Dynamics of monocyte chemoattractant protein type one (MCP-1) and HIV viral load in human cerebrospinal fluid and plasma

Distinct Effects of Selective Serotonin Reuptake Inhibitors and Serotonin-Norepinephrine Reuptake Inhibitors on Soluble Biomarkers in Blood and Cerebrospinal Fluid of People With HIV

BACKGROUND

Persistent inflammation affects people with HIV (PWH) despite antiretroviral therapy (ART). Selective serotonin and serotonin-norepinephrine reuptake inhibitors (SSRIs, SNRIs), HMG-CoA reductase-inhibitors (statins), and angiotensin-converting enzyme inhibitors (ACEIs) have immunomodulant properties. We evaluated the potential impact of these drugs on inflammation and neurodegeneration in PWH.

METHODS

Cross-sectional single-center (United States) analysis in 184 PWH on ART with plasma HIV RNA < 200 copies/mL. All participants had 10 biomarkers measured in blood and cerebrospinal fluid (CSF). To reduce dimensionality, hierarchical clustering and principal components (PCs) analysis were employed. The analyses were adjusted for duration of the drugs and clinical conditions.

RESULTS

Participants were mostly middle-aged men, with median CD4+ T cells of 620/µL. In adjusted models, SSRI use was associated with 3 PCs: higher CSF and plasma Aβ42 and CSF CCL2 (aβ=.14, P = .040); lower CSF 8-oxo-dG, total tau, and sCD14 (aβ=-.12, P = .042); and higher plasma sCD14 with lower sCD40L (aβ=.15, P = .042). SNRI use was associated with higher values of CSF and plasma neopterin and CSF sTNFR-II (aβ=.22, P = .004). Statins and ACEIs showed no association.

CONCLUSIONS

SSRIs and SNRIs had distinct biomarker signatures. SSRIs were associated with reduced neurodegeneration, immune activation, and oxidative stress in CSF, suggesting a role of SSRIs as adjunctive therapy in PWH.

CD3+CD56+ and CD3-CD56+ lymphocytes in the cerebrospinal fluid of persons with HIV-1 subtypes B and C

The transactivator of transcription (Tat) is a HIV regulatory protein which promotes viral replication and chemotaxis. HIV-1 shows extensive genetic diversity, HIV-1 subtype C being the most dominant subtype in the world. Our hypothesis is the frequency of CSF CD3+CD56+ and CD3-CD56dim is reduced in HIV-1C compared to HIV-1B due to the Tat C30S31 substitution in HIV-1C. 34 CSF and paired blood samples (PWH, n = 20; PWoH, n = 14) were studied. In PWH, the percentage of CD3+CD56+ was higher in CSF than in blood (p < 0.001), comparable in both compartments in PWoH (p = 0.20). The proportion of CD3-CD56dim in CSF in PWH was higher than PWoH (p = 0.008). There was no subtype differences. These results showed CNS compartmentalization of NKT cell response in PWH.

Rebound HIV-1 in cerebrospinal fluid after antiviral therapy interruption is mainly clonally amplified R5 T cell-tropic virus

HIV-1 persists as a latent reservoir in people receiving suppressive antiretroviral therapy (ART). When ART is interrupted (treatment interruption/TI), rebound virus re-initiates systemic infection in the lymphoid system. During TI, HIV-1 is also detected in cerebrospinal fluid (CSF), although the source of this rebound virus is unknown. To investigate whether there is a distinct HIV-1 reservoir in the central nervous system (CNS), we compared rebound virus after TI in the blood and CSF of 11 participants. Peak rebound CSF viral loads vary and we show that high viral loads and the appearance of clonally amplified viral lineages in the CSF are correlated with the transient influx of white blood cells. We found no evidence of rebound macrophage-tropic virus in the CSF, even in one individual who had macrophage-tropic HIV-1 in the CSF pre-therapy. We propose a model in which R5 T cell-tropic virus is released from infected T cells that enter the CNS from the blood (or are resident in the CNS during therapy), with clonal amplification of infected T cells and virus replication occurring in the CNS during TI.

Central Nervous System Safety During Brief Analytic Treatment Interruption of Antiretroviral Therapy Within 4 Human Immunodeficiency Virus Remission Trials: An Observational Study in Acutely Treated People Living With Human Immunodeficiency Virus

BACKGROUND

The central nervous system (CNS) is a likely reservoir of human immunodeficiency virus (HIV), vulnerable to viral rebound, inflammation, and clinical changes upon stopping antiretroviral therapy (ART). It is critical to evaluate the CNS safety of studies using analytic treatment interruption (ATI) to assess HIV remission.

METHODS

Thirty participants who started ART during acute HIV infection underwent CNS assessments across 4 ATI remission trials. ART resumption occurred with plasma viral load >1000 copies/mL. CNS measures included paired pre- vs post-ATI measures of mood, cognitive performance, and neurologic examination, with elective cerebrospinal fluid (CSF) sampling, brain diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS).

RESULTS

Median participant age was 30 years old and 29/30 were male. Participants' median time on ART before ATI was 3 years, and ATI lasted a median of 35 days. Post-ATI, there were no differences in median mood scores or neurologic findings and cognitive performance improved modestly. During ATI, a low level of CSF HIV-1 RNA was detectable in 6 of 20 participants with plasma viremia, with no group changes in CSF immune activation markers or brain DTI measures. Mild worsening was identified in post-ATI basal ganglia total choline MRS, suggesting an alteration in neuronal membranes.

CONCLUSION

No adverse CNS effects were observed with brief, closely monitored ATI in participants with acutely treated HIV, except an MRS alteration in basal ganglia choline. Further studies are needed to assess CNS ATI safety in HIV remission trials, particularly for studies using higher thresholds to restart ART and longer ATI durations.

Daily Cannabis Use is Associated With Lower CNS Inflammation in People With HIV

OBJECTIVE

Recent cannabis exposure has been associated with lower rates of neurocognitive impairment in people with HIV (PWH). Cannabis's anti-inflammatory properties may underlie this relationship by reducing chronic neuroinflammation in PWH. This study examined relations between cannabis use and inflammatory biomarkers in cerebrospinal fluid (CSF) and plasma, and cognitive correlates of these biomarkers within a community-based sample of PWH.

METHODS

263 individuals were categorized into four groups: HIV- non-cannabis users (n = 65), HIV+ non-cannabis users (n = 105), HIV+ moderate cannabis users (n = 62), and HIV+ daily cannabis users (n = 31). Differences in pro-inflammatory biomarkers (IL-6, MCP-1/CCL2, IP-10/CXCL10, sCD14, sTNFR-II, TNF-α) by study group were determined by Kruskal-Wallis tests. Multivariable linear regressions examined relationships between biomarkers and seven cognitive domains, adjusting for age, sex/gender, race, education, and current CD4 count.

RESULTS

HIV+ daily cannabis users showed lower MCP-1 and IP-10 levels in CSF compared to HIV+ non-cannabis users (p = .015; p = .039) and were similar to HIV- non-cannabis users. Plasma biomarkers showed no differences by cannabis use. Among PWH, lower CSF MCP-1 and lower CSF IP-10 were associated with better learning performance (all ps < .05).

CONCLUSIONS

Current daily cannabis use was associated with lower levels of pro-inflammatory chemokines implicated in HIV pathogenesis and these chemokines were linked to the cognitive domain of learning which is commonly impaired in PWH. Cannabinoid-related reductions of MCP-1 and IP-10, if confirmed, suggest a role for medicinal cannabis in the mitigation of persistent inflammation and cognitive impacts of HIV.

Immuno-inflammatory changes across phases of early psychosis: The impact of antipsychotic medication and stage of illness

INTRODUCTION

Research examining the role of inflammation in psychosis has produced inconsistent results. Variables that influence inflammation, including antipsychotic medication, are inconsistently controlled across studies and variation of inflammatory analytes across stages of psychosis may also influence findings. The purpose of this study was to assess for evidence of immuno-inflammatory dysregulation across the stages of early psychosis. We examined a immuno-inflammatory analytes in subjects at clinical high risk (CHR) for developing a psychotic disorder, antipsychotic-naïve (-n) and antipsychotic treated (-a) subjects in their first episode of psychosis (FEP), and healthy control (HC) subjects.

METHODS

A total of 11 subjects at CHR, 50 subjects within their FEP (40 FEP-n, 10 FEP-a), and 10 HC subjects were recruited from early psychosis programs in San Diego and Mexico City. Plasma was collected for biomarker assay.

RESULTS

Immuno-inflammatory analytes significantly differed between groups: Interferon-gamma (IFN-γ), Interleukin-10 (IL-10), Eotaxin-1, Interferon Gamma-Induced Protein-10 (IP-10), Monocyte Chemotactic Protein-1 (MCP-1), Macrophage-Derived Chemokine (MDC), Macrophage Inflammatory Protein-1 beta (MIP-1β), Thymus and Activation Regulated Chemokine (TARC), and Brain Derived Neurotropic Factor (BDNF). Post-hoc analyses revealed an overall pattern of higher levels of IL-10, MCP-1, MIP-1β, TARC, and BDNF in CHR as compared to FEP-a, FEP-n, and HC subjects.

CONCLUSIONS

Results reveal a profile of immuno-inflammatory dysregulation in early stages of psychosis prior to psychotic conversion and treatment with antipsychotic medication. The CHR phase of early psychosis may represent a period of increased immuno-inflammatory activation, but due to limited sample size, these results deserve replication in a well characterized early psychosis population.

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.

Recall Responses from Brain-Resident Memory CD8+ T Cells (bTRM) Induce Reactive Gliosis

HIV-associated neurocognitive disorders (HAND) persist even during effective combination antiretroviral therapy (cART). Although the cause of HAND is unknown, studies link chronic immune activation, neuroinflammation, and cerebrospinal fluid viral escape to disease progression. In this study, we tested the hypothesis that specific, recall immune responses from brain-resident memory T cells (bT_RM) could activate glia and induce neurotoxic mediators. To address this question, we developed a heterologous prime-central nervous system (CNS) boost strategy in mice. We observed that the murine brain became populated with long-lived CD8⁺ bT_RM, some being specific for an immunodominant Gag epitope. Recall stimulation using HIV-1 AI9 peptide administered in vivo resulted in microglia displaying elevated levels of major histocompatibility complex class II and programmed death-ligand 1, and demonstrating tissue-wide reactive gliosis. Immunostaining further confirmed this glial activation. Taken together, these results indicate that specific, adaptive recall responses from bT_RM can induce reactive gliosis and production of neurotoxic mediators.

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Heterologous prime-CNS boost induced HIV-1-specific bT_RM, which persisted long term

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Recall responses from HIV-specific bT_RM induced tissue-wide reactive gliosis

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bT_RM induced-reactive gliosis likely has cumulative neurotoxic consequences

Brief Report: CD14+ Enriched Peripheral Cells Secrete Cytokines Unique to HIV-Associated Neurocognitive Disorders

Monocytes play a vital role in HIV-associated neurocognitive disorder (HAND), postulated to transport HIV into the brain and secrete pro-inflammatory cytokines. We analyzed cytokines released by cultured peripheral blood mononuclear cells enriched with the CD14 marker isolated from HIV-infected individuals with HAND and normal cognition (NC) in combination antiretroviral therapy naive and after 1 year on treatment. Interleukin-8 and monocyte chemoattractant protein-1 levels were higher in HAND compared with NC at baseline (P = 0.002 and P < 0.0001). These cytokines remained higher in HAND patients 1 year after combination antiretroviral therapy and were significant when NC patients who were initially HAND were excluded (P = 0.012 and P = 0.002). Both correlated with baseline CD14 peripheral blood mononuclear cell HIV DNA levels supporting the role of HIV DNA reservoir size and monocyte cytokines in HAND persistence.

Plasma soluble CD163 is associated with postmortem brain pathology in human immunodeficiency virus infection

OBJECTIVE

Higher plasma soluble cluster of differentiation (CD)163 (sCD163), shed by monocytes and macrophages, correlates with neurocognitive impairment in HIV infection. We hypothesized that higher antemortem plasma or cerebrospinal fluid (CSF) sCD163 would be associated with greater postmortem neurodegeneration and/or microgliosis.

DESIGN

Retrospective, postmortem observational study.

METHODS

We measured sCD163 levels in antemortem plasma (n = 54) and CSF (n = 32) samples from 74 HIV-seropositive participants (median 5 months before death) who donated their brains to research at autopsy. Postmortem, we quantified markers of synaptodendritic damage (microtubule-associated protein 2, synaptophysin), microgliosis [human leukocyte antigen DR (HLA-DR), ionized calcium-binding adaptor molecule 1], astrocytosis (glial fibrillary acidic protein), and impaired protein clearance (β-amyloid) in frontal cortex, hippocampus, putamen, and internal capsule. Multivariable least-squares regression was used to evaluate the association between plasma or CSF sCD163 and histological measures, correcting for multiple comparisons.

RESULTS

Higher plasma sCD163 was associated with lower microtubule-associated protein 2 in frontal cortex [B = -0.23, 95% confidence interval (CI) -0.41 to -0.06, P = 0.04], putamen (B = 0.32, 95% CI -0.52 to -0.12, P = 0.02), and hippocampus (B = -0.23, 95% CI -0.35 to -0.10, P = 0.01), and with lower synaptophysin in hippocampus (B = -0.25, 95% CI -0.42 to -0.03, P = 0.02) but not putamen or frontal cortex (P > 0.05). Higher plasma sCD163 was associated with higher HLA-DR in putamen (B = 0.17, 95% CI 0.08 to 0.26, P = 0.008). CSF sCD163 was not associated with any histological measure (P > 0.05).

CONCLUSION

Higher plasma sCD163 in life is associated with greater synaptodendritic damage and microglial activation in cortical and subcortical brain regions.

Chemokine and Chemokine Receptor Polymorphisms in Bipolar Disorder

OBJECTIVE

Bipolar disorder (BD) is a debilitating psychiatric disease with unknown etiology. Recent studies have shown inflammation as a potential contributing factor of BD pathogenesis. However, potential associations between chemokine and chemokine receptor polymorphisms and BD have been fundamentally understudied. To identify participation of chemokines in BD pathogenesis, we examined genetic variants of several chemokine and chemokine receptor genes.

METHODS

The study population comprised 200 patients with BD and 195 age- and sex-matched healthy controls. Genotyping of monocyte chemotactic protein 1 (MCP-1) A2518G, CCR2 V64I, CCR5 Δ32, CCR5 A55029G, stromal cell-derived factor 1 (SDF-1) 3'A, and CXCR4 C138T polymorphisms was performed using polymerase chain reaction and restriction enzyme digestion.

RESULTS

We found that CCR5-Δ32 II and CXCR4-C138T C+ genotype frequencies contributed to an increased risk for BD. However, no statistical significance could be obtained with these genotypes after Bonferroni correction. A significant asssociation was only found with MCP-1 GG and G+ genotypes, which were markedly more prevalent in patients with BD and these genotypes seemed to significantly increase the risk for BD even after Bonferroni correction.

CONCLUSION

Our findings indicate an association between genetic variants of certain chemokine and chemokine receptor (especially MCP-1) genes and BD. The exact mechanisms by which these variants contribute to BD pathogenesis and their clinical implications need to be further investigated.

Compartmentalized HIV rebound in the central nervous system after interruption of antiretroviral therapy

To design effective eradication strategies, it may be necessary to target HIV reservoirs in anatomic compartments other than blood. This study examined HIV RNA rebound following interruption of antiretroviral therapy (ART) in blood and cerebrospinal fluid (CSF) to determine whether the central nervous system (CNS) might serve as an independent source of resurgent viral replication.

Paired blood and CSF samples were collected longitudinally from 14 chronically HIV-infected individuals undergoing ART interruption. HIV env (C2-V3), gag (p24) and pol (reverse transcriptase) were sequenced from cell-free HIV RNA and cell-associated HIV DNA in blood and CSF using the Roche 454 FLX Titanium platform. Comprehensive sequence and phylogenetic analyses were performed to search for evidence of unique or differentially represented viral subpopulations emerging in CSF supernatant as compared with blood plasma.

Using a conservative definition of compartmentalization based on four distinct statistical tests, nine participants presented a compartmentalized HIV RNA rebound within the CSF after interruption of ART, even when sampled within 2 weeks from viral rebound. The degree and duration of viral compartmentalization varied considerably between subjects and between time-points within a subject. In 10 cases, we identified viral populations within the CSF supernatant at the first sampled time-point after ART interruption, which were phylogenetically distinct from those present in the paired blood plasma and mostly persisted over time (when longitudinal time-points were available). Our data suggest that an independent source of HIV RNA contributes to viral rebound within the CSF after treatment interruption. The most likely source of compartmentalized HIV RNA is a CNS reservoir that would need to be targeted to achieve complete HIV eradication.

Cerebrospinal fluid analysis in the HIV infection and compartmentalization of HIV in the central nervous system

The nervous system plays an important role in HIV infection. The purpose of this review is to discuss the indications for cerebrospinal fluid (CSF) analysis in HIV infection in clinical practice. CSF analysis in HIV infection is indicated for the diagnosis of opportunistic infections and co-infections, diagnosis of meningitis caused by HIV, quantification of HIV viral load, and analysis of CNS HIV compartmentalization. Although several CSF biomarkers have been investigated, none are clinically applicable. The capacity of HIV to generate genetic diversity, in association with the constitutional characteristics of the CNS, facilitates the generation of HIV quasispecies in the CNS that are distinct from HIV in the systemic circulation. CSF analysis has a well-defined and valuable role in the diagnosis of CNS infections in HIV/AIDS patients. Further research is necessary to establish a clinically applicable biomarker for the diagnosis of HIV-associated neurocognitive disorders.

Plasma and Cerebrospinal Fluid Biomarkers Predict Cerebral Injury in HIV-Infected Individuals on Stable Combination Antiretroviral Therapy

OBJECTIVES

HIV-associated brain injury persists despite combination antiretroviral therapy, but contributing factors remain poorly understood. We postulated that inflammation-associated biomarkers will be associated with cerebral injury on proton magnetic resonance spectroscopy in chronically HIV-infected subjects.

METHODS

Five biomarkers were measured in 197 HIV-infected subjects: soluble CD14, MCP-1, IP-10, MIP-1β, and fractalkine. Levels of N-acetyl aspartate (NAA), Choline (Cho), Myoinositol (MI), Glutamate + Glutamine (Glx), and Creatine (Cr) were acquired in the midfrontal cortex (MFC), frontal white matter, and basal ganglia (BG). Predictive models were built through linear regression, and the best models were chosen using the Akaike Information Criterion.

RESULTS

Increases in plasma or CSF MCP-1 were associated with lower NAA/Cr in the MFC and BG, whereas metabolite changes in the frontal white matter for NAA/Cr, GlxCr, and Cho/Cr were explained almost exclusively by a single factor, sCD14. Plasma and CSF levels of this factor were also significantly associated with Glx/Cr in MFC and BG. Higher CSF FKN was associated with higher NAA/Cr in BG. Best predictors for higher Cho/Cr in BG and MFC were CSF sCD14 and CSF MIP-1β. Plasma and CSF IP-10 were only associated with Cho/Cr in MFC. Of the 3 models that simultaneously accounted for both plasma and CSF, there were more associations between CSF biomarkers and magnetic resonance spectroscopy metabolites.

CONCLUSIONS

Markers of inflammation and immune activation, in particular MCP-1 and sCD14, predominantly reflecting CNS sources, contribute to the persistence of brain injury in a metabolite and region-dependent manner in chronically HIV-infected patients on stable combination antiretroviral therapy.

Neuropathogenesis of HIV-associated neurocognitive disorders: roles for immune activation, HIV blipping and viral tropism

PURPOSE OF REVIEW

The purpose of this study is to discuss why HIV-associated neurocognitive disorders (HAND) persist despite apparently effective HIV suppression by highly active antiretroviral therapy (ART).

RECENT FINDINGS

As many as 50% of HIV-infected individuals suffer from HAND despite ART suppression of HIV replication to apparently undetectable levels in most treated individuals. Prior to ART, HIV-associated dementia (HAD), the severest form of HAND, affected nearly 20% of infected individuals; HAD now affects only nearly 2% of ART-treated persons, although less severe HAND forms persist. Recent studies link persistent immune activation, inflammation and viral escape/blipping in ART-treated individuals, as well as comorbid conditions, to HIV disease progression and increased HAND risk. Despite sustained HIV suppression in most ART-treated individuals, indicated by routine plasma monitoring and occasional cerebrospinal fluid (CSF) monitoring, 'blips' of HIV replication are often detected with more frequent monitoring, thus challenging the concept of viral suppression. Although the causes of HIV blipping are unclear, CSF HIV blipping associates with neuroinflammation and, possibly, central nervous system (CNS) injury. The current theory that macrophage-tropic HIV strains within the CNS predominate in driving HAND and these associated factors is now also challenged.

SUMMARY

Protection of the CNS by ART is incomplete, probably due to combined effects of incomplete HIV suppression, persistent immune activation and host comorbidity factors. Adjunctive therapies to ART are necessary for more effective protection.

Cerebrospinal fluid (CSF) CD8+ T-cells that express interferon-gamma contribute to HIV associated neurocognitive disorders (HAND)

Background

HIV associated neurocognitive disorders (HAND) continue to affect cognition and everyday functioning despite anti-retroviral treatment (ART). Previous studies focused on mechanisms related to monocyte/macrophage mediated inflammation. However, in the ART era, there is increasing evidence for the involvement of CD8+ T-cells in CNS pathogenesis.

Methods

To investigate the relationship between T-cell responses and neurocognitive impairment (NCI), cerebrospinal fluid (CSF) and peripheral blood CD4+ and CD8+ T-cell intracellular cytokine (IFNγ, IL-2, TNFα) and lytic marker (CD107a) expression were assessed in HIV infected subjects who underwent comprehensive neurocognitive (NC) evaluation and either initiated or changed ART.

Results

Data were collected from 31 participants at 70 visits. The frequency of cytokine expressing T-cells in CSF was significantly higher than in peripheral blood for CD4+T-cells: TNFα, IL-2, IFNγ and CD8+T-cells: IL-2 and IFNγ. Analysis of T-cell activity and NCI as a function of CSF HIV RNA levels suggested a general association between NCI, high CSF CD8+ (but not CD4+T-cell) cytokine expression and CSF HIV RNA <10³ copies/ml (p<0.0001). Specifically, CSF CD8+ T-cell IFNγ expression correlated with severity of NCI (r = 0.57, p = 0.004). Multivariable analyses indicated that CSF CD8+T-cell IFNγ and myeloid activation (CD163) contributed equally and independently to cognitive status and a composite variable produced the strongest correlation with NCI (r = 0.83, p = 0.0001). In contrast, CD8+ cytolytic activity (CD107a expression) was negatively correlated with NCI (p = 0.05) but was dependent on CD4 levels >400/μl and low CSF HIV RNA levels (<10³ copies/ml). In our longitudinal analysis of 16 subjects, higher CSF CD8+IFNγ expression at baseline predicted NC decline at follow-up (p = 0.02). Severity of NCI at follow-up correlated with level of residual HIV RNA in CSF.

Conclusions

Presence of IFNγ expressing CD8+ T-cells, absence of cytolytic CD8+ T-cells, high myeloid activation, and failure of ART to suppress HIV replication in CSF contribute to increased risk of HAND.

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.

Evidence for an immune role on cognition in schizophrenia: a systematic review

Objective:

Recent evidence has associated immune and inflammatory changes to cognitive performance in many diseases, including schizophrenia. Since this is a new research field where concepts are not yet solid and new questions and hypothesis are still arising, the present study aimed at summarizing the available clinical data associating schizophrenia, cognition and inflammation/immune function.

Methods:

A systematic review of the literature was made by searching the following terms in Medline: “schizophrenia or psychosis or psychotic” AND “inflamm* or immun* or cytokine or IL-* or TNF-* or kynureni* or KYNA”, AND “cognit* or attention or memory or executive function”.

Results:

Seventy five papers were identified using the selected terms, and seven papers were included in the review. Papers excluded focused mainly on basic research or other neuropsychiatric disorders.

Conclusions:

Recent findings link inflammatory markers to cognition in schizophrenia, suggesting that inflammation is associated with worst cognitive performance. Microglial activation, monoaminergic imbalance, brain abnormalities and the kynurenine pathway are possible mechanisms underlying cognitive impairment in schizophrenia. Clinical trials with addition of immunomodulatory drugs have shown promising results, opening new windows to tackle cognition in schizophrenia.

Cognitive impairment and major depressive disorder in HIV infection and cerebrospinal fluid biomarkers

Cognitive impairment and major depressive disorder (MDD) are common HIV-1 central nervous system (CNS) complications. Their frequencies in AIDS patients are 36% and 45%, respectively. The diagnoses of HIV cognitive impairment are made by clinical criteria, no single laboratory test or biomarker establishes the diagnosis. Factors of indirect neuronal injury related with the pathophysiology of the HIV infection in the CNS, are the factors studied as biomarkers. In the present no biomarker is established to the diagnosis of HIV cognitive impairment, much still needs to be done. We review in this paper some biomarkers in cerebrospinal fluid that could be valuable to the diagnosis of HIV cognitive impairment. Diagnosing depression in the context of HIV can be challenging, to identify a biomarker that could help in the diagnosis would be very important, although MDD risks and neurobiology are still poorly understood.

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.

Mechanisms of HIV entry into the CNS: increased sensitivity of HIV infected CD14+CD16+ monocytes to CCL2 and key roles of CCR2, JAM-A, and ALCAM in diapedesis

As HIV infected individuals live longer, the prevalence of HIV associated neurocognitive disorders is increasing, despite successful antiretroviral therapy. CD14(+)CD16(+) monocytes are critical to the neuropathogenesis of HIV as they promote viral seeding of the brain and establish neuroinflammation. The mechanisms by which HIV infected and uninfected monocytes cross the blood brain barrier and enter the central nervous system are not fully understood. We determined that HIV infection of CD14(+)CD16(+) monocytes resulted in their highly increased transmigration across the blood brain barrier in response to CCL2 as compared to uninfected cells, which did not occur in the absence of the chemokine. This exuberant transmigration of HIV infected monocytes was due, at least in part, to increased CCR2 and significantly heightened sensitivity to CCL2. The entry of HIV infected and uninfected CD14(+)CD16(+) monocytes into the brain was facilitated by significantly increased surface JAM-A, ALCAM, CD99, and PECAM-1, as compared to CD14(+) cells that are CD16 negative. Upon HIV infection, there was an additional increase in surface JAM-A and ALCAM on CD14(+)CD16(+) monocytes isolated from some individuals. Antibodies to ALCAM and JAM-A inhibited the transmigration of both HIV infected and uninfected CD14(+)CD16(+) monocytes across the BBB, demonstrating their importance in facilitating monocyte transmigration and entry into the brain parenchyma. Targeting CCR2, JAM-A, and ALCAM present on CD14(+)CD16(+) monocytes that preferentially infiltrate the CNS represents a therapeutic strategy to reduce viral seeding of the brain as well as the ongoing neuroinflammation that occurs during HIV pathogenesis.

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.

Genotypical diversity of HIV clades and central nervous system impairment

The central nervous system (CNS) and the immune system are considered major target organs for HIV infection. The neurological manifestations directly related to HIV are acute viral meningitis, chronic meningitis, HIV associated dementia, vacuolar myelopathy and involvement of the peripheral nervous system. Changes in diagnosis and clinical management have changed the aspect of HIV infection so that it is no longer a fatal disease, and has become a chronic disease requiring sustained medical management. After HAART the incidence of most opportunistic infections, including those affecting the CNS, has dropped markedly. Some studies suggest that neurological involvement of infected patient occur with different frequency, depending on HIV subtype involved in the infection. Subtype C may have reduced neuroinvasive capacity, possibly due to its different primary conformation of HIV transactivating regulatory protein (Tat), involved in monocyte chemotaxis. This review focus on physiopathologic aspects of HIV infection in CNS and its correlation with HIV clades.

Cognitive impairment is related to oxidative stress and chemokine levels in first psychotic episodes

INTRODUCTION

This study measures the levels of various markers of oxidative stress and inflammation in blood samples from first-episode psychosis (FEP) patients, and examines the association between these peripheral biomarkers and cognitive performance at 6 months after treatment.

METHODS

Twenty-eight FEP patients and 28 healthy controls (matched by age, sex and educational level) had blood samples taken at admission for assessment of total antioxidant status, superoxide dismutase (SOD), total glutathione (GSH), catalase (CAT), glutathione peroxidase, lipid peroxidation, nitrites and the chemokine monocyte chemoattractant protein-1 (MCP-1). A battery of cognitive tests was also applied to the healthy controls and those FEP patients who were in remission at 6 months after the acute episode.

RESULTS

FEP patients had significantly lower levels of total antioxidant status, catalase and glutathione peroxidase, compared with the healthy controls. Regression analyses found that MCP-1 levels were negatively associated with learning and memory (verbal and working), nitrite levels were negatively associated with executive function, and glutathione levels were positively associated with executive function.

CONCLUSION

Our results suggest an association between certain peripheral markers of oxidative stress and inflammation and specific aspects of cognitive functioning in FEP patients. Further studies on the association between MCP-1 and cognition are warranted.

HIV-1 neuroimmunity in the era of antiretroviral therapy

Human immunodeficiency virus type 1 (HIV-1)-associated neurocognitive disorders (HAND) can affect up to 50% of infected people during the disease course. While antiretroviral therapies have substantively increased the quality of life and reduced HIV-1-associated dementia, less severe minor cognitive and motor deficits continue. Trafficking of HIV-1 into the central nervous system (CNS), peripheral immune activation, dysregulated glial immunity, and diminished homeostatic responses are the disease-linked pathobiologic events. Monocyte-macrophage passage into the CNS remains an underlying force for disease severity. Monocyte phenotypes may change at an early stage of cell maturation and immune activation of hematopoietic stem cells. Activated monocytes are pulled into the brain in response to chemokines made as a result of glial inflammatory processes, which in turn, cause secondary functional deficits in neurons. Current therapeutic approaches are focused on adjunctive and brain-penetrating antiretroviral therapies. These may attenuate virus-associated neuroinflammatory activities thereby decreasing the severity and frequency of HAND.

Coordinated regulation of SIV replication and immune responses in the CNS

Central nervous system (CNS) invasion during acute-stage HIV-infection has been demonstrated in a small number of individuals, but there is no evidence of neurological impairment at this stage and virus infection in brain appears to be controlled until late-stage disease. Using our reproducible SIV macaque model to examine the earliest stages of infection in the CNS, we identified immune responses that differentially regulate inflammation and virus replication in the brain compared to the peripheral blood and lymphoid tissues. SIV replication in brain macrophages and in brain of SIV-infected macaques was detected at 4 days post-inoculation (p.i.). This was accompanied by upregulation of innate immune responses, including IFNβ, IFNβ-induced gene MxA mRNA, and TNFα. Additionally, IL-10, the chemokine CCL2, and activation markers in macrophages, endothelial cells, and astrocytes were all increased in the brain at four days p.i. We observed synchronous control of virus replication, cytokine mRNA levels and inflammatory markers (MHC Class II, CD68 and GFAP) by 14 days p.i.; however, control failure was followed by development of CNS lesions in the brain. SIV infection was accompanied by induction of the dominant-negative isoform of C/EBPβ, which regulates SIV, CCL2, and IL6 transcription, as well as inflammatory responses in macrophages and astrocytes. This synchronous response in the CNS is in part due to the effect of the C/EBPβ on virus replication and cytokine expression in macrophage-lineage cells in contrast to CD4+ lymphocytes in peripheral blood and lymphoid tissues. Thus, we have identified a crucial period in the brain when virus replication and inflammation are controlled. As in HIV-infected individuals, though, this control is not sustained in the brain. Our results suggest that intervention with antiretroviral drugs or anti-inflammatory therapeutics with CNS penetration would sustain early control. These studies further suggest that interventions should target HIV-infected individuals with increased CCL2 levels or HIV RNA in the CNS.

Cerebrospinal fluid levels of chemokines in HIV infected patients with and without opportunistic infection of the central nervous system

Chemokines are chemoattractant cytokines involved in the immune response of a wide variety of diseases. There are few studies assessing their role in opportunistic infections in HIV-infected patients. In this study, we measured CC and CXC chemokines in cerebrospinal fluid (CSF) samples obtained from 40 HIV-infected patients with or without opportunistic infections of the central nervous system (CNS). CSF samples were also analyzed for quantification of total protein, cell count and HIV-1 RNA. HIV+ patients with cryptococcal meningitis had higher levels of CCL2, CCL3, CCL5, CXCL9 and CXCL10 when compared to patients without opportunistic neurological infections. Furthermore, HIV+ patients with associated cryptococcal meningitis had higher levels of CCL3, CXCL9 and CXCL10 when compared to HIV+ patients with associated toxoplasmic encephalitis. CCL3 and CXCL9 levels were positively correlated with CSF HIV-1 RNA levels, CSF protein concentration, and CSF cell count. CXCL10 level was correlated with the CSF viral load and the CSF cell count and CCL5 level was correlated with the CSF cell count. In conclusion, the profile of chemokines in CSF of HIV patients may differ according to the modality of the presented opportunistic infection and according to other biological markers, such as viral load in CSF. These differences are probably related to different patterns of neuroinflammatory responses displayed by patients with different opportunistic neurological infections.

Activation of central nervous system inflammatory pathways by interferon-alpha: relationship to monoamines and depression

BACKGROUND

Interferon (IFN)-alpha has been used to study the effects of innate immune cytokines on the brain and behavior in humans. The degree to which peripheral administration of IFN-alpha accesses the brain and is associated with a central nervous system (CNS) inflammatory response is unknown. Moreover, the relationship among IFN-alpha-associated CNS inflammatory responses, neurotransmitter metabolism, and behavior has yet to be established.

METHODS

Twenty-four patients with hepatitis C underwent lumbar puncture and blood sampling after approximately 12 weeks of either no treatment (n = 12) or treatment with pegylated IFN-alpha 2b (n = 12). Cerebrospinal fluid (CSF) and blood samples were analyzed for proinflammatory cytokines and their receptors as well as the chemokine, monocyte chemoattractant protein-1 (MCP-1), and IFN-alpha. Cerebrospinal fluid samples were additionally analyzed for monoamine metabolites and corticotropin releasing hormone. Depressive symptoms were assessed using the Montgomery Asberg Depression Rating Scale.

RESULTS

Interferon-alpha was detected in the CSF of all IFN-alpha-treated patients and only one control subject. Despite no increases in plasma IL-6, IFN-alpha-treated patients exhibited significant elevations in CSF IL-6 and MCP-1, both of which were highly correlated with CSF IFN-alpha concentrations. Of the immunologic and neurotransmitter variables, log-transformed CSF concentrations of the serotonin metabolite, 5-hydroxyindoleacetic acid (5-HIAA), were the strongest predictor of depressive symptoms. Log-transformed CSF concentrations of IL-6, but not IFN-alpha or MCP-1, were negatively correlated with log-transformed CSF 5-HIAA (r(2) = -.25, p < .05).

CONCLUSIONS

These data indicate that a peripherally administered cytokine can activate a CNS inflammatory response in humans that interacts with monoamine (serotonin) metabolism, which is associated with depression.

Antioxidant enzyme dysfunction in monocytes and CSF of Hispanic women with HIV-associated cognitive impairment

HIV-associated cognitive neurological disorders (HAND) prevail in the antiretroviral therapy era. Proteomics analysis of CSF revealed expression of Cu/Zn superoxide dismutase (Cu/Zn SOD) in Hispanic women with cognitive impairment (CI). We tested the hypothesis that there is reduced capacity of antioxidant enzymes in CI by measures of expression and activity of Cu/Zn SOD, catalase, and Se-glutathione peroxidase in HAND. Our results showed that the function of these antioxidants was decreased in the CSF and monocytes of women with CI. These findings have important implications regarding their possible contribution to oxidative stress and in the diagnosis and therapy for HAND.

Duffy antigen receptor for chemokines mediates trans-infection of HIV-1 from red blood cells to target cells and affects HIV-AIDS susceptibility

Duffy antigen receptor for chemokines (DARC) expressed on red blood cells (RBCs) influences plasma levels of HIV-1-suppressive and proinflammatory chemokines such as CCL5/RANTES. DARC is also the RBC receptor for Plasmodium vivax. Africans with DARC -46C/C genotype, which confers a DARC-negative phenotype, are resistant to vivax malaria. Here, we show that HIV-1 attaches to RBCs via DARC, effecting trans-infection of target cells. In African Americans, DARC -46C/C is associated with 40% increase in the odds of acquiring HIV-1. If extrapolated to Africans, approximately 11% of the HIV-1 burden in Africa may be linked to this genotype. After infection occurs, however, DARC-negative RBC status is associated with slower disease progression. Furthermore, the disease-accelerating effect of a previously described CCL5 polymorphism is evident only in DARC-expressing and not in DARC-negative HIV-infected individuals. Thus, DARC influences HIV/AIDS susceptibility by mediating trans-infection of HIV-1 and by affecting both chemokine-HIV interactions and chemokine-driven inflammation.

Antiretroviral therapy and central nervous system HIV type 1 infection

Central nervous system (CNS) human immunodeficiency virus type 1 (HIV-1) infection begins during primary viremia and continues throughout the course of untreated systemic infection. Although frequently accompanied by local inflammatory reactions detectable in cerebrospinal fluid (CSF), CNS HIV-1 infection usually is not clinically apparent. In a minority of patients, CNS HIV-1 infection evolves into encephalitis during the late stages of systemic infection, which compromises brain function and presents clinically as acquired immunodeficiency syndrome dementia complex (ADC). Combination antiretroviral therapy (ART) has had a major impact on all aspects of CNS HIV-1 infection and disease. In those with asymptomatic infection, ART usually effectively suppresses HIV-1 in CSF and markedly reduces the incidence of symptomatic ADC. In those presenting with ADC, ART characteristically prevents neurological progression and leads to variable, and at times substantial, recovery. Similarly, treatment has reduced CNS opportunistic infections. With better control of these severe disorders, attention has turned to the possible consequences of chronic silent infection and the issue of whether indolent, low-grade brain injury might require earlier treatment intervention.

Trypanosoma cruzi (Chagas' disease agent) reduces HIV-1 replication in human placenta

Background

Several factors determine the risk of HIV mother-to-child transmission (MTCT), such as coinfections in placentas from HIV-1 positive mothers with other pathogens. Chagas' disease is one of the most endemic zoonoses in Latin America, caused by the protozoan Trypanosoma cruzi. The purpose of the study was to determine whether T. cruzi modifies HIV infection of the placenta at the tissue or cellular level.

Results

Simple and double infections were carried out on a placental histoculture system (chorionic villi isolated from term placentas from HIV and Chagas negative mothers) and on the choriocarcinoma BeWo cell line. Trypomastigotes of T. cruzi (VD lethal strain), either purified from mouse blood or from Vero cell cultures, 24 h-supernatants of blood and cellular trypomastigotes, and the VSV-G pseudotyped HIV-1 reporter virus were used for the coinfections. Viral transduction was evaluated by quantification of luciferase activity. Coinfection with whole trypomastigotes, either from mouse blood or from cell cultures, decreased viral pseudotype luciferase activity in placental histocultures. Similar results were obtained from BeWo cells. Supernatants of stimulated histocultures were used for the simultaneous determination of 29 cytokines and chemokines with the Luminex technology. In histocultures infected with trypomastigotes, as well as in coinfected tissues, IL-6, IL-8, IP-10 and MCP-1 production was significantly lower than in controls or HIV-1 transducted tissue. A similar decrease was observed in histocultures treated with 24 h-supernatants of blood trypomastigotes, but not in coinfected tissues.

Conclusion

Our results demonstrated that the presence of an intracellular pathogen, such as T. cruzi, is able to impair HIV-1 transduction in an in vitro system of human placental histoculture. Direct effects of the parasite on cellular structures as well as on cellular/viral proteins essential for HIV-1 replication might influence viral transduction in this model. Nonetheless, additional mechanisms including modulation of cytokines/chemokines at placental level could not be excluded in the inhibition observed. Further experiments need to be conducted in order to elucidate the mechanism(s) involved in this phenomenon. Therefore, coinfection with T. cruzi may have a deleterious effect on HIV-1 transduction and thus could play an important role in viral outcome at the placental level.

Biomarkers of HIV related central nervous system disease

In this review we critically assess biomarkers of the direct effects of HIV related brain disease. This area is becoming increasingly complex because of the presence of confounds and varying degrees of activity of HIV brain disease. Sensitive and specific biomarkers are urgently needed although existing biomarkers do have some utility. The review will focus on the practical implications of the more established biomarkers. We discuss blood, cerebrospinal fluid and neurophysiological biomarkers but not neuroimaging techniques as they are beyond the scope of this review.

Polymorphisms of Cx(3)CR1 and CXCR6 receptors in relation to HAART therapy of HIV type 1 patients

The chemokine polymorphisms CXCR6-3E/K, In1.1T/C, H7 haplotype, CX(3)CR1-V249I, and CX(3)CR1-T280M have been shown to affect the course of HIV infection. We studied their influence on immunologic and virologic response to HAART in a group of 143 HIV-1 patients. We performed Kaplan-Meier analysis using the following end-point criteria: (1) time from HAART initiation to undetectable viral load (VL < 50 copies/ml), (2) maximum duration of viral suppression, (3) time from HAART administration until CD4 elevation above 200 cells/microl for patients with baseline CD4 below 200 cells/microl and above 500 cells/microl for patients with baseline CD4 between 200 and 500 cells/microl, respectively, and (4) time from HAART initiation until CD4 reduction below baseline values. Our results revealed an improved immunologic response to HAART in patients with the CX(3)CR1-249I or CX(3)CR1-280M allele. On the contrary, patients with initial VL suppression due to HAART showed a faster virologic failure in the presence of the CXCR6-3K allele. The In1.1T/C polymorphism and H7 haplotype did not reveal any specific effect on HAART response.

Monocyte chemoattractant protein-1 and atherosclerosis: is there room for an additional biomarker?

Atherosclerosis is an inflammatory disease in which several chemokines are implicated. The roles of these molecules extend from the recruitment of circulating inflammatory cells to the activation of inflammatory and pro-thrombotic cascades, which ultimately leads to an atherosclerosis-related event. One of the most studied chemokines is monocyte chemoattractant protein-1 (CCL2), which has been strongly linked to atherosclerosis in both animal and human studies. The higher the expression of either the CCL2 gene or its receptor CCR-2, the higher the likelihood of developing atherosclerosis in genetically-modified animals. Conversely, the deletion of either CCL2 or its receptor is followed by a significant reduction in the development of atherosclerotic plaques. Studies in humans yield controversial results. Most of these studies linked the plasma CCL2 concentration to the occurrence of atherosclerosis or related events; however, this relationship does not seem to be independent of the classical, known risk factors. Currently, there are no suitable analytical tools to reach strong conclusions with respect to the value of plasma CCL2 concentration as a biomarker of atherosclerosis, but experimental evidence suggests that the CCL2/CCR2 pathway should be further explored as a diagnostic, prognostic and therapeutic target.

Dichotomous effects of C-C chemokines in HIV-1 pathogenesis

Chemokines play a critical role in shaping innate and adaptive immunity. These molecules also participate in maintaining the immune balance in the body. Apart from their regulatory role, these mediators are involved in several inflammatory and autoimmune diseases including viral infection such as HIV-1/AIDS. Chemokine co-receptor CCR5 and CXCR4 and their ligands significantly contribute to HIV-1 disease progression. C-C chemokines such CCL3, CCL4 and CCL5 have been shown to possess antiviral effects by binding to HIV-1 co-receptors. CCL2, a member of the C-C chemokine family, displays a different feature instead. It is a potential enhancer rather than inhibitor of viral replication, a property exhibited by most of the C-C chemokine members. In addition, the role of CCL2 is well established in forming a Th2 type of response by directing differentiation of Th0 cells towards Th2 type, a unique feature of HIV-1 disease. We propose a hypothesis in which the chemotactic nature of CCL2 drives recruitment of target cells to the site of infection as one of the mechanisms operating in vivo that favours viral replication and eventually a high viral load in infected individuals.

Relationship of CSF leukocytosis to compartmentalized changes in MCP-1/CCL2 in the CSF of HIV-infected patients undergoing interruption of antiretroviral therapy

Although monocyte chemoattractant protein (MCP-1)/CCL2 is believed to mediate trafficking of HIV-activated leukocytes into the CNS, its role has not been studied directly in humans. To evaluate MCP-1's effects on CNS leukocyte infiltration, we measured CSF leukocytes and MCP-1 levels in serial plasma and cerebrospinal fluid (CSF) samples from subjects who experienced large increases in viral load after interrupting antiretrovirals. Following large increases in CSF MCP-1, CSF leukocytosis (15-166 cells/microL) developed in 4 of 6 subjects. Both initial MCP-1 levels and subsequent changes were 3-fold larger in CSF than plasma. The magnitude and timing of changes suggested that MCP-1 triggers the development of CSF pleocytosis.