Simian immunodeficiency virus-infected rhesus macaques with AIDS co-develop cardiovascular pathology and encephalitis

Despite effective antiretroviral therapy, HIV co-morbidities remain where central nervous system (CNS) neurocognitive disorders and cardiovascular disease (CVD)-pathology that are linked with myeloid activation are most prevalent. Comorbidities such as neurocogntive dysfunction and cardiovascular disease (CVD) remain prevalent among people living with HIV. We sought to investigate if cardiac pathology (inflammation, fibrosis, cardiomyocyte damage) and CNS pathology (encephalitis) develop together during simian immunodeficiency virus (SIV) infection and if their co-development is linked with monocyte/macrophage activation. We used a cohort of SIV-infected rhesus macaques with rapid AIDS and demonstrated that SIV encephalitis (SIVE) and CVD pathology occur together more frequently than SIVE or CVD pathology alone. Their co-development correlated more strongly with activated myeloid cells, increased numbers of CD14+CD16+ monocytes, plasma CD163 and interleukin-18 (IL-18) than did SIVE or CVD pathology alone, or no pathology. Animals with both SIVE and CVD pathology had greater numbers of cardiac macrophages and increased collagen and monocyte/macrophage accumulation, which were better correlates of CVD-pathology than SIV-RNA. Animals with SIVE alone had higher levels of activated macrophage biomarkers and cardiac macrophage accumulation than SIVnoE animals. These observations were confirmed in HIV infected individuals with HIV encephalitis (HIVE) that had greater numbers of cardiac macrophages and fibrosis than HIV-infected controls without HIVE. These results underscore the notion that CNS and CVD pathologies frequently occur together in HIV and SIV infection, and demonstrate an unmet need for adjunctive therapies targeting macrophages.

Increased Macrophage-Specific Arterial Infiltration Relates to Non-calcified Plaque and Systemic Immune Activation in People with HIV

BACKGROUND

Persistent immune activation is thought to contribute to heightened atherosclerotic cardiovascular disease (ASCVD) risk among people with HIV (PWH).

METHODS

Participants (≥18 years) with versus without HIV and without history of clinical ASCVD were enrolled. We hypothesized that increased macrophage-specific arterial infiltration would relate to plaque composition and systemic immune activation among PWH. We applied a novel targeted molecular imaging approach [technetium-99  m (99mTc)-tilmanocept single photon emission computed tomography (SPECT)/CT] and comprehensive immune phenotyping.

RESULTS

Aortic 99mTc-tilmanocept uptake was significantly higher among PWH (N = 20) versus participants without HIV (N = 10) with similar 10-year ASCVD risk (P = 0.02). Among PWH, but not among participants without HIV, non-calcified aortic plaque volume related directly to aortic 99mTc-tilmanocept uptake at different uptake thresholds. An interaction (P = 0.001) was seen between HIV status and non-calcified plaque volume, but not calcified plaque (P = 0.83). Systemic levels of caspase-1 (P = 0.004), CD14-CD16+ (non-classical/patrolling/homing) monocytes (P = 0.0004) and CD8+ T-cells (P = 0.005) related positively and CD4+/CD8 + T-cell ratio (P = 0.02) inversely to aortic 99mTc-tilmanocept uptake volume.

CONCLUSIONS

Macrophage-specific arterial infiltration was higher among PWH and related to non-calcified aortic plaque volume only among PWH. Key systemic markers of immune activation relating to macrophage-specific arterial infiltration may contribute to heightened ASCVD risk among PWH.

Predator-Prey Dynamics of Intra-Host Simian Immunodeficiency Virus Evolution Within the Untreated Host

The dynamic nature of the SIV population during disease progression in the SIV/macaque model of AIDS and the factors responsible for its behavior have not been documented, largely owing to the lack of sufficient spatial and temporal sampling of both viral and host data from SIV-infected animals. In this study, we detail Bayesian coalescent inference of the changing collective intra-host viral effective population size (N_e ) from various tissues over the course of infection and its relationship with what we demonstrate is a continuously changing immune cell repertoire within the blood. Although the relative contribution of these factors varied among hosts and time points, the adaptive immune response best explained the overall periodic dynamic behavior of the effective virus population. Data exposing the nature of the relationship between the virus and immune cell populations revealed the plausibility of an eco-evolutionary mathematical model, which was able to mimic the large-scale oscillations in N_e through virus escape from relatively few, early immunodominant responses, followed by slower escape from several subdominant and weakened immune populations. The results of this study suggest that SIV diversity within the untreated host is governed by a predator-prey relationship, wherein differing phases of infection are the result of adaptation in response to varying immune responses. Previous investigations into viral population dynamics using sequence data have focused on single estimates of the effective viral population size (N_e ) or point estimates over sparse sampling data to provide insight into the precise impact of immune selection on virus adaptive behavior. Herein, we describe the use of the coalescent phylogenetic frame- work to estimate the relative changes in N_e over time in order to quantify the relationship with empirical data on the dynamic immune composition of the host. This relationship has allowed us to expand on earlier simulations to build a predator-prey model that explains the deterministic behavior of the virus over the course of disease progression. We show that sequential viral adaptation can occur in response to phases of varying immune pressure, providing a broader picture of the viral response throughout the entire course of progression to AIDS.

Brain tissue transcriptomic analysis of SIV-infected macaques identifies several altered metabolic pathways linked to neuropathogenesis and poly (ADP-ribose) polymerases (PARPs) as potential therapeutic targets

Despite improvements in antiretroviral therapy, human immunodeficiency virus type 1 (HIV-1)-associated neurocognitive disorders (HAND) remain prevalent in subjects undergoing therapy. HAND significantly affects individuals' quality of life, as well as adherence to therapy, and, despite the increasing understanding of neuropathogenesis, no definitive diagnostic or prognostic marker has been identified. We investigated transcriptomic profiles in frontal cortex tissues of Simian immunodeficiency virus (SIV)-infected Rhesus macaques sacrificed at different stages of infection. Gene expression was compared among SIV-infected animals (n = 11), with or without CD8+ lymphocyte depletion, based on detectable (n = 6) or non-detectable (n = 5) presence of the virus in frontal cortex tissues. Significant enrichment in activation of monocyte and macrophage cellular pathways was found in animals with detectable brain infection, independently from CD8+ lymphocyte depletion. In addition, transcripts of four poly (ADP-ribose) polymerases (PARPs) were up-regulated in the frontal cortex, which was confirmed by real-time polymerase chain reaction. Our results shed light on involvement of PARPs in SIV infection of the brain and their role in SIV-associated neurodegenerative processes. Inhibition of PARPs may provide an effective novel therapeutic target for HIV-related neuropathology.

Phyloanatomic characterization of the distinct T cell and monocyte contributions to the peripheral blood HIV population within the host

Human immunodeficiency virus (HIV) is a rapidly evolving virus, allowing its genetic sequence to act as a fingerprint for epidemiological processes among, as well as within, individual infected hosts. Though primarily infecting the CD4+ T-cell population, HIV can also be found in monocytes, an immune cell population that differs in several aspects from the canonical T-cell viral target. Using single genome viral sequencing and statistical phylogenetic inference, we investigated the viral RNA diversity and relative contribution of each of these immune cell types to the viral population within the peripheral blood. Results provide evidence of an increased prevalence of circulating monocytes harboring virus in individuals with high viral load in the absence of suppressive antiretroviral therapy. Bayesian phyloanatomic analysis of three of these individuals demonstrated a measurable role for these cells, but not the circulating T-cell population, as a source of cell-free virus in the plasma, supporting the hypothesis that these cells can act as an additional conduit of virus spread.

Rationale and design of the Mechanistic Substudy of the Randomized Trial to Prevent Vascular Events in HIV (REPRIEVE): Effects of pitavastatin on coronary artery disease and inflammatory biomarkers

BACKGROUND

People with HIV (PWH) have increased cardiovascular events, inflammation, and high-risk coronary atherosclerosis. Statin therapy has been shown to lower the risk of cardiovascular disease (CVD) in the general population, but whether this results from reductions in coronary atherosclerosis and is mediated by decreased inflammation remains unknown.

METHODS

REPRIEVE is a randomized, placebo-controlled trial of pitavastatin calcium (4 mg/day) vs. placebo enrolling at least 7500 PWH between 40-75 years, on antiretroviral therapy (ART), with low to moderate traditional CVD risk. The Mechanistic Substudy of REPRIEVE (A5333s) is co-enrolling 800 participants from 31 US sites. These participants undergo serial contrast enhanced coronary computed tomography angiography (CCTA) and measurements of biomarkers of inflammation and immune activation at baseline and after 2 years of follow-up. The primary objectives are to determine the effects of pitavastatin on noncalcified coronary atherosclerotic plaque (NCP) volume, low attenuation plaque, and positive remodeling and on changes in immune activation and inflammation and to assess relationships between the two. Changes in CAD will be assessed in a standardized fashion by a core lab with expert readers blinded to time points and participant information; immune activation and inflammation assessment is also performed centrally.

RESULTS

To date the Mechanistic Substudy has completed planned enrollment, with 805 participants.

CONCLUSION

This study represents the first large, randomized, CCTA-based assessment of the effects of a primary prevention strategy for CVD on high-risk CAD, immune activation and inflammation among PWH. The study will assess pitavastatin's effects on coronary plaque, and the interrelationship of these changes with biomarkers of immune activation and inflammation in PWH to determine mechanisms of CVD prevention and improved outcomes in this population.

Effects of Antiretroviral Therapy on Immune Function and Arterial Inflammation in Treatment-Naive Patients With Human Immunodeficiency Virus Infection

IMPORTANCE

Individuals with human immunodeficiency virus (HIV) infection receiving combined antiretroviral therapy (ART) have an increased risk of myocardial infarction. Effects of ART on arterial inflammation among treatment-naive individuals with HIV are unknown.

OBJECTIVE

To determine the effects of newly initiated ART on arterial inflammation and other immune/inflammatory indices in ART-naive patients with HIV infection.

DESIGN, SETTING, PARTICIPANTS

Twelve treatment-naive HIV-infected individuals underwent fludeoxyglucose F 18 ([18F]-FDG) positron emission tomographic scanning for assessment of arterial inflammation, coronary computed tomographic angiography for assessment of subclinical atherosclerosis, and systemic immune and metabolic phenotyping before and 6 months after the initiation of therapy with elvitegravir, cobicistat, emtricitabine, and tenofovir disoproxil fumarate (combined ART). Systemic immune and metabolic factors were also assessed in 12 prospectively recruited individuals without HIV serving as controls. The study began July 24, 2012, and was completed May 7, 2015.

INTERVENTIONS

Combined ART in the HIV-infected cohort.

MAIN OUTCOMES AND MEASURES

The primary outcome was change in aortic target-background ratio (TBR) on [18F]-FDG-PET with combined ART in the HIV-infected group.

RESULTS

For the 12 participants with HIV infection (mean (SD) age, 35 [11] years), combined ART suppressed viral load (mean [SD] log viral load, from 4.3 [0.6] to 1.3 [0] copies/mL; P < .001), increased the CD4+ T-cell count (median [IQR], from 461 [332-663] to 687 [533-882] cells/mm3; P < .001), and markedly reduced percentages of circulating activated CD4+ T cells (human leukocyte antigen-D related [HLA-DR]+CD38+CD4+) (from 3.7 [1.8-5.0] to 1.3 [0.3-2.0]; P = .008) and CD8+ T cells (HLA-DR+CD38+CD8+) (from 18.3 [8.1-27.0] to 4.0 [1.5-7.8]; P = .008), increased the percentage of circulating classical CD14+CD16- monocytes (from 85.8 [83.7-90.8] to 91.8 [87.5-93.2]; P = .04), and reduced levels of CXCL10 (mean [SD] log CXCL10, from 2.4 [0.4] to 2.2 [0.4] pg/mL; P = .03). With combined ART, uptake of [18F]-FDG in the axillary lymph nodes, as measured by TBR, decreased from a median (IQR) of 3.7 (1.3-7.0) at baseline to 1.4 (0.9-1.9; P = .01) at study end. In contrast, no significant decrease was seen in aortic TBR in response to combined ART (mean [SD], 1.9 [0.2]; median [IQR], 2.0 [1.8-2.1] at baseline to 2.2 [0.4]; 2.1 [1.9-2.6], respectively, at study end; P = .04 by 2-way test, P = .98 for test of decrease by 1-way test). Changes in aortic TBR during combined ART were significantly associated with changes in lipoprotein-associated phospholipase A2 (n = 10; r = 0.67; P = .03). Coronary plaque increased among 3 participants with HIV infection with baseline plaque and developed de novo in 1 participant during combined ART.

CONCLUSIONS AND RELEVANCE

Newly initiated combined ART in treatment-naive individuals with HIV infection had discordant effects to restore immune function without reducing arterial inflammation. Complementary strategies to reduce arterial inflammation among ART-treated HIV-infected individuals may be needed.

Hydrocephalus after Intrathecal Administration of Dextran to Rhesus Macaques (Macaca mulatta)

Dextrans have been used extensively as medical therapies and labeling agents in biomedical research to investigate the blood-brain barrier and CSF flow and absorption. Adverse effects from dextrans include anaphylactic reaction and dilation of the cerebral ventricles due to administration into the subarachnoid space. This retrospective study describes 51 rhesus macaques (Macaca mulatta) that received dextran intrathecally. The purpose of intrathecal administration was to enable detection of long-lived, dextran-labeled macrophages and to study monocyte-macrophage turnover in the CNS of SIV- or SHIV- infected and uninfected animals by using immunofluorescence. Of the 51 dextran-treated macaques, 8 that received dextran diluted in saline developed hydrocephalus; 6 of these 8 animals exhibited neurologic signs. In contrast, none of the macaques that received intrathecal dextran diluted in PBS developed hydrocephalus. These data suggest the use of saline diluent and the duration of dextran exposure as potential factors contributing to hydrocephalus after intrathecal dextran in rhesus macaques.

Temporal/compartmental changes in viral RNA and neuronal injury in a primate model of NeuroAIDS

Despite the advent of highly active anti-retroviral therapy HIV-associated neurocognitive disorders (HAND) continue to be a significant problem. Furthermore, the precise pathogenesis of this neurodegeneration is still unclear. The objective of this study was to examine the relationship between infection by the simian immunodeficiency virus (SIV) and neuronal injury in the rhesus macaque using in vivo and postmortem sampling techniques. The effect of SIV infection in 23 adult rhesus macaques was investigated using an accelerated NeuroAIDS model. Disease progression was modulated either with combination anti-retroviral therapy (cART, 4 animals) or minocycline (7 animals). Twelve animals remained untreated. Viral loads were monitored in the blood and cerebral spinal fluid, as were levels of activated monocytes in the blood. Neuronal injury was monitored in vivo using magnetic resonance spectroscopy. Viral RNA was quantified in brain tissue of each animal postmortem using reverse transcription polymerase chain reaction (RT-PCR), and neuronal injury was assessed by immunohistochemistry. Without treatment, viral RNA in plasma, cerebral spinal fluid, and brain tissue appears to reach a plateau. Neuronal injury was highly correlated both to plasma viral levels and a subset of infected/activated monocytes (CD14+CD16+), which are known to traffic the virus into the brain. Treatment with either cART or minocycline decreased brain viral levels and partially reversed alterations in in vivo and immunohistochemical markers for neuronal injury. These findings suggest there is significant turnover of replicating virus within the brain and the severity of neuronal injury is directly related to the brain viral load.

Animal models of HIV-associated disease of the central nervous system

It is difficult to study the pathogenesis of human immunodeficiency virus (HIV)-associated neurocognitive disorder (HAND) in living patients because central nervous system (CNS) tissues are only available post mortem. Rodent and nonhuman primate (NHP) models of HAND allow for longitudinal analysis of HIV-associated CNS pathology and efficacy studies of novel therapeutics. Rodent models of HAND allow for studies with large sample sizes, short duration, and relatively low cost. These models include humanized mice used to study HIV-associated neuropathogenesis and transgenic mice used to study neurotoxic effects of viral proteins without infection. Simian immunodeficiency virus (SIV)-infected NHP are the premier model of neuroAIDS; SIV-associated CNS pathology is similar to HIV-associated CNS pathology with HAND. Additionally, the size, lifespan of NHP, and time to acquired immune deficiency syndrome (AIDS) progression make SIV-infected NHP models optimal for studies of viral latency and reservoirs, and assessing novel therapeutics for neuroAIDS. NHP models of neuroAIDS generally include conventional progressors (AIDS within 2-3 years) and those that have rapid disease (AIDS within 150 days). Rapid AIDS models are achieved by immune modulation and/or infection with neurovirulent and neurosuppressive viral strains and result in a high incidence of SIV-associated encephalitis. In this chapter, we briefly review rodent and NHP models of neuroAIDS, including contributions made using these models to our understanding of HIV-associated CNS disease.

Monocyte subsets exhibit transcriptional plasticity and a shared response to interferon in SIV-infected rhesus macaques

The progression to AIDS is influenced by changes in the biology of heterogeneous monocyte subsets. Classical (CD14++CD16-), intermediate (CD14++CD16+), and nonclassical (CD14+CD16++) monocytes may represent progressive stages of monocyte maturation or disparate myeloid lineages with different turnover rates and function. To investigate the relationship between monocyte subsets and the response to SIV infection, we performed microarray analysis of monocyte subsets in rhesus macaques at three time points: prior to SIV infection, 26 days postinfection, and necropsy with AIDS. Genes with a 2-fold change between monocyte subsets (2023 genes) or infection time points (424 genes) were selected. We identify 172 genes differentially expressed among monocyte subsets in both uninfected and SIV-infected animals. Classical monocytes express genes associated with inflammatory responses and cell proliferation. Nonclassical monocytes express genes associated with activation, immune effector functions, and cell cycle inhibition. The classical and intermediate subsets are most similar at all time points, and transcriptional similarity between intermediate and nonclassical monocytes increases with AIDS. Cytosolic sensors of nucleic acids, restriction factors, and IFN-stimulated genes are induced in all three subsets with AIDS. We conclude that SIV infection alters the transcriptional relationship between monocyte subsets and that the innate immune response to SIV infection is conserved across monocyte subsets.

HDL Cholesterol Efflux Capacity in Newly Diagnosed HIV and Effects of Antiretroviral Therapy

CONTEXT

In the general population, high-density lipoprotein (HDL) cholesterol efflux capacity (HCEC) relates inversely to incident cardiovascular events. Previous studies have suggested that HCEC is decreased in HIV and that antiretroviral therapy (ART) initiation might improve HCEC.

OBJECTIVE

To evaluate HCEC in the context of ART initiation and immune activation in HIV.

DESIGN AND OUTCOME MEASURES

Baseline HCEC from 10 ART-naive HIV-infected males and 12 prospectively matched non-HIV-infected males were analyzed. In the HIV cohort, HCEC 6 months after elvitegravir/cobicistat/emtricitabine/tenofovir disoproxil fumarate (E/C/F/TDF) therapy was evaluated. HCEC served as the primary outcome and was measured by the ability of J774 mouse macrophages to efflux cholesterol. Our ex vivo assay used two cholesterol acceptors [apolipoprotein B (apoB)-depleted sera or purified HDL] and modulation of cellular efflux pathways using a liver X receptor (LXR) agonist.

RESULTS

The median age was 34 years [interquartile range (IQR), 27 to 51], and baseline HDL was 46 mg/dL (IQR, 38 to 61). HCEC was significantly greater in the non-HIV-infected subjects than in the HIV-infected subjects at baseline. HCEC, assessed using apoB-depleted sera, significantly increased after ART (no LXR agonist, baseline: median, 8.1%; IQR, 7.0% to 11.9%; after ART: median, 12.9%; IQR, 10.4% to 21.1%; P = 0.006; LXR agonist, baseline, 1.3% ± 1.3%; after ART, 2.5% ± 1.0%; P = 0.02), although not to the levels in the non-HIV-infected subjects (no LXR agonist: median, 14.9%; IQR, 11.5% to 19.1%; LXR agonist: 5.8% ± 1.3%). HCEC, assessed using purified HDL, did not significantly increase after ART. The change in HCEC with ART related inversely to the change in the percentage of CD14-CD16+ (nonclassical) monocytes (ρ = -0.74, P = 0.04) and directly to the change in the percentage of CD14+CD16- (classical) monocytes (ρ = 0.72, P = 0.045).

CONCLUSIONS

Our data suggest improvement of HCEC with E/C/F/TDF and a relationship between the ART-induced decrease in immune activation and ART-induced improvement in HCEC.

Application of a Novel CD206+ Macrophage-Specific Arterial Imaging Strategy in HIV-Infected Individuals

Background

The ability to noninvasively assess arterial CD206+ macrophages may lead to improved understanding of human immunodeficiency virus (HIV)-associated cardiovascular disease.

Methods

We trialed a novel macrophage-specific arterial imaging technique.

Results

We demonstrated colocalization between technetium Tc 99m tilmanocept (99mTc-tilmanocept) and CD206+ macrophages ex vivo. In vivo application of 99mTc-tilmanocept single-photon emission computed tomography/computed tomography revealed high-level 99mTc-tilmanocept uptake across 20.4% of the aortic surface volume among HIV-infected subjects, compared with 4.3% among non-HIV-infected subjects (P = .009). Among all subjects, aortic high-level 99mTc-tilmanocept uptake was related to noncalcified aortic plaque volume (r = 0.87; P = .003) on computed tomographic angiography, and this relationship held when we controlled for HIV status.

Conclusion

These first-in-human data introduce a novel macrophage-specific arterial imaging technique in HIV.

Clinical Trials Registration

NCT02542371.

An oral form of methylglyoxal-bis-guanylhydrazone reduces monocyte activation and traffic to the dorsal root ganglia in a primate model of HIV-peripheral neuropathy

Peripheral neuropathy (PN) is a major comorbidity of HIV infection that is caused in part by chronic immune activation. HIV-PN is associated with infiltration of monocytes/macrophages to the dorsal root ganglia (DRG) causing neuronal loss and formation of Nageotte nodules. Here, we used an oral form of methylglyoxal-bis-guanylhydrazone (MGBG), a polyamine biosynthesis inhibitor, to specifically reduce activation of myeloid cells. MGBG is selectively taken up by monocyte/macrophages in vitro and inhibits HIV p24 expression and DNA viral integration in macrophages. Here, MGBG was administered to nine SIV-infected, CD8-depleted rhesus macaques at 21 days post-infection (dpi). An additional nine SIV-infected, CD8-depleted rhesus macaques were used as untreated controls. Cell traffic to tissues was measured by in vivo BrdU pulse labeling. MGBG treatment significantly diminished DRG histopathology and reduced the number of CD68+ and CD163+ macrophages in DRG tissue. The number of recently trafficked BrdU+ cells in the DRG was significantly reduced with MGBG treatment. Despite diminished DRG pathology, intraepidermal nerve fiber density (IENFD) did not recover after treatment with MGBG. These data suggest that MGBG alleviated DRG pathology and inflammation.

Immunologic Pathways That Predict Mortality in HIV-Infected Ugandans Initiating Antiretroviral Therapy

The plasma kynurenine/tryptophan (KT) ratio, a marker of adaptive immune defects, strongly predicts mortality during treated human immunodeficiency virus (HIV) disease in Ugandans as compared to US-based populations. Here, the KT ratio and T-cell and plasma biomarkers of immune activation were measured among 535 HIV-infected Ugandans prior to ART initiation and at month 6 of viral suppression. The month 6 KT ratio (adjusted hazard ratio [aHR], 2.74), soluble CD14 level (aHR, 2.32), interleukin 6 level (aHR, 2.34), and D-dimer level (aHR, 1.95) were associated with mortality occurring ≥6 months after ART initiation. The KT ratio remained significantly predictive of mortality even after adjustment for the additional biomarkers, suggesting an independent contribution to clinical outcomes in resource-limited settings.

A method for obtaining simian immunodeficiency virus RNA sequences from laser capture microdissected and immune captured CD68+ and CD163+ macrophages from frozen tissue sections of bone marrow and brain

Laser capture microdissection (LCM) is used to extract cells or tissue regions for analysis of RNA, DNA or protein. Several methods of LCM are established for different applications, but a protocol for consistently obtaining lentiviral RNA from LCM captured immune cell populations is not described. Obtaining optimal viral RNA for analysis of viral genes from immune-captured cells using immunohistochemistry (IHC) and LCM is challenging. IHC protocols have long antibody incubation times that increase risk of RNA degradation. But, immune capture of specific cell populations like macrophages without staining for virus cannot result in obtaining only a fraction of cells which are productively lentivirally infected. In this study we sought to obtain simian immunodeficiency virus (SIV) RNA from SIV gp120+ and CD68+ monocyte/macrophages in bone marrow (BM) and CD163+ perivascular macrophages in brain of SIV-infected rhesus macaques. Here, we report an IHC protocol with RNase inhibitors that consistently results in optimal quantity and yield of lentiviral RNA from LCM-captured immune cells.

Effects of Sodium Restriction on Activation of the Renin-Angiotensin-Aldosterone System and Immune Indices During HIV Infection

BACKGROUND

 Human immunodeficiency virus (HIV)-infected patients demonstrate increased activation of the renin-angiotensin-aldosterone system (RAAS). We evaluated changes in immune markers with physiological RAAS activation.

METHODS

 Immune activation markers were assessed serially in 18 HIV-infected and 7 non-HIV-infected subjects consuming an ad libitum diet followed by a standardized low-sodium diet.

RESULTS

 Levels of CCL-2 (P = .0004) and soluble CD163 (P = .0001) significantly increased with sodium restriction and RAAS activation, compared with levels in individuals with ad libitum sodium intake, among chronically treated HIV-infected subjects (mean duration of ART [±SEM], 11 ± 1 years), but not among non-HIV-infected subjects of similar age and sex.

CONCLUSIONS

 Dietary sodium restriction, which activates RAAS, uniquely stimulates critical indices of immune activation during HIV infection.

CLINICAL TRIALS REGISTRATION

 NCT01407237.

α4-Integrin Antibody Treatment Blocks Monocyte/Macrophage Traffic to, Vascular Cell Adhesion Molecule-1 Expression in, and Pathology of the Dorsal Root Ganglia in an SIV Macaque Model of HIV-Peripheral Neuropathy

Traffic of activated monocytes into the dorsal root ganglia (DRG) is critical for pathology in HIV peripheral neuropathy. We have shown that accumulation of recently recruited (bromodeoxyuridine(+) MAC387(+)) monocytes is associated with severe DRG pathology and loss of intraepidermal nerve fibers in SIV-infected macaques. Herein, we blocked leukocyte traffic by treating animals with natalizumab, which binds to α4-integrins. SIV-infected CD8-depleted macaques treated with natalizumab either early (the day of infection) or late (28 days after infection) were compared with untreated SIV-infected animals sacrificed at similar times. Histopathology showed diminished DRG pathology with natalizumab treatment, including decreased inflammation, neuronophagia, and Nageotte nodules. Natalizumab treatment resulted in a decrease in the number of bromodeoxyuridine(+) (early), MAC387(+) (late), CD68(+) (early and late), and SIVp28(+) (late) macrophages in DRG tissues. The number of CD3(+) T lymphocytes in DRGs was not affected by natalizumab treatment. Vascular cell adhesion molecule 1, an adhesion molecule that mediates leukocyte traffic, was diminished in DRGs of all natalizumab-treated animals. These data show that blocking monocyte, but not T lymphocyte, traffic to the DRG results in decreased inflammation and pathology, supporting a role for monocyte traffic and activation in HIV peripheral neuropathy.

Associations between Cognition, Gender and Monocyte Activation among HIV Infected Individuals in Nigeria

The potential role of gender in the occurrence of HIV-related neurocognitive impairment (NCI) and associations with markers of HIV-related immune activity has not been previously examined. In this study 149 antiretroviral-naïve seropositive subjects in Nigeria (SP, 92 women and 57 men) and 58 seronegative (SN, 38 women and 20 men) were administered neuropsychological testing that assessed 7 ability domains. From the neuropsychological test scores was calculated a global deficit score (GDS), a measure of overall NCI. Percentages of circulating monocytes and plasma HIV RNA, soluble CD163 and soluble CD14 levels were also assessed. HIV SP women were found to be younger, more educated and had higher CD4+ T cell counts and borderline higher viral load measures than SP men. On the neuropsychological testing, SP women were more impaired in speed of information processing and verbal fluency and had a higher mean GDS than SN women. Compared to SP men, SP women were also more impaired in speed of information processing and verbal fluency as well as on tests of learning and memory. Numbers of circulating monocytes and plasma sCD14 and sCD163 levels were significantly higher for all SP versus all SN individuals and were also higher for SP women and for SP men versus their SN counterparts. Among SP women, soluble CD14 levels were slightly higher than for SP men, and SP women had higher viral load measurements and were more likely to have detectable virus than SP men. Higher sCD14 levels among SP women correlated with more severe global impairment, and higher viral load measurements correlated with higher monocyte numbers and sCD14 and sCD14 levels, associations that were not observed for SP men. These studies suggest that the risk of developing NCI differ for HIV infected women and men in Nigeria and, for women, may be linked to effects from higher plasma levels of HIV driving activation of circulating monocytes.

Anti-α4 Integrin Antibody Blocks Monocyte/Macrophage Traffic to the Heart and Decreases Cardiac Pathology in a SIV Infection Model of AIDS

Background

Cardiovascular disease (CVD), myocarditis and fibrosis are comorbidities of HIV⁺ individuals on durable antiretroviral therapy (ART). Although mechanisms for these vary, monocytes/macrophages are increasingly demonstrated to be key players.

Methods and Results

We directly blocked monocyte/macrophage traffic to the heart in an SIV model of AIDS using an anti-alpha-4 integrin antibody (natalizumab). Nineteen Rhesus macaques were SIVmac251 infected and CD8-lymphocyte depleted for the development of rapid AIDS. Ten animals received natalizumab once a week, for 3 weeks, and were sacrificed 1 week later. Six animals began treatment at the time of infection (early) and the remaining 4 began treatment 28 days post-infection (late), a time point we have previously established when significant cardiac inflammation occurs. Nine animals were untreated controls; of these, 3 were sacrificed early and 6 were sacrificed late. At necropsy, we found decreased SIV-associated cardiac pathology in late natalizumab-treated animals, compared to untreated controls. Early and late treatment resulted in significant reductions in numbers of CD163⁺ and CD68⁺ macrophages in cardiac tissues, compared to untreated controls, and a trend in decreasing numbers of newly recruited MAC387⁺ and BrdU⁺ (recruited) monocytes/macrophages. In late treated animals, decreased macrophage numbers in cardiac tissues correlated with decreased fibrosis. Early and late treatment resulted in decreased cardiomyocyte damage.

Conclusions

These data demonstrate a role for macrophages in the development of cardiac inflammation and fibrosis, and suggest that blocking monocyte/macrophage traffic to the heart can alleviate HIV- and SIV-associated myocarditis and fibrosis. They underscore the importance of targeting macrophage activation and traffic as an adjunctive therapy in HIV infection.

High expression levels of BLyS/BAFF by blood dendritic cells and granulocytes are associated with B-cell dysregulation in SIV-infected rhesus macaques

Dendritic cells (DCs) modulate B-cell survival and differentiation, mainly through production of growth factors such as B lymphocyte stimulator (BLyS/BAFF). In recent longitudinal studies involving HIV-1-infected individuals with different rates of disease progression, we have shown that DCs were altered in number and phenotype in the context of HIV-1 disease progression and B-cell dysregulations were associated with increased BLyS/BAFF expression in plasma and by blood myeloid DCs (mDCs) in rapid and classic progressors but not in HIV-1-elite controllers (EC). Suggesting that the extent to which HIV-1 disease progression is controlled may be linked to BLyS/BAFF expression status and the capacity to orchestrate B-cell responses. Herein, longitudinal analyses of simian immunodeficiency virus (SIV)-infected rhesus macaques also revealed increased expression of BLyS/BAFF by blood mDCs as soon as day 8 and throughout infection. Strikingly, granulocytes presented the highest BLyS/BAFF expression profile in the blood of SIV-infected macaques. BLyS/BAFF levels were also increased in plasma and correlated with viral loads. Consequently, these SIV-infected animals had plasma hyperglobulinemia and reduced blood B-cell numbers with altered population frequencies. These data underscore that BLyS/BAFF is associated with immune dysregulation in SIV-infected rhesus macaques and suggest that BLyS/BAFF is a key regulator of immune activation that is highly conserved among primates. These findings emphasize the potential importance of this SIV-infected primate model to test whether blocking excess BLyS/BAFF has an effect on the overall inflammatory burden and immune restoration.

Macrophage Polarization in AIDS: Dynamic Interface between Anti-Viral and Anti-Inflammatory Macrophages during Acute and Chronic Infection

Monocyte and macrophage inflammation in parenchymal tissues during acute and chronic HIV and SIV infection plays a role in early anti-viral immune responses and later in restorative responses. Macrophage polarization is observed in such responses in the central nervous system (CNS) and the heart and cardiac vessels that suggest early responses are M1 type antiviral responses, and later responses favor M2 restorative responses. Macrophage polarization is unique to different tissues and is likely dictated as much by the local microenvironment as well as other inflammatory cells involved in the viral responses. Such polarization is found in HIV infected humans, and the SIV infected animal model of AIDS, and occurs even with effective anti-retroviral therapy. Therapies that directly target macrophage polarization in HIV infection have recently been implemented, as have therapies to directly block traffic and accumulation of macrophages in tissues.

SIV encephalitis lesions are composed of CD163(+) macrophages present in the central nervous system during early SIV infection and SIV-positive macrophages recruited terminally with AIDS

Macrophage recruitment to the central nervous system (CNS) during AIDS pathogenesis is poorly understood. We measured the accumulation of brain perivascular (CD163(+)) and inflammatory (MAC387(+)) macrophages in SIV-infected monkeys. Monocyte progenitors were 5-bromo-2'-deoxyuridine (BrdU) labeled in bone marrow, and CNS macrophages were labeled serially with fluorescent dextrans injected into the cisterna magna. MAC387(+) macrophages accumulated in the meninges and choroid plexus in early inflammation and in the perivascular space and SIV encephalitis (SIVE) lesions late. CD163(+) macrophages accumulated in the perivascular space and SIVE lesions with late inflammation. Most of the BrdU(+) cells were MAC387(+); however, CD163(+)BrdU(+) macrophages were present in the meninges and choroid plexus with AIDS. Most (81.6% ± 1.8%) of macrophages in SIVE lesions were present in the CNS before SIVE lesion formation. There was a 2.9-fold increase in SIVp28(+) macrophages entering the CNS late compared with those entering early (P < 0.05). The rate of CD163(+) macrophage recruitment to the CNS inversely correlated with time to death (P < 0.03) and increased with SIVE. In SIVE animals, soluble CD163 correlated with CD163(+) macrophage recruitment (P = 0.02). Most perivascular macrophages that comprise SIVE lesions and multinucleated giant cells are present in the CNS early, before SIVE lesions are formed. Most SIV-infected macrophages traffic to the CNS terminally with AIDS.

Neuropharmacology of purinergic receptors in human submucous plexus: Involvement of P2X₁, P2X₂, P2X₃ channels, P2Y and A₃ metabotropic receptors in neurotransmission

RATIONALE

The role of purinergic signaling in human ENS is not well understood. We sought to further characterize the neuropharmacology of purinergic receptors in human ENS and test the hypothesis that endogenous purines are critical regulators of neurotransmission.

EXPERIMENTAL APPROACH

LSCM-Fluo-4/(Ca(2+))-imaging of postsynaptic Ca(2+) transients (PSCaTs) was used as a reporter of synaptic transmission evoked by fiber tract electrical stimulation in human SMP surgical preparations. Pharmacological analysis of purinergic signaling was done in 1,556 neurons (identified by HuC/D-immunoreactivity) in 235 ganglia from 107 patients; P2XR-immunoreactivity was evaluated in 19 patients. Real-time MSORT (Di-8-ANEPPS) imaging tested effects of adenosine on fast excitatory synaptic potentials (fEPSPs).

RESULTS

Synaptic transmission is sensitive to pharmacological manipulations that alter accumulation of extracellular purines: Apyrase blocks PSCaTs in a majority of neurons. An ecto-NTPDase-inhibitor 6-N,N-diethyl-D-β,γ-dibromomethyleneATP or adenosine deaminase augments PSCaTs. Blockade of reuptake/deamination of eADO inhibits PSCaTs. Adenosine inhibits fEPSPs and PSCaTs (IC50 = 25 µM), sensitive to MRS1220-antagonism (A3AR). A P2Y agonist ADPβS inhibits PSCaTs (IC50 = 111 nM) in neurons without stimulatory ADPbS responses (EC50 = 960 nM). ATP or a P2X1,2,2/3 (α,β-MeATP) agonist evokes fast, slow, biphasic Ca(2+) transients or Ca(2+) oscillations (ATP,EC50 = 400 mM). PSCaTs are sensitive to P2X1 antagonist NF279. Low (20 nM) or high (5 µM) concentrations of P2X antagonist TNP-ATP block PSCaTs in different neurons; proportions of neurons with P2XR-immunoreactivity follow the order P2X2 > P2X1 >> P2X3; P2X1 + P2X2 and P2X3 + P2X2 are co-localized. RT-PCR identified mRNA-transcripts for P2X1-7, P2Y1,2,12-14R.

CONCLUSIONS

Purines are critical regulators of neurotransmission in human ENS. Purinergic signaling involves P2X1, P2X2, P2X3 channels, P2X1 + P2X2 co-localization and inhibitory P2Y or A3 receptors. These are potential novel therapeutic targets for neurogastroenterology.

High-density lipoprotein-mediated cholesterol efflux capacity is improved by treatment with antiretroviral therapy in acute human immunodeficiency virus infection

Background

 Individuals infected with human immunodeficiency virus (HIV) have decreased high-density lipoprotein (HDL)-cholesterol and increased cardiovascular disease (CVD). Reverse cholesterol transport from macrophages may be inhibited by HIV and contribute to increased CVD. Human studies have not investigated longitudinal effects of HIV and antiretroviral therapy (ART) on cholesterol efflux.

Methods

 Subjects with acute HIV infection were randomized to ART or not. Cholesterol efflux capacity was determined ex vivo after exposure of murine macrophages to apolipoprotein B-depleted patient sera obtained at baseline and after 12 weeks.

Results

 After 12 weeks, HIV RNA decreased most in subjects randomized to ART. Available data on cholesterol demonstrated that efflux capacity from Abca1^+/+ macrophages was increased most by sera obtained from ART-treated subjects (20.5% ± 5.0% to 24.3 % ± 6.9%, baseline to 12 weeks, P = .007; ART group [n = 6] vs 18.0 % ± 3.9% to 19.1 % ± 2.9%, baseline to 12 weeks, P = .30; untreated group [n = 6] [P = .04 ART vs untreated group]). Change in HIV RNA was negatively associated with change in Abca1^+/+ macrophage cholesterol efflux (r = − 0.62, P = .03), and this finding remained significant (P = .03) after controlling for changes in HDL-cholesterol, CD4⁺ cells, and markers of monocyte or macrophage activation.

Conclusions

 In subjects acutely infected with HIV, ATP-binding cassette transporter A1-mediated cholesterol efflux was stimulated to a greater degree over time by apolipoprotein B-depleted serum from subjects randomized to ART. The improvement in cholesterol efflux capacity is independently related to reduction in viral load.

Anti-α4 antibody treatment blocks virus traffic to the brain and gut early, and stabilizes CNS injury late in infection

Four SIV-infected monkeys with high plasma virus and CNS injury were treated with an anti-α4 blocking antibody (natalizumab) once a week for three weeks beginning on 28 days post-infection (late). Infection in the brain and gut were quantified, and neuronal injury in the CNS was assessed by MR spectroscopy, and compared to controls with AIDS and SIV encephalitis. Treatment resulted in stabilization of ongoing neuronal injury (NAA/Cr by 1H MRS), and decreased numbers of monocytes/macrophages and productive infection (SIV p28⁺, RNA⁺) in brain and gut. Antibody treatment of six SIV infected monkeys at the time of infection (early) for 3 weeks blocked monocyte/macrophage traffic and infection in the CNS, and significantly decreased leukocyte traffic and infection in the gut. SIV – RNA and p28 was absent in the CNS and the gut. SIV DNA was undetectable in brains of five of six early treated macaques, but proviral DNA in guts of treated and control animals was equivalent. Early treated animals had low-to-no plasma LPS and sCD163. These results support the notion that monocyte/macrophage traffic late in infection drives neuronal injury and maintains CNS viral reservoirs and lesions. Leukocyte traffic early in infection seeds the CNS with virus and contributes to productive infection in the gut. Leukocyte traffic early contributes to gut pathology, bacterial translocation, and activation of innate immunity.

To determine whether ongoing cell traffic is required for SIV-associated tissue damage, we blocked monocyte and T lymphocyte traffic to the brain and gut during a) ongoing infection or, b) at the time of infection. When animals were treated at four weeks post infection (late), once significant neuronal injury and accumulation of infected macrophages had already occurred, neuronal injury was stabilized, and CNS infection and the number of CNS lesions decreased. In the gut, there were significantly fewer productively infected cells and decreased inflammatory macrophages post treatment. Treatment at the time of infection (early) blocked infection of the CNS (SIV –DNA, RNA, or protein) and macrophage accumulation. In the gut, treatment at the time of infection blocked productive infection (SIV –RNA and protein) but not SIV –DNA. Interestingly, with treatment at the time of infection, there was no evidence of microbial translocation or elevated sCD163 in plasma, demonstrating that leukocyte traffic early plays a role in damage to gut tissues. Overall, these data point to the role of monocyte traffic and possibly lymphocytes to the CNS and leukocyte traffic to the gut to establish and maintain viral reservoirs. They underscore the role of monocyte/macrophage traffic and accumulation in the CNS for neuronal injury and maintenance of CNS lesions.

Spatiotemporal dynamics of simian immunodeficiency virus brain infection in CD8+ lymphocyte-depleted rhesus macaques with neuroAIDS

Despite the success of combined antiretroviral therapy in controlling viral replication in human immunodeficiency virus (HIV)-infected individuals, HIV-associated neurocognitive disorders, commonly referred to as neuroAIDS, remain a frequent and poorly understood complication. Infection of CD8(+) lymphocyte-depleted rhesus macaques with the SIVmac251 viral swarm is a well-established rapid disease model of neuroAIDS that has provided critical insight into HIV-1-associated neurocognitive disorder onset and progression. However, no studies so far have characterized in depth the relationship between intra-host viral evolution and pathogenesis in this model. Simian immunodeficiency virus (SIV) env gp120 sequences were obtained from six infected animals. Sequences were sampled longitudinally from several lymphoid and non-lymphoid tissues, including individual lobes within the brain at necropsy, for four macaques; two animals were sacrificed at 21 days post-infection (p.i.) to evaluate early viral seeding of the brain. Bayesian phylodynamic and phylogeographic analyses of the sequence data were used to ascertain viral population dynamics and gene flow between peripheral and brain tissues, respectively. A steady increase in viral effective population size, with a peak occurring at ~50-80 days p.i., was observed across all longitudinally monitored macaques. Phylogeographic analysis indicated continual viral seeding of the brain from several peripheral tissues throughout infection, with the last migration event before terminal illness occurring in all macaques from cells within the bone marrow. The results strongly supported the role of infected bone marrow cells in HIV/SIV neuropathogenesis. In addition, our work demonstrated the applicability of Bayesian phylogeography to intra-host studies in order to assess the interplay between viral evolution and pathogenesis.

Elevated numbers of CD163+ macrophages in hearts of simian immunodeficiency virus-infected monkeys correlate with cardiac pathology and fibrosis

The role of macrophage activation, traffic, and accumulation on cardiac pathology was examined in 23 animals. Seventeen animals were simian immunodeficiency virus (SIV) infected, 12 were CD8 lymphocyte depleted, and the remaining six were uninfected controls (two CD8 lymphocyte depleted, four nondepleted). None of the uninfected controls had cardiac pathology. One of five (20%) SIV-infected, non-CD8 lymphocyte-depleted animals had minor cardiac pathology with increased numbers of macrophages in ventricular tissue compared to controls. Seven of the 12 (58%) SIV-infected, CD8 lymphocyte-depleted animals had cardiac pathology in ventricular tissues, including macrophage infiltration and myocardial degeneration. The extent of fibrosis (measured as the percentage of collagen per tissue area) was increased 41% in SIV-infected, CD8 lymphocyte-depleted animals with cardiac pathology compared to animals without pathological abnormalities. The number of CD163+ macrophages increased significantly in SIV-infected, CD8 lymphocyte-depleted animals with cardiac pathology compared to ones without pathology (1.66-fold) and controls (5.42-fold). The percent of collagen (percentage of collagen per total tissue area) positively correlated with macrophage numbers in ventricular tissue in SIV-infected animals. There was an increase of BrdU+ monocytes in the heart during late SIV infection, regardless of pathology. These data implicate monocyte/macrophage activation and accumulation in the development of cardiac pathology with SIV infection.

Identification and characterization of a macrophage-tropic SIV envelope glycoprotein variant in blood from early infection in SIVmac251-infected macaques

Macrophages play an important role in HIV/SIV pathogenesis by serving as a reservoir for viral persistence in brain and other tissues. Infected macrophages have been detected in brain early after infection, but macrophage-tropic viruses are rarely isolated until late-stage infection. Little is known about early variants that establish persistent infection in brain. Here, we characterize a unique macrophage-tropic SIV envelope glycoprotein (Env) variant from two weeks post-infection in blood of an SIVmac251-infected macaque that is closely related to sequences in brain from animals with neurological disease. SIVmac251 clones expressing this Env are highly fusogenic, and replicate efficiently in T cells and macrophages. N173 and N481 were identified as novel determinants of macrophage tropism and neutralization sensitivity. These results imply that macrophage-tropic SIV capable of establishing viral reservoirs in brain can be present in blood during early infection. Furthermore, these SIVmac251 clones will be useful for studies on pathogenesis, eradication, and vaccines.

Noncalcified coronary atherosclerotic plaque and immune activation in HIV-infected women

BACKGROUND

Little is known about coronary plaque in human immunodeficiency virus (HIV)-infected women.

METHODS

Sixty HIV-infected and 30 non-HIV-infected women without symptoms or history of cardiovascular disease were recruited to assess coronary plaque with coronary computed tomographic angiography and immune activation. Data from 102 HIV-infected men and 41 non-HIV-infected male controls were compared.

RESULTS

HIV-infected women demonstrated significantly higher percentages of segments with noncalcified plaque (mean ± SD, 74% ± 28% vs 23% ± 39% compared to female control subjects; median [interquartile range], 75% [63%-100%] vs 0% [0%-56%]; P = .007) and more segments with noncalcified plaque (mean ± SD, 0.92 ± 1.48 vs 0.40 ± 1.44; median [interquartile range], 0 [0-2] vs 0 [0-0]; P = .04). Immune activation parameters, including soluble CD163 (sCD163; P = .006), CXCL10 (P = .002), and percentages of CD14(+)CD16(+) monocytes (P = .008), were higher in HIV-infected women than in female control subjects, but no differences were seen in general inflammatory markers. Among HIV-infected women with noncalcified coronary plaque, sCD163 levels were significantly higher than in HIV-infected women without noncalcified plaque (P = .04). In multivariate modeling for sCD163 levels among male and female subjects, significant effects of HIV (P < .0001), age (P = .002), and sex (P = .0002) were seen.

CONCLUSIONS

Young, asymptomatic, HIV-infected women, demonstrate increased noncalcified coronary plaque and increased immune activation, particularly monocyte activation. Independent effects of sex, HIV status, and aging on immune activation may contribute to cardiovascular disease in this population.

CLINICAL TRIALS REGISTRATION

NCT00455793.

Monocyte/macrophages and their role in HIV neuropathogenesis

Neurological sequelae of human immunodeficiency virus (HIV) infection have been and remain a significant problem. Monocytes and macrophages in humans and monkeys are susceptible to infection by HIV and simian immunodeficiency virus (SIV), and are considered to be a main mechanism by which the central nervous system (CNS) is infected. Within the infected CNS, perivascular macrophages and, in some cases, parenchymal microglia are infected as are multinucleated giant cells when present. While neurons are not themselves directly infected, neuronal damage occurs within the infected CNS. Despite the success of antiretroviral therapy (ART) in limiting virus in plasma to non-detectable levels, neurological deficits persist. This review discusses the continued neurological dysfunctions that persist in the era of ART, focusing on the roles of monocyte and macrophage as targets of continued viral infection and as agents of pathogenesis in what appears to be emergent macrophage-mediated disease resulting from long-term HIV infection of the host. Data discussed include the biology of monocyte/macrophage activation with HIV and SIV infection, traffic of cells into and out of the CNS with infection, macrophage-associated biomarkers of CNS and cardiac disease, the role of antiretroviral therapy on these cells and CNS disease, as well as the need for effective adjunctive therapies targeting monocytes and macrophages.

Relationship between monocyte/macrophage activation marker soluble CD163 and insulin resistance in obese and normal-weight subjects

CONTEXT

The relationship of monocyte/macrophage activation to insulin resistance in obesity is unknown.

OBJECTIVE

To investigate a marker of macrophage activation, soluble CD163 (sCD163), in relationship to insulin resistance and metabolic parameters in obese and normal-weight subjects.

DESIGN AND PARTICIPANTS

Ninety-five healthy subjects (65 obese and 30 normal-weight) were studied. Plasma concentrations of sCD163 were assessed, as well as markers of glucose homeostasis, anthropometrics, cytokines and adipokines. The relationships between sCD163 and these parameters were investigated, and multiple regression modelling assessing the contribution of sCD163 to insulin resistance (HOMA-IR) was performed.

RESULTS

Soluble CD163 was significantly increased in obese subjects compared with normal-weight controls [974 (657, 1272) ng/ml vs 599 (423, 892) ng/ml, median (IQR); P < 0·0001]. sCD163 was strongly associated with HOMA-IR (Spearman's ρ = 0·37, P = 0·0003) and other metabolic parameters. In multiple regression modelling for log HOMA-IR, sCD163 remained significantly associated (P = 0·005) controlling for known mediators of insulin resistance including age, gender, visceral adiposity and inflammatory markers (model R(2) = 0·54, P < 0·0001). Additional nested multiple regression models for log HOMA-IR showed that sCD163 added more than other adipokines and inflammatory markers to the prediction of HOMA-IR.

CONCLUSIONS

Monocyte/macrophage activation, as reflected by sCD163 levels, is strongly associated with HOMA-IR in normal-weight and obese subjects after controlling for known mediators of insulin resistance. Moreover, sCD163 adds to standard risk markers for predicting insulin resistance. These data suggest that monocyte/macrophage activation may be an important determinant of insulin resistance in obesity.

Arterial inflammation in patients with HIV

CONTEXT

Cardiovascular disease is increased in patients with human immunodeficiency virus (HIV), but the specific mechanisms are unknown.

OBJECTIVE

To assess arterial wall inflammation in HIV, using 18fluorine-2-deoxy-D-glucose positron emission tomography (18F-FDG-PET), in relationship to traditional and nontraditional risk markers, including soluble CD163 (sCD163), a marker of monocyte and macrophage activation.

DESIGN, SETTING, AND PARTICIPANTS

A cross-sectional study of 81 participants investigated between November 2009 and July 2011 at the Massachusetts General Hospital. Twenty-seven participants with HIV without known cardiac disease underwent cardiac 18F-FDG-PET for assessment of arterial wall inflammation and coronary computed tomography scanning for coronary artery calcium. The HIV group was compared with 2 separate non-HIV control groups. One control group (n = 27) was matched to the HIV group for age, sex, and Framingham risk score (FRS) and had no known atherosclerotic disease (non-HIV FRS-matched controls). The second control group (n = 27) was matched on sex and selected based on the presence of known atherosclerotic disease (non-HIV atherosclerotic controls).

MAIN OUTCOME MEASURE

Arterial inflammation was prospectively determined as the ratio of FDG uptake in the arterial wall of the ascending aorta to venous background as the target-to-background ratio (TBR).

RESULTS

Participants with HIV demonstrated well-controlled HIV disease (mean [SD] CD4 cell count, 641 [288] cells/μL; median [interquartile range] HIV-RNA level, <48 [<48 to <48] copies/mL). All were receiving antiretroviral therapy (mean [SD] duration, 12.3 [4.3] years). The mean FRS was low in both HIV and non-HIV FRS-matched control participants (6.4; 95% CI, 4.8-8.0 vs 6.6; 95% CI, 4.9-8.2; P = .87). Arterial inflammation in the aorta (aortic TBR) was higher in the HIV group vs the non-HIV FRS-matched control group (2.23; 95% CI, 2.07-2.40 vs 1.89; 95% CI, 1.80-1.97; P < .001), but was similar compared with the non-HIV atherosclerotic control group (2.23; 95% CI, 2.07-2.40 vs 2.13; 95% CI, 2.03-2.23; P = .29). Aortic TBR remained significantly higher in the HIV group vs the non-HIV FRS-matched control group after adjusting for traditional cardiovascular risk factors (P = .002) and in stratified analyses among participants with undetectable viral load, zero calcium, FRS of less than 10, a low-density lipoprotein cholesterol level of less than 100 mg/dL (<2.59 mmol/L), no statin use, and no smoking (all P ≤ .01). Aortic TBR was associated with sCD163 level (P = .04) but not with C-reactive protein (P = .65) or D-dimer (P = .08) among patients with HIV.

CONCLUSION

Participants infected with HIV vs noninfected control participants with similar cardiac risk factors had signs of increased arterial inflammation, which was associated with a circulating marker of monocyte and macrophage activation.

Soluble CD163, a novel marker of activated macrophages, is elevated and associated with noncalcified coronary plaque in HIV-infected patients

BACKGROUND

Pro-inflammatory monocytes/macrophages may contribute to increased atherosclerosis in human immunodeficiency virus (HIV)-infected patients. We investigate--to our knowledge, for the first time--sCD163 and other markers of monocyte activation in relationship to atherosclerotic plaque in HIV-infected patients.

METHODS

One hundred two HIV-infected and 41 HIV-seronegative men with equivalent cardiovascular risk factors and without history of coronary artery disease were prospectively recruited and underwent computed tomography coronary angiography.

RESULTS

sCD163 levels and presence of plaque were significantly higher among antiretroviral-treated subjects with undetectable HIV RNA levels, compared with seronegative controls (1172 ± 646 vs. 883 ± 561 ng/mL [P = .02] for sCD163 and 61% vs. 39% [P = .03] for presence of plaque). After adjusting for age, race, lipids, blood pressure, glucose, smoking, sCD14, and HIV infection, sCD163 remained independently associated with noncalcified plaque (P = .008). Among HIV-infected patients, sCD163 was associated with coronary segments with noncalcified plaque (r = 0.21; P = .04), but not with calcium score. In contrast, markers of generalized inflammation, including C-reactive protein level, and D-dimer were not associated with sCD163 or plaque among HIV-infected patients.

CONCLUSIONS

sCD163, a monocyte/macrophage activation marker, is increased in association with noncalcified coronary plaque in men with chronic HIV infection and low or undetectable viremia. These data suggest a potentially important role of chronic monocyte/macrophage activation in the development of noncalcified vulnerable plaque.

CLINICAL TRIAL REGISTRATION

NCT00455793.

Soluble CD163 made by monocyte/macrophages is a novel marker of HIV activity in early and chronic infection prior to and after anti-retroviral therapy

CD163, a monocyte- and macrophage-specific scavenger receptor, is shed during activation as soluble CD163 (sCD163). We have previously demonstrated that monocyte expansion from bone marrow with simian immunodeficiency virus (SIV) infection correlated with plasma sCD163, the rate of AIDS progression, and the severity of macrophage-mediated pathogenesis. Here, we examined sCD163 in human immunodeficiency virus (HIV) infection. sCD163 was elevated in the plasma of individuals with chronic HIV infection (>1 year in duration), compared with HIV-seronegative individuals. With effective antiretroviral therapy (ART), sCD163 levels decreased in parallel with HIV RNA levels but did not return to HIV-seronegative levels, suggesting the presence of residual monocyte/macrophage activation even with plasma viral loads below the limit of detection. In individuals with early HIV infection (≤1 year in duration), effective ART resulted in decreased sCD163 levels that were comparable to levels in HIV-seronegative individuals. sCD163 levels in plasma were positively correlated with the percentage of CD14+CD16+ monocytes and activated CD8+HLA-DR+CD38+ T lymphocytes and were inversely correlated with CD163 expression on CD14+CD16+ monocytes. With ART interruption in subjects with early HIV infection, sCD163 and plasma virus levels spiked but rapidly returned to baseline with reinitiation of ART. This study points to the utility of monocyte- and macrophage-derived sCD163 as a marker of HIV activity that links viral replication with monocyte and macrophage activation. These observations underscore the significance of monocyte and macrophage immune responses with HIV pathogenesis.

Minocycline inhibition of monocyte activation correlates with neuronal protection in SIV neuroAIDS

Background

Minocycline is a tetracycline antibiotic that has been proposed as a potential conjunctive therapy for HIV-1 associated cognitive disorders. Precise mechanism(s) of minocycline's functions are not well defined.

Methods

Fourteen rhesus macaques were SIV infected and neuronal metabolites measured by proton magnetic resonance spectroscopy (¹H MRS). Seven received minocycline (4 mg/kg) daily starting at day 28 post-infection (pi). Monocyte expansion and activation were assessed by flow cytometry, cell traffic to lymph nodes, CD16 regulation, viral replication, and cytokine production were studied.

Results

Minocycline treatment decreased plasma virus and pro-inflammatory CD14+CD16+ and CD14^loCD16+ monocytes, and reduced their expression of CD11b, CD163, CD64, CCR2 and HLA-DR. There was reduced recruitment of monocyte/macrophages and productively infected cells in axillary lymph nodes. There was an inverse correlation between brain NAA/Cr (neuronal injury) and circulating CD14+CD16+ and CD14^loCD16+ monocytes. Minocycline treatment in vitro reduced SIV replication CD16 expression on activated CD14+CD16+ monocytes, and IL-6 production by monocytes following LPS stimulation.

Conclusion

Neuroprotective effects of minocycline are due in part to reduction of activated monocytes, monocyte traffic. Mechanisms for these effects include CD16 regulation, reduced viral replication, and inhibited immune activation.

CD8+ lymphocyte depletion without SIV infection does not produce metabolic changes or pathological abnormalities in the rhesus macaque brain

BACKGROUND

Simian immunodeficiency virus (SIV) infection and persistent CD8(+) lymphocyte depletion rapidly leads to encephalitis and neuronal injury. The objective of this study is to confirm that CD8 depletion alone does not induce brain lesions in the absence of SIV infection.

METHODS

Four rhesus macaques were monitored by proton magnetic resonance spectroscopy ((1) H-MRS) before and biweekly after anti-CD8 antibody treatment for 8 weeks and compared with four SIV-infected animals. Post-mortem immunohistochemistry was performed on these eight animals and compared with six uninfected, non-CD8-depleted controls.

RESULTS

CD8-depleted animals showed stable metabolite levels and revealed no neuronal injury, astrogliosis or microglial activation in contrast to SIV-infected animals.

CONCLUSIONS

Alterations observed in MRS and lesions in this accelerated model of neuroAIDS result from unrestricted viral expansion in the setting of immunodeficiency rather than from CD8(+) lymphocyte depletion alone.

Brain creatine elevation and N-Acetylaspartate reduction indicates neuronal dysfunction in the setting of enhanced glial energy metabolism in a macaque model of neuroAIDS

Proton magnetic resonance spectroscopy has emerged as one of the most informative neuroimaging modalities for studying the effect of HIV infection in the brain, providing surrogate markers by which to assess disease progression and monitor treatment. Reductions in the level of N-Acetylaspartate and N-Acetylaspartate/creatine are established markers of neuronal injury or loss. However, the biochemical basis of altered creatine levels in neuroAIDS is not well understood. This study used a rapid progression macaque model of neuroAIDS to elucidate the changes in creatine. As the disease progressed, proton magnetic resonance spectroscopy revealed a decrease in N-Acetylaspartate, indicative of neuronal injury, and an increase in creatine yet to be elucidated. Subsequently, immunohistochemistry and stereology measures of decreased synaptophysin, microtubule-associated protein 2, and neuronal density confirmed neuronal injury. Furthermore, increases in ionized calcium binding adaptor molecule 1 and glial fibrillary acidic protein indicated microglial and astroglial activation, respectively. Given these data, elevated creatine may reflect enhanced high-energy phosphate turnover in highly metabolizing activated astrocytes and microglia.

Evaluation of a 12-color flow cytometry panel to study lymphocyte, monocyte, and dendritic cell subsets in humans

Monitoring changes in human immune cell populations such as lymphocytes, monocytes, and dendritic cells (DCs) during infectious diseases like human immunodeficiency virus (HIV) is crucial. However, difficulties to identify rare or heterogeneous cell populations can be limiting. For example, to accurately measure DC subsets, eight flow cytometry parameters are ideal. The aim of this work was to analyze the phenotype of human lymphocyte, monocyte, and DC subsets using a single 12-color flow cytometry panel. After erythrocyte lysis, blood from healthy human volunteers was washed and labeled with a cocktail of 12 antibodies. Samples were analyzed on a Becton-Dickinson FACSAria equipped with three lasers. Data were compared with lineage-specific panels using 5-8 Ab combinations per lineage. Acquired data were analyzed using FlowJo software. Our 12-color panel allows for the identification of the following major subsets of circulating cells in a single tube: CD4+ and CD8+ T lymphocytes, B lymphocytes, NK cells, NKT cells, monocyte subsets (CD14 and/or CD16), and five nonoverlapping HLA-DR+Lin- subsets: CD34+ hematopoietic stem cells, CD123+ plasmacytoid DC, and three subsets of CD11c+ myeloid DC expressing either CD16, CD1c (BDCA-1), or CD141 (BDCA-3). We have developed a single flow cytometry panel that allows for simultaneous detection of the lymphocyte and monocyte cell populations and all known DC subsets. Studying these major players of the immune system in one single panel may give us a broader view of the immune response during HIV infection and the ability to better define the role of individual cell types in Acquired Immune Deficiency Syndrome (AIDS) pathogenesis. (c) 2010 International Society for Advancement of Cytometry.

Immunophenotyping of lymphocyte, monocyte and dendritic cell subsets in normal rhesus macaques by 12-color flow cytometry: clarification on DC heterogeneity

Monitoring changes in rhesus macaque immune cell populations during infectious disease is crucial. The aim of this work was to simultaneously analyze the phenotype of rhesus macaque lymphocyte, monocyte and dendritic cell (DC) subsets using a single 12-color flow cytometry panel. Blood from healthy non-infected rhesus macaques was labeled with a cocktail of 12 antibodies. Data were compared to three smaller lineage specific panels and absolute and relative percentages of cells were compared. Our 12-color panel allows for the identification of the following major subsets: CD4+ and CD8+ T lymphocytes, B lymphocytes, natural killer (NK) cells, natural killer T (NKT) cells, monocyte subsets and four non-overlapping Lin-HLA-DR+ cell subsets: CD34+ hematopoietic stem cells, CD11c- CD123+ plasmacytoid DC, CD11c+ CD16+ and CD11c(-)(/dim) CD1c+ myeloid DC. The development of a multiparameter flow cytometry panel will allow for simultaneous enumeration of mature lymphocyte, NK cells, monocyte and DC subsets. Studying these major players of the immune system in one panel may give us a broader view of the immune response during SIV infection and the ability to better define the role of each of these individual cell types in the pathogenesis of AIDS.

Proton magnetic resonance spectroscopy reveals neuroprotection by oral minocycline in a nonhuman primate model of accelerated NeuroAIDS

BACKGROUND

Despite the advent of highly active anti-retroviral therapy (HAART), HIV-associated neurocognitive disorders continue to be a significant problem. In efforts to understand and alleviate neurocognitive deficits associated with HIV, we used an accelerated simian immunodeficiency virus (SIV) macaque model of NeuroAIDS to test whether minocycline is neuroprotective against lentiviral-induced neuronal injury.

METHODOLOGY/PRINCIPAL FINDINGS

Eleven rhesus macaques were infected with SIV, depleted of CD8+ lymphocytes, and studied until eight weeks post inoculation (wpi). Seven animals received daily minocycline orally beginning at 4 wpi. Neuronal integrity was monitored in vivo by proton magnetic resonance spectroscopy and post-mortem by immunohistochemistry for synaptophysin (SYN), microtubule-associated protein 2 (MAP2), and neuronal counts. Astrogliosis and microglial activation were quantified by measuring glial fibrillary acidic protein (GFAP) and ionized calcium binding adaptor molecule 1 (IBA-1), respectively. SIV infection followed by CD8+ cell depletion induced a progressive decline in neuronal integrity evidenced by declining N-acetylaspartate/creatine (NAA/Cr), which was arrested with minocycline treatment. The recovery of this ratio was due to increases in NAA, indicating neuronal recovery, and decreases in Cr, likely reflecting downregulation of glial cell activation. SYN, MAP2, and neuronal counts were found to be higher in minocycline-treated animals compared to untreated animals while GFAP and IBA-1 expression were decreased compared to controls. CSF and plasma viral loads were lower in MN-treated animals.

CONCLUSIONS/SIGNIFICANCE

In conclusion, oral minocycline alleviates neuronal damage induced by the AIDS virus.

Increased monocyte turnover from bone marrow correlates with severity of SIV encephalitis and CD163 levels in plasma

Cells of the myeloid lineage are significant targets for human immunodeficiency virus (HIV) in humans and simian immunodeficiency virus (SIV) in monkeys. Monocytes play critical roles in innate and adaptive immunity during inflammation. We hypothesize that specific subsets of monocytes expand with AIDS and drive central nervous system (CNS) disease. Additionally, there may be expansion of cells from the bone marrow through blood with subsequent macrophage accumulation in tissues driving pathogenesis. To identify monocytes that recently emigrated from bone marrow, we used 5-bromo-2′-deoxyuridine (BrdU) labeling in a longitudinal study of SIV-infected CD8+ T lymphocyte depleted macaques. Monocyte expansion and kinetics in blood was assessed and newly migrated monocyte/macrophages were identified within the CNS. Five animals developed rapid AIDS with differing severity of SIVE. The percentages of BrdU+ monocytes in these animals increased dramatically, early after infection, peaking at necropsy where the percentage of BrdU+ monocytes correlated with the severity of SIVE. Early analysis revealed changes in the percentages of BrdU+ monocytes between slow and rapid progressors as early as 8 days and consistently by 27 days post infection. Soluble CD163 (sCD163) in plasma correlated with the percentage of BrdU+ monocytes in blood, demonstrating a relationship between monocyte activation and expansion with disease. BrdU+ monocytes/macrophages were found within perivascular spaces and SIVE lesions. The majority (80–90%) of the BrdU+ cells were Mac387+ that were not productively infected. There was a minor population of CD68+BrdU+ cells (<10%), very few of which were infected (<1% of total BrdU+ cells). Our results suggest that an increased rate of monocyte recruitment from bone marrow into the blood correlates with rapid progression to AIDS, and the magnitude of BrdU+ monocytes correlates with the severity of SIVE.

Human immunodeficiency virus (HIV) and the closely related simian immunodeficiency virus (SIV) can infect monocyte/macrophages, which enter and accumulate in the brain leading to neuronal dysfunction. Monocyte/macrophages exit the bone marrow, transit through the blood and enter the central nervous system (CNS). What triggers these cells to traffic is undefined, but it occurs in normal non-infected conditions at a rate that is accelerated with viral infection. Here, we used 5-bromo-2′-deoxyuridine (BrdU) injection and incorporation into the DNA of monocytes prior to their departure from the bone marrow. We found that the percentage of BrdU+ monocytes leaving the bone marrow 24 hours after injection increased in animals that rapidly succumbed to AIDS and correlated with the severity of SIV encephalitis (SIVE). Differences in BrdU labeled monocytes in slow and rapid progressors were revealed as early as 8 days and were consistent by 27 days post infection. Soluble CD163, shed by activated monocyte/macrophages, directly correlated with BrdU+ monocyte expansion. Our study provides new insights into the development of HIV-related CNS disease and underscores the importance of monocyte/macrophage recruitment from the bone marrow as an AIDS defining event.

HIV and SIV infection: the role of cellular restriction and immune responses in viral replication and pathogenesis

The human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) have a long biological history. Both viruses evolved from Africa and remnants of them can be found in the 'fossil record' of several species in which they are not endemic. SIV remains endemic in several species of monkeys in Africa where it does not cause immune deficiency. HIV and SIV actively replicate within humans and Asian non-human primates, despite cellular and genetic viral restriction factors and genes, and at times robust innate and adaptive immune responses. While Lentiviruses are considered 'slow viruses' it is clear in humans and susceptible Asian monkeys that virus production is rapid and highly active. This results in a massive loss of CD4+ memory effector T cells early after infection and a continued race between viral evolution, cytotoxic lymphocytes, and failed neutralizing antibody responses. Concurrently, HIV and SIV can infect monocyte/macrophage populations in blood and more importantly in tissues, including the central nervous system, where the virus can remain sequestered and not cleared by anti-retroviral therapy, and hide for years. This review will discuss species and cellular barriers to infection, and the role of innate and acquired immunity with infection and pathogenesis of HIV and SIV in select species.