ABSTRACT
Methamphetamine (Meth) abuse increases risky behaviors that contribute to the spread of HIV infection. In addition, because HIV and Meth independently affect physiological systems including the central nervous system, HIV-induced disease may be more severe in drug users. We investigated changes in blood and brain viral load as well as differences in immune cells in chronically simian immunodeficiency virus-infected rhesus macaques that were either administered Meth or used as controls. Although Meth administration did not alter levels of virus in the plasma, viral load in the brain was significantly increased in Meth-treated animals compared with control animals. Meth treatment also resulted in an activation of natural killer cells. Given the prevalence of Meth use in HIV-infected and HIV at-risk populations, these findings reveal the likely untoward effects of Meth abuse in such individuals.
Subject(s)
Brain , Killer Cells, Natural , Macaca mulatta , Methamphetamine/pharmacology , Simian Acquired Immunodeficiency Syndrome , Simian Immunodeficiency Virus/immunology , Viral Load , Animals , Brain/drug effects , Brain/virology , HIV/drug effects , HIV Infections/virology , Humans , Killer Cells, Natural/drug effects , Killer Cells, Natural/immunology , Killer Cells, Natural/virology , Macaca mulatta/immunology , Macaca mulatta/virology , Simian Acquired Immunodeficiency Syndrome/immunology , Simian Acquired Immunodeficiency Syndrome/virology , Substance-Related DisordersABSTRACT
Drug addiction is a chronic relapsing disorder of compulsive drug use. Studies of the neurobehavioral factors that promote drug relapse have yet to produce an effective treatment. Here we take a different approach and examine the factors that suppress-rather than promote-relapse. Adapting Pavlovian procedures to suppress operant drug response, we determined the anti-relapse action of environmental cues that signal drug omission (unavailability) in rats. Under laboratory conditions linked to compulsive drug use and heightened relapse risk, drug omission cues suppressed three major modes of relapse-promotion (drug-predictive cues, stress, and drug exposure) for cocaine and alcohol. This relapse-suppression is, in part, driven by omission cue-reactive neurons, which constitute small subsets of glutamatergic and GABAergic cells, in the infralimbic cortex. Future studies of such neural activity-based cellular units (neuronal ensembles/memory engram cells) for relapse-suppression can be used to identify alternate targets for addiction medicine through functional characterization of anti-relapse mechanisms.
Subject(s)
Cocaine/pharmacology , Conditioning, Operant/drug effects , Cues , Neurons/physiology , Prefrontal Cortex/drug effects , Alcoholism/physiopathology , Alcoholism/prevention & control , Animals , Cocaine/administration & dosage , Compulsive Behavior/physiopathology , Compulsive Behavior/prevention & control , Conditioning, Operant/physiology , Dopamine Uptake Inhibitors/pharmacology , Male , Prefrontal Cortex/physiopathology , Rats, Long-Evans , Rats, Sprague-Dawley , Rats, Transgenic , Recurrence , Substance-Related Disorders/physiopathology , Substance-Related Disorders/prevention & controlABSTRACT
Previous work has demonstrated that the surface glycoprotein (gp120) of human immunodeficiency virus-1 (HIV-1) can induce damage and apoptosis of neurons both in vitro and in vivo. In this report, we provide evidence that double-stranded RNA-activated protein kinase (PKR), a stress kinase, is involved in HIV/gp120-associated neurodegeneration. In cultures of mixed cortical cells, HIV/gp120 increased the protein level of PKR. Additionally, PKR was phosphorylated in neurons but not glia after exposure to gp120. The use of two independent pharmacological inhibitors of PKR activity abrogated neuronal cell death induced by gp120. Cortical neurons from PKR knock-out mice were significantly protected from neurotoxicity induced by gp120, further validating the pivotal proapoptotic function of PKR. gp120-induced phosphorylated PKR localized prominently to neuronal nuclei; PKR inhibition or the NMDA receptor antagonist MK-801 [(+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine maleate] abrogated this effect. PKR inactivation also inhibited gp120-induced caspase-3 activation, consistent with its neuroprotective effect. Finally, brain tissue from individuals diagnosed with HIV-associated dementia (HAD), but not HIV infection alone, contained the activated form of PKR, which localized predominantly to neuronal nuclei. Together, these results identify PKR as a critical mediator of gp120 neurotoxicity, suggesting that activation of PKR contributes to the neuronal injury and cell death observed in HAD.
Subject(s)
Apoptosis/physiology , HIV Envelope Protein gp120/physiology , HIV-1/physiology , Neurons/enzymology , Neurons/virology , Signal Transduction/physiology , eIF-2 Kinase/physiology , AIDS Dementia Complex/enzymology , AIDS Dementia Complex/pathology , AIDS Dementia Complex/virology , Adult , Animals , Cells, Cultured , Humans , Mice , Mice, Inbred C57BL , Mice, Knockout , Middle Aged , Neurons/pathology , Rats , Rats, Sprague-Dawley , eIF-2 Kinase/deficiency , eIF-2 Kinase/geneticsABSTRACT
In order to assess the role of osteopontin (OPN) in leukocyte accumulation in inflammatory conditions, native OPN and its thrombin cleaved form (OPN+Thr) were studied in vivo using a rodent subcutaneous air pouch model (AP). Both forms of OPN-induced macrophage infiltration into the AP in wild-type mice. In animals lacking CD44, macrophage numbers were significantly reduced within the cavity, but cells still accumulated along the subcutaneous lining. In animals lacking endogenous OPN, no differences were found in exogenous OPN-induced macrophage accumulation, although macrophage exhibited increased alpha4 integrin expression. These studies reveal that both OPN and OPN+Thr attract macrophages in vivo through CD44.
Subject(s)
Chemotaxis, Leukocyte/immunology , Hyaluronan Receptors/biosynthesis , Macrophages/immunology , Osteopontin/immunology , Animals , Blotting, Western , Cell Adhesion/immunology , Flow Cytometry , Immunohistochemistry , Macrophages/metabolism , Mice , Osteopontin/metabolismABSTRACT
BACKGROUND: Alcohol consumption is a common problem in HIV-infected individuals, and the effects of alcohol may alter the efficiency of the immune response, potentially aggravating the disease as well as affecting end organs, such as the brain. However, the elements of the virus-host interaction that are modulated by ethanol are poorly dissected. METHODS: Ethanol intake was conditioned in rhesus macaques prior to SIV infection, in order to mimic this common human behavior, and allow the evaluation of aspects of the virus-immune system interactions during acute time-points, when important facets of the infection are set up and when virus reproducibly enters the brain. RESULTS: Although ethanol had a limited effect on the acute plasma viral load, it resulted in reduced circulating memory CD4(+) T cells and increased levels of monocytes expressing the viral coreceptor CCR5. In organs, ethanol consumption impacted immune cells in the liver as well as lymphoid and other nonlymphoid tissues, where CD4(+) T cells were predominantly affected. CONCLUSION: Overall, the consumption of alcohol causes immune cell alterations that can contribute to the generation of a disease susceptible environment upon SIV infection.
Subject(s)
Alcohol Drinking/immunology , Alcoholism/immunology , Immune System/physiopathology , Monkey Diseases/immunology , Monkey Diseases/virology , Simian Acquired Immunodeficiency Syndrome/immunology , Simian Immunodeficiency Virus/immunology , Animals , Brain/pathology , Brain/virology , Cytokines/metabolism , Disease Models, Animal , Disease Susceptibility/immunology , Killer Cells, Natural/pathology , Liver/pathology , Liver/virology , Macaca mulatta , Monkey Diseases/epidemiology , Risk Factors , Simian Acquired Immunodeficiency Syndrome/epidemiology , Simian Acquired Immunodeficiency Syndrome/pathology , Spleen/pathology , Spleen/virology , T-Lymphocytes/pathology , Viral LoadABSTRACT
Claudin-5 is a protein component of many endothelial tight junctions, including those at the blood-brain barrier, a barrier that limits molecular exchanges between the central nervous system and the circulatory system. To test the contribution of claudin-5 to this barrier function of tight junctions, we expressed murine claudin-5 in Madin-Darby canine kidney II cells. The result was a fivefold increase in transepithelial resistance in claudin-5 transductants and a reduction in conductance of monovalent cations. However, the paracellular flux of neither neutral nor charged monosaccharides was significantly changed in claudin-5 transductants compared to controls. Therefore, expression of claudin-5 selectively decreased the permeability to ions. Additionally, site-directed mutations of particular amino acid residues in the first extracellular domain of claudin-5 altered the properties of the tight junctions formed in response to claudin-5 expression. In particular, the conserved cysteines were crucial: mutation of either cysteine abolishted the ability of claudin-5 to increase transepithelial resistance, and mutation of Cys(64) strikingly increased the paracellular flux of monosaccharides. These new insights into the functions of claudin-5 at the molecular level in tight junctions may account for some aspects of the blood-brain barrier's selective permeability.
Subject(s)
Membrane Proteins/metabolism , Tight Junctions/metabolism , Amino Acid Sequence , Animals , Cysteine/genetics , Cysteine/metabolism , Mannitol/metabolism , Membrane Proteins/genetics , Mice , Microscopy, Confocal , Molecular Sequence Data , MutationABSTRACT
Facets of the immune response early after human immunodeficiency virus (HIV) infection influence the course of disease. In the simian immunodeficiency virus (SIV)-rhesus monkey system, a global dysfunction of CD4(+) T cell cytokine secretion was reported to develop early after infection [McKay PF, Barouch DH, Schmitz JE, Veazey RS, Gorgone DA, Lifton MA, Williams KC, and Letvin NL: J Virol 2003;77:4695-4702]. Because differences have been found in SIV pathogenesis depending on the origin of the monkeys, we investigated the correlation between animal background, defined by country of origin (India or China), and circulating T cell cytokine secretion as well as cycling ability within the first 3 mo of SIV infection. An early loss of CD4(+) T cells that produce interferon (IFN)-gamma and interleukin (IL)-2, those that produce IFN-gamma but not tumor necrosis factor (TNF)-alpha, as well as those that do not express IFN-gamma but can express IL-2 or TNF-alpha, was observed in animals of Indian, but not of Chinese, origin after SIV infection. After infection CD4(+) T cells in Chinese macaques developed an increased proliferating pool of T cells compared with Indian animals. These data reveal host diversity in the global effects of SIV infection on functional subsets of immune cells, which can add to a better understanding of differences observed in populations from diverse ethnic origins.
Subject(s)
CD4-Positive T-Lymphocytes/immunology , Cytokines/biosynthesis , Simian Acquired Immunodeficiency Syndrome/immunology , Simian Immunodeficiency Virus/immunology , Animals , China , India , Interferon-gamma/biosynthesis , Interleukin-2/biosynthesis , Lymphocyte Activation , Macaca mulatta , Species Specificity , Tumor Necrosis Factor-alpha/biosynthesisABSTRACT
Conflicting evidence exists regarding the role of infralimbic cortex (IL) in the environmental control of appetitive behavior. Inhibition of IL, irrespective of its intrinsic neural activity, attenuates not only the ability of environmental cues predictive of reward availability to promote reward seeking, but also the ability of environmental cues predictive of reward omission to suppress this behavior. Here we report that such bidirectional behavioral modulation in rats is mediated by functionally distinct units of neurons (neural ensembles) that are concurrently localized within the same IL brain area but selectively reactive to different environmental cues. Ensemble-specific neural activity is thought to function as a memory engram representing a learned association between environment and behavior. Our findings establish the causal evidence for the concurrent existence of two distinct engrams within a single brain site, each mediating opposing environmental actions on a learned behavior.
Subject(s)
Appetitive Behavior , Cerebral Cortex/physiology , Limbic Lobe/physiology , Memory , Animals , Association Learning , Cues , Neurons/physiology , Rats , RewardABSTRACT
HIV is found in the brains of most infected individuals but only 30% develop neurological disease. Both viral and host factors are thought to contribute to the motor and cognitive disorders resulting from HIV infection. Here, using the SIV/rhesus monkey system, we characterize the salient characteristics of the virus from the brain of animals with neuropathological disorders. Nine unique molecular clones of SIV were derived from virus released by microglia cultured from the brains of two macaques with SIV encephalitis. Sequence analysis revealed a remarkably high level of similarity between their env and nef genes as well as their 3' LTR. As this genotype was found in the brains of two separate animals, and it encoded a set of distinct amino acid changes from the infecting virus, it demonstrates the convergent evolution of the virus to a unique brain-adapted genotype. This genotype was distinct from other macrophage-tropic and neurovirulent strains of SIV. Functional characterization of virus derived from representative clones showed a robust in vitro infection of 174xCEM cells, primary macrophages and primary microglia. The infectious phenotype of this virus is distinct from that shown by other strains of SIV, potentially reflecting the method by which the virus successfully infiltrates and infects the CNS. Positive in vivo selection of a brain-adapted strain of SIV resulted in a near-homogeneous strain of virus with distinct properties that may give clues to the viral basis of neuroAIDS.
Subject(s)
Brain/virology , Simian Immunodeficiency Virus/physiology , Amino Acid Sequence , Animals , Cloning, Molecular , Cytopathogenic Effect, Viral , Gene Expression Regulation, Viral , Macaca mulatta , Macrophages/virology , Microglia/virology , Molecular Sequence Data , Simian Immunodeficiency Virus/genetics , Viral Regulatory and Accessory Proteins/chemistry , Viral Regulatory and Accessory Proteins/geneticsABSTRACT
The virus/host interactions during the acute phase of human immunodeficiency virus (HIV) infection help determine the course of disease. During this time period, virus enters the brain. Here, we report clusters of genes whose transcripts are significantly upregulated in the frontal lobe of the brain during acute simian immunodeficiency virus (SIV) infection of rhesus monkeys. Many of these genes are involved in interferon (IFN) and/or interleukin (IL)-6 pathways. Although neither IFNalpha nor IFNgamma are elevated in the brain, IL6 is increased. Both IFNalpha and IL6 are elevated in plasma during this acute phase. The upregulation of STAT1, verified by immunohistochemical staining, can be due to both central nervous system (CNS) (SIV and IL6) and peripheral (IFNalpha and IL6) causes, and can itself drive the expression of many of these genes. Examination of the levels of expression of the upregulated genes in the post-acute and long-term phases of infection, as well as in SIV encephalitis, reveals increased expression throughout SIV infection, which may serve to protect the brain, but can have untoward long-term consequences.
Subject(s)
Brain/virology , Interferons/metabolism , Interleukin-6/metabolism , Simian Acquired Immunodeficiency Syndrome/metabolism , Simian Immunodeficiency Virus/physiology , Analysis of Variance , Animals , Brain/metabolism , DNA-Binding Proteins/metabolism , Disease Progression , Enzyme-Linked Immunosorbent Assay/methods , Humans , Immunohistochemistry/methods , Interferons/genetics , Interleukin-6/genetics , Macaca mulatta , Oligonucleotide Array Sequence Analysis/methods , RNA, Messenger/metabolism , Reverse Transcriptase Polymerase Chain Reaction/methods , STAT1 Transcription Factor , Simian Acquired Immunodeficiency Syndrome/genetics , Simian Acquired Immunodeficiency Syndrome/virology , Time Factors , Trans-Activators/metabolism , Up-Regulation , Viral Load/methodsABSTRACT
OBJECTIVE: Neurocognitive disorders are devastating consequences of HIV infection. Although antiretroviral regimens have been efficacious in both improving life expectancy and decreasing dementia, there has not been an effect on the overall prevalence of HIV-associated neurocognitive disorders. Whether early institution of treatment, or treatment with drugs that effectively penetrate the blood-brain barrier, would help protect from such conditions is not known. Using the simian immunodeficiency virus/macaque model, we investigated the hypothesis that early introduction of antiretroviral treatment can protect the brain. DESIGN AND METHODS: Animals were inoculated with simian immunodeficiency virus, and upon resolution of the acute infection period divided into two groups and treated, or not, with combination antiretroviral therapy. Viral, immune, and physiological parameters were measured during the course of infection, followed by assessment of viral, immune, and molecular parameters in the brain. RESULTS: We observed that even with agents that show poor penetration into the central nervous system, early antiretroviral treatment prevented characteristic neurophysiological and locomotor alterations arising after infection and resulted in a significant decrease in brain viral load. Although the number of infiltrating immune cells in the brain did not change with treatment, their phenotype did, favoring an enrichment of effector T cells. Early treatment also significantly lowered brain levels of interferon-alpha, a cytokine that can lead to neurocognitive and behavioral alterations. CONCLUSION: Early antiretroviral treatment prevents central nervous system dysfunction by decreasing brain viral load and interferon-alpha levels, which can have a profound impact over the course of infection.
Subject(s)
AIDS Dementia Complex/prevention & control , Anti-HIV Agents/administration & dosage , Simian Acquired Immunodeficiency Syndrome/drug therapy , AIDS Dementia Complex/immunology , AIDS Dementia Complex/virology , Animals , Brain/immunology , Brain/virology , Drug Administration Schedule , Drug Evaluation, Preclinical/methods , Evoked Potentials, Auditory, Brain Stem/drug effects , Gene Expression Regulation/drug effects , Immunologic Memory/drug effects , Immunophenotyping , Lymphocyte Activation/drug effects , Macaca mulatta , Simian Acquired Immunodeficiency Syndrome/immunology , Simian Acquired Immunodeficiency Syndrome/virology , Simian Immunodeficiency Virus/isolation & purification , T-Lymphocyte Subsets/drug effects , Telemetry/methods , Viral LoadABSTRACT
In people infected with human immunodeficiency virus type 1 (HIV-1), the accumulation of macrophages in the brain correlates with encephalitis and dementia. We hypothesized that a pattern of surface marker expression in blood monocytes may serve as a marker for central nervous system (CNS) disease. Using the simian immunodeficiency virus (SIV)-rhesus monkey model, we analyzed functionally relevant surface markers on monocytes and macrophages from the blood and brain in animals that did or did not develop SIV encephalitis. At necropsy, multiple markers (CD44v6, CCR2, and CCR5 on blood monocytes and brain microglia and/or macrophages, and CX3CR1 on blood monocytes) allowed us to distinguish animals with encephalitis from those without. Furthermore, the level of expression of CD44v6 on the 2 main populations of blood monocytes--those that express either low or high levels of CD16--was significantly increased in animals with encephalitis. A longitudinal analysis of blood monocyte markers revealed that as early as 28 days after inoculation, CD44v6 staining could distinguish the 2 groups. This provides a potential peripheral biomarker to identify individuals who may develop the HIV-induced CNS disease. Furthermore, given its role in cellular adhesion and as an osteopontin receptor, CD44v6 upregulation on monocytes offers functional clues to the pathogenesis of such complications, and provides a target for preventative and therapeutic measures.
Subject(s)
Encephalitis/virology , Hyaluronan Receptors/biosynthesis , Monocytes/immunology , Simian Acquired Immunodeficiency Syndrome/complications , Simian Immunodeficiency Virus/immunology , Animals , Biomarkers , Blood/immunology , Brain/immunology , Brain/pathology , Brain/virology , Encephalitis/immunology , Flow Cytometry , Longitudinal Studies , Macaca mulatta , Simian Acquired Immunodeficiency Syndrome/immunologyABSTRACT
OBJECTIVES: Defects in memory CD4+ T cells correlate with development of AIDS in monkeys infected with simian immunodeficiency virus, but the early events leading to these deficits are unknown. We explored the role of cells specific to simian immunodeficiency virus and CD8 cells in the determination of CD4 failure and rapid disease course. DESIGN AND METHODS: Using MamuA*01-restricted Gag and Tat epitope tetramers, we compared the kinetics of specific response in animals with regular (REG) and rapid (RAP) progression. Expressions of memory, activation and proliferation markers were examined on the global CD8 pool, as well as on CD4 T cells in those animals. In-vivo CD8 depletion in non-MamuA*01 animals was used to investigate CD8 collapse as an event leading to disease progression and CD4 deficits. RESULTS: In animals with a rapid disease course, an initial development of cytotoxic T lymphocytes specific to simian immunodeficiency virus is followed by collapse accompanied by global changes in CD8 cells and occurs in synchrony with the characteristic CD4 deficiencies. Antibody-mediated depletion of CD8 cells early after infection with simian immunodeficiency virus induces similar changes in the CD4 cells and rapid development of AIDS. CONCLUSION: CD8 collapse at acute time points may result in uncontrolled viral load and development of a defective and insufficient CD4 population. Our results indicate that early breakdown in CD8 cells leads to CD4 deficits and rapid progression to AIDS and suggest that therapeutic approaches should aim at strengthening CD8 T cells early after viral infection.
Subject(s)
CD4-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/immunology , Simian Acquired Immunodeficiency Syndrome/immunology , Animals , Brain/immunology , Brain/virology , CD4 Lymphocyte Count , Cell Proliferation , Disease Progression , Immunophenotyping , Lymphocyte Activation/immunology , Macaca mulatta , Simian Acquired Immunodeficiency Syndrome/virology , T-Lymphocytes, Cytotoxic/immunology , Viral LoadABSTRACT
Indoleamine 2,3-dioxygenase (IDO), a tryptophan catabolizing enzyme, has been implicated in the pathogenesis of various neurological disorders. IDO expression is induced by IFN-gamma and leads to neurotoxicity by generating quinolinic acid. Additionally, it inhibits the immune response through both tryptophan depletion and generating other tryptophan catabolites. IL-4 and IL-13 have been shown to control IDO expression by antagonizing the effects of IFN-gamma in different cell types. Here, we investigated the effects of these cytokines on IDO expression in microglia. Interestingly, we observed that both IL-4 and IL-13 greatly enhanced IFN-gamma-induced IDO expression. However, tryptophanyl-tRNA synthetase (WRS), which is coinduced with IDO by IFN-gamma, is downregulated by IL-4 and IL-13. The effect of IL-4 and IL-13 was independent of STAT-6. Modulation of IDO but not WRS was eliminated by inhibition of protein phosphatase 2A (PP2A) activity. The phosphatidylinositol 3-kinase (PI3K) pathway further differentiated the regulation of these two enzymes, as inhibiting the PI3K pathway eliminated IFN-gamma induction of IDO, whereas such inhibition greatly enhanced WRS expression. These findings show discordance between modulations of expression of two distinct enzymes utilizing tryptophan as a common substrate, and raise the possibility of their involvement in regulating immune responses in various neurological disorders.
Subject(s)
Indoleamine-Pyrrole 2,3,-Dioxygenase/metabolism , Interferon-gamma/pharmacology , Interleukin-4/pharmacology , Microglia/drug effects , Microglia/metabolism , Tryptophan-tRNA Ligase/metabolism , Animals , Cells, Cultured , Gene Expression/drug effects , Indoleamine-Pyrrole 2,3,-Dioxygenase/genetics , Interleukin-13/pharmacology , Mice , Mice, Knockout , Phosphatidylinositol 3-Kinases/metabolism , Phosphoprotein Phosphatases/metabolism , Phosphorylation , Protein Phosphatase 2 , STAT1 Transcription Factor/genetics , STAT1 Transcription Factor/metabolism , STAT1 Transcription Factor/physiology , STAT6 Transcription Factor/genetics , STAT6 Transcription Factor/physiology , Signal Transduction/physiology , Tryptophan-tRNA Ligase/geneticsABSTRACT
The host reaction to infection of the brain contributes to a number of CNS pathologies including neuro-AIDS. In this study, we have identified the accumulation of SIV-specific CTL in the brains of SIV-infected animals who have neurophysiological abnormalities but are otherwise asymptomatic. SIV-specific CTL enter the brain early after viral infection and are maintained in the brain even when those reactive with an immunodominant epitope in Tat are lost from the rest of the body. The specialized CNS environment contributes to this unique outcome. Following SIV infection, brain levels of IL-15 were significantly elevated whereas IL-2 was absent, creating an environment that favors CTL persistence. Furthermore, in response to IL-15, brain-derived CD8(+) T cells could expand in greater numbers than those from spleen. The accumulation, persistence, and maintenance of CTL in the brain are closely linked to the increased levels of IL-15 in the absence of IL-2 in the CNS following SIV infection.
Subject(s)
Brain/immunology , Interleukin-15/immunology , Simian Acquired Immunodeficiency Syndrome/immunology , Simian Immunodeficiency Virus , T-Lymphocytes, Cytotoxic/immunology , Amino Acid Sequence , Animals , Blood/immunology , Cell Survival , Cerebrospinal Fluid/immunology , Cytokines/analysis , Cytokines/metabolism , Epitopes, T-Lymphocyte/immunology , Interleukin-15/analysis , Macaca mulatta , Molecular Sequence Data , T-Lymphocytes, Cytotoxic/virologyABSTRACT
The human immunodeficiency virus type 1-associated cognitive-motor disorder, including the AIDS dementia complex, is characterized by brain functional abnormalities that are associated with injury initiated by viral infection of the brain. Indoleamine 2,3-dioxygenase (IDO), the first and rate-limiting enzyme in tryptophan catabolism in extrahepatic tissues, can lead to neurotoxicity through the generation of quinolinic acid and immunosuppression and can alter brain chemistry via depletion of tryptophan. Using the simian immunodeficiency virus (SIV)-infected rhesus macaque model of AIDS, we demonstrate that cells of the macrophage lineage are the main source for expression of IDO in the SIV-infected monkey brain. Animals with SIV encephalitis have the highest levels of IDO mRNA, and the level of IDO correlates with gamma interferon (IFN-gamma) and viral load levels. In vitro studies on mouse microglia reveal that IFN-gamma is the primary inducer of IDO expression. These findings demonstrate the link between IDO expression, IFN-gamma levels, and brain pathology signs observed in neuro-AIDS.
Subject(s)
Brain/enzymology , Simian Acquired Immunodeficiency Syndrome/enzymology , Simian Acquired Immunodeficiency Syndrome/genetics , Tryptophan Oxygenase/genetics , AIDS Dementia Complex/etiology , Animals , Base Sequence , Brain/immunology , Brain/pathology , Disease Models, Animal , Gene Expression Regulation, Enzymologic , Humans , In Vitro Techniques , Indoleamine-Pyrrole 2,3,-Dioxygenase , Interferon-gamma/genetics , Interferon-gamma/metabolism , Interferon-gamma/pharmacology , Macaca mulatta , Mice , Microglia/drug effects , Microglia/enzymology , Molecular Sequence Data , RNA, Messenger/genetics , RNA, Messenger/metabolism , Recombinant Proteins , Simian Acquired Immunodeficiency Syndrome/immunology , Simian Acquired Immunodeficiency Syndrome/pathology , Tumor Necrosis Factor-alpha/metabolismABSTRACT
The etiology of the central nervous system (CNS) alterations after human immunodeficiency virus (HIV) infection, such as dementia and encephalitis, remains unknown. We have used microarray analysis in a monkey model of neuroAIDS to identify 98 genes, many previously unrecognized in lentiviral CNS pathogenesis, whose expression is significantly up-regulated in the frontal lobe of simian immunodeficiency virus-infected brains. Further, through immunohistochemical illumination, distinct classes of genes were found whose protein products localized to infiltrating macrophages, endothelial cells and resident glia, such as CD163, Glut5, and ISG15. In addition we found proteins induced in cortical neurons (ie, cyclin D3, tissue transglutaminase, alpha1-antichymotrypsin, and STAT1), which have not previously been described as participating in simian immunodeficiency virus or HIV-related CNS pathology. This molecular phenotyping in the infected brains revealed pathways promoting entry of macrophages into the brain and their subsequent detrimental effects on neurons. These data support the hypothesis that in HIV-induced CNS disease products of activated macrophages and astrocytes lead to CNS dysfunction by directly damaging neurons, as well as by induction of altered gene and protein expression profiles in neurons themselves which are deleterious to their function.
Subject(s)
Central Nervous System Diseases/pathology , Gene Expression Profiling , Macrophages/metabolism , Neurons/metabolism , Simian Acquired Immunodeficiency Syndrome/pathology , Simian Immunodeficiency Virus , Animals , Antigen Presentation/genetics , Antigen Presentation/immunology , Brain/metabolism , Brain/pathology , Brain/virology , Cell Cycle/genetics , Cell Differentiation/genetics , Cell Division/genetics , Cell Movement , Central Nervous System Diseases/genetics , Central Nervous System Diseases/metabolism , Cytoskeleton/genetics , Gene Expression Regulation/drug effects , Immune System/metabolism , Immunohistochemistry , In Situ Hybridization , Inflammation/genetics , Inflammation/metabolism , Inflammation/pathology , Interferons/pharmacology , Macaca mulatta , Macrophages/virology , Microglia/metabolism , Microglia/virology , Monocytes/pathology , Neurons/virology , Oligonucleotide Array Sequence Analysis , Proteins/genetics , RNA/genetics , RNA/metabolism , Signal Transduction/genetics , Simian Acquired Immunodeficiency Syndrome/genetics , Simian Acquired Immunodeficiency Syndrome/metabolism , Transcription, GeneticABSTRACT
To investigate the basis for envelope (Env) determinants influencing simian immunodeficiency virus (SIV) tropism, we studied a number of Envs that are closely related to that of SIVmac239, a pathogenic, T-tropic virus that is neutralization resistant. The Envs from macrophage-tropic (M-tropic) virus strains SIVmac316, 1A11, 17E-Fr, and 1100 facilitated infection of CCR5-positive, CD4-negative cells. In contrast, the SIVmac239 Env was strictly dependent upon the presence of CD4 for membrane fusion. We also found that the Envs from M-tropic virus strains, which are less pathogenic in vivo, were very sensitive to antibody-mediated neutralization. Antibodies to the V3-loop, as well as antibodies that block SIV gp120 binding to CCR5, efficiently neutralized CD4-independent, M-tropic Envs but not the 239 Env. However, triggering the 239 Env with soluble CD4, presumably resulting in exposure of the CCR5 binding site, made it as neutralization sensitive as the M-tropic Envs. In addition, mutations of N-linked glycosylation sites in the V1/V2 region, previously shown to enhance antigenicity and immunogenicity, made the 239 Env partially CD4 independent. These findings indicate that Env-based determinants of M tropism of these strains are generally associated with decreased dependence on CD4 for entry into cells. Furthermore, CD4 independence and M tropism are also associated with neutralization sensitivity and reduced pathogenicity, suggesting that the humoral immune response may exert strong selective pressure against CD4-independent M-tropic SIVmac strains. Finally, genetic modification of viral Envs to enhance CD4 independence may also result in improved humoral immune responses.