Plasma levels of soluble CD14 and tumor necrosis factor-alpha type II receptor correlate with cognitive dysfunction during human immunodeficiency virus type 1 infection

Depression, Inflammation, and Intestinal Permeability: Associations with Subjective and Objective Cognitive Functioning throughout Breast Cancer Survivorship

About one-in-three breast cancer survivors have lingering cognitive complaints and objective cognitive impairment. Chronic inflammation and intestinal permeability (i.e., leaky gut), two risk factors for cognitive decline, can also fuel depression-another vulnerability for cognitive decline. The current study tested whether depression accompanied by high levels of inflammation or intestinal permeability predicted lower subjective and objective cognitive function in breast cancer survivors. We combined data from four breast cancer survivor studies (n = 613); some had repeated measurements for a total of 1015 study visits. All participants had a blood draw to obtain baseline measures of lipopolysaccharide binding protein-a measure of intestinal permeability, as well as three inflammatory markers that were incorporated into an inflammatory index: C-reactive protein, interleukin-6, and tumor necrosis factor-α. They reported depressive symptoms on the Center for Epidemiological Studies depression scale (CES-D), and a binary variable indicated clinically significant depressive symptoms (CES-D ≥ 16). The Kohli (749 observations) and the Breast Cancer Prevention Trial (591 observations) scales assessed subjective cognitive function. Objective cognitive function tests included the trail-making test, Hopkins verbal learning test, Conners continuous performance test, n-back test, FAS test, and animal-naming test (239-246 observations). Adjusting for education, age, BMI, cancer treatment type, time since treatment, study visit, and fatigue, women who had clinically elevated depressive symptoms accompanied by heightened inflammation or intestinal permeability reported poorer focus and marginally poorer memory. However, poorer performance across objective cognitive measures was not specific to inflammation-associated depression. Rather, there was some evidence of lower verbal fluency; poorer attention, verbal learning and memory, and working memory; and difficulties with visuospatial search among depressed survivors, regardless of inflammation. By themselves, inflammation and intestinal permeability less consistently predicted subjective or objective cognitive function. Breast cancer survivors with clinically significant depressive symptoms accompanied by either elevated inflammation or intestinal permeability may perceive greater cognitive difficulty, even though depression-related objective cognitive deficits may not be specific to inflammation- or leaky-gut-associated depression.

Soluble CD14 is subtype-dependent in serum but not in cerebrospinal fluid in people with HIV

Monocytes and macrophages activation are crucial in human immunodeficiency virus (HIV) central nervous system (CNS) infection and HIV associated neurocognitive disorders (HAND) pathogenesis. The soluble form of CD14 (sCD14) is a marker of monocyte activation. We hypothesized that sCD14 levels would be lower in people with HIV-1 subtype C (HIV-1C) than in HIV-1B owing to a variant Tat cysteine dimotif (C30S31) with reduced chemotactic activity. A total of 68 paired cerebrospinal fluid (CSF) and blood samples from people with HIV (PWH); 27 samples of the HIV-1B subtype and 40 of the non-B HIV-1 subtypes (including 26,HIV-1C), and 18 HIV-negative controls were included. sCD14 levels were quantified using a high-sensitivity enzyme-linked immunosorbent assay. sCD14 increase in serum, but not in CSF, was higher in samples from HIV-1B than HIV-1C (p = 0.002; Cohen's d, 0.7). CSF or serum sCD14 values were not correlated with global deficit score or specific cognitive domains. The impact of HIV-1 on monocyte stimulation biomarkers evaluated by sCD14 in serum was subtype-dependent, higher in HIV-1B than HIV-1C, consistent with reduced chemotactic activity as hypothesized.

Redistribution of brain glucose metabolism in people with HIV after antiretroviral therapy initiation

OBJECTIVE

We evaluated brain glucose metabolism in people living with HIV (PWH) with [18F]-Fluoro-Deoxyglucose (FDG) PET/computed tomography (CT) before and after antiretroviral therapy (ART) initiation.

DESIGN

We conducted a longitudinal study wherein ART-naive late-presenting untreated PWH with CD4+ cell counts less than 100 cells/μl were prospectively assessed for FDG uptake at baseline and at 4-8 weeks (n = 22) and 19-26 months (n = 11) following ART initiation.

METHODS

Relative uptake in the subcortical regions (caudate, putamen and thalamus) and cortical regions (frontal, parietal, temporal and occipital cortices) were compared across time and correlated with biomarkers of disease activity and inflammation, in addition to being compared with a group of uninfected individuals (n = 10).

RESULTS

Before treatment initiation, putaminal and caudate relative FDG uptake values in PWH were significantly higher than in uninfected controls. Relative putaminal and thalamic uptake significantly decreased shortly following ART initiation, while frontal cortex values significantly increased. FDG uptake changes correlated with changes in CD4+ cell counts and viral load, and, in the thalamus, with IL-6R and sCD14. Approximately 2 years following ART initiation, there was further decrease in subcortical relative uptake values, reaching levels below those of uninfected controls.

CONCLUSION

Our findings support pretreatment basal ganglia and thalamic neuroinflammatory changes in PWH, which decrease after treatment with eventual unmasking of long-term irreversible neuronal damage. Meanwhile, increased frontal cortex metabolism following ART initiation suggests reversible cortical dysfunction which improves with virologic control and increased CD4+ cell counts. Early initiation of treatment after HIV diagnosis and secondary control of inflammation are thus necessary to halt neurological damage in PWH.

Elevated Plasma Levels of sCD14 and MCP-1 Are Associated With HIV Associated Neurocognitive Disorders Among Antiretroviral-Naive Individuals in Nigeria

BACKGROUND

Mononuclear cells play key roles in the pathogenesis of HIV-associated neurocognitive disorders (HAND). Limited studies have looked at the association of markers of monocyte activation with HAND in Africa. We examined this association among HIV-1-infected patients in Nigeria.

METHOD

A total of 190 HIV-infected treatment-naive participants with immune marker data were included in this cross-sectional study. Plasma levels of soluble CD14 (sCD14), soluble CD163, monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-alpha (TNF-α), and neopterin were measured. Demographically adjusted T scores obtained from a 7-domain neuropsychological test battery were generated, and functional status was assessed using activities of daily living questionnaire. Participants were classified as unimpaired, having asymptomatic neurocognitive impairment (ANI), mild neurocognitive disorder (MND), or HIV-associated dementia (HAD) in line with the "Frascati" criteria.

RESULTS

Thirty-two participants (16.8%) had ANI, 14 (7.4%) had MND, whereas none had HAD. In multivariable linear regression analyses, after adjusting for age, gender, education, CD4 count, and viral load, mean levels of sCD14 were higher among those with ANI and MND as compared with the unimpaired (P = 0.033 and 0.023, respectively). Similarly, the mean level of MCP-1 was greater among those with HAND as compared with the unimpaired (P = 0.047). There were also trends for higher levels of sCD163 and TNF-α among females with MND in univariable analyses.

CONCLUSIONS

Levels of monocyte activation markers correlate with the severity of impairment among individuals with HAND. The mechanisms that underlie these effects and the potential role of gender require further study.

Cerebrospinal Fluid and Plasma Lipopolysaccharide Levels in Human Immunodeficiency Virus Type 1 Infection and Associations With Inflammation, Blood-Brain Barrier Permeability, and Neuronal Injury

Human immunodeficiency virus (HIV) infection is associated with increased systemic microbial translocation, neuroinflammation, and occasionally, neuronal injury. Whether systemic lipopolysaccharide (LPS) penetrates into the brain and contributes to neuroinflammation remain unknown in HIV. Here, we measured plasma and cerebrospinal fluid (CSF) LPS levels along with biomarkers of neuroinflammation (white blood cell counts and 40 soluble markers) and neurofilament light chain (NfL). Notably, CSF LPS was undetectable in all samples, including 3 HIV-infected individuals with dementia. Increased plasma LPS, neuroinflammation, and blood-brain barrier (BBB) dysfunction were found in untreated HIV-infected individuals, but not in healthy or treated HIV-infected individuals. Plasma LPS levels were directly correlated with various markers of inflammation in both plasma and CSF, as well as with degree of BBB permeability but not with CSF NfL in HIV-infected subjects. These results suggest that the magnitude of microbial translocation associates with neuroinflammation and BBB permeability in HIV without direct penetration into the central nervous system.

Peripheral immune dysregulation in the ART era of HIV-associated neurocognitive impairments: A systematic review

Human immunodeficiency virus-associated neurocognitive impairment (HANI) remains problematic despite the effective use of antiretroviral therapy (ART) and viral suppression. A dysregulated immune response contributes to the development of HANI but findings on the association between peripheral blood immune markers and HANI have been inconsistent. We therefore conducted a systematic review of studies of the association of peripheral blood immune markers with neurocognitive performance in ART experienced HIV-positive participants. Thirty-seven studies were eligible, including 12 longitudinal studies and 25 cross-sectional studies. Findings consistently show that HIV-positive participants have altered immune marker levels, including elevated markers of monocyte activation (neopterin, sCD14, sCD163) and inflammation (CCL2, IL-8, IL-18, IP-10, IFN-α, sTNFR-II and TNF-α). These elevated levels persist in HIV-positive participants despite ART. The majority of studies found associations of HANI with immune markers, including those linked to monocyte activation (sCD14 and sCD163) and inflammation (IL-18 and IP-10). Despite the heterogeneity of studies reviewed, due to the presence of raised peripheral markers, our narrative review provides evidence of chronic inflammation despite ART. The raised levels of these markers may suggest certain mechanisms are active, potentially those involved in the neuropathophysiology of HANI.

Association of CD14 with incident dementia and markers of brain aging and injury

OBJECTIVE

To test the hypothesis that the inflammatory marker plasma soluble CD14 (sCD14) associates with incident dementia and related endophenotypes in 2 community-based cohorts.

METHODS

Our samples included the prospective community-based Framingham Heart Study (FHS) and Cardiovascular Health Study (CHS) cohorts. Plasma sCD14 was measured at baseline and related to the incidence of dementia, domains of cognitive function, and MRI-defined brain volumes. Follow-up for dementia occurred over a mean of 10 years (SD 4) in the FHS and a mean of 6 years (SD 3) in the CHS.

RESULTS

We studied 1,588 participants from the FHS (mean age 69 ± 6 years, 47% male, 131 incident events) and 3,129 participants from the CHS (mean age 72 ± 5 years, 41% male, 724 incident events) for the risk of incident dementia. Meta-analysis across the 2 cohorts showed that each SD unit increase in sCD14 was associated with a 12% increase in the risk of incident dementia (95% confidence interval 1.03-1.23; p = 0.01) following adjustments for age, sex, APOE ε4 status, and vascular risk factors. Higher levels of sCD14 were associated with various cognitive and MRI markers of accelerated brain aging in both cohorts and with a greater progression of brain atrophy and a decline in executive function in the FHS.

CONCLUSION

sCD14 is an inflammatory marker related to brain atrophy, cognitive decline, and incident dementia.

High Plasma Soluble CD163 During Infancy Is a Marker for Neurocognitive Outcomes in Early-Treated HIV-Infected Children

BACKGROUND

Monocyte activation may contribute to neuronal injury in aviremic HIV-infected adults; data are lacking in children. We examined the relation between monocyte activation markers and early and long-term neurodevelopmental outcomes in early-treated HIV-infected children.

SETTING

Prospective study of infant and child neurodevelopmental outcomes nested within a randomized clinical trial (NCT00428116) and extended cohort study in Kenya.

METHODS

HIV-infected infants (N = 67) initiated antiretroviral therapy (ART) at age <5 months. Plasma soluble (s) CD163 (sCD163), sCD14, and neopterin were measured before ART (entry) and 6 months later. Milestone attainment was ascertained monthly during 24 months, and neuropsychological tests were performed at 5.8-8.2 years after initiation of ART (N = 27). The relationship between neurodevelopment and sCD163, sCD14, and neopterin at entry and 6 months after ART was assessed using Cox proportional hazards models and linear regression.

RESULTS

Infants with high entry sCD163 had unexpected earlier attainment of supported sitting (5 vs 6 months; P = 0.006) and supported walking (10 vs 12 months; P = 0.02) with trends in adjusted analysis. Infants with high 6-month post-ART sCD163 attained speech later (17 vs 15 months; P = 0.006; adjusted hazard ratio, 0.47; P = 0.02), threw toys later (18 vs 17 months; P = 0.01; adjusted hazard ratio, 0.53; P = 0.04), and at median 6.8 years after ART, had worse neuropsychological test scores (adj. mean Z-score differences, cognition, -0.42; P = 0.07; short-term memory, -0.52; P = 0.08; nonverbal test performance, -0.39, P = 0.05).

CONCLUSIONS

Before ART, monocyte activation may reflect transient neuroprotective mechanisms in infants. After ART and viral suppression, monocyte activation may predict worse short- and long-term neurodevelopment outcomes.

Aging, comorbidities, and the importance of finding biomarkers for HIV-associated neurocognitive disorders

HIV-associated neurocognitive disorders (HAND) continue to affect a large proportion of persons living with HIV despite effective viral suppression with combined antiretroviral therapy (cART). Importantly, milder versions of HAND have become more prevalent. The pathogenesis of HAND in the era of cART appears to be multifactorial with contributions from central nervous system (CNS) damage that occur prior to starting cART, chronic immune activation, cART neurotoxicity, and various age-related comorbidities (i.e., cardiovascular and cerebrovascular disease, diabetes, hyperlipidemia). Individuals with HIV may experience premature aging, which could also contribute to cognitive impairment. Likewise, degenerative disorders aside from HAND increase with age and there is evidence of shared pathology between HAND and other neurodegenerative diseases, such as Alzheimer's disease, which can occur with or without co-existing HAND. Given the aforementioned complex interactions associated with HIV, cognitive impairment, and aging, it is important to consider an age-appropriate differential diagnosis for HAND as the HIV-positive population continues to grow older. These factors make the accuracy and reliability of the diagnosis of mild forms of HAND in an aging population of HIV-infected individuals challenging. The complexity of current diagnosis of mild HAND also highlights the need to develop reliable biomarkers. Ultimately, the identification of a set of specific biomarkers will be required to achieve early and accurate diagnosis, which will be necessary assuming specific treatments for HAND are developed.

Inflammation Relates to Poorer Complex Motor Performance Among Adults Living With HIV on Suppressive Antiretroviral Therapy

BACKGROUND

Inflammatory processes have been suggested to underlie early neurologic abnormalities among persons living with HIV (HIV-positive), such as deficits in complex motor function, that are purported to remit with effective antiretroviral therapy (ART). We hypothesized that HIV will have negative direct and indirect effects through inflammation on complex motor performance.

METHODS

The sample consisted of 90 ART-treated virally suppressed HIV-positive and 94 HIV-negative adults, aged 36-65 years, with balanced recruiting in each age decade (36-45, 46-55, and 56-65). Biomarkers of inflammation (d-dimer, IL-6, MCP-1/CCL2, sCD14, and TNF-α) were measured, and a composite inflammation burden score was calculated. Complex motor performance was evaluated using the Grooved Pegboard Test.

RESULTS

The HIV-positive group had worse complex motor performance (P = 0.001; Hedges g = -0.49) and a higher average inflammation burden composite score (P < 0.001; Hedges g = 0.78) than the HIV-negative group. Path analyses indicated that the indirect effect of HIV disease on complex motor performance through inflammation burden was statistically significant, accounting for 15.1% of the effect of HIV on complex motor performance.

CONCLUSIONS

Although neurologic findings (eg, deficits in motor speed/dexterity) commonly associated with HIV infection typically remit with ART, our analysis indicates that inflammation plays an important role in worse complex motor skills among HIV-positive adults. Future studies of strategies for managing chronic inflammation in HIV should consider using an inflammation burden composite and examining its effect on complex motor performance.

Neuropathogenesis of human immunodeficiency virus infection

Human immunodeficiency virus (HIV)-associated neurocognitive disorders (HAND) remain a common end-organ manifestation of viral infection. Subclinical and mild symptoms lead to neurocognitive and behavioral abnormalities. These are associated, in part, with viral penetrance and persistence in the central nervous system. Infections of peripheral blood monocytes, macrophages, and microglia are the primary drivers of neuroinflammation and neuronal impairments. While current antiretroviral therapy (ART) has reduced the incidence of HIV-associated dementia, milder forms of HAND continue. Depression, comorbid conditions such as infectious liver disease, drugs of abuse, antiretroviral drugs themselves, age-related neurodegenerative diseases, gastrointestinal maladies, and concurrent social and economic issues can make accurate diagnosis of HAND challenging. Increased life expectancy as a result of ART clearly creates this variety of comorbid conditions that often blur the link between the virus and disease. With the discovery of novel biomarkers, neuropsychologic testing, and imaging techniques to better diagnose HAND, the emergence of brain-penetrant ART, adjunctive therapies, longer life expectancy, and better understanding of disease pathogenesis, disease elimination is perhaps a realistic possibility. This review focuses on HIV-associated disease pathobiology with an eye towards changing trends in the face of widespread availability of ART.

Peripheral and cerebrospinal fluid immune activation and inflammation in chronically HIV-infected patients before and after virally suppressive combination antiretroviral therapy (cART)

Cerebrospinal fluid (CSF)/plasma HIV-RNA ratio has been associated with residual neurocognitive impairment on cART, leading us to hypothesize a specific peripheral and/or CSF immune feature in patients with high CSF/plasma ratio (≥ 1). In patients with diverse pre-cART CSF/plasma ratio (61/70 with CSF/plasma ratio < 1, L-CSF, 9/70 with CSF/plasma ratio ≥ 1, H-CSF), we investigated the effects of 12 months of effective cART on peripheral and CSF inflammatory markers, on T cell activation/maturation and HIV/CMV-specific intracellular cytokine pattern. We also studied the possible clinical association between peripheral/CSF pro-inflammatory milieu and neurocognitive screening tests (MMSE, FAB, IHDS). Prior to cART, the two groups were comparable for peripheral and CSF inflammation, T cell activation/proliferation and maturation, and HIV/CMV-specific response. Upon cART initiation, both H-CSF and L-CSF featured a significant reduction in plasma TNF-α and circulating CD8 activation, with a redistribution of memory/naïve T cell subsets in L-CSF alone. In the CSF compartment, cART seemed able to reduce pro-inflammatory cytokine/chemokine levels in both H-CSF and L-CSF patients. Interestingly, despite a reduction in the pro-inflammatory milieu, no changes were shown in neurocognitive screening tests in both patients' groups. We hereby show that 12-month cART is able to reduce intratechal and peripheral pro-inflammatory burden; a longer cART exposure and a more comprehensive neuropsychological evaluation might be necessary to gain a broader insight into the possible effects on neurocognitive performance.

Sex Differences in Select Non-communicable HIV-Associated Comorbidities: Exploring the Role of Systemic Immune Activation/Inflammation

PURPOSE OF THE REVIEW

The goals of this review are to (1) explore HIV-associated cardiovascular disease (CVD), neurocognitive impairment, and non-AIDS-defining cancers (NADC) as heterogeneous model disease states fuelled in part by systemic immune activation/inflammation; (2) consider sex differences in the epidemiology of these diseases in both high-resource and lower-resource settings; and (3) examine biological and environmental factors which may contribute to heightened systemic immune activation/inflammation specifically among women living with HIV (WLHIV).

RECENT FINDINGS

The observation that WLHIV have higher levels of systemic immune activation/inflammation than men living with HIV (MLHIV) may be relevant to sex differences in select non-communicable HIV-associated comorbidities. Heightened systemic immune activation among WLHIV may be influenced by sex-specific responses to the virus and to immunomodulatory agents, as well as by behavioral choices/comorbid conditions and perturbations in the hypothalamic-pituitary-gonadal axis. Additional research is needed to elucidate region-specific drivers of heightened systemic immune activation/inflammation among WLHIV and to determine whether WLHIV who present with one immune-mediated HIV-associated comorbidity (e.g., cognitive impairment) may be at increased risk for another (e.g., CVD, NADC). This kind of research would facilitate improved risk prediction for non-communicable HIV-associated comorbidities among WLHIV and the development of targeted immunomodulatory prevention strategies.

Peripheral TNFα elevations in abstinent alcoholics are associated with hepatitis C infection

Substantial evidence supports the view that inflammatory processes contribute to brain alterations in HIV infection. Mechanisms recently proposed to underlie neuropathology in Alcohol Use Disorder (AUD) include elevations in peripheral cytokines that sensitize the brain to the damaging effects of alcohol. This study included 4 groups: healthy controls, individuals with AUD (abstinent from alcohol at examination), those infected with HIV, and those comorbid for HIV and AUD. The aim was to determine whether inflammatory cytokines are elevated in AUD as they are in HIV infection. Cytokines showing group differences included interferon gamma-induced protein 10 (IP-10) and tumor necrosis factor α (TNFα). Follow-up t-tests revealed that TNFα and IP-10 were higher in AUD than controls but only in AUD patients who were seropositive for Hepatitis C virus (HCV). Specificity of TNFα and IP-10 elevations to HCV infection status was provided by correlations between cytokine levels and HCV viral load and indices of liver integrity including albumin/globulin ratio, fibrosis scores, and AST/platelet count ratio. Because TNFα levels were mediated by HCV infection, this study provides no evidence for elevations in peripheral cytokines in "uncomplicated", abstinent alcoholics, independent of liver disease or HCV infection. Nonetheless, these results corroborate evidence for elevations in IP-10 and TNFα in HIV and for IP-10 levels in HIV+HCV co-infection.

Clinical Relevance of Total HIV DNA in Peripheral Blood Mononuclear Cell Compartments as a Biomarker of HIV-Associated Neurocognitive Disorders (HAND)

The pathogenesis of HIV-associated neurocognitive disorders is complex and multifactorial. It is hypothesized that the critical events initiating this condition occur outside the brain, particularly in the peripheral blood. Diagnoses of HIV-induced neurocognitive disorders largely rely on neuropsychometric assessments, which are not precise. Total HIV DNA in the peripheral blood mononuclear cells (PBMCs), quantified by PCR, correlate with disease progression, which is a promising biomarker to predict HAND. Numerous PCR assays for HIV DNA in cell compartments are prone to variation due to the lack of standardization and, therefore, their utility in predicting HAND produced different outcomes. This review evaluates the clinical relevance of total HIV DNA in circulating mononuclear cells using different published quantitative PCR (qPCR) protocols. The rationale is to shed light on the most appropriate assays and sample types used to accurately quantify HIV DNA load, which predicts severity of neurocognitive impairment. The role of monocytes as a vehicle for trafficking HIV into the CNS makes it the most suitable sample for determining a HAND associated reservoir. Studies have also shown significant associations between monocyte HIV DNA levels with markers of neurodamage. However, qPCR assays using PBMCs are cheaper and available commercially, thus could be beneficial in clinical settings. There is need, however, to standardise DNA extraction, normalisation and limit of detection.

HIV/neuroAIDS biomarkers

HIV infection often causes neurological symptoms including cognitive and motor dysfunction, which have been collectively termed HIV/neuroAIDS. Neuropsychological assessment and clinical symptoms have been the primary diagnostic criteria for HIV/neuroAIDS, even for the mild cognitive and motor disorder, the most prevalent form of HIV/neuroAIDS in the era of combination antiretroviral therapy. Those performance-based assessments and symptoms are generally descriptive and do not have the sensitivity and specificity to monitor the diagnosis, progression, and treatment response of the disease when compared to objective and quantitative laboratory-based biological markers, or biomarkers. In addition, effects of demographics and comorbidities such as substance abuse, psychiatric disease, nutritional deficiencies, and co-infection on HIV/neuroAIDS could be more readily determined using biomarkers than using neuropsychological assessment and clinical symptoms. Thus, there have been great efforts in identification of HIV/neuroAIDS biomarkers over the past two decades. The need for reliable biomarkers of HIV/neuroAIDS is expected to increase as the HIV-infected population ages and their vulnerability to neurodegenerative diseases, particularly Alzheimer's disease increases. Currently, three classes of HIV/neuroAIDS biomarkers are being pursued to establish objective laboratory-based definitions of HIV-associated neurologic injury: cerebrospinal fluid biomarkers, blood biomarkers, and neuroimaging biomarkers. In this review, we will focus on the current knowledge in the field of HIV/neuroAIDS biomarker discovery.

HIV-1 Infection Primes Macrophages Through STAT Signaling to Promote Enhanced Inflammation and Viral Replication

Macrophages play important roles in HIV-1 pathogenesis as targets for viral replication and mediators of chronic inflammation. Similar to IFNγ-priming, HIV-1 primes macrophages, resulting in hyperresponsiveness to subsequent toll-like receptor (TLR) stimulation and increased inflammatory cytokine production. However, the specific molecular mechanism of HIV-1 priming and whether cells must be productively infected or if uninfected bystander cells also are primed by HIV-1 remains unclear. To explore these questions, human macrophages were primed by IFNγ or infected with HIV-1 before activation by TLR ligands. Transcriptome profiling by microarray revealed a gene expression profile for IFNγ-primed cells that was further modulated by the addition of lipopolysaccharide (LPS). HIV-1 infection elicited a gene expression profile that correlated strongly with the profile induced by IFNγ (r = .679, p = .003). Similar to IFNγ, HIV-1 enhanced TLR ligand-induced tumor necrosis factor (TNF) protein expression and release. Increased TNF production was limited to productively infected cells. Specific signal transducer and activator of transcription (STAT)1 and STAT3 inhibitors suppressed HIV-1-mediated enhancement of TLR-induced TNF expression as well as HIV-1 replication. These findings indicate that viral replication and inflammation are linked through a common IFNγ-like, STAT-dependent pathway and that HIV-1-induced STAT1 and STAT3 signaling are involved in both inflammation and HIV-1 replication. Systemic innate immune activation is a hallmark of active HIV-1 replication. Our study shows that inflammation may develop as a consequence of HIV-1 triggering STAT-IFN pathways to support viral replication.

Immune activation and neuroinflammation in alcohol use and HIV infection: evidence for shared mechanisms

BACKGROUND

Emerging research points to innate immune mechanisms in the neuropathological and behavioral consequences of heavy alcohol use. Alcohol use is common among people living with HIV infection (PLWH), a chronic condition that carries its own set of long-term effects on brain and behavior. Notably, neurobiological and cognitive profiles associated with heavy alcohol use and HIV infection share several prominent features. This observation raises questions about interacting biological mechanisms as well as compounded impairment when HIV infection and heavy drinking co-occur.

OBJECTIVE AND METHOD

This narrative overview discusses peer-reviewed research on specific immune mechanisms of alcohol that exhibit apparent potential to compound the neurobiological and psychiatric sequelae of HIV infection. These include microbial translocation, systemic immune activation, blood-brain barrier compromise, microglial activation, and neuroinflammation.

RESULTS

Clinical and preclinical evidence supports overlapping mechanistic actions of HIV and alcohol use on peripheral and neural immune systems. In preclinical studies, innate immune signaling mediates many of the detrimental neurocognitive and behavioral effects of alcohol use. Neuropsychopharmacological research suggests potential for a feed-forward cycle in which heavy drinking induces innate immune signaling, which in turn stimulates subsequent alcohol use behavior.

CONCLUSION

Alcohol-induced immune activation and neuroinflammation are a serious health concern for PLWH. Future research to investigate specific immune effects of alcohol in the context of HIV infection has potential to identify novel targets for therapeutic intervention.

Autoimmune diseases, gastrointestinal disorders and the microbiome in schizophrenia: more than a gut feeling

Autoimmunity, gastrointestinal (GI) disorders and schizophrenia have been associated with one another for a long time. This paper reviews these connections and provides a context by which multiple risk factors for schizophrenia may be related. Epidemiological studies strongly link schizophrenia with autoimmune disorders including enteropathic celiac disease. Exposure to wheat gluten and bovine milk casein also contribute to non-celiac food sensitivities in susceptible individuals. Co-morbid GI inflammation accompanies humoral immunity to food antigens, occurs early during the course of schizophrenia and appears to be independent from antipsychotic-generated motility effects. This inflammation impacts endothelial barrier permeability and can precipitate translocation of gut bacteria into systemic circulation. Infection by the neurotropic gut pathogen, Toxoplasma gondii, will elicit an inflammatory GI environment. Such processes trigger innate immunity, including activation of complement C1q, which also functions at synapses in the brain. The emerging field of microbiome research lies at the center of these interactions with evidence that the abundance and diversity of resident gut microbiota contribute to digestion, inflammation, gut permeability and behavior. Dietary modifications of core bacterial compositions may explain inefficient gluten digestion and how immigrant status in certain situations is a risk factor for schizophrenia. Gut microbiome research in schizophrenia is in its infancy, but data in related fields suggest disease-associated altered phylogenetic compositions. In summary, this review surveys associative and experimental data linking autoimmunity, GI activity and schizophrenia, and proposes that understanding of disrupted biological pathways outside of the brain can lend valuable information regarding pathogeneses of complex, polygenic brain disorders.

Short Communication: Do Cytomegalovirus Antibody Levels Associate with Age-Related Syndromes in HIV Patients Stable on Antiretroviral Therapy?

HIV(+) persons stable on antiretroviral therapy (ART) face early onset of age-related diseases. This may arise from a high burden of cytomegalovirus (CMV). To address the role of CMV, we investigated univariate and multivariate associations between markers of systemic and endothelial inflammation, vascular damage, insulin resistance (IR), neurocognitive decline, and antibodies reactive with CMV. In this study, HIV(+) participants (n = 91) aged >45 years with <50 copies HIV RNA/ml plasma after >2 years on ART were assessed for cardiovascular risk (the D:A:D algorithm), type II diabetes (the HOMA-IR index), and neurocognitive performance. Blood samples were assayed for lipids, T cells, insulin, glucose, C-reactive protein, CX3CL1, sTNF-R1, total immunoglobulin G (IgG), and antibodies reactive with CMV lysate, glycoprotein B, or immediate-early-1. Levels of antibodies detected with the three antigens were tightly correlated. Levels of CMV lysate antibody were higher in patients than in age-matched healthy controls and reflected their nadir CD4 T-cell count (p = .001), total IgG (p = .02), and age (p = .08). Levels of CMV lysate antibody correlated with D:A:D score (p = .04), neurocognitive performance (p = .045), and fasting insulin (p = .02). In multivariable analyses, some associations reflected the effect of age, but CMV lysate antibody and CD8 T-cell counts were significant predictors of the HOMA-IR index (R(2) = 0.09, p = .01) independent of age. We conclude that associations between levels of CMV antibodies, cardiovascular risk, and neurocognitive health in HIV(+) patients stable on ART are moderated by age-associated increases in response to CMV, while CMV antibodies may be independently linked with IR.

Soluble CD14 in cerebrospinal fluid is associated with markers of inflammation and axonal damage in untreated HIV-infected patients: a retrospective cross-sectional study

Background

HIV-associated cognitive impairment has declined since the introduction of combination antiretroviral treatment (cART). However, milder forms of cognitive impairment persist. Inflammation in the cerebrospinal fluid (CSF) has been associated with cognitive impairment, and CSF neurofilament light chain protein (NFL) and CSF neopterin concentrations are increased in those patients. Microbial translocation in HIV infection has been suggested to contribute to chronic inflammation, and lipopolysaccharide (LPS) and soluble CD14 (sCD14) are markers of microbial translocation and the resulting monocyte activation, respectively. We hypothesised that microbial translocation contributes to inflammation and axonal damage in the central nervous system (CNS) in untreated HIV infection.

Methods

We analyzed paired samples of plasma and CSF from 62 HIV-infected, untreated patients without cognitive symptoms from Sahlgrenska University Hospital, Gothenburg, Sweden. Measurements of neopterin and NFL in CSF were available from previous studies. Plasma and CSF sCD14 was measured using ELISA (R&D, Minneapolis, MN), and plasma and CSF LPS was measured using LAL colorimetric assay (Lonza, Walkersville, MD, USA). Univariate and multivariate regression analyses were performed.

Results

LPS in plasma was associated with plasma sCD14 (r = 0.31, P = 0.015), and plasma sCD14 was associated with CSF sCD14 (r = 0.32, P = 0.012). Furthermore, CSF sCD14 was associated with NFL (r = 0.32, P = 0.031) and neopterin (r = 0.32, P = 0.012) in CSF. LPS was not detectable in CSF. In a multivariate regression model CSF sCD14 remained associated with NFL and neopterin after adjusting for age, CD4+ cell count, and HIV RNA in CSF.

Conclusions

In a group of untreated, HIV-infected patients LPS was associated with sCD14 in plasma, and plasma sCD14 was associated CSF sCD14. CSF sCD14 were associated with markers of CNS inflammation and axonal damage. This suggest that microbial translocation might be a driver of systemic and CNS inflammation. However, LPS was not detectable in the CSF, and since sCD14 is a marker of monocyte activation sCD14 may be increased due to other causes than microbial translocation. Further studies regarding cognitive impairment and biomarkers are warranted to fully understand causality.

HIV-associated neurocognitive disorder--pathogenesis and prospects for treatment

In the past two decades, several advancements have improved the care of HIV-infected individuals. Most importantly, the development and deployment of combination antiretroviral therapy (CART) has resulted in a dramatic decline in the rate of deaths from AIDS, so that people living with HIV today have nearly normal life expectancies if treated with CART. The term HIV-associated neurocognitive disorder (HAND) has been used to describe the spectrum of neurocognitive dysfunction associated with HIV infection. HIV can enter the CNS during early stages of infection, and persistent CNS HIV infection and inflammation probably contribute to the development of HAND. The brain can subsequently serve as a sanctuary for ongoing HIV replication, even when systemic viral suppression has been achieved. HAND can remain in patients treated with CART, and its effects on survival, quality of life and everyday functioning make it an important unresolved issue. In this Review, we describe the epidemiology of HAND, the evolving concepts of its neuropathogenesis, novel insights from animal models, and new approaches to treatment. We also discuss how inflammation is sustained in chronic HIV infection. Moreover, we suggest that adjunctive therapies--treatments targeting CNS inflammation and other metabolic processes, including glutamate homeostasis, lipid and energy metabolism--are needed to reverse or improve HAND-related neurological dysfunction.

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.

Response to peripheral immune stimulation within the brain: magnetic resonance imaging perspective of treatment success

Chronic peripheral inflammation in diseases such as rheumatoid arthritis leads to alterations in central pain processing and consequently to mood disorders resulting from sensitization within the central nervous system and enhanced vulnerability of the medial pain pathway. Proinflammatory cytokines such as tumor necrosis factor (TNF) alpha play an important role herein, and therapies targeting their signaling (i.e., anti-TNF therapies) have been proven to achieve good results. However, the phenomenon of rapid improvement in the patients’ subjective feeling after the start of TNFα neutralization remained confusing, because it was observed long before any detectable signs of inflammation decline. Functional magnetic resonance imaging (fMRI), enabling visualization of brain activity upon peripheral immune stimulation with anti-TNF, has helped to clarify this discrepancy. Moreover, fMRI appeared to work as a reliable tool for predicting prospective success of anti-TNF therapy, which is valuable considering the side effects of the drugs and the high therapy costs. This review, which is mainly guided by neuroimaging studies of the brain, summarizes the state-of-the-art knowledge about communication between the immune system and the brain and its impact on subjective well-being, addresses in more detail the outcome of the abovementioned anti-TNF fMRI studies (rapid response to TNFα blockade within the brain pain matrix and differences in brain activation patterns between prospective therapy responders and nonresponders), and discusses possible mechanisms for the latter phenomena and the predictive power of fMRI.

The role of chemokine C-C motif ligand 2 genotype and cerebrospinal fluid chemokine C-C motif ligand 2 in neurocognition among HIV-infected patients

OBJECTIVES

We examined interrelationships between chemokine C-C motif ligand 2 (CCL2) genotype and expression of inflammatory markers in the cerebrospinal fluid (CSF), plasma viral load, CD4 cell count and neurocognitive functioning among HIV-infected adults. We hypothesized that HIV-positive carriers of the 'risk' CCL2 -2578G allele, caused by a single nucleotide polymorphism (SNP) at rs1024611, would have a higher concentration of CCL2 in CSF, and that CSF CCL2 would be associated with both higher concentrations of other proinflammatory markers in CSF and worse neurocognitive functioning.

DESIGN

A cross-sectional study of 145 HIV-infected individuals enrolled in the National NeuroAIDS Tissue Consortium cohort for whom genotyping, CSF and neurocognitive data were available.

METHODS

Genomic DNA was extracted from peripheral blood mononuclear cells and/or frozen tissue specimens. CSF levels of CCL2, interleukin (IL)-2, IL-6, tumour necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), soluble tumor necrosis factor receptor 2, sIL-6Rα, sIL-2, sCD14 and B-cell activating factor were quantified. Neurocognitive functioning was measured using a comprehensive battery of neuropsychological tests.

RESULTS

Carriers of the CCL2 -2578G allele had a significantly higher concentration of CCL2 in CSF. CSF CCL2 level was positively and significantly associated with other CSF neuroinflammatory markers and worse cognitive functioning. There was a significant association between genotype and plasma viral load, such that carriers of the CCL2 -2578G allele with high viral load expressed greater levels of CCL2 and had higher neurocognitive deficit scores than other genotype/viral load groups.

CONCLUSION

Individuals with the CCL2 -2578G allele had higher levels of CCL2 in CSF, which was associated with increased pro-inflammatory markers in CSF and worse neurocognitive functioning. The results highlight the potential role of intermediate phenotypes in studies of genotype and cognition.

Central and peripheral markers of neurodegeneration and monocyte activation in HIV-associated neurocognitive disorders

HIV-associated neurocognitive disorders (HAND) affect up to 50 % of HIV-infected adults, independently predict HIV morbidity/mortality, and are associated with neuronal damage and monocyte activation. Cerebrospinal fluid (CSF) neurofilament subunits (NFL, pNFH) are sensitive surrogate markers of neuronal damage in several neurodegenerative diseases. In HIV, CSF NFL is elevated in individuals with and without cognitive impairment, suggesting early/persistent neuronal injury during HIV infection. Although individuals with severe cognitive impairment (HIV-associated dementia (HAD)) express higher CSF NFL levels than cognitively normal HIV-infected individuals, the relationships between severity of cognitive impairment, monocyte activation, neurofilament expression, and systemic infection are unclear. We performed a retrospective cross-sectional study of 48 HIV-infected adults with varying levels of cognitive impairment, not receiving antiretroviral therapy (ART), enrolled in the CNS Anti-Retroviral Therapy Effects Research (CHARTER) study. We quantified NFL, pNFH, and monocyte activation markers (sCD14/sCD163) in paired CSF/plasma samples. By examining subjects off ART, these correlations are not confounded by possible effects of ART on inflammation and neurodegeneration. We found that CSF NFL levels were elevated in individuals with HAD compared to cognitively normal or mildly impaired individuals with CD4+ T-lymphocyte nadirs ≤200. In addition, CSF NFL levels were significantly positively correlated to plasma HIV-1 RNA viral load and negatively correlated to plasma CD4+ T-lymphocyte count, suggesting a link between neuronal injury and systemic HIV infection. Finally, CSF NFL was significantly positively correlated with CSF pNFH, sCD163, and sCD14, demonstrating that monocyte activation within the CNS compartment is directly associated with neuronal injury at all stages of HAND.

Inflammatory co-morbidities in HIV+ individuals: learning lessons from healthy ageing

Increased life expectancy due to improved efficacy of cART has uncovered an increased risk of age-related morbidities in HIV+ individuals and catalyzed significant research into mechanisms driving these diseases. HIV infection increases the risk of non-communicable diseases common in the aged, including cardiovascular disease, neurocognitive decline, non-AIDS malignancies, osteoporosis, and frailty. These observations suggest that HIV accelerates immunological ageing, and there are many immunological similarities with the aged, including shortened telomeres, accumulation of senescent T cells and altered monocyte phenotype/function. However, the most critical similarity between HIV+ individuals and the elderly, which most likely underpins the heightened risk of non-communicable diseases, is chronic inflammation and associated immune activation. Here, we review the similarities between HIV+ individuals and the aged regarding the pathogenesis of inflammatory diseases, the current evidence for mechanisms driving these processes and discuss current and potential therapeutic strategies for addressing inflammatory co-morbidity in HIV+ infection.

Plasma cytokine levels are related to brain volumes in HIV-infected individuals

HIV-infected individuals frequently exhibit brain dysfunction despite antiretroviral treatment. The neuropathological mechanisms underlying these abnormalities remain unclear, pointing to the importance of identifying biomarkers sensitive to brain dysfunction. We examined 74 medically stable HIV-infected individuals using T1-weighted MRI. Volumes of the cortical grey matter (GM), white matter (WM), caudate, putamen, globus pallidus, thalamus, hippocampus, amygdala, and ventricles were derived using automated parcellation. A panel of plasma cytokines was measured using multiplexed bead array immunoassay. A model selection algorithm was used to select the combination of clinical and cytokine markers that best predicted each brain volumetric measure in a series of linear regression models. Higher CD4 nadir, shorter HIV infection duration, and antiretroviral treatment were significantly related to higher volumes of the putamen, thalamus, hippocampus, and WM. Older age was related to lower volumes in most brain regions and higher ventricular volume. Higher IFN-γ, MCP-1, and TNF-α were related to higher volumes of the putamen, pallidum, amygdala, GM, and WM. Higher IL-1β, IL-6, IL-16, IL-18, IP-10, MIP-1β, and SDF-1α were related to lower volumes of the putamen, pallidum, thalamus, hippocampus, amygdala, GM, and WM; and higher ventricular volume. The current findings provide evidence linking smaller brain volumes to HIV disease history, antiretroviral treatment, and advanced age. Cytokine markers, especially IL-6 and IL-16, showed robust association with brain volumes even after accounting for other clinical variables, demonstrating their utility in examining the mechanisms of HIV-associated brain abnormalities.

Heme oxygenase-1 deficiency accompanies neuropathogenesis of HIV-associated neurocognitive disorders

Heme oxygenase-1 (HO-1) is an inducible, detoxifying enzyme that is critical for limiting oxidative stress, inflammation, and cellular injury within the CNS and other tissues. Here, we demonstrate a deficiency of HO-1 expression in the brains of HIV-infected individuals. This HO-1 deficiency correlated with cognitive dysfunction, HIV replication in the CNS, and neuroimmune activation. In vitro analysis of HO-1 expression in HIV-infected macrophages, a primary CNS HIV reservoir along with microglia, demonstrated a decrease in HO-1 as HIV replication increased. HO-1 deficiency correlated with increased culture supernatant glutamate and neurotoxicity, suggesting a link among HIV infection, macrophage HO-1 deficiency, and neurodegeneration. HO-1 siRNA knockdown and HO enzymatic inhibition in HIV-infected macrophages increased supernatant glutamate and neurotoxicity. In contrast, increasing HO-1 expression through siRNA derepression or with nonselective pharmacologic inducers, including the CNS-penetrating drug dimethyl fumarate (DMF), decreased supernatant glutamate and neurotoxicity. Furthermore, IFN-γ, which is increased in CNS HIV infection, reduced HO-1 expression in cultured human astrocytes and macrophages. These findings indicate that HO-1 is a protective host factor against HIV-mediated neurodegeneration and suggest that HO-1 deficiency contributes to this degeneration. Furthermore, these results suggest that HO-1 induction in the CNS of HIV-infected patients on antiretroviral therapy could potentially protect against neurodegeneration and associated cognitive dysfunction.

Cerebrospinal fluid metabolomics reveals altered waste clearance and accelerated aging in HIV patients with neurocognitive impairment

Objective(s):

HIV-associated neurocognitive disorders (HAND) remain prevalent in HIV-infected patients on antiretroviral therapy (ART), but the underlying mechanisms are unclear. Some features of HAND resemble those of age-associated cognitive decline in the absence of HIV, suggesting that overlapping mechanisms may contribute to neurocognitive impairment.

Design:

Cross-sectional analysis of cerebrospinal fluid (CSF) from 100 individuals (46 HIV-positive patients and 54 HIV-negative controls).

Methods:

Untargeted CSF metabolite profiling was performed using liquid/gas chromatography followed by mass spectrometry. Cytokine profiling was performed by Bioplex. Bioinformatic analyses were performed in Metaboanalyst and R.

Results:

Alterations in the CSF metabolome of HIV patients on ART mapped to pathways associated with neurotransmitter production, mitochondrial function, oxidative stress, and metabolic waste. Many CSF metabolites altered in HIV overlapped with those altered with advanced age in HIV-negative controls, suggesting a pattern indicative of accelerated aging. Machine learning models identified neurotransmitters (glutamate, N-acetylaspartate), markers of glial activation (myo-inositol), and ketone bodies (beta-hydroxybutyric acid, 1,2-propanediol) as top-ranked classifiers of HAND. These CSF metabolites correlated with worse neurocognitive test scores, plasma inflammatory biomarkers [interferon (IFN)-α, IFN-γ, interleukin (IL)-8, IL-1β, IL-6, IL-2Ra], and intrathecal IFN responses (IFN-γ and kynurenine : tryptophan ratio), suggesting inter-relationships between systemic and intrathecal inflammation and metabolic alterations in CSF.

Conclusions:

Alterations in the CSF metabolome of HIV patients on ART suggest that persistent inflammation, glial responses, glutamate neurotoxicity, and altered brain waste disposal systems contribute to mechanisms involved in HAND that may be augmented with aging.

Neurologic disease in HIV-infected children and the impact of combination antiretroviral therapy

The prevalence of HIV-associated neurocognitive impairment in perinatally HIV-infected children has declined since the introduction of combination antiretroviral therapy (cART). Early initiation of cART in infancy has been shown to positively impact neurodevelopment; however, children continue to be diagnosed with HIV outside of the early infancy period and can experience subtle to severe neurocognitive deficits despite cART. The causes of these neurocognitive deficits despite effective cART are multifactorial and likely include continued viral replication in the CNS, ongoing neuroinflammation, irreversible CNS injury prior to cART initiation, neurotoxic effects of cART, and socioeconomic and psychosocial effects. Many aspects of our understanding of HIV-associated neurocognitive disorders have emerged from research in adult patients, but perinatally HIV-infected children represent a very different population. These children were exposed to HIV during a period of rapid brain development and have lifelong infection and potential lifelong cART exposure. HIV is no longer a rapidly fatal disease, and most HIV-infected children in resource-rich countries are living into adulthood. It is therefore critical to optimize neurocognitive outcomes of these youth. This review summarizes current understanding of the pathogenesis of HIV-associated CNS infection and the impact of cART on neurocognitive function in children and adolescents and discusses important areas for future research.

Extracellular vesicle protein levels are related to brain atrophy and cerebral white matter lesions in patients with manifest vascular disease: the SMART-MR study

OBJECTIVES

Extracellular vesicles (EVs) and their protein levels have been identified as a potential risk marker for the development of vascular disease. In the present study, we assessed whether levels of four previously identified EV proteins (cystatin C, serpin G1, serpin F2 and CD14) are associated with cerebral white matter lesions (WMLs) and brain atrophy.

DESIGN

Cohort study; cross-sectional and prospective.

SETTING

Single centre, secondary and tertiary setting.

PARTICIPANTS

1309 patients with manifest vascular disease from the Second Manifestations of ARTerial disease-MR (SMART-MR) study, of which 994 had successful brain MRI and EV protein level measurements.

OUTCOMES

WML and brain parenchymal fraction (BPF), as parameter for brain atrophy, at baseline and follow-up.

STATISTICAL METHODS

The relationship between EV protein levels and WML volume (expressed as log transformed percentage of intracranial volume) and BPF (expressed percentage of intracranial volume) on 1.5 T brain MRI was assessed with multivariable linear regression modelling. Subsequently, the relationship between baseline EV protein levels and progression of atrophy and WML was analysed in 534 patients, in whom a follow-up MRI was obtained after 4 years.

RESULTS

Higher EV-cystatin C and EV-CD14 were significantly associated with larger WML volume (linear regression coefficient (95% CI) 0.10 log %/SD (0.04 to 0.17) and 0.14 log %/SD (0.07 to 0.20), respectively. Higher EV-CD14 was associated with more brain atrophy (-0.14%/SD; -0.27 to -0.01). Baseline EV-CD14 was significantly associated with increase of WMLs (0.11 log %/SD (0.04 to 0.18)). No relationship with EV-serpins was observed at baseline or at follow-up.

CONCLUSIONS

EV proteins cystatin C and CD14 are related to cerebral WMLs and the progression of brain atrophy in patients with manifest vascular disease, potentially identifying EVs in the aetiology of structural brain changes.

A concise panel of biomarkers identifies neurocognitive functioning changes in HIV-infected individuals

Neurocognitive (NC) impairment (NCI) occurs commonly in people living with HIV. Despite substantial effort, no biomarkers have been sufficiently validated for diagnosis and prognosis of NCI in the clinic. The goal of this project was to identify diagnostic or prognostic biomarkers for NCI in a comprehensively characterized HIV cohort. Multidisciplinary case review selected 98 HIV-infected individuals and categorized them into four NC groups using normative data: stably normal (SN), stably impaired (SI), worsening (Wo), or improving (Im). All subjects underwent comprehensive NC testing, phlebotomy, and lumbar puncture at two timepoints separated by a median of 6.2 months. Eight biomarkers were measured in CSF and blood by immunoassay. Results were analyzed using mixed model linear regression and staged recursive partitioning. At the first visit, subjects were mostly middle-aged (median 45) white (58 %) men (84 %) who had AIDS (70 %). Of the 73 % who took antiretroviral therapy (ART), 54 % had HIV RNA levels below 50 c/mL in plasma. Mixed model linear regression identified that only MCP-1 in CSF was associated with neurocognitive change group. Recursive partitioning models aimed at diagnosis (i.e., correctly classifying neurocognitive status at the first visit) were complex and required most biomarkers to achieve misclassification limits. In contrast, prognostic models were more efficient. A combination of three biomarkers (sCD14, MCP-1, SDF-1α) correctly classified 82 % of Wo and SN subjects, including 88 % of SN subjects. A combination of two biomarkers (MCP-1, TNF-α) correctly classified 81 % of Im and SI subjects, including 100 % of SI subjects. This analysis of well-characterized individuals identified concise panels of biomarkers associated with NC change. Across all analyses, the two most frequently identified biomarkers were sCD14 and MCP-1, indicators of monocyte/macrophage activation. While the panels differed depending on the outcome and on the degree of misclassification, nearly all stable patients were correctly classified.

Applications and limitations of inflammatory biomarkers for studies on neurocognitive impairment in HIV infection

Despite reduced prevalence of severe forms of HIV-associated neurocognitive disorders (HAND) on current antiretroviral therapy (ART) regimens, milder forms of neurocognitive impairment (NCI) remain prevalent in HIV-infected populations. These mild forms of HAND consist of subtypes, probably reflecting distinct, though possibly overlapping, pathophysiological mechanisms. Factors associated with HAND in HIV patients with prolonged viral suppression on ART include older age, low nadir CD4, active HCV co-infection, and cardiovascular risk factors, but underlying mechanisms and their relationship to innate immune activation, chronic inflammation, and other features of systemic disease are poorly understood. In this article, we discuss applications and limitations of plasma inflammatory biomarkers for studies on HAND in HIV patients on ART and describe an analysis pipeline to reduce common sources of noise and increase likelihood of identifying relevant inflammatory biomarkers. Clinical covariates and comorbidities that influence inflammatory biomarkers, such as aging, obesity, metabolic abnormalities, HCV co-infection, and substance abuse, are also reviewed. As an example for using this analytic pipeline, we present an exploratory study of 22 plasma inflammatory biomarkers (IFN-α 2b and -γ, 16 cytokines/chemokines, sIL-2R, sCD14, HA, and YKL-40) in a cohort of HIV-infected individuals with advanced disease, frequent HCV co-infection, and viral suppression on ART. The identification of inflammatory biomarkers associated with HAND in HIV+ patients on ART may be useful to distinguish between HAND subtypes with distinct pathophysiology, and is important for achieving a systems-level understanding of the biology of these disorders, developing effective therapies, and evaluating therapeutic outcomes.

HIV DNA reservoir increases risk for cognitive disorders in cART-naïve patients

Objectives

Cognitive impairment remains frequent in HIV, despite combination antiretroviral therapy (cART). Leading theories implicate peripheral monocyte HIV DNA reservoirs as a mechanism for spread of the virus to the brain. These reservoirs remain present despite cART. The objective of this study was to determine if the level of HIV DNA in CD14⁺ enriched monocytes predicted cognitive impairment and brain injury.

Methods

We enrolled 61 cART-naïve HIV-infected Thais in a prospective study and measured HIV DNA in CD14⁺ enriched monocyte samples in a blinded fashion. We determined HAND diagnoses by consensus panel and all participants underwent magnetic resonance spectroscopy (MRS) to measure markers of brain injury. Immune activation was measured via cytokines in cerebrospinal fluid (CSF).

Results

The mean (SD) age was 35 (6.9) years, CD4 T-lymphocyte count was 236 (139) and log₁₀ plasma HIV RNA was 4.8 (0.73). Twenty-eight of 61 met HAND criteria. The log₁₀ CD14⁺ HIV DNA was associated with HAND in unadjusted and adjusted models (p = 0.001). There was a 14.5 increased odds ratio for HAND per 1 log-value of HIV DNA (10-fold increase in copy number). Plasma CD14⁺ HIV DNA was associated with plasma and CSF neopterin (p = 0.023) and with MRS markers of neuronal injury (lower N-acetyl aspartate) and glial dysfunction (higher myoinositol) in multiple brain regions.

Interpretation

Reservoir burden of HIV DNA in monocyte-enriched (CD14⁺) peripheral blood cells increases risk for HAND in treatment-naïve HIV+ subjects and is directly associated with CSF immune activation and both brain injury and glial dysfunction by MRS.

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.

HIV Associated Neurocognitive Disorders

Human immunodeficiency virus type 1 is associated with the development of neurocognitive disorders in many infected individuals, including a broad spectrum of motor impairments and cognitive deficits. Despite extensive research, the pathogenesis of HIV-associated neurocognitive disorders (HAND) is still not clear. This review provides a comprehensive view of HAND, including HIV neuroinvasion, HAND diagnosis and different level of disturbances, influence of highly-active antiretroviral therapy to HIV-associated dementia (HAD), possible pathogenesis of HAD, etc. Together, this review will give a thorough and clear understanding of HAND, especially HAD, which will be vital for future research, diagnosis and treatment.

Elevated sCD163 in plasma but not cerebrospinal fluid is a marker of neurocognitive impairment in HIV infection

OBJECTIVE

Here we evaluated whether neurocognitive disorders in HIV-infected individuals on effective antiretroviral therapy (ART) are associated with persistent monocyte activation as indexed by levels of soluble CD163 (sCD163), shed by monocyte/macrophages.

DESIGN

Chronically, HIV-infected individuals were examined at two consecutive visits median [interquartile range (IQR)] 16 (7-32) months apart. All patients were on ART and durably virologically suppressed (plasma HIV RNA <50 copies/ml) at all visits. Thirty-four age-matched HIV-seronegative patients were used as controls.

METHODS

A global deficit score (GDS) was calculated based on comprehensive neuropsychological assessment according to standard methods. Neuropsychological and medical data were used to assign neurocognitive status according to published guidelines for HIV-associated neurocognitive disorders (HAND) as follows: neuropsychologically normal (NP-nml), asymptomatic neuropsychological impairment (ANI) and minor neurocognitive disorder (MND). sCD163 in plasma and cerebrospinal fluid was measured using ELISA.

RESULTS

GDS-impaired patients had higher plasma sCD163 than those who were not impaired [median (IQR) 1401 ng/ml (1057-2258) versus 955 ng/ml (586-1313); Wilcoxon P=0.028]. Patients with MND (N=6) had significantly higher plasma sCD163 than ANI (P=0.04) or NP-nml (P=0.02). Whereas plasma sCD163 levels dropped in patients who were stably GDS-unimpaired after the first visit (P<0.032), levels remained elevated in those who remained GDS-impaired (P=0.50).

INTERPRETATION

These findings are consistent with persistent monocyte/macrophage activation in neurophysiologically impaired HIV-infected individuals despite virally suppressive ART. Overall, these observations underscore the significance of monocyte/macrophage immune responses in HIV, persistent monocyte activation in HAND and the value of sCD163, as a plasma marker of neurocognitive impairment.

Pivotal role of M-DC8+ monocytes from viremic HIV-infected patients in TNFα overproduction in response to microbial products

HIV infects activated CD4+ T cells and induces their depletion. Progressive HIV infection leading to AIDS is fueled by chronic immune hyperactivation, mediated by inflammatory cytokines like TNFα. This has been related to intestinal epithelial damage and microbial LPS translocation into the circulation. Using 11-color flow cytometry, cell sorting, and cell culture, we investigated the numbers and TNFα production of fully defined circulating dendritic cell and monocyte populations during HIV-1 infection. In 15 viremic, untreated patients, compared with 8 treated, virologically suppressed patients or to 13 healthy blood donors, circulating CD141 (BDCA-3)+ and CD1c (BDCA-1)+ dendritic cell counts were reduced. Conversely, CD14+CD16++ monocyte counts were increased, particularly those expressing M-DC8, while classical CD14++CD16−M-DC8− monocyte numbers were unchanged. Blood mononuclear cells from viremic patients produced more TNFα in response to LPS than those from virologically suppressed patients. M-DC8+ monocytes were mostly responsible for this overproduction. Moreover, M-DC8+ monocytes differentiated in vitro from classical monocytes using M-CSF and GM-CSF, which is increased in viremic patient's plasma. This M-DC8+ monocyte population, which is involved in the pathogenesis of chronic inflammatory diseases like Crohn disease, might thus be considered as a major actor in the immune hyperactivation fueling HIV infection progression.

Monocyte activation markers in cerebrospinal fluid associated with impaired neurocognitive testing in advanced HIV infection

BACKGROUND

Activated monocytes/macrophages play a role in severe forms of HIV-associated neurocognitive disorders (HAND), but little is known about the mechanisms driving milder forms that are prevalent despite combination antiretroviral therapy (cART). To examine relationships of monocyte activation markers to HAND of varying severity, we compared plasma and cerebrospinal fluid (CSF) biomarker levels with neurocognitive test scores in HIV+ subjects.

METHODS

Plasma and CSF soluble CD14 (sCD14), CCL2, and interleukin (IL) 6 were measured by enzyme-linked immunosorbent assay in 67 HIV+ subjects with nadir CD4 <300, and CSF inflammatory biomarkers were measured by multiplex assay in 14 subjects on suppressive cART.

RESULTS

Eighty-two percent were on cART, with 31% having undetectable plasma viral load (VL). CSF sCD14 was increased in subjects with impaired neurocognitive testing (P = 0.02), correlated inversely with global T scores in subjects with detectable but not undetectable plasma VL (P = 0.02), and yielded higher area under the receiver operating characteristic curve values for predicting impaired T scores (0.659) than plasma or CSF VL and current or nadir CD4 counts in single-marker and multivariate models. CSF sCD14, IL-6, IL-8, CCL2, CCL3, CXCL10, and interferon (IFN) gamma were increased in subjects on suppressive cART regardless of cognitive status and predicted patient class in unsupervised analyses, with IL-8, CCL2, and IFNγ explaining most of the variance.

CONCLUSIONS

CSF sCD14 is associated with impaired neurocognitive testing in patients with HIV on nonsuppressive cART, suggesting potential utility as a biomarker to monitor HAND progression. CSF sCD14, IL-6, IL-8, CCL2, CCL3, CXCL10, and IFNγ remain elevated in patients on suppressive cART regardless of cognitive status, implying ongoing intrathecal inflammation even in the absence of clinical manifestations.

Microbial translocation in HIV infection: causes, consequences and treatment opportunities

Systemic immune activation is increased in HIV-infected individuals, even in the setting of virus suppression with antiretroviral therapy. Although numerous factors may contribute, microbial products have recently emerged as potential drivers of this immune activation. In this Review, we describe the intestinal damage that occurs in HIV infection, the evidence for translocation of microbial products into the systemic circulation and the pathways by which these products activate the immune system. We also discuss novel therapies that disrupt the translocation of microbial products and the downstream effects of microbial translocation.

The HIV-1 protease inhibitor nelfinavir activates PP2 and inhibits MAPK signaling in macrophages: a pathway to reduce inflammation

The HIV-1 PI NFV has off-target effects upon host enzymes, including inhibition of the 20S proteasome, resulting in activation of PP1. HIV-1-associated monocyte/macrophage activation, in part a result of systemically elevated levels of microbial products including LPS, is associated with risk of mortality, independent of viremia or CD4 T cell loss. This study tested the hypothesis that activation of protein phosphatases by NFV would reduce activation of monocytes/macrophages through dephosphorylation of signal transduction proteins. NFV uniquely blocked LPS-induced production by human monocyte-derived macrophages of the inflammatory cytokines TNF and IL-6, as well as sCD14. Although NFV failed to modulate NF-κB, NFV treatment reduced phosphorylation of AKT and MAPKs. Inhibition of PP2 with okadaic acid blocked the anti-inflammatory effect of NFV, whereas the PP1 inhibitor calyculin A failed to counter the anti-inflammatory effects of NFV. For in vivo studies, plasma sCD14 and LPS were monitored in a cohort of 31 pediatric HIV-1 patients for over 2 years of therapy. Therapy, including NFV, reduced sCD14 levels significantly compared with IDV or RTV, independent of ΔLPS levels, VL, CD4 T cell frequency, or age. The hypothesis was supported as NFV induced activation of PP2 in macrophages, resulting in disruption of inflammatory cell signaling pathways. In vivo evidence supports that NFV may offer beneficial effects independent of antiviral activity by reducing severity of chronic innate immune activation in HIV-1 infection.

HIV patients treated with low-dose prednisolone exhibit lower immune activation than untreated patients

Background

HIV-associated general immune activation is a strong predictor for HIV disease progression, suggesting that chronic immune activation may drive HIV pathogenesis. Consequently, immunomodulating agents may decelerate HIV disease progression.

Methods

In an observational study, we determined immune activation in HIV patients receiving low-dose (5 mg/day) prednisolone with or without highly-active antiretroviral therapy (HAART) compared to patients without prednisolone treatment. Lymphocyte activation was determined by flow cytometry detecting expression of CD38 on CD8(+) T cells. The monocyte activation markers sCD14 and LPS binding protein (LBP) as well as inflammation markers soluble urokinase plasminogen activated receptor (suPAR) and sCD40L were determined from plasma by ELISA.

Results

CD38-expression on CD8+ T lymphocytes was significantly lower in prednisolone-treated patients compared to untreated patients (median 55.40% [percentile range 48.76-67.70] versus 73.34% [65.21-78.92], p = 0.0011, Mann-Whitney test). Similarly, we detected lower levels of sCD14 (3.6 μg/ml [2.78-5.12] vs. 6.11 μg/ml [4.58-7.70]; p = 0.0048), LBP (2.18 ng/ml [1.59-2.87] vs. 3.45 ng/ml [1.84-5.03]; p = 0.0386), suPAR antigen (2.17 μg/ml [1.65-2.81] vs. 2.56 μg/ml [2.24-4.26]; p = 0.0351) and a trend towards lower levels of sCD40L (2.70 pg/ml [1.90-4.00] vs. 3.60 pg/ml [2.95-5.30]; p = 0.0782). Viral load in both groups was similar (0.8 × 10⁵ ng/ml [0.2-42.4 × 10⁵] vs. 1.1 × 10⁵ [0.5-12.2 × 10⁵]; p = 0.3806). No effects attributable to prednisolone were observed when patients receiving HAART in combination with prednisolone were compared to patients who received HAART alone.

Conclusions

Patients treated with low-dose prednisolone display significantly lower general immune activation than untreated patients. Further longitudinal studies are required to assess whether treatment with low-dose prednisolone translates into differences in HIV disease progression.

Plasma sCD14 is a biomarker associated with impaired neurocognitive test performance in attention and learning domains in HIV infection

OBJECTIVE

Mild forms of HIV-associated neurocognitive disorders (HAND) remain prevalent in the era of combination antiretroviral therapy (cART). Although elevated lipopolysaccharide (LPS) and immune activation are implicated in HAND pathogenesis, relationships of LPS and inflammatory markers to mild forms of HAND or impairment in specific cognitive domains are unknown. To examine these relationships, we compared plasma soluble CD14 (sCD14), CCL2, and LPS levels with neurocognitive test scores in a cART era cohort.

METHODS

We analyzed plasma from HIV+ subjects (n = 97) with nadir CD4 counts <300 and high frequency of hepatitis C virus coinfection and illicit drug use for relationships between sCD14, CCL2, and LPS levels and neurocognitive test scores.

RESULTS

Plasma sCD14 levels were higher in subjects with test scores indicating global impairment (P = 0.007), particularly in attention and learning domains (P = 0.015 and P = 0.03, respectively), regardless of HAND diagnosis. Plasma sCD14 levels correlated inversely with global, attention, and learning T scores (P = 0.036, 0.047, and 0.007, respectively) and yielded higher area under receiver operating characteristic values for predicting impaired scores than single-marker models based on plasma or cerebrospinal fluid viral load or CD4 count (area under receiver operating characteristic values = 0.71, 0.81, and 0.71, respectively) and in 4-marker models based on plasma sCD14 and 3 conventional markers compared with the 3-marker models.

CONCLUSIONS

Plasma sCD14 is a biomarker associated with impaired neurocognitive testing in attention and learning domains in HIV-infected individuals with advanced disease, suggesting involvement of cortical and limbic pathways by inflammatory processes in the cART era. Plasma sCD14 is a potential biomarker to monitor HAND progression and therapeutic responses.

Minocycline treatment for HIV-associated cognitive impairment: results from a randomized trial

OBJECTIVE

We conducted a study of minocycline to assess its safety, tolerability, and efficacy for the treatment of HIV-associated cognitive impairment.

METHODS

HIV-1-infected individuals with progressive neurocognitive decline were enrolled in a double-blind, placebo-controlled study of minocycline. Participants were randomized to receive minocycline 100 mg or matching placebo orally every 12 hours. The primary efficacy measure was change in a neuropsychological test composite z score (NPZ-8) from baseline to week 24. Measures of safety included the frequency of adverse events and changes over time in laboratory tests. After 50% of participants completed the double-blind phase, an interim analysis of futility for the primary outcome measure was performed, and our Data and Safety Monitoring Board recommended early study termination.

RESULTS

A total of 107 HIV-1-infected individuals with cognitive impairment were enrolled. The minocycline group did not show improvement in the primary outcome measure (NPZ-8) (mean 24-week change = 0.12) compared to placebo (mean 24-week change = 0.17) (95% confidence interval = [-0.26, 0.39], p = 0.70). There were few severe adverse events or laboratory abnormalities in either treatment group.

CONCLUSION

Minocycline was safe and well-tolerated in individuals with HIV-associated cognitive impairment, but cognitive improvement was not observed. Classification of evidence. This interventional study provides Class II evidence for the safety, tolerability, and efficacy of minocycline for the treatment of HIV-associated cognitive impairment.

Identification of three immunologic correlates for HIV type 1 pathogenesis in youth

To evaluate the stability and heterogeneity of cytokine and chemokine profiles in 80 youth with and without HIV-1 infection, we tested plasma samples at repeated visits without antiretroviral therapy. Among nine analytes that were quantified using multiplexing assays, interleukin 10 (IL-10), IL-18, and soluble CD30 persistently showed a positive correlation with HIV-1 viral load (Spearman ρ = 0.40-0.59, p < 0.01 for all). A negative correlation with CD4(+) T cell counts (ρ = -0.40 to -0.60, p < 0.01 for all) was also persistent for the three analytes. Analyses restricted to 48 AIDS-free youth (96 visits) yielded similar findings, as did multivariable models in which race, sex, age, body mass index, and time interval between visits were treated as covariates. These relationships reflected two novel features observed for all three analytes. First, their presence in plasma was relatively stable between visits (ρ = 0.50-0.90, p < 0.03), regardless of HIV-1 infection status. Second, pairwise correlation was strong and persistent in HIV-1-seropositive youth (ρ = 0.40-0.59, p < 0.01), but not in HIV-1, seronegatives (p > 0.13). Additional analytes, especially eotaxin/CCL11 and SDF-1β/CXCL12, had no correlation with HIV-1-related outcomes despite their stability between visits. Overall, circulating IL-10, IL-18, and soluble CD30 could partially track unfavorable responses to HIV-1 infection in youth. These markers of persistent immune activation are individually and collectively indicative of HIV-1 pathogenesis.

Peripheral biomarkers do not correlate with cognitive impairment in highly active antiretroviral therapy-treated subjects with human immunodeficiency virus type 1 infection

Neuropsychological (NP) impairments in human immunodeficiency virus (HIV)-infected individuals remain high despite the introduction of highly active antiretroviral therapy (HAART). We sought to determine whether or not a monocyte gene expression profile along with other peripheral factors would correlate with neuropsychological impairment among HIV-infected individuals. Forty-four HIV-1-seropositive subjects (HIV+) on HAART and 11 HIV-1-seronegative controls (HIV-) had NP testing and blood drawn for monocyte gene expression analysis. All HIV+ subjects were assessed for CD4 counts, apolipoprotein E (ApoE) genotype, viral load, and plasma lipopolysaccharide (LPS) and soluble CD14 (sCD14). NP scores were normalized to age, gender, and education. Twenty-five percent of HIV+ individuals showed abnormal NP testing results (> 1.5 SD below normal in two domains). HIV+ individuals had deficits in attention/working memory, verbal learning, and information processing speed compared to HIV- controls. There was no correlation between overall NP impairment and plasma viral load, level of education, age, ethnic diversity, sCD14, plasma LPS, CD4 cell count, ApoE genotype, or years of infection. However, greater years of infection had worse visual learning performance. sCD14 and CD4 nadir positively correlated with information processing speed and fine motor skills, respectively. LPS correlated with viral load but not cognitive impairment. Monocyte gene expression confirmed a chronic inflammatory profile that correlated with viral load but not cognition. No blood index or profile was associated with overall NP impairment.

HIV-associated neurocognitive disorder: pathogenesis and therapeutic opportunities

Human immunodeficiency virus type 1 (HIV) infection presently affects more that 40 million people worldwide, and is associated with central nervous system (CNS) disruption in at least 30% of infected individuals. The use of highly active antiretroviral therapy has lessened the incidence, but not the prevalence of mild impairment of higher cognitive and cortical functions (HIV-associated neurocognitive disorders) as well as substantially reduced a more severe form dementia (HIV-associated dementia). Furthermore, improving neurological outcomes will require novel, adjunctive therapies that are targeted towards mechanisms of HIV-induced neurodegeneration. Identifying such molecular and pharmacological targets requires an understanding of the events preceding irreversible neuronal damage in the CNS, such as actions of neurotoxins (HIV proteins and cellular factors), disruption of ion channel properties, synaptic damage, and loss of adult neurogenesis. By considering the specific mechanisms and consequences of HIV neuropathogenesis, unified approaches for neuroprotection will likely emerge using a tailored, combined, and non-invasive approach.