Cerebrospinal fluid neopterin: an informative biomarker of central nervous system immune activation in HIV-1 infection

Changes in Cerebrospinal Fluid Proteins across the Spectrum of Untreated and Treated Chronic HIV-1 Infection

Using the Olink Explore 1536 platform, we measured 1,463 unique proteins in 303 cerebrospinal fluid (CSF) specimens from four clinical centers that included uninfected controls and 12 groups of people living with HIV-1 infection representing the spectrum of progressive untreated and treated chronic infection. We present three initial analyses of these measurements: an overview of the CSF protein features of the sample; correlations of the CSF proteins with CSF HIV-1 RNA and neurofilament light chain protein (NfL) concentrations; and comparison of the CSF proteins in HIV-associated dementia ( HAD ) and neurosymptomatic CSF escape ( NSE ). These reveal a complex but coherent picture of CSF protein changes that includes highest concentrations of many proteins during CNS injury in the HAD and NSE groups and variable protein changes across the course of neuroasymptomatic systemic HIV-1 progression, including two common patterns, designated as lymphoid and myeloid patterns, related to the principal involvement of their underlying inflammatory cell lineages. Antiretroviral therapy reduced CSF protein perturbations, though not always to control levels. The dataset of these CSF protein measurements, along with background clinical information, is posted online. Extended studies of this unique dataset will provide more detailed characterization of the dynamic impact of HIV-1 infection on the CSF proteome across the spectrum of HIV-1 infection, and further the mechanistic understanding of HIV-1-related CNS pathobiology.

Multimodal Approach to Neurocognitive Function in People Living with HIV in the cART Era: A Comprehensive Review

Combination antiretroviral treatment (cART) has revolutionized the management of human immunodeficiency virus (HIV) and has markedly improved the disease burden and life expectancy of people living with HIV. HIV enters the central nervous system (CNS) early in the course of infection, establishes latency, and produces a pro-inflammatory milieu that may affect cognitive functions, even in the cART era. Whereas severe forms of neurocognitive impairment (NCI) such as HIV-associated dementia have declined over the last decades, milder forms have become more prevalent, are commonly multifactorial, and are associated with comorbidity burdens, mental health, cART neurotoxicity, and ageing. Since 2007, the Frascati criteria have been used to characterize and classify HIV-associated neurocognitive disorders (HAND) into three stages, namely asymptomatic neurocognitive impairment (ANI), mild neurocognitive disorder (MND), and HIV-associated dementia (HAD). These criteria are based on a comprehensive neuropsychological assessment that presupposes the availability of validated, demographically adjusted, and normative population data. Novel neuroimaging modalities and biomarkers have been proposed in order to complement NCI assessments, elucidate neuropathogenic mechanisms, and support HIV-associated NCI diagnosis, monitoring, and prognosis. By integrating neuropsychological assessments with biomarkers and neuroimaging into a holistic care approach, clinicians can enhance diagnostic accuracy, prognosis, and patient outcomes. This review interrogates the value of these modes of assessment and proposes a unified approach to NCI diagnosis.

HIV-1-infected T cell clones are shared across cerebrospinal fluid and blood during ART

The central nervous system HIV reservoir is incompletely understood and is a major barrier to HIV cure. We profiled people with HIV (PWH) and uninfected controls through single-cell transcriptomic and T cell receptor (TCR) sequencing to understand the dynamics of HIV persistence in the CNS. In PWH on ART, we found that most participants had single cells containing HIV-1 RNA, which was found predominantly in CD4 central memory T cells, in both cerebrospinal fluid (CSF) and blood. HIV-1 RNA-containing cells were found more frequently in CSF than blood, indicating a higher burden of reservoir cells in the CNS than blood for some PWH. Most CD4 T cell clones containing infected cells were compartment specific, while some (22%) - including rare clones with members of the clone containing detectable HIV RNA in both blood and CSF - were found in both CSF and blood. These results suggest that infected T cells trafficked between tissue compartments and that maintenance and expansion of infected T cell clones contributed to the CNS reservoir in PWH on ART.

Cerebrospinal Fluid Viral Escape on Highly Active Antiretroviral Therapy: Analysis from Single Tertiary Care Centre

HIV-infected individuals receiving regular antiretroviral therapy (ART) can present with a high viral load in cerebrospinal fluid (CSF) at times when it is suppressed in blood. This study presents data of HIV-infected patients who had undetectable or low plasma viral load in blood but presented with neurological signs and symptoms and were diagnosed to have CSF HIV viral escape. Records were reviewed for clinical manifestations, details of opportunistic or coinfection, and HIV viral copies in plasma and CSF at time of diagnosis of CSF escape. A total of 10,200 HIV-infected individuals were registered in HIV care till December 31, 2021. Nineteen individuals (14 virologically confirmed and 5 clinically) were diagnosed with high viral copies in CSF from June 2014 to December 2021. Mean age was 41.5 ± 9.2 (median, 39.5; range, 30-62) years. Average duration of antiretroviral treatment received at the time of diagnosis of CSF escape was 10.1 years. Median plasma HIV-viral copies were 2,469.8 (undetectable to 29,418) and in CSF were 12,773.7 (n = 14, range, 1,340-48,530) copies/mL. HIV viral copies in CSF were significantly higher than in plasma at the time of presentation (p = .003). ART regimen switch was done after identification of HIV CSF escape. Seventeen patients were alive with a regular follow-up of average 35 (range 7-66) months. All had documented clinical improvement with reversal of neurological impairment after ART switch. There was one death and one lost to follow-up. Early identification and timely intervention in CSF viral escape could revert severe neurological impairment and improves treatment outcome.

Serum Neopterin, Biopterin, Tryptophan, and Kynurenine Levels in Patients with Fabry Disease

Background

Fabry disease is characterized by the accumulation of globotriaosylceramide. Substrate accumulation in lysosomes is thought to trigger an inflammatory response and is responsible for progressive organ damage through the induction of autoimmunity. The levels of pteridine and kynurenine pathway metabolites increase when immune activation is observed and are employed to monitor several diseases and determine prognosis.

Aims

To elucidate the effects of immune activation on the pathophysiology of Fabry disease and to investigate the potential utility of pteridine and kynurenine metabolites.

Study Design

A prospective case-control study.

Methods

In this study, 33 patients with Fabry disease and 33 age-and sex-matched healthy controls were included. Blood pteridine and kynurenine metabolites were studied in both groups. Organ involvement in Fabry disease and its correlation with the pteridine and kynurenine pathways were also investigated.

Results

The patients’ neopterin and biopterin levels and the tryptophan/kynurenine ratio were statistically higher than those of the healthy control group (p < 0.05). A statistically significant association was found between neopterin levels and hypertrophic cardiomyopathy, cardiac arrhythmias, and GFR values (p = 0.044, p = 0.021, and p = 0.030, respectively), tryptophan and corneal verticillate, hearing loss and tinnitus (p = 0.010, p = 0.009 and p = 0.046, respectively), and kynurenine levels and valvular heart disease (p = 0.020).

Conclusion

From the onset of the disease, patients with Fabry disease exhibited elevated levels of inflammation and immune activation. Furthermore, inflammation and immune activation markers can be used as early disease biomarkers.

CD4 dim CD8 bright T cells are inversely associated with neuro-inflammatory markers among people with HIV

OBJECTIVE

HIV-associated neuroinflammation persists in the brain despite suppressive combination antiretroviral therapy (cART). We evaluated associations between a subset of CD8 + T cells, termed CD4 dim CD8 bright T cells, and soluble markers of immune activation and/or neuroinflammation in the cerebrospinal fluid (CSF) and plasma of people with HIV (PWH).

DESIGN

Fifteen cART-naive PWH were enrolled and underwent blood draw, lumbar puncture for CSF collection, and neuropsychological tests at week 0 (pre-cART) and 24 weeks after cART initiation.

METHODS

CSF and peripheral blood T cells were evaluated with flow cytometry and soluble markers of immune activation were measured by multiplex and singleplex assays. Spearman bootstrap correlation coefficients with 10 000 resamples were computed and reported with corresponding 95% confidence intervals (CIs) for each marker of interest and T-cell type.

RESULTS

The frequency of CSF CD4 dim CD8 bright T cells at week 0 was inversely related with CSF neopterin. In contrast, at week 24, CSF CD4 - CD8 + T cells were positively correlated with CSF s100β, a marker of brain injury. In the blood, at week 0, CD4 dim CD8 bright T cells were inversely correlated with MCP-1, IP-10, IL-8, IL-6, G-CSF, and APRIL and positively correlated with plasma RANTES and MMP1. At week 0, the frequency of blood CD4 - CD8 + were positively correlated with CRP and BAFF.

CONCLUSION

CD4 dim CD8 bright T cells are associated with some anti-inflammatory properties, whereas CD4 - CD8 + T cells may contribute to inflammation and injury. Assessing the contrast between these two cell populations in neuroHIV may inform targeted therapeutic intervention to reduce neuroinflammation and associated neurocognitive impairment.

Elevated Plasma Protein Carbonyl Concentration Is Associated with More Abnormal White Matter in People with HIV

Structural brain abnormalities, including those in white matter (WM), remain common in people with HIV (PWH). Their pathogenesis is uncertain and may reflect multiple etiologies. Oxidative stress is associated with inflammation, HIV, and its comorbidities. The post-translational carbonylation of proteins results from oxidative stress, and circulating protein carbonyls may reflect this. In this cross-sectional analysis, we evaluated the associations between protein carbonyls and a panel of soluble biomarkers of neuronal injury and inflammation in plasma (N = 45) and cerebrospinal fluid (CSF, n = 32) with structural brain MRI. The volume of abnormal WM was normalized for the total WM volume (nAWM). In this multisite project, all regression models were adjusted for the scanner. The candidate covariates included demographics, HIV disease characteristics, and comorbidities. Participants were PWH on virally suppressive antiretroviral therapy (ART) and were mostly white (64.4%) men (88.9%), with a mean age of 56.8 years. In unadjusted analyses, more nAWM was associated with higher plasma protein carbonyls (p = 0.002) and higher CCL2 (p = 0.045). In the adjusted regression models for nAWM, the association with plasma protein carbonyls remained significant (FDR p = 0.018). Protein carbonyls in plasma may be a valuable biomarker of oxidative stress and its associated adverse health effects, including within the central nervous system. If confirmed, these findings would support the hypothesis that reducing oxidative stress could treat or prevent WM injury in PWH.

Urinary neopterin and biopterin indicate that inflammation has a role in autism spectrum disorder

Inflammation is thought to be involved in the pathogenesis of autism spectrum disorder (ASD). Pteridine metabolites are biomarkers of inflammation that increase on immune system activation. In this study, we investigated the urinary pteridine metabolites in ASD patients as a possible biomarker for immune activation and inflammation. This observational, cross-sectional, prospective study collected urine samples from 212 patients with ASD and 68 age- and sex-matched healthy individuals. Urine neopterin (NE) and biopterin (BIO) levels were measured. Patients who had chronic disorders, active infection at the time of sampling, or high C-reactive protein levels were excluded. The urine NE and BIO concentrations were determined by high-performance liquid chromatography. The ratios of both NE and BIO to creatinine (CRE) were used to standardise the measurements. The NE/CRE and NE/BIO levels were significantly higher in ASD patients than controls. Univariate and multivariate models revealed a significant increase in NE/CRE and NE/BIO in ASD patients. There was a significant relationship between the NE/BIO [average area under the curve (AUC) = 0.717; range: 0.637-0.797] and NE/CRE (average AUC = 0.756; range: 0.684-0.828) ratios, which distinguished individuals with ASD from controls. The elevated NE/CRE and NE/BIO ratios suggest that inflammation and T cell-mediated immunity are involved in the pathophysiology of autism. NE/BIO could serve as a diagnostic inflammatory marker in the pathogenesis of ASD.

Impact of antiretroviral therapy intensification with C-C motif chemokine receptor 5 antagonist maraviroc on HIV-associated neurocognitive impairment

OBJECTIVES

Chemokine receptor CCR5 is the principal co-receptor for entry of M-tropic HIV virus into immune cells. It is expressed in the central nervous system and may contribute to neuro-inflammation. The CCR5 antagonist maraviroc (MVC) has been suggested to improve HIV-associated neurocognitive impairment (NCI).

DESIGN

A double-blind, placebo-controlled, 48-week, randomized study of MVC vs. placebo in people with HIV (PWH) on stable antiretroviral therapy (ART) for more than one year in Hawaii and Puerto Rico with plasma HIV RNA less than 50 copies/ml and at least mild NCI defined as an overall or domain-specific neuropsychological z (NPZ) score less than -0.5.

METHODS

Study participants were randomized 2 : 1 to intensification of ART with MVC vs. placebo. The primary endpoint was change in global and domain-specific NPZ modeled from study entry to week 48. Covariate adjusted treatment comparisons of average changes in cognitive outcome were performed using winsorized NPZ data. Monocyte subset frequencies and chemokine expression as well as plasma biomarker levels were assessed.

RESULTS

Forty-nine participants were enrolled with 32 individuals randomized to MVC intensification and 17 to placebo. At baseline, worse NPZ scores were seen in the MVC arm. Comparison of 48-week NPZ change by arm revealed no differences except for a modest improvement in the Learning and Memory domain in the MVC arm, which did not survive multiplicity correction. No significant changes between arms were seen in immunologic parameters.

CONCLUSION

This randomized controlled study found no definitive evidence in favor of MVC intensification among PWH with mild cognitive difficulties.

Mechanisms underlying HIV-associated cognitive impairment and emerging therapies for its management

People living with HIV are affected by the chronic consequences of neurocognitive impairment (NCI) despite antiretroviral therapies that suppress viral replication, improve health and extend life. Furthermore, viral suppression does not eliminate the virus, and remaining infected cells may continue to produce viral proteins that trigger neurodegeneration. Comorbidities such as diabetes mellitus are likely to contribute substantially to CNS injury in people living with HIV, and some components of antiretroviral therapy exert undesirable side effects on the nervous system. No treatment for HIV-associated NCI has been approved by the European Medicines Agency or the US Food and Drug Administration. Historically, roadblocks to developing effective treatments have included a limited understanding of the pathophysiology of HIV-associated NCI and heterogeneity in its clinical manifestations. This heterogeneity might reflect multiple underlying causes that differ among individuals, rather than a single unifying neuropathogenesis. Despite these complexities, accelerating discoveries in HIV neuropathogenesis are yielding potentially druggable targets, including excessive immune activation, metabolic alterations culminating in mitochondrial dysfunction, dysregulation of metal ion homeostasis and lysosomal function, and microbiome alterations. In addition to drug treatments, we also highlight the importance of non-pharmacological interventions. By revisiting mechanisms implicated in NCI and potential interventions addressing these mechanisms, we hope to supply reasons for optimism in people living with HIV affected by NCI and their care providers.

Antiretroviral Therapy Intensification for Neurocognitive Impairment in Human Immunodeficiency Virus

BACKGROUND

Neurocognitive impairment (NCI) in people with HIV (PWH) on antiretroviral therapy (ART) is common and may result from persistent HIV replication in the central nervous system.

METHODS

A5324 was a randomized, double-blind, placebo-controlled, 96-week trial of ART intensification with dolutegravir (DTG) + MVC, DTG + Placebo, or Dual - Placebo in PWH with plasma HIV RNA <50 copies/mL on ART and NCI. The primary outcome was the change on the normalized total z score (ie, the mean of individual NC test z scores) at week 48.

RESULTS

Of 357 screened, 191 enrolled: 71% male, 51% Black race, 22% Hispanic ethnicity; mean age 52 years; mean CD4+ T-cells 681 cells/µL. Most (65%) had symptomatic HIV-associated NC disorder. Study drug was discontinued due to an adverse event in 15 (8%) and did not differ between arms (P = .17). Total z score, depressive symptoms, and daily functioning improved over time in all arms with no significant differences between them at week 48 or later. Adjusting for age, sex, race, study site, efavirenz use, or baseline z score did not alter the results. Body mass index modestly increased over 96 weeks (mean increase 0.32 kg/m2, P = .006) and did not differ between arms (P > .10).

CONCLUSIONS

This is the largest, randomized, placebo-controlled trial of ART intensification for NCI in PWH. The findings do not support empiric ART intensification as a treatment for NCI in PWH on suppressive ART. They also do not support that DTG adversely affects cognition, mood, or weight.

Increasing Neuroinflammation Relates to Increasing Neurodegeneration in People with HIV

BACKGROUND

HIV infection causes neuroinflammation and immune activation (NIIA) and systemic inflammation and immune activation (SIIA), which in turn drive neurodegeneration (ND). Cross-sectionally, higher levels of NIIA biomarkers correlate with increased biomarkers of ND. A more convincing confirmation would be a longitudinal demonstration.

METHODS

PWH in the US multisite CHARTER Aging project were assessed at a baseline visit and after 12 years using standardized evaluations. We measured a panel of 14 biomarkers of NIIA, SIIA, and ND in plasma and CSF at two time points and calculated changes from baseline to the 12-year visit. Factor analysis yielded simplified indices of NIIA, SIIA, and ND.

RESULTS

The CSF NIIA factor analysis yielded Factor1 loading on soluble tumor necrosis factor type-2 (sTNFR-II) and neopterin, and Factor2, loading on MCP1, soluble CD14, and IL-6. The SIIA factor analysis yielded Factor1 loading on CRP, D-dimer, and Neopterin; Factor2 loading on sTNFR-II. The ND analysis yielded Factor1 loading on Phosphorylated tau (p-tau) and Aβ42; Factor2 loading on NFL. NIIA Factor1, but not Factor2, correlated with increases in CSF NFL (r = 0.370, p = 0.0002).

CONCLUSIONS

Increases in NIIA and SIIA in PWH were associated with corresponding increases in ND, suggesting that reducing neuro/systemic inflammation might slow or reverse neurodegeneration.

Cognitive impairment in people living with HIV: consensus recommendations for a new approach

Current approaches to classifying cognitive impairment in people living with HIV can overestimate disease burden and lead to ambiguity around disease mechanisms. The 2007 criteria for HIV-associated neurocognitive disorders (HAND), sometimes called the Frascati criteria, can falsely classify over 20% of cognitively healthy individuals as having cognitive impairment. Minimum criteria for HAND are met on the basis of performance on cognitive tests alone, which might not be appropriate for populations with diverse educational and socioeconomic backgrounds. Imprecise phenotyping of cognitive impairment can limit mechanistic research, biomarker discovery and treatment trials. Importantly, overestimation of cognitive impairment carries the risk of creating fear among people living with HIV and worsening stigma and discrimination towards these individuals. To address this issue, we established the International HIV-Cognition Working Group, which is globally representative and involves the community of people living with HIV. We reached consensus on six recommendations towards a new approach for diagnosis and classification of cognitive impairment in people living with HIV, intended to focus discussion and debate going forward. We propose the conceptual separation of HIV-associated brain injury - including active or pretreatment legacy damage - from other causes of brain injury occurring in people living with HIV. We suggest moving away from a quantitative neuropsychological approach towards an emphasis on clinical context. Our recommendations are intended to better represent the changing profile of cognitive impairment in people living with HIV in diverse global settings and to provide a clearer framework of classification for clinical management and research studies.

Correlates of the HIV-associated neurocognitive disorders among adults living with HIV in Dodoma region, central Tanzania: A cross-sectional study

BACKGROUND

HIV-associated neurocognitive disorders (HAND) continue to manifest despite advancements and improved antiretroviral therapy coverage. Neurocognitive impairment is a significant predictor of poor prognosis related to poor antiretroviral therapy adherence and retention in HIV care.

METHODS

This cross-sectional study examined 397 participants attending cared for and treatment at Dodoma Regional Referral Hospital (DRRH) and selected by systematic sampling. The combination of Montreal Cognitive Assessment (MoCA), International HIV Dementia Scale (IHDS), and The Lawton Instrumental Activity of Daily Living (IADL) were used to assess HIV-associated neurocognitive disorders. Factors associated with HAND were determined using univariate and multivariable logistic regression.

RESULTS

Of 397 participants, 234(59.1%) met the criteria for HAND with 231(58.2%) comprising asymptomatic neurocognitive disorder (ANI) or mild neurocognitive disorders (MND), and 3 (0.76%) HIV- associated dementia (HAD). Participants with HAND had significantly poorer performance in each cognitive domain on both MoCA and IHDS. Under multivariable regression, age of 55 years or above with Adjusted Odds Ratio (AOR): 3.5 (95%CI: 1.1, 11.6), p = 0.041 and female gender (AOR): 2.7 (95%CI: 1, 6, 4.5), p<0.001 were significantly associated with HAND. Adherence to antiretroviral therapy AOR: 0.4(95%CI: 0.2, 1.0), p = 0.044, and attaining primary education AOR: 0.3(95%CI: 0.1, 0.8), p = 0.01 or secondary education AOR: 0.1(95%CI: 0.03, 0.2), p<0.001 compared to having no formal education showed good cognitive performance.

CONCLUSION

HIV-associated neurocognitive disorders are common in HIV, especially ANI and MND, are common in HIV infected Tanzanians. Both socio-demographic and clinical variables influence neurocognitive functioning in this population. Screening for mild neurocognitive disorders may be indicated if effective treatment becomes available.

Cerebrospinal fluid biomarkers in SARS-CoV-2 patients with acute neurological syndromes

BACKGROUND AND PURPOSE

Mechanisms underlying acute brain injury in SARS-CoV-2 patients remain poorly understood. A better characterization of such mechanisms remains essential to preventing long-term neurological sequelae. Our present aim was to study a panel of biomarkers of neuroinflammation and neurodegeneration in the cerebrospinal fluid (CSF) of NeuroCOVID patients.

METHODS

We retrospectively collected clinical and CSF biomarkers data from 24 NeuroCOVID adults seen at the University Hospital of Guadeloupe between March and June 2021.

RESULTS

Among 24 NeuroCOVID patients, 71% had encephalopathy and 29% meningoencephalitis. A number of these patients also experienced de novo movement disorder (33%) or stroke (21%). The CSF analysis revealed intrathecal immunoglobulin synthesis in 54% of NeuroCOVID patients (two with a type 2 pattern and 11 with a type 3) and elevated neopterin levels in 75% of them (median 9.1nM, IQR 5.6-22.1). CSF neurofilament light chain (NfL) was also increased compared to a control group of non-COVID-19 patients with psychiatric illnesses (2905ng/L, IQR 1428-7124 versus 1222ng/L, IQR 1049-1566). Total-tau was elevated in the CSF of 24% of patients, whereas protein 14-3-3, generally undetectable, reached intermediate levels in two patients. Finally, CSF Aß1-42 was reduced in 52.4% of patients (median 536ng/L, IQR 432-904) with no change in the Aß1-42/Aß1-40 ratio (0.082, IQR 0.060-0.096).

CONCLUSIONS

We showed an elevation of CSF biomarkers of neuroinflammation in NeuroCOVID patients and a rise of CSF NfL, evocative of neuronal damage. However, longitudinal studies are needed to determine whether NeuroCOVID could evolve into a chronic neurodegenerative condition.

Residual Central Nervous System Immune Activation Is Not Prevented by Antiretroviral Therapy Initiated During Early Chronic HIV Infection

Background

Antiretroviral therapy (ART) initiated during acute infection can potentially impact the central nervous system (CNS) reservoir, but the differential long-term effects of ART initiation during early or late chronic infection are unknown.

Methods

We included neuroasymptomatic people with human immunodeficiency virus (HIV) with suppressive ART initiated during chronic (>1 year since transmission) HIV with archived cerebrospinal fluid (CSF) and serum samples after 1 and/or ≥3 years of ART from a cohort study. CSF and serum neopterin was measured using a commercial immunoassay (BRAHMS, Germany).

Results

In total, 185 people with HIV (median, 79 [interquartile range, 55-128] months on ART) were included. A significant inverse correlation was found between CD4⁺ T-cell count and CSF neopterin only at baseline (r = -0.28, P = .002), but not after 1 (r = -0.026, P = .8) or ≥3 (r -0.063, P = .5) years of ART. No significant differences were seen in CSF or serum neopterin concentrations between different pretreatment CD4⁺ T-cell strata after 1 or ≥3 (median, 6.6) years of ART.

Conclusions

In people with HIV initiating ART during chronic infection, occurrence of residual CNS immune activation was not correlated with pretreatment immune status, even when treatment was initiated at high CD4⁺ T-cell counts, suggesting that the CNS reservoir, once established, is not differentially affected by the timing of ART initiation during chronic infection.

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.

Insights into Molecular Structure of Pterins Suitable for Biomedical Applications

Pterins are an inseparable part of living organisms. Pterins participate in metabolic reactions mostly as tetrahydropterins. Dihydropterins are usually intermediates of these reactions, whereas oxidized pterins can be biomarkers of diseases. In this review, we analyze the available data on the quantum chemistry of unconjugated pterins as well as their photonics. This gives a comprehensive overview about the electronic structure of pterins and offers some benefits for biomedicine applications: (1) one can affect the enzymatic reactions of aromatic amino acid hydroxylases, NO synthases, and alkylglycerol monooxygenase through UV irradiation of H₄pterins since UV provokes electron donor reactions of H₄pterins; (2) the emission properties of H₂pterins and oxidized pterins can be used in fluorescence diagnostics; (3) two-photon absorption (TPA) should be used in such pterin-related infrared therapy because single-photon absorption in the UV range is inefficient and scatters in vivo; (4) one can affect pathogen organisms through TPA excitation of H₄pterin cofactors, such as the molybdenum cofactor, leading to its detachment from proteins and subsequent oxidation; (5) metal nanostructures can be used for the UV-vis, fluorescence, and Raman spectroscopy detection of pterin biomarkers. Therefore, we investigated both the biochemistry and physical chemistry of pterins and suggested some potential prospects for pterin-related biomedicine.

Characterization of Macrophage-Tropic HIV-1 Infection of Central Nervous System Cells and the Influence of Inflammation

HIV-1 infection within the central nervous system (CNS) includes evolution of the virus, damaging inflammatory cascades, and the involvement of multiple cell types; however, our understanding of how Env tropism and inflammation can influence CNS infectivity is incomplete. In this study, we utilize macrophage-tropic and T cell-tropic HIV-1 Env proteins to establish accurate infection profiles for multiple CNS cells under basal and interferon alpha (IFN-α) or lipopolysaccharide (LPS)-induced inflammatory states. We found that macrophage-tropic viruses confer entry advantages in primary myeloid cells, including monocyte-derived macrophage, microglia, and induced pluripotent stem cell (iPSC)-derived microglia. However, neither macrophage-tropic or T cell-tropic HIV-1 Env proteins could mediate infection of astrocytes or neurons, and infection was not potentiated by induction of an inflammatory state in these cells. Additionally, we found that IFN-α and LPS restricted replication in myeloid cells, and IFN-α treatment prior to infection with vesicular stomatitis virus G protein (VSV G) Envs resulted in a conserved antiviral response across all CNS cell types. Further, using RNA sequencing (RNA-seq), we found that only myeloid cells express HIV-1 entry receptor/coreceptor transcripts at a significant level and that these transcripts in select cell types responded only modestly to inflammatory signals. We profiled the transcriptional response of multiple CNS cells to inflammation and found 57 IFN-induced genes that were differentially expressed across all cell types. Taken together, these data focus attention on the cells in the CNS that are truly permissive to HIV-1, further highlight the role of HIV-1 Env evolution in mediating infection in the CNS, and point to limitations in using model cell types versus primary cells to explore features of virus-host interaction. IMPORTANCE The major feature of HIV-1 pathogenesis is the induction of an immunodeficient state in the face of an enhanced state of inflammation. However, for many of those infected, there can be an impact on the central nervous system (CNS) resulting in a wide range of neurocognitive defects. Here, we use a highly sensitive and quantitative assay for viral infectivity to explore primary and model cell types of the brain for their susceptibility to infection using viral entry proteins derived from the CNS. In addition, we examine the ability of an inflammatory state to alter infectivity of these cells. We find that myeloid cells are the only cell types in the CNS that can be infected and that induction of an inflammatory state negatively impacts viral infection across all cell types.

Cerebrospinal Fluid Viral Load Across the Spectrum of Untreated Human Immunodeficiency Virus Type 1 (HIV-1) Infection: A Cross-Sectional Multicenter Study

BACKGROUND

The aim of this large multicenter study was to determine variations in cerebrospinal fluid (CSF) HIV-RNA in different phases of untreated human immunodeficiency virus type 1 (HIV-1) infection and its associations with plasma HIV-RNA and other biomarkers.

METHODS

Treatment naive adults with available CSF HIV-RNA quantification were included and divided into groups representing significant disease phases. Plasma HIV-RNA, CSF white blood cell count (WBC), neopterin, and albumin ratio were included when available.

RESULTS

In total, 1018 patients were included. CSF HIV-RNA was in median (interquartile range [IQR]) 1.03 log10 (0.37-1.86) copies/mL lower than in plasma, and correlated with plasma HIV-RNA (r = 0.44, P < .01), neopterin concentration in CSF (r = 0.49, P < .01) and in serum (r = 0.29, P < .01), CSF WBC (r = 0.34, P < .01) and albumin ratio (r = 0.25, P < .01). CSF HIV-RNA paralleled plasma HIV-RNA in all groups except neuroasymptomatic patients with advanced immunodeficiency (CD4 < 200) and patients with HIV-associated dementia (HAD) or opportunistic central nervous system (CNS) infections. Patients with HAD had the highest CSF HIV-RNA (in median [IQR] 4.73 (3.84-5.35) log10 copies/mL). CSF > plasma discordance was found in 126 of 972 individuals (13%) and varied between groups, from 1% in primary HIV, 11% in neuroasymptomatic groups, up to 30% of patients with HAD.

CONCLUSIONS

Our study confirms previous smaller observations of variations in CSF HIV-RNA in different stages of HIV disease. Overall, CSF HIV-RNA was approximately 1 log10 copies/mL lower in CSF than in plasma, but CSF discordance was found in a substantial minority of subjects, most commonly in patients with HAD, indicating increasing CNS compartmentalization paralleling disease progression.

Advances in Potential Cerebrospinal Fluid Biomarkers for Autoimmune Encephalitis: A Review

Autoimmune encephalitis (AE) is a severe inflammatory disease of the brain. Patients with AE demonstrate amnesia, seizures, and psychosis. Recent studies have identified numerous associated autoantibodies (e.g., against NMDA receptors (NMDARs), LGI1, etc.) involved in the pathogenesis of AE, and the levels of diagnosis and treatment are thus improved dramatically. However, there are drawbacks of clinical diagnosis and treatment based solely on antibody levels, and thus the application of additional biomarkers is urgently needed. Considering the important role of immune mechanisms in AE development, we summarize the relevant research progress in identifying cerebrospinal fluid (CSF) biomarkers with a focus on cytokines/chemokines, demyelination, and nerve damage.

Age-related cognitive impairments in domestic cats naturally infected with feline immunodeficiency virus

BACKGROUND

Age-related dementia has been documented in domestic cats; however, its interaction with naturally occurring feline immunodeficiency virus (FIV) infection has been investigated minimally.

METHODS

Visuospatial working memory (VSWM) and problem-solving (PS) ability were evaluated in FIV-infected (n = 37) and control cats (n = 39) using two cognitive tasks tested serially, which assessed the ability of cats to remember the location of a baited container after a set delay, then evaluated the capability of the cats to manipulate the container to obtain the food within a time limit. Cats were categorized using 7 years of age as a cut-off to determine age-related differences. The relationship between cognitive performance and FIV viral load was investigated using real-time PCR cycle threshold (C_t ) values.

RESULTS

Age significantly affected VSWM and PS ability. Younger cats had better VSWM performance and PS ability compared to older cats with the same FIV status. There was no difference between younger FIV-positive and negative cats in either part of the task. While older FIV-positive cats had significantly worse VSWM than older FIV-negative cats, no differences were found in PS ability. Additionally, C_t values predicted VSWM but not PS ability.

CONCLUSION

Age-related cognitive impairments and FIV infection appear synergetic, causing greater cognitive deficits in older FIV-infected cats.

Viral Antigen and Inflammatory Biomarkers in Cerebrospinal Fluid in Patients With COVID-19 Infection and Neurologic Symptoms Compared With Control Participants Without Infection or Neurologic Symptoms

IMPORTANCE

Neurologic symptoms are common in COVID-19, but the central nervous system (CNS) pathogenesis is unclear, and viral RNA is rarely detected in cerebrospinal fluid (CSF).

OBJECTIVE

To measure viral antigen and inflammatory biomarkers in CSF in relation to neurologic symptoms and disease severity.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study was performed from March 1, 2020, to June 30, 2021, in patients 18 years or older who were admitted to Sahlgrenska University Hospital, Gothenburg, Sweden, with COVID-19. All patients had CSF samples taken because of neurologic symptoms or within a study protocol. Healthy volunteer and prepandemic control groups were included.

EXPOSURE

SARS-CoV-2 infection.

MAIN OUTCOMES AND MEASURES

Outcomes included CSF SARS-CoV-2 nucleocapsid antigen (N-Ag) using an ultrasensitive antigen capture immunoassay platform and CSF biomarkers of immune activation (neopterin, β2-microglobulin, and cytokines) and neuronal injury (neurofilament light protein [NfL]).

RESULTS

Forty-four patients (median [IQR] age, 57 [48-69] years; 30 [68%] male; 26 with moderate COVID-19 and 18 with severe COVID-19 based on the World Health Organization Clinical Progression Scale), 10 healthy controls (median [IQR] age, 58 [54-60] years; 5 [50%] male), and 41 patient controls (COVID negative without evidence of CNS infection) (median [IQR] age, 59 [49-70] years; 19 [46%] male) were included in the study. Twenty-one patients were neuroasymptomatic and 23 were neurosymptomatic (21 with encephalopathy). In 31 of 35 patients for whom data were available (89%), CSF N-Ag was detected; viral RNA test results were negative in all. Nucleocapsid antigen was significantly correlated with CSF neopterin (r = 0.38; P = .03) and interferon γ (r = 0.42; P = .01). No differences in CSF N-Ag concentrations were found between patient groups. Patients had markedly increased CSF neopterin, β2-microglobulin, interleukin (IL) 2, IL-6, IL-10, and tumor necrosis factor α compared with controls. Neurosymptomatic patients had significantly higher median (IQR) CSF interferon γ (86 [47-172] vs 21 [17-81] fg/mL; P = .03) and had a significantly higher inflammatory biomarker profile using principal component analysis compared with neuroasymptomatic patients (0.54; 95% CI, 0.03-1.05; P = .04). Age-adjusted median (IQR) CSF NfL concentrations were higher in patients compared with controls (960 [673-1307] vs 618 [489-786] ng/L; P = .002). No differences were seen in any CSF biomarkers in moderate compared with severe disease.

CONCLUSIONS AND RELEVANCE

In this study of Swedish adults with COVID-19 infection and neurologic symptoms, compared with control participants, viral antigen was detectable in CSF and correlated with CNS immune activation. Patients with COVID-19 had signs of neuroaxonal injury, and neurosymptomatic patients had a more marked inflammatory profile that could not be attributed to differences in COVID-19 severity. These results highlight the clinical relevance of neurologic symptoms and suggest that viral components can contribute to CNS immune responses without direct viral invasion.

CSF neopterin and beta-2-microglobulin as inflammation biomarkers in newborns with hypoxic-ischemic encephalopathy

BACKGROUND

Inflammation plays a crucial role in the pathogenesis of hypoxic-ischemic encephalopathy (HIE). The aim of this study was to measure inflammation in HIE through an analysis of CSF neopterin and β2-microglobulin and to study the association with brain injury as shown by MRI findings and neurodevelopmental outcomes.

METHODS

CSF biomarkers were measured in study patients at 12 and 72 h. Brain injury was evaluated by MRI, and neurodevelopmental outcomes were assessed at 2-3 years of life. An adverse outcome was defined as the presence of motor or cognitive impairment.

RESULTS

Sixty-nine HIE infants were included. Median values of neopterin and β2-microglobulin paralleled the severity of HIE. Adverse outcomes were associated with early neopterin and β2-microglobulin values, late neopterin values, and the neopterin percentage change between the two samples. A cutoff value of 75% neopterin change predicted adverse outcomes with a specificity of 0.9 and a sensitivity of 0.75.

CONCLUSIONS

CSF neopterin and β2-microglobulin are elevated in HIE, indicating the activation of inflammation processes. Infants with adverse neurodevelopmental outcomes show higher levels of CSF neopterin and β2-microglobulin. The evolution of neopterin levels provides a better predictive capacity than a single determination.

IMPACT

Brain inflammation in newborns with HIE could be measurable through the analysis of CSF neopterin and β2-microglobulin, both of which are associated with neurodevelopmental outcomes. Our study introduces two inflammatory biomarkers for infants with HIE that seem to show a more stable profile and are easier to interpret than cytokines. CSF neopterin and β2-m may become clinical tools to monitor inflammation in HIE and might eventually be helpful in measuring the response to emerging therapies.

The importance of neopterin in COVID-19: The prognostic value and relation with the disease severity

Coronavirus Disease 2019 [COVID-19], caused by severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2], has rapidly evolved into a global health emergency. Neopterin [NPT], produced by macrophages when stimulated with interferon [IFN-]gamma, is an essential cytokine in the antiviral immune response. NPT has been used as a marker for the early assessment of disease severity in different diseases. The leading cause of NPT production is the pro-inflammatory cytokine IFN-. Macrophage activation has also been revealed to be linked with disease severity in SARS-CoV-2 patients. We demonstrate the importance of NPT in the pathogenesis of SARS-CoV-2 and suggest that targeting NPT in SARS-CoV-2 infection may be critical in the early prediction of disease progression and provision of timely management of infected individuals.

Elevated Cerebrospinal Fluid Anti-CD4 Autoantibody Levels in HIV Associate with Neuroinflammation

The mechanisms of persistent central nervous system (CNS) inflammation in people with HIV (PWH) despite effective antiretroviral therapy (ART) are not fully understood. We have recently shown that plasma anti-CD4 IgGs contribute to poor CD4⁺ T cell recovery during suppressive ART via antibody-mediated cytotoxicity (ADCC) against CD4⁺ T cells, and that plasma anti-CD4 IgG levels are associated with worse cognitive performance and specific brain area atrophy. However, the role of anti-CD4 IgGs in neuroinflammation remains unclear. In the current study, plasma and cerebrospinal fluid (CSF) samples from 31 ART-naive and 26 treated, virologically suppressed PWH, along with 16 HIV-seronegative controls, were evaluated for CSF levels of anti-CD4 IgG, white blood cell (WBC) counts, soluble biomarkers of neuroinflammation, and neurofilament light chain (NfL). We found that 37% of the PWH exhibited elevated CSF anti-CD4 IgG levels, but few or none of the PWH were observed with elevated CSF anti-CD4 IgM, anti-CD8 IgG, or anti-double-strand DNA IgG. CSF anti-CD4 IgG levels in PWH were directly correlated with neuroinflammation (WBC counts, neopterin, and markers of myeloid cell activation), but not with CSF NfL levels. Using cells from one immune nonresponder to ART, we generated a pathogenic anti-CD4 monoclonal IgG (JF19) presenting with ADCC activity; JF19 induced the production of soluble CD14 (sCD14) and interleukin-8 (IL-8) in human primary monocyte-derived macrophages via CD4 binding in vitro. This study demonstrates for the first time that elevated CSF anti-CD4 IgG levels present in a subgroup of PWH which may play a role in neuroinflammation in HIV.

IMPORTANCE This study reports that an autoantibody presents in the CNS of HIV patients and that its levels in the CSF correlate with some markers of neuroinflammation.

Epigenome-wide epidemiologic studies of human immunodeficiency virus infection, treatment, and disease progression

Despite significant advances in the treatment and care of people with HIV (PWH), several challenges remain in our understanding of disease pathogenesis to improve patient care. HIV infection can modify the host epigenome and as such can impact disease progression, as well as the molecular processes driving non-AIDS comorbidities in PWH. Epigenetic epidemiologic studies including epigenome-wide association studies (EWAS) offer a unique set of tools to expand our understanding of HIV disease and to identify novel strategies applicable to treatment and diagnosis in this patient population. In this review, we summarize the current state of knowledge from epigenetic epidemiologic studies of PWH, identify the main challenges of this approach, and highlight future directions for the field. Emerging epigenetic epidemiologic studies of PWH can expand our understanding of HIV infection and health outcomes, improve scientific validity through collaboration and replication, and increase the coverage of diverse populations affected by the global HIV pandemic. Through this review, we hope to highlight the potential of EWAS as a tool for HIV research and to engage more investigators to explore its application to important research questions.

Effect of antiretroviral treatment on blood-brain barrier integrity in HIV-1 infection

Background

Blood-brain barrier (BBB) injury is prevalent in patients with HIV-associated dementia (HAD) and is a frequent feature of HIV encephalitis. Signs of BBB damage are also sometimes found in neuroasymptomatic HIV-infected individuals without antiretroviral therapy (ART). The aim of this study was to investigate the integrity of the BBB before and after initiation of ART in both neuroasymptomatic HIV infection and in patients with HAD.

Methods

We determined BBB integrity by measuring cerebrospinal fluid (CSF)/plasma albumin ratios in archived CSF samples prior to and after initiation of ART in longitudinally-followed neuroasymptomatic HIV-1-infected individuals and patients with HAD. We also analyzed HIV RNA in blood and CSF, IgG Index, CSF WBC counts, and CSF concentrations of β2-micoglobulin, neopterin, and neurofilament light chain protein (NfL).

Results

We included 159 HIV-infected participants; 82 neuroasymptomatic individuals and 77 with HAD. All neuroasymptomatic individuals (82/82), and 10/77 individuals with HAD, were longitudinally followed with a median (interquartile range, IQR) follow-up of 758 (230–1752) days for the neuroasymptomatic individuals, and a median (IQR) follow-up of 241 (50–994) days for the individuals with HAD. Twelve percent (10/82) of the neuroasymptomatic individuals and 80% (8/10) of the longitudinally-followed individuals with HAD had elevated albumin ratios at baseline. At the last follow-up, 9% (7/82) of the neuroasymptomatic individuals and 20% (2/10) of the individuals with HAD had elevated albumin ratios. ART significantly decreased albumin ratios in both neuroasymptomatic individuals and in patients with HAD.

Conclusion

These findings indicate that ART improves and possibly normalizes BBB integrity in both neuroasymptomatic HIV-infected individuals and in patients with HAD.

Soluble Biomarkers of Cognition and Depression in Adults with HIV Infection in the Combination Therapy Era

PURPOSE OF REVIEW

Cognitive impairment and depression continue to be common among people with HIV (PWH) in the combination antiretroviral therapy (ART) era. A better understanding of the biological mechanisms that may underpin these disorders is needed. The purpose of this review is to describe published findings on soluble biomarkers from blood and cerebrospinal fluid (CSF) that have been associated with either cognition or depression among PWH in the setting of ART.

RECENT FINDINGS

Several biomarkers, including those that reflect viral persistence, monocyte/macrophage activation, and other processes, are associated with cognition and depressive symptoms. Some but not all results have been consistent across multiple studies. More research has been published on biomarkers of cognition relative to biomarkers of depression (particularly from CSF). More studies are needed that investigate multiple biomarkers to understand the role of distinct but additive pathways in these disorders and to guide the development of new therapies.

Increased immune activation and signs of neuronal injury in HIV-negative people on preexposure prophylaxis

OBJECTIVE

Persistent immune activation in the central nervous system and systemically are common in people living with HIV (PLHIV) despite antiretroviral therapy. It is not known whether this is generated by HIV replication or by other components such as coinfections and lifestyle-related factors.

DESIGN

The aim of this study was to determine the importance of different factors; it is crucial to find well matched HIV-negative controls. In this context, HIV-negative persons on preexposure prophylaxis (PrEP) may constitute a suitable control group to PLHIV with similar lifestyle-related factors.

METHODS

Cerebrospinal fluid (CSF) and blood were collected from 40 HIV-negative persons on PrEP and 20 controls without PrEP. Biomarkers of immune activation, blood--brain barrier (BBB) integrity and neuronal injury were analysed.

RESULTS

CSF and serum β2-microglobulin, serum neopterin and CSF neurofilament light protein were higher in persons on PrEP compared with controls. Furthermore, persons on PrEP had higher CSF/plasma albumin ratio, and matrix metalloproteinase-3 concentrations, indicating BBB dysfunction. Of persons on PrEP, 90% were cytomegalovirus (CMV)-positive compared to 65% of the controls. CMV-positive individuals as a group had higher levels of serum β2-microglobulin than CMV-negative individuals (P < 0.05). Drug users had higher serum β2-microglobulin compared to nonusers (P < 0.01).

CONCLUSION

HIV-negative persons on PrEP had higher levels of biomarkers for immune activation, BBB impairment and neuronal injury, compared with volunteers without PrEP. Moreover, serum β2-microglobulin was higher in CMV-positive than in CMV-negative individuals and in drug users compared with nonusers. These findings are important to consider when analysing immune activation and CNS injury in PLHIV, and emphasize the importance of appropriate controls.

Cerebrospinal fluid metabolomics: detection of neuroinflammation in human central nervous system disease

The high morbidity and mortality of neuroinflammatory diseases drives significant interest in understanding the underlying mechanisms involved in the innate and adaptive immune response of the central nervous system (CNS). Diagnostic biomarkers are important to define treatable neuroinflammation. Metabolomics is a rapidly evolving research area offering novel insights into metabolic pathways, and elucidation of reliable metabolites as biomarkers for diseases. This review focuses on the emerging literature regarding the detection of neuroinflammation using cerebrospinal fluid (CSF) metabolomics in human cohort studies. Studies of classic neuroinflammatory disorders such as encephalitis, CNS infection and multiple sclerosis confirm the utility of CSF metabolomics. Additionally, studies in neurodegeneration and neuropsychiatry support the emerging potential of CSF metabolomics to detect neuroinflammation in common CNS diseases such as Alzheimer's disease and depression. We demonstrate metabolites in the tryptophan-kynurenine pathway, nitric oxide pathway, neopterin and major lipid species show moderately consistent ability to differentiate patients with neuroinflammation from controls. Integration of CSF metabolomics into clinical practice is warranted to improve recognition and treatment of neuroinflammation.

Neurologic Complications of Human Immunodeficiency Virus

PURPOSE OF REVIEW

This article reviews the neurologic complications associated with human immunodeficiency virus (HIV) infection.

RECENT FINDINGS

Neurologic complications of HIV may be caused by direct virally mediated pathology, immune-mediated phenomena in response to viral infection, or opportunistic infections secondary to depletion of lymphocytes. These neurologic disorders may be influenced by the degree of immunosuppression (ie, CD4+ T-cell lymphocyte count) and stage of infection (early versus late), as well as use of antiretroviral therapy, and may manifest as a variety of central and peripheral neurologic syndromes, including the more commonly encountered HIV-associated cognitive disorders and length-dependent sensorimotor polyneuropathy, respectively. Immune dysregulation underlies the majority of these neurologic phenomena, as well as other HIV-associated conditions including immune reconstitution inflammatory syndrome (IRIS), CD8 lymphocytosis, and potentially the development of compartmentalized infection within the CSF, also referred to as CSF escape.

SUMMARY

This article reviews a spectrum of clinical syndromes and related neuropathologic states associated with HIV infection.

Neurochemical biomarkers to study CNS effects of COVID-19: a narrative review and synthesis

Neurological symptoms are frequently reported in patients suffering from COVID‐19. Common CNS‐related symptoms include anosmia, caused by viral interaction with either neurons or supporting cells in nasal olfactory tissues. Diffuse encephalopathy is the most common sign of CNS dysfunction, which likely results from the CNS consequences of the systemic inflammatory syndrome associated with severe COVID‐19. Additionally, microvascular injuries and thromboembolic events likely contribute to the neurologic impact of acute COVID‐19. These observations are supported by evidence of CNS immune activation in cerebrospinal fluid (CSF) and in autopsy tissue, along with the detection of microvascular injuries in both pathological and neuroimaging studies. The frequent occurrence of thromboembolic events in patients with COVID‐19 has generated different hypotheses, among which viral interaction with perivascular cells is particularly attractive, yet unproven. A distinguishing feature of CSF findings in SARS‐CoV‐2 infection is that clinical signs characteristic of neurotropic viral infections (CSF pleocytosis and blood–brain barrier injury) are mild or absent. Moreover, virus detection in CSF is rare and often of uncertain significance. In this review, we provide an overview of the neurological impact that occurs in the acute phase of COVID‐19, and the role of CSF biomarkers in the clinical management and research to better treat and understand the disease. In addition to aiding as diagnostic and prognostic tools during acute infection, the use of comprehensive and well‐characterized CSF and blood biomarkers will be vital in understanding the potential impact on the CNS in the rapidly increasing number of individuals recovering from COVID‐19.

Compartmentalization of cerebrospinal fluid inflammation across the spectrum of untreated HIV-1 infection, central nervous system injury and viral suppression

OBJECTIVE

To characterize the evolution of central nervous system (CNS) inflammation in HIV-1 infection applying a panel of cerebrospinal fluid (CSF) inflammatory biomarkers to grouped subjects representing a broad spectrum of systemic HIV-1 immune suppression, CNS injury and viral control.

METHODS

This is a cross-sectional analysis of archived CSF and blood samples, assessing concentrations of 10 functionally diverse soluble inflammatory biomarkers by immunoassays in 143 HIV-1-infected subjects divided into 8 groups: untreated primary HIV-1 infection (PHI); four untreated groups defined by their blood CD4+ T lymphocyte counts; untreated patients presenting with subacute HIV-associated dementia (HAD); antiretroviral-treated subjects with ≥1 years of plasma viral suppression; and untreated elite controllers. Twenty HIV-1-uninfected controls were included for comparison. Background biomarkers included blood CD4+ and CD8+ T lymphocytes, CSF and blood HIV-1 RNA, CSF white blood cell (WBC) count, CSF/blood albumin ratio, CSF neurofilament light chain (NfL), and CSF t-tau.

FINDINGS

HIV-1 infection was associated with a broad compartmentalized CSF inflammatory response that developed early in its course and changed with systemic disease progression, development of neurological injury, and viral suppression. CSF inflammation in untreated individuals without overt HAD exhibited at least two overall patterns of inflammation as blood CD4+ T lymphocytes decreased: one that peaked at 200-350 blood CD4+ T cells/μL and associated with lymphocytic CSF inflammation and HIV-1 RNA concentrations; and a second that steadily increased through the full range of CD4+ T cell decline and associated with macrophage responses and increasing CNS injury. Subacute HAD was distinguished by a third inflammatory profile with increased blood-brain barrier permeability and robust combined lymphocytic and macrophage CSF inflammation. Suppression of CSF and blood HIV-1 infections by antiretroviral treatment and elite viral control were associated with reduced CSF inflammation, though not fully to levels found in HIV-1 seronegative controls.

Functional changes of immune cells: signal of immune tolerance of the ectopic lesions in endometriosis?

RESEARCH QUESTION

What is the potential role of immune cells and their inflammatory cytokines in the pathogenesis, development and establishment of endometriosis?

DESIGN

Peritoneal fluid from 59 women (43 with endometriosis and 16 controls) who had undergone laparoscopic surgery was analysed. Changes in the population of innate and adaptive immune cells, cytokines, chemokines and growth factor expression were measured by flow cytometry, Luminex Technology and enzyme-linked immunosorbent assay.

RESULTS

No differences were found in the frequencies of the innate and adaptive immune cells between women with and without endometriosis. In the peritoneal fluid of women with endometriosis, IL-1β, IL-1RN, IL-2, IL-4, IL-8, IL-10, IL-12 (p70), IL-17α, FGF2, G-CSF, MCP-1, MIP-1α and TNF-α were significantly increased compared with controls. A correlation between IL-2, MCP-1, MIP-1α, TNF-α and the severity of endometriosis was observed. The concentration of neopterin, a possible biomarker for this disease, was increased in women with endometriosis compared with controls.

CONCLUSIONS

The functional activity of immune cells seemed to be reduced despite their numbers remaining unchanged. The data indicate that a shift of T_H cytokine profile occurs, which increases the T_H1-T_H2 ratio. This is driven by the increased levels of the cytokines (TNF-α and IL-2) in women with severe endometriosis.

Cognitive and Neuronal Link With Inflammation: A Longitudinal Study in People With and Without HIV Infection

BACKGROUND

Across many settings, lack of virologic control remains common in people with HIV (PWH) because of late presentation and lack of retention in care. This contributes to neuronal damage and neurocognitive impairment, which remains prevalent. More evidence is needed to understand these outcomes in both PWH and people without HIV (PWOH).

METHODS

We recruited PWH initiating antiretroviral therapy and PWOH at 2 sites in the United States. One hundred eight adults were enrolled (56 PWOH and 52 PWH), most of whom had a second assessment at least 24 weeks later (193 total assessments). Tumor necrosis factor alpha, monocyte chemotactic protein-1 (MCP-1), neopterin, soluble CD14, and neurofilament light chain protein (NFL) were measured in plasma and cerebrospinal fluid (CSF). Using multivariate models including Bayesian model averaging, we analyzed factors associated with global neuropsychological performance (NPT-9) and CSF NFL at baseline and over time.

RESULTS

At baseline, higher CSF MCP-1 and plasma sCD14 were associated with worse NPT-9 in PWH, while CSF HIV RNA decrease was the only marker associated with improved NPT-9 over time. Among PWH, higher CSF neopterin was most closely associated with higher NFL. Among PWOH, higher CSF MCP-1 was most closely associated with higher NFL. After antiretroviral therapy initiation, decrease in CSF MCP-1 was most closely associated with NFL decrease.

CONCLUSION

Monocyte-associated CSF biomarkers are highly associated with neuronal damage in both PWH and PWOH. More research is needed to evaluate whether therapies targeting monocyte-associated inflammation may ameliorate HIV-associated neurobehavioral diseases.

Chronic inflammation mediates brain injury in HIV infection: relevance for cure strategies

PURPOSE OF REVIEW

Chronic inflammation is a major component of HIV infection, the effects of which can be devastating in the central nervous system (CNS). Protecting the brain is, therefore, critical as efforts proceed to cure HIV infection by reactivating latent viral reservoirs and driving immune responses. We review the clinical presentation and pathology findings of inflammatory processes in the CNS in patients managed with ART and the drivers of these processes.

RECENT FINDINGS

Chronic inflammation is associated with increased mortality and morbidity and HIV infection increases the risk for chronic diseases, especially cognitive impairment. Latent viral reservoirs, including microglia and tissue macrophages, contribute to inflammation in the CNS. Inflammation is generated and maintained through residual viral replication, dysregulation of infected cells, continuously produced viral proteins and positive feedback loops of chronic inflammation. Novel therapeutics and lifestyle changes may help to protect the CNS from immune-mediated damage.

SUMMARY

As therapies are developed to cure HIV, it is important to protect the CNS from additional immune-mediated damage. Adjunctive therapies to restore glial function, reduce neuroinflammation and systemic inflammation, and inhibit expression of viral proteins are needed.

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.

Insights into the biomarkers of viral encephalitis from clinical patients

BACKGROUND

biomarkers can be helpful in identifying patients who may profit by explicit treatments or evaluating the reaction to the treatment of specific disease. Finding unique biomarkers in the process of disease could help clinicians in identifying serious disease in the early stage, so as to improve prognosis.

OBJECTIVE

these investigations, nonetheless, have made constrained progress. Numerous infections are known to cause intense viral encephalitis (VE) in people which can cause a variable level of meningeal just as parenchymal aggravation. Initial clinical manifestations in most encephalitis are nonspecific, resembling a viral-like illness. However, with disease progression, symptoms can become quite severe and fatal, including prominent cranial hypertension, cognitive problems, cerebral hernia and respiratory failure. Forwards: the clinical and research center discoveries in huge numbers of those viral issues are to a great extent comparable and in this way increasingly explicit biomarkers for indicative and prognostic intentions are justified. These biomarkers are progressively significant in the acknowledgment and treatment of the viral central nervous system (CNS) issue.

CONCLUSION

Clinical manifestations have been the indicative approaches for analysis of viral encephalitis. Lots of studies have been endeavored to distinguish progressively objective laboratory-based quantitative CSF biomarkers for VE.

Cerebrospinal fluid neopterin as a biomarker of neuroinflammatory diseases

The elevation of neopterin in cerebrospinal fluid (CSF) has been reported in several neuroinflammatory disorders. However, it is not expected that neopterin alone can discriminate among different neuroinflammatory etiologies. We conducted an observational retrospective and case-control study to analyze the CSF biomarkers neopterin, total proteins, and leukocytes in a large cohort of pediatric patients with neuroinflammatory disorders. CSF samples from 277 subjects were included and classified into four groups: Viral meningoencephalitis, bacterial meningitis, acquired immune-mediated disorders, and patients with no-immune diseases (control group). CSF neopterin was analyzed with high-performance liquid chromatography. Microbiological diagnosis included bacterial CSF cultures and several specific real-time polymerase chain reactions. Molecular testing for multiple respiratory pathogens was also included. Antibodies against neuronal and glial proteins were tested. Canonical discriminant analysis of the three biomarkers was conducted to establish the best discriminant functions for the classification of the different clinical groups. Model validation was done by biomarker analyses in a new cohort of 95 pediatric patients. CSF neopterin displayed the highest values in the viral and bacterial infection groups. By applying canonical discriminant analysis, it was possible to classify the patients into the different groups. Validation analyses displayed good results for neuropediatric patients with no-immune diseases and for viral meningitis patients, followed by the other groups. This study provides initial evidence of a more efficient approach to promote the timely classification of patients with viral and bacterial infections and acquired autoimmune disorders. Through canonical equations, we have validated a new tool that aids in the early and differential diagnosis of these neuroinflammatory conditions.

Enhancing care for people living with HIV: current and future monitoring approaches

INTRODUCTION

Antiretroviral therapy (ART) is the most significant advance in the medical management of HIV-1 infection. Given the fact that HIV cannot be eradicated from the body, ART has to be indefinitely maintained. New approaches need to be defined for monitoring HIV-infected individuals (PLWHIV), including clinical, virologic, immunological parameters and also ways to collect individual points of view and quality of life.

AREAS COVERED

We discuss which tests may be used to improve the management of PLWHIV and respond to a comprehensive health demand.

EXPERT OPINION

Viral load and CD4 counts are well-validated outcome measures and we still need them, but they do not completely depict the health status of PLWHIV. We need to better understand and to apply to clinical practice what happens in sanctuaries, what is the role of HIV DNA, what is the meaning of low-level viremia. Most of these questions do not yet have a definitive response. Further, we need to understand how to modify these variables in order to improve outcomes.Similar points may be raised for immunological measures and for tests exploring the tolerability of drugs. The goal must be the evolution from a viro/immunologic-based to a comprehensive quality-of-health-based evaluation of PLWHIV.

Biomarkers of Activation and Inflammation to Track Disparity in Chronological and Physiological Age of People Living With HIV on Combination Antiretroviral Therapy

With advancement, prompt use, and increasing accessibility of antiretroviral therapy, people with HIV are living longer and have comparable lifespans to those negative for HIV. However, people living with HIV experience tradeoffs with quality of life often developing age-associated co-morbid conditions such as cancers, cardiovascular diseases, or neurodegeneration due to chronic immune activation and inflammation. This creates a discrepancy in chronological and physiological age, with HIV-infected individuals appearing older than they are, and in some contexts ART-associated toxicity exacerbates this gap. The complexity of the accelerated aging process in the context of HIV-infection highlights the need for greater understanding of biomarkers involved. In this review, we discuss markers identified in different anatomical sites of the body including periphery, brain, and gut, as well as markers related to DNA that may serve as reliable predictors of accelerated aging in HIV infected individuals as it relates to inflammatory state and immune activation.

Cognitive disorders in people living with HIV

High rates of cognitive disorders in antiretroviral-treated people living with HIV have been described worldwide. The exact prevalence of such cognitive disorders is determined by the definitions used, and the presence of these cognitive disorders significantly impacts the overall wellbeing of people with HIV. With the cohort of people with HIV becoming increasingly older, and having high rates of comorbidities and concomitant medication use, rates of cognitive disorders are likely to increase. Conversely, interventions are being sought to reduce the size of the latent HIV reservoir. If successful, such interventions are likely to also reduce the HIV reservoir in the brain compartment, which could result in improvements in cognitive function and reduced rates of impairment.

Herpes zoster in HIV-1 infection: The role of CSF pleocytosis in secondary CSF escape and discordance

HIV cerebrospinal fluid (CSF) escape is defined by a concentration of HIV-1 RNA in CSF above the lower limit of quantification of the employed assay and equal to or greater than the plasma HIV-1 RNA level in the presence of treatment-related plasma viral suppression, while CSF discordance is similarly defined by equal or higher CSF than plasma HIV-1 RNA in untreated individuals. During secondary CSF escape or discordance, disproportionate CSF HIV-1 RNA develops in relation to another infection in addition to HIV-1. We performed a retrospective review of people living with HIV receiving clinical care at Sahlgrenska Infectious Diseases Clinic in Gothenburg, Sweden who developed uncomplicated herpes zoster (HZ) and underwent a research lumbar puncture (LP) within the ensuing 150 days. Based on treatment status and the relationship between CSF and plasma HIV-1 RNA concentrations, they were divided into 4 groups: i) antiretroviral treated with CSF escape (N = 4), ii) treated without CSF escape (N = 5), iii) untreated with CSF discordance (N = 8), and iv) untreated without CSF discordance (N = 8). We augmented these with two additional cases of secondary CSF escape related to neuroborreliosis and HSV-2 encephalitis and analyzed these two non-HZ cases for factors contributing to CSF HIV-1 RNA concentrations. HIV-1 CSF escape and discordance were associated with higher CSF white blood cell (WBC) counts than their non-escape (P = 0.0087) and non-discordant (P = 0.0017) counterparts, and the CSF WBC counts correlated with the CSF HIV-1 RNA levels in both the treated (P = 0.0047) and untreated (P = 0.002) group pairs. Moreover, the CSF WBC counts correlated with the CSF:plasma HIV-1 RNA ratios of the entire group of 27 subjects (P = <0.0001) indicating a strong effect of the CSF WBC count on the relation of the CSF to plasma HIV-1 RNA concentrations across the entire sample set. The inflammatory response to HZ and its augmenting effect on CSF HIV-1 RNA was found up to 5 months after the HZ outbreak in the cross-sectional sample and, was present for one year after HZ in one individual followed longitudinally. We suggest that HZ provides a ‘model’ of secondary CSF escape and discordance. Likely, the inflammatory response to HZ pathology provoked local HIV-1 production by enhanced trafficking or activation of HIV-1-infected CD4+ T lymphocytes. Whereas treatment and other systemic factors determined the plasma HIV-1 RNA concentrations, in this setting the CSF WBC counts established the relation of the CSF HIV-1 RNA levels to this plasma set-point.

Potential pharmacological approaches for the treatment of HIV-1 associated neurocognitive disorders

HIV associated neurocognitive disorders (HAND) are the spectrum of cognitive impairments present in patients infected with human immunodeficiency virus type 1 (HIV-1). The number of patients affected with HAND ranges from 30 to 50% of HIV infected individuals and although the development of combinational antiretroviral therapy (cART) has improved longevity, HAND continues to pose a significant clinical problem as the current standard of care does not alleviate or prevent HAND symptoms. At present, the pathological mechanisms contributing to HAND remain unclear, but evidence suggests that it stems from neuronal injury due to chronic release of neurotoxins, chemokines, viral proteins, and proinflammatory cytokines secreted by HIV-1 activated microglia, macrophages and astrocytes in the central nervous system (CNS). Furthermore, the blood-brain barrier (BBB) not only serves as a route for HIV-1 entry into the brain but also prevents cART therapy from reaching HIV-1 brain reservoirs, and therefore could play an important role in HAND. The goal of this review is to discuss the current data on the epidemiology, pathology and research models of HAND as well as address the potential pharmacological treatment approaches that are being investigated.

Cerebrospinal fluid soluble CD30 elevation despite suppressive antiretroviral therapy in individuals living with HIV-1

OBJECTIVES

The aim of this study was to assess soluble CD30 (sCD30), a protein that colocalises with HIV-1 RNA and DNA in lymphoid cells and tissues, in cerebrospinal fluid (CSF) as a marker of HIV-1 infection in the central nervous system (CNS).

METHODS

This was a cross-sectional study using archived samples from two clinical cohorts. Soluble CD30 concentrations were measured in paired CSF and plasma from untreated viraemic individuals (n=52), individuals on suppressive antiretroviral therapy (ART) (n=33), HIV-1 controllers (n=10), participants with CSF HIV-1 'escape' (n=11) and controls without HIV-1 infection (n=16). Nonparametric tests were used to compare levels across groups and evaluate correlations with HIV-1 RNA, CSF neurofilament light chain protein (NFL) and neopterin.

RESULTS

Compared with controls (median 30 ng/mL, interquartile range [IRQ] 23-50), plasma sCD30 levels were elevated in viraemic participants (75 ng/mL, 52-116; P<0.001), but not in those on suppressive ART (38 ng/mL, 32-62). In contrast, CSF sCD30 levels were elevated in ART-suppressed individuals (34 ng/mL, 19-46; P=0.001) and in those with CSF 'escape' (33 ng/mL, 27-40; P=0.004) compared with controls (18 ng/mL, 11-23), but not in untreated viraemic individuals. No association was observed between CSF sCD30 and plasma HIV-1 RNA, concurrent or nadir CD4+ T cell count, duration of infection or plasma sCD30. CSF sCD30 correlated with CSF NFL (r=0.34, P=0.001).

CONCLUSIONS

In contrast to plasma, sCD30 levels are elevated in the CSF of individuals with HIV-1 infection who are on suppressive ART. Elevated levels of sCD30 in the CSF may be an indicator of persistent CNS HIV-1 infection, although the mechanism underlying this elevation warrants further investigation.

Plasma inflammatory biomarkers link to diffusion tensor imaging metrics in virally suppressed HIV-infected individuals

OBJECTIVE

Inflammation may contribute to brain white matter health in people living with HIV who report cognitive symptoms despite adherence to combination antiretroviral therapy and viral suppression. We explored relationships between diffusion tensor imaging (DTI) metrics of white matter, plasma biomarkers of immune activation, and cognitive function in the HIV-infected population.

DESIGN

Retrospective study of older adults living with HIV who are combination antiretroviral therapy adherent, virally suppressed, and self-report cognitive symptoms.

METHODS

MRI, blood draws, and standardized neuropsychological test scores were collected from HIV-infected individuals. DTI metrics (fractional anisotropy, mean diffusivity, radial diffusivity, axial diffusivity) and plasma biomarkers (soluble CD163, soluble CD14, neopterin, IFN γ-induced protein 10, monocyte chemoattractant protein 1) were quantified. Statistical analysis explored associations between biomarker levels or neuropsychological test scores and DTI metrics using region of interest analyses and a voxelwise approach.

RESULTS

A total of 43 participants with median (interquartile range) age of 64 (62-66 years), CD4 cell count of 600 (400-760 cell/μl) who were all virally suppressed (<100 copies/ml) were selected. Higher levels of monocyte chemoattractant protein 1 associated with lower fractional anisotropy and higher mean diffusivity (P < 0.05) across white matter tracts including corpus callosum, corona radiata, and superior longitudinal fasciculus. Higher neopterin associated with higher mean diffusivity in the genu of corpus callosum, and higher soluble CD14 associated with lower fractional anisotropy in the bilateral superior corona radiata (P < 0.05). Worse global performance and speed domain scores associated with higher mean diffusivity and lower fractional anisotropy, and worse executive domain scores associated with lower fractional anisotropy (P < 0.05).

CONCLUSION

Elevated inflammatory plasma biomarkers link to white matter abnormalities among virally suppressed individuals. DTI abnormalities associate to cognitive performance. We conclude that inflammatory processes impact clinically relevant brain health indices despite viral suppression.

Cerebrospinal Fluid Concentrations of the Synaptic Marker Neurogranin in Neuro-HIV and Other Neurological Disorders

Purpose of Review

The aim of this study was to examine the synaptic biomarker neurogranin in cerebrospinal fluid (CSF) in different stages of HIV infection and in relation to what is known about CSF neurogranin in other neurodegenerative diseases.

Recent Findings

CSF concentrations of neurogranin are increased in Alzheimer’s disease, but not in other neurodegenerative disorder such as Parkinson’s disease, frontotemporal dementia, and Lewy body dementia. Adults with HIV-associated dementia have been found to have decreased levels of neurogranin in the frontal cortex, which at least to some extent, may be mediated by the proinflammatory cytokines IL-1β and IL-8.

Summary

CSF neurogranin concentrations were in the same range for all groups of HIV-infected individuals and uninfected controls. This either indicates that synaptic injury is not an important part of HIV neuropathogenesis or that CSF neurogranin is not sensitive to the type of synaptic impairment present in HIV-associated neurocognitive disorders.