ABSTRACT
BACKGROUND: HIV-associated neuroinflammation is believed to be a major contributing factor in the development of HIV-associated neurocognitive disorders (HAND). In this study, we used micropositron emission tomography (PET) imaging to quantify neuroinflammation in HIV-1 transgenic rat (Tg), a small animal model of HIV, known to develop neurological and behavioral problems. METHODS: Dynamic [(18)F]DPA-714 PET imaging was performed in Tg and age-matched wild-type (WT) rats in three age groups: 3-, 9-, and 16-month-old animals. As a positive control for neuroinflammation, we performed unilateral intrastriatal injection of quinolinic acid (QA) in a separate group of WT rats. To confirm our findings, we performed multiplex immunofluorescent staining for Iba1 and we measured cytokine/chemokine levels in brain lysates of Tg and WT rats at different ages. RESULTS: [(18)F]DPA-714 uptake in HIV-1 Tg rat brains was generally higher than in age-matched WT rats but this was not statistically significant in any age group. [(18)F]DPA-714 uptake in the QA-lesioned rats was significantly higher ipsilateral to the lesion compared to contralateral side indicating neuroinflammatory changes. Iba1 immunofluorescence showed no significant differences in microglial activation between the Tg and WT rats, while the QA-lesioned rats showed significant activation. Finally, cytokine/chemokine levels in brain lysates of the Tg rats and WT rats were not significantly different. CONCLUSION: Microglial activation might not be the primary mechanism for neuropathology in the HIV-1 Tg rats. Although [(18)F]DPA-714 is a good biomarker of neuroinflammation, it cannot be reliably used as an in vivo biomarker of neurodegeneration in the HIV-1 Tg rat.
Subject(s)
Brain Injuries/virology , Encephalitis/diagnostic imaging , Fluorodeoxyglucose F18/pharmacokinetics , HIV-1/metabolism , Positron-Emission Tomography , Pyrazoles/pharmacokinetics , Pyrimidines/pharmacokinetics , Analysis of Variance , Animals , Body Weight/drug effects , Body Weight/genetics , Brain Injuries/chemically induced , Brain Injuries/complications , Brain Injuries/diagnostic imaging , Brain Mapping , Cytokines/metabolism , Encephalitis/etiology , Fluorodeoxyglucose F18/blood , Functional Laterality , HIV-1/genetics , Male , Pyrazoles/blood , Pyrimidines/blood , Quinolinic Acid/toxicity , Rats , Rats, Inbred F344 , Rats, Transgenic , Time FactorsABSTRACT
The dopaminergic system is especially vulnerable to the effects of human immunodeficiency virus (HIV) infection, rendering dopaminergic deficits early surrogate markers of HIV-associated neuropathology. We quantified dopamine D2/3 receptors in young HIV-1 transgenic (Tg) (n â=â 6) and age-matched control rats (n â=â 7) and adult Tg (n â=â 5) and age-matched control rats (n â=â 5) using [18F]fallypride positron emission tomography (PET). Regional uptake was quantified as binding potential (BPND) using the two-tissue reference model with the cerebellum as the reference. Time-activity curves were generated for the ventral striatum, dorsal striatum, thalamus, and cerebellum. Whereas BPND values were significantly lower in the ventral striatum (p < .001) and dorsal striatum (p â=â .001) in the adult Tg rats compared to controls rats, they were significantly lower only in the dorsal striatum (p < .05) in the young rats. Tg rats had smaller striatal volumes on magnetic resonance imaging. We also found lower expression levels of tyrosine hydroxylase on immunohistochemistry in the Tg animals. Our findings suggest that progressive striatal D2/3 receptor deficits occur in Tg rats as they age and can be detected using small-animal PET imaging. The effectiveness of various approaches in preventing or halting this dopaminergic loss in the Tg rat can thus be measured preclinically using [18F]fallypride PET as a molecular imaging biomarker of HIV-associated neuropathology.
Subject(s)
Benzamides/pharmacokinetics , Brain/diagnostic imaging , HIV Infections/diagnostic imaging , Pyrrolidines/pharmacokinetics , Radiopharmaceuticals/pharmacokinetics , Animals , Biomarkers/analysis , Brain/metabolism , Disease Models, Animal , HIV Infections/metabolism , HIV Infections/pathology , HIV-1/physiology , Humans , Positron-Emission Tomography/methods , Rats , Rats, Transgenic , Receptors, Dopamine D2/analysis , Receptors, Dopamine D3/analysisABSTRACT
CD163, a monocyte- and macrophage-specific scavenger receptor, is shed during activation as soluble CD163 (sCD163). We have previously demonstrated that monocyte expansion from bone marrow with simian immunodeficiency virus (SIV) infection correlated with plasma sCD163, the rate of AIDS progression, and the severity of macrophage-mediated pathogenesis. Here, we examined sCD163 in human immunodeficiency virus (HIV) infection. sCD163 was elevated in the plasma of individuals with chronic HIV infection (>1 year in duration), compared with HIV-seronegative individuals. With effective antiretroviral therapy (ART), sCD163 levels decreased in parallel with HIV RNA levels but did not return to HIV-seronegative levels, suggesting the presence of residual monocyte/macrophage activation even with plasma viral loads below the limit of detection. In individuals with early HIV infection (≤1 year in duration), effective ART resulted in decreased sCD163 levels that were comparable to levels in HIV-seronegative individuals. sCD163 levels in plasma were positively correlated with the percentage of CD14+CD16+ monocytes and activated CD8+HLA-DR+CD38+ T lymphocytes and were inversely correlated with CD163 expression on CD14+CD16+ monocytes. With ART interruption in subjects with early HIV infection, sCD163 and plasma virus levels spiked but rapidly returned to baseline with reinitiation of ART. This study points to the utility of monocyte- and macrophage-derived sCD163 as a marker of HIV activity that links viral replication with monocyte and macrophage activation. These observations underscore the significance of monocyte and macrophage immune responses with HIV pathogenesis.
Subject(s)
Antigens, CD/blood , Antigens, Differentiation, Myelomonocytic/blood , Biomarkers/blood , HIV Infections/immunology , Macrophages/metabolism , Monocytes/metabolism , Receptors, Cell Surface/blood , Adult , Anti-HIV Agents/administration & dosage , Chronic Disease , Female , HIV Infections/drug therapy , Humans , Male , Middle Aged , Plasma/chemistry , RNA, Viral/blood , Viral LoadABSTRACT
Proton magnetic resonance spectroscopy has emerged as one of the most informative neuroimaging modalities for studying the effect of HIV infection in the brain, providing surrogate markers by which to assess disease progression and monitor treatment. Reductions in the level of N-Acetylaspartate and N-Acetylaspartate/creatine are established markers of neuronal injury or loss. However, the biochemical basis of altered creatine levels in neuroAIDS is not well understood. This study used a rapid progression macaque model of neuroAIDS to elucidate the changes in creatine. As the disease progressed, proton magnetic resonance spectroscopy revealed a decrease in N-Acetylaspartate, indicative of neuronal injury, and an increase in creatine yet to be elucidated. Subsequently, immunohistochemistry and stereology measures of decreased synaptophysin, microtubule-associated protein 2, and neuronal density confirmed neuronal injury. Furthermore, increases in ionized calcium binding adaptor molecule 1 and glial fibrillary acidic protein indicated microglial and astroglial activation, respectively. Given these data, elevated creatine may reflect enhanced high-energy phosphate turnover in highly metabolizing activated astrocytes and microglia.
Subject(s)
Brain/metabolism , Creatine/metabolism , Energy Metabolism , Magnetic Resonance Imaging/methods , Magnetic Resonance Spectroscopy/methods , Neurons/metabolism , Simian Acquired Immunodeficiency Syndrome/metabolism , Analysis of Variance , Animals , Aspartic Acid/analogs & derivatives , Aspartic Acid/metabolism , Brain/pathology , CD8-Positive T-Lymphocytes , Choline/metabolism , Flow Cytometry , Immunohistochemistry , Inositol/metabolism , Macaca , Male , Neurons/pathology , Simian Acquired Immunodeficiency Syndrome/pathology , Viral LoadABSTRACT
Migration of both uninfected and infected monocytes into the brain during acute HIV infection likely initiates metabolic changes that can be observed with magnetic resonance spectroscopy (MRS). Herein, we measured changes in brain metabolism during the first year of HIV infection and examined the relationship of these metabolite levels to CD16+ monocyte populations measured in the blood. MRS was performed on nine HIV+ subjects identified during acute HIV infection and nine seronegative control subjects. HIV+ subjects were examined within 90 days of an indeterminate Western blot, then again 2 and 6 months later, during early infection. Blood samples were collected for plasma viral RNA and monocyte subset quantification. HIV+ subjects were identified with acute viral ailment and did not display severe cognitive deficits such as dementia or minor cognitive motor disorder. Changes in lipid membrane metabolism (choline levels) in the frontal cortex and white matter were observed during the initial year of HIV infection. Greater numbers of CD16+ monocytes were associated with lower N-acetylaspartate levels and higher choline levels in the brain. These results suggest that HIV infection induces metabolic changes in the brain early during infection and that these changes may be related to monocyte dynamics in the periphery.
Subject(s)
Basal Ganglia/metabolism , Frontal Lobe/metabolism , HIV Infections/blood , Monocytes/metabolism , Adult , Anti-Retroviral Agents/therapeutic use , Aspartic Acid/analogs & derivatives , Aspartic Acid/blood , Basal Ganglia/pathology , Basal Ganglia/virology , Choline/blood , Frontal Lobe/pathology , Frontal Lobe/virology , GPI-Linked Proteins/analysis , HIV/physiology , HIV Infections/drug therapy , HIV Infections/pathology , HIV Infections/virology , Humans , Inositol/blood , Lipid Metabolism , Lipopolysaccharide Receptors/analysis , Longitudinal Studies , Magnetic Resonance Spectroscopy , Middle Aged , Monocytes/pathology , RNA, Viral/analysis , Receptors, IgG/analysis , Viral LoadABSTRACT
Understanding the mechanisms of neuronal regeneration and repair in the adult central nervous system is a vital area of research. Using a rhesus lentiviral encephalitis model, we sought to determine whether recovery of neuronal metabolism after injury coincides with the induction of two important markers of synaptodendritic repair: growth-associated protein-43 (GAP-43) and ephrin B3. We examined whether the improvement of neuronal metabolism with combined anti-retroviral therapy (cART) after simian immunodeficiency virus (SIV) infection in rhesus macaques involved induction of GAP-43, also known as neuromodulin, and ephrin B3, both implicated in axonal pathfinding during neurodevelopment and regulation of synapse formation, neuronal plasticity, and repair in adult brain. We utilized magnetic resonance spectroscopy to demonstrate improved neuronal metabolism in vivo in adult SIV-infected cART animals compared to untreated and uninfected controls. We then assessed levels of GAP-43, ephrin B3, and synaptophysin, a pre-synaptic marker, in three brain regions important for cognitive function, cortex, hippocampus, and putamen, by quantitative real-time RT-PCR and immunohistochemistry. Here we demonstrate that (1) GAP-43 mRNA and protein are induced with SIV infection, (2) GAP-43 protein is higher in the hippocampus outer molecular layer in SIV-infected animals that received cART compared to those that did not, and (3) activated microglia and infiltrating SIV-infected macrophages express abundant ephrin B3, an important axonal guidance molecule. We propose a model whereby SIV infection triggers events that lead to induction of GAP-43 and ephrin B3, and that short-term cART results in increased magnitude of repair mechanisms especially in the hippocampus, a region known for high levels of adult plasticity.
Subject(s)
Brain/metabolism , Ephrin-B3/metabolism , GAP-43 Protein/metabolism , Simian Acquired Immunodeficiency Syndrome/pathology , Animals , Anti-Retroviral Agents/therapeutic use , Brain/pathology , Brain/virology , Hippocampus/metabolism , Macaca mulatta/metabolism , Macaca mulatta/virology , Macrophages/metabolism , Microglia/metabolism , Neuronal Plasticity , RNA, Messenger/metabolism , Simian Acquired Immunodeficiency Syndrome/drug therapy , Simian Acquired Immunodeficiency Syndrome/virology , Simian Immunodeficiency Virus/pathogenicity , Synaptophysin/metabolismABSTRACT
PURPOSE: To develop a relevant pathophysiologic model of human immunodeficiency virus (HIV)-associated dementia by studying regional variations in metabolite levels measured with magnetic resonance (MR) spectroscopic imaging and their relationship to immunologic measures and cognitive dysfunction. MATERIALS AND METHODS: This was a HIPAA-compliant, institutional review board-approved study involving written informed consent. Distributions of N-acetylaspartate (NAA), choline (Cho), and creatine (Cr) concentrations in 94 subjects (20 seronegative controls and 74 HIV-positive subjects; 34 of the HIV-positive subjects having HIV-associated dementia; 63 men, 31 women; mean age, 40 years) were determined with proton (hydrogen 1 [(1)H]) MR spectroscopic imaging. HIV-positive subjects underwent neuropsychological testing and blood and cerebrospinal fluid (CSF) analysis. Factor analysis was utilized to determine associations between metabolites across regions. Analysis of variance and t tests were used to isolate differences between cohorts. RESULTS: A "Cho factor" differentiated seronegative controls from HIV-infected cohorts, indicating elevated Cho levels across deep gray and white matter regions of HIV-positive individuals. An "NAA factor" differentiated those with dementia from those without and correlated best with psychomotor and executive function tests. A "Cr factor" indicated Cr elevations correlated with CSF monocyte chemoattractant protein-1 levels. NAA and Cr factor scores were strongly weighted to metabolite changes in white matter regions. CONCLUSION: These results highlight the importance of white matter involvement in HIV-associated dementia and support the current pathogenesis model of glial cell proliferation in HIV infection, denoted by regional Cho elevations, and neuronal dysfunction and/or death, denoted by NAA decreases, associated with dementia. Factor analysis of MR spectroscopic imaging data is a useful method for determining regional metabolic variations in HIV infection and its neuropsychological correlates.
Subject(s)
AIDS Dementia Complex/metabolism , HIV Infections/metabolism , Magnetic Resonance Spectroscopy , Adult , Analysis of Variance , Aspartic Acid/analogs & derivatives , Aspartic Acid/metabolism , Case-Control Studies , Chi-Square Distribution , Choline/metabolism , Creatine/metabolism , Factor Analysis, Statistical , Female , Humans , Male , Neuropsychological TestsABSTRACT
Macrophage colony-stimulating factor (M-CSF) promotes macrophage differentiation, increases susceptibility of macrophages to viral infection, and enhances human immunodeficiency virus (HIV) replication in infected macrophages. Given the current model of HIV neuropathogenesis, which involves monocyte trafficking into the central nervous system, immune factors linked with macrophage maturation and survival may be associated with cognitive decline (measured by neuropsychological z-score [NPZ-8] or Memorial Sloan-Kettering [MSK] score) and alterations in a marker of neuronal integrity, N-acetylaspartate (NAA). Fifty-four chronically infected HIV+ subjects underwent neuropsychological assessment, magnetic resonance spectroscopic imaging, and quantification of M-CSF in plasma and cerebrospinal fluid (CSF) at baseline. Thirty-nine of those subjects underwent further examination at 3 and 10 months after initiation of combination antiretroviral therapy (ART) regimens. Within 3 months of therapy use, CSF M-CSF and viral RNA levels were reduced, whereas NAA concentrations in many brain regions were increased. Neither baseline levels nor the change in M-CSF levels had the ability to predict changes in NAA levels observed after 10 months of combination ART use. At study entry those with the lowest M-CSF levels in the CSF had the least cognitive impairment (NPZ-8). Those who had higher baseline CSF M-CSF levels and exhibited larger decreases in M-CSF after therapy, tended to have greater cognitive improvement after 10 months. Increased prevalence of M-CSF in the setting of HIV infection could contribute to neuronal injury and may be predictive of cognitive impairment.
Subject(s)
AIDS Dementia Complex/drug therapy , AIDS Dementia Complex/psychology , Cognition , HIV-1 , Macrophage Colony-Stimulating Factor/metabolism , AIDS Dementia Complex/blood , AIDS Dementia Complex/cerebrospinal fluid , Adult , Anti-HIV Agents/therapeutic use , Antiretroviral Therapy, Highly Active , Aspartic Acid/analogs & derivatives , Aspartic Acid/analysis , Aspartic Acid/metabolism , Biomarkers/blood , Biomarkers/cerebrospinal fluid , Biomarkers/metabolism , Brain/metabolism , Chronic Disease , Cohort Studies , Female , Humans , Macrophage Colony-Stimulating Factor/blood , Macrophage Colony-Stimulating Factor/cerebrospinal fluid , Magnetic Resonance Spectroscopy , Male , Neuropsychological Tests , PrognosisABSTRACT
BACKGROUND: In vivo proton magnetic resonance spectroscopy (1H-MRS) studies of HIV-infected humans have demonstrated significant metabolic abnormalities that vary by brain region, but the causes are poorly understood. Metabolic changes in the frontal cortex, basal ganglia and white matter in 18 SIV-infected macaques were investigated using MRS during the first month of infection. RESULTS: Changes in the N-acetylaspartate (NAA), choline (Cho), myo-inositol (MI), creatine (Cr) and glutamine/glutamate (Glx) resonances were quantified both in absolute terms and relative to the creatine resonance. Most abnormalities were observed at the time of peak viremia, 2 weeks post infection (wpi). At that time point, significant decreases in NAA and NAA/Cr, reflecting neuronal injury, were observed only in the frontal cortex. Cr was significantly elevated only in the white matter. Changes in Cho and Cho/Cr were similar across the brain regions, increasing at 2 wpi, and falling below baseline levels at 4 wpi. MI and MI/Cr levels were increased across all brain regions. CONCLUSION: These data best support the hypothesis that different brain regions have variable intrinsic vulnerabilities to neuronal injury caused by the AIDS virus.
Subject(s)
Brain , Magnetic Resonance Spectroscopy , Protons , Simian Acquired Immunodeficiency Syndrome/pathology , Simian Immunodeficiency Virus , Animals , Aspartic Acid/analogs & derivatives , Aspartic Acid/metabolism , Brain/metabolism , Brain/pathology , Brain/virology , Brain Mapping , Choline/metabolism , Creatine/metabolism , Disease Models, Animal , Female , Inositol/metabolism , Macaca mulatta , Magnetic Resonance Imaging/methods , MaleABSTRACT
The success of antiretroviral therapy has reduced the incidence of severe neurological complication resulting from human immunodeficiency virus (HIV) infection. However, increased patient survival has been associated with an increased prevalence of protracted forms of HIV encephalitis leading to moderate cognitive impairment. NeuroAIDS remains a great challenge to patients, their families, and our society. Thus development of preclinical models that will be suitable for testing promising new compounds with neurotrophic and neuroprotective capabilities is of critical importance. The simian immunodeficiency virus (SIV)-infected macaque is the premiere model to study HIV neuropathogenesis. This model was central to the seminal work of Dr. Opendra "Bill" Narayan. Similar to patients with HIV encephalitis, in the SIV model there is injury to the synaptodendritic structure of excitatory pyramidal neurons and inhibitory calbindin-immunoreactive interneurons. This article, which is part of a special issue of the Journal of NeuroVirology in honor of Dr. Bill Narayan, discusses the most important neurodegenerative features in preclinical models of neuroAIDS and their potential for treatment development.
Subject(s)
Neurodegenerative Diseases/etiology , Simian Acquired Immunodeficiency Syndrome/complications , Simian Acquired Immunodeficiency Syndrome/physiopathology , Simian Immunodeficiency Virus/physiology , Animals , Disease Models, Animal , Encephalitis/etiology , HIV Infections/complications , Human Immunodeficiency Virus Proteins/metabolism , Humans , Magnetic Resonance Spectroscopy , Neurons/pathology , Simian Acquired Immunodeficiency Syndrome/virologyABSTRACT
INTRODUCTION: HIV infection is known to be associated with brain volume loss, even in optimally treated patients. In this study, we assessed whether dynamic brain volume changes over time are predictive of neurobehavorial performance in the HIV-1 transgenic (Tg) rat, a model of treated HIV-positive patients. MATERIALS AND METHODS: Cross-sectional brain MRI imaging was first performed comparing Tg and wild type (WT) rats at 3 and 19 months of age. Longitudinal MRI and neurobehavioral testing of another group of Tg and WT rats was then performed from 5 to 23 weeks of age. Whole brain and subregional image segmentation was used to assess the rate of brain growth over time. We used repeated-measures mixed models to assess differences in brain volumes and to establish how predictive the volume differences are of specific neurobehavioral deficits. RESULTS: Cross-sectional imaging showed smaller whole brain volumes in Tg compared to WT rats at 3 and at 19 months of age. Longitudinally, Tg brain volumes were smaller than age-matched WT rats at all time points, starting as early as 5 weeks of age. The Tg striatal growth rate delay between 5 and 9 weeks of age was greater than that of the whole brain. Striatal volume in combination with genotype was the most predictive of rota-rod scores and in combination with genotype and age was the most predictive of total exploratory activity scores in the Tg rats. CONCLUSION: The disproportionately delayed striatal growth compared to whole brain between 5 and 9 weeks of age and the role of striatal volume in predicting neurobehavioral deficits suggest an important role of the dopaminergic system in HIV associated neuropathology. This might explain problems with motor coordination and executive decisions in this animal model. Smaller brain and subregional volumes and neurobehavioral deficits were seen as early as 5 weeks of age, suggesting an early brain insult in the Tg rat. Neuroprotective therapy testing in this model should thus target this early stage of development, before brain damage becomes irreversible.
Subject(s)
Brain/pathology , HIV Infections/complications , HIV Infections/pathology , Mental Disorders/etiology , Mental Disorders/pathology , Animals , Behavior, Animal , HIV-1 , Magnetic Resonance Imaging , Male , Rats , Rats, TransgenicABSTRACT
Nipah virus (NiV) infection can lead to severe respiratory or neurological disease in humans. Transmission of NiV has been shown to occur through contact with virus contaminated fomites or consumption of contaminated food. Previous results using the African green monkey (AGM) model of NiV infection identified aspects of infection that, while similar to humans, don't fully recapitulate disease. Previous studies also demonstrate near uniform lethality that is not consistent with human NiV infection. In these studies, aerosol exposure using an intermediate particle size (7µm) was used to mimic potential human exposure by facilitating virus deposition in the upper respiratory tract. Computed tomography evaluation found some animals developed pulmonary parenchymal disease including consolidations, ground-glass opacities, and reactive adenopathy. Despite the lack of neurological signs, magnetic resonance imaging identified distinct brain lesions in three animals, similar to those previously reported in NiV-infected patients. Immunological characterization of tissues collected at necropsy suggested a local pulmonary inflammatory response with increased levels of macrophages in the lung, but a limited neurologic response. These data provide the first clear evidence of neurological involvement in the AGM that recapitulates human disease. With the development of a disease model that is more representative of human disease, these data suggest that NiV infection in the AGM may be appropriate for evaluating therapeutic countermeasures directed at virus-induced neuropathogenesis.
Subject(s)
Aerosols/adverse effects , Henipavirus Infections/virology , Nervous System Diseases/virology , Nipah Virus/physiology , Aerosols/chemistry , Animals , Chlorocebus aethiops , Cytokines/genetics , Cytokines/immunology , Disease Models, Animal , Female , Henipavirus Infections/genetics , Henipavirus Infections/immunology , Humans , Lung/immunology , Lung/virology , Male , Nervous System Diseases/etiology , Nervous System Diseases/genetics , Nervous System Diseases/immunology , Nipah Virus/chemistry , Particle Size , Respiratory Tract Infections/etiology , Respiratory Tract Infections/genetics , Respiratory Tract Infections/immunology , Respiratory Tract Infections/virologyABSTRACT
Nipah virus (NiV) is a paramyxovirus (genus Henipavirus) that emerged in the late 1990s in Malaysia and has since been identified as the cause of sporadic outbreaks of severe febrile disease in Bangladesh and India. NiV infection is frequently associated with severe respiratory or neurological disease in infected humans with transmission to humans through inhalation, contact or consumption of NiV contaminated foods. In the work presented here, the development of disease was investigated in the African Green Monkey (AGM) model following intratracheal (IT) and, for the first time, small-particle aerosol administration of NiV. This study utilized computed tomography (CT) and magnetic resonance imaging (MRI) to temporally assess disease progression. The host immune response and changes in immune cell populations over the course of disease were also evaluated. This study found that IT and small-particle administration of NiV caused similar disease progression, but that IT inoculation induced significant congestion in the lungs while disease following small-particle aerosol inoculation was largely confined to the lower respiratory tract. Quantitative assessment of changes in lung volume found up to a 45% loss in IT inoculated animals. None of the subjects in this study developed overt neurological disease, a finding that was supported by MRI analysis. The development of neutralizing antibodies was not apparent over the 8-10 day course of disease, but changes in cytokine response in all animals and activated CD8+ T cell numbers suggest the onset of cell-mediated immunity. These studies demonstrate that IT and small-particle aerosol infection with NiV in the AGM model leads to a severe respiratory disease devoid of neurological indications. This work also suggests that extending the disease course or minimizing the impact of the respiratory component is critical to developing a model that has a neurological component and more accurately reflects the human condition.
Subject(s)
Brain/pathology , Henipavirus Infections/immunology , Immunity, Cellular , Lung/pathology , Aerosols , Animals , Brain/virology , CD8-Positive T-Lymphocytes/immunology , Chlorocebus aethiops/virology , Cytokines/blood , Disease Models, Animal , Disease Progression , Female , Henipavirus Infections/veterinary , Humans , Lung/virology , Magnetic Resonance Imaging , Male , Nipah Virus , RNA, Viral/analysis , Tomography, X-Ray ComputedABSTRACT
Medical imaging using animal models for human diseases has been utilized for decades; however, until recently, medical imaging of diseases induced by high-consequence pathogens has not been possible. In 2014, the National Institutes of Health, National Institute of Allergy and Infectious Diseases, Integrated Research Facility at Fort Detrick opened an Animal Biosafety Level 4 (ABSL-4) facility to assess the clinical course and pathology of infectious diseases in experimentally infected animals. Multiple imaging modalities including computed tomography (CT), magnetic resonance imaging, positron emission tomography, and single photon emission computed tomography are available to researchers for these evaluations. The focus of this article is to describe the workflow for safely obtaining a CT image of a live guinea pig in an ABSL-4 facility. These procedures include animal handling, anesthesia, and preparing and monitoring the animal until recovery from sedation. We will also discuss preparing the imaging equipment, performing quality checks, communication methods from "hot side" (containing pathogens) to "cold side," and moving the animal from the holding room to the imaging suite.
Subject(s)
Containment of Biohazards , Laboratories , Safety , Tomography, X-Ray Computed , Anesthesia/veterinary , Animal Welfare , Animals , Disease Models, Animal , Guinea Pigs , Humans , Magnetic Resonance Imaging , Positron-Emission TomographyABSTRACT
BACKGROUND AND PURPOSE: In vivo 1H MR spectroscopy demonstrates elevated choline (Cho)/creatine (Cr) and myo-inositol (MI)/Cr in many neurologic diseases that has been ascribed to gliosis. We tested the hypotheses that in vivo Cho/Cr and/or MI/Cr levels are correlated with glial fibrillary acidic protein (GFAP) immunostains and that the changes are water-soluble metabolites. METHODS: We performed postmortem 1H MR spectroscopy and GFAP immunohistochemistry in brains from seven rhesus macaques acutely infected with simian immunodeficiency virus (SIV) and in four controls and compared the findings with previous in vivo MR spectroscopic results. Changes in neuropathologic and MR spectroscopic markers after infection and relationships among plasma viral load, GFAP immunostaining results, and ex vivo and in vivo MR spectroscopic measures were statistically evaluated. RESULTS: On GFAP immunostaining and in vivo MR spectroscopy, GFAP, Cho/Cr and MI/Cr were highest near the time of peak plasma viral load at 11 days postinfection (dpi). Immunostains returned to baseline by 14 dpi, whereas Cho/Cr and MI/Cr had different time courses, with the former dropping below baseline and the latter remaining elevated. Viral load and immunostains were significantly correlated. No correlation was found between ex vivo Cho/Cr or MI/Cr and viral load or between metabolite ratios from in vivo and ex vivo MR spectroscopy. CONCLUSION: In acute SIV infection, plasma viral load was significantly correlated with brain GFAP immunostains and in vivo 1H MR spectroscopic Cho/Cr. In vivo changes in Cho/Cr and MI/Cr were principally due to contributions other than those of low-molecular-weight water-soluble metabolites.
Subject(s)
Choline/analysis , Creatine/analysis , Disease Models, Animal , Glial Fibrillary Acidic Protein/analysis , Gliosis/metabolism , Inositol/analysis , Magnetic Resonance Spectroscopy , Simian Acquired Immunodeficiency Syndrome/metabolism , Animals , Hydrogen , Macaca mulattaABSTRACT
BACKGROUND: The neurological complications of HIV infection remain poorly understood. Clinically, in vivo 1H magnetic resonance spectroscopy (MRS) demonstrates brain injury caused by HIV infection even when the MRI is normal. Our goal was to undertsand the dynamics of cerebral injury by performing a longitudinal in vivo 1H MRS study of the SIV/macaque model of neuroAIDS. RESULTS: Eight rhesus macaques were infected with SIVmac251 and serially imaged with MRI and 1H MRS to terminal AIDS or the endpoint of 2 years. During acute infection, there were stereotypical brain MRS changes, dominated by a significant elevation of the Cho/Cr ratio in the frontal cortex. Subsequently, brain metabolic patterns diverged between animals. There was an elevation of basal ganglia Cho/Cr four weeks post-inoculation in 2 animals that developed SIV encephalitis (p = 0.022). Metabolite ratios averaged across all 8 animals were not significantly different from baseline at any time point after 2 weeks post inoculation. However, linear regression analysis on all 8 animals revealed a positive correlation between a change in frontal lobe Cho/Cr and plasma viral load (P < 0.001, R = 0.80), and a negative correlation between NAA/Cr in the basal ganglia and the plasma viral load (P < 0.02, R = -0.73). No MRI abnormalities were detected at any time. CONCLUSIONS: After infection with SIV, macaque brain metabolism changes in a complex manner that is dependent on brain region, host factors and viral load. An elevation of basal ganglia Cho/Cr 4 weeks after SIV infection may be marker of a propensity to develop SIV encephalitis. Elevations of Cho/Cr, often observed in CNS inflammation, were associated with increased plasma viral load during acute and chronic infection. Evidence of neuronal injury in the basal ganglia was associated with increased plasma viral load in the chronic stage of infection. These observations support the use of drugs capable of controlling the viral replication and trafficking of virus into the CNS, and may help explain the reduction in incidence of HIV-associated dementia in the era of HAART despite the inability of most of those drugs to effectively enter the CNS.
Subject(s)
AIDS Dementia Complex/diagnosis , Aspartic Acid/analogs & derivatives , Brain/metabolism , Magnetic Resonance Spectroscopy , Simian Acquired Immunodeficiency Syndrome/metabolism , Simian Immunodeficiency Virus/pathogenicity , AIDS Dementia Complex/complications , AIDS Dementia Complex/pathology , Acute Disease , Animals , Aspartic Acid/blood , Aspartic Acid/metabolism , Brain/pathology , Choline/blood , Choline/metabolism , Chronic Disease , Creatine/blood , Creatine/metabolism , Disease Models, Animal , Disease Progression , Female , Inositol/blood , Inositol/metabolism , Longitudinal Studies , Macaca mulatta , Male , Predictive Value of Tests , Prospective Studies , Simian Acquired Immunodeficiency Syndrome/complications , Simian Acquired Immunodeficiency Syndrome/virology , Survival Rate , Viral LoadABSTRACT
BACKGROUND: There are currently no widely accepted neuro-HIV small animal models. We wanted to validate the HIV-1 Transgenic rat (Tg) as an appropriate neuro-HIV model and then establish in vivo imaging biomarkers of neuropathology, within this model, using MR structural and diffusion tensor imaging (DTI). METHODS: Young and middle-aged Tg and control rats were imaged using MRI. A subset of middle-aged animals underwent longitudinal repeat imaging six months later. Total brain volume (TBV), ventricular volume (VV) and parenchymal volume (PVâ=âTBV-VV) were measured. Fractional anisotropy (FA) and mean diffusivity (MD) values of the corpus callosum (CC) were calculated from DTI data. RESULTS: TBV and PV were smaller in Tg compared to control rats in young and middle-aged cohorts (p<0.0001). VV increased significantly (pâ=â0.005) over time in the longitudinal Tg cohort. There were lower FA (p<0.002) and higher MD (p<0.003) values in the CC of middle-aged Tg rats compared to age-matched controls. Longitudinally, MD significantly decreased over time in Tg rats (p<0.03) while it did not change significantly in the control cohort over the same period of time (p>0.05). CONCLUSIONS: We detected brain volume loss in the Tg rat, probably due to astrocytic dysfunction/loss, loss of structural/axonal matrix and striatal neuronal loss as suggested by immunofluorescence. Increased MD and decreased FA in the CC probably reflect microstructural differences between the Tg and Control rats which could include increased extracellular space between white matter tracts, demyelination and axonal degeneration, among other pathologies. We believe that the Tg rat is an adequate model of neuropathology in HIV and that volumetric MR and DTI measures can be potentially used as biomarkers of disease progression.
Subject(s)
Brain Injuries/pathology , Corpus Callosum/pathology , HIV Infections/pathology , HIV-1 , Neuroimaging , Animals , Biomarkers/metabolism , Brain Injuries/metabolism , Corpus Callosum/metabolism , Disease Models, Animal , HIV Infections/metabolism , Humans , Rats , Rats, Inbred F344 , Rats, TransgenicABSTRACT
BACKGROUND: Despite the advent of highly active anti-retroviral therapy (HAART), HIV-associated neurocognitive disorders continue to be a significant problem. In efforts to understand and alleviate neurocognitive deficits associated with HIV, we used an accelerated simian immunodeficiency virus (SIV) macaque model of NeuroAIDS to test whether minocycline is neuroprotective against lentiviral-induced neuronal injury. METHODOLOGY/PRINCIPAL FINDINGS: Eleven rhesus macaques were infected with SIV, depleted of CD8+ lymphocytes, and studied until eight weeks post inoculation (wpi). Seven animals received daily minocycline orally beginning at 4 wpi. Neuronal integrity was monitored in vivo by proton magnetic resonance spectroscopy and post-mortem by immunohistochemistry for synaptophysin (SYN), microtubule-associated protein 2 (MAP2), and neuronal counts. Astrogliosis and microglial activation were quantified by measuring glial fibrillary acidic protein (GFAP) and ionized calcium binding adaptor molecule 1 (IBA-1), respectively. SIV infection followed by CD8+ cell depletion induced a progressive decline in neuronal integrity evidenced by declining N-acetylaspartate/creatine (NAA/Cr), which was arrested with minocycline treatment. The recovery of this ratio was due to increases in NAA, indicating neuronal recovery, and decreases in Cr, likely reflecting downregulation of glial cell activation. SYN, MAP2, and neuronal counts were found to be higher in minocycline-treated animals compared to untreated animals while GFAP and IBA-1 expression were decreased compared to controls. CSF and plasma viral loads were lower in MN-treated animals. CONCLUSIONS/SIGNIFICANCE: In conclusion, oral minocycline alleviates neuronal damage induced by the AIDS virus.
Subject(s)
AIDS-Associated Nephropathy/prevention & control , Disease Models, Animal , Macaca mulatta/virology , Minocycline/administration & dosage , Minocycline/therapeutic use , Neuroprotective Agents/therapeutic use , Simian Acquired Immunodeficiency Syndrome/drug therapy , AIDS-Associated Nephropathy/complications , Administration, Oral , Animals , Biomarkers/metabolism , CD8-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/virology , Cohort Studies , DNA-Binding Proteins/metabolism , Humans , Lymphocyte Depletion , Magnetic Resonance Spectroscopy , Male , Microglia/pathology , Microglia/virology , Minocycline/pharmacology , Neurons/drug effects , Neurons/pathology , Neurons/virology , Neuroprotective Agents/administration & dosage , Neuroprotective Agents/pharmacology , Protons , Simian Acquired Immunodeficiency Syndrome/blood , Simian Acquired Immunodeficiency Syndrome/cerebrospinal fluid , Simian Acquired Immunodeficiency Syndrome/complications , Simian Acquired Immunodeficiency Syndrome/virology , Viral LoadABSTRACT
Due to the overall similarity of their brains' structure and physiology to its human counterpart, nonhuman primates provide excellent model systems for the pathogenesis of neurological diseases and their response to treatments. Its much smaller size, 80 versus 1250 cm(3), however, requires proportionally higher spatial resolution to study, nondestructively, as many analogous regions as efficiently as possible in anesthetized animals. The confluence of these requirements underscores the need for the highest sensitivity, spatial coverage, resolution, and exam speed. Accordingly, we demonstrate the feasibility of 3D multi-voxel, proton ((1)H) MRSI at (0.375 cm)(3)=0.05 cm(3) isotropic spatial resolution over 21 cm(3) (approximately 25%) of the anesthetized rhesus macaques brain at 7T in 25 min. These voxels are x10(2)-10(1) times smaller than the 8-1 cm(3) common to (1)H-MRS in humans, retaining similar proportions between the macaque and human brain. The spectra showed a signal-to-noise-ratio (SNR) approximately 9-10 for the major metabolites and the interanimal SNR spatial distribution reproducibility was in the +/-10% range for the standard error of their means (SEMs). Their metabolites' linewidths, 9+/-2 Hz, yield excellent spectral resolution as well. These results indicate that 3D (1)H-MRSI can be integrated into comprehensive MR studies in primates at such high fields.
Subject(s)
Brain/anatomy & histology , Brain/metabolism , Image Interpretation, Computer-Assisted/methods , Imaging, Three-Dimensional/methods , Magnetic Resonance Imaging/methods , Magnetic Resonance Spectroscopy/methods , Protons , Algorithms , Animals , Feasibility Studies , Image Enhancement/methods , Macaca mulatta , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
In vivo MR spectroscopy (MRS) studies have shown reductions in NAA/Cr levels in patients with severe neurocognitive deficits due to AIDS dementia complex (ADC), also known as neuroAIDS. The relationship between the cellular changes within the brain during neuroAIDS and the role of NAA/Cr as a metabolic marker remains unclear. In order to clarify the relationship between NAA/Cr and disease severity we utilized the simian immunodeficiency virus (SIV)/macaque model of encephalitis. High-field proton MRS was performed on extracted metabolites from frontal cortex tissue samples of 29 rhesus macaques (6 healthy, 23 moribund with AIDS). Neuropathologic determination of encephalitis severity for each animal was completed and was found to correlate with NAA/Cr levels. Decreases in Glu/Cr and GABA/Cr may indicate that both excitatory and inhibitory neurons are affected. Highly significant correlations between NAA/Cr, Glu/Cr, and GABA/Cr were observed. These neuronal metabolites were also decreased in the absence of classical SIV encephalitis (SIVE). At any disease classification, animals inoculated with SIVmac251 were found to have lower levels of NAA/Cr than animals inoculated with SIVmac239. In considering therapy for neuroAIDS the findings here support prevention of the encephalitic process, but suggest that suppressing the formation of multinucleated giant cells alone would be insufficient to prevent neuronal injury.