Systems biology analyses reveal enhanced chronic morphine distortion of gut-brain interrelationships in simian human immunodeficiency virus infected rhesus macaques.

Background: Commonly used opioids, such as morphine have been implicated in augmented SIV/HIV persistence within the central nervous system (CNS). However, the extent of myeloid cell polarization and viral persistence in different brain regions remains unclear. Additionally, the additive effects of morphine on SIV/HIV dysregulation of gut-brain crosstalk remain underexplored. Therefore, studies focused on understanding how drugs of abuse such as morphine affect immune dynamics, viral persistence and gut-brain interrelationships are warranted. Materials and methods: For a total of 9 weeks, rhesus macaques were ramped-up, and twice daily injections of either morphine (n = 4) or saline (n = 4) administered. This was later followed with infection with SHIVAD8EO variants. At necropsy, mononuclear cells were isolated from diverse brain [frontal lobe, cerebellum, medulla, putamen, hippocampus (HIP) and subventricular zone (SVZ)] and gut [lamina propria (LP) and muscularis (MUSC) of ascending colon, duodenum, and ileum] regions. Multiparametric flow cytometry was used to were profile for myeloid cell polarity/activation and results corroborated with indirect immunofluorescence assays. Simian human immunodeficiency virus (SHIV) DNA levels were measured with aid of the digital droplet polymerase chain reaction (PCR) assay. Luminex assays were then used to evaluate soluble plasma/CSF biomarker levels. Finally, changes in the fecal microbiome were evaluated using 16S rRNA on the Illumina NovaSeq platform. Results: Flow Cytometry-based semi-supervised analysis revealed that morphine exposure led to exacerbated M1 (CD14/CD16)/M2 (CD163/CD206) polarization in activated microglia that spanned across diverse brain regions. This was accompanied by elevated SHIV DNA within the sites of neurogenesis-HIP and SVZ. HIP/SVZ CD16+ activated microglia positively correlated with SHIV DNA levels in the brain (r = 0.548, p = 0.042). Simultaneously, morphine dependence depleted butyrate-producing bacteria, including Ruminococcus (p = 0.05), Lachnospira (p = 0.068) genera and Roseburia_sp_831b (p = 0.068). Finally, morphine also altered the regulation of CNS inflammation by reducing the levels of IL1 Receptor antagonist (IL1Ra). Conclusion: These findings are suggestive that morphine promotes CNS inflammation by altering receptor modulation, increasing myeloid brain activation, distorting gut-brain crosstalk, and causing selective enhancement of SHIV persistence in sites of neurogenesis.

HIV-1 Nef hijacks both exocytic and endocytic pathways of host intracellular trafficking through differential regulation of Rab GTPases.

BACKGROUND: HIV-1 Nef regulates several cellular functions in an infected cell which results in viral persistence and AIDS pathogenesis. The currently understood molecular mechanism(s) underlying Nef-dependent cellular function(s) are unable to explain how events are coordinately regulated in the host cell. Intracellular membranous trafficking maintains cellular homeostasis and is regulated by Rab GTPases - a member of the Ras superfamily. RESULTS: In the current study, we tried to decipher the role of Nef on the Rab GTPases-dependent complex and vesicular trafficking. Expression profiling of Rabs in Nef-expressing cells showed that Nef differentially regulates the expression of individual Rabs in a cell-specific manner. Further analysis of Rabs in HIV-1NL4-3 or ΔNef infected cells demonstrated that the Nef protein is responsible for variation in Rabs expression. Using a panel of competitive peptide inhibitors against Nef, we identified the critical domain of HIV-1 Nef involved in modulation of Rabs expression. The molecular function of Nef-mediated upregulation of Rab5 and Rab7 and downregulation of Rab11 increased the transport of SERINC5 from the cell surface to the lysosomal compartment. Moreover, the Nef-dependent increase in Rab27 expression assists exosome release. Reversal of Rabs expression using competitive inhibitors against Nef and manipulation of Rabs expression reduced viral release and infectivity of progeny virions. CONCLUSION: This study demonstrates that Nef differentially regulates the expression of Rab proteins in HIV-1 infected cells to hijack the host intracellular trafficking, which augments viral replication and HIV-1 pathogenesis. SIGNIFICANCE: Our study emphasized the indispensable role of HIV-1 protein Nef on various aspects of the intracellular trafficking regulated by Rabs GTPases, which explained how HIV-1 Nef may hijack membrane trafficking pathways in infected cells.

Diminished Peripheral CD29hi Cytotoxic CD4+ T Cells Are Associated With Deleterious Effects During SIV Infection.

Cytotoxic CD4+ T cells (CD4+ CTLs) limit HIV pathogenesis, as evidenced in elite controllers (a subset of individuals who suppress the virus without the need for therapy). CD4+ CTLs have also been shown to kill HIV-infected macrophages. However, little is known about their contribution towards HIV persistence, how they are affected following exposure to immune modulators like morphine, and what factors maintain their frequencies and function. Further, the lack of robust markers to identify CD4+ CTLs in various animal models limits understanding of their role in HIV pathogenesis. We utilized various PBMC samples obtained from SIV infected and cART treated rhesus macaques exposed to morphine or saline and subjected to flow cytometry evaluations. Thereafter, we compared and correlated the expression of CD4+ CTL-specific markers to viral load and viral reservoir estimations in total CD4+ T cells. We found that CD29 could be reliably used as a marker to identify CD4+ CTLs in rhesus macaques since CD29hi CD4+ T cells secrete higher cytotoxic and proinflammatory cytokines following PMA/ionomycin or gag stimulation. In addition, this immune cell subset was depleted during untreated SIV infection. Strikingly, we also observed that early initiation of cART reconstitutes depleted CD29hi CD4+ T cells and restores their function. Furthermore, we noted that morphine exposure reduced the secretion of proinflammatory cytokines/cytotoxic molecules in CD29hi CD4+ T cells. Lastly, increased functionality of CD29hi CD4+ T cells as depicted by elevated levels of either IL-21 or granzyme B hi T Bet+ gag specific responses were linked to limiting the size of the replication-competent reservoir during cART treatment. Collectively, our data suggest that CD4+ CTLs are crucial in limiting SIV pathogenesis and persistence.

Chronic morphine administration differentially modulates viral reservoirs in SIVmac251 infected rhesus macaque model.

HIV persists in cellular reservoirs despite effective combined antiretroviral therapy (cART) and there is viremia flare up upon therapy interruption. Opioids modulate the immune system and suppress antiviral gene responses, which significantly impact people living with HIV (PLWH). However, the effect of opioids on viral reservoir dynamics remain elusive. Herein, we developed a morphine dependent SIVmac251 infected Rhesus macaque (RM) model to study the impact of opioids on HIV reservoirs. RMs on a morphine (or saline control) regimen were infected with SIVmac251. The cART was initiated in approximately half the animals five weeks post-infection, and morphine/saline administration continued until the end of the study. Among the untreated RM, we did not find any difference in plasma/CSF or in cell-associated DNA/RNA viral load in anatomical tissues. On the other hand, within the cART suppressed macaques, there was a reduction in cell-associated DNA load, intact proviral DNA levels, and in inducible SIV reservoir in lymph nodes (LNs) of morphine administered RMs. In distinction to LNs, in the CNS, the size of latent SIV reservoirs was higher in the CD11b+ microglia/macrophages in morphine dependent RMs. These results suggest that in the proposed model, morphine plays a differential role in SIV reservoirs by reducing the CD4+ T-cell reservoir in lymphoid tissues, while increasing the microglia/reservoir size in CNS tissue. The findings from this pre-clinical model will serve as a tool for screening therapeutic strategies to reduce/eliminate HIV reservoirs in opioid dependent PLWH.IMPORTANCE Identification and clearance of HIV reservoirs is a major challenge in achieving a cure for HIV. This is further complicated by co-morbidities that may alter the size of the reservoirs. There is an overlap between the risk factors for HIV and opioid abuse. Opiates have been recognized as prominent co-morbidities in HIV-infected populations. People infected with HIV also abusing opioids have immune modulatory effects and more severe neurological disease. However, the impact of opioid abuse on HIV reservoirs remains unclear. In this study, we used morphine dependent SIVmac251 infected rhesus macaque (RM) model to study the impact of opioids on HIV reservoirs. Our studies suggested that people with HIV who abuse opioids had higher reservoirs in CNS than the lymphoid system. Extrapolating the macaque findings in humans suggests that such differential modulation of HIV reservoirs among people living with HIV abusing opioids could be considered for future HIV cure research efforts.

Reactive Oxygen Species/Hypoxia-Inducible Factor-1α/Platelet-Derived Growth Factor-BB Autocrine Loop Contributes to Cocaine-Mediated Alveolar Epithelial Barrier Damage.

Abuse of psychostimulants, such as cocaine, has been shown to be closely associated with complications of the lung, such as pulmonary hypertension, edema, increased inflammation, and infection. However, the mechanism by which cocaine mediates impairment of alveolar epithelial barrier integrity that underlies various pulmonary complications has not been well determined. Herein, we investigate the role of cocaine in disrupting the alveolar epithelial barrier function and the associated signaling cascade. Using the combinatorial electric cell-substrate impedance sensing and FITC-dextran permeability assays, we demonstrated cocaine-mediated disruption of the alveolar epithelial barrier, as evidenced by increased epithelial monolayer permeability with a concomitant loss of the tight junction protein zonula occludens-1 (Zo-1) in both mouse primary alveolar epithelial cells and the alveolar epithelial cell line, L2 cells. To dissect the signaling pathways involved in this process, we demonstrated that cocaine-mediated induction of permeability factors, platelet-derived growth factor (PDGF-BB) and vascular endothelial growth factor, involved reactive oxygen species (ROS)-dependent induction of hypoxia-inducible factor (HIF)-1α. Interestingly, we demonstrated that ROS-dependent induction of another transcription factor, nuclear factor erythroid-2-related factor-2, that did not play a role in cocaine-mediated barrier dysfunction. Importantly, this study identifies, for the first time, that ROS/HIF-1α/PDGF-BB autocrine loop contributes to cocaine-mediated barrier disruption via amplification of oxidative stress and downstream signaling. Corroboration of these cell culture findings in vivo demonstrated increased permeability of the alveolar epithelial barrier, loss of expression of Zo-1, and a concomitantly increased expression of both HIF-1α and PDGF-BB. Pharmacological blocking of HIF-1α significantly abrogated cocaine-mediated loss of Zo-1. Understanding the mechanism(s) by which cocaine mediates barrier dysfunction could provide insights into the development of potential therapeutic targets for cocaine-mediated pulmonary hypertension.

Effects of Morphine on Behavioral Task Performance in SIV-Infected Rhesus Macaques.

The abuse of opiates such as morphine in synergy with HIV infection not only exacerbates neuropathogenesis but significantly impacts behavioral attributes in HIV infected subjects. Thus, the goal of the current study was to characterize behavioral perturbations in rhesus macaques subjected to chronic morphine and SIV infection. Specifically, we assessed three behavioral tasks: motor skill (MS), forelimb force (FFT) and progressive ratio (PR) tasks. After collecting baseline control data (44 weeks) and data during the morphine-only dependency period (26 weeks), a subset of animals were productively infected with neurovirulent strains of SIVmac (R71/E17) for an additional 33 weeks. A general pattern in the results is that behavioral decline occurred with high CSF viral loads but not necessarily with high plasma viral loads. Compared to saline controls, all treated animals showed significant decreases in performance on all three behavioral tasks during the morphine-only dependency period. During the post infection period, only the morphine plus SIV group showed a significant further decline and this only occurred for the MS task. Taken together, these data demonstrate a clear effect of morphine to produce behavioral deficits and also suggest that morphine can act synergistically with SIV/HIV to exacerbate behavioral deficits.

HIV-1 transgenic rats display mitochondrial abnormalities consistent with abnormal energy generation and distribution.

With the advent of the combination antiretroviral therapy era (cART), the development of AIDS has been largely limited in the USA. Unfortunately, despite the development of efficacious treatments, HIV-1-associated neurocognitive disorders (HAND) can still develop, and as many HIV-1 positive individuals age, the prevalence of HAND is likely to rise because HAND manifests in the brain with very low levels of virus. However, the mechanism producing this viral disorder is still debated. Interestingly, HIV-1 infection exposes neurons to proteins including Tat, Nef, and Vpr which can drastically alter mitochondrial properties. Mitochondrial dysfunction has been posited to be a cornerstone of the development of numerous neurodegenerative diseases. Therefore, we investigated mitochondria in an animal model of HAND. Using an HIV-1 transgenic rat model expressing seven of the nine HIV-1 viral proteins, mitochondrial functional and proteomic analysis were performed on a subset of mitochondria that are particularly sensitive to cellular changes, the neuronal synaptic mitochondria. Quantitative mass spectroscopic studies followed by statistical analysis revealed extensive proteome alteration in this model paralleling mitochondrial abnormalities identified in HIV-1 animal models and HIV-1-infected humans. Novel mitochondrial protein changes were discovered in the electron transport chain (ETC), the glycolytic pathways, mitochondrial trafficking proteins, and proteins involved in various energy pathways, and these findings correlated well with the function of the mitochondria as assessed by a mitochondrial coupling and flux assay. By targeting these proteins and proteins upstream in the same pathway, we may be able to limit the development of HAND.

Chronic SIV and morphine treatment increases heat shock protein 5 expression at the synapse.

The abuse of opiates such as morphine in synergy with HIV infection accelerates neurocognitive impairments and neuropathology in the CNS of HIV-infected subjects, collectively referred to as HAND. To identify potential pathogenic markers associated with HIV and morphine in perturbing the synaptic architecture, we performed quantitative mass spectrometry proteomics on purified synaptosomes isolated from the caudate of two groups of rhesus macaques chronically infected with SIV differing by one regimen-morphine treatment. The upregulation of heat shock 70-kDa protein 5 in the SIV + morphine group points to increased cellular stress during SIV/morphine interaction thus leading to CNS dysfunction.

Cannabinoid receptor 2 activation: a means to prevent monocyte-endothelium engagement.

This Commentary highlights the article by Rom et al which shows that selective cannabinoid receptor 2 activation in leukocytes decreases key steps in monocyte-blood brain barrier engagement suppressing inflammatory leukocyte responses and preventing neuroinflammation.

HIV-1 Tat-mediated neurotoxicity in retinal cells.

The current study was aimed at investigating the effect of HIV-1 protein Tat on the retinal neurosensory cell line R28. Exposure of Tat resulted in induction of pro-inflammatory mediators such as CXCL10 and TNF-α in addition to the activation marker GFAP in these cells. Conditioned media from Tat-treated R28 cells was able to induce monocyte migration, an effect that was blocked by CXCR3 antagonist. Complementary studies in the HIV-1 Tat-transgenic mice, showed a complete absence of the nuclear layer and the outer photoreceptor segments of the retina with a concomitant increase in glial activation. These findings lend support to the observation in post-HAART era of increased incidence of immune response-mediated retinal degeneration. These findings have direct relevance to diseases such as immune response uveitis and patients recovering from CMV retinitis.

Neuroimmune pharmacology as an emerging curriculum for pre-medical students.

As science continues to evolve and expand some major areas of interest are now crossing boundaries to become multi-disciplinary in nature closely reflecting the biological processes of the organism as a whole. The fields of neuroscience, immunology, and pharmacology are good examples of one such emerging inter-disciplinary area. This article is focused on developing a curriculum for undergraduate pre-medical students in the area of neuroimmune pharmacology (NIP) to empower them with the knowledge of neuroscience and its interaction with immune responses and drug interactions. This course is intended to amalgamate and put into perspective a large body of knowledge including: (1) brain function in health and disease, (2) cross talk between neural and immune responses, and (3) the pharmacology of drugs of abuse in the context of neurodegenerative diseases. The goal of this course is to expose pre-medical students to the field of NIP so that they are equipped with a solid foundation in these multidisciplinary fields for future clinical/academic careers.

HIV neuropathogenesis: a tight rope walk of innate immunity.

During the course of HIV-1 disease, virus neuroinvasion occurs as an early event, within weeks following infection. Intriguingly, subsequent central nervous system (CNS) complications manifest only decades after the initial virus exposure. Although CNS is commonly regarded as an immune-privileged site, emerging evidence indicates that innate immunity elicited by the CNS glial cells is a critical determinant for the establishment of protective immunity. Sustained expression of these protective immune responses, however, can be a double-edged sword. As protective immune mediators, cytokines have the ability to function in networks and co-operate with other host/viral mediators to tip the balance from a protective to toxic state in the CNS. Herein, we present an overview of some of the essential elements of the cerebral innate immunity in HIV neuropathogenesis including the key immune cell types of the CNS with their respective soluble immune mediators: (1) cooperative interaction of IFN-γ with the host/virus factor (platelet-derived host factor (PDGF)/viral Tat) in the induction of neurotoxic chemokine CXCL10 by macrophages, (2) response of astrocytes to viral infection, and (3) protective role of PDGF and MCP-1 in neuronal survival against HIV Tat toxicity. These components of the cerebral innate immunity do not act separately from each other but form a functional immunity network. The ultimate outcome of HIV infection in the CNS will thus be dependent on the regulation of the net balance of cell-specific protective versus detrimental responses.

A coat of many colors: neuroimmune crosstalk in human immunodeficiency virus infection.

The use of antiretroviral therapy has reduced mortality and increased the quality of life of HIV-1-infected people, particularly in more developed countries where access to treatment is more widespread. However, morbidities continue, which include HIV-1-associated neurocognitive disorders (HAND). Subtle cognitive abnormalities and low-level viral replication underlie disease. The balance between robust antiviral adaptive immunity, neuronal homeostatic mechanisms, and neuroprotective factors on one hand and toxicities afforded by dysregulated immune activities on the other govern disease. New insights into the pathobiological processes for neuroimmune-linked disease and ways to modulate such activities for therapeutic gain are discussed. Better understanding of the complexities of immune regulation during HAND can improve diagnosis and disease outcomes but is also relevant for the pathogenesis of a broad range of neurodegenerative disorders.

HIV-1 Tat co-operates with IFN-gamma and TNF-alpha to increase CXCL10 in human astrocytes.

HIV-associated neurological disorders (HAND) are estimated to affect 60% of the HIV infected population. HIV-encephalitis (HIVE), the pathological correlate of the most severe form of HAND is often characterized by glial activation, cytokine/chemokine dysregulation, and neuronal damage and loss. However, the severity of HIVE correlates better with glial activation rather than viral load. One of the characteristic features of HIVE is the increased amount of the neurotoxic chemokine, CXCL10. This chemokine can be released from astroglia activated with the pro-inflammatory cytokines IFN-gamma and TNF-alpha, in conjunction with HIV-1 Tat, all of which are elevated in HIVE. In an effort to understand the pathogenesis of HAND, this study was aimed at exploring the regulation of CXCL10 by cellular and viral factors during astrocyte activation. Specifically, the data herein demonstrate that the combined actions of HIV-1 Tat and the pro-inflammatory cytokines, IFN-gamma and TNF-alpha, result in the induction of CXCL10 at both the RNA and protein level. Furthermore, CXCL10 induction was found to be regulated transcriptionally by the activation of the p38, Jnk, and Akt signaling pathways and their downstream transcription factors, NF-kappaB and STAT-1alpha. Since CXCL10 levels are linked to disease severity, understanding its regulation could aid in the development of therapeutic intervention strategies for HAND.

Morphine enhances Tat-induced activation in murine microglia.

There is increasing evidence that opiates accelerate the pathogenesis and progression of acquired immunodeficiency syndrome (AIDS), as well as the incidence of human immunodeficiency virus (HIV) encephalitis (HIVE), a condition characterized by inflammation, leukocyte infiltration, and microglial activation. The mechanisms, by which the HIV-1 transactivating protein Tat and opioids exacerbate microglial activation, however, are not fully understood. In the current study, we explored the effects of morphine and HIV-1 Tat(1-72) on the activation of mouse BV-2 microglial cells and primary mouse microglia. Both morphine and Tat exposure caused up-regulation of the chemokine receptor CCR5, an effect blocked by the opioid receptor antagonist naltrexone. Morphine in combination with Tat also induced morphological changes in the BV-2 microglia from a quiescent to an activated morphology, with a dramatic increase in the expression of the microglial activation marker CD11b, as compared with cells exposed to either agent alone. In addition, the mRNA expression of inducible nitric oxide synthase (iNOS), CD40 ligand, Interferon-gamma-inducible protein 10 (IP-10), and the proinflammatory cytokines tumor necrosis factor alpha (TNFalpha), interleukin (IL)-1beta, and IL-6, which were elevated with Tat alone, were dramatically enhanced with Tat in the presence of morphine. In summary, these findings shed light on the cooperative effects of morphine and HIV-1 Tat on both microglial activation and HIV coreceptor up-regulation, effects that could result in exacerbated neuropathogenesis.

Proinflammatory cytokines and HIV-1 synergistically enhance CXCL10 expression in human astrocytes.

HIV encephalitis (HIVE), the pathologic correlate of HIV-associated dementia (HAD) is characterized by astrogliosis, cytokine/chemokine dysregulation, and neuronal degeneration. Increasing evidence suggests that inflammation is actively involved in the pathogenesis of HAD. In fact, the severity of HAD/HIVE correlates more closely with the presence of activated glial cells than with the presence and amount of HIV-infected cells in the brain. Astrocytes, the most numerous cell type within the brain, provide an important reservoir for the generation of inflammatory mediators, including interferon-gamma inducible peptide-10 (CXCL10), a neurotoxin and a chemoattractant, implicated in the pathophysiology of HAD. Additionally, the proinflammatory cytokines, IFN-gamma and TNF-alpha, are also markedly increased in CNS tissues during HIV-1 infection. In this study, we hypothesized that the interplay of host cytokines and HIV-1 could lead to enhanced expression of the toxic chemokine, CXCL10. Our findings demonstrate a synergistic induction of CXCL10 mRNA and protein in human astrocytes exposed to HIV-1 and the proinflammatory cytokines. Signaling molecules, including JAK, STATs, MAPK (via activation of Erk1/2, AKT, and p38), and NF-kappaB were identified as instrumental in the synergistic induction of CXCL10. Understanding the mechanisms involved in HIV-1 and cytokine-mediated up-regulation of CXCL10 could aid in the development of therapeutic modalities for HAD.

Cocaine-mediated alteration in tight junction protein expression and modulation of CCL2/CCR2 axis across the blood-brain barrier: implications for HIV-dementia.

One of the hallmark features underlying the pathogenesis of HIV encephalitis is the disruption of blood-brain barrier (BBB). Cocaine, often abused by HIV-infected patients, has been suggested to worsen the HIV-associated dementia (HAD) via unknown mechanisms. The objective of the present study was to explore the effects of cocaine on BBB permeability using human brain microvascular endothelial cells (HBMECs). Additionally, because the chemokine CCL2 and its receptor CCR2 play a crucial role in the recruitment of inflammatory cells into the central nervous system in HAD brains, we tested for the effect of cocaine in modulating the CCL2/CCR2 axis. Our findings suggest that exposure of HBMECs to cocaine correlated with the breakdown of ZO-1 tight junction protein and reorganization of the cytoskeleton resulting in stress fiber formation. Furthermore, cocaine also modulated upregulation of the CCL2/CCR2 axis in monocytes. These findings conform to the multifaceted effects of cocaine leading to accelerated progression of HIV-1 neuropathogenesis.

Cocaine-mediated enhancement of virus replication in macrophages: implications for human immunodeficiency virus-associated dementia.

Injection drug use has been recognized as a major risk factor for acquired immunodeficiency syndrome (AIDS) from the outset of the epidemic. Cocaine, one of the most widely abused drugs in the United States, can both impair the functions of macrophages and CD4(+) lymphocytes and also activate human immunodeficiency virus (HIV)-1 expression in these cells. Because the brain is the target organ for both cocaine and HIV, the objective of the present study was to explore the effects of cocaine on virus replication in macrophages, the target cells for the virus in the central nervous system (CNS). Cocaine markedly enhanced virus production in simian human immunodeficiency virus (SHIV)-infected monocyte-derived macrophages (MDMs) and in U1 cells, a chronically infected promonocytic cell line as monitored by enzyme-linked immunosorbent assay (ELISA) and immunocytochemistry. Cocaine treatment also resulted in the activation of nuclear factor (NF)-kappa B and transcriptional activation of the HIV-LTR (long terminal repeat) gag-GFP (green fluorescent protein). Analyses of chemokines in cocaine-treated macrophages by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and Luminex assays suggested increased expression of interleukin (IL)-10, a cytokine that is known to promote HIV replication in MDMs. In addition to enhancing IL-10 expression, cocaine also caused an up-regulation of the macrophage activation marker, human leukocyte antigen (HLA)-DR, in MDMs. The synergistic effect of cocaine on virus replication and its enhancement of host activation markers suggest that cocaine functions at multiple pathways to accelerate HIV-associated dementia (HAD).

Chronic morphine exposure causes pronounced virus replication in cerebral compartment and accelerated onset of AIDS in SIV/SHIV-infected Indian rhesus macaques.

Six morphine-exposed and 3 control male Indian rhesus macaques were intravenously inoculated with mixture of SHIV(KU), SHIV(89.6)P and SIV/17E-Fr. These animals were followed for a period of 56 weeks in order to determine CD4 and CD8 profile, viral loads in plasma and cerebrospinal fluid (CSF), relative distribution of 3 pathogenic viruses in blood and brain, binding as well neutralizing antibody levels and cellular immune responses. Both morphine-exposed and control macaques showed a precipitous loss of CD4+ T cells; control animals, however, showed a greater tendency to recover these cells than did their morphine-exposed counterparts. The plasma and CSF viral loads were significantly higher in morphine-exposed group than those in the control group. Four morphine-exposed animals succumbed to SIV/SHIV-induced AIDS at week 18, 19, 20 and 51; post-infection with neurological disorders was found in 3 of the 4 animals. At the end of the 56-week observation period, 2 morphine-exposed and 3 control animals were still alive. All 3 viruses replicated in the blood of both morphine-exposed and control macaques, but the cerebral compartment showed a selection phenomenon; only SIV/17E-Fr and SHIV(KU) successfully crossed the blood brain barrier (BBB). The morphine-exposed macaques further favored viral migration through the blood brain barrier (BBB). SIV/17E-Fr crossed the BBB within 2 weeks in both morphine-exposed and control macaques, whereas SHIV(KU) crossed the BBB more rapidly in morphine-exposed than in control macaques. Three morphine-exposed macaques (euthanized at weeks 18, 19 and 20) did not develop cellular or humoral immune responses, whereas the other 3 morphine-exposed and 3 control macaques developed both cellular and humoral immune responses.

Innate differences between simian-human immunodeficiency virus (SHIV)(KU-2)-infected rhesus and pig-tailed macaques in development of neurological disease.

Neurological disease associated with HIV infection results from either primary replication of the virus or a combination of virus infection and replication of opportunistic pathogens in the CNS. Recent studies indicate that the primary infection is mediated mainly by viruses that utilize CCR5 as the coreceptor; it is not known whether the syndrome can be mediated by viruses that use the CXCR4 coreceptor. The macaque model of the disease using simian immunodeficiency virus (SIV) has confirmed that CCR5-using viruses such as SIV(mac)251 can cause primary disease in the CNS. In this report we have examined the role of simian-human immunodeficiency virus (SHIV)(KU-2), a CXCR4 virus which replicates productively in rhesus macrophages, in causing CNS disease. A survey of archival brain tissues from SHIV(KU-2)-infected rhesus and pig-tailed macaques that succumbed to AIDS showed productive viral replication in the CNS of 10 of 14 rhesus animals. Eight of these 10 had additional infections with opportunistic pathogens. In contrast, 21 of 22 pig-tailed macaques had no evidence of productive viral infection in the brain. In an earlier study we had shown that inoculation of SHIV-infected rhesus macaques with eggs of Schistosoma mansoni, a potent inducer of IL-4, resulted in enhanced replication of the virus in tissue macrophages. In the present study, we compared the replication of the virus in macrophages from normal rhesus and pig-tailed macaques and determined further whether exogenous IL-4 could cause enhancement of virus replication in these cells. These studies showed that the virus replicated productively in rhesus macrophages, and this was enhanced significantly after recombinant macaque IL-4 was added to the medium. IL-4 also caused enhancement of virus production in macrophages isolated from virus-infected animals. In contrast, the virus replicated only minimally in pig-tailed macaque macrophages and supplemental IL-4 had negligible effects. The data thus suggested that failure of pig-tailed macaques to develop encephalitis was due to the innate resistance of macrophages from this species of macaque to support replication of SHIV(KU-2). The ability of the virus to replicate in the brains of rhesus macaques was dependent on coinfection in the brain with opportunistic pathogens which presumably induced both macrophages and IL-4 in the CNS microenvironment. A supportive role for IL-4 in the CNS disease was suggested by the presence of IL-4 RNA in the encephalitic brains of rhesus macaques and reduced levels of this cytokine in the brains from pig-tailed macaques.