Cerebral blood flow and cognitive function in HIV-infected men with sustained suppressed viremia on combination antiretroviral therapy

Circulating endothelial and angiogenic cells predict hippocampal volume as a function of HIV status

Circulating endothelial cells (CECs) and myeloid angiogenic cells (MACs) have the capacity to stabilize human blood vessels in vivo. Evidence suggests that these cells are depleted in dementia and in persons living with HIV (PWH), who have a higher prevalence of dementia and other cognitive deficits associated with aging. However, the associations of CECs and MACs with MRI-based measures of aging brain health, such as hippocampal gray matter volume, have not been previously demonstrated. The present study examined differences in these associations in 51 postmenopausal women with and without HIV infection. Gray matter volume was quantified using MRI. CECs and MACs were enumerated using fluorescence-activated cell sorting. Analyses examined the association of these cell counts with left and right hippocampal gray matter volume while controlling for age and hypertension status. The main finding was an interaction suggesting that compared to controls, postmenopausal PWH with greater levels of CECs and MACs had significantly greater hippocampus GMV. Further research is necessary to examine potential underlying pathophysiological mechanisms in HIV infection linking morpho-functional circulatory reparative processes with more diminished hippocampal volume in postmenopausal women.

HIV Promotes Neurocognitive Impairment by Damaging the Hippocampal Microvessels

Current evidence suggests that mild cerebrovascular changes could induce neurodegeneration and contribute to HIV-associated neurocognitive disease (HAND) in HIV patients. We investigated both the quantitative and qualitative impact of HIV infection on brain microvessels, especially on hippocampal microvessels, which are crucial for optimal O2 supply, and thus for maintaining memory and cognitive abilities. The results obtained using cultured human brain microvascular endothelial cells (HBMEC) were reproduced using a suitable mouse model and autopsied human HIV hippocampus. In HBMEC, we found significantly higher oxidative stress-dependent apoptotic cell loss following 5 h of treatment of GST-Tat (1 µg/ml) compared to GST (1 µg/ml) control. We noticed complete recovery of HBMEC cells after 24 h of GST-Tat treatment, due to temporal degradation or inactivation of GST-Tat. Interestingly, we found a sustained increase in mitochondrial oxidative DNA damage marker 8-OHdG, as well as an increase in hypoxia-inducible factor hypoxia-inducible factor-1α (HIF-1α). In our mouse studies, upon short-term injection of GST-Tat, we found the loss of small microvessels (mostly capillaries) and vascular endothelial growth factor (VEGF), but not large microvessels (arterioles and venules) in the hippocampus. In addition to capillary loss, in the post-mortem HIV-infected human hippocampus, we observed large microvessels with increased wall cells and perivascular tissue degeneration. Together, our data show a crucial role of Tat in inducing HIF-1α-dependent inhibition of mitochondrial transcriptional factor A (TFAM) and dilated perivascular space. Thus, our results further define the underlying molecular mechanism promoting mild cerebrovascular disease, neuropathy, and HAND pathogenesis in HIV patients.

Effects of Framingham 10-Year Cardiovascular Risk Score and Viral Load on Brain Integrity in Persons With HIV

BACKGROUND

Combination antiretroviral therapy (cART) has allowed for viral load (VL) suppression and increased life expectancy for persons with HIV (PWH). Altered brain integrity, measured by neuropsychological (NP) performance and neuroimaging, is still prevalent among virally suppressed PWH. Age-related conditions such as cardiovascular disease may also affect brain integrity. This study investigated the effects of cardiovascular risk, VL, and HIV serostatus on cerebral blood flow (CBF), brain volumetrics, and cognitive function in PWH and persons without HIV (PWoH).

METHODS

Ten-year cardiovascular risk, using the Framingham Heart Study criteria, was calculated in PWH (n = 164) on cART with undetectable (≤20 copies/mL; n = 134) or detectable (>20 copies/mL; n = 30) VL and PWoH (n = 66). The effects of cardiovascular risk on brain integrity (CBF, volume, and cognition) were compared for PWH (undetectable and detectable VL) and PWoH.

RESULTS

PWH had smaller brain volumes and worse NP scores than PWoH. PWH with detectable and undetectable VL had similar brain integrity measures. Higher cardiovascular risk was associated with smaller volumes and lower CBF in multiple brain regions for PWH and PWoH. Significant interactions between HIV serostatus and cardiovascular risk on brain volumes were observed in frontal, orbitofrontal, and motor regions. Cardiovascular risk was not associated with cognition for PWH or PWoH.

CONCLUSIONS

Neuroimaging, but not cognitive measures, was associated with elevated cardiovascular risk. HIV serostatus was associated with diminished brain volumes and worse cognition while CBF remained unchanged, reflecting potential protective effects of cART. Neuroimaging measures of structure (volume) and function (CBF) may identify contributions of comorbidities, but future longitudinal studies are needed.

Reduction in cerebral oxygen metabolism in subcortical regions may be a biomarker of cognitive decline in people living with human immunodeficiency virus

BACKGROUND AND PURPOSE

Regional cerebral blood flow (rCBF) and oxygen metabolism (rCMRO₂ ) in whole brain, white matter, gray matter and lenticular nuclei were studied in people living with human immunodeficiency virus (PLHIV) as well as HIV-associated neurocognitive disorder (HAND).

METHODS

Treatment-naïve PLHIV underwent neurocognitive assessment and magnetic resonance (MR) measurement of rCBF and rCMRO₂ with repeat after 12 months of antiretroviral therapy (ART). Age- and sex-matched controls underwent single MR measurements. Regional CBF and rCMRO₂ were compared amongst symptomatic, asymptomatic, normal HAND and controls using analysis of variance. Longitudinal analysis of HAND worsening (≥1 category) was assessed after 12 months of ART and correlated with rCBF and rCMRO₂ measured by MR imaging using the paired-sample t test.

RESULTS

Thirty PLHIV completed baseline and 12-month assessments (29 with rCMRO₂ measurement). At baseline HAND assessment, 13% had no cognitive impairment, 27% had asymptomatic neurocognitive impairment, 60% had mild neurocognitive disorder and none had HIV-associated dementia. At 12 months, 13% had no cognitive impairment, 20% had asymptomatic neurocognitive impairment, 50% had mild neurocognitive disorder and 17% had HIV-associated dementia. In those without HAND worsening (N = 21) rCMRO₂ remained stable and in those with HAND worsening (N = 8) rCMRO₂ measurement declined from baseline to 12 months in white matter (2.05 ± 0.40 to 1.73 ± 0.51, p = 0.03) and lenticular nuclei (4.32 ± 0.39 to 4.00 ± 0.51, p = 0.05).

CONCLUSIONS

In recently diagnosed PLHIV, no association was found between rCBF or rCMRO₂ and cognitive impairment at baseline. There was a reduction in rCMRO₂ in those with worsening of cognitive function at 12 months on ART. Reduction in rCMRO₂ may be a biomarker of cognitive decline in PLHIV.

Regional Cerebral Blood Flow Abnormalities in Neurosyphilis: A Pilot SPECT Study

Objective: Clinical and radiological findings on neurosyphilis are fairly non-specific and there is a paucity of functional neuroimaging studies on neurosyphilis other than case reports and case series. The purpose of this study was to investigate brain perfusion abnormalities in patients with neurosyphilis. Methods: Four HIV-negative neurosyphilis patients and 4 healthy controls underwent clinical evaluation, brain technetium-99m ethyl cysteinate dimer (99mTc-ECD) single-photon emission computed tomography (SPECT) imaging, and neuropsychological assessments which included the Mini-Mental State Examination (MMSE), Clinical Dementia Rating (CDR), Clinical Dementia Rating-Sum of Boxes (CDR-SOB), and Global Deterioration Scale (GDS). Voxel-wise differences in regional cerebral blood flow were compared between the two groups. Results: Neuropsychological test results indicated cognitive impairment in all patients. SPECT analysis revealed multifocal hypoperfusion predominantly in the frontal, insular, and posterior cingulate regions in neurosyphilis patients compared with healthy controls (family-wise error corrected p < 0.05). Conclusions: Together with previous findings, our results suggest that the hypoperfusion in the frontal, insular, and posterior cingulate regions may reflect cognitive impairments observed in neurosyphilis patients. Further studies with larger samples are needed to confirm our findings.

Accelerated Brain Aging and Cerebral Blood Flow Reduction in Persons With Human Immunodeficiency Virus

BACKGROUND

Persons with human immunodeficiency virus (PWH) are characterized by altered brain structure and function. As they attain normal lifespans, it has become crucial to understand potential interactions between human immunodeficiency virus (HIV) and aging. However, it remains unclear how brain aging varies with viral load (VL).

METHODS

In this study, we compare magnetic resonance imaging (MRI) biomarkers among PWH with undetectable VL (UVL; ≤50 genomic copies/mL; n = 230), PWH with detectable VL (DVL; >50 copies/mL; n = 93), and HIV-uninfected (HIV-) controls (n = 206). To quantify gray matter cerebral blood flow (CBF), we utilized arterial spin labeling. To measure structural aging, we used a publicly available deep learning algorithm to estimate brain age from T1-weighted MRI. Cognitive performance was measured using a neuropsychological battery covering 5 domains.

RESULTS

Associations between age and CBF varied with VL. Older PWH with DVL had reduced CBF vs PWH with UVL (P = .02). Structurally predicted brain aging was accelerated in PWH vs HIV- controls regardless of VL (P < .001). Overall, PWH had impaired learning, executive function, psychomotor speed, and language compared to HIV- controls. Structural brain aging was associated with reduced psychomotor speed (P < .001).

CONCLUSIONS

Brain aging in HIV is multifaceted. CBF depends on age and current VL and is improved by medication adherence. By contrast, structural aging is an indicator of cognitive function and reflects serostatus rather than current VL.

A Longitudinal Analysis of Cerebral Blood Flow in Perinatally HIV Infected Adolescents as Compared to Matched Healthy Controls

Despite effective combination anti-retroviral therapy (cART), perinatally HIV infected (PHIV) adolescents still experience cognitive complications. We previously reported higher cerebral blood flow (CBF) in basal ganglia and white matter (WM) in PHIV children compared to matched controls. In healthy children CBF is associated with cognitive domains. To determine longitudinal changes in CBF and its impact on cognitive complications, we measured CBF—using arterial spin labeling—in 21 PHIV adolescents and 23 controls matched for age, sex and socio-economic status twice with a mean follow-up of 4.6 years. We explored associations between CBF changes and WM micro- and macrostructural markers and cognitive domains using linear mixed models. The median age at follow-up was comparable between PHIV adolescents 17.4y (IQR:15.3–20.7) and controls 16.2y (IQR:15.6–19.1). At baseline, PHIV had higher CBF in the caudate nucleus and putamen. CBF development was comparable in gray matter (GM), WM and subcortical regions in both groups. In our cohort, we found that over time an increase of GM CBF was associated with an increase of visual motor function (p = 0.043) and executive function (p = 0.045). Increase of CBF in the caudate nucleus, putamen and thalamus was associated with an increase processing speed (p = 0.033; 0.036; 0.003 respectively) and visual motor function (p = 0.023; 0.045; 0.003 respectively). CBF development is relatively normal in PHIV adolescents on cART. CBF decline is associated with cognitive impairment, irrespective of HIV status.

Role of Brain Arterial Remodeling in HIV-Associated Cerebrovascular Outcomes

As the life expectancy of people living with HIV (PLWH) on combination antiretroviral therapy (cART) increases, so does morbidity from cerebrovascular disease and neurocognitive disorders. Brain arterial remodeling stands out as a novel investigational target to understand the role of HIV in cerebrovascular and neurocognitive outcomes. We therefore conducted a review of publications in PubMed, EMBASE, Web of Science and Wiley Online Library, from inception to April 2021. We included search terms such as HIV, cART, brain, neuroimmunity, arterial remodeling, cerebrovascular disease, and neurocognitive disorders. The literature shows that, in the post-cART era, PLWH continue to experience an increased risk of stroke and neurocognitive disorders (albeit milder forms) compared to uninfected populations. PLWH who are immunosuppressed have a higher proportion of hemorrhagic strokes and strokes caused by opportunistic infection and HIV vasculopathy, while PLWH on long-term cART have higher rates of ischemic strokes, compared to HIV-seronegative controls. Brain large artery atherosclerosis in PLWH is associated with lower CD4 nadir and higher CD4 count during the stroke event. HIV vasculopathy, a form of non-atherosclerotic outward remodeling, on the other hand, is associated with protracted immunosuppression. HIV vasculopathy was also linked to a thinner media layer and increased adventitial macrophages, suggestive of non-atherosclerotic degeneration of the brain arterial wall in the setting of chronic central nervous system inflammation. Cerebrovascular architecture seems to be differentially affected by HIV infection in successfully treated versus immunosuppressed PLWH. Brain large artery atherosclerosis is prevalent even with long-term immune reconstitution post-cART. HIV-associated changes in brain arterial walls may also relate to higher rates of HIV-associated neurocognitive disorders, although milder forms are more prevalent in the post-cART era. The underlying mechanisms of HIV-associated pathological arterial remodeling remain poorly understood, but a role has been proposed for chronic HIV-associated inflammation with increased burden on the vasculature. Neuroimaging may come to play a role in assessing brain arterial remodeling and stratifying cerebrovascular risk, but the data remains inconclusive. An improved understanding of the different phenotypes of brain arterial remodeling associated with HIV may reveal opportunities to reduce rates of cerebrovascular disease in the aging population of PLWH on cART.

HIV, Vascular Risk Factors, and Cognition in the Combination Antiretroviral Therapy Era: A Systematic Review and Meta-Analysis

OBJECTIVES

Mounting evidence indicates that vascular risk factors (VRFs) are elevated in HIV and play a significant role in the development and persistence of HIV-associated neurocognitive disorder. Given the increased longevity of people living with HIV (PLWH), there is a great need to better elucidate vascular contributions to neurocognitive impairment in HIV. This systematic review and meta-analysis examine relationships between traditional VRFs, cardiovascular disease (CVD), and cognition in PLWH in the combination antiretroviral therapy era.

METHODS

For the systematic review, 44 studies met inclusion criteria and included data from 14,376 PLWH and 6,043 HIV-seronegative controls. To better quantify the contribution of VRFs to cognitive impairment in HIV, a robust variance estimation meta-analysis (N = 11 studies) was performed and included data from 2139 PLWH.

RESULTS

In the systematic review, cross-sectional and longitudinal studies supported relationships between VRFs, cognitive dysfunction, and decline, particularly in the domains of attention/processing speed, executive functioning, and fine motor skills. The meta-analysis demonstrated VRFs were associated with increased odds of global neurocognitive impairment (odds ratio [OR ]= 2.059, p = .010), which remained significant after adjustment for clinical HIV variables (p = .017). Analyses of individual VRFs demonstrated type 2 diabetes (p = .004), hyperlipidemia (p = .043), current smoking (p = .037), and previous CVD (p = .0005) were significantly associated with global neurocognitive impairment.

CONCLUSIONS

VRFs and CVD are associated with worse cognitive performance and decline, and neurocognitive impairment in PLWH. Future studies are needed to examine these relationships in older adults with HIV, and investigate how race/ethnicity, gender, medical comorbidities, and psychosocial factors contribute to VRF-associated cognitive dysfunction in HIV.

Additive and Synergistic Cardiovascular Disease Risk Factors and HIV Disease Markers' Effects on White Matter Microstructure in Virally Suppressed HIV

BACKGROUND

It is unclear whether intermediate to high cardiovascular disease (CVD) risk and HIV disease status may have additive (ie, independent statistical effects concomitantly tested) or synergistic effects on white matter microstructure and cognition in virally suppressed HIV-infected (HIV+) men relative to sex and age-matched controls.

SETTING

Tertiary health care observational cohort.

METHODS

Eighty-two HIV+ men (mean age 55 ± 6 years, 10%-30% on various CVD drugs; 20% with previous CVD) and 40 HIV-uninfected (HIV-) men (none with previous CVD; 10%-20% on various CVD drugs) underwent diffusion tensor imaging and neuropsychological testing. A standard classification of intermediate to high CVD risk (CVD+ group) was based on the Framingham score ≥15% cutoff and/or a history of CVD. Fractional anisotropy (FA) and mean diffusivity (MD) were quantified in 11 white matter tracts.

RESULTS

Within the HIV- group, the CVD+ group had lower FA (P = 0.03) and higher MD (P = 0.003) in the corona radiata and higher MD in the corpus callosum (P = 0.02) and superior fasciculi (P = 0.03) than the CVD- group. Within the HIV+ group, the CVD+ group had lower FA in the superior fasciculi (P = 0.04) and higher MD in the uncinate fasciculus (P = 0.04), and lower FA (P = 0.01) and higher MD (P = 0.03) in the fornix than the CVD- group. The fornix alterations were also abnormal compared with the HIV- groups. The HIV+ CVD+ was more likely to have HIV-associated dementia. Older age, antihypertensive use, longer HIV duration, and higher C-reactive protein associated with lower FA and higher MD. Higher blood CD4 lymphocyte count and CD4/CD8 ratio associated with higher FA and lower MD.

CONCLUSIONS

In virally suppressed HIV, CVD risk factors have a mostly additive contribution to white matter microstructural alterations, leading to a different distribution of injury in HIV- and HIV+ persons with CVD. There was also evidence of a synergistic effect of CVD and HIV factors on the fornix white matter injury.

Associations between Antiretrovirals and Cognitive Function in Women with HIV

Cognitive complications persist in antiretroviral therapy(ART)-treated people with HIV. However, the pattern and severity of domain-specific cognitive performance is variable and may be exacerbated by ART-mediated neurotoxicity. 929 women with HIV(WWH) from the Women's Interagency HIV Study who were classified into subgroups based on sociodemographic and longitudinal behavioral and clinical data using semi-parametric latent class trajectory modelling. Five subgroups were comprised of: 1) well-controlled HIV with vascular comorbidities(n = 116); 2) profound HIV legacy effects(CD4 nadir <250 cells/μL; n = 275); 3) primarily <45 year olds with hepatitis C(n = 165); 4) primarily 35-55 year olds(n = 244), and 5) poorly-controlled HIV/substance use(n = 129). Within each subgroup, we fitted a constrained continuation ratio model via penalized maximum likelihood to examine adjusted associations between recent ART agents and cognition. Most drugs were not associated with cognition. However, among the few drugs, non-nucleoside reverse transcriptase inhibitor (NNRTIs) and protease inhibitors(PIs) were most commonly associated with cognition, followed by nucleoside reverse transcriptase inhibitors(NRTIs) and integrase inhibitors(IIs). Directionality of ART-cognition associations varied by subgroup. Better psychomotor speed and fluency were associated with ART for women with well-controlled HIV with vascular comorbidities. This pattern contrasts women with profound HIV legacy effects for whom poorer executive function and fluency were associated with ART. Motor function was associated with ART for younger WWH and primarily 35-55 year olds. Memory was associated with ART only for women with poorly-controlled HIV/substance abuse. Findings demonstrate interindividual variability in ART-cognition associations among WWH and highlight the importance of considering sociodemographic, clinical, and behavioral factors as an underlying contributors to cognition. Are antiretroviral agents a risk factor for cognitive complications in women with HIV? We examind associations between ART-agents and cognitive function among similar subgroups of women with HIV from the Women's Interagency HIV study. The patterns of associations depended on sociodemographic, clinical, and behavioral characteristics of women.

Pathomechanisms of HIV-Associated Cerebral Small Vessel Disease: A Comprehensive Clinical and Neuroimaging Protocol and Analysis Pipeline

Rationale: We provide an in-depth description of a comprehensive clinical, immunological, and neuroimaging study that includes a full image processing pipeline. This approach, although implemented in HIV infected individuals, can be used in the general population to assess cerebrovascular health.

Aims: In this longitudinal study, we seek to determine the effects of neuroinflammation due to HIV-1 infection on the pathomechanisms of cerebral small vessel disease (CSVD). The study focuses on the interaction of activated platelets, pro-inflammatory monocytes and endothelial cells and their impact on the neurovascular unit. The effects on the neurovascular unit are evaluated by a novel combination of imaging biomarkers.

Sample Size: We will enroll 110 HIV-infected individuals on stable combination anti-retroviral therapy for at least three months and an equal number of age-matched controls. We anticipate a drop-out rate of 20%.

Methods and Design: Subjects are followed for three years and evaluated by flow cytometric analysis of whole blood (to measure platelet activation, platelet monocyte complexes, and markers of monocyte activation), neuropsychological testing, and brain MRI at the baseline, 18- and 36-month time points. MRI imaging follows the recommended clinical small vessel imaging standards and adds several advanced sequences to obtain quantitative assessments of brain tissues including white matter microstructure, tissue susceptibility, and blood perfusion.

Discussion: The study provides further understanding of the underlying mechanisms of CSVD in chronic inflammatory disorders such as HIV infection. The longitudinal study design and comprehensive approach allows the investigation of quantitative changes in imaging metrics and their impact on cognitive performance.

The regional pattern of abnormal cerebrovascular reactivity in HIV-infected, virally suppressed women

The purpose of this study was to assess whole brain and regional patterns of cerebrovascular reactivity (CVR) abnormalities in HIV-infected women using quantitative whole brain arterial spin labeling (ASL). We hypothesized that HIV-infected women would demonstrate decreased regional brain CVR despite viral suppression. This cross-sectional study recruited subjects from the Bay Area Women's Interagency Health Study (WIHS)-a cohort study designed to investigate the progression of HIV disease in women. In addition to conventional noncontrast cerebral MRI sequences, perfusion imaging was performed before and after the administration of intravenous acetazolamide. CVR was measured by comparing quantitative ASL brain perfusion before and after administration of intravenous acetazolamide. In order to validate and corroborate ASL-based whole brain and regional perfusion, phase-contrast (PC) imaging was also performed through the major neck vessels. FLAIR and susceptibility weighted sequences were performed to assess for white matter injury and microbleeds, respectively. Ten HIV-infected women and seven uninfected, age-matched controls were evaluated. Significant group differences were present in whole brain and regional CVR between HIV-infected and uninfected women. These regional differences were significant in the frontal lobe and basal ganglia. CVR measurements were not significantly impacted by the degree of white matter signal abnormality or presence of microbleeds. Despite complete viral suppression, dysfunction of the neurovascular unit persists in the HIV population. Given the lack of association between CVR and traditional imaging markers of small vessel disease, CVR quantification may provide an early biomarker of pre-morbid vascular disease.

Brain Perfusion, Regional Volumes, and Cognitive Function in Human Immunodeficiency Virus-positive Patients Treated With Protease Inhibitor Monotherapy

BACKGROUND

Protease inhibitor monotherapy (PIM) for human immunodeficiency virus (HIV) may exert suboptimal viral control in the central nervous system. We determined whether cerebral blood flow (CBF) and regional brain volumes were associated with PIM, and whether specific cognitive domains were associated with imaging biomarkers.

METHODS

Cognitive assessments and brain magnetic resonance imaging were performed after the final visit of a randomized HIV-treatment strategy trial. Participants were virologically suppressed on triple therapy at trial entry and followed for 3-5 years. We studied 37 patients randomized to ongoing triple therapy and 39 randomized to PIM. Resting CBF and normalized volumes were calculated for brain regions of interest, and correlated with treatment strategy and neuropsychological performance.

RESULTS

Mean age was 48.1 years (standard deviation 8.6 years), 63 male (83%), and 64 white (84%). Participants had median 8.1 years (interquartile range 6.4, 10.8) of antiretroviral therapy experience and CD4+ counts of median 640 cells/mm3 (interquartile range 490, 780). We found no difference between treatment arms in CBF or regional volumes. Regardless of treatment arm, poorer fine motor performance correlated with lower CBF in the caudate nucleus (P = .01), thalamus (P = .04), frontal cortex (P = .01), occipital cortex (P = .004), and cingulate cortex (P = .02), and was associated with smaller supratentorial white matter volume (decrease of 0.16 in Z-score per -1% of intracranial volume, 95% confidence interval 0.02-0.29; P = .023).

CONCLUSIONS

PIM does not confer an additional risk of neurological injury compared with triple therapy. There were correlations between fine motor impairment, grey matter hypoperfusion, and white matter volume loss.

CLINICAL TRIALS REGISTRATION

ISRCTN-04857074.

No Evidence for Accelerated Aging-Related Brain Pathology in Treated Human Immunodeficiency Virus: Longitudinal Neuroimaging Results From the Comorbidity in Relation to AIDS (COBRA) Project

Background

Despite successful antiretroviral therapy, people living with human immunodeficiency virus (PLWH) experience higher rates of age-related morbidity, including abnormal brain structure, brain function, and cognitive impairment. This has raised concerns that PLWH may experience accelerated aging-related brain pathology.

Methods

We performed a multicenter longitudinal study of 134 virologically suppressed PLWH (median age, 56.0 years) and 79 demographically similar human immunodeficiency virus (HIV)-negative controls (median age, 57.2 years). To measure cognitive performance and brain pathology, we conducted detailed neuropsychological assessments and multimodality neuroimaging (T1-weighted, T2-weighted, diffusion magnetic resonance imaging [MRI], resting-state functional MRI, spectroscopy, arterial spin labeling) at baseline and at 2 years. Group differences in rates of change were assessed using linear mixed effects models.

Results

One hundred twenty-three PLWH and 78 HIV-negative controls completed longitudinal assessments (median interval, 1.97 years). There were no differences between PLWH and HIV-negative controls in age, sex, years of education, smoking or alcohol use. At baseline, PLWH had poorer global cognitive performance (P < .01), lower gray matter volume (P = .04), higher white matter hyperintensity load (P = .02), abnormal white matter microstructure (P < .005), and greater brain-predicted age difference (P = .01). Longitudinally, there were no significant differences in rates of change in any neuroimaging measure between PLWH and HIV-negative controls (P > .1). Cognitive performance was longitudinally stable in both groups.

Conclusions

We found no evidence that middle-aged PLWH, when receiving successful treatment, are at increased risk of accelerated aging-related brain changes or cognitive decline over 2 years.

Cerebral blood flow in young and middle-aged people living with HIV

Purpose: Neurocognitive disorder has been noted as a long-term complication in individuals with HIV. In people living with HIV, regardless of treatment, age-related changes like arteriosclerosis are well-known to be accelerated. Such accelerated aging changes may decrease cerebral blood flow in younger generations with HIV, increasing the rate of occurrence of neurocognitive disorders. We investigated regional cerebral blood flows in well-controlled Japanese people living with HIV under 65 years old to clarify whether age-related changes in regional cerebral blood flows are accelerated in people living with HIV.Method: Japanese male HIV patients >20 years old but <65 years old who visited Teikyo University Hospital between August 2013 and September 2015 were recruited to and enrolled in this study. Healthy coeval male volunteers during the same period were recruited as controls. Magnetic resonance imaging was performed. Twelve regional cerebral blood flows were calculated from pseudocontinuous arterial spine labelling data.Results: Participants in this study comprised 40 individuals with HIV (HIV-positive group) and 33 non-HIV individuals (Control group). Median age was 40.15 years [interquartile range (IQR), 32.80-50.55 years] for the HIV-positive group and 48.00 years [IQR, 37.75-59.25 years; p = 0.3585] for the Control group. No significant differences in regional cerebral blood flows were seen between groups. In the HIV-positive group, cerebral blood flows decreased with age in the neocortex, although no significant decrease was observed in any of the regions in the control group.Conclusions: Significant age-related declines in cerebral blood flows in the neocortex may occur earlier in HIV patients.

Global HIV neurology: a comprehensive review

: Neurological conditions associated with HIV remain major contributors to morbidity and mortality and are increasingly recognized in the aging population on long-standing combination antiretroviral therapy (cART). Importantly, growing evidence shows that the central nervous system (CNS) may serve as a reservoir for viral replication, which has major implications for HIV eradication strategies. Although there has been major progress in the last decade in our understanding of the pathogenesis, burden, and impact of neurological conditions associated with HIV infection, significant scientific gaps remain. In many resource-limited settings, antiretrovirals considered second or third line in the United States, which carry substantial neurotoxicity, remain mainstays of treatment, and patients continue to present with severe immunosuppression and CNS opportunistic infections. Despite this, increased global access to cART has coincided with an aging HIV-positive population with cognitive sequelae, cerebrovascular disease, and peripheral neuropathy. Further neurological research in low-income and middle-income countries (LMICs) is needed to address the burden of neurological complications in HIV-positive patients, particularly regarding CNS viral reservoirs and their effects on eradication.

Abnormal Cerebral Perfusion Profile in Older Adults with HIV-Associated Neurocognitive Disorder: Discriminative Power of Arterial Spin-Labeling

BACKGROUND AND PURPOSE

The aging HIV-infected (HIV⁺) population has increased vascular comorbidities, including stroke, and increased cognitive deficits compared with the general population. Arterial spin-labeling is a technique to measure cerebral blood flow and is more sensitive than regional volume loss in assessing neurodegenerative diseases and cognitive aging. Previous studies have found global cerebral perfusion abnormalities in the HIV⁺ participants. In this study, we evaluated the specific regional pattern of CBF abnormalities in older HIV⁺ participants using quantitative whole-brain arterial spin-labeling.

MATERIALS AND METHODS

CBF data from the UCSF HIV Over 60 Cohort and the Alzheimer Disease Neuroimaging Initiative were retrospectively evaluated to identify 19 HIV⁺ older adults, all with plasma viral suppression (including 5 with HIV-associated neurocognitive disorder); 13 healthy, age-matched controls; and 19 participants with early mild cognitive impairment. CBF values were averaged by ROI and compared among the 3 groups using generalized linear models.

RESULTS

When we accounted for age, education, sex, and vascular risk factors, the HIV⁺ participants demonstrated alterations in regional cerebral perfusion, including hypoperfusion of bilateral temporal, parietal, and occipital brain regions compared with both clinically healthy participants and those with mild cognitive impairment. Arterial spin-labeling showed reasonable test characteristics in distinguishing those with HIV-associated neurocognitive disorder from healthy controls and participants with mild cognitive impairment.

CONCLUSIONS

This study found specific CBF patterns associated with HIV status despite viral suppression-data that should animate further investigations into the pathobiologic basis of vascular and cognitive abnormalities in HIV-associated neurocognitive disorders.

Microglial activation is inversely associated with cognition in individuals living with HIV on effective antiretroviral therapy

OBJECTIVE

Despite viral suppression, HIV-associated cognitive impairment persists and may be partially due to persistent immune signalling by cells of the myeloid-lineage. Here, we aimed to understand the contribution of activated microglia located in vulnerable brain regions (e.g. frontal, subcortical) of HIV-infected, virally suppressed (HIV+VS) individuals in relation to cognitive and motor function.

DESIGN

Twenty-one HIV+VS individuals underwent PET with [11C]DPA-713 to image the translocator protein 18 kDa (TSPO), a marker of microglial activation, and completed a comprehensive neuropsychological test battery.

METHODS

Multivariable linear regressions were used to examine the contribution of [11C]DPA-713 binding to cognitive performance.

RESULTS

Higher [11C]DPA-713 binding was associated with lower cognition among HIV+VS individuals. [11C]DPA-713 binding in middle frontal gyrus/frontal cortex, hippocampus/temporal cortex and occipital cortex was inversely associated with performance on a number of cognitive domains, including verbal memory, processing speed/attention/concentration, executive function, working memory and motor function. [C]DPA-713 binding in parietal cortex, cerebellum and thalamus was associated with only specific cognitive domains including visual construction and verbal memory. Binding was not associated with global cognitive performance.

CONCLUSION

The findings add to the growing body of evidence that immune-mediated brain injury may contribute to domain specific, HIV-associated, cognitive vulnerabilities despite viral suppression.

HIV-associated neurocognitive disorder

Human immunodeficiency virus (HIV)-associated neurocognitive disorder (HAND) affects roughly half the HIV-positive population. The symptoms of cognitive slowing, poor concentration, and memory problems can impact on everyday life. Its diagnosis is validated where possible by identifying deficits in two cognitive domains on neuropsychologic testing in patients either with or without symptoms. Corroborating evidence may be found on imaging, blood tests, and cerebrospinal fluid analysis, though sensitive and specific biomarkers are currently lacking. The introduction of combined antiretroviral therapy in the 1990s has generated a therapeutic paradox whereby the number of severe cases of HAND has fallen, yet milder forms continue to rise in prevalence. New emphasis has been placed on identifying the cause of apparent ongoing HIV infection and inflammation of the central nervous system (CNS) in the face of durable systemic viral suppression, and how this equates to the neuronal dysfunction underlying HAND. The interaction with aging and comorbidities is becoming increasingly common as the HIV-positive population enters older adulthood, with neurodegenerative, metabolic, and vascular causes of cognitive impairment combining and probably accelerating in the context of chronic HIV infection. Therapies targeted to the CNS, but without neurotoxic side-effects, are being investigated to attempt to reduce the likelihood of developing, and improving, HAND.

α7-Nicotinic acetylcholine receptor inhibition by indinavir: implications for cognitive dysfunction in treated HIV disease

OBJECTIVE

The study set out to determine if the HIV protease inhibitor, indinavir, alters responsiveness of α7-nicotinic acetylcholine receptors to acetylcholine.

DESIGN

Treatment with HAART has dramatically reduced development of HIV-associated dementia and more severe forms of cognitive impairment. However, many individuals continue to experience cognitive decline of uncertain cause. Previous studies have failed to demonstrate significant alterations of functional brain connectivity, structural brain changes, or changes in cerebral blood flow sufficient to explain cognitive decline in virally suppressed individuals. This suggests that the mechanisms underlying development and progression of cognitive problems likely occurs at a micro rather than macro level, such as disruptions in neurotransmitter system signaling.

MATERIALS AND METHODS

Indinavir's effects on α7-nicotinic acetylcholine receptor activity was tested using a ScreenPatch IonWorks Barracuda-based assay in a mammalian cell model.

RESULTS

At low concentrations (0.0003-10 μmol/l) indinavir acts as a positive allosteric modulator (EC50 = 0.021 μmol/l), whereas at concentrations greater than 10 μmol/l (30-100 μmol/l) indinavir acts as an inhibitor of the α7-nicotinic acetylcholine receptor.

CONCLUSION

At concentrations greater than 10 μmol/l indinavir reduces synaptic transmission in the acetylcholine neurotransmitter system, which could possibly contribute to cognitive dysfunction. These results suggest that further experiments should be considered to assess whether patients might benefit from treatment with cholinesterase inhibitors that counteract the effects of indinavir.