Clinical factors related to brain structure in HIV: the CHARTER study

The prefrontal cortex, but not the medial temporal lobe, is associated with episodic memory in middle-aged persons with HIV

OBJECTIVE

Identifying persons with HIV (PWH) at increased risk for Alzheimer's disease (AD) is complicated because memory deficits are common in HIV-associated neurocognitive disorders (HAND) and a defining feature of amnestic mild cognitive impairment (aMCI; a precursor to AD). Recognition memory deficits may be useful in differentiating these etiologies. Therefore, neuroimaging correlates of different memory deficits (i.e., recall, recognition) and their longitudinal trajectories in PWH were examined.

DESIGN

We examined 92 PWH from the CHARTER Program, ages 45-68, without severe comorbid conditions, who received baseline structural MRI and baseline and longitudinal neuropsychological testing. Linear and logistic regression examined neuroanatomical correlates (i.e., cortical thickness and volumes of regions associated with HAND and/or AD) of memory performance at baseline and multilevel modeling examined neuroanatomical correlates of memory decline (average follow-up = 6.5 years).

RESULTS

At baseline, thinner pars opercularis cortex was associated with impaired recognition (p = 0.012; p = 0.060 after correcting for multiple comparisons). Worse delayed recall was associated with thinner pars opercularis (p = 0.001) and thinner rostral middle frontal cortex (p = 0.006) cross sectionally even after correcting for multiple comparisons. Delayed recall and recognition were not associated with medial temporal lobe (MTL), basal ganglia, or other prefrontal structures. Recognition impairment was variable over time, and there was little decline in delayed recall. Baseline MTL and prefrontal structures were not associated with delayed recall.

CONCLUSIONS

Episodic memory was associated with prefrontal structures, and MTL and prefrontal structures did not predict memory decline. There was relative stability in memory over time. Findings suggest that episodic memory is more related to frontal structures, rather than encroaching AD pathology, in middle-aged PWH. Additional research should clarify if recognition is useful clinically to differentiate aMCI and HAND.

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.

Inhibition of lipid synthesis by the HIV integrase strand transfer inhibitor elvitegravir in primary rat oligodendrocyte cultures

Combined antiretroviral therapy (cART) has greatly decreased mortality and morbidity among persons with HIV; however, neurologic impairments remain prevalent, in particular HIV-associated neurocognitive disorders (HANDs). White matter damage persists in cART-treated persons with HIV and may contribute to neurocognitive dysfunction as the lipid-rich myelin membrane of oligodendrocytes is essential for efficient nerve conduction. Because of the importance of lipids to proper myelination, we examined the regulation of lipid synthesis in oligodendrocyte cultures exposed to the integrase strand transfer inhibitor elvitegravir (EVG), which is administered to persons with HIV as part of their initial regimen. We show that protein levels of genes involved in the fatty acid pathway were reduced, which correlated with greatly diminished de novo levels of fatty acid synthesis. In addition, major regulators of cellular lipid metabolism, the sterol regulatory element-binding proteins (SREBP) 1 and 2, were strikingly altered following exposure to EVG. Impaired oligodendrocyte differentiation manifested as a marked reduction in mature oligodendrocytes. Interestingly, most of these deleterious effects could be prevented by adding serum albumin, a clinically approved neuroprotectant. These new findings, together with our previous study, strengthen the possibility that antiretroviral therapy, at least partially through lipid dysregulation, may contribute to the persistence of white matter changes observed in persons with HIV and that some antiretrovirals may be preferable as life-long therapy.

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.

Cerebral abnormalities in HIV-infected individuals with neurocognitive impairment revealed by fMRI

Although the combination antiretroviral treatment (cART) has considerably lowered the risk of HIV associated dementia (HAD), the incidence of neurocognitive impairments (NCI) has not decreased likely due to the insidious and slow progressive nature of HIV infection. Recent studies showed that the resting-state functional magnetic resonance imaging (rs-fMRI) is a prominent technique in helping the non-invasive analysis of neucognitive impairment. Our study is to explore the neuroimaging characteristics among people living with HIV (PLWH) with or without NCI in terms of cerebral regional and neural network by rs-fMRI, based on the hypothesis that HIV patients with and without NCI have independent brain imaging characteristics. 33 PLWH with NCI and 33 PLWH without NCI, recruited from the Cohort of HIV-infected associated Chronic Diseases and Health Outcomes, Shanghai, China (CHCDO) which was established in 2018, were categorized into the HIV-NCI and HIV-control groups, respectively, based on Mini-Mental State Examination (MMSE) results. The two groups were matched in terms of sex, education and age. Resting-state fMRI data were collected from all participants to analyze the fraction amplitude of low-frequency fluctuation (fALFF) and functional connectivity (FC) to assess regional and neural network alterations in the brain. Correlations between fALFF/FC values in specific brain regions and clinical characteristics were also examined. The results showed increased fALFF values in the bilateral calcarine gyrus, bilateral superior occipital gyrus, left middle occipital gyrus, and left cuneus in the HIV-NCI group compared to the HIV-control group. Additionally, increased FC values were observed between the right superior occipital gyrus and right olfactory cortex, bilateral gyrus rectus, and right orbital part of the middle frontal gyrus in the HIV-NCI group. Conversely, decreased FC values were found between the left hippocampus and bilateral medial prefrontal gyrus, as well as bilateral superior frontal gyrus. The study concluded that abnormal spontaneous activity in PLWH with NCI primarily occurred in the occipital cortex, while defects in brain networks were mostly associated with the prefrontal cortex. The observed changes in fALFF and FC in specific brain regions provide visual evidence to enhance our understanding of the central mechanisms underlying the development of cognitive impairment in HIV patients.

Brain volumetrics differ by Fiebig stage in acute HIV infection

OBJECTIVE

People with chronic HIV exhibit lower regional brain volumes compared to people without HIV (PWOH). Whether imaging alterations observed in chronic infection occur in acute HIV infection (AHI) remains unknown.

DESIGN

Cross-sectional study of Thai participants with AHI.

METHODS

One hundred and twelve Thai males with AHI (age 20-46) and 18 male Thai PWOH (age 18-40) were included. Individuals with AHI were stratified into early (Fiebig I-II; n  = 32) and late (Fiebig III-V; n  = 80) stages of acute infection using validated assays. T1-weighted scans were acquired using a 3 T MRI performed within five days of antiretroviral therapy (ART) initiation. Volumes for the amygdala, caudate nucleus, hippocampus, nucleus accumbens, pallidum, putamen, and thalamus were compared across groups.

RESULTS

Participants in late Fiebig stages exhibited larger volumes in the nucleus accumbens (8% larger; P  = 0.049) and putamen (19%; P  < 0.001) when compared to participants in the early Fiebig. Compared to PWOH, participants in late Fiebig exhibited larger volumes of the amygdala (9% larger; P  = 0.002), caudate nucleus (11%; P  = 0.005), nucleus accumbens (15%; P  = 0.004), pallidum (19%; P  = 0.001), and putamen (31%; P  < 0.001). Brain volumes in the nucleus accumbens, pallidum, and putamen correlated modestly with stimulant use over the past four months among late Fiebig individuals ( P s < 0.05).

CONCLUSIONS

Findings indicate that brain volume alterations occur in acute infection, with the most prominent differences evident in the later stages of AHI. Additional studies are needed to evaluate mechanisms for possible brain disruption following ART, including viral factors and markers of neuroinflammation.

Elevated frequency and everyday functioning implications of vascular depression in persons with HIV disease

Depression and cardiovascular disease are common and associated with one another in HIV disease. This study aimed to determine the frequency and everyday functioning implications of the clinical syndrome of vascular depression among people living with HIV (PLWH). Participants in this cross-sectional study included 536 PLWH and 272 seronegative individuals who completed a biomedical and psychiatric research evaluation. Vascular depression was operationalized as the current presence of: 1) two or more vascular conditions; and 2) depression as determined by a normative elevation on the Depression/Dejection subscale of the Profile of Mood States or a diagnosis of Major Depressive Disorder per the Composite International Diagnostic Interview. Everyday functioning was measured by both self- and clinician-rated activities of daily living. A logistic regression model showed that HIV was associated with a three-fold increased risk of vascular depression, independent of potential confounding factors. A second logistic regression model within the PLWH sample showed that PLWH with vascular depression had significantly greater odds of dependence in everyday functioning as compared to PLWH with either vascular disease or depression alone. The elevated frequency of vascular depression in PLWH is consistent with the vascular depression hypothesis from the late-life depression literature. The high rate of functional dependence among PLWH with vascular depression highlights the clinical importance of prospective work on this syndrome in the context of HIV disease.

Imaging of Brain Structural and Functional Effects in People With Human Immunodeficiency Virus

Before the introduction of antiretroviral therapy, human immunodeficiency virus (HIV) infection was often accompanied by central nervous system (CNS) opportunistic infections and HIV encephalopathy marked by profound structural and functional alterations detectable with neuroimaging. Treatment with antiretroviral therapy nearly eliminated CNS opportunistic infections, while neuropsychiatric impairment and peripheral nerve and organ damage have persisted among virally suppressed people with HIV (PWH), suggesting ongoing brain injury. Neuroimaging research must use methods sensitive for detecting subtle HIV-associated brain structural and functional abnormalities, while allowing for adjustments for potential confounders, such as age, sex, substance use, hepatitis C coinfection, cardiovascular risk, and others. Here, we review existing and emerging neuroimaging tools that demonstrated promise in detecting markers of HIV-associated brain pathology and explore strategies to study the impact of potential confounding factors on these brain measures. We emphasize neuroimaging approaches that may be used in parallel to gather complementary information, allowing efficient detection and interpretation of altered brain structure and function associated with suboptimal clinical outcomes among virally suppressed PWH. We examine the advantages of each imaging modality and systematic approaches in study design and analysis. We also consider advantages of combining experimental and statistical control techniques to improve sensitivity and specificity of biotype identification and explore the costs and benefits of aggregating data from multiple studies to achieve larger sample sizes, enabling use of emerging methods for combining and analyzing large, multifaceted data sets. Many of the topics addressed in this article were discussed at the National Institute of Mental Health meeting "Biotypes of CNS Complications in People Living with HIV," held in October 2021, and are part of ongoing research initiatives to define the role of neuroimaging in emerging alternative approaches to identifying biotypes of CNS complications in PWH. An outcome of these considerations may be the development of a common neuroimaging protocol available for researchers to use in future studies examining neurological changes in the brains of PWH.

Regular cannabis use modulates the impact of HIV on the neural dynamics serving cognitive control

BACKGROUND

Cannabis use and HIV are independently associated with decrements in cognitive control. However, the combined effects of HIV and regular cannabis use on the brain circuitry serving higher-order cognition are unclear.

AIMS

Investigate the interaction between cannabis and HIV on neural interference effects during the flanker task and spontaneous activity in regions underlying higher-order cognition.

METHODS

The sample consisted of 100 participants, including people with HIV (PWH) who use cannabis, PWH who do not use cannabis, uninfected cannabis users, and uninfected nonusers. Participants underwent an interview regarding their substance use history and completed the Eriksen flanker task during magnetoencephalography (MEG). MEG data were imaged in the time-frequency domain and oscillatory maps depicting the neural flanker interference effect were probed for group differences. Voxel time series were then assessed for group-level differences in spontaneous activity.

RESULTS

Group differences in behavioral performance were identified along with group differences in theta and alpha neural interference responses in higher-order regions across the cortex, with nonusers with HIV generally exhibiting the most aberrant responses. Likewise, time series analyses indicated that nonusers with HIV also had significantly elevated spontaneous alpha activity in the left inferior frontal and dorsolateral prefrontal cortices (dlPFC). Finally, we found that spontaneous and oscillatory alpha activity were significantly coupled in the inferior frontal cortex and dlPFC among cannabis users, but not nonusers.

CONCLUSIONS

Regular cannabis use appears to suppress the impact of HIV on spontaneous and oscillatory alpha deficits in the left inferior frontal cortex and dlPFC.

Neuropathogenesis of HIV-1: insights from across the spectrum of acute through long-term treated infection

This review outlines the neuropathogenesis of HIV, from initial HIV entry into the central nervous system (CNS) to chronic infection, focusing on key advancements in the last 5 years. Discoveries regarding acute HIV infection reveal timing and mechanisms of early HIV entry and replication in the CNS, early inflammatory responses, and establishment of genetically distinct viral reservoirs in the brain. Recent studies additionally explore how chronic HIV infection is maintained in the CNS, examining how the virus remains in a latent "hidden" state in diverse cells in the brain, and how this leads to sustained pathological inflammatory responses. Despite viral suppression with antiretroviral therapy, HIV can persist and even replicate in the CNS, and associate with ongoing neuropathology including CD8 + T-lymphocyte mediated encephalitis. Crucial investigation to advance our understanding of the immune mechanisms that both control viral infection and lead to pathological consequences in the brain is necessary to develop treatments to optimize long-term neurologic health in people living with HIV.

Identification, Quantification, and Characterization of HIV-1 Reservoirs in the Human Brain

The major barrier to cure HIV infection is the early generation and extended survival of HIV reservoirs in the circulation and tissues. Currently, the techniques used to detect and quantify HIV reservoirs are mostly based on blood-based assays; however, it has become evident that viral reservoirs remain in tissues. Our study describes a novel multi-component imaging method (HIV DNA, mRNA, and viral proteins in the same assay) to identify, quantify, and characterize viral reservoirs in tissues and blood products obtained from HIV-infected individuals even when systemic replication is undetectable. In the human brains of HIV-infected individuals under ART, we identified that microglia/macrophages and a small population of astrocytes are the main cells with integrated HIV DNA. Only half of the cells with integrated HIV DNA expressed viral mRNA, and one-third expressed viral proteins. Surprisingly, we identified residual HIV-p24, gp120, nef, vpr, and tat protein expression and accumulation in uninfected cells around HIV-infected cells suggesting local synthesis, secretion, and bystander uptake. In conclusion, our data show that ART reduces the size of the brain's HIV reservoirs; however, local/chronic viral protein secretion still occurs, indicating that the brain is still a major anatomical target to cure HIV infection.

Application of Diffusion Tensor Imaging (DTI) in the Diagnosis of HIV-Associated Neurocognitive Disorder (HAND): A Meta-Analysis and a System Review

Background

The patients with HIV-associated neurocognitive disorder (HAND) are often accompanied by white matter structure damage. Diffusion tensor imaging (DTI) is an important tool to detect white matter structural damage. However, the changes in DTI values reported in many studies are diverse in different white matter fiber tracts and brain regions.

Purpose

Our research is dedicated to evaluating the consistency and difference of the correlation between HAND and DTI measures in different studies. Additionally, the value of DTI in HAND evaluation is used to obtain consensus and independent conclusions between studies.

Methods

We searched PubMed and Web of Science to collect relevant studies using DTI for the diagnosis of HAND. After screening and evaluating the search results, meta-analysis is used for quantitative research on data. Articles that cannot collect data but meet the research relevance will be subjected to a system review.

Results

The meta-analysis shows that the HAND group has lower fractional anisotropy (standardized mean difference = −0.57 p < 0.0001) and higher mean diffusivity (standardized mean difference = 0.04 p < 0.0001) than the healthy control group in corpus callosum. In other white matter fibers, we found similar changes in fractional anisotropy (standardized mean difference = −1.18 p < 0.0001) and mean diffusivity (standardized mean difference = 0.69 p < 0.0001). However, the heterogeneity (represented by I²) between the studies is high (in corpus callosum 94, 88%, in other matter fibers 95, 81%). After subgroup analysis, the heterogeneity is obtained as 19.5, 40.7% (FA, MD in corpus callosum) and 0, 0% (FA, MD among other white matter fibers).

Conclusion

The changes in white matter fibers in patients with HAND are statistically significant at the observation level of DTI compared with healthy people. The differences between the studies are mainly derived from demographics, start and maintenance time of antiretroviral therapy, differences in nadir CD4+T cells, and the use of different neurocognitive function scales. As an effective method to detect the changes in white matter fibers, DTI is of great significance for the diagnosis of HAND, but there are still some shortcomings. In the absence of neurocognitive function scales, independent diagnosis remains difficult.

Systematic Review Registration:https://inplasy.com/inplasy-2021-10-0079/.

Altered white matter microstructure and neurocognitive function of HIV-infected patients with low nadir CD4

Altered white matter microstructure has been reported repeatedly using diffusion tensor imaging (DTI) in HIV-associated neurocognitive disorders. However, the associations between neurocognitive deficits and impaired white matter remains obscure due to frequent physical and psychiatric comorbidities in the patients. Severe immune suppression, reflected by low nadir CD4 T-cell counts, is reported to be associated with the neurocognitive deficits in the patients. In the present study, we examined white matter integrity using DTI and tract-based spatial statistics (TBSS), and neurocognitive functions using a battery of tests, in 15 HIV-infected patients with low nadir CD4, 16 HIV-infected patients with high nadir CD4, and 33 age- and sex-matched healthy controls. As DTI measures, we analyzed fractional anisotropy (FA) and mean diffusivity (MD). In addition, we investigated the correlation between white matter impairments and neurocognitive deficits. Among the three participant groups, the patients with low nadir CD4 showed significantly lower performance in processing speed and motor skills, and had significantly increased MD in widespread regions of white matter in both hemispheres. In the patients with low nadir CD4, there was a significant negative correlation between motor skills and MD in the right motor tracts, as well as in the corpus callosum. In summary, this study may provide white matter correlates of neurocognitive deficits in HIV-infected patients with past severe immune suppression as legacy effects.

Brain aging and cardiovascular factors in HIV: a longitudinal volume and shape MRI study

OBJECTIVE

We aimed to examine the relative contributions of HIV infection, age, and cardiovascular risk factors to subcortical brain atrophy in people with HIV (PWH).

DESIGN

Longitudinal observational study.

METHODS

Virally suppressed PWH with low neuropsychological confounds (n  = 75) and demographically matched HIV-negative controls (n = 31) completed baseline and 18-month follow-up MRI scans, neuropsychological evaluation, cardiovascular assessments, and HIV laboratory tests. PWH were evaluated for HIV-associated neurocognitive disorder (HAND). Subcortical volumes were extracted with Freesurfer after removal of white matter hyperintensities. Volumetric and shape analyses were conducted using linear mixed-effect models incorporating interactions between age, time, and each of HIV status, HAND status, HIV disease factors, and cardiovascular markers.

RESULTS

Across baseline and follow-up PWH had smaller volumes of most subcortical structures compared with HIV-negative participants. In addition, over time older PWH had a more rapid decline in caudate volumes (P  = 0.041), predominantly in the more severe HAND subgroups (P = 0.042). Higher CD4+ cell counts had a protective effect over time on subcortical structures for older participants with HIV. Increased cardiovascular risk factors were associated with smaller volumes across baseline and follow-up for most structures, although a more rapid decline over time was observed for striatal volumes. There were no significant shape analyses findings.

CONCLUSION

The study demonstrates a three-hit model of general (as opposed to localized) subcortical injury in PWH: HIV infection associated with smaller volumes of most subcortical structures, HIV infection and aging synergy in the striatum, and cardiovascular-related injury linked to early and more rapid striatal atrophy.

Abnormal cognitive aging in people with HIV: Evidence from Data Integration between two countries' cohort studies

OBJECTIVES

Previous research has shown inconsistent results on whether cognitive aging is abnormal in people with HIV (PWH) because of low sample size, cross-sectional design, and nonstandard neuropsychological methods. To address these issues, we integrated data from two longitudinal studies: Australian HIV and Brain Ageing Research Program (N = 102) and CNS HIV Antiretroviral Therapy Effects Research (CHARTER) study (N = 924) and determined the effect of abnormal aging on neurocognitive impairment (NCI) among PWH.

METHODS

Both studies used the same neuropsychological test battery. NCI was defined based on demographically corrected global deficit score (≥0.5 = impaired). Both studies also assessed comorbidities, neuropsychiatric conditions and functional status using similar tools. To determine the cross-sectional and longitudinal effects of age on the risk of NCI, a generalized linear mixed-effect model tested main and interaction effects of age group (young, <50 vs. old, ≥50) and time on NCI adjusting the effects of covariates.

RESULTS

Older PWH had 83% higher chance of NCI compared with younger PWH [odds ratio (OR) = 1.83 (1.15-2.90), P < 0.05]. Older participants also had a greater risk of increases in NCI over the follow-up [OR = 1.66 (1.05-2.64), P < 0.05] than younger participants. Nonwhite ethnicity (P < 0.05), having a contributing (P < 0.05) or confounding (P < 0.001) comorbidity, greater cognitive symptoms (P < 0.001), and abnormal creatinine level (P < 0.05), plasma viral load greater than 200 copies/ml (P < 0.05), being from the Australian cohort (P < 0.05) were also associated with a higher risk of NCI.

CONCLUSION

Data integration may serve as a strategy to increase sample size and study power to better assess abnormal cognitive aging effect in PWH, which was significant in the current study.

Evidence for neuropsychological health disparities in Black Americans with HIV disease

OBJECTIVE

Black Americans are at high risk for HIV disease and associated morbidity. The impact and clinical correlates of HIV-associated neurocognitive impairment among Black Americans is not fully understood. The current study uses a full factorial design to examine the independent and combined effects of race and HIV disease on neurocognitive functioning, including its associations with everyday functioning and clinical disease markers in Black and White persons with HIV (PWH).

METHOD

Participants included 40 Black PWH, 83 White PWH, 28 Black HIV- and 64 White HIV- individuals. Neurocognition was measured by raw sample-based z-scores from a clinical battery. Everyday functioning was assessed using self- and clinician-rated measures of cognitive symptoms and activities of daily living. HIV-associated neurocognitive disorders were also classified using demographically adjusted normative standards and the Frascati criteria.

RESULTS

We observed a significant three-way interaction between HIV, race, and domain on raw neurocognitive z-scores. This omnibus effect was driven by medium and large effect size decrements in processing speed and semantic memory, respectively, in Black PWH compared to other study groups. Black PWH also demonstrated higher frequencies of HIV-associated neurocognitive disorders as compared to White PWH. Unexpectedly, global neurocognitive performance was negatively related to everyday functioning impairments for White PWH, but not for Black PWH.

CONCLUSIONS

Systemic disadvantages for Black Americans may combine with HIV disease to compound some neurocognitive impairments in this under-served population. Prospective studies are needed to identify better ways to prevent, measure, diagnose, and manage HIV-associated neurocognitive disorders among Black Americans.

High-content analysis and Kinetic Image Cytometry identify toxicity and epigenetic effects of HIV antiretrovirals on human iPSC-neurons and primary neural precursor cells

INTRODUCTION

Despite viral suppression due to combination antiretroviral therapy (cART), HIV-associated neurocognitive disorders (HAND) continue to affect half of people with HIV, suggesting that certain antiretrovirals (ARVs) may contribute to HAND.

METHODS

We examined the effects of nucleoside/nucleotide reverse transcriptase inhibitors tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) and the integrase inhibitors dolutegravir (DTG) and elvitegravir (EVG) on viability, structure, and function of glutamatergic neurons (a subtype of CNS neuron involved in cognition) derived from human induced pluripotent stem cells (hiPSC-neurons), and primary human neural precursor cells (hNPCs), which are responsible for neurogenesis.

RESULTS

Using automated digital microscopy and image analysis (high content analysis, HCA), we found that DTG, EVG, and TDF decreased hiPSC-neuron viability, neurites, and synapses after 7 days of treatment. Analysis of hiPSC-neuron calcium activity using Kinetic Image Cytometry (KIC) demonstrated that DTG and EVG also decreased the frequency and magnitude of intracellular calcium transients. Longer ARV exposures and simultaneous exposure to multiple ARVs increased the magnitude of these neurotoxic effects. Using the Microscopic Imaging of Epigenetic Landscapes (MIEL) assay, we found that TDF decreased hNPC viability and changed the distribution of histone modifications that regulate chromatin packing, suggesting that TDF may reduce neuroprogenitor pools important for CNS development and maintenance of cognition in adults.

CONCLUSION

This study establishes human preclinical assays that can screen potential ARVs for CNS toxicity to develop safer cART regimens and HAND therapeutics.

Prior Methamphetamine Use Disorder History Does Not Impair Interoceptive Processing of Soft Touch in HIV Infection

Introduction: Interoception, defined as the sense of the internal state of one’s body, helps motivate goal-directed behavior. Prior work has shown that methamphetamine (METH) use disorder is associated with altered interoception, and that this may contribute to risky behavior. As people with HIV (PWH) may also experience disrupted bodily sensations (e.g., neuropathy), an important question is whether PWH with a history of METH use disorder might exhibit greater impairment of interoceptive processing. Methods: Eighty-three participants stratified by HIV infection and a past history of methamphetamine use disorder experienced a soft touch paradigm that included slow brush strokes on the left forearm and palm during blood-oxygen level-dependent functional MRI acquisition. To assess differences in interoception and reward, voxelwise analyses were constrained to the insula, a hub for the evaluation of interoceptive cues, and the striatum, which is engaged in reward processing. Results: Overall, individuals with a history of METH use disorder had an attenuated neural response to pleasant touch in both the insula and striatum. Longer abstinence was associated with greater neural response to touch in the insula, suggesting some improvement in responsivity. However, only PWH with no METH use disorder history had lower brain activation in the insula relative to non-using seronegative controls. Conclusions: Our findings suggest that while METH use disorder history and HIV infection independently disrupt the neural processes associated with interoception, PWH with METH use disorder histories do not show significant differences relative to non-using seronegative controls. These findings suggest that the effects of HIV infection and past methamphetamine use might not be additive with respect to interoceptive processing impairment.

Cerebrovascular Disease Correlates With Longitudinal Brain Atrophy in Virally Suppressed Older People Living With HIV

BACKGROUND

Mild cognitive difficulties and progressive brain atrophy are observed in older people living with HIV (PLWH) despite persistent viral suppression. Whether cerebrovascular disease (CVD) risk factors and white matter hyperintensity (WMH) volume correspond to the observed progressive brain atrophy is not well understood.

METHODS

Longitudinal structural brain atrophy rates and WMH volume were examined among 57 HIV-infected participants and 40 demographically similar HIV-uninfected controls over an average (SD) of 3.4 (1.7) years. We investigated associations between CVD burden (presence of diabetes, hypertension, hyperlipidemia, obesity, smoking history, and atrial fibrillation) and WMH with atrophy over time.

RESULTS

The mean (SD) age was 64.8 (4.3) years for PLWH and 66.4 (3.2) years for controls. Participants and controls were similar in age and sex (P > 0.05). PLWH were persistently suppressed (VL <375 copies/mL with 93% <75 copies/mL). The total number of CVD risk factors did not associate with atrophy rates in any regions of interests examined; however, body mass index independently associated with progressive atrophy in the right precentral gyrus (β = -0.30; P = 0.023), parietal lobe (β = -0.28; P = 0.030), and frontal lobe atrophy (β = -0.27; P = 0.026) of the HIV-infected group. No associations were found in the HIV-uninfected group. In both groups, baseline WMH was associated with progressive atrophy rates bilaterally in the parietal gray in the HIV-infected group (β = -0.30; P = 0.034) and the HIV-uninfected participants (β = -0.37; P = 0.033).

CONCLUSIONS

Body mass index and WMH are associated with atrophy in selective brain regions. However, CVD burden seems to partially contribute to progressive brain atrophy in older individuals regardless of HIV status, with similar effect sizes. Thus, CVD alone is unlikely to explain accelerated atrophy rates observed in virally suppressed PLWH. In older individuals, addressing modifiable CVD risk factors remains important to optimize brain health.

Gray matter volumes discriminate cognitively impaired and unimpaired people with HIV

BACKGROUND

Current diagnostic criteria of HIV-associated neurocognitive disorders (HAND) rely on neuropsychological assessments. The aim of this study was to evaluate if gray matter volumes (GMV) can distinguish people with HAND, neurocognitively unimpaired people with HIV (unimpaired PWH), and uninfected controls using linear discriminant analyses.

METHODS

A total of 231 participants, including 110 PWH and 121 uninfected controls, completed a neuropsychological assessment and an MRI protocol. Among PWH, HAND (n = 48) and unimpaired PWH (n = 62) designations were determined using the widely accepted Frascati criteria. We then assessed the extent to which GMV, corrected for intracranial volume, could accurately distinguish the three groups using linear discriminant analysis. Sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, area under the curve (AUC), and accuracy were computed for each model using the classification results based on GMV compared to the neuropsychological assessment.

RESULTS

The best performing model was comprised of bilaterally combined GMV and was stratified by sex. Among males, sensitivity was 85.2% (95% CI: 66.3%-95.8%), specificity was 97.0% (95% CI: 91.6%-99.4%), and the AUC was 0.91 (95% CI: 0.83-0.99). Among females, sensitivity was 100.0% (95% CI: 83.9%-100.0%), specificity was 98.8% (95% CI: 93.4%-100.0%), and the AUC was 0.99 (95% CI: 0.98-1.00).

CONCLUSIONS

GMV accurately discriminated HAND from unimpaired PWH and controls. Measures of GMV may be highly sensitive to HAND, and revisions to the Frascati criteria should consider including GMV in conjunction with a neuropsychological assessment to diagnose HAND.

Higher CSF Ferritin Heavy-Chain (Fth1) and Transferrin Predict Better Neurocognitive Performance in People with HIV

HIV-associated neurocognitive disorder (HAND) remains prevalent despite antiretroviral therapy and involves white matter damage in the brain. Although iron is essential for myelination and myelin maintenance/repair, its role in HAND is largely unexplored. We tested the hypotheses that cerebrospinal fluid (CSF) heavy-chain ferritin (Fth1) and transferrin, proteins integral to iron delivery and myelination, are associated with neurocognitive performance in people with HIV (PWH). Fth1, transferrin, and the pro-inflammatory cytokines TNF-α and IL-6 were quantified in CSF at baseline (entry) in 403 PWH from a prospective observational study who underwent serial, comprehensive neurocognitive assessments. Associations of Fth1 and transferrin with Global Deficit Score (GDS)-defined neurocognitive performance at baseline and 30-42 months of follow-up were evaluated by multivariable regression. While not associated with neurocognitive performance at baseline, higher baseline CSF Fth1 predicted significantly better neurocognitive performance over 30 months in all PWH (p < 0.05), in PWH aged < 50 at 30, 36, and 42 months (all p < 0.05), and in virally suppressed PWH at all three visit time-points (all p < 0.01). Higher CSF transferrin was associated with superior neurocognitive performance at all visits, primarily in viremic individuals (all p < 0.05). All associations persisted after adjustment for neuro-inflammation. In summary, higher CSF Fth1 is neuroprotective over prolonged follow-up in all and virally suppressed PWH, while higher CSF transferrin may be most neuroprotective during viremia. We speculate that higher CSF levels of these critical iron-delivery proteins support improved myelination and consequently, neurocognitive performance in PWH, providing a rationale for investigating their role in interventions to prevent and/or treat HAND.

Impact of HIV-infection on human somatosensory processing, spontaneous cortical activity, and cortical thickness: A multimodal neuroimaging approach

HIV-infection has been associated with widespread alterations in brain structure and function, although few studies have examined whether such aberrations are co-localized and the degree to which clinical and cognitive metrics are related. We examine this question in the somatosensory system using high-resolution structural MRI (sMRI) and magnetoencephalographic (MEG) imaging of neural oscillatory activity. Forty-four participants with HIV (PWH) and 55 demographically-matched uninfected controls completed a paired-pulse somatosensory stimulation paradigm during MEG and underwent 3T sMRI. MEG data were transformed into the time-frequency domain; significant sensor level responses were imaged using a beamformer. Virtual sensor time series were derived from the peak responses. These data were used to compute response amplitude, sensory gating metrics, and spontaneous cortical activity power. The T1-weighted sMRI data were processed using morphological methods to derive cortical thickness values across the brain. From these, the cortical thickness of the tissue coinciding with the peak response was estimated. Our findings indicated both PWH and control exhibit somatosensory gating, and that spontaneous cortical activity was significantly stronger in PWH within the left postcentral gyrus. Interestingly, within the same tissue, PWH also had significantly reduced cortical thickness relative to controls. Follow-up analyses indicated that the reduction in cortical thickness was significantly correlated with CD4 nadir and mediated the relationship between HIV and spontaneous cortical activity within the left postcentral gyrus. These data indicate that PWH have abnormally strong spontaneous cortical activity in the left postcentral gyrus and such elevated activity is driven by locally reduced cortical gray matter thickness.

Preliminary Evidence for a Relationship between Elevated Plasma TNFα and Smaller Subcortical White Matter Volume in HCV Infection Irrespective of HIV or AUD Comorbidity

Classical inflammation in response to bacterial, parasitic, or viral infections such as HIV includes local recruitment of neutrophils and macrophages and the production of proinflammatory cytokines and chemokines. Proposed biomarkers of organ integrity in Alcohol Use Disorders (AUD) include elevations in peripheral plasma levels of proinflammatory proteins. In testing this proposal, previous work included a group of human immunodeficiency virus (HIV)-infected individuals as positive controls and identified elevations in the soluble proteins TNFα and IP10; these cytokines were only elevated in AUD individuals seropositive for hepatitis C infection (HCV). The current observational, cross-sectional study evaluated whether higher levels of these proinflammatory cytokines would be associated with compromised brain integrity. Soluble protein levels were quantified in 86 healthy controls, 132 individuals with AUD, 54 individuals seropositive for HIV, and 49 individuals with AUD and HIV. Among the patient groups, HCV was present in 24 of the individuals with AUD, 13 individuals with HIV, and 20 of the individuals in the comorbid AUD and HIV group. Soluble protein levels were correlated to regional brain volumes as quantified with structural magnetic resonance imaging (MRI). In addition to higher levels of TNFα and IP10 in the 2 HIV groups and the HCV-seropositive AUD group, this study identified lower levels of IL1β in the 3 patient groups relative to the control group. Only TNFα, however, showed a relationship with brain integrity: in HCV or HIV infection, higher peripheral levels of TNFα correlated with smaller subcortical white matter volume. These preliminary results highlight the privileged status of TNFα on brain integrity in the context of infection.

Iron-regulatory genes are associated with Neuroimaging measures in HIV infection

The pathogenesis of HIV-associated neurocognitive impairment (NCI) may involve iron dysregulation. In 243 HIV-seropositive adults without severe comorbidities, we therefore genotyped 250 variants in 20 iron-related genes and evaluated their associations with magnetic resonance imaging measures of brain structure and metabolites, including measures previously linked to NCI. Multivariable regression analyses examined associations between genetic variants and neuroimaging measures, adjusting for relevant covariates and multiple testing. Exploratory analyses stratified by NCI (Global Deficit Score ≥ 0.5 vs. <0.5), virus detectability in plasma, and comorbidity levels were also performed. Of 27 variants (in 12 iron-regulatory genes) associated with neuroimaging measures after correction for the 37 haplotype blocks represented, 3 variants survived additional correction for the 21 neuroimaging measures evaluated and demonstrated biologically plausible associations. SLC11A1 rs7576974_T was significantly associated with higher frontal gray matter N-acetylaspartate (p = 3.62e^-5). Among individuals with detectable plasma virus, TFRC rs17091382_A was associated with smaller subcortical gray matter volume (p = 3.23e^-5), and CP rs4974389_A (p = 3.52e^-5) was associated with higher basal ganglia Choline in persons with mild comorbidities. Two other strong associations were observed for variants in SLC40A1 and ACO2 but were not robust due to low minor-allele frequencies in the study sample. Variants in iron metabolism and transport genes are associated with structural and metabolite neuroimaging measures in HIV-seropositive adults, regardless of virus suppression on antiretroviral therapy. These variants may confer susceptibility to HIV-related brain injury and NCI. Further studies are needed to determine the specificity of these findings to HIV infection and explore potential underlying mechanisms.

Association of White Matter Hyperintensities With HIV Status and Vascular Risk Factors

OBJECTIVE

To test the hypothesis that brain white matter hyperintensities (WMH) are more common in people living with HIV (PLWH), even in the setting of well-controlled infection, and to identify clinical measures that correlate with these abnormalities.

METHODS

Research brain MRI scans, acquired within longitudinal studies evaluating neurocognitive outcomes, were reviewed to determine WMH load using the Fazekas visual rating scale in PLWH with well-controlled infection (antiretroviral therapy for at least 1 year and plasma viral load <200 copies/mL) and in sociodemographically matched controls without HIV (CWOH). The primary outcome measure of this cross-sectional analysis was increased WMH load, determined by total Fazekas score ≥2. Multiple logistic regression analysis was performed to evaluate the effect of HIV serostatus on WMH load and to identify MRI, CSF, and clinical variables that associate with WMH in the PLWH group.

RESULTS

The study included 203 PLWH and 58 CWOH who completed a brain MRI scan between April 2014 and March 2019. The multiple logistic regression analysis, with age and history of tobacco use as covariates, showed that the adjusted odds ratio of the PLWH group for increased WMH load is 3.7 (95% confidence interval 1.8-7.5; p = 0.0004). For the PLWH group, increased WMH load was associated with older age, male sex, tobacco use, hypertension, and hepatitis C virus coinfection, and also with the presence of measurable tumor necrosis factor α in CSF.

CONCLUSION

Our results suggest that HIV serostatus affects the extent of brain WMH. This effect is mainly associated with aging and modifiable comorbidities.

Association of Immunosuppression and Viral Load With Subcortical Brain Volume in an International Sample of People Living With HIV

Importance

Despite more widely accessible combination antiretroviral therapy (cART), HIV-1 infection remains a global public health challenge. Even in treated patients with chronic HIV infection, neurocognitive impairment often persists, affecting quality of life. Identifying the neuroanatomical pathways associated with infection in vivo may delineate the neuropathologic processes underlying these deficits. However, published neuroimaging findings from relatively small, heterogeneous cohorts are inconsistent, limiting the generalizability of the conclusions drawn to date.

Objective

To examine structural brain associations with the most commonly collected clinical assessments of HIV burden (CD4+ T-cell count and viral load), which are generalizable across demographically and clinically diverse HIV-infected individuals worldwide.

Design, Setting, and Participants

This cross-sectional study established the HIV Working Group within the Enhancing Neuro Imaging Genetics Through Meta Analysis (ENIGMA) consortium to pool and harmonize data from existing HIV neuroimaging studies. In total, data from 1295 HIV-positive adults were contributed from 13 studies across Africa, Asia, Australia, Europe, and North America. Regional and whole brain segmentations were extracted from data sets as contributing studies joined the consortium on a rolling basis from November 1, 2014, to December 31, 2019.

Main Outcomes and Measures

Volume estimates for 8 subcortical brain regions were extracted from T1-weighted magnetic resonance images to identify associations with blood plasma markers of current immunosuppression (CD4+ T-cell counts) or detectable plasma viral load (dVL) in HIV-positive participants. Post hoc sensitivity analyses stratified data by cART status.

Results

After quality assurance, data from 1203 HIV-positive individuals (mean [SD] age, 45.7 [11.5] years; 880 [73.2%] male; 897 [74.6%] taking cART) remained. Lower current CD4+ cell counts were associated with smaller hippocampal (mean [SE] β = 16.66 [4.72] mm3 per 100 cells/mm3; P < .001) and thalamic (mean [SE] β = 32.24 [8.96] mm3 per 100 cells/mm3; P < .001) volumes and larger ventricles (mean [SE] β = -391.50 [122.58] mm3 per 100 cells/mm3; P = .001); in participants not taking cART, however, lower current CD4+ cell counts were associated with smaller putamen volumes (mean [SE] β = 57.34 [18.78] mm3 per 100 cells/mm3; P = .003). A dVL was associated with smaller hippocampal volumes (d = -0.17; P = .005); in participants taking cART, dVL was also associated with smaller amygdala volumes (d = -0.23; P = .004).

Conclusions and Relevance

In a large-scale international population of HIV-positive individuals, volumes of structures in the limbic system were consistently associated with current plasma markers. Our findings extend beyond the classically implicated regions of the basal ganglia and may represent a generalizable brain signature of HIV infection in the cART era.

Neuroimaging Advances in Diagnosis and Differentiation of HIV, Comorbidities, and Aging in the cART Era

In the "cART era" of more widely available and accessible treatment, aging and HIV-related comorbidities, including symptoms of brain dysfunction, remain common among HIV-infected individuals on suppressive treatment. A better understanding of the neurobiological consequences of HIV infection is essential for developing thorough treatment guidelines and for optimizing long-term neuropsychological outcomes and overall brain health. In this chapter, we first summarize magnetic resonance imaging (MRI) methods used in over two decades of neuroHIV research. These methods evaluate brain volumetric differences and circuitry disruptions in adults living with HIV, and help map clinical correlations with brain function and tissue microstructure. We then introduce and discuss aging and associated neurological complications in people living with HIV, and processes by which infection may contribute to the risk for late-onset dementias. We describe how new technologies and large-scale international collaborations are helping to disentangle the effect of genetic and environmental risk factors on brain aging and neurodegenerative diseases. We provide insights into how these advances, which are now at the forefront of Alzheimer's disease research, may advance the field of neuroHIV. We conclude with a summary of how we see the field of neuroHIV research advancing in the decades to come and highlight potential clinical implications.

Assessing Cognitive Functioning in People Living With HIV (PLWH): Factor Analytic Results From CHARTER and NNTC Cohorts

BACKGROUND

Single summary scores, such as the Global Deficit Score, are often used to classify overall performance on neuropsychological batteries. The factor structure of test scores that underlie Global Deficit Score in studies of people living with HIV (PLWH) was assessed to determine whether individual test scores loaded onto a unitary factor to summarize performance.

SETTING

Secondary data analysis on baseline data of PLWH from National NeuroAIDS Tissue Consortium and CNS HIV Antiretroviral Therapy Effects Research (CHARTER) Study.

METHOD

Primary analyses included testing model structure and fit of neuropsychological test scores with confirmatory and exploratory factor analyses. Secondary analyses involved receiver operating characteristic curves, and associations with psychosocial and medical variables.

RESULTS

Participants with confounds were excluded, leading to 798 (National NeuroAIDS Tissue Consortium) and 1222 (CHARTER) cases. When confirmatory factor analysis models were structured to be consistent with theoretically-based cognitive domains, models did not fit adequately. Per exploratory factor analyses, tests assessing speeded information processing, working memory, and executive functions loaded onto a single factor and explained the most variance in both cohorts. This factor tended to be associated with age, estimated premorbid ability, and aspects of substance use history. Its relation to age, in context of demographically corrected neuropsychological scores, suggested accelerated aging.

CONCLUSION

Results indicate that individual neuropsychological tests did not load exactly onto expected domains, suggesting another framework for future analyses of cognitive domains. The possibility of a new index, and its use to assess cognitive impairment in PLWH, is suggested for further diagnostic and prognostic purposes.

Differential effects of integrase strand transfer inhibitors, elvitegravir and raltegravir, on oligodendrocyte maturation: A role for the integrated stress response

Regardless of adherence to combined antiretroviral therapy, white matter and myelin pathologies persist in patients with HIV-associated neurocognitive disorders, a spectrum of cognitive, motor, and behavioral impairments. We hypothesized that antiretroviral therapy alters the maturation of oligodendrocytes which synthesize myelin. We tested whether specific frontline integrase strand transfer inhibitors would alter oligodendrocyte differentiation and myelination. To model the effect of antiretrovirals on oligodendrocytes, we stimulated primary rat oligodendrocyte precursor cells to differentiate into mature oligodendrocytes in vitro in the presence of therapeutically relevant concentrations of elvitegravir or raltegravir and then assessed differentiation with lineage specific markers. To examine the effect of antiretrovirals on myelination, we treated mice with the demyelinating compound cuprizone, for 5 weeks. This was followed by 3 weeks of recovery in absence of cuprizone, during which time some mice received a daily intrajugular injection of elvitegravir. Brains were harvested, sectioned and processed by immunohistochemistry to examine oligodendrocyte maturation and myelination. Elvitegravir inhibited oligodendrocyte differentiation in vitro in a concentration-dependent manner, while raltegravir had no effect. Following cuprizone demyelination, administration of elvitegravir to adult mice reduced remyelination compared with control animals. Elvitegravir treatment activated the integrated stress response in oligodendrocytes in vitro, an effect which was completely blocked by pretreatment with the integrated stress response inhibitor Trans-ISRIB, preventing elvitegravir-mediated inhibition of oligodendrocyte maturation. These studies demonstrate that elvitegravir impairs oligodendrocyte maturation and remyelination and that the integrated stress response mediates this effect and may be a possible therapeutic target.

Association of HIV serostatus and metabolic syndrome with neurobehavioral disturbances

Metabolic syndrome (MetS), a constellation of related metabolic risk factors, is a common comorbidity associated with cognitive difficulty in people living with HIV (PLWH). Neurobehavioral disturbances (e.g., behavioral manifestations of frontal-subcortical dysfunction) are also prevalent in HIV, yet the role MetS might play in HIV-associated neurobehavioral disturbances is unknown. Thus, we examined the link between MetS and neurobehavioral disturbances in PLWH. Participants included 215 adults (117 PLWH, 98 HIV-uninfected), aged 36 to 65 years, from a cohort study at the University of California San Diego. Using the Frontal Systems Behavior Scale, we captured neurobehavioral disturbances (apathy, disinhibition, and executive dysfunction). MetS was defined by the National Cholesterol Education Program's Adult Treatment Panel-III criteria. Covariates examined included demographic, neurocognitive impairment, and psychiatric characteristics. When controlling for relevant covariates, both HIV serostatus and MetS were independently associated with greater apathy and executive dysfunction. HIV, but not MetS, was associated with greater disinhibition. The present findings suggest an additive effect of HIV and MetS on specific neurobehavioral disturbances (apathy and executive dysfunction), underscoring the importance of identifying and treating both HIV and MetS to lessen central nervous system burden among PLWH.

Evidence for a novel subcortical mechanism for posterior cingulate cortex atrophy in HIV peripheral neuropathy

We previously reported that neuropathic pain was associated with smaller posterior cingulate cortical (PCC) volumes, suggesting that a smaller/dysfunctional PCC may contribute to development of pain via impaired mind wandering. A gap in our previous report was lack of evidence for a mechanism for the genesis of PCC atrophy in HIV peripheral neuropathy. Here we investigate if volumetric differences in the subcortex for those with neuropathic paresthesia may contribute to smaller PCC volumes, potentially through deafferentation of ascending white matter tracts resulting from peripheral nerve damage in HIV neuropathy. Since neuropathic pain and paresthesia are highly correlated, statistical decomposition was used to separate pain and paresthesia symptoms to determine which regions of brain atrophy are associated with both pain and paresthesia and which are associated separately with pain or paresthesia. HIV+ individuals (N = 233) with and without paresthesia in a multisite study underwent structural brain magnetic resonance imaging. Voxel-based morphometry and a segmentation/registration tool were used to investigate regional brain volume changes associated with paresthesia. Analysis of decomposed variables found that smaller midbrain and thalamus volumes were associated with paresthesia rather than pain. However, atrophy in the PCC was related to both pain and paresthesia. Peak thalamic atrophy (p = 0.004; MNI x = - 14, y = - 24, z = - 2) for more severe paresthesia was in a region with reciprocal connections with the PCC. This provides initial evidence that smaller PCC volumes in HIV peripheral neuropathy are related to ascending white matter deafferentation caused by small fiber damage observed in HIV peripheral neuropathy.

Brain structural correlates of trajectories to cognitive impairment in men with and without HIV disease

There are distinct trajectories to cognitive impairment among participants in the Multicenter AIDS Cohort Study (MACS). Here we analyzed the relationship between regional brain volumes and the individual trajectories to impairment in a subsample (n = 302) of the cohort. 302 (167 HIV-infected; mean age = 55.7 yrs.; mean education: 16.2 yrs.) of the men enrolled in the MACS MRI study contributed data to this analysis. We used voxel-based morphometry (VBM) to segment the brain images to analyze gray and white matter volume at the voxel-level. A Mixed Membership Trajectory Model had previously identified three distinct profiles, and each study participant had a membership weight for each of these three trajectories. We estimated VBM model parameters for 100 imputations, manually performed the post-hoc contrasts, and pooled the results. We examined the associations between brain volume at the voxel level and the MMTM membership weights for two profiles: one considered "unhealthy" and the other considered "Premature aging." The unhealthy profile was linked to the volume of the posterior cingulate gyrus/precuneus, the inferior frontal cortex, and the insula, whereas the premature aging profile was independently associated with the integrity of a portion of the precuneus. Trajectories to cognitive impairment are the result, in part, of atrophy in cortical regions linked to normal and pathological aging. These data suggest the possibility of predicting cognitive morbidity based on patterns of CNS atrophy.

COMT Val158Met Polymorphism, Cardiometabolic Risk, and Nadir CD4 Synergistically Increase Risk of Neurocognitive Impairment in Men Living With HIV

OBJECTIVE

The Val allele of the Val158Met single-nucleotide polymorphism of the catechol-o-methyltransferase gene (COMT) results in faster metabolism and reduced bioavailability of dopamine (DA). Among persons living with HIV, Val carriers display neurocognitive deficits relative to Met carriers, presumably due to exacerbation of HIV-related depletion of DA. COMT may also impact neurocognition by modulating cardiometabolic function, which is often dysregulated among persons living with HIV. We examined the interaction of COMT, cardiometabolic risk, and nadir CD4 on neurocognitive impairment (NCI) among HIV+ men.

METHODS

Three hundred twenty-nine HIV+ men underwent COMT genotyping and neurocognitive and neuromedical assessments. Cohort-standardized z scores for body mass index, systolic blood pressure, glucose, triglycerides, and high-density lipoprotein cholesterol were averaged to derive a cardiometabolic risk score (CMRS). NCI was defined as demographically adjusted global deficit score of ≥0.5. Logistic regression modeled NCI as a function of COMT, CMRS, and their interaction, covarying for estimated premorbid function, race/ethnicity, and HIV-specific characteristics. Follow-up analysis included the 3-way interaction of COMT, CMRS, and nadir CD4.

RESULTS

Genotypes were 81 (24.6%) Met/Met, 147 (44.7%) Val/Met, and 101 (30.7%) Val/Val. COMT interacted with CMRS (P = 0.02) such that higher CMRS increased risk of NCI among Val/Val [odds ratio (OR) = 2.13, P < 0.01], but not Val/Met (OR = 0.93, P > 0.05) or Met/Met (OR = 0.92, P > 0.05) carriers. Among Val/Val, nadir CD4 moderated the effect of CMRS (P < 0.01) such that higher CMRS increased likelihood of NCI only when nadir CD4 <180.

DISCUSSION

Results suggest a tripartite model by which genetically driven low DA reserve, cardiometabolic dysfunction, and historical immunosuppression synergistically enhance risk of NCI among HIV+ men, possibly due to neuroinflammation and oxidative stress.

Neuroimaging Findings in Chronic Hepatitis C Virus Infection: Correlation with Neurocognitive and Neuropsychiatric Manifestations

Chronic hepatitis C virus (HCV) infection is commonly associated with neurocognitive dysfunction, altered neuropsychological performance and neuropsychiatric symptoms. Quantifiable neuropsychological changes in sustained attention, working memory, executive function, verbal learning and recall are the hallmark of HCV-associated neurocognitive disorder (HCV-AND). This constellation is at variance with the neuropsychological complex that is seen in minimal hepatic encephalopathy, which is typified by an array of alterations in psychomotor speed, selective attention and visuo-constructive function. Noncognitive symptoms, including sleep disturbances, depression, anxiety and fatigue, which are less easily quantifiable, are frequently encountered and can dominate the clinical picture and the clinical course of patients with chronic HCV infection. More recently, an increased vulnerability to Parkinson’s disease among HCV-infected patients has also been reported. The degree to which neurocognitive and neuropsychiatric changes are due to HCV replication within brain tissues or HCV-triggered peripheral immune activation remain to be determined. Without absolute evidence that clearly exonerates or indicts HCV, our understanding of the so-called “HCV brain syndrome”, relies primarily on clinical and neuropsychological assessments, although other comorbidities and substance abuse may impact on neurocognitive function, thus confounding an appropriate recognition. In recent years, a number of functional and structural brain imaging studies have been of help in recognizing possible biological markers of HCV-AND, thus providing a rationale for guiding and justifying antiviral therapy in selected cases. Here, we review clinical, neuroradiological, and therapeutic responses to interferon-based and interferon-free regimens in HCV-related cognitive and neuropsychiatric disorder.

Regional brain volumetric changes despite 2 years of treatment initiated during acute HIV infection

OBJECTIVE

To assess changes in regional brain volumes after 24 months among individuals who initiated combination antiretroviral therapy (cART) within weeks of HIV exposure.

DESIGN

Prospective cohort study of Thai participants in the earliest stages of HIV-1infection.

METHODS

Thirty-four acutely HIV-infected individuals (AHI; Fiebig I-V) underwent brain magnetic resonance (MR) imaging and MR spectroscopy at 1.5 T and immediately initiated cART. Imaging was repeated at 24 months. Regional brain volumes were quantified using FreeSurfer's longitudinal pipeline. Voxel-wise analyses using tensor-based morphometry (TBM) were conducted to verify regional assessments. Baseline brain metabolite levels, blood and cerebrospinal fluid biomarkers assessed by ELISA, and peripheral blood monocyte phenotypes measured by flow cytometry were examined as predictors of significant volumetric change.

RESULTS

Participants were 31 ± 8 years old. The estimated mean duration of infection at cART initiation was 15 days. Longitudinal analyses revealed reductions in volumes of putamen (P < 0.001) and caudate (P = 0.006). TBM confirmed significant atrophy in the putamen and caudate, and also in thalamic and hippocampal regions. In exploratory post-hoc analyses, higher baseline frequency of P-selectin glycoprotein ligand-1 (PSGL-1)-expressing total monocytes correlated with greater caudate volumetric decrease (ρ = 0.67, P = 0.017), whereas the baseline density of PSGL-1-expressing inflammatory (CD14CD16) monocytes correlated with putamen atrophy (ρ = 0.65, P = 0.022).

CONCLUSION

Suppressive cART initiated during AHI may not prevent brain atrophy. Volumetric decrease appears greater than expected age-related decline, although examination of longitudinal change in demographically similar HIV-uninfected Thai individuals is needed. Mechanisms underlying progressive HIV-related atrophy may include early activation and enhanced adhesive and migratory capacity of circulating monocyte populations.

Cognitive impairment severity in relation to signs of subclinical Wernicke's encephalopathy in HIV and alcoholism comorbidity

OBJECTIVES

The comorbidity of HIV infection and alcoholism (ALC) is prevalent. Wernicke's encephalopathy, a neurological disorder resulting from thiamine depletion, has been generally associated with alcoholism but has also been reported in HIV infection. This study examined whether subclinical Wernicke's encephalopathy signs could contribute to the heterogeneity of cognitive and motor deficits observed in individuals with both disease conditions (HIV+ALC).

DESIGN

Sixty-one HIV+ALC individuals and 59 controls were assessed on attention and working memory, production, immediate and delayed episodic memory, visuospatial abilities, and upper limb motor function.

METHODS

Using Caine criteria (dietary deficiency, oculomotor abnormality, cerebellar dysfunction, and altered mental state), HIV+ALC individuals were classified by subclinical Wernicke's encephalopathy risk factors.

RESULTS

Signs of subclinical Wernicke's encephalopathy were present in 20% of the HIV+ALC participants. For attention/working memory, delayed memory, and upper limb motor function, HIV+ALC Caine 2+ (i.e. meeting two or three criteria) demonstrated the most severe deficits, scoring lower than HIV+ALC Caine 1 (i.e. meeting one criterion), HIV+ALC Caine 0 (i.e. meeting no criteria), and controls.

CONCLUSION

The high prevalence of subclinical signs of Wernicke's encephalopathy and relevance to performance indicate that this condition should be considered in assessment of HIV-infected individuals, especially when alcoholism comorbidity is known or suspected. Above and beyond clinical factors, such as depression, alcoholism and HIV disease-related variables, AIDS, hepatitis C and drug history known to mediate neuropsychological performance, subclinical Wernicke's encephalopathy signs could partly explain the heterogeneity in patterns and severity of cognitive and motor impairments in HIV-infected individuals with alcoholism comorbidity.

Use of Neuroimaging to Inform Optimal Neurocognitive Criteria for Detecting HIV-Associated Brain Abnormalities

OBJECTIVE

Frascati international research criteria for HIV-associated neurocognitive disorders (HAND) are controversial; some investigators have argued that Frascati criteria are too liberal, resulting in a high false positive rate. Meyer et al. recommended more conservative revisions to HAND criteria, including exploring other commonly used methodologies for neurocognitive impairment (NCI) in HIV including the global deficit score (GDS). This study compares NCI classifications by Frascati, Meyer, and GDS methods, in relation to neuroimaging markers of brain integrity in HIV.

METHOD

Two hundred forty-one people living with HIV (PLWH) without current substance use disorder or severe (confounding) comorbid conditions underwent comprehensive neurocognitive testing and brain structural magnetic resonance imaging and magnetic resonance spectroscopy. Participants were classified using Frascati criteria versus Meyer criteria: concordant unimpaired [Frascati(Un)/Meyer(Un)], concordant impaired [Frascati(Imp)/Meyer(Imp)], or discordant [Frascati(Imp)/Meyer(Un)] which were impaired via Frascati criteria but unimpaired via Meyer criteria. To investigate the GDS versus Meyer criteria, the same groupings were utilized using GDS criteria instead of Frascati criteria.

RESULTS

When examining Frascati versus Meyer criteria, discordant Frascati(Imp)/Meyer(Un) individuals had less cortical gray matter, greater sulcal cerebrospinal fluid volume, and greater evidence of neuroinflammation (i.e., choline) than concordant Frascati(Un)/Meyer(Un) individuals. GDS versus Meyer comparisons indicated that discordant GDS(Imp)/Meyer(Un) individuals had less cortical gray matter and lower levels of energy metabolism (i.e., creatine) than concordant GDS(Un)/Meyer(Un) individuals. In both sets of analyses, the discordant group did not differ from the concordant impaired group on any neuroimaging measure.

CONCLUSIONS

The Meyer criteria failed to capture a substantial portion of PLWH with brain abnormalities. These findings support continued use of Frascati or GDS criteria to detect HIV-associated CNS dysfunction.

Low CD4 nadir linked to widespread cortical thinning in adults living with HIV

BACKGROUND

The history of immune suppression, especially CD4 nadir, has been shown to be a strong predictor of HIV-associated neurocognitive disorders (HAND). However, the potential mechanism of this association is not well understood.

METHODS

High resolution structural MRI images and neuropsychological data were obtained from fifty-nine HIV+ adults (mean age, 56.5 ± 5.8) to investigate the correlation between CD4 nadir and cortical thickness.

RESULTS

Low CD4 nadir was associated with widespread cortical thinning, especially in the frontal and temporal regions, and global mean cortical thickness correlated with CD4 nadir. In addition, worse global neurocognitive function was associated with bilateral frontal cortical thinning, and the association largely persisted (especially in the left frontal cortex) in the subset of participants who did not meet HAND criteria.

CONCLUSIONS

These results suggest that low CD4 nadir may be associated with widespread neural injury in the brain, especially in the frontal and temporal regions. The diffuse neural injury might contribute to the prevalence and the phenotypes of HAND, as well as the difficulty treating HAND due to a broad network of brain regions affected. Low CD4 nadir related neural injury to the frontal cortex might contribute to subtle neurocognitive impairment/decline, even in the absence of HAND diagnosis.

Circulating levels of ATP is a biomarker of HIV cognitive impairment

BACKGROUND

In developed countries, Human Immunodeficiency Virus type-1 (HIV-1) infection has become a chronic disease despite the positive effects of anti-retroviral therapies (ART), but still at least half of the HIV infected population shown signs of cognitive impairment. Therefore, biomarkers of HIV cognitive decline are urgently needed.

METHODS

We analyze the opening of one of the larger channels expressed by humans, pannexin-1 (Panx-1) channels, in the uninfected and HIV infected population (n = 175). We determined channel opening and secretion of intracellular second messengers released through the channel such as PGE₂ and ATP. Also, we correlated the opening of Panx-1 channels with the circulating levels of PGE₂ and ATP as well as cogntive status of the individuals analyzed.

FINDINGS

Here, we demonstrate that Panx-1 channels on fresh PBMCs obtained from uninfected individuals are closed and no significant amounts of PGE₂ and ATP are detected in the circulation. In contrast, in all HIV-infected individuals analyzed, even the ones under effective ART, a spontaneous opening of Panx-1 channels and increased circulating levels of PGE₂ and ATP were detected. Circulating levels of ATP were correlated with cognitive decline in the HIV-infected population supporting that ATP is a biomarker of cognitive disease in the HIV-infected population.

INTERPRETATION

We propose that circulating levels of ATP could predict CNS compromise and lead to the breakthroughs necessary to detect and prevent brain compromise in the HIV-infected population.

The impact of substance abuse on HIV-mediated neuropathogenesis in the current ART era

Approximately 37 million people worldwide are infected with human immunodeficiency virus (HIV). One highly significant complication of HIV infection is the development of HIV-associated neurocognitive disorders (HAND) in 15-55% of people living with HIV (PLWH), that persists even in the antiretroviral therapy (ART) era. The entry of HIV into the central nervous system (CNS) occurs within 4-8 days after peripheral infection. This establishes viral reservoirs that may persist even in the presence of ART. Once in the CNS, HIV infects resident macrophages, microglia, and at low levels, astrocytes. In response to chronic infection and cell activation within the CNS, viral proteins, inflammatory mediators, and host and viral neurotoxic factors produced over extended periods of time result in neuronal injury and loss, cognitive deficits and HAND. Substance abuse is a common comorbidity in PLWH and has been shown to increase neuroinflammation and cognitive disorders. Additionally, it has been associated with poor ART adherence, and increased viral load in the cerebrospinal fluid (CSF), that may also contribute to increased neuroinflammation and neuronal injury. Studies have examined mechanisms that contribute to neuroinflammation and neuronal damage in PLWH, and how substances of abuse exacerbate these effects. This review will focus on how substances of abuse, with an emphasis on methamphetamine (meth), cocaine, and opioids, impact blood brain barrier (BBB) integrity and transmigration of HIV-infected and uninfected monocytes across the BBB, as well as their effects on monocytes/macrophages, microglia, and astrocytes within the CNS. We will also address how these substances of abuse may contribute to HIV-mediated neuropathogenesis in the context of suppressive ART. Additionally, we will review the effects of extracellular dopamine, a neurotransmitter that is increased in the CNS by substances of abuse, on HIV neuropathogenesis and how this may contribute to neuroinflammation, neuronal insult, and HAND in PLWH with active substance use. Lastly, we will discuss some potential therapies to limit CNS inflammation and damage in HIV-infected substance abusers.

HIV infection and age effects on striatal structure are additive

The age of the HIV-infected population is increasing. Although many studies document gray matter volume (GMV) changes following HIV infection, GMV also declines with age. Findings have been inconsistent concerning interactions between HIV infection and age on brain structure. Effects of age, substance use, and inadequate viral suppression may confound identification of GMV serostatus effects using quantitative structural measures. In a cross-sectional study of HIV infection, including 97 seropositive and 84 seronegative, demographically matched participants, ages 30-70, we examined serostatus and age effects on GMV and neuropsychological measures. Ninety-eight percent of seropositive participants were currently treated with anti-retroviral therapies and all were virally suppressed. Gray, white, and CSF volumes were estimated using high-resolution T1-weighted MRI. Linear regression modeled effects of serostatus, age, education, comorbidities, and magnetic field strength on brain structure, using both a priori regions and voxel-based morphometry. Although seropositive participants exhibited significant bilateral decreases in striatal GMV, no serostatus effects were detected in the thalamus, hippocampus, or cerebellum. Age was associated with cortical, striatal, thalamic, hippocampal, and cerebellar GMV reductions. Effects of age and serostatus on striatal GMV were additive. Although no main effects of serostatus on neuropsychological performance were observed, serostatus moderated the relationship between pegboard performance and striatal volume. Both HIV infection and age were associated with reduced striatal volume. The lack of interaction of these two predictors suggests that HIV infection is associated with premature, but not accelerated, brain age. In serostatus groups matched on demographic and clinical variables, there were no observed differences in neuropsychological performance. Striatal GMV measures may be promising biomarker for use in studies of treated HIV infection.

Glutamine Antagonist JHU083 Normalizes Aberrant Glutamate Production and Cognitive Deficits in the EcoHIV Murine Model of HIV-Associated Neurocognitive Disorders

HIV-associated neurocognitive disorders (HAND) have been linked to dysregulation of glutamate metabolism in the central nervous system (CNS) culminating in elevated extracellular glutamate and disrupted glutamatergic neurotransmission. Increased glutamate synthesis via upregulation of glutaminase (GLS) activity in brain immune cells has been identified as one potential source of excess glutamate in HAND. However, direct evidence for this hypothesis in an animal model is lacking, and the viability of GLS as a drug target has not been explored. In this brief report, we demonstrate that GLS inhibition with the glutamine analogue 6-diazo-5-oxo-L-norleucine (DON) can reverse cognitive impairment in the EcoHIV-infected mouse model of HAND. However, due to peripheral toxicity DON is not amenable to clinical use in a chronic disease such as HAND. We thus tested JHU083, a novel, brain penetrant DON prodrug predicted to exhibit improved tolerability. Systemic administration of JHU083 reversed cognitive impairment in EcoHIV-infected mice similarly to DON, and simultaneously normalized EcoHIV-induced increases in cerebrospinal fluid (CSF) glutamate and GLS activity in microglia-enriched brain CD11b + cells without observed toxicity. These studies support the mechanistic involvement of elevated microglial GLS activity in HAND pathogenesis, and identify JHU083 as a potential treatment option. Graphical Abstract Please provide Graphical Abstract caption.Glutamine Antagonist JHU083 Normalizes Aberrant Glutamate Production and Cognitive Deficits in the EcoHIV Murine Model of HIV-Associated Neurocognitive Disorders .

Effects of comorbidity burden and age on brain integrity in HIV

OBJECTIVE

The influence of confounding neurocognitive comorbidities in people living with HIV (PLWH) on neuroimaging has not been systematically evaluated. We determined associations between comorbidity burden and brain integrity and examined the moderating effect of age on these relationships.

DESIGN

Observational, cross-sectional substudy of the CNS HIV Antiretroviral Therapy Effects Research cohort.

METHODS

A total of 288 PLWH (mean age = 44.2) underwent structural MRI and magnetic resonance spectroscopy as well as neurocognitive and neuromedical assessments. Consistent with Frascati criteria for HIV-associated neurocognitive disorders (HAND), neuromedical and neuropsychiatric comorbidity burden was classified as incidental (mild), contributing (moderate), or confounding (severe-exclusionary) to a diagnosis of HAND. Multiple regression modeling predicted neuroimaging outcomes as a function of comorbidity classification, age, and their interaction.

RESULTS

Comorbidity classifications were 176 incidental, 77 contributing, and 35 confounded; groups did not differ in HIV disease characteristics. Relative to incidental and contributing participants, confounded participants had less cortical gray matter and more abnormal white matter and ventricular cerebrospinal fluid, alongside more neuroinflammation (choline, myo-inositol) and less neuronal integrity (N-acetylaspartate). Older age exacerbated the impact of comorbidity burden: to a greater extent in the confounded group, older age was associated with more abnormal white matter (P = 0.017), less total white matter (P = 0.015), and less subcortical gray matter (P = 0.014).

CONCLUSION

Neuroimaging in PLWH reveals signatures associated with confounding neurocognitive conditions, emphasizing the importance of evaluating these among individuals with suspected HAND. Older age amplifies subcortical and white matter tissue injury, especially in PLWH with severe comorbidity burden, warranting increased attention to this population as it ages.

Validation of a Novel Multivariate Method of Defining HIV-Associated Cognitive Impairment

BACKGROUND

The optimum method of defining cognitive impairment in virally suppressed people living with HIV is unknown. We evaluated the relationships between cognitive impairment, including using a novel multivariate method (NMM), patient- reported outcome measures (PROMs), and neuroimaging markers of brain structure across 3 cohorts.

METHODS

Differences in the prevalence of cognitive impairment, PROMs, and neuroimaging data from the COBRA, CHARTER, and POPPY cohorts (total n = 908) were determined between HIV-positive participants with and without cognitive impairment defined using the HIV-associated neurocognitive disorders (HAND), global deficit score (GDS), and NMM criteria.

RESULTS

The prevalence of cognitive impairment varied by up to 27% between methods used to define impairment (eg, 48% for HAND vs 21% for NMM in the CHARTER study). Associations between objective cognitive impairment and subjective cognitive complaints generally were weak. Physical and mental health summary scores (SF-36) were lowest for NMM-defined impairment ( P < .05).There were no differences in brain volumes or cortical thickness between participants with and without cognitive impairment defined using the HAND and GDS measures. In contrast, those identified with cognitive impairment by the NMM had reduced mean cortical thickness in both hemispheres ( P < .05), as well as smaller brain volumes ( P < .01). The associations with measures of white matter microstructure and brain-predicted age generally were weaker.

CONCLUSION

Different methods of defining cognitive impairment identify different people with varying symptomatology and measures of brain injury. Overall, NMM-defined impairment was associated with most neuroimaging abnormalities and poorer self-reported health status. This may be due to the statistical advantage of using a multivariate approach.

Progressive brain atrophy in chronically infected and treated HIV+ individuals

Growing evidence points to persistent neurological injury in chronic HIV infection. It remains unclear whether chronically HIV-infected individuals on combined antiretroviral therapy (cART) develop progressive brain injury and impaired neurocognitive function despite successful viral suppression and immunological restoration. In a longitudinal neuroimaging study for the HIV Neuroimaging Consortium (HIVNC), we used tensor-based morphometry to map the annual rate of change of regional brain volumes (mean time interval 1.0 ± 0.5 yrs), in 155 chronically infected and treated HIV+ participants (mean age 48.0 ± 8.9 years; 83.9% male) . We tested for associations between rates of brain tissue loss and clinical measures of infection severity (nadir or baseline CD4+ cell count and baseline HIV plasma RNA concentration), HIV duration, cART CNS penetration-effectiveness scores, age, as well as change in AIDS Dementia Complex stage. We found significant brain tissue loss across HIV+ participants, including those neuro-asymptomatic with undetectable viral loads, largely localized to subcortical regions. Measures of disease severity, age, and neurocognitive decline were associated with greater atrophy. Chronically HIV-infected and treated individuals may undergo progressive brain tissue loss despite stable and effective cART, which may contribute to neurocognitive decline. Understanding neurological complications of chronic infection and identifying factors associated with atrophy may help inform strategies to maintain brain health in people living with HIV.

Mapping abnormal subcortical neurodevelopment in a cohort of Thai children with HIV

Alterations in subcortical brain structures have been reported in adults with HIV and, to a lesser extent, pediatric cohorts. The extent of longitudinal structural abnormalities in children with perinatal HIV infection (PaHIV) remains unclear. We modeled subcortical morphometry from whole brain structural magnetic resonance imaging (1.5 T) scans of 43 Thai children with PaHIV (baseline age = 11.09±2.36 years) and 50 HIV- children (11.26±2.80 years) using volumetric and surface-based shape analyses. The PaHIV sample were randomized to initiate combination antiretroviral treatment (cART) when CD4 counts were 15-24% (immediate: n = 22) or when CD4 < 15% (deferred: n = 21). Follow-up scans were acquired approximately 52 weeks after baseline. Volumetric and shape descriptors capturing local thickness and surface area dilation were defined for the bilateral accumbens, amygdala, putamen, pallidum, thalamus, caudate, and hippocampus. Regression models adjusting for clinical and demographic variables examined between and within group differences in morphometry associated with HIV. We assessed whether baseline CD4 count and cART status or timing associated with brain maturation within the PaHIV group. All models were adjusted for multiple comparisons using the false discovery rate. A pallidal subregion was significantly thinner in children with PaHIV. Regional thickness, surface area, and volume of the pallidum was associated with CD4 count in children with PaHIV. Longitudinal morphometry was not associated with HIV or cART status or timing, however, the trajectory of the left pallidum volume was positively associated with baseline CD4 count. Our findings corroborate reports in adult cohorts demonstrating a high predilection for HIV-mediated abnormalities in the basal ganglia, but suggest the effect of stable PaHIV infection on morphological aspects of brain development may be subtle.

Structural Brain Abnormalities in Successfully Treated HIV Infection: Associations With Disease and Cerebrospinal Fluid Biomarkers

Background

Brain structural abnormalities have been reported in persons living with human immunodeficiency virus (HIV; PLWH) who are receiving suppressive combination antiretroviral therapy (cART), but their pathophysiology remains unclear.

Methods

We investigated factors associated with brain tissue volumes and white matter microstructure (fractional anisotropy) in 134 PLWH receiving suppressive cART and 79 comparable HIV-negative controls, aged ≥45 years, from the Comorbidity in Relation to AIDS cohort, using multimodal neuroimaging and cerebrospinal fluid biomarkers.

Results

Compared with controls, PLWH had lower gray matter volumes (-13.7 mL; 95% confidence interval, -25.1 to -2.2) and fractional anisotropy (-0.0073; 95% confidence interval, -.012 to -.0024), with the largest differences observed in those with prior clinical AIDS. Hypertension and the soluble CD14 concentration in cerebrospinal fluid were associated with lower fractional anisotropy. These associations were independent of HIV serostatus (Pinteraction = .32 and Pinteraction = .59, respectively) and did not explain the greater abnormalities in brain structure in relation to HIV infection.

Conclusions

The presence of lower gray matter volumes and more white matter microstructural abnormalities in well-treated PLWH partly reflect a combination of historical effects of AIDS, as well as the more general influence of systemic factors, such as hypertension and ongoing neuroinflammation. Additional mechanisms explaining the accentuation of brain structure abnormalities in treated HIV infection remain to be identified.

Semaphorin4A causes loss of mature oligodendrocytes and demyelination in vivo

Background

Inappropriate contact between the immune system and the central nervous system is thought to be a cause of demyelination. We previously reported the ability of the class IV semaphorin, Semaphorin4A (Sema4A), to induce apoptosis in human oligodendrocytes; however, these results have yet to be translated to an in vivo setting. Importantly, HIV-associated neurocognitive disorder remains a significant complication for patients on combined anti-retroviral therapy, with white matter damage seen on MRI.

Methods

Human cerebrospinal fluid and serum was assayed for Sema4A using a Sema4A-specific ELISA. Wild-type mice were injected with Sema4A via stereotaxic infusion. Data was assessed for significance using unpaired t tests, comparing the corpus callosum of PBS-injected mice versus Sema4A-injected mice.

Results

Here, we demonstrate elevated levels of Sema4A in the cerebrospinal fluid and serum of people with HIV infection. Furthermore, we demonstrate that direct injection of Sema4A into the corpus callosum of mice results in loss of myelin architecture and decreased myelin, concomitant with apoptosis of mature myelinating oligodendrocytes. Sema4A injection also causes increased activation of microglia.

Conclusions

Taken together, our data further establish Sema4A as a potentially significant mediator of demyelinating diseases and a direct connection between the immune system and oligodendrocytes.