons throughout the CNS. On challenge, 8 weeks later with gp120 injected into the caudate putamen, significant neuroprotection was documented. Thus, intracisternal administration of antioxidant-carrying rSV40 vectors may be useful in treating widespread CNS diseases such as HIV-1-associated neurocognitive disorders characterized by oxidative stress.

Virologic outcomes of HAART with concurrent use of cytochrome P450 enzyme-inducing antiepileptics: a retrospective case control study

BACKGROUND

To evaluate the efficacy of highly-active antiretroviral therapy (HAART) in individuals taking cytochrome P450 enzyme-inducing antiepileptics (EI-EADs), we evaluated the virologic response to HAART with or without concurrent antiepileptic use.

METHODS

Participants in the US Military HIV Natural History Study were included if taking HAART for ≥6 months with concurrent use of EI-AEDs phenytoin, carbamazepine, or phenobarbital for ≥28 days. Virologic outcomes were compared to HAART-treated participants taking AEDs that are not CYP450 enzyme-inducing (NEI-AED group) as well as to a matched group of individuals not taking AEDs (non-AED group). For participants with multiple HAART regimens with AED overlap, the first 3 overlaps were studied.

RESULTS

EI-AED participants (n = 19) had greater virologic failure (62.5%) compared to NEI-AED participants (n = 85; 26.7%) for the first HAART/AED overlap period (OR 4.58 [1.47-14.25]; P = 0.009). Analysis of multiple overlap periods yielded consistent results (OR 4.29 [1.51-12.21]; P = 0.006). Virologic failure was also greater in the EI-AED versus NEI-AED group with multiple HAART/AED overlaps when adjusted for both year of and viral load at HAART initiation (OR 4.19 [1.54-11.44]; P = 0.005). Compared to the non-AED group (n = 190), EI-AED participants had greater virologic failure (62.5% vs. 42.5%; P = 0.134), however this result was only significant when adjusted for viral load at HAART initiation (OR 4.30 [1.02-18.07]; P = 0.046).

CONCLUSIONS

Consistent with data from pharmacokinetic studies demonstrating that EI-AED use may result in subtherapeutic levels of HAART, EI-AED use is associated with greater risk of virologic failure compared to NEI-AEDs when co-administered with HAART. Concurrent use of EI-AEDs and HAART should be avoided when possible.

[Treatment of neuro-AIDS on a neurological intensive care unit: epidemiology and predictors of outcome]

BACKGROUND

Investigations concerning the outcome for patients suffering from neuro-AIDS treated on a neurological intensive care unit and specific predictors indicating "dead" were analyzed.

MATERIAL AND METHODS

A total of 56 patients with a mean age of 39 ± 0.7 years, a mean CD4+ cell count of 130 ± 166 CD4+ cells/µl and viral load of 146,520 ± 198,059 copies/ml were treated on a neurological intensive care unit due to different forms of neuro-AIDS.

RESULTS

Of the patients, 34% were immigrants of whom 74% came from sub-Saharan regions. In 57% of the patients the diagnosis of HIV infection was made during therapy on the neurological intensive care unit. The median for the time between diagnosis of HIV infection and the treatment on the neurological intensive care unit was 8 days for immigrants and 10 years for residents. The most common manifestations of neuro-AIDS were cerebral toxoplasmosis, cryptococcosis and progressive multifocal leukoencephalopathy (PML). Fifty per cent of the patients (n=28) died during treatment on the neurological intensive care unit. Negative predictors for the outcome "dead" were (a) artificial ventilation, (b) antiretroviral naïve immigrant, (c) primary cerebral lymphoma and (d) missing antiretroviral therapy as a result of admission to the intensive care unit.

DISCUSSION

The rate of death during treatment of neuro-AIDS on a neurological intensive care unit is much higher than during treatment of internal medicine problems of HIV infection. Antiretroviral naïve immigrants show a much higher rate of death compared to residents in Germany. A lot of research and effort is necessary to improve the availability of the Highly Active Anti-Retroviral Therapy (HAART) worldwide in order to improve the outcome especially for immigrants with neuro-AIDS treated on a neurological intensive care unit.

Peripheral neuropathy in HIV: prevalence and risk factors

OBJECTIVES

To estimate neuropathic sign/symptom rates with initiation of combination antiretroviral therapy (cART) in HIV-infected ART-naive patients, and to investigate risk factors for: peripheral neuropathy and symptomatic peripheral neuropathy (SPN), recovery from peripheral neuropathy/SPN after neurotoxic ART (nART) discontinuation, and the absence of peripheral neuropathy/SPN while on nART.

DESIGN

AIDS Clinical Trials Group (ACTG) Longitudinal Linked Randomized Trial participants who initiated cART in randomized trials for ART-naive patients were annually screened for symptoms/signs of peripheral neuropathy. ART use and disease characteristics were collected longitudinally.

METHODS

Peripheral neuropathy was defined as at least mild loss of vibration sensation in both great toes or absent/hypoactive ankle reflexes bilaterally. SPN was defined as peripheral neuropathy and bilateral symptoms. Generalized estimating equation logistic regression was used to estimate associations.

RESULTS

Two thousand, one hundred and forty-one participants were followed from January 2000 to June 2007. Rates of peripheral neuropathy/SPN at 3 years were 32.1/8.6% despite 87.1% with HIV-1RNA 400 copies/ml or less and 70.3% with CD4 greater than 350 cells/μl. Associations with higher odds of peripheral neuropathy included older patient age and current nART use. Associations with higher odds of SPN included older patient age, nART use, and history of diabetes mellitus. Associations with lower odds of recovery after nART discontinuation included older patient age. Associations with higher odds of peripheral neuropathy while on nART included older patient age and current protease inhibitor use. Associations with higher odds of SPN while on nART included older patient age, history of diabetes, taller height, and protease inhibitor use.

CONCLUSION

Signs of peripheral neuropathy remain despite virologic/immunologic control but frequently occurs without symptoms. Aging is a risk factor for peripheral neuropathy/SPN.

[Visual function evaluation in human immunodeficiency virus carriers]

OBJECTIVE

To determine whether there are changes in the peripapillary nerve fibre layer, in colour vision, contrast sensitivity, dark adaptation and electroretinography changes in these patients who do not have infectious retinitis.

METHODS

We studied 52 patients without ocular pathology; the mean age was 35.88 years old.

RESULTS

We observed less thickness in all quadrants, except the nasal. The colour vision was altered in 27.77% of the patients. The contrast sensitivity test showed high frequency alterations. There was no statistically significant difference in the electroretinography test or in dark adaptation.

CONCLUSIONS

There are changes in the peripapillary nerve fibre layer thickness; also we found changes in colour vision, contrast sensitivity and a decreasing trend of the B wave in the electroreninogram.

Neurologic manifestations of human immunodeficiency virus-2: dementia, myelopathy, and neuropathy in West Africa

While well documented in human immunodeficiency virus (HIV)-1, neurologic sequelae have not been systematically evaluated in HIV-2. After excluding for confounding comorbidities, 67 individuals from a rural cohort in Guinea-Bissau (22 HIV-2 participants, 45 seronegative controls) were evaluated. HIV + individuals were divided into CD4 < 350 and CD4 ≥ 350 for analysis. HIV-associated neurocognitive disorders (HAND), assessed by the International HIV Dementia Scale (IHDS), distal sensory polyneuropathy (DSPN), and myelopathy were the main outcome variables. In univariate analysis, there was no difference in IHDS scores among groups. When analyzed by primary education attainment, IHDS scores were nonsignificantly higher (p = 0.06) with more education. There was no significant difference in DSPN prevalence among groups; overall, 45% of participants had DSPN. There were no cases of myelopathy. In multivariate linear regression, higher IHDS scores were significantly correlated with older age (coefficient = -0.11, p < 0.001). Logistic regression analysis showed that older age (odds ratio (OR) 95% CI 1.04-1.20), lower CD4 count (OR 95% CI 0.996-0.999), and higher BMI (OR 95% CI 1.02-1.43) significantly predicted the presence of DSPN. While a significant increase in cognitive impairment was not observed in HIV-2-infected individuals, the study suggests the IHDS may be a less effective screening tool for HAND in settings of lower educational attainment as encountered in rural Guinea-Bissau. Similar to HIV-1, DSPN seems to occur with lower CD4 counts in HIV-2. Further study of the viral-host interactions in HIV-2 and its consequent neurological diseases may provide an avenue for understanding the epidemic problems of HIV-1.

Translational research in NeuroAIDS: a neuroimmune pharmacology-related course

Neuroimmune pharmacology (NIP) can be considered a multidisciplinary science where areas of neuroscience, immunology, and pharmacology intersect in neurological disorders. The R25 training program titled "Translational Research in NeuroAIDS and Mental Health (TR-NAMH): An innovative mentoring program to promote diversity in NeuroAIDS Research (R25 MH080661)" at the Johns Hopkins University is a web-based interactive course with the goal to improve the capacity of high quality research by developing mentoring programs for (1) doctoral and postdoctoral candidates and junior faculty from racial and ethnic minorities and (2) non-minority individuals at the same levels, whose research focuses on NeuroAIDS disparity issues such as HIV-associated neurocognitive disorders (HAND). This web-based interactive course overcomes the limitations of traditional education such as access to expert faculty and financial burden of scientists from racial and ethnic minority groups in the field of NeuroAIDS research and NIP and identifies rich nurturing environments for investigators to support their careers. The TR-NAMH program identifies a cadre of talented students and investigators eager to commit to innovative educational and training sessions in NeuroAIDS and NIP. The interplay between NIP changes precipitated by HIV infection in the brain makes the study of HAND an outstanding way to integrate important concepts from these two fields. The course includes activities besides those related to didactic learning such as research training and long-term mentoring; hence, the newly learned topics in NIP are continually reinforced and implemented in real-time experiences. We describe how NIP is integrated in the TR-NAMH program in the context of HAND.

Neurological complications of HIV infection in critically ill patients: clinical features and outcomes

OBJECTIVE

We aimed to investigate the prognosis of HIV-infected patients with acute neurological complications at the highly active antiretroviral therapy (HAART) era.

METHODS

We performed a retrospective study in HIV-infected patients admitted to a medical ICU with neurological complications between 2001 and 2008.

RESULTS

Among the 210 studied patients (median [interquartile range] CD4-cell count: 80 [18-254]/μL; HIV viral load: 4.8 [2-5.3] log₁₀/mL), 40 (19%) had unknown HIV status at admission. Neurological complications consisted in delirium (45%), coma (39%), seizures (32%) and/or intracranial hypertension (21%). Admission diagnoses were AIDS-defining CNS disease for 88 (42%) patients, non-AIDS-defining CNS disease for 45 (21%), and systemic disease with neurological signs for 77 (37%). Seizures (p=0.003), focal deficit (p<0.001) and intracranial hypertension (p<0.001) were more frequently observed in patients with AIDS-defining CNS disease. Factors independently associated with ICU mortality (29.5%) were intracranial hypertension [odds ratio (OR), 5.09; 95% confidence interval (95% CI), 2.17-11.91], vasopressor use [OR, 3.92; 95% CI, 1.78-8.60] and SAPS II score [per 10-point increment, OR, 1.59; 95% CI, 1.31-1.93].

CONCLUSIONS

Prognosis of HIV-infected patients with neurological complications depends rather on clinical presentation than on HIV-related parameters. Intracranial hypertension symptoms at admission have a major impact on outcome.

ER-β mediates 17β-estradiol attenuation of HIV-1 Tat-induced apoptotic signaling

The protective actions of estrogen have been well evaluated in various models of neurodegeneration. These neuroprotective mechanisms may include a direct neuronal antiapoptotic effect as estrogen modulates actions of key regulators of the mitochondrial/intrinsic apoptotic cascade. We tested the ability of estrogen to protect against apoptotic signaling in cortical cell cultures exposed to Tat 1-86 (50 nM), and additionally, whether the beneficial actions of estrogen involved an estrogen receptor sensitive mechanism. We demonstrated that estrogen pretreatment significantly delayed Tat-induced cell death in primary cortical cultures. Pretreatment with 17β-estradiol (10 nM) attenuated the increased expression of antiapoptotic protein Bcl-2, proapoptotic protein Bax and activation of caspases linked to mitochondrial apoptotic pathway following Tat exposure. In addition, select components of apoptotic pathway signaling appear more sensitive to estrogen receptor (ER) activation, as the addition of ER antagonist ICI 182780 reversed estrogen downregulation of Bax and caspase 3, while estrogen effects on Tat-induced Bcl-2 and caspase 9 expression were maintained. Moreover, the addition of preferential ERα and ERβ antagonists (MPP dihydrochloride and PHTPP) indicated that estrogen effects on caspase 3 may be mediated by both receptor subtypes, whereas, was more involved in estrogen effects on Bax. Our data suggest that estrogen intervenes against HIV-1 Tat-induced cortical neuronal dysfunction via intersecting mitochondrial apoptotic pathway signaling in an ER-sensitive manner.

Abnormalities in resting-state functional connectivity in early human immunodeficiency virus infection

Limited information is available concerning changes that occur in the brain early in human immunodeficiency virus (HIV) infection. This investigation evaluated resting-state functional connectivity, which is based on correlations of spontaneous blood oxygen level-dependent functional magnetic resonance imaging (fMRI) oscillations between brain regions, in 15 subjects within the first year of HIV infection and in 15 age-matched controls. Resting-state fMRI data for each session were concatenated in time across subjects to create a single 4D dataset and decomposed into 36 independent component analysis (ICA) using Multivariate Exploratory Linear Optimized Decomposition into Independent Components. ICA components were back-reconstructed for each subject's 4D data to estimate subject-specific spatial maps using the dual-regression technique. Comparison of spatial maps between HIV and controls revealed significant differences in the lateral occipital cortex (LOC) network. Reduced coactivation in left inferior parietal cortex within the LOC network was identified in the HIV subjects. Connectivity strength within this region correlated with performance on tasks involving visual-motor coordination (Grooved Pegboard and Rey Figure Copy) in the HIV group. The findings indicate prominent changes in resting-state functional connectivity of visual networks early in HIV infection. This network may sustain injury in association with the intense viremia and brain viral invasion before immune defenses can contain viral replication. Resting-state functional connectivity may have utility as a noninvasive neuroimaging biomarker for central nervous system impairment in early HIV infection.

Penalized least squares regression methods and applications to neuroimaging

The goals of this paper are to review the most popular methods of predictor selection in regression models, to explain why some fail when the number P of explanatory variables exceeds the number N of participants, and to discuss alternative statistical methods that can be employed in this case. We focus on penalized least squares methods in regression models, and discuss in detail two such methods that are well established in the statistical literature, the LASSO and Elastic Net. We introduce bootstrap enhancements of these methods, the BE-LASSO and BE-Enet, that allow the user to attach a measure of uncertainty to each variable selected. Our work is motivated by a multimodal neuroimaging dataset that consists of morphometric measures (volumes at several anatomical regions of interest), white matter integrity measures from diffusion weighted data (fractional anisotropy, mean diffusivity, axial diffusivity and radial diffusivity) and clinical and demographic variables (age, education, alcohol and drug history). In this dataset, the number P of explanatory variables exceeds the number N of participants. We use the BE-LASSO and BE-Enet to provide the first statistical analysis that allows the assessment of neurocognitive performance from high dimensional neuroimaging and clinical predictors, including their interactions. The major novelty of this analysis is that biomarker selection and dimension reduction are accomplished with a view towards obtaining good predictions for the outcome of interest (i.e., the neurocognitive indices), unlike principal component analysis that are performed only on the predictors' space independently of the outcome of interest.

Rescue of adult hippocampal neurogenesis in a mouse model of HIV neurologic disease

The prevalence of central nervous system (CNS) neurologic dysfunction associated with human immunodeficiency virus (HIV) infection continues to increase, despite the use of antiretroviral therapy. Previous work has focused on the deleterious effects of HIV on mature neurons and on development of neuroprotective strategies, which have consistently failed to show a meaningful clinical benefit. It is now well established that new neurons are continuously generated in discrete regions in the adult mammalian brain, and accumulating evidence supports important roles for these neurons in specific cognitive functions. In a transgenic mouse model of HIV neurologic disease with glial expression of the HIV envelope protein gp120, we demonstrate a significant reduction in proliferation of hippocampal neural progenitors in the dentate gyrus of adult animals, resulting in a dramatic decrease in the number of newborn neurons in the adult brain. We identify amplifying neural progenitor cells (ANPs) as the first class of progenitors affected by gp120, and we also demonstrate that newly generated neurons exhibit aberrant dendritic development. Furthermore, voluntary exercise and treatment with a selective serotonin reuptake inhibitor increase the ANP population and rescue the observed deficits in gp120 transgenic mice. Thus, during HIV infection, the envelope protein gp120 may potently inhibit adult hippocampal neurogenesis, and neurorestorative approaches may be effective in ameliorating these effects. Our study has significant implications for the development of novel therapeutic approaches for HIV-infected individuals with neurologic dysfunction and may be applicable to other neurodegenerative diseases in which hippocampal neurogenesis is impaired.

Utility of quantitative sensory testing and screening tools in identifying HIV-associated peripheral neuropathy in Western Kenya: pilot testing

BACKGROUND/AIM

Neuropathy is the most common neurologic complication of HIV but is widely under-diagnosed in resource-constrained settings. We aimed to identify tools that accurately distinguish individuals with moderate/severe peripheral neuropathy and can be administered by non-physician healthcare workers (HCW) in resource-constrained settings.

METHODS

We enrolled a convenience sample of 30 HIV-infected outpatients from a Kenyan HIV-care clinic. A HCW administered the Neuropathy Severity Score (NSS), Single Question Neuropathy Screen (Single-QNS), Subjective Peripheral Neuropathy Screen (Subjective-PNS), and Brief Peripheral Neuropathy Screen (Brief-PNS). Monofilament, graduated tuning fork, and two-point discrimination examinations were performed. Tools were validated against a neurologist's clinical assessment of moderate/severe neuropathy.

RESULTS

The sample was 57% male, mean age 38.6 years, and mean CD4 count 324 cells/µL. Neurologist's assessment identified 20% (6/30) with moderate/severe neuropathy. Diagnostic utilities for moderate/severe neuropathy were: Single-QNS--83% sensitivity, 71% specificity; Subjective-PNS-total--83% sensitivity, 83% specificity; Subjective-PNS-max and NSS--67% sensitivity, 92% specificity; Brief-PNS--0% sensitivity, 92% specificity; monofilament--100% sensitivity, 88% specificity; graduated tuning fork--83% sensitivity, 88% specificity; two-point discrimination--75% sensitivity, 58% specificity.

CONCLUSIONS

Pilot testing suggests Single-QNS, Subjective-PNS, and monofilament examination accurately identify HIV-infected patients with moderate/severe neuropathy and may be useful diagnostic tools in resource-constrained settings.

Peripheral biomarkers do not correlate with cognitive impairment in highly active antiretroviral therapy-treated subjects with human immunodeficiency virus type 1 infection

Neuropsychological (NP) impairments in human immunodeficiency virus (HIV)-infected individuals remain high despite the introduction of highly active antiretroviral therapy (HAART). We sought to determine whether or not a monocyte gene expression profile along with other peripheral factors would correlate with neuropsychological impairment among HIV-infected individuals. Forty-four HIV-1-seropositive subjects (HIV+) on HAART and 11 HIV-1-seronegative controls (HIV-) had NP testing and blood drawn for monocyte gene expression analysis. All HIV+ subjects were assessed for CD4 counts, apolipoprotein E (ApoE) genotype, viral load, and plasma lipopolysaccharide (LPS) and soluble CD14 (sCD14). NP scores were normalized to age, gender, and education. Twenty-five percent of HIV+ individuals showed abnormal NP testing results (> 1.5 SD below normal in two domains). HIV+ individuals had deficits in attention/working memory, verbal learning, and information processing speed compared to HIV- controls. There was no correlation between overall NP impairment and plasma viral load, level of education, age, ethnic diversity, sCD14, plasma LPS, CD4 cell count, ApoE genotype, or years of infection. However, greater years of infection had worse visual learning performance. sCD14 and CD4 nadir positively correlated with information processing speed and fine motor skills, respectively. LPS correlated with viral load but not cognitive impairment. Monocyte gene expression confirmed a chronic inflammatory profile that correlated with viral load but not cognition. No blood index or profile was associated with overall NP impairment.

Mitochondrial dysfunction in distal axons contributes to human immunodeficiency virus sensory neuropathy

OBJECTIVE

Accumulation of mitochondrial DNA (mtDNA) damage has been associated with aging and abnormal oxidative metabolism. We hypothesized that in human immunodeficiency virus-associated sensory neuropathy (HIV-SN), damaged mtDNA accumulates in distal nerve segments, and that a spatial pattern of mitochondrial dysfunction contributes to the distal degeneration of sensory nerve fibers.

METHODS

We measured levels of common deletion mutations in mtDNA and expression levels of mitochondrial respiratory chain complexes of matched proximal and distal nerve specimens from patients with and without HIV-SN. In mitochondria isolated from peripheral nerves of simian immunodeficiency virus (SIV)-infected macaques, a model of HIV-SN, we measured mitochondrial function and generation of reactive oxygen species.

RESULTS

We identified increased levels of mtDNA common deletion mutation in postmortem sural nerves of patients with HIV-SN as compared to uninfected patients or HIV patients without sensory neuropathy. Furthermore, we found that common deletion mutation in mtDNA was more prevalent in distal sural nerves compared to dorsal root ganglia. In a primate model of HIV-SN, freshly isolated mitochondria from sural nerves of macaques infected with a neurovirulent strain of SIV showed impaired mitochondrial function compared to mitochondria from proximal nerve segments.

INTERPRETATION

Our findings suggest that mtDNA damage accumulates in distal mitochondria of long axons, especially in patients with HIV-SN, and that this may lead to reduced mitochondrial function in distal nerves relative to proximal segments. Although our findings are based on HIV-SN, if confirmed in other neuropathies, these observations could explain the length-dependent nature of most axonal peripheral neuropathies.

Functional proteomic analysis for regulatory T cell surveillance of the HIV-1-infected macrophage

Regulatory T cells (Treg) induce robust neuroprotection in murine models of neuroAIDS, in part, through eliciting anti-inflammatory responses for HIV-1-infected brain mononuclear phagocytes (MP; macrophage and microglia). Herein, using both murine and human primary cell cultures in proteomic and cell biologic tests, we report that Treg promotes such neuroprotection by an even broader range of mechanisms than previously seen including inhibition of virus release, killing infected MP, and inducing phenotypic cell switches. Changes in individual Treg-induced macrophage proteins were quantified by iTRAQ labeling followed by mass spectrometry identifications. Reduction in virus release paralleled the upregulation of interferon-stimulated gene 15, an ubiquitin-like protein involved in interferon-mediated antiviral immunity. Treg killed virus-infected macrophages through caspase-3 and granzyme and perforin pathways. Independently, Treg transformed virus-infected macrophages from an M1 to an M2 phenotype by down- and up- regulation of inducible nitric oxide synthase and arginase 1, respectively. Taken together, Treg affects a range of virus-infected MP functions. The observations made serve to challenge the dogma of solitary Treg immune suppressor functions and provides novel insights into how Treg affects adaptive immunosurveillance for control of end organ diseases, notably neurocognitive disorders associated with advanced viral infection.

Cervical spondylotic myelopathy

BACKGROUND

Cervical spondylosis is part of the aging process and affects most people if they live long enough. Degenerative changes affecting the intervertebral disks, vertebrae, facet joints, and ligamentous structures encroach on the cervical spinal canal and damage the spinal cord, especially in patients with a congenitally small cervical canal. Cervical spondylotic myelopathy (CSM) is the most common cause of myelopathy in adults.

REVIEW SUMMARY

The anatomy, pathophysiology, clinical presentation, differential diagnosis, diagnostic investigation, natural history, and treatment options for CSM are summarized. Patients present with signs and symptoms of cervical spinal cord dysfunction with or without cervical nerve root injury. The condition may or may not be accompanied by pain in the neck and/or upper limb. The differential diagnosis is broad. Imaging, typically with magnetic resonance imaging, is the most useful diagnostic tool. Electrophysiologic testing can help exclude alternative diagnoses. The effectiveness of conservative treatments is unproven. Surgical decompression improves neurologic function in some patients and prevents worsening in others, but is associated with risk.

CONCLUSIONS

Neurologists should be familiar with this very common condition. Patients with mild signs and symptoms of CSM can be monitored. Surgical decompression from an anterior or posterior approach should be considered in patients with progressive and moderate to severe neurologic deficits.

[HIV-associated neuropathies]

Human immunodeficiency virus (HIV)-associated polyneuropathy has become the most common neurological complication of HIV infection and is one of the main risk factors for development of a neuropathy worldwide. Therefore HIV should always be considered as an underlying cause in patients with neuropathy. Many types of peripheral neuropathies are seen in HIV infection depending on the stage of infection. The inflammatory demyelinating neuropathies both acute (Guillain-Barré syndrome, GBS) and chronic (chronic inflammatory demyelinating neuropathy, CIDP) occur mainly at the time of seroconversion or early in the course of the disease while syndromes associated with opportunistic infections like CMV (i.e. polyradiculoneuropathy) occur in the late phase of HIV infection and are related to the loss of immune function. Distal symmetrical polyneuropathy (DSP) is the most common neuropathy in HIV-infected patients. We review the clinical manifestations, epidemiology, clinical diagnostics, pathophysiology and management strategies for HIV-associated polyneuropathies.

Suppressor of cytokine signaling 3 inhibits antiviral IFN-beta signaling to enhance HIV-1 replication in macrophages

HIV-1 replication within macrophages of the CNS often results in cognitive and motor impairment, which is known as HIV-associated dementia (HAD) in its most severe form. IFN-beta suppresses viral replication within these cells during early CNS infection, but the effect is transient. HIV-1 eventually overcomes this protective innate immune response to resume replication through an unknown mechanism, initiating the progression toward HAD. In this article, we show that Suppressor of Cytokine Signaling (SOCS)3, a molecular inhibitor of IFN signaling, may allow HIV-1 to evade innate immunity within the CNS. We found that SOCS3 is elevated in an in vivo SIV/macaque model of HAD and that the pattern of expression correlates with recurrence of viral replication and onset of CNS disease. In vitro, the HIV-1 regulatory protein transactivator of transcription induces SOCS3 in human and murine macrophages in a NF-kappaB-dependent manner. SOCS3 expression attenuates the response of macrophages to IFN-beta at proximal levels of pathway activation and downstream antiviral gene expression and consequently overcomes the inhibitory effect of IFN-beta on HIV-1 replication. These studies indicate that SOCS3 expression, induced by stimuli present in the HIV-1-infected brain, such as transactivator of transcription, inhibits antiviral IFN-beta signaling to enhance HIV-1 replication in macrophages. This consequence of SOCS3 expression in vitro, supported by a correlation with increased viral load and onset of CNS disease in vivo, suggests that SOCS3 may allow HIV-1 to evade the protective innate immune response within the CNS, allowing the recurrence of viral replication and, ultimately, promoting progression toward HAD.

HIV-1 viral protein R causes peripheral nervous system injury associated with in vivo neuropathic pain

Painful peripheral neuropathy has become the principal neurological disorder in HIV/AIDS patients. Herein, we investigated the effects of a cytotoxic HIV-1 accessory protein, viral protein R (Vpr), on the peripheral nervous system (PNS). Host and viral gene expression was investigated in peripheral nerves from HIV-infected individuals and in HIV-infected human dorsal root ganglion (DRG) cultures by RT-PCR and immunocytochemistry. Cytosolic calcium ([Ca(2+)]) fluxes and neuronal membrane responses were analyzed in cultured DRGs. Neurobehavioral responses and cytokine levels were assessed in a transgenic mouse model in which the vpr transgene was expressed in an immunodeficient background (vpr/RAG1(-/-)). Vpr transcripts and proteins were detected in peripheral nerves and DRGs from HIV-infected patients. Exposure of rat or human cultured DRG neurons to Vpr rapidly increased [Ca(2+)] and action potential frequency while increasing input resistance. HIV infection of human DRG cultures caused neurite retraction (P<0.05), accompanied by induction of interferon-α (IFN-α) transcripts (P<0.05). vpr/RAG1(-/-) mice expressed Vpr together with increased IFN-α (P<0.05) in the PNS and also exhibited mechanical allodynia, unlike their vpr/RAG1(-/-) littermates (P<0.05). Herein, Vpr caused DRG neuronal damage, likely through cytosolic calcium activation and cytokine perturbation, highlighting Vpr's contribution to HIV-associated peripheral neuropathy and ensuing neuropathic pain.

Cognitive dysfunction in HIV patients despite long-standing suppression of viremia

OBJECTIVE

To determine the prevalence of cognitive complaints and HIV-associated neurocognitive disorders (HANDs) in a cohort of aviremic HIV-positive patients. To evaluate the relevance of the HIV dementia scale to detect HANDs.

DESIGN

Assessment of HANDs with neuropsychological tests.

METHODS

Two hundred HIV-infected patients with undetectable HIV-1 RNA concentrations in the plasma, no history of major opportunistic infection of the central nervous system in the past 3 years, no current use of intravenous drugs, and no major depression answered a questionnaire designed to elicit cognitive complaints. Cognitive functions of 50 complaining and 50 noncomplaining HIV-positive patients were assessed.

RESULTS

Patients had undetectable HIV-1 RNA concentrations for a median time of 48 months (range 3.2-136.6). The prevalence of cognitive complaints was 27%. The prevalence of HANDs was 84% among patients with cognitive complaints (asymptomatic neurocognitive impairment 24%, mild neurocognitive disorders 52%, and HIV-associated dementia 8%) and 64% among noncomplainers (asymptomatic neurocognitive impairment 60%, mild neurocognitive disorders 4%, and HIV-associated dementia 0%; P < 0.001). A score of 14 points or less on the HIV dementia scale yielded a positive predictive value of HANDs of 92% in complainers and 82% in noncomplainers.

CONCLUSION

The prevalence of HANDs is high even in long-standing aviremic HIV-positive patients. However, HANDs without functional repercussion in daily life (asymptomatic neurocognitive impairment) is the most frequent subtype observed. In this population, the HIV dementia scale with a cutoff of 14 points or less seems to provide a useful tool to screen for the presence of HANDs.

Measurement of soluble inflammatory mediators in cerebrospinal fluid of human immunodeficiency virus-positive patients at distinct stages of infection by solid-phase protein array

The objective of this study was to evaluate immune cytokine expression in cerebrospinal fluid (CSF) of patients with human immunodeficiency virus-1 (HIV-1)-associated dementia (HAD) using a novel cytokine array assay. HIV-1 induces a condition resembling classical subcortical dementia, known as HAD. The immune mechanisms contributing to HAD have not been elucidated. Cytokine expression in CSF was determined by solid-phase protein array in 33 neurologically asymptomatic HIV-positive male patients and were compared to levels in non-HIV controls and patients with HAD. Neurological examinations and lumbar and venous punctures were conducted in all patients and controls. Interleukin (IL)-1, IL-4, and IL-10, were up-regulated in all treated acquired immunodeficiency syndrome (AIDS) patients independent of neurological status compared to controls. In contrast, interferon gamma (IFN-gamma), IL-1alpha, IL-15, and tumor necrosis factor alpha (TNF-alpha) were highly expressed in patients with HAD compared to undemented HIV-positive patients. These results show that solid-phase protein array can detect immunological changes in patients infected with HIV. Cytokine expression levels differ in different disease stages and in patients on different treatment paradigms. Pending further validation on a larger number of patients, this method may be a useful tool in CSF diagnostics and the longitudinal evaluation of patient with HAD.

Causality in acute encephalitis: defining aetiologies

Defining the causal relationship between a microbe and encephalitis is complex. Over 100 different infectious agents may cause encephalitis, often as one of the rarer manifestations of infection. The gold-standard techniques to detect causative infectious agents in encephalitis in life depend on the study of brain biopsy material; however, in most cases this is not possible. We present the UK perspective on aetiological case definitions for acute encephalitis and extend them to include immune-mediated causes. Expert opinion was primarily used and was supplemented by literature-based methods. Wide usage of these definitions will facilitate comparison between studies and result in a better understanding of the causes of this devastating condition. They provide a framework for regular review and updating as the knowledge base increases both clinically and through improvements in diagnostic methods. The importance of new and emerging pathogens as causes of encephalitis can be assessed against the principles laid out here.

The macrophage in HIV-1 infection: from activation to deactivation?

Macrophages play a crucial role in innate and adaptative immunity in response to microorganisms and are an important cellular target during HIV-1 infection. Recently, the heterogeneity of the macrophage population has been highlighted. Classically activated or type 1 macrophages (M1) induced in particular by IFN-γ display a pro-inflammatory profile. The alternatively activated or type 2 macrophages (M2) induced by Th-2 cytokines, such as IL-4 and IL-13 express anti-inflammatory and tissue repair properties. Finally IL-10 has been described as the prototypic cytokine involved in the deactivation of macrophages (dM). Since the capacity of macrophages to support productive HIV-1 infection is known to be modulated by cytokines, this review shows how modulation of macrophage activation by cytokines impacts the capacity to support productive HIV-1 infection. Based on the activation status of macrophages we propose a model starting with M1 classically activated macrophages with accelerated formation of viral reservoirs in a context of Th1 and proinflammatory cytokines. Then IL-4/IL-13 alternatively activated M2 macrophages will enter into the game that will stop the expansion of the HIV-1 reservoir. Finally IL-10 deactivation of macrophages will lead to immune failure observed at the very late stages of the HIV-1 disease.