Neuroscience findings in AIDS: A review op research sponsored by the National Institute of Mental Health

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NEUROSCIENCE FINDINGS IN AIDS: AREVIEWOFRESEARCH SPONSORED BY THE NATIONAL INSTITUTE OF MENTAL HEALTH WILL0 PEQUEGNAT, NANCY

A.

GARRICK, AND ELLEN STOVER

Office of AIDS Programs, NINH, Rockville, MD, U.S.A (Final form, October 1991) Contents Abstract 1.

2. 2.1. 2.2. 2.3. 2.4. 3. 3.1. 3.2. 3.3. 3.4. 4. 4.1. 4.2. 4.3. 4.4. 4.5. 4.6. 5, 5.1. 5.2. 5.3. 5.4. 6.

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Introduction 146 Mechanisms of Nsuropathogenesis 147 Cell Culture Model of NIV-Associated Neural Damage 147 Quinofinic Acid and Neuropathology 148 Immunoregulatory Activity of HIV-l Associated Peptides 149 Inununotoxin-InducedT-Cell Death 149 Animal Models for Human AIDS and HIV Encephalopathy 150 MousefKSV-1 Model of Virus-Induced Behavioral Disorders 150 Borna Virus Model for Virus-Induced Neurological Damage 151 CNS Effects of HIV-l in Rabbits 152 Simian AIDS Models for Neurobehavioxal Effects of HIV-l Infection152 Two-Way Interactions Between the Brain and the InununeSystem 154 Sympathetic Regulation of Immune Responae in Spleen and Thymus 154 Brain Interleukin-1 Reduction of Cellular Immune Response 155 Brain Targets for Melanotropin 157 Central and Peripheral Interleukin-I Mediated Immunoregufatian 158 Role of the HPA Axis in Susceptibility to Inflammatory Disease 158 Neurotransmission with Cells of the Immune System 159 Stress and Immune Function 160 Regulation of Brain and Lymphoid Glucocorticoid Receptor% 3.60 Restraint Stress: Suppression of NHC I-a Expression 161 Mechanism% of Stress-Induced Immune Alterations 161 Impact of Stress on the Immune-Endocrine Axis and Health 163 Future Directions 164 Acknowledgements 165 References 165

Abstract Pequegnat, Wilfa, Nancy A. Garrick and Ellen Stover, Neuroscience Findings in AIDS: A Review of Research Sponsored by the National Institute of Mental Health. Neuro-Ps.ychopharmacal.& Biol. Psychia. 1992, 1612) : 145-170. 145

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1. The human immunodeficiency virus (HIV-l) infects cells in both the immune system and the brain, but these effects are not independent. 2. Research funded by the National Institute of Mental Health (NIMH) has been directed at identifying some of the mechanisms by which HIV-l infects the brain, produces pathology, causes behavioral changes, and alters immune responses. 3. HIV-l-associated peptides have been shown to produce immunological changes without active virus present and there is also evidence that neurological damage may result not from direct viral action, by via excitotoxin production. 4. Rhesus macaque monkeys infected with simian inununodeficiency virus (SIV) are proving to be a useful model of the neurological and behavioral changes identified in human AIDS patients; behavioral changes observed in monkeys are similar to those seen in humans infected with HIV-l. 5. Studies examining the relationship between the brain and immune system are identifying the role that the macrophage cytokine interleukin-1 may play in suppressing T-lymphocyte activity by two pathways, both mediated by corticotropin releasing factor (CRF). 6. One pathway involves the pituitary-adrenal axis and release of glucocorticoids while the other involves direct interaction with the sympathetic noradrenergic nervous system, which has been shown to innervate T-lymphocytes in the spleen and thymus. 1. These observations are relevant because macrophages infected with HIV-l infiltrate the brain and may release substances that damage the brain. 8. Stress may affect these pathways via the CRF-mediated release of glucocorticoids; a model of stress has also demonstrated that stress can suppress the cellular immune response. Keywords: alpha-melanocyte stimulating hormone, glucocorticoid, HIV-lassociated peptides, human immunodeficiency virus, hypothalamic-pituitaryadrenal axis, interleukin-1, macrophages, norepinephrine, Rhesus macaque monkeys, Simian immunodeficiency virus, stress-induced immune alterations, sympathetic noradrenergic nervous system, T-lymphocytes, quinolinic acid Abbreviations: Adrenocorticotropin hormone (ACTH), Acquired immunodeficiency syndrome (AIDS), azidothymidine (AZT), beta-transforming growth factor (beta-TGF), central nervous system (CNS), cerebrospinal fluid (CSF), corticotropin releasing factor (CRF), deoxyribonucleic acid (DNA), EbsteinBarr virus (EBV), Herpes simplex type 1 virus (HSV-l), human cerebral cortical neuronal cell line (HCN-lA), human immunodeficiency virus (HIV-l), hypothalamic-pituitary-adrenal (HPA), interleukin (IL), 5'-iododeoxyuridine (IUdR), a-melanocyte stimulating hormone (a-MSH), messenger ribonucleic acid (mRNA), natural killer cell activity (NK cell activity), N-methyl Daspartate (NMDA), phytohemagglutinin (PHA), polymerase chain reaction (PCR), ribonucleic acid (RNA), simian immunodeficiency virus (SIV), streptococcal cell walls (SCW) 1. Introduction The human immunodeficiency virus (HIV-l) infects cells in both the immune system, particularly CD4+ T-lymphocytes, and the brain. Individuals with AIDS often exhibit neurological and behavioral deficits in addition to

NeurosciencefInciingsinAlDS profound immunological deficiencies. The effects of HIV-1 on the brain and the immune system, however, are not independent. For example, macrophages are present in the HIV-l-infected brain in large numbers. In addition, the brain and immune system are linked by a variety of neural and hormonal signals, some of which may be altered by HIV-l infection. Autopsy studies have demonstrated that the majority of AIDS patients have an HIV-1 infection of the central nervous system (CNS). Approximately 50 percent of AIDS patients develop what is known as BIV-1 Associated Cognitive/Motor Complex, characterized by progressive impairment of motor and cognitive functions (Budka et al 1991). The possibility exists, however, that HIV-1 may exert physiologic effects in the brain, via the brain-immune system connection, that influence the course of systemic infection without impairing neurological function. To better understand the effects of HIV-l on the CNS and behavior, the National Institute of Mental Health (NINH) supports HIV-l-related research in the neurosciences. NIMH convened a meeting of grantees and intramural scientists on February 21-22, 1991 to assess the current state of neuroscience research related to HIV-1 infection and AIDS, and to identify directions for future studies. Scientific presentations centered on the effects of HIV-1 on neural tissue and behavior, and recent findings on the interactions between the brain and immune system. This article is based on the presentations at this meeting and is organized around four topics: (I) Mechanisms of Neuropathoqenesis, (2) Animal Models for Human AIDS and BIV Encephalopathy, f3) Two-Nay Interactions Between the Brain and the Immune System, and (4) Stress and Immune Function. 2. Mechanisms of Neurooathosenesis Several studies have corroborated the presence of HIV-l in brain tissue of individuals who test positive for HIV-l. Other reports, based on autopsy studies, have demonstrated that there is neurological damage present in many patients who die of AIDS or HIV-l-related complications. Current NINNfunded research is pursuing several areas of inquiry. Some questions of interest are whether HIV-I leads to direct damage of nerve cells and whether HIV-l-related peptides cause direct damage of nerve cells. The neurological damage present in AIDS patients may be due to the virus or to other biochemical events triggered by HIV-l infection. The following section reviews some results from studies directed at these questions. 2.1. Cell Culture Model of HIV-l-Associated Neural Damaue Investigators have found a correlation between the earlier onset of immune dysfunction and more severe abnormalities in both neuropathology and fetal development: the forehead is prominent (bossing), the nose is flattened, and the distance between the nose and lips is increased. The bxains of fetuses from normal women and from others infected with HIV-l were examined (Hutchins et al 1990). In normal brain, they found rich neuropil development with glioblasts, neuroblasts, and germinal matrix cells. In fetuses infected with HIV-l, no neuropathological change or only mild chanqes ranging from focal hemorrhage to significant cellular dropout and edema formation were visible.

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To study these changes in a time-dependent manner, Lyman and colleagues developed a tissue culture model using explant cultures of frontal lobe containing a portion of the germinal matrix (Lyman et al 1988). This tissue grows well and develops a rich culture with arborization, cell outgrowth, cell differentiation, and synapse formation. Thymus tissue from the same fetus was also cultured to provide autologous thymocytes for future studies of the inflammatory response in neural tissue. Incubating the cultured cortical tissue with supernatant containing HIV-l for seven days produced significant cell drop out, edema formation, and lipid deposition, but little overt evidence of HIV-l infection. A model for the fetal blood brain barrier which consists of cultured fetal astrocytes growing on one side of a permeable membrane with autologous umbilical cord cells growing on the other side has also been developed. Preliminary studies show that cells form junctional complexes. 2.2. Quinolinic

Acid and Neurooatholoav

Investigators have suggested that the CNS damage seen in AIDS patients may be a result of a neurotoxin associated with HIV-l infection. Heyes and colleagues (1991) found that the excitotoxin quinolinic acid, produced during tryptophan metabolism, may be one such neurotoxin. This compound, when injected directly into the brain may trigger nerve cell firing by binding to the N-methyl D-aspartate (NMDA) receptor, cause seizures in some animals, and ultimately kill neurons. In HIV-l infection, inflammation in the brain causes macrophages to infiltrate neural tissue. Macrophages contain the enzymes that produce quinolinate, so their presence may increase levels of quinolinate in the brain. They further hypothesize that this process, in turn, could produce more brain injury, attracting more macrophages in a potentially positive feedback cycle. Working with mice, Suito et al (1991) demonstrated that brain quinolinate levels rise after stimulation of the immune system with pokeweed mitogen or interferon-gamma. Following this observation, they measured quinolinate levels in the CSF of AIDS patients and found that these levels were markedly elevated over those found in healthy controls (Heyes et al 1991). Levels were highest in those patients with neurological symptoms, and correlated with the degree of neurological impairment. Conversely, patients treated with AZT showed a decrease in CSF quinolinate that correlated with an improvement in their neurological status. These results paralleled those seen in Rhesus macaque monkeys infected with simian immunodeficiency virus (SIV). Infected animals showed a 700-fold increase in quinolinate levels coinciding with the appearance of neurological symptoms. Monkeys infected with an SIV strain that does not produce neurologic deficits showed less elevation in quinolinate. A prospective study of patients with elevated quinolinate levels but no neurological signs is being conducted to determine whether they later develop neurological symptoms. These metabolic responses may reflect activation of indolamine-2,3-dioxygenase (Suit0 et al 1991).

Neuroscience findings in AIDS 2.3. Immunoreaulatorv

Activitv

of HIV-l-Associated

149 Pentides

Another body of evidence suggests that some of the pathogenesis of HIV-l infection may be mediated by soluble products derived from the HIV-l genome, rather than as a result of direct viral infection of target cells. Nair and colleagues (1988) and Tuki et al (1990), in cooperation with Hoffman-LaRoche Incorporated, developed a panel of recombinant and synthetic HIV-l peptides and examined their effects on immunocompetent cells. One peptide, a 120-residue fusion product consisting of approximately 80 residues of the GP-41 peptide from the HIV-l envelope and 40 residues from the gag viral core protein, clearly stimulated immunoglobulin production by mature lymphocytes obtained from healthy adult donors (Nair et al 1989; Tuki et al 1990). This is the first time a specific HIV-l peptide has been demonstrated to have the capability of regulating immune system activity. This observation may explain why AIDS patients develop hypergammaglobulinemia--a non-specific activation of B-cells that then produces large amounts of immunoglobulin with no protective influence. The gag-envelope peptide exhibited other immune regulating activity as well. Low levels of the peptide were able to inhibit immunoglobulin production by B-cells activated with pokeweed mitogen. Inhibition decreased with increasing amounts of peptide which also demonstrated the same reverse dose-dependent activity in suppressing natural killer (NK) cell leukemia activity. Adding the lymphocyte activator interleukin-2 (IL-2) to the cells not only reversed this inhibition, but produced a marked stimulation of NX cell activity. A second peptide, consisting of the superconserved region of GP-41 coupled to dihydrofolate reductase, showed this behavior as well, suppressing both B-cell activation and inducing DNA synthesis in T-cells. The gag-envelope peptide also activated DNA synthesis in cultured peripheral blood lymphocytes, but it inhibited DNA synthesis in lymphocytes obtained from umbilical cord (Tuki et al 1991). 2.4. Immunotoxin-Induced

T-cell Death

Neville and coworkers developed an immunotoxin based on the binding-site mutant diphtheria toxin CRM9 (Neville et al 1989). This immunotoxin was targeted at CD3-positive lymphocytes, and produced a lOOO-fold reduction in T-cell levels in vivo. The researchers used a nude mouse model implanted subcutaneously with Jurket human T-cell leukemia; these tumors do not undergo spontaneous remission. Immunotoxin was administered intraperitoneally, and the animals were evaluated 37 days later. Of the animals treated with the immunotoxin, 80 percent had complete tumor remission, and the tumors did not recur by day 56. There was no evidence of residual tumor upon autopsy. The immunotoxin's effectiveness may be due to the fact that CD3 and diphtheria toxin enter cells and travel to their targets by the same pathway. CM9 linked to an anti-CD5 immunoglobulin-- the number of CD3 and

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CDS receptors are approximately the same in this tumor line--produced no tumor regression. Diphtheria toxin works by blocking protein ayntheeis. Thus, this immunotoxfn could prove useful in eliminating quiescent T-cells from the body, those not actively expressing HIV-1 DNA. Other investigators (Zack et al 1990) have found that quiescent T-cells may be the reservoir for HIV-l during the latent phase of infection. 3. Animal Models for Human AXDS and HIV EnceohaloDathv The neuropathological indicators of the disease process are important in understanding the effects of AIDS. Animal models of both HIV-l infection and AIDS are invaluable for studying the progress of HIV-l infection, the behavioral and neurological changes that occur both during and after infection, and for development of potential therapies for treating and preventing infection. The models being developed under the auspices of NINH are aimed at elucidating the mechanisms by which viruses similar to HIV-1 infect the brain, and assessing behavioral changes that occur in animals infected with HIV-l itself or related viruses. 3.1 Mouse/HSV-I Model of Virus-Induced Behavioral Disorders Newborn mice infected with Herpes simplex virus type 1 (HSV-1) at birth show abnormal brain development and behavioral deficits (Crnic 1991). To probe the mechanisms that may underlie this observation, the brain and behavioral development in mice infected with HSV-I were studied (Crnic and Pizer 1988). When animals were inoculated 2 days after birth with a non-lethal virus lacking thymidine kinase, the virus entered the central nervous system rapidly, with titers peaking at about 10 days of age. However, if inoculated S days postnatally, the virus did not enter the brain. The virus disappears, leaving the mice with permanent behavioral and developmental deficits of two distinct types: one group of mice showed incomplete cerebellar development and were hyperactive while the other group had more severe cerebellar disruption and were both ataxic and hyperactive. The behavioral deficit in the hyperactive group was specific because the mice failed a teat requiring reduced activity, but performed as well as control mice in a similar task requiring an active response and in a difficult maze test (Fig 1 and Fig 2). Changes in the cerebellum correlated with the degree of hyperactivity. In normal development of mice, dramatic changes occur in the cerebellum between days 10 and 20. The most profound change is a migration of granule cells from the external to the internal granule cell layer; this is also largely a post-natal event in human brain development (Rakic and Sidman 1980). In the hyperactive mice, many granule cells do not complete migration, an observation that others had made following Tamiami virus infection in rats (Gilden et al 1974); behavior was not studied. However, hyperactivity is produced when granule cell migration is blocked by exposure to x-radiation in the neonatal period in rats (Altman et al 1971;

Neuroscience llndings in AIDS

HSV

151

Control

Fig 1. Trials to criterion on a step-down passive avoidance task. Values given are means of litter averages + SD and are significantly diffeirent (v < 0.05). Mice were injected subcutaneously in the shoulder on the first day of liie with either iOe plaque forming units of a mutant HSV-1 (HSV) or uninjected (control) and tested as adults. Criterion performance 'consisted of 2 trials of 120 s each in which the mouse remained on a platform above a grid electrified with 200 pa. From Crnic and Pizer 1988.

HSV

Control

Fig 2. Trials to criterion (7/8 correct choices for 5 consecutive trials) on an 8 arm radial maze learning task. The same mice described in Fig 1 were given 50 pl water to reinforced correct choices on 3 trials a day. There was no difference between the performance of the two groups. From Crnic and Pizer 1988.

Wallace et al 1972). Thus granule cell heterotopia may be a common defect through which a variety of insults, including viruses, could produce hyperactivity. 3.2. Borna Virus Model for Virus-Induced

Neuroloaical

Damaae

Borna virus, like HIV-l, is an RNA virus with a long latency between infection and clinical manifestations. In addition, Borna virus also has a specific affinity for neurons in the limbic system and can produce an observable behavioral syndrome in adult rats, and thus may serve as a useful model for the pathogenesis of HIV-l-mediated behavioral changes. It is possible to detect Borna virus antibodies in about 10 percent of AIDS patients with encephalopathy. Attempts to isolate structurally intact Borna virus particles have not yet been successful; therefore, Dietzschold and coworkers used protein microsequencing and molecular cloning to obtain viral-specific nucleic acid sequences (Shankar et al under review). One of these sequences has been used as a probe to identify where the virus is retained following acute infection in the rat. Preliminary results suggest that the virus enters the central nervous system through the olfactory neuroepithelium and then moves to the olfactory bulb, cerebrum, brain stem, and cerebellum.

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These investigators have also found that Borna virus induces a gene of the platelet 4 cytokine family, which includes IL-8. This lymphokine affects gross movement of a variety of cells that participate in immune and i~unoinfla~atory responses. They are studying whether Borna virus induces cytokine release in the brain and if this can trigger cell-mediated immune response in neural tissue. 3.3. CNS Effects of HIV-1 in Rabbits Kulaga and coworkers used a human T-cell line, HCN-lA, as a carrier to infect rabbits with HIV-1 (Kulaga et al under review). HCN-1A is a continuous cell line isolated from a patient with unilateral megaloencephaly, a condition where immature neurons continue to proliferate at an uncontrolled rate following infection with a high titered HIV-1 stock (LAV), HCN-1A cultures exhibit many properties normally described for infection of susceptible cell lines. This provides the first evidence for the infection of a human cerebral cortical neuronal cell line (HCN-1A) with the human immunodeficiency virus-l (HIV-1). The changes include alterations in cellular morphology during the course of infection, even though syncytia formation is diminished in comparison with permissive cell lines of lymphoid origin. Productive infection as evidence in cultures 3-15 days after inoculations, as determined by an increase in both p24 antigen production and, to a lesser extent, an increase in reverse transcriptase (RT) activity in cell free supernatants. Following infection an increase in virus positive cells was detected by indirect immune fluorescent using serum from an individual with AIDS. Confirmation that HCN-1A cells were infected with HIV-l was provided by analysis of polymerase chain reaction (PCR) amplified cDNAs obtained from long term cultures. Proof that cellfree supernatants of infected HCN-1A cultures contained infectious virus was obtained by successful passage to a permissive human T-cell line (A3.01). The ability of HIV-l to infect HNC-1A in viCro may provide a model to investigate further the mechanisms involved in neuronal dysfunction associated with acquired immune deficiency syndrome (AIDS). 3.4. Simian AIDS Model6 for Neurobehavioral Effects of HIV-1 Infection Simian immunodeficiency virus (SIV) infects Rhesus macaque monkeys producing immune and CNS pathology that closely resembles HIV-l induced pathology in humans. Both SIV and HIV-l are retroviruses that use the CD4 molecule on T-helper lymphocytes as the entry site for infection. Some SIV-infected monkeys also show behavioral changes that suggest that they may be a good model for studying AIDS dementia complex. Rausch et al (1990) have been working with SfV-infected Rhesus macaques as a model.to test the effectiveness of CDQ-derived peptides to either block SIV infection or retard disease progression. The peptide, a tribensyl-derivative of amino acids 81 to 92 in the CD4 molecule, was used. This modification is hypothesized to restrict the peptide's conformation so that it mimics that region in the whole CD4 molecule. Animals were infused with the peptide over a lo-hour period to maintain a therapeutic serum level of peptide prior to inoculation with SXV, and for eight hours after inoculation. The peptide-treated group had a longer mean survival time than did an untreated, SIV-inoculated group (Fig 3).

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Peptide treated: Mean SurvivalTime 353 Days

~~~

Days Post-Inoculation Fig J. Rausch

Comparison of et al 1990.

animals

injected

with

peptide

vexx%s

control.

From

and colleagues (1990) havtlcantimed to improve the peptide so it is nearly seven times mofe effective in blocking infection in an ia vitm assay. Such peptfdes may prove useful in blocking NIV-1 Infection in infants born to seropositive mothers. Rausch

that

Other investigators have also used SW-infected Rhesus macagues to study behavioral changes (Murray et al under review). Monkeys were trained on a number of tasks that measured a variety of visual learning and memory abilities and motor skills. The tests were selected because they assess the integrity of different neural substrates. For example, matching to sample tasks are known to depend on functioning of the medial temporal lobe. The study involved ten inoculated monkeys, of which only 8 became productively infected, and five &am-inoculated control monkeys- The data showed that some of the infected animals performed a fittle worse on these tests than did the controlst but the group difference was not statistically significant.

However, analyzing the test data on an individual basis according to preand post-inoculation behavioral scorea revealed relatively early in the post inoculation testing, that four of the eight monkeys performed significantly outside the ranga of the control animals, The two inoculated but uninfected animals performed in the normal range. By the end of postinoculation testing, 7 of 8 infected animals performed more pearly than the controls on the motor skills testt showing a subtle but significant difference. Patients with AIKiSshow similar results on behavioral tests. Different patterns of impaiment were also seen in the individual monkeys. One monkey, for example, was impaired in a recognition memory task as well as on a discrimination leasning and retention task, but not on the motor skills task. Another monkey was impaired in discrimination learning

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and retention and motor skills, but not in recognition. But impairments in recognition and recency memory seemed correlated, as were impairments on discrimination learning and retention. Currently, brain autopsy studies are underway, but a preliminary analysis shows that there is a very slight pathology in animals with significant behavioral impairments. 4. Two-Wav

Interactions

Between the Brain and Immune Svstem

Results from research efforts have highlighted the fact that the immune system is not an autonomous system. It is regulated, not only by cells of the immune system, but by the autonomic nervous system, neuropeptides, hormones, and a host of factors that were not originally believed to be immunomodulatory. Two observations in the field of neuroimmunology may lead to an understanding of the mechanisms by which HIV-l compromises the immune system. The first is that glucocorticoids are released at the peak of an immune response, probably through the hypothalamic-pituitary-adrenal (HPA) axis, and the second is that there are beta adrenergic receptors on the surface of lymphocytes. These two observations form the basis for the studies presented below. 4.1. Svmoathetic

Reaulation

of Immune ReSDOnSe

in Soleen and Thvmus

The observation that lymphocytes have neurotransmitter receptors on their surfaces has prompted a number of investigations into possible modulatory effects of neurotransmitters on immune response (Johnson and Fuchs 1991). The investigators used 6-hydroxydopamine chemically to sympathectomize mice and studied the effect of the resulting norepinephrine deficiency on various components of the immune system. After sympathectomy, beta-receptor density increased on lymphocyte cell surfaces. Conversely, immunizing intact mice with an antigen caused the density of the beta-receptors to decrease by 50 percent, coinciding with an increase in norepinephrine turnover in the spleen (Pruett and Fuchs under review). Sympathectomy significantly reduced thymus weight and altered thymic T-cell populations. The largest decrease was in the number of CD4 positive/CD8 positive T-cells. T-cells that were either CD4 positive or CD8 positive also disappeared. Preliminary data suggest that the absence of norepinephrine induces programmed cell suicide, or apoptosis, in the affected T-cell populations. Treating mice with 5_hydroxydopamine, which does not destroy norepinephrine nerve terminals, had no effect on the spleen, thymus, or immune cell populations (Spriggs and Fuchs in preparation). Morphine addiction may have an effect similar to sympathectomy. Subcutaneous implantation of time-release morphine pellets in mice produced addiction within two days. After four days the animals showed a significant decrease in immune function. In the spleen, a decrease in the ability to form antibody-forming cells was found in the morphine-addicted mice (Fuchs and Pruett under review). In the thymus, 92 percent of T-cells with both CD4 and CD8 receptors are killed, and apoptosis again appears to be involved. Both the opiate antagonist naloxone and the glucocorticoid antagonist RU486 blocked morphine's effects on the immune system, indicating that morphine may be inducing the release of glucocorticoids

NeurasciencefindingsjnAiDS (Pruett and Fuchs under review). In addition to stimulating the HPA axis, morphine may be activating the sympathetic nervous system since up to 50 percent of the beta receptors on lymphocytes disappeared within 24 hours (Freier and Fuchs under review). Based on these results, Fuchs and his colleagues have suggested that antigens may act as a stressor in the following way. In the presence of an antigen, the immune system releases a chemical signal, such as interleukin-1 (IL-l), that travels to the h~othal~us and triggers the CRf-ACTH-glucocorticoid cascade. In addition, CRF may increase autonomic activity by way of noradrenergic neurons. 4.2. Brain Interleukin-1 Reduction of Cellular Immune Resoonse One characteristic of HIV-infection of the CNS is that macrophages are able to cross the blood-brain-barrier. Macrophages secrete a number of cytokines, among them IL-l, that have powerful effects on cells of the immune system. To determine if IL-1 released in the brain could also affect the systemic immune response; picogram were injected with quantities of human recombinant IL-l into the central nervous system of the rat to determine its effects on cellular immune responses (Weiss et al 1991).

tiours after

-

infusion

Vehicle

D....*.iTl LPS *---?A

IL-1

Hours after infusion Fig 4, MR cell activity, response to PMA, and IL-2 production in groups infused with IL-l (200 pg), LPS (10 ng), or vehicle, with lymphocytes taken 3, 6, and 24 hr after infusion. Means + SE% are shown. n - 3 for each group at each time point. Measures were not made of PMA response in blood lymphocytes or IL-2 production in splenocvtes at 24 hr. Differs significantly from vehicle-infused animals at the same time point. From Sundar et al 1989.

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Fifteen minutes after injection there was a decrease in the mitogen responses of blood and spleen lymphocytes and in NK cell activity. The responses remained suppressed for as long as six hours and returned to normal within 24 hours without rebound enhancement (Fig 4). Systemic injection of IL-1 did not produce this effect I indicating that the effects of IL-1 are centrally mediated. Simultaneous administration of an IL-l blocker, alpha-melanocyte stimulating hormane (a-MSH), completely inhibited the effect by pxeventing IL-l from stimulating the HPA axis (Weiss et al 1991). Conversely, injecting lipopolysaccharide, a potent stimulator of IL-l, into mouse brains suppressed immune system activity: this effect was blocked by a-MSW. Splanic

Lymphocytes

Fig 5* Cellular immune response of spfenic lymphocytes following infusion of IL-l or vehicle. Animals were infused with either control IgG (non-CRF IgGf or anti-CRF IgG in low dose (Q-75 ug) or high dose (2.25 ugf. Effects are shown on NX cell activity, response to PHA, and IL-2 production. Xean and SE for each group are shown. Asterfskf differences significantly (at least p < 0.05) from each of the other 3 groups; open circle, differs significantly form each vehicle-infused group. From Sundar et al 1990,

To determine whether this effect was due to stimulating the HPA axis, Weiss et al (1991) conducted the same experiments in adrenalectomised animals. Even without the ability to trigger glucocorticoid release, IL-1 produced a considerable amount of suppression of the cellular immune response. This appears to result from CRP stimulation of the adrenergic system (Sundar et al 1989). Administration of a purified antibody to CRF in

Neuroscience

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AIDS

conjunction with IL-l injection into the brain completely blocked the effects of IL-l. These investigators also demonstrated that pharmacological blockade of sympathetic neurotransmission, via the administration of chlorisondamine, reduced the severity of immunoauppresaion induced by IL-1 (Fig 5). Thus, IL-1 in the brain suppressed the immune system in two ways: by stimulating the HPA axis, leading to the eventual release of immune suppressing glucocorticoida, and by direct excitation of the sympathetic noradrenergic neural pathways (Sundar et al 1990). 4.3. Brain Taraets

for Melanotrooin

The role of alpha-MSH as a modulator of the effects of IL-l in the brain has been explored (Cannon et al 1986). They found that alpha-MSH inhibits immunostimulatory and proinflammatory actions of IL-l in vitro (Cannon et al 1986), while others have reported that alpha-MSH inhibits diverse actions of IL-l, including IL-l-induced fever, stimulation of adrenocorticotropin (ACTH) secretion, stimulation of neutrophil migration, and modulation of hypothalamic neuron firing, as well as central IL-l-induced suppression of immune responses. These IL-l-antagonistic properties suggest that endogenous hormonal and neuronal alpha-MSH may be part of a counterregulatory system which protects against the damaging effects of unchecked cytokine action. To identify target sites for endogenous alpha-MSH and related peptides (collectively known as melanotropins) in the brain, this group mapped the distribution of melanotropin receptors in the rat brain using in situ radioligand binding and autoradiography (Tatro 1990). Melanotropin receptors were found to be enriched in brain regions innervated by melanotropinergic neurons, including, among others, the preoptic and septal areas, which are thought to be involved in thermoregulation and fever; and the parvocellular division of the hypothalamic paraventricular nucleus, which is the primary site of CRF production. The results in the paraventricular nucleus suggest that one mechanism by which alpha-MSH inhibits IL-l actions in the brain, may be by modulating the cytokine'a ability to stimulate CRF secretion, thereby affecting either responses of the hypothalamic-pituitary-adrenal axis (see Sternberg et al), and/or the reported systematically immunosuppressive effects of central CRF release (see Sundar et al). In melanoma cells, which are the classic mammalian melanotropinresponsive model system, melanotropin receptors bind alpha-MSH with higher affinity than its homologous precursor peptide, ACTH (Tatro et al 1990). In contrast, brain melanotropin receptors recognized alpha-MSH and ACTH with apparently equal affinities, suggesting that either alpha-MSH or ACTH may potentially act as endogenous ligands for melanotropin receptors in the brain, and that multiple melanotropin receptor subclasses exist (Tatro 1990). Present research is aimed at characterizing the brain melanotropin receptors, and at defining the mediators and cellular targets of alpha-MSHIL-l) interactions in the brain. If cytokines mediate brain injury in AIDS and in CNS diseases such as multiple sclerosis, as suggested by recent reports, then defining the basic roles of the melanotropinergic counterregulatory neuronal system may permit the development of new

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strategies for mitigating the disease processes. 4.4 Central and Perinheral Interleukin-1 Mediated Immunoresufation To further explore the role on IL-1 in mediating the immune response, Greenberg and colleagues (in press) tested the hypothesis that IL-l released by macrophages that had infiltrated the brain could stimulate the hypothalamus to release CRF, which would trigger a rise in ACTH and eventually glucocorticoid concentrations. This, in turn, would suppress macrophage production of IL-l. Since one of the characteristics of HIV-l infection is the abnormal presence of macrophages in the brain, macrophage-secreted IL-1 could play a role in producing the suppressed immune response characteristic of AIDS. Two hours after injecting IL-l into a mouse brain, spleen macrophage secretion of IL-l was inhibited even after stimulation with lipopolysaccharide, a powerful inducer of macrophage IL-l production (Brown et al 1991). Macrophage production of another cytokine, beta-TGF, was not affected in either experiment. Repeating the experiment in adrenalectomized animals confirmed that corticosteroids were involved in blocking macrophage activity: IL-l secretion increased slightly in adrenalectomized animals, and lipopolysaccharide profoundly stimulated macrophage IL-l secretion. Corticosteroids are not the only factor involved, however, for surgical sympathectomy of the spleen also blocked the ability of IL-l injected in the brain to suppress macrophage synthesis of the cytokine. The mice have an intact HPA axis response, so circulating corticosterone concentrations increase after IL-1 injection. Therefore, a synergistic interaction between the HPA axis and the sympathetic nervous system must be present. In fact, performing both adrenalectomy and sympathectomy in the same mouse produced the highest level of IL-1 secretion. A complicating factor was the finding that adding IL-l to adrenocortical. cells caused the cells to release corticosterone and cortisol (Winter et al 1990). This direct stimulatory effect was quite sensitive, occurring at picogram levels of IL-l, but Greenberg and colleagues were unable to find IL-l receptors on adrenocortieal cells. They did find, however, that IL-1 could activate the cyclooxygenase system, and thus3,stimulate synthesis of prostaglandins 12, F2A, and E2. Indomethacin, a potent inhibitor of the cyclooxygenase pathway, completely blocked the IL-l-induced cortisol response, but had no effect on the ability of ACTH to stimulate cortisol secretion by the same cells. 4.5. Role of the HPA Axis in Susceotibilitv to Inflammatory Disease Further evidence that the HPA axis is integral in regulating the immune response comes from Sternberg (under review). They used the Lewis rat model for streptococcal-cell-wall-inducedarthritis to explore the importance of the HPA in susceptibility to inflammatory disease. Lewis rats are highly susceptible to developing arthritis in this manner because the hypothalamus does not synthesize and secrete CRF in response to inflammation or other stress mediators. Therefore, no corticosteroid response to shut down

maerophage and lymphocyte activity occurs, allowing the inflammatory response to go unchecked.

immune

Seven hours after intraperitonsel injection of streptococcal cell walls (SCW) peptidoglycan polysaccharide, Fischer rats, used as a control, expressed a significant amount of CRF mRNA in the paraventricular nucleus, while Lewis rats showed low induction of CRF mRNA synthesis, Administering physiological concentrations of dexamethasone significantly suppressed the inflammatory response, while blocking the feedback loop in Fischer rats with the gfucocorticoid antagonist RU486 produced inflammatory disease response to SCW in this otherwise Fnflammatory reef&ant strain of rats. There was also a behavioral difference between the Fischer and Lewis rats. Fischer rats, with a noma HPA axis response to stress, did not explore as much in an open-field, stressful situation when compared to Lawis rats with their blunted CAP response. These experiment8 suggest at least one mechanism by which abnormal reactions to stress and inflammation would be linked. 4.6. Neurotransmission with Cell8 of the Immune Svstem One way in which the brain might influence immune system behavior is by direct neurochemicaf transmission with cells of the immune system, since lymphocytes and other immune system cells contain receptors fox norepinephrine, substance P1 VIP, tachykinins, opiates, and other neuxotransmitters. There is evidence that noradrenergic neurons that innervate the thymus and spleen have nerve terminals that lie next to both lymphocytes and macrophages (Ackerman et al 1991; Felten and Felten 1937}. In the thymus, norepinephrine and neuropeptide Y nerve fibers are distributed widely in the cortical region. Noradrenergic nerve fibers distribute among thymocytes and substance P. CGRP fibers distribute along regions near the capsule and septa adjacent to mast cells. Norepinephrine nerve fibers enter the spleen with the splenic artery and distribute throughout the white pulp, where they arborize away from the vasculature and distribute extensively through the white pulp of the spleen, where there are abundant CD4 positive and CD8 positive T-cell populations; the norepinephrine nerve terminal is often cradled with an indentation sitting adjacent to T-cells. Noradrenergic nerve fibers also terminate next to macxophages. Substance panel CGRP nerve fiber distribute into both the white pulp and red pulp in the rat spleen. This research lab has also found evidence that norepinephrine's effects on the immune response may depend on when the appropriate cell of the immune system is exposed (Ackerman et al 1991). In the initiation phase of a primary immune response , norepinephrine actually enhances primary antibody responses. At the same time, norepinephrine inhibit8 effector cell formation. Denervating the spleen prior to antigen challenge produces an 30 percent decrease in primary antibody response.

160

W. PequegnatetaL 5. Stress and Immune Function

The brain exerts some control over the immune response, and this control may be exercised through the HPA axis. This same hormonal control system forms the basis of the body's response to stress. The question is then raised about which mechanisms contribute to the observed immunosuppressive effects. The following studies examine this question within the context of HIV-infection and AIDS. 5.1 Reaulation

of Brain and Lvmohoid Glucocorticoid

Receptors

To understand the effects of glucocorticoids on the brain and the immune system, Lowy (1989) has characterized glucocorticoid receptors through which glucocorticoids exert their biological activity in rat brain and lymphoid tissues (Lowy 1989). He found type II glucocorticoid receptors in high concentrations throughout the brain, including the striatum, hypothalamus, and hippocampus, as well as in the thymus, spleen, and to a lesser extent, lymphocytes. This suggests that the immunosuppressive effects of glucocorticoids are mediated by the type II receptor. There was no evidence of type I, or mineralocorticoid, receptors in the lymphoid tissue. Competition binding assays with several types of steroids confirmed that brain and spleen receptors exhibit virtually indistinguishable binding profiles. The molecular weights of the two receptors also appear identical. Lowy and coworkers examined the effect of chronic corticosteroid administration on glucocorticoid receptors in various tissues of the rat (Lowy 1991). In hippocampus, spleen, and lymphocytes there was the expected decrease in receptor density. The thymus, however, was resistant to the effects of corticosterone, although its mass was reduced by approximately 50 percent. The inability of the thymus to down-regulate the number of glucocorticoid receptors may contribute to its vulnerability to high levels of glucocorticoids. Seven days following adrenalectomy, receptors were increased in various rat brain regions but not in other tissues. Reserpine administered to adrenalectomized animals produced a significant decrease in corticosteroid receptors in the frontal cortex and hippocampus, but not in the hypothalamus (Lowy 1990a). There was no effect on the thymus, but there was a 50 percent drop in the number of receptors in the spleen. This may be related to the intense noradrenergic innervation in the spleen (Fig 6). Methamphetamine administered to adrenalectomized animals produced a pronounced decrease in glucocorticoid receptors in the hippocampus (Lowy 1990b). This was blocked by MK801, an excitatory amino acid antagonist acting via the NMDA receptor. A study with AIDS patients revealed that they have increased plasma cortisol levels, but paradoxically, decreased ACTH levels, suggesting that there may be an immune factor that can directly stimulate the adrenals independent of ACTH. An in vitro finding reveals that hydrocortisone can enhance the expression of HIV-l in tissue culture. Given the compromised immune system in AIDS patients as well as possibly compromised neuronal function, even modest elevations in cortisol concentrations may have

161

Neu~science findIngs in AIDS

FCx

THY

HPC

SPL

LYMP

HYPO

PIT

6. Distribution of tvne 1 fmineralocorticoidland tvne II (giucocorticoid) recepto;s in {A) brain and (B) lymphoid-and pituitary tissues. FCx=frontal cortex, HPC-hippocampus, ~O~h~othal~us, THY=thymus, SPL=spleen, LYMP=lymphocytes, PIT=pituitary. Prom Lowy 1989. Fia

deleterious

effects in these patients.

5.2. Restraint Stress: Suppression of MHC I-a ExDression Zwilling and colleagues investigated how restraint stress in mice suppresses MHC class II (I-A) expression by macrophages (Fig 7) (Swilling et al 1990a; Zwilling et al 1990b). The mononuclear phagocytes are important effector cells in controlling the growth of mycobacterium. Differences in I-A expression by macrophages have been associated with resistance of mycobacterial growth. Infections caused by these bacteria are common in AIDS patients who are under a considerable amount of stress. The suppression of MHC I-A glycoproteins, one of the earliest events of the immunological cascade, may therefose prove to be an important link between behavior and the clinical manifestations of HIV-1 infection. 5.3. Mechanisms of Stress-Induced Immune Alterations A reproducible model of stress-induced immune system changes was developed by Rabin and colleagues (Rabin et al 1989). Using conditioned response to electrical shock as the stressor in Lewis rats, they demonstrated that stress suppresses the mitogenic response of peripheral blood lymphocytes. There was also profound suppression of mitogenic activity, about 10 percent of normal, in the spleen as well, but by day 5 of the experiment the spleen's mitogenic responsiveness had habituated. Lymph node lymphocytes showed no alteration in macrophage mitogenic

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Beg’

f3cgs

Fig 7. Restraint stress does not affect I-A expression by macrophages from BCGR mice. Macrophages were obtained from Balb/C.BCGS mice after 12H of restraint. The percentage of macrophages expressing I-A was determined by indirect fluorescent, The data represent the mean of duplicate determinations for groups of eight mice. From Zwilling et al 1990a.

activity at any time, while blood lymphocyte mitogenic response stayed suppressed for approximately 96 hours following a single shock session. All types of T-cell lymphocytes were affected. Adrenalectomized animals did not exhibit a depressed response in the peripheral lymphocytes, although spleen lymphocytes were suppressed. Administering natalol, a beta-adrenergic antagonist, blocked the effect of stress on reducing spleen mitogenic activity, although blood lymphocyte mitogenic activity still decreased. This suggests that the spleen is functionally altered by an adrenergic-type of mechanism. Administering an inhibitor of norepinephrine release produced the same effect. Shock also decreased NK cell activity, and the effect was blocked by the opiate antagonist naltrexone. NX cell activity in the spleen did not habituate after five days as did lymphocyte mitogenic activity. Lymphocyte IL-2 production is not altered by shock treatment, although spleen lymphocytes produced 57 percent less interferon-gamma and showed lowered protein kinase C activity on day 1 of the stressor. This response habituated, however, by day 5. Confirming the report from Zwilling's laboratory ('&willing et al 1990a, 1990b), Rabin and coworkers showed that shock stress decreases MHC Class II antigen expression by macrophages; this response does not habituate, Mice show a different response to shock-induced stress. Mouse lymphocytes, for example, showed increased mitogenic response after stress. However, both mice and rats showed a decrease in immune system function when they were subjected to a mild stressor, such as living in a cage with four other animals (Lysle et al 1990).

Neuroscience findlngs inAIDS

Differences were also found in human immune system responses to stress. Heart rate, blood pressure, and lymphocyte activity were measured after performance of several stressful mental exercises. Based on these results subjects were designated as high-reactors or low-reactors. CD8 positive lymphocytes increased in number, and showed higher mitogenic activity, in the high reactors but not in the low reactors; CD4 positive lymphocytes were not affected by the mental stressors. Increasing the level of the stressor, however, resulted in all subjects responding as high-reactors (Manuck et al 1991). 5.4. Imuact of Stress on the Immune-Endocrine

Axis and Health

There is evidence that a number of immune system changes occur in humans following stressful events (Glaser et al 1985; Kiecolt-Glaser and Glaser 1991). There is a decrease or an inhibition of NK cell activity, changes in the ability of peripheral blood lymphocytes to synthesize interferon-gamma after stimulation with concanavalin A, an increase in cyclic AMP in peripheral blood lymphocytes, and down-regulation of the messenger RNA to the IL-2 receptor concomitant with a decrease in cells with IL-2 receptors (Kiecolt-Glaser and Glaser 1991). In a series of studies these investigators also studied the effect of stress on latent Epstein-Barr virus (EBV) in subjects who experienced stressful events and who served as their own controls (Glaser and GotliebStematsky 1982). EBV latently infects B lymphocytes as well as some epithelial cells in the nasopharynx. In a person with a normally functioning immune system, these latent viruses are generally not a health problem. In patients with severe immune suppression, however, these viruses can cause morbidity and mortality. Herpes viruses can be reactivated in a normal individual even in the absence of lesions. Evidence of this virus reactivation is based on recovering infectious virus or changes in antibody titers. The cellular immune response is thought to be important in controlling latent herpes viruses. Thus, in studying virus reactivation in normal individuals, an increase in antibody levels to EBV, for example, is not necessarily good, because it suggests a down-regulation of the cellular immune response in controlling latent virus. Under normal circumstances, when antibody titers drop, it indicates a more efficient cellular immune response is once again controlling virus latency. In one study, Glaser and colleagues examined EBV, HSV-1, and cytomegalovirus titers in subjects in an initial stressful situation and later in a non-stressful situation. They found that antibody titers dropped when measured after the non-stressful as compared to the stressful event; but no change was seen in antibody titers to polio virus type 2. Psychological assessments provided evidence that perceived stress and anxiety decreased as well. These data were confirmed in a year-long study with another group of subjects (Table 1) (Glaser et al 1987). Assays for specific antibodies against EBV polypeptides, conducted with the assistance of Gary Pearson, showed that only one of four antibodies

163

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W. Pequegnat

ef al.

Table 1 Means

(_tSEM) for EBV VCA Antibody Titers

Sample

EBV VCA

Baseline 1 (Sept.) Examinations (Oct.)

68.18 115.04

Baseline 2 (Jan.) Examinations (Feb.)

80.08 (15.86) 386.36 (101.30)

Baseline 3 (April) Examinations (May)

84.85 141.03

(25.05) (10.86)

(22.76) (46.34)

N = 34

Adapted

from Table 1, Glaser, R. et al (1987)

studied were modulated by stress. The specific antibody reacted to an early antigen protein associated with EBV DNA-polymerase activity. Glaser concluded that latent EBV, and therefore other latent viruses, may be reactivated only partially under certain circumstances (Glaser et al 1987). Whether pathology can result from viral genes expressed under these circumstances is not known. As already discussed, glucocorticoids are capable of inducing latent EBV in vitro. Glucocorticoids have also been shown to enhance HIV-1 replication. In addition, in vitro data show that certain stress hormones have the capability, by themselves, to induce and enhance virus expression. Taken together with Glaser's and others' studies showing stress-associated changes in latent herpes virus, a reasonable hypothesis warranting further study is that psychological stress, both by down-regulating the cellular immune response and enhancing virus expression, may affect the progression of HIV-~ in virus-infected individuals. 6. Future Directions Although progress has been made in studying the neuroscience of HIV-1 infection and AIDS, there are important questions that remain. The following are a sample of the ones raised during this NIMH-sponsored meeting. To what extent is the brain a reservoir for HIV-l, and as a reservoir, how does latent virus affect the brain? What are the differences and similarities between central nervous system dystrophy in infantile and AIDS dementia complex in juveniles and adults ? Do they represent different disease processes or are they manifestations of the same underlying pathophysiological mechanisms ? Does the CD4 molecule serve as a receptor for HIV-l in the brain as it does on T-lymphocytes? Are there other molecules in the brain that might act as receptors for the virus? Is the blood-brain barrier a target for HIV-l? What role do neurotoxins play in the neurological damage produced by HIV-l infection? How does the lifecycle of HIV-l differ in brain and systemic infections? Should researchers be looking for viral RNA, DNA, or protein when searching for the virus in the brain?

165

Neuroscience findings inAIDS Investigators are initiating studies to address these questions. The results of future studies may provide further clarification of the mechanisms that contribute to neurological and behavioral changes that accompany infection with HIV-l. Acknowledaements The authors gratefully acknowledge the assistance NIMH Professional Services Contract W352682.

of Joe Alper under an

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FUCHS, B. A. and PRUETT, S. B. Morphine induces apoptosis in the murine thymus in vivo: Involvement of both opiate and glucocorticoid receptors. (under review) GILDEN, D. H., FRIEDMAN, H. M., and NATHANSON, M. (1974) Tamiami .virus induced cerebellar heterotopica. J. of Neuro. and Exp. Neur. 33: 29-41. GLASER, R. and GOTLIEF-STEMATSXY, T. (Eds.) (1982) Human herpesvirus infections: Clinical aspects. Marcel Dekker, New York. GLASER, R., RICE, J., SHERIDAN, J., FERTEL, R., STOUT, J., SPEICHER, C., PINSXY, D., XOTUR, M., POST, A., BECX, M., and XIECOLT-GLASER, J. X. (1985) Stress-related immune suppression: Health implications. Br., Beh., Imm. 1: 7-20. GLASER, R., RICE, T., SHERIDEN, J., FERTEL, P., STOUT, J., SPEICHER, C. E., PINSLEY, D., XOTUR, E. M., POST, H., BECK, M., XIECOLT-GLASER, J. X. (1987) Stress-related immune suppression: Health implications. Br., Beh., Imm., 1: 7-20. GREENBERG, A. H., BROWN, R., LI, Z. and DYCX, D. G. (1991) Brain immune pathways regulating immunological functioning and conditioned immune responses. In: Behavior and Immunity, A. J. Husbard (Ed.), CRC Press. press)

(in

HEYES, M. P., BREW, B. J., MARTIN, A., and PRICE, R. W. (1991) Quinolinic Acid in Cerebrospinal Fluid and Serum in HIV-l Infection: Relationship to Clinical and Neurological Status. Ann. of Neur. 29: 202-209. HUTCHINS, X. D., DICKSON, D. W., RASHBAUM, W. X., LYMAN, W. D. (1990) Localization of morphologically distinct microglial populations in the developing human fetal brain: Implications for ontogeny. Br. Res. 55: 95-102. JOHNSON, C. C. and FUCHS, B. A. (1991) Time dependent uptake of (-)'25 I-Iodocyanopindolol but Not (-)'251-Iodopindolol by murine splenic lymphocytes. J. of Receptor Res., Il, 959-964. XIECOLT-GLASER, J. X., and GLASER, R. (1991) Stress and immune function in humans. In: Psychoneuroimmunology, R. Ader, 0. L. Felten, and N. Cohen (Eds.), pp 849-868, 2nd Ed., Academic Press, New York. XULAGA, H., COGGAINO, M., RONNETT, G., SNYDER, S., WYATT, R. J., and SWEETNAM, P. (1991) HIV-l infection of the central nervous sytem: Characterization using a human cortical neuronal cell line. (under review)

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Neuroscience findings in AIDS the effect of cord blood and adult lymphocytes.

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Inquiries and requests

for reprints should be addressed

Dr. Will0 Pequegnat Office of AIDS Programs National Institute of Mental Health Parklawn Building, Room 17C-06 5600 Fishers Lane Rockville, Maryland 20857 U.S.A. Meetins

on Neuroscience

to:

(NIMH)

Findinas in AIDS Research

A two day meeting on Neuroscience Findings in AIDS Research was convened on February 20-21, 1991 by the Office of AIDS Programs, Office of the Director, National Institute of Mental Health (NIMH). Meetinq Orqanizers

Ellen Stover, Ph.D., NIMH Nancy A. Garrick, Ph.D., NIMH

170

W. Pequegnatetaf.

Co-Chairmen

Lee Eiden, Ph.D., NIMH David Felten, M.D., Ph.D., University of Rochester Ronald Glaser, Ph.D., Ohio State University William Lyman, Ph.D., Albert Einstein

Participants

De-Maw Chuang, Ph.D, NIMH Linda S. Crnic, Ph.D., University of Colorado P. B. Dews, M.B., Ch.B., Ph.D., Harvard University Berhard Dietzschold, D.V.M., The Wistar Institute Anita G. Eichler, M.P.H., NIMH Bruce A. Fuchs, Ph.D., Medical College of Virginia Arnold H. Greenberg, M.D., Ph.D., Manitoba Institute of Cell Biology Melvyn P. Heyes, Ph.D., NIMH Henrietta Kulaga, Ph.D., NIMH Martin T. Lowy, Ph.D., Case Western Reserve University Elisabeth A. Murray, Ph.D., NIMH David M. Neville, Jr., M.D., NIMH Will0 Pequegnat, Ph.D., NIMH Bruce S. Rabin, M.D., Ph.D., University of Pittsburgh Diane Rausch, Ph.D., NIMH Stanley Schwartz, M.D., Ph.D., University of Michigan Esther Sternberg, M.D., NIMH Syam Sundar, Ph.D., Duke University Jeffrey B. Tatro, Ph.D., Tufts University Jay M. Weiss, Ph.D., Duke University Bruce S. Zwilling, Ph.D., Ohio State University.