Relative sensitivity of magnetic resonance spectroscopy and quantitative magnetic resonance imaging to cognitive function among nondemented individuals infected with HIV

Brain N -acetyl-aspartyl-glutamate is associated with cognitive function in older virally suppressed people with HIV

OBJECTIVES

Cognitive impairment persists in virally suppressed people with HIV (VS-PWH) especially in higher order domains. One cortical circuit, linked to these domains, is regulated by N -acetyl-aspartyl glutamate (NAAG), the endogenous agonist of the metabotropic glutamate receptor 3. The enzyme glutamate carboxypeptidase II (GCPII) catabolizes NAAG and is upregulated in aging and disease. Inhibition of GCPII increases brain NAAG and improves learning and memory in rodent and primate models.

DESIGN

As higher order cognitive impairment is present in VS-PWH, and NAAG has not been investigated in earlier magnetic resonance spectroscopy studies (MRS), we investigated if brain NAAG levels measured by MRS were associated with cognitive function.

METHODS

We conducted a retrospective analysis of 7-Tesla MRS data from a previously published study on cognition in older VS-PWH. The original study did not separately quantify NAAG, therefore, work for this report focused on relationships between regional NAAG levels in frontal white matter (FWM), left hippocampus, left basal ganglia and domain-specific cognitive performance in 40 VS-PWH after adjusting for confounds. Participants were older than 50 years, negative for affective and neurologic disorders, and had no prior 3-month psychoactive-substance use.

RESULTS

Higher NAAG levels in FWM were associated with better attention/working memory. Higher left basal ganglia NAAG related to better verbal fluency. There was a positive relationship between hippocampal NAAG and executive function which lost significance after correction for confounds.

CONCLUSION

These data suggest brain NAAG serves as a biomarker of cognition in VS-PWH. Pharmacological modulation of brain NAAG warrants investigation as a therapeutic approach for cognitive deficits in VS-PWH.

Update on Central Nervous System Effects of HIV in Adolescents and Young Adults

PURPOSE OF REVIEW

: Behaviorally acquired (non-perinatal) HIV infection during adolescence and young adulthood occurs in the midst of key brain developmental processes such as frontal lobe neuronal pruning and myelination of white matter, but we know little about the effects of new infection and therapy on the developing brain.

RECENT FINDINGS

Adolescents and young adults account for a disproportionately high fraction of new HIV infections each year. Limited data exist regarding neurocognitive performance in this age group, but suggest impairment is at least as prevalent as in older adults, despite lower viremia, higher CD4 + T cell counts, and shorter durations of infection in adolescents/young adults. Neuroimaging and neuropathologic studies specific to this population are underway. The full impact of HIV on brain growth and development in youth with behaviorally acquired HIV has yet to be determined; it must be investigated further to develop future targeted treatment and mitigation strategies.

Identifying subtypes of HIV/AIDS-related symptoms in China using latent profile analysis and symptom networks

The identification of subgroups of people living with HIV in China based on the severity of symptom clusters and individual symptoms is crucial to determine group-specific symptom management strategies. Participants reported 27 highly prevalent HIV/AIDS-related symptoms. Latent profile analysis based on symptom severity was used to identify person-centered subtypes of HIV/AIDS-related symptoms. Symptom networks were compared among subgroups identified by latent profile analysis. A total of 2927 eligible people living with HIV (PWH) were included in the analysis. Five profiles were identified: "Profile 1: all low symptom severity" (n₂ = 2094, 71.54%), "Profile 2: medium symptom severity with syndemic conditions" (n₃ = 109, 3.72%), "Profile 3: medium symptom severity with low functional status" (n₁ = 165, 5.64%), "Profile 4: medium symptom severity in transitional period" (n₄ = 448, 15.31%), and "Profile 5: all high symptom severity" (n₅ = 111, 3.79%). Except for Profile 1 and Profile 5, the symptom severity was similar among the other three profiles. Profiles 1 (2.09 ± 0.52) and 4 (2.44 ± 0.66) had the smallest ∑s values, and Profiles 2 (4.38 ± 1.40) and 5 (4.39 ± 1.22) had the largest ∑s values. Our study demonstrates the need for health care professionals to provide PWH with group-specific symptom management interventions based on five profiles to improve their physical and psychological well-being. Future studies should be conducted in different contexts using different symptom checklists to further validate our results.

Altered Glymphatic System in Middle-Aged cART-Treated Patients With HIV: A Diffusion Tensor Imaging Study

Objective:

The brain relies on the glymphatic system to clear metabolic wastes and maintain brain homeostasis to fulfill its functions better. Yet, the complexity of the glymphatic flow and clearance and its changes in HIV infection and its role in neurocognitive dysfunction remain poorly understood. This study aims to explore the impact of HIV and combination antiretroviral therapy (cART) on the glymphatic system and establish a potential biomarker of HIV-associated neurocognitive disorders (HAND).

Methods

Here, we examined the glymphatic profiles of middle-aged virosuppressed patients with HIV (n = 27) receiving cART over 1–6 years and healthy controls (n = 28) along the perivascular space (PVS) using diffusion tensor image analysis along the perivascular space (ALPS) with guided and unguided approaches. We later combined data from these analyses to investigate MRI glymphatic correlates of cognitive impairment and other clinical tests of HIV (CD4+ T-cell counts and CD4+/CD8+ ratio).

Results

We found that glymphatic function as measured by the ALPS index increased significantly in the right and left PVSs of patients with HIV having cART. On antiretroviral therapy, a changing pattern in glymphatic clearance function in patients with HIV having cART correlated with attention and working memory. Duration on cART was also associated with cognitive performances of abstract and executive function and learning and memory.

Conclusion

These findings provide MRI evidence of the presence of HIV-induced changes in the glymphatic flow and clearance, which might underlie cognitive impairment among patients with HIV having cART. An increase in the glymphatic activity might reflect a compensatory mechanism to regulate microenvironment homeostasis compromised by HIV. This compensation might be necessary to maintain the proper functioning of the brain while coping with HIV pathology. These findings also shed light on the clinical importance of evaluating glymphatic function based on the ALPS index and suggest that improving the glymphatic system may serve as an alternative therapeutic strategy for HAND.

MR spectroscopy in HIV associated neurocognitive disorder in the era of cART: a review

Neuroimaging has been a critical tool for understanding the neuropathological underpinnings observed in HIV. The pathophysiology of HAND is chiefly driven by neuroinflammation. Despite adhering to cART, low levels of viraemia probably persist in the brain in some patients leading to chronic immune activation with resultant neuroinflammation and consequent neuronal injury. MR spectroscopy has been widely used as a biomarker for the presence and severity of HAND in several studies. By studying the MRS signatures, it is possible to characterise the presence of neuroinflammation and neural injury. Furthermore, metabolite concentrations measured by MRS could be used as a quantitative indicator of HIV cerebral involvement, thereby affording the opportunity to assess the efficacy of cART in HAND. However, currently there are three significant limitations in the MRS HIV research literature: the relative paucity of prospective studies, the small number of regions of interrogation due to current methodology (single voxel MRS), and the evolving understanding of the impact of co-morbidities (e.g. ageing, mood disorders, alcoholism etc.) on MRS measurements. This review critically addresses the current literature of MRS studies in people living with HIV (PWH) with HAND to determine its value, especially in the context of the current cART era. In addition, we discuss technical considerations related to the disease and the future direction in HAND using MRS.

Cognitive Performance and Neuro-Metabolites in HIV Using 3T Magnetic Resonance Spectroscopy: A Cross-Sectional Study from India

BACKGROUND

Cognitive impairment in patients with human immunodeficiency virus (HIV) is associated with higher morbidity. The prevalence of the metabolite changes in the brain associated with cognitive impairment in anti-retroviral therapy naïve patients with HIV is unknown.

OBJECTIVE

To estimate the prevalence of the neurometabolites associated with cognitive impairment in antiretroviral therapy (ART) naïve patients with HIV.

METHODS

We conducted a cross-sectional study among ART naïve patients with HIV aged 18-50 years in a tertiary care center in India. Cognition was tested using the Post Graduate Institute battery of brain dysfunction across five domains; memory, attention-information processing, abstraction executive, complex perceptual, and simple motor skills. We assessed the total N-acetyl aspartyl (tNAA), creatine (tCr) and glutamate + glutamine (Glx) using 3T magnetic resonance spectroscopy. Cognitive impairment was defined as an impairment in ≥2 domains.

RESULTS

Among 43 patients eligible for this study, the median age was 32 years (IQR 29, 40) and 30% were women. Median CD4 count and viral load were 317 cells/μL (IQR 157, 456) and 9.3 copies/ μL (IQR 1.4, 38), respectively. Impairment in at least one cognitive domain was present in 32 patients (74.4%). Impairment in simple motor skills and memory was present in 46.5% and 44% of patients, respectively. Cognitive impairment, defined by impairment in ≥2 domains, was found in 22 (51.2%) patients. There was a trend towards higher concentration of tNAA (7.3 vs. 7.0 mmol/kg), tGlx (9.1 vs. 8.2 mmol/kg), and tCr (5.5 vs. 5.2 mmol/kg) in the frontal lobe of patients with cognitive impairment vs. without cognitive impairment but it did not reach statistical significance (p>0.05 for all). There was no difference in the concentration of these metabolites in the two groups in the basal ganglia.

CONCLUSION

There is a high prevalence of cognitive impairment in ART naïve patients with HIV. There is no difference in metabolites in patients with or without cognitive impairment. Further studies, with longitudinal follow-up are required to understand the underlying pathophysiological mechanisms.

Neuroimaging and Cognitive Evidence for Combined HIV-Alcohol Effects on the Central Nervous System: A Review

Alcohol use disorder (AUD) among people living with HIV (PLWH) is a significant public health concern. Despite the advent of effective antiretroviral therapy, up to 50% of PLWH still experience worsened neurocognition, which comorbid AUD exacerbates. We report converging lines of neuroimaging and neuropsychological evidence linking comorbid HIV/AUD to dysfunction in brain regions linked to executive function, learning and memory, processing speed, and motor control, and consequently to impairment in daily life. The brain shrinkage, functional network alterations, and brain metabolite disruption seen in individuals with HIV/AUD have been attributed to several interacting pathways: viral proteins and EtOH are directly neurotoxic and exacerbate each other's neurotoxic effects; EtOH reduces antiretroviral adherence and increases viral replication; AUD and HIV both increase gut microbial translocation, promoting systemic inflammation and HIV transport into the brain by immune cells; and HIV may compound alcohol's damaging effects on the liver, further increasing inflammation. We additionally review the neurocognitive effects of aging, Hepatitis C coinfection, obesity, and cardiovascular disease, tobacco use, and nutritional deficiencies, all of which have been shown to compound cognitive changes in HIV, AUD, and in their comorbidity. Finally, we examine emerging questions in HIV/AUD research, including genetic and cognitive protective factors, the role of binge drinking in HIV/AUD-linked cognitive decline, and whether neurocognitive and brain functions normalize after drinking cessation.

Alzheimer's disease-like perturbations in HIV-mediated neuronal dysfunctions: understanding mechanisms and developing therapeutic strategies

Excessive exposure to toxic substances or chemicals in the environment and various pathogens, including viruses and bacteria, is associated with the onset of numerous brain abnormalities. Among them, pathogens, specifically viruses, elicit persistent inflammation that plays a major role in Alzheimer's disease (AD) as well as dementia. AD is the most common brain disorder that affects thought, speech, memory and ability to execute daily routines. It is also manifested by progressive synaptic impairment and neurodegeneration, which eventually leads to dementia following the accumulation of Aβ and hyperphosphorylated Tau. Numerous factors contribute to the pathogenesis of AD, including neuroinflammation associated with pathogens, and specifically viruses. The human immunodeficiency virus (HIV) is often linked with HIV-associated neurocognitive disorders (HAND) following permeation through the blood-brain barrier (BBB) and induction of persistent neuroinflammation. Further, HIV infections also exhibited the ability to modulate numerous AD-associated factors such as BBB regulators, members of stress-related pathways as well as the amyloid and Tau pathways that lead to the formation of amyloid plaques or neurofibrillary tangles accumulation. Studies regarding the role of HIV in HAND and AD are still in infancy, and potential link or mechanism between both is not yet established. Thus, in the present article, we attempt to discuss various molecular mechanisms that contribute to the basic understanding of the role of HIV-associated neuroinflammation in AD and HAND. Further, using numerous growth factors and drugs, we also present possible therapeutic strategies to curb the neuroinflammatory changes and its associated sequels.

Effect of human immunodeficiency virus on the brain: A review

Thirty million people are infected with human immunodeficiency virus (HIV) worldwide, and HIV-associated neurocognitive disorder (HAND) is one of the most common comorbidities of HIV. However, the effect of HIV on the brain has not been fully investigated. This article aimed to review the changes to the brain due to HIV in terms of atrophy, diffusion changes, and hyperintensities. Studies have observed significant atrophy in subcortical gray matter, as well as in cortical white and gray matter. Moreover, the ventricles enlarge, and the sulci widen. Although HIV causes changes to the white and gray matter of the brain, few diffusion tensor imaging studies have investigated the changes to gray matter integrity. White and gray matter hyperintensities have frequently been observed in HIV-positive individuals, with the subcortical gray matter (caudate nucleus and putamen) and periventricular white matter frequently affected. In conclusion, subcortical gray matter is the first brain region to be affected and is affected most severely. Additionally, this review highlights the gaps in the literature, since the effect of HIV on the brain is not fully known. Future studies should continue to investigate the effect of HIV on the brain in different stages of the disease, and alternate therapies should be developed since highly active antiretroviral therapy is currently ineffective at treating HAND.

MRS suggests multi-regional inflammation and white matter axonal damage at 11 years following perinatal HIV infection

The neurological changes in children living with perinatal HIV (PHIV) on antiretroviral therapy (ART) can be studied at a metabolic level through proton magnetic resonance spectroscopy. While previous studies in children have largely focused on individual metabolite changes, investigating patterns within and across regions of interest can aid in identifying metabolic markers of HIV infection. In this study 76 children with PHIV from the Children with HIV Early AntiRetroviral (CHER) trial, 30 children who were HIV-exposed-uninfected (HEU) and 30 children who were HIV-unexposed (HU), were scanned at the age of 11.6 (sd = 0.3) years using a 3 T Skyra scanner. Metabolite concentrations were quantified within the basal ganglia (BG), midfrontal gray matter (MFGM) and peritrigonal white matter (PWM), comparing levels between HIV status groups using linear regression. Factor analysis and logistic regression were performed to identify metabolic patterns characteristic of HIV infection within and across the regions of interest. In the BG region we observed restored metabolic activity in children with PHIV and children who were HEU, despite differences being previously observed at younger ages, suggesting that treatment may effectively reduce the effects of HIV infection and exposure. Elevated MFGM choline levels in children with PHIV are indicative of inflammation. Further, we observed reduced N-acetyl-aspartate (NAA) in the PWM of children with PHIV and children who were HEU, indicating possible axonal damage. Lower levels of PWM creatine in children with PHIV suggest that this may not be a valid reference metabolite in HIV studies. Finally, factor scores for a cross-regional inflammatory factor and a PWM axonal factor, driven by PWM NAA and creatine levels, distinguished children with PHIV from children without HIV (HEU and HU) at 11 years. Therefore, the effects of perinatal HIV infection and exposure continue to be seen at 11 years despite early treatment.

Independent and Combined Effects of Nicotine or Chronic Tobacco Smoking and HIV on the Brain: A Review of Preclinical and Clinical Studies

Tobacco smoking is highly prevalent among HIV-infected individuals. Chronic smokers with HIV showed greater cognitive deficits and impulsivity, and had more psychopathological symptoms and greater neuroinflammation than HIV non-smokers or smokers without HIV infection. However, preclinical studies that evaluated the combined effects of HIV-infection and tobacco smoking are scare. The preclinical models typically used cell cultures or animal models that involved specific HIV viral proteins or the administration of nicotine to rodents. These preclinical models consistently demonstrated that nicotine had neuroprotective and anti-inflammatory effects, leading to cognitive enhancement. Although the major addictive ingredient in tobacco smoking is nicotine, chronic smoking does not lead to improved cognitive function in humans. Therefore, preclinical studies designed to unravel the interactive effects of chronic tobacco smoking and HIV infection are needed. In this review, we summarized the preclinical studies that demonstrated the neuroprotective effects of nicotine, the neurotoxic effects of the HIV viral proteins, and the scant literature on nicotine or tobacco smoke in HIV transgenic rat models. We also reviewed the clinical studies that evaluated the neurotoxic effects of tobacco smoking, HIV infection and their combined effects on the brain, including studies that evaluated the cognitive and behavioral assessments, as well as neuroimaging measures. Lastly, we compared the different approaches between preclinical and clinical studies, identified some gaps and proposed some future directions. Graphical abstract Independent and combined effects of HIV and tobacco/nicotine. Left top and bottom panels: Both clinical studies of HIV infected persons and preclinical studies using viral proteins in vitro or in vivo in animal models showed that HIV infection could lead to neurotoxicity and neuroinflammation. Right top and bottom panels: While clinical studies of tobacco smoking consistently showed deleterious effects of smoking, clinical and preclinical studies that used nicotine show mild cognitive enhancement, neuroprotective and possibly anti-inflammatory effects. In the developing brain, however, nicotine is neurotoxic. Middle overlapping panels: Clinical studies of persons with HIV who were smokers typically showed additive deleterious effects of HIV and tobacco smoking. However, in the preclinical studies, when nicotine was administered to the HIV-1 Tg rats, the neurotoxic effects of HIV were attenuated, but tobacco smoke worsened the inflammatory cascade.

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

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

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.

Systemic Mitochondrial Oxidative Phosphorylation Protein Levels Correlate with Neuroimaging Measures in Chronically HIV-Infected Individuals

Few studies have examined systemic mitochondrial function in conjunction with brain imaging in human immunodeficiency virus (HIV) disease. Oxidative phosphorylation enzyme protein levels of peripheral blood mononuclear cells were measured in association with neuroimaging indices in 28 HIV+ individuals. T1-weighted magnetic resonance imaging yielded volumes of seven brain regions of interest; diffusion tensor imaging determined fractional anisotropy (FA) and mean diffusivity (MD) in the corpus callosum (CC). Higher nicotinamide adenine dinucleotide dehydrogenase levels correlated with lower volumes of thalamus (p = .005) and cerebral white matter (p = .049) and, in the CC, with lower FA (p = .011, body; p = .005, genu; p = .009, total CC) and higher MD (p = .023, body; p = .035, genu; p = .019, splenium; p = .014, total CC). Greater cytochrome c oxidase levels correlated with lower thalamic (p = .034) and cerebellar gray matter (p = .021) volumes. The results indicate that systemic mitochondrial cellular bioenergetics are associated with brain health in HIV.

HIV-1 infection alters energy metabolism in the brain: Contributions to HIV-associated neurocognitive disorders

The brain is particularly sensitive to changes in energy supply. Defects in glucose utilization and mitochondrial dysfunction are hallmarks of nearly all neurodegenerative diseases and are also associated with the cognitive decline that occurs as the brain ages. Chronic neuroinflammation driven by glial activation is commonly implicated as a contributing factor to neurodegeneration and cognitive impairment. Human immunodeficiency virus-1 (HIV-1) disrupts normal brain homeostasis and leads to a spectrum of HIV-associated neurocognitive disorders (HAND). HIV-1 activates stress responses in the brain and triggers a state of chronic neuroinflammation. Growing evidence suggests that inflammatory processes and bioenergetics are interconnected in the propagation of neuronal dysfunction. Clinical studies of people living with HIV and basic research support the notion that HIV-1 creates an environment in the CNS that interrupts normal metabolic processes at the cellular level to collectively alter whole brain metabolism. In this review, we highlight reports of abnormal brain metabolism from clinical studies and animal models of HIV-1. We also describe diverse CNS cell-specific changes in bioenergetics associated with HIV-1. Moreover, we propose that attention should be given to adjunctive therapies that combat sources of metabolic dysfunction as a mean to improve and/or prevent neurocognitive impairments.

Is treated HIV infection still toxic to the brain?

Clinically apparent HIV infection, accompanied by CNS opportunistic infections and HIV encephalopathy, was often associated with profound structural and functional brain effects prior to the introduction of anti-retroviral therapy (ART). With treatment, HIV structural and functional brain effects are smaller and have not been as easily detected. With near complete elimination of CNS opportunistic infections, the HIV neuroimaging research community now grapples with the problem of detecting subtler structural and functional changes against a background of persisting confounds, such as comorbidities and clinical features common in the HIV infected population. This situation also raises the question of whether imaging measure changes that are reported as HIV brain effects are purely related to viral infection, rather than originating from confounding effects that might include age, substance use, hepatitis C coinfection, cerebrovascular risk factors, ART, premorbid cognitive skills and illness duration. In addition to cohort characteristics, variation in image acquisition and analysis techniques may also contribute to study outcome heterogeneity. We review the potential effects of these confounds on detection of HIV infection effects and discuss strategies to avoid or mitigate the effects of these confounds. We then present a systematic approach to measurement, design and analysis in HIV neuroimaging studies, combining both experimental and statistical control techniques to determine if HIV infection effects persist, fluctuate or worsen in groups achieving viral suppression from ART.

Neurocognitive Phenotyping of HIV in the Era of Antiretroviral Therapy

PURPOSE OF REVIEW

This paper examines the theoretical and empirical basis for neurocognitive phenotyping of HIV.

RECENT FINDINGS

The pattern of neurocognitive symptoms associated with HIV has traditionally been referred to as a "subcortical" phenotype. Recent concern has been raised that the neurocognitive phenotype in the post-ART era has changed to reflect the addition of cortical features, suggestive of synergistic age-related neurodegeneration. Empirical evidence reviewed in this paper suggests that, when present, HIV-related neurocognitive impairment in the post-ART era remains subcortical in nature, regardless of advanced age or treatment status. Persistent neurocognitive impairment among virally suppressed individuals may reflect a combination of HIV disease factors, pre-existing risk factors, and/or emergent health comorbidities such as subcortical ischemic vascular disease in older people living with HIV. An entrenchment of the subcortical neurocognitive phenotype of HIV appears to be unfolding in the post-ART era. Whether new neurocognitive subtypes of HIV exist in the current era requires additional research utilizing harmonized test protocols and advanced computational methods capable of deep phenotyping. Recommendations from other neurological disorders are provided.

HIV brain latency as measured by CSF BcL11b relates to disrupted brain cellular energy in virally suppressed HIV infection

OBJECTIVE

We investigated whether HIV brain latency was associated with brain injury in virally suppressed HIV infection.

DESIGN

Observational cross-sectional and longitudinal study.

METHODS

The study included 26 virally suppressed HIV-infected men (61.5% with HIV-associated neurocognitive disorder) who undertook cerebrospinal fluid (CSF) analyses at baseline. They also completed a proton magnetic resonance spectroscopy (1H MRS) and neuropsychological assessments at baseline and 18 months. To quantify whether there was residual brain HIV transcription, we measured CSF HIV-tat. As an HIV brain latency biomarker, we used concentrations of CSF BcL11b - a microglia transcription factor that inhibits HIV transcription. Concurrently, we assessed neuroinflammation with CSF neopterin, neuronal injury with CSF neurofilament light-chain (NFL), and in-vivo neurochemistry with 1H MRS of N-acetyl aspartate (NAA), choline (Cho), creatine, myo-inositol (MI), glutamine/glutamate (Glx) in the frontal white matter (FWM), posterior cingulate cortex (PCC), and caudate nucleus area.

RESULTS

Baseline adjusted regression models for neopterin, NFL, and tat showed that a higher CSF BcL11b was consistently associated with lower FWM creatine (when adjusted for neopterin: β = -0.30, P = 0.15; when adjusted for NFL: β = -0.47, P = 0.04; and when adjusted for tat: β = -0.47, P = 0.02). In longitudinal analyses, we found no time effect, but a consistent BcL11b altering effect on FWM creatine. The effect reached a significant moderate effect size range when corrected for CSF NFL (β = -0.36, P = 0.02) and CSF tat (β = -0.34, P = 0.02).

CONCLUSIONS

Reduced frontal white matter total creatine may indicate subclinical HIV brain latency-related injury. H MRS may offer a noninvasive option to measure HIV brain latency.

White matter damage, neuroinflammation, and neuronal integrity in HAND

HIV-associated neurocognitive disorders (HANDs) persist even with virologic suppression on combination antiretroviral therapy (cART), and the underlying pathophysiological mechanisms are not well understood. We performed structural magnetic resonance imaging and MR spectroscopy (MRS) in HIV+ individuals without major neurocognitive comorbidities. Study participants were classified as neurocognitively unimpaired (NU), asymptomatic (ANI), mild neurocognitive disorder (MND), or HIV-associated dementia (HAD). Using structural MRI, we measured volumes of cortical and subcortical gray matter and total and abnormal white matter (aWM). Using single-voxel MRS, we estimated metabolites in frontal gray matter (FGM) and frontal white matter (FWM) and basal ganglia (BG) regions. Adjusted odds ratios were used to compare HAND to NU. Among 253 participants, 40% met HAND criteria (21% ANI, 15% MND, and 4% HAD). Higher risk of HAND was associated with more aWM. Both HAD and MND also had smaller gray and white matter volumes than NU. Among individuals with undetectable plasma HIV RNA, structural volumetric findings were similar to the overall sample. MND had lower FWM creatine and higher FGM choline relative to NU, whereas HAD and ANI had lower BG N-acetyl aspartate relative to NU. In the virologically suppressed subgroup, however, ANI and MND had higher FGM choline compared to NU. Overall, HAND showed specific alterations (more aWM and inflammation; less gray matter volume and lower NAA). Some MR measures differentiated less severe subtypes of HAND from HAD. These MR alterations may represent legacy effects or accumulating changes, possibly related to medical comorbidities, antiretroviral therapy, or chronic effects of HIV brain infection.

Structural Neuroimaging and Neuropsychologic Signatures in Children With Vertically Acquired HIV

BACKGROUND

Children with vertically acquired HIV exhibit persistent cognitive impairments, yet the corresponding neuroimaging signature of vertical infection remains unclear.

METHODS

Fifty healthy control children and 51 vertically infected children were included in the study. The HIV-infected group consisted of survivors who had not received antiretroviral therapy at birth. The HIV-infected group averaged 11.4 (2.5) years of age, with a median CD4 count of 683 cells/mm(3). Most (71%) of the HIV-infected children were on antiretroviral therapy for a median of 34 months (range: 33-42) with HIV RNA <40 copies/mL in 89% of the sample. The HIV-uninfected group averaged 10.6 (2.6) years of age. Magnetic resonance imaging was acquired to determine volumes of the caudate, putamen, thalamus, pallidum, hippocampus, nucleus accumbens, total white matter, total gray matter and cortical gray matter. Correlational analyses examined the degree of shared variance between brain volumes and both cognitive performances and laboratory markers of disease activity (T cells and plasma viral load).

RESULTS

HIV-infected children exhibited larger volumes of the caudate, nucleus accumbens, total gray matter and cortical gray matter when compared with the controls. Volumetric differences were predominately evident in children under 12 years of age. HIV-infected children performed worse than controls on most neuropsychologic tests, though neither cognitive performances nor laboratory markers corresponded to brain volumes in the HIV-infected children.

CONCLUSIONS

Outcomes of the present study suggest abnormal brain maturation among HIV-infected pediatric survivors. Longitudinal studies of brain integrity and related resilience factors are needed to determine the impact of neuroimaging abnormalities on psychosocial function in pediatric HIV.

The Aging Brain With HIV Infection: Effects of Alcoholism or Hepatitis C Comorbidity

As successfully treated individuals with Human Immunodeficiency Virus (HIV)-infected age, cognitive and health challenges of normal aging ensue, burdened by HIV, treatment side effects, and high prevalence comorbidities, notably, Alcohol Use Disorders (AUD) and Hepatitis C virus (HCV) infection. In 2013, people over 55 years old accounted for 26% of the estimated number of people living with HIV (~1.2 million). The aging brain is increasingly vulnerable to endogenous and exogenous insult which, coupled with HIV infection and comorbid risk factors, can lead to additive or synergistic effects on cognitive and motor function. This paper reviews the literature on neuropsychological and in vivo Magnetic Resonance Imaging (MRI) evaluation of the aging HIV brain, while also considering the effects of comorbidity for AUD and HCV.

Neural response to working memory demand predicts neurocognitive deficits in HIV

Human immunodeficiency virus (HIV) continues to have adverse effects on cognition and the brain in many infected people, despite a reduced incidence of HIV-associated dementia with combined antiretroviral therapy (cART). Working memory is often affected, along with attention, executive control, and cognitive processing speed. Verbal working memory (VWM) requires the interaction of each of the cognitive component processes along with a phonological loop for verbal repetition and rehearsal. HIV-related functional brain response abnormalities during VWM are evident in functional MRI (fMRI), though the neural substrate underlying these neurocognitive deficits is not well understood. The current study addressed this by comparing 24 HIV+ to 27 demographically matched HIV-seronegative (HIV-) adults with respect to fMRI activation on a VWM paradigm (n-back) relative to performance on two standardized tests of executive control, attention and processing speed (Stroop and Trail Making A-B). As expected, the HIV+ group had deficits on these neurocognitive tests compared to HIV- controls, and also differed in neural response on fMRI relative to neuropsychological performance. Reduced activation in VWM task-related brain regions on the 2-back was associated with Stroop interference deficits in HIV+ but not with either Trail Making A or B performance. Activation of the posterior cingulate cortex (PCC) of the default mode network during rest was associated with Hopkins Verbal Learning Test-2 (HVLT-2) learning in HIV+. These effects were not observed in the HIV- controls. Reduced dynamic range of neural response was also evident in HIV+ adults when activation on the 2-back condition was compared to the extent of activation of the default mode network during periods of rest. Neural dynamic range was associated with both Stroop and HVLT-2 performance. These findings provide evidence that HIV-associated alterations in neural activation induced by VWM demands and during rest differentially predict executive-attention and verbal learning deficits. That the Stroop, but not Trail Making was associated with VWM activation suggests that attentional regulation difficulties in suppressing interference and/or conflict regulation are a component of working memory deficits in HIV+ adults. Alterations in neural dynamic range may be a useful index of the impact of HIV on functional brain response and as a fMRI metric in predicting cognitive outcomes.

Chronic low-level expression of HIV-1 Tat promotes a neurodegenerative phenotype with aging

The widespread use of combinational antiretroviral therapies (cART) in developed countries has changed the course of Human Immunodeficiency Virus (HIV) infection from an almost universally fatal disease to a chronic infection for the majority of individuals. Although cART has reduced the severity of neurological damage in HIV-infected individuals, the likelihood of cognitive impairment increases with age, and duration of infection. As cART does not suppress the expression of HIV non-structural proteins, it has been proposed that a constitutive production of HIV regulatory proteins in infected brain cells may contribute to neurological damage. However, this assumption has never been experimentally tested. Here we take advantage of the leaky tetracycline promoter system in the Tat-transgenic mouse to show that a chronic very low-level expression of Tat is associated with astrocyte activation, inflammatory cytokine expression, ceramide accumulation, reductions in brain volume, synaptic, and axonal damage that occurs over a time frame of 1 year. These data suggest that a chronic low-level production of Tat may contribute to progressive neurological damage in virally suppressed HIV-infected individuals.

Topographies of Cortical and Subcortical Volume Loss in HIV and Aging in the cART Era

OBJECTIVES

Studies of HIV-associated brain atrophy often focus on a priori brain regions of interest, which can introduce bias. A data-driven, minimally biased approach was used to analyze changes in brain volumetrics associated with HIV and their relationship to aging, viral factors, combination antiretroviral therapy (cART), and gender, and smoking.

DESIGN

A cross-sectional study of 51 HIV-uninfected (HIV-) and 146 HIV-infected (HIV+) participants.

METHODS

Structural MRI of participants was analyzed using principal component analysis (PCA) to reduce dimensionality and determine topographies of volumetric changes. Neuropsychological (NP) assessment was examined using global and domain-specific scores. The effects of HIV disease factors (eg, viral load, CD4, etc.) on brain volumes and neuropsychological were investigated using penalized regression (LASSO).

RESULTS

Two components of interest were visualized using principal component analysis. An aging effect predominated for both components. The first component, a cortically weighted topography, accounted for a majority of variance across participants (43.5% of variance) and showed independent effects of HIV and smoking. A secondary, subcortically weighted topography (4.6%) showed HIV-status accentuated age-related volume loss. In HIV+ patients, the cortical topography correlated with global neuropsychological scores and nadir CD4, whereas subcortical volume loss was associated with recent viral load.

CONCLUSIONS

Cortical regions showed the most prominent volumetric changes because of aging and HIV. Within HIV+ participants, cortical volumes were associated with immune history, whereas subcortical changes correlated with current immune function. Cognitive function was primarily associated with cortical volume changes. Observed volumetric changes in chronic HIV+ patients may reflect both past infection history and current viral status.

Topological Organization of Whole-Brain White Matter in HIV Infection

Infection with human immunodeficiency virus (HIV) is associated with neuroimaging alterations. However, little is known about the topological organization of whole-brain networks and the corresponding association with cognition. As such, we examined structural whole-brain white matter connectivity patterns and cognitive performance in 29 HIV+ young adults (mean age = 25.9) with limited or no HIV treatment history. HIV+ participants and demographically similar HIV- controls (n = 16) residing in South Africa underwent magnetic resonance imaging (MRI) and neuropsychological testing. Structural network models were constructed using diffusion MRI-based multifiber tractography and T₁-weighted MRI-based regional gray matter segmentation. Global network measures included whole-brain structural integration, connection strength, and structural segregation. Cognition was measured using a neuropsychological global deficit score (GDS) as well as individual cognitive domains. Results revealed that HIV+ participants exhibited significant disruptions to whole-brain networks, characterized by weaker structural integration (characteristic path length and efficiency), connection strength, and structural segregation (clustering coefficient) than HIV- controls (p < 0.05). GDSs and performance on learning/recall tasks were negatively correlated with the clustering coefficient (p < 0.05) in HIV+ participants. Results from this study indicate disruption to brain network integrity in treatment-limited HIV+ young adults with corresponding abnormalities in cognitive performance.

Visceral fat is associated with brain structure independent of human immunodeficiency virus infection status

The combined effects of human immunodeficiency virus (HIV), obesity, and elevated visceral adipose tissue (VAT) on brain structure are unknown. In a cross-sectional analysis of Multicenter AIDS Cohort Study (MACS) participants, we determined associations between HIV serostatus, adiposity, and brain structure. Men (133 HIV+, 84 HIV-) in the MACS Cardiovascular 2 and magnetic resonance imaging (MRI) sub-studies with CT-quantified VAT and whole brain MRI measured within 1 year were assessed. Voxel-based morphometry analyzed brain volumes. Men were stratified by elevated (eVAT, ≥100cm²) or "normal" (nVAT, <100cm²) VAT. Forward stepwise modeling determined associations between clinical and demographic variables and regional brain volumes. eVAT was present in 67% of men. Groups were similar in age and education, but eVAT men were more likely to be HIV+ and have hypertension, diabetes mellitus, body mass index >25 kg/m², smaller gray and white matter volumes, and larger cerebrospinal fluid volume than nVAT men. In multivariate analysis, hypertension, higher adiponectin, higher interleukin-6, age, diabetes mellitus, higher body mass index, and eVAT were associated with brain atrophy (p < 0.05, ordered by increasing strength of association), but HIV serostatus and related factors were generally not. No interactions were observed. Greater VAT was associated with smaller bilateral posterior hippocampus and left mesial temporal lobe and temporal stem white matter volume. Traditional risk factors are more strongly associated with brain atrophy than HIV serostatus, with VAT having the strongest association. However, HIV+ MACS men had disproportionately greater VAT, suggesting the risk for central nervous system effects may be amplified in this population.

Neuroimaging abnormalities in clade C HIV are independent of Tat genetic diversity

Controversy remains regarding the neurotoxicity of clade C human immunodeficiency virus (HIV-C). When examined in preclinical studies, a cysteine to serine substitution in the C31 dicysteine motif of the HIV-C Tat protein (C31S) results in less severe brain injury compared to other viral clades. By contrast, patient cohort studies identify significant neuropsychological impairment among HIV-C individuals independent of Tat variability. The present study clarified this discrepancy by examining neuroimaging markers of brain integrity among HIV-C individuals with and without the Tat substitution. Thirty-seven HIV-C individuals with the Tat C31S substitution, 109 HIV-C individuals without the Tat substitution (C31C), and 34 HIV- controls underwent 3T structural magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI). Volumes were determined for the caudate, putamen, thalamus, corpus callosum, total gray matter, and total white matter. DTI metrics included fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD). Tracts of interest included the anterior thalamic radiation (ATR), cingulum bundle (CING), uncinate fasciculus (UNC), and corpus callosum (CC). HIV+ individuals exhibited smaller volumes in subcortical gray matter, total gray matter and total white matter compared to HIV- controls. HIV+ individuals also exhibited DTI abnormalities across multiple tracts compared to HIV- controls. By contrast, neither volumetric nor diffusion indices differed significantly between the Tat C31S and C31C groups. Tat C31S status is not a sufficient biomarker of HIV-related brain integrity in patient populations. Clinical attention directed at brain health is warranted for all HIV+ individuals, independent of Tat C31S or clade C status.

Putamen volume and its clinical and neurological correlates in primary HIV infection

OBJECTIVE

Little is known about the extent of cortical and subcortical volumetric alterations that may occur within the first year of HIV infection [primary HIV infection (PHI)].

DESIGN

We used structural MRI in this prospective cross-sectional neuroimaging study to determine the extent of volumetric changes in early HIV infection.

METHODS

Cerebrospinal fluid, blood, neuropsychological testing, and structural T1 MRI scans were acquired from 18 HIV and 47 PHI age-matched antiretroviral-naïve male participants. Using FreeSurfer 5.1, volumetric measurements were obtained from the caudate, amygdala, corpus callosum, ventricles, putamen, thalamus, cortical white matter, and total gray matter. Regional volumes were compared groupwise and related to biomarkers in cerebrospinal fluid (viral load, neopterin, and neurofilament light chain), blood (viral load, CD4, and CD8 T-cell count), and neuropsychometric tests (digit-symbol, grooved pegboard, finger-tapping, and timed gait).

RESULTS

A trend-level moderate reduction of putamen volume (P = 0.076, adjusted Cohen's d = 0.5 after controlling for age) was observed for PHI compared with HIV-uninfected individuals. Within the PHI group, putamen volume associated with CD4 cell count (P = 0.03), CD4/CD8 ratio (P = 0.045), infection duration (P = 0.009), and worsening psychomotor performance on the digit-symbol (P = 0.028), finger-tapping (P = 0.039), and timed gait (P = 0.009) tests.

CONCLUSION

Our volumetric results suggest that the putamen is preferentially susceptible to early HIV-associated processes. Examining the natural course of early HIV infection longitudinally will allow for mapping of the trajectory of HIV-associated central nervous system changes, enabling creation of improved interventional strategies to potentially stabilize or reverse these observed structural changes.

Effects of HIV and childhood trauma on brain morphometry and neurocognitive function

A wide spectrum of neurocognitive deficits characterises HIV infection in adults. HIV infection is additionally associated with morphological brain abnormalities affecting neural substrates that subserve neurocognitive function. Early life stress (ELS) also has a direct influence on brain morphology. However, the combined impact of ELS and HIV on brain structure and neurocognitive function has not been examined in an all-female sample with advanced HIV disease. The present study examined the effects of HIV and childhood trauma on brain morphometry and neurocognitive function. Structural data were acquired using a 3T Magnetom MRI scanner, and a battery of neurocognitive tests was administered to 124 women: HIV-positive with ELS (n = 32), HIV-positive without ELS (n = 30), HIV-negative with ELS (n = 31) and HIV-negative without ELS (n = 31). Results revealed significant group volumetric differences for right anterior cingulate cortex (ACC), bilateral hippocampi, corpus callosum, left and right caudate and left and right putamen. Mean regional volumes were lowest in HIV-positive women with ELS compared to all other groups. Although causality cannot be inferred, findings also suggest that alterations in the left frontal lobe, right ACC, left hippocampus, corpus callosum, left and right amygdala and left caudate may be associated with poorer neurocognitive performance in the domains of processing speed, attention/working memory, abstraction/executive functions, motor skills, learning and language/fluency with these effects more pronounced in women living with both HIV and childhood trauma. This study highlights the potential contributory role of childhood trauma to brain alterations and neurocognitive decline in HIV-infected individuals.

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

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

Physical Activity Affects Brain Integrity in HIV+ Individuals

Prior research has suggested benefits of aerobic physical activity (PA) on cognition and brain volumes in HIV uninfected (HIV-) individuals, however, few studies have explored the relationships between PA and brain integrity (cognition and structural brain volumes) in HIV-infected (HIV+) individuals. Seventy HIV+ individuals underwent neuropsychological testing, structural neuroimaging, laboratory tests, and completed a PA questionnaire, recalling participation in walking, running, and jogging activities over the last year. A PA engagement score of weekly metabolic equivalent (MET) hr of activity was calculated using a compendium of PAs. HIV+ individuals were classified as physically active (any energy expended above resting expenditure, n=22) or sedentary (n=48). Comparisons of neuropsychological performance, grouped by executive and motor domains, and brain volumes were completed between groups. Physically active and sedentary HIV+ individuals had similar demographic and laboratory values, but the active group had higher education (14.0 vs. 12.6 years, p=.034). Physically active HIV+ individuals performed better on executive (p=.040, unadjusted; p=.043, adjusted) but not motor function (p=.17). In addition, among the physically active group the amount of physical activity (METs) positively correlated with executive (Pearson's r=0.45, p=0.035) but not motor (r=0.21; p=.35) performance. In adjusted analyses the physically active HIV+ individuals had larger putamen volumes (p=.019). A positive relationship exists between PA and brain integrity in HIV+ individuals. Results from the present study emphasize the importance to conduct longitudinal interventional investigation to determine if PA improves brain integrity in HIV+ individuals.

Neuroimaging of HIV-associated neurocognitive disorders (HAND)

PURPOSE OF REVIEW

HIV enters the brain after initial infection, and with time can lead to HIV-associated neurocognitive disorders (HAND). Although the introduction of combination antiretroviral therapy has reduced the more severe forms of HAND, milder forms are still highly prevalent. The 'gold standard' for HAND diagnosis remains detailed neuropsychological performance testing but additional biomarkers (including neuroimaging) may assist in early detection of HAND.

RECENT FINDINGS

We review the application of recently developed noninvasive MRI and PET techniques in HIV+ individuals. In particular, magnetic resonance spectroscopy may be more sensitive than conventional MRI alone in detecting HIV associated changes. Diffusion tensor imaging has become increasingly popular for assessing changes in white matter structural integrity due to HIV. Both functional MRI and PET have been limitedly performed but could provide keys for characterizing neuropathophysiologic changes due to HIV.

SUMMARY

It is hoped that continued progress will allow novel neuroimaging methods to be included in future HAND management guidelines.

HIV effects on age-associated neurocognitive dysfunction: premature cognitive aging or neurodegenerative disease?

Marked improvements in survival and health outcome for people infected with HIV have occurred since the advent of combination antiretroviral therapy over a decade ago. Yet HIV-associated neurocognitive disorders continue to occur with an alarming prevalence. This may reflect the fact that infected people are now living longer with chronic infection. There is mounting evidence that HIV exacerbates age-associated cognitive decline. Many middle-aged HIV-infected people are experiencing cognitive decline similar that to that found among much older adults. An increased prevalence of vascular and metabolic comorbidities has also been observed and is greatest among older adults with HIV. Premature age-associated neurocognitive decline appears to be related to structural and functional brain changes on neuroimaging, and of particular concern is the fact that pathology indicative of neurodegenerative disease has been shown to occur in the brains of HIV-infected people. Yet notable differences also exist between the clinical presentation and brain disturbances occurring with HIV and those occurring in neurodegenerative conditions such as Alzheimer’s disease. HIV interacts with the aging brain to affect neurological structure and function. However, whether this interaction directly affects neurodegenerative processes, accelerates normal cognitive aging, or contributes to a worsening of other comorbidities that affect the brain in older adults remains an open question. Evidence for and against each of these possibilities is reviewed.

Differences in the direction of change of cerebral function parameters are evident over three years in HIV-infected individuals electively commencing initial cART

Background

Changes in cerebral metabolite ratios (CMR) measured on ¹H-MRS and changes in cognitive function (CF) are described in subjects commencing combination antiretroviral therapy (cART), although the dynamics of such changes are poorly understood.

Methods

Neuroasymptomatic, HIV-infected subjects electively commencing cART were eligible. CMR were assessed in three anatomical voxels and CF assessed at baseline, week 48 and week 144. Overall differences in absolute change in CMRs and CF parameters between 0–48 and 48–144 weeks were assessed.

Results

Twenty-two subjects completed study procedures. Plasma HIV-RNA was <50 copies/mL in all at week 48 and in all, but two subjects at week 144. In general, between weeks 0–48 a rise in N-acetyl-aspartate(NAA)/Creatine(Cr) ratio and a decline in myo-Inositol(mI)/Cr ratio were observed. Between weeks 48–144, small rises in NAA/Cr ratio were observed in two anatomical voxels, whereas a rise in mI/Cr ratio was observed in all anatomical locations (0.31 (0.66) and -0.27 (1.35) between weeks 0–48 and 0.13 (0.91) and 1.13 (1.71) between weeks 48–144 for absolute changes in NAA/Cr and mI/Cr (SD) in frontal-grey voxel, respectively). Global CF score improved between weeks 0–48 and then declined between weeks 48–144 (0.63 (1.16) and -0.63 (0.1.41) for mean absolute change (SD) between weeks 0–48 and weeks 48–144, respectively).

Conclusions

The direction of change of cerebral function parameters differs over time in HIV-infected subjects commencing cART, highlighting the need for long-term follow-up in such studies. The changes we have observed between weeks 48–144 may represent the initial development of cerebral toxicities from cART.

Accelerated aging of selective brain structures in human immunodeficiency virus infection: a controlled, longitudinal magnetic resonance imaging study

Advances in treatment have transformed human immunodeficiency virus (HIV) infection from an inexorable march to severe morbidity and premature death to a manageable chronic condition, often marked by good health. Thus, infected individuals are living long enough that there is a potential for interaction with normal senescence effects on various organ systems, including the brain. To examine this interaction, the brains of 51 individuals with HIV infection and 65 uninfected controls were studied using 351 magnetic resonance imaging and a battery of neuropsychological tests collected 2 or more times over follow-up periods ranging from 6 months to 8 years. Brain tissue regions of interest showed expected age-related decrease in volume; cerebrospinal fluid-filled spaces showed increase in volume for both groups. Although HIV-infected individuals were in good general health, and free of clinically-detectable dementia, several brain regions supporting higher-order cognition and integration of functions showed acceleration of the normal aging trajectory, including neocortex, which extended from the frontal and temporal poles to the parietal lobe, and the thalamus. Beyond an anticipated increase in lateral ventricle and Sylvian fissure volumes and decrease in tissue volumes (specifically, the frontal and sensorimotor neocortices, thalamus, and hippocampus) with longer duration of illness, most regions also showed accelerated disease progression. This accelerated loss of cortical tissue may represent a risk factor for premature cognitive and motor compromise if not dementia. On a more promising note, HIV-infected patients with increasing CD4 counts exhibited slower expansion of Sylvian fissure volume and slower declines of frontal and temporoparietal cortices, insula, and hippocampus tissue volumes. Thus, attenuated shrinkage of these brain regions, likely with adequate pharmacologic treatment and control of further infection, has the potential of abating decline in associated higher-order functions, notably, explicit memory, executive functions, self-regulation, and visuospatial abilities.

Role of neuroimaging in HIV-associated neurocognitive disorders

Human immunodeficiency virus (HIV) enters the brain soon after seroconversion and can cause HIV-associated neurocognitive disorders (HAND). Although the more severe and progressive forms of HAND are less prevalent due to combination antiretroviral therapy (cART), ∼ 40% of HIV-infected (HIV+) patients continue to have cognitive impairment. Some HIV+ individuals who have effective plasma HIV-1 RNA suppression with cART still develop HAND. It is often difficult to diagnose HAND in the outpatient setting as detailed neuropsychological performance testing is required. Additional biomarkers that are relatively easy to obtain and clinically relevant are needed for assessing HIV-associated neuropathologic changes. Recently developed noninvasive magnetic resonance imaging (MRI) techniques have great potential to serve as biomarkers. The authors review the application of some of these neuroimaging techniques, magnetic resonance spectroscopy (MRS), volumetric MRI, diffusion tensor imaging (DTI), functional MRI (fMRI), in HIV+ individuals. Each of the neuroimaging methods offers unique insight into mechanisms underlying neuroHIV, could monitor disease progression, and may assist in evaluating the efficacy of particular cART regimens. It is hoped that considerable progress will continue to occur such that some of these neuroimaging methods will be incorporated across multiple sites and included in future HAND guidelines.

Relationship of plasma cytokines and clinical biomarkers to memory performance in HIV

Chronic systemic immune activation and inflammatory processes have been linked to brain dysfunction in medically stable HIV-infected people. We investigated the association between verbal memory performance and plasma concentrations of 13 cytokines measured using multiplexed bead array immunoassay in 74 HIV-seropositive individuals and 50 HIV-seronegative controls. Memory performance was positively related to levels of IL-8 and IFN-γ, and negatively related to IL-10 and IL-18 and to hepatitis C infection. Memory performance was not significantly related to HIV disease markers. The results indicate the importance of systemic immune and inflammatory markers to neurocognitive function in chronic and stable HIV disease.

Neuroimaging biomarkers of neurodegenerative diseases and dementia

Neurodegenerative disorders leading to dementia are common diseases that affect many older and some young adults. Neuroimaging methods are important tools for assessing and monitoring pathological brain changes associated with progressive neurodegenerative conditions. In this review, the authors describe key findings from neuroimaging studies (magnetic resonance imaging and radionucleotide imaging) in neurodegenerative disorders, including Alzheimer's disease (AD) and prodromal stages, familial and atypical AD syndromes, frontotemporal dementia, amyotrophic lateral sclerosis with and without dementia, Parkinson's disease with and without dementia, dementia with Lewy bodies, Huntington's disease, multiple sclerosis, HIV-associated neurocognitive disorder, and prion protein associated diseases (i.e., Creutzfeldt-Jakob disease). The authors focus on neuroimaging findings of in vivo pathology in these disorders, as well as the potential for neuroimaging to provide useful information for differential diagnosis of neurodegenerative disorders.

Disrupted cerebral metabolite levels and lower nadir CD4 + counts are linked to brain volume deficits in 210 HIV-infected patients on stable treatment

Cognitive impairment and brain injury are common in people with HIV/AIDS, even when viral replication is effectively suppressed with combined antiretroviral therapies (cART). Metabolic and structural abnormalities may promote cognitive decline, but we know little about how these measures relate in people on stable cART. Here we used tensor-based morphometry (TBM) to reveal the 3D profile of regional brain volume variations in 210 HIV + patients scanned with whole-brain MRI at 1.5 T (mean age: 48.6 ± 8.4 years; all receiving cART). We identified brain regions where the degree of atrophy was related to HIV clinical measures and cerebral metabolite levels assessed with magnetic resonance spectroscopy (MRS). Regional brain volume reduction was linked to lower nadir CD4 + count, with a 1–2% white matter volume reduction for each 25-point reduction in nadir CD4 +. Even so, brain volume measured by TBM showed no detectable association with current CD4 + count, AIDS Dementia Complex (ADC) stage, HIV RNA load in plasma or cerebrospinal fluid (CSF), duration of HIV infection, antiretroviral CNS penetration-effectiveness (CPE) scores, or years on cART, after controlling for demographic factors, and for multiple comparisons. Elevated glutamate and glutamine (Glx) and lower N-acetylaspartate (NAA) in the frontal white matter, basal ganglia, and mid frontal cortex — were associated with lower white matter, putamen and thalamus volumes, and ventricular and CSF space expansion. Reductions in brain volumes in the setting of chronic and stable disease are strongly linked to a history of immunosuppression, suggesting that delays in initiating cART may result in imminent and irreversible brain damage.

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We mapped the 3D pattern of brain abnormalities in 210 HIV patients on stable cART.

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Brain atrophy was linked to MRS metabolite disturbances reflecting neuronal injury.

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Lower nadir CD4 + count was associated with greater white matter atrophy.

HIV, vascular and aging injuries in the brain of clinically stable HIV-infected adults: a (1)H MRS study

BACKGROUND

Cardiovascular disease (CVD) and premature aging have been hypothesized as new risk factors for HIV associated neurocognitive disorders (HAND) in adults with virally-suppressed HIV infection. Moreover, their significance and relation to more classical HAND biomarkers remain unclear.

METHODS

92 HIV- infected (HIV+) adults stable on combined antiretroviral therapy (cART) and 30 age-comparable HIV-negative (HIV-) subjects underwent (1)H Magnetic Resonance Spectroscopy (MRS) of the frontal white matter (targeting HIV, normal aging or CVD-related neurochemical injury), caudate nucleus (targeting HIV neurochemical injury), and posterior cingulate cortex (targeting normal/pathological aging, CVD-related neurochemical changes). All also underwent standard neuropsychological (NP) testing. CVD risk scores were calculated. HIV disease biomarkers were collected and cerebrospinal fluid (CSF) neuroinflammation biomarkers were obtained in 38 HIV+ individuals.

RESULTS

Relative to HIV- individuals, HIV+ individuals presented mild MRS alterations: in the frontal white matter: lower N-Acetyl-Aspartate (NAA) (p<.04) and higher myo-inositol (mIo) (p<.04); in the caudate: lower NAA (p = .01); and in the posterior cingulate cortex: higher mIo (p<.008- also significant when Holm-Sidak corrected) and higher Choline/NAA (p<.04). Regression models showed that an HIV*age interaction was associated with lower frontal white matter NAA. CVD risk factors were associated with lower posterior cingulate cortex and caudate NAA in both groups. Past acute CVD events in the HIV+ group were associated with increased mIo in the posterior cingulate cortex. HIV duration was associated with lower caudate NAA; greater CNS cART penetration was associated with lower mIo in the posterior cingulate cortex and the degree of immune recovery on cART was associated with higher NAA in the frontal white matter. CSF neopterin was associated with higher mIo in the posterior cingulate cortex and frontal white matter.

CONCLUSIONS

In chronically HIV+ adults with long-term viral suppression, current CVD risk, past CVD and age are independent factors for neuronal injury and inflammation. This suggests a tripartite model of HIV, CVD and age likely driven by chronic inflammation.

Peripheral blood HIV DNA is associated with atrophy of cerebellar and subcortical gray matter

OBJECTIVE

We evaluated regional brain volumes and cerebral metabolite levels as correlates of HIV DNA in peripheral blood mononuclear cells (PBMCs).

METHODS

In this cross-sectional study, 35 HIV+ subjects aged ≥40 years (25 with detectable PBMC HIV DNA; 10 with HIV DNA <10 copies/10(6) cells, the threshold of detection) and 12 seronegative controls underwent structural brain MRI and magnetic resonance spectroscopy at 3 T. HIV+ subjects were on combination antiretroviral therapy ≥1 year; all but 1 had plasma HIV RNA <50 copies/mL. We used logistic regression to evaluate relationships of likely predictor variables to the outcome of PBMC HIV DNA detectability in the HIV+ subjects. Effects of serostatus and HIV DNA on regional brain volumes (normalized to intracranial volume) and on metabolite ratios over creatine were evaluated by analyses of covariance, controlling for age.

RESULTS

Relative to the HIV+ group with undetectable HIV DNA, subjects with detectable HIV DNA demonstrated decreased volumes of cerebellar (-14%, p = 0.020) and total subcortical (-10%, p = 0.024) gray matter. Compared to healthy controls, only the detectable HIV DNA group showed significant (p < 0.05) enlargement of lateral ventricles and volumetric reductions of caudate, putamen, thalamus, hippocampus, nucleus accumbens, brainstem, total cortical gray matter, and cerebral white matter. Detectable HIV DNA was not associated with significantly altered cerebral metabolite levels.

CONCLUSION

Inability to clear peripheral blood of HIV DNA is associated with regional brain atrophy in well-controlled HIV infection, supporting the involvement of peripheral viral reservoirs in the neuropathogenesis of persistent HIV-related neurocognitive disorders.

Assessment, diagnosis, and treatment of HIV-associated neurocognitive disorder: a consensus report of the mind exchange program

Many practical clinical questions regarding the management of human immunodeficiency virus (HIV)-associated neurocognitive disorder (HAND) remain unanswered. We sought to identify and develop practical answers to key clinical questions in HAND management. Sixty-six specialists from 30 countries provided input into the program, which was overseen by a steering committee. Fourteen questions were rated as being of greatest clinical importance. Answers were drafted by an expert group based on a comprehensive literature review. Sixty-three experts convened to determine consensus and level of evidence for the answers. Consensus was reached on all answers. For instance, good practice suggests that all HIV patients should be screened for HAND early in disease using standardized tools. Follow-up frequency depends on whether HAND is already present or whether clinical data suggest risk for developing HAND. Worsening neurocognitive impairment may trigger consideration of antiretroviral modification when other causes have been excluded. The Mind Exchange program provides practical guidance in the diagnosis, monitoring, and treatment of HAND.

Distal sensory polyneuropathy is associated with neuropsychological test performance among persons with HIV

While distal sensory polyneuropathy (DSP) is the most common neurological condition associated with HIV, causing nerve damage in upper and lower extremities, its impact on neuropsychological test performance is unclear. In this study, we analyzed baseline data for 278 HIV-infected participants with comprehensive neurological and neurocognitive evaluations to examine the contribution of DSP and anatomic distribution of neuropathic signs (upper extremity or lower extremity) on standardized domain scores. We found that participants with DSP performed significantly worse in multiple domains containing timed psychomotor tests (i.e., motor, information processing speed and executive functioning). With regard to executive functioning, differences were limited to a test with a motor component (Trail Making Test, Part B). The group with clinically detectable neuropathic signs in the upper extremities and the group with signs limited to the lower extremities both performed worse in the motor domain than the group without DSP. Participants with DSP demonstrated a unique pattern of impairment limited to neuropsychological domains with timed psychomotor tests. These results suggest that caution should be used in interpretation of neuropsychological tests in patients with DSP, as some abnormalities may be exacerbated by peripheral nervous system pathology. (JINS, 2012, 19, 1-10).

Regional brain structural dysmorphology in human immunodeficiency virus infection: effects of acquired immune deficiency syndrome, alcoholism, and age

BACKGROUND

Human immunodeficiency virus (HIV) infection and alcoholism each carries liability for disruption of brain structure and function integrity. Despite considerable prevalence of HIV-alcoholism comorbidity, few studies examined the potentially heightened burden of disease comorbidity.

METHODS

Participants were 342 men and women: 110 alcoholics, 59 with HIV infection, 65 with HIV infection and alcoholism, and 108 healthy control subjects. This design enabled examination of independent and combined effects of HIV infection and alcoholism along with other factors (acquired immune deficiency syndrome [AIDS]-defining events, hepatitis C infection, age) on regional brain volumes derived from T1-weighted magnetic resonance images.

RESULTS

Brain volumes, expressed as Z scores corrected for intracranial volume and age, were measured in 20 tissue and 5 ventricular and sulcal regions. The most profound and consistent volume deficits occurred with alcohol use disorders, notable in the cortical mantle, insular and anterior cingulate cortices, thalamus, corpus callosum, and frontal sulci. The HIV-only group had smaller thalamic and larger frontal sulcal volumes than control subjects. HIV disease-related factors associated with greater volume abnormalities included CD4 cell count nadir, clinical staging, history of AIDS-defining events, infection age, and current age. Longer sobriety and less lifetime alcohol consumption were predictive of attenuated brain volume abnormalities in both alcohol groups.

CONCLUSIONS

Having HIV infection with alcoholism and AIDS had an especially poor outcome on brain structures. That longer periods of sobriety and less lifetime alcohol consumption were predictive of attenuated brain volume abnormalities encourages the inclusion of alcohol recovery efforts in HIV/AIDS therapeutic settings.

Two patterns of cerebral metabolite abnormalities are detected on proton magnetic resonance spectroscopy in HIV-infected subjects commencing antiretroviral therapy

INTRODUCTION

Cerebral function impairment remains problematic in subjects with chronic human immunodeficiency virus (HIV) infection despite effective combination antiretroviral therapy (cART). Using cerebral proton magnetic resonance spectroscopy ((1)H MRS), we aimed to determine if abnormalities could be detected in neurologically asymptomatic HIV-infected subjects electively commencing cART.

METHODS

Therapy-naive, HIV-infected individuals and HIV-uninfected controls underwent (1)H MRS in several anatomical voxels including the mid-frontal grey matter (FGM) and right basal ganglia (RBG). Differences in cerebral metabolite ratios between groups and correlations between immune and virological status were assessed.

RESULTS

Forty-six subjects were recruited (26 HIV-infected and 20 control subjects). In the HIV-infected group, mean CD4+ count (SD, cells per microlitre) and plasma HIV RNA (SD, log10 copies per millilitre) were 192 (86) and 4.71 (0.64), respectively. Choline (Cho)/Creatine (Cr) and myoinositol (MI)/Cr ratios were significantly lower in the FGM in HIV-infected subjects compared to controls (0.67 (0.14) versus 0.88 (0.49), p = 0.036, and 0.94 (0.28) and 1.17 (0.26), p = 0.008, for Cho/Cr and MI/Cr, respectively) and Cho/Cr ratio associated with CD4+ lymphocyte count (p = 0.041). N-Acetyl-aspartate (NAA)/Cho ratio was significantly lower in the RBG in HIV-infected subjects compared to controls (2.27 (0.54) versus 2.63 (0.68), p = 0.002), and this was associated with greater plasma HIV RNA load (p = 0.014).

CONCLUSIONS

Two patterns of cerebral metabolite abnormalities were observed in HIV-infected subjects electively commencing cART. Greater inflammatory metabolite ratios (Cho/Cr and MI/Cr) associated with lower markers of peripheral immune markers (CD4+ lymphocyte count) in the FGM and lower neuronal metabolite ratios (NAA/Cho) associated with greater HIV viraemia in the RBG were present in HIV-infected subjects.

Effects of HIV and early life stress on amygdala morphometry and neurocognitive function

Both HIV infection and high levels of early life stress (ELS) have been related to abnormalities in frontal-subcortical structures, yet the combined effects of HIV and ELS on brain structure and function have not been previously investigated. In this study we assessed 49 non-demented HIV-seropositive (HIV+) and 47 age-matched HIV-seronegative healthy control (HC) adults. Levels of ELS exposure were quantified and used to define four HIV-ELS groups: HC Low-ELS (N = 20); HC High-ELS (N = 27); HIV+ Low-ELS (N = 24); HIV+ High-ELS (N = 25). An automated segmentation tool measured volumes of brain structures known to show HIV-related or ELS-related effects; a brief neurocognitive battery was administered. A significant HIV-ELS interaction was observed for amygdala volumes, which was driven by enlargements in HIV+ High-ELS participants. The HIV+ High-ELS group also demonstrated significant reductions in psychomotor/processing speed compared with HC Low-ELS. Regression analyses in the HIV+ group revealed that amygdala enlargements were associated with higher ELS, lower nadir CD4 counts, and reduced psychomotor/processing speed. Our results suggest that HIV infection and high ELS interact to increase amygdala volume, which is associated with neurocognitive dysfunction in HIV+ patients. These findings highlight the lasting neuropathological influence of ELS and suggest that high ELS may be a significant risk factor for neurocognitive impairment in HIV-infected individuals.

Independent effects of HIV, aging, and HAART on brain volumetric measures

BACKGROUND

Neurocognitive impairment remains prevalent in HIV-infected (HIV+) individuals despite highly active antiretroviral therapy (HAART). We assessed the impact of HIV, HAART, and aging using structural neuroimaging.

METHODS

Seventy-eight participants [HIV- (n = 26), HIV+ on stable HAART (HIV+/HAART+; n = 26), HIV+ naive to HAART (HIV+/HAART-; n = 26)] completed neuroimaging and neuropsychological testing. A subset of HIV+ subjects (n = 12) performed longitudinal assessments before and after initiating HAART. Neuropsychological tests evaluated memory, psychomotor speed, and executive function, and a composite neuropsychological score was calculated based on normalized performances (neuropsychological summary Z score, NPZ-4). Volumetrics were evaluated for the amygdala, caudate, thalamus, hippocampus, putamen, corpus callosum, and cerebral gray and white matter. A 3-group 1-way analysis of variance assessed differences in neuroimaging and neuropsychological indices. Correlations were examined between NPZ-4 and volumetrics. Exploratory testing using a broken-stick regression model evaluated self-reported duration of HIV infection on brain structure.

RESULTS

HIV+ individuals had significant reductions in brain volumetrics within select subcortical regions (amygdala, caudate, and corpus callosum) compared with HIV- participants. However, HAART did not affect brain structure as regional volumes were similar for HIV+/HAART- and HIV+/HAART+. No association existed between NPZ-4 and volumetrics. HIV and aging were independently associated with volumetric reductions. Exploratory analyses suggest caudate atrophy due to HIV slowly occurs after self-reported seroconversion.

CONCLUSIONS

HIV associated volumetric reductions within the amygdala, caudate, and corpus callosum occurs despite HAART. A gradual decline in caudate volume occurs after self-reported seroconversion. HIV and aging independently increase brain vulnerability. Additional longitudinal structural magnetic resonance imaging studies, especially within older HIV+ participants, are required.

Regional cerebral blood flow and FDG uptake in asymptomatic HIV-1 men

Despite advances in the treatment of patients with human immunodeficiency virus (HIV), HIV-associated neurocognitive disorder occurs in 15-50% of HIV-infected individuals, and may become more apparent as ageing advances. In the present study we investigated regional cerebral blood flow (rCBF) and regional cerebral metabolic rate of glucose uptake (rCMRglc) in medically and psychiatrically stable HIV-1-infected participants in two age-groups. Positron emission tomography (PET) and magnetic resonance imaging (MRI)-based arterial spin labeling (ASL) were used to measure rCMRglc and rCBF, respectively, in 35 HIV-infected participants and 37 HIV-negative matched controls. All participants were currently asymptomatic with undetectable HIV-1 viral loads, without medical or psychiatric comorbidity, alcohol or substance misuse, stable on medication for at least 6 months before enrolment in the study. We found significant age effects on both ASL and PET with reduced rCBF and rCMRglc in related frontal brain regions, and consistent, although small, reductions in rCBF and rCMRglc in the anterior cingulate cortex (ACC) in HIV, a finding of potential clinical significance. There was no significant interaction between HIV status and the ageing process, and no significant HIV-related changes elsewhere in the brain on PET or ASL. This is the first paper to combine evidence from ASL and PET method in HIV participants. These finding provide evidence of crossvalidity between the two techniques, both in ageing and a clinical condition (HIV).