The coming problem of HIV-associated Alzheimer's disease

Nucleoside Reverse Transcriptase Inhibitor Exposure Is Associated with Lower Alzheimer's Disease Risk: A Retrospective Cohort Proof-of-Concept Study

Brain somatic gene recombination (SGR) and the endogenous reverse transcriptases (RTs) that produce it have been implicated in the etiology of Alzheimer's disease (AD), suggesting RT inhibitors as novel prophylactics or therapeutics. This retrospective, proof-of-concept study evaluated the incidence of AD in people with human immunodeficiency virus (HIV) with or without exposure to nucleoside RT inhibitors (NRTIs) using de-identified medical claims data. Eligible participants were aged ≥60 years, without pre-existing AD diagnoses, and pursued medical services in the United States from October 2015 to September 2016. Cohorts 1 (N = 46,218) and 2 (N = 32,923) had HIV. Cohort 1 had prescription claims for at least one NRTI within the exposure period; Cohort 2 did not. Cohort 3 (N = 150,819) had medical claims for the common cold without evidence of HIV or antiretroviral therapy. The cumulative incidence of new AD cases over the ensuing 2.75-year observation period was lowest in patients with NRTI exposure and highest in controls. Age- and sex-adjusted hazard ratios showed a significantly decreased risk for AD in Cohort 1 compared with Cohorts 2 (HR 0.88, p < 0.05) and 3 (HR 0.84, p < 0.05). Sub-grouping identified a decreased AD risk in patients with NRTI exposure but without protease inhibitor (PI) exposure. Prospective clinical trials and the development of next-generation agents targeting brain RTs are warranted.

Increasing Neuroinflammation Relates to Increasing Neurodegeneration in People with HIV

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Subjective cognitive decline disrupts aspects of prospective memory in older adults with HIV disease

Subjective cognitive decline (SCD) is a risk factor for dementia that may occur at higher rates in people with HIV (PWH). Prospective memory (PM) is an aspect of cognition that may help us better understand how SCD impacts daily life. Paricipants were 62 PWH aged ≥ 50 years and 33 seronegative individuals. SCD was operationalized as normatively elevated cognitive symptoms on standardized questionnaires, but with normatively unimpaired performance-based cognition and no current affective disorders. PM was measured with the Comprehensive Assessment of Prospective Memory (CAPM), the Cambridge Test of Prospective Memory (CAMPROMPT), and an experimental computerized time-based PM task. A logistic regression revealed that older PWH had a three-fold increased likelihood for SCD. Among the PWH, SCD was associated with more frequent PM symptoms and poorer accuracy on the time-based scale of the CAMPROMPT. These findings suggest that SCD disrupts PM in older PWH.

Alzheimer's Disease Pathology in Middle Aged and Older People with HIV: Comparisons with Non-HIV Controls on a Healthy Aging and Alzheimer's Disease Trajectory and Relationships with Cognitive Function

We determined the prevalence of Alzheimer's disease (AD) pathological hallmarks, amyloid-β and phosphorylated-Tau, in autopsied brains of 49 people with HIV (PWH) (ages: 50-68; mean age = 57.0) from the National NeuroAIDS Tissue Consortium and in a comparative cohort of 55 people without HIV (PWoH) from the UC San Diego Alzheimer's Disease Research Center (17 controls, 14 mild cognitive impairment, 24 AD; ages: 70-102, mean age = 88.7). We examined how AD pathology relates to domain-specific cognitive functions in PWH overall and in sex-stratified samples. Amyloid-β and phosphorylated-Tau positivity (presence of pathology of any type/density) was determined via immunohistochemistry in AD-sensitive brain regions. Among PWH, amyloid-β positivity ranged from 19% (hippocampus) to 41% (frontal neocortex), and phosphorylated-Tau positivity ranged from 47% (entorhinal cortex) to 73% (transentorhinal cortex). Generally, AD pathology was significantly less prevalent, and less severe when present, in PWH versus PWoH regardless of cognitive status. Among PWH, positivity for AD pathology related most consistently to memory-related domains. Positivity for p-Tau pathology related to memory-related domains in women with HIV only, although the sample size of women with HIV was small (n = 10). Results indicate that AD pathology is present in a sizable portion of middle aged and older PWH, although not to the extent in older PWoH. Studies with better age-matched PWoH are needed to examine the effect of HIV status on AD pathology.

HIV and FIV glycoproteins increase cellular tau pathology via cGMP-dependent kinase II activation

As the development of combination antiretroviral therapy (cART) against human immunodeficiency virus (HIV) drastically improves the lifespan of individuals with HIV, many are now entering the prime age when Alzheimer's disease (AD)-like symptoms begin to manifest. It has been shown that hyperphosphorylated tau, a known AD pathological characteristic, is prematurely increased in the brains of HIV-infected individuals as early as in their 30s and that its levels increase with age. This suggests that HIV infection might lead to accelerated AD phenotypes. However, whether HIV infection causes AD to develop more quickly in the brain is not yet fully determined. Interestingly, we have previously revealed that the viral glycoproteins HIV gp120 and feline immunodeficiency virus (FIV) gp95 induce neuronal hyperexcitation via cGMP-dependent kinase II (cGKII; also known as PRKG2) activation in cultured hippocampal neurons. Here, we use cultured mouse cortical neurons to demonstrate that the presence of HIV gp120 and FIV gp95 are sufficient to increase cellular tau pathology, including intracellular tau hyperphosphorylation and tau release to the extracellular space. We further reveal that viral glycoprotein-induced cellular tau pathology requires cGKII activation. Taken together, HIV infection likely accelerates AD-related tau pathology via cGKII activation.

Higher buccal mitochondrial DNA and mitochondrial common deletion number are associated with markers of neurodegeneration and inflammation in cerebrospinal fluid

Human immunodeficiency virus (HIV) infection is potentially associated with premature aging, but demonstrating this is difficult due to a lack of reliable biomarkers. The mitochondrial (mt) DNA "common deletion" mutation (mtCDM) is a 4977-bp deletion associated with aging and neurodegenerative diseases. We examined how mtDNA and mtCDM correlate with markers of neurodegeneration and inflammation in people with and without HIV (PWH and PWOH). Data from 149 adults were combined from two projects involving PWH (n = 124) and PWOH (n = 25). We measured buccal mtDNA and mtCDM by digital droplet PCR and compared them to disease and demographic characteristics and soluble biomarkers in cerebrospinal fluid (CSF) and blood measured by immunoassay. Participants had a median age of 52 years, with 53% white and 81% men. Median mtDNA level was 1,332 copies/cell (IQR 1,201-1,493) and median mtCDM level was 0.36 copies × 10²/cell (IQR 0.31-0.42); both were higher in PWH. In the best model adjusting for HIV status and demographics, higher mtDNA levels were associated with higher CSF amyloid-β 1-42 and 8-hydroxy-2'-deoxyguanosine and higher mtCDM levels were associated with higher plasma soluble tumor necrosis factor receptor II. The differences in mtDNA markers between PWH and PWOH support potential premature aging in PWH. Our findings suggest mtDNA changes in oral tissues may reflect CNS processes, allowing the use of inexpensive and easily accessible buccal biospecimens as a screening tool for CSF inflammation and neurodegeneration. Confirmatory and mechanistic studies on mt genome alterations by HIV and ART may identify interventions to prevent or treat neurodegenerative complications.

CSF markers of AD-related pathology relate specifically to memory impairment in older people with HIV: a pilot study

Given the co-occurrence of memory impairment in HIV-associated neurocognitive disorders (HAND) and amnestic mild cognitive impairment/Alzheimer's disease (aMCI/AD), biomarkers are needed that can disentangle these conditions among people with HIV (PWH). We assessed whether cerebrospinal fluid (CSF) markers of AD could help in this effort by determining their relationship to learning and memory deficits versus cognitive deficits more characteristic of HAND than aMCI/AD (processing speed and complex visual/motor coordination) among 31 older PWH. CSF amyloid-β₄₂ phosphorylated-tau, amyloid-β₄₀/amyloid-β₄₂ and phosphorylated-tau/amyloid-β₄₂ ratio related to learning/memory performance but not HAND-related deficits, suggesting that these biomarkers may have utility in disentangling aMCI/AD from HAND.

Current Considerations for Clinical Management and Care of People with HIV: Findings from the 11th Annual International HIV and Aging Workshop

The number of people with HIV (PWH) aged 50 years or older continues to steadily increase. The convergence of age- and HIV-related complications in these individuals presents a challenge for both patients and clinicians alike. New findings continue to emerge, as numerous researchers evaluate the combined impact of these two factors on quality of life, physiological systems, and mental health in PWH. Since its first occurrence in 2009, the International Workshop on HIV and Aging has served as a multidisciplinary meeting to share basic biomedical data, clinical trial results, treatment strategies, and epidemiological recommendations, toward better understanding and outcomes among like-minded scientific professionals. In this article, we share a selection of key findings presented in plenary talks at the 11th Annual International Workshop on HIV and Aging, held virtually from September 30, 2020 to October 2, 2020. We will also address the future directions of HIV and aging research, to further assess how the aging process intersects with chronic HIV.

Improved neurocognitive performance in FIV infected cats following treatment with the p75 neurotrophin receptor ligand LM11A-31

HIV rapidly infects the central nervous system (CNS) and establishes a persistent viral reservoir within microglia, perivascular macrophages and astrocytes. Inefficient control of CNS viral replication by antiretroviral therapy results in chronic inflammation and progressive cognitive decline in up to 50% of infected individuals with no effective treatment options. Neurotrophin based therapies have excellent potential to stabilize and repair the nervous system. A novel non-peptide ligand, LM11A-31, that targets the p75 neurotrophin receptor (p75^NTR) has been identified as a small bioavailable molecule capable of strong neuroprotection with minimal side effects. To evaluate the neuroprotective effects of LM11A-31 in a natural infection model, we treated cats chronically infected with feline immunodeficiency virus (FIV) with 13 mg/kg LM11A-31 twice daily over a period of 10 weeks and assessed effects on cognitive functions, open field behaviors, activity, sensory thresholds, plasma FIV, cerebrospinal fluid (CSF) FIV, peripheral blood mononuclear cell provirus, CD4 and CD8 cell counts and general physiology. Between 12 and 18 months post-inoculation, cats began to show signs of neural dysfunction in T maze testing and novel object recognition, which were prevented by LM11A-31 treatment. Anxiety-like behavior was reduced in the open field and no changes were seen in sensory thresholds. Systemic FIV titers were unaffected but treated cats exhibited a log drop in CSF FIV titers. No significant adverse effects were observed under all conditions. The data indicate that LM11A-31 is likely to be a potent adjunctive treatment for the control of neurodegeneration in HIV infected individuals.

Magnetic resonance imaging changes in Asian people living with HIV

BACKGROUND

Previous studies have reported a significant increase in age-related magnetic resonance imaging (MRI) changes in relatively younger people living with HIV (PLWH). However, there is little data available for brain changes in Asian PLWH. The data to differentiate HIV specific brain change from usual aging change was also sparse. To clarify them, we assessed the presence of leukoaraiosis and brain atrophic changes on MRI in young and middle-aged Japanese PLWH.

METHODS

We reviewed data from well-controlled PLWH (age: 20-64 years) and coeval controls. We evaluated the presence of leukoaraiosis, as well as the extent of whole-brain grey matter (GM) atrophy and parahippocampal atrophy on brain MRI and determined between-group differences. Moreover, we evaluated the severity of parahippocampal atrophy based on the voxel-based specific regional analysis system for Alzheimer's disease.

RESULTS

We enrolled 40 PLWH and 33 controls (median age: 40.15 and 48.00 years, respectively, [p = .3585]). Leukoaraiosis was significantly more prevalent among the PLWH (20 cases [50%]) than in the controls (9 cases [27.3%]) (univariate: p = .0483, multivariate: p = .0206). The extent of whole-brain GM atrophy was significantly greater in the PLWH than in the controls (univariate: p < .001, multivariate: p = .0012). Contrastingly, there was no significant between-group difference in the extent and severity of parahippocampal atrophy.

CONCLUSIONS

Aging changes in the brain were significantly more prevalent in well-controlled Japanese PLWH. However, the process of atrophic brain changes might differ between HIV and one of age-related diseases, Alzheimer's disease.

Beta amyloid levels in cerebrospinal fluid of HIV-infected people vary by exposure to antiretroviral therapy

BACKGROUND

HIV-associated neurocognitive disorders (HAND) persist despite the widespread implementation of combined antiretroviral therapy (ART). As people with HIV (PWH) age on ART regimens, the risk of age-related comorbidities, such as Alzheimer's disease may increase. However, questions remain as to whether HIV or ART will alter such risks. Beta amyloid (Aβ) and phosphorylated-tau (p-tau) proteins are associated with Alzheimer's disease and their levels are altered in the CSF of Alzheimer's disease cases.

METHODS

To better understand how these Alzheimer's disease-related markers are affected by HIV infection and ART, postmortem CSF collected from 70 well characterized HIV+ decedents was analyzed for Aβ1-42, Aβ1-40, and p-tau levels.

RESULTS

Aβ1-42 and Aβ1-40 CSF levels were higher in cases that were exposed to ART. Aβ1-42 and Aβ1-40 CSF levels were also higher in cases on protease inhibitors compared with those with no exposure to protease inhibitors. Aβ1-42 and Aβ1-40 levels in CSF were lowest in HIV+ cases with HIV-associated dementia (HAD) and levels were highest in those diagnosed with asymptomatic neurocognitive impairment (ANI) and minor neurocognitive disorder (MND). Aβ1-42 and Aβ1-40 were inversely related with p-tau levels in all cases, as previously reported.

CONCLUSION

These data suggest that ART exposure is associated with increased levels of Aβ1-42 and Aβ1-40 in the CSF. Also, HAD, but not ANI/MND diagnosis is associated with decreased levels of Aβ1-42 and Aβ1-40 in CSF, potentially suggesting impaired clearance. These data suggest that HIV infection and ART may impact pathogenic mechanisms involving Aβ1-42 and Aβ1-40, but not p-tau.

Mosaic Somatic Gene Recombination as a Potentially Unifying Hypothesis for Alzheimer's Disease

The recent identification of somatic gene recombination(SGR) in human neurons affecting the well-known Alzheimer's disease (AD) pathogenic gene, amyloid precursor protein (APP), has implications for the normal and the diseased human brain. The amyloid hypothesis has been the prevailing theory for sporadic AD (SAD) pathogenesis since the discovery of APP gene involvement in familial AD and Down syndrome. Yet, despite enormous scientific and clinical effort, no disease-modifying therapy has emerged. SGR offers a novel mechanism to explain AD pathogenesis and the failures of amyloid-related clinical trials, while maintaining consistency with most aspects of the amyloid hypothesis and additionally supporting possible roles for tau, oxidative stress, inflammation, infection, and prions. SGR retro-inserts novel "genomic complementary DNAs" (gencDNAs) into neuronal genomes and becomes dysregulated in SAD, producing numerous mosaic APP variants, including DNA mutations observed in familial AD. Notably, SGR requires gene transcription, DNA strand-breaks, and reverse transcriptase (RT) activity, all of which may be promoted by well-known AD risk factors and provide a framework for the pursuit of new SGR-based therapeutics. In this perspective, we review evidence for APP SGR in AD pathogenesis and discuss its possible relevance to other AD-related dementias. Further, SGR's requirement for RT activity and the relative absence of AD in aged HIV -infected patients exposed to RT inhibitors suggest that these Food and Drug Administration (FDA)-approved drugs may represent a near-term disease-modifying therapy for AD.

Longitudinal brain atrophy patterns and neuropsychological performance in older adults with HIV-associated neurocognitive disorder compared with early Alzheimer's disease

Older HIV-infected patients are at risk for both HIV-associated neurocognitive disorder (HAND) and Alzheimer's disease. We investigated neuroimaging and neuropsychological performance of 61 virally suppressed older adults with HAND (mean (SD) age 64.3 (3.9) years), 53 demographically matched individuals with mild cognitive impairment of the Alzheimer's type (MCI-AD; 65.0 [4.8]), and 89 healthy controls (65.0 [4.3]) cross-sectionally and over 20 months. At the baseline, both disease groups exhibited lower volumes in multiple cortical and subcortical regions compared with controls. Hippocampal volume differentiated MCI-AD from HAND. Cognitively, MCI-AD performed worse on memory and language compared with HAND. Adjusted longitudinal models revealed greater diffuse brain atrophy in MCI-AD compared with controls, whereas HAND showed greater atrophy in frontal gray matter and cerebellum compared with controls. Comparing HAND with MCI-AD showed similar atrophy rates in all brain regions explored, with no significant findings. MCI-AD exhibited more pronounced language decline compared with HAND. These findings reveal the need for further work on unique cognitive phenotypes and neuroimaging signatures of HAND compared with early AD, providing preliminary clinical insight for differential diagnosis of age-related brain dysfunction in geriatric neuroHIV.

HIV and Aging: Reconsidering the Approach to Management of Comorbidities

Health care for older adults with human immunodeficiency virus can be highly complex, resource intensive, and carry a high administrative burden. Data from aging longitudinal cohorts and feedback from the human immunodeficiency virus community suggest that the current model is not meeting the needs of these older adults. We introduce the 6 Ms approach, which acknowledges the multicomplexity of older adults with human immunodeficiency virus, simplifies geriatric principles for non-geriatrics-trained providers, and minimizes extensive training and specialized screening tests or tools. Implementing novel approaches to care requires support at local/national levels.

Frequency and Correlates of Subjective Cognitive Impairment in HIV Disease

The increasing prevalence of older adults living with HIV has raised growing concerns about a possible rise in the incidence of neurocognitive disorders due to HIV and other age-related factors. In typical aging, subjective cognitive impairment (SCI) among individuals with normal neurocognitive functioning may be an early manifestation of an incipient neurocognitive disorder. The current study examined the frequency and correlates of SCI in 188 HIV-infected adults without performance-based neurocognitive deficits or a current psychiatric disorder and 133 HIV seronegative comparison participants. All participants completed the Prospective and Retrospective Memory Questionnaire and Profile of Mood States Confusion/Bewilderment scale. Consistent with the diagnostic criteria proposed by Jessen et al. (Alzheimers Dement 10(6):844-852, 2014), participants were classified with SCI if their scores on either of the self-reported measures was greater than 1.5 SD above the normative mean. A logistic regression controlling for current mood complaints and lifetime history of substance use disorders revealed that HIV infection increased the odds of SCI (odds ratio= 4.5 [1.6, 15.4], p = 0.004). Among HIV+ individuals, SCI was associated with lower performance-based learning and delayed memory scores (Cohen's d range 0.41-0.42.) and poorer global everyday functioning (odds ratio= 8.5 [2.6, 15.9]), but not HIV disease severity (ps > 0.10). In a sample of individuals without neurocognitive impairment or elevated mood symptoms, HIV disease was associated with a nearly fivefold increased odds of SCI compared to seronegative individuals, which may indicate an increased risk for developing major neurocognitive disorders as these HIV+ individuals age.

Inflammation: Bridging Age, Menopause and APOEε4 Genotype to Alzheimer's Disease

Neuro-inflammatory processes that contribute to development of Alzheimer’s are evident early in the latent prodromal phase and worsen during the course of the disease. Despite substantial mechanistic and clinical evidence of inflammation, therapeutic approaches targeting inflammation have failed to alter the course of the disease. Disparate results from epidemiological and clinical trials targeting inflammation, highlight the complexity of the inflammatory process. Herein we review the dynamics of the inflammatory process across aging, midlife endocrine transitions, and the APOEε4 genotype and their contribution to progression of Alzheimer’s disease (AD). We discuss the chronic inflammatory processes that are activated during midlife chronological and endocrine aging, which ultimately limit the clearance capacity of microglia and lead to immune senescence. Aging, menopause, and APOEε4 combine the three hits of a compromised bioenergetic system of menopause with the chronic low grade innate inflammation of aging with the APOEε4 dyslipidemia and adaptive immune response. The inflammatory immune response is the unifying factor that bridges across each of the risk factors for AD. Immune system regulators that are specific to stage of disease and inflammatory phenotype would provide a therapeutic strategy to disconnect the bridge that drives disease. Outcomes of this analysis provide plausible mechanisms underlying failed clinical trials of anti-inflammatory agents in Alzheimer’s patients. Further, they highlight the need for stratifying AD clinical trial cohorts based on inflammatory phenotype. Combination therapies that include targeted use of anti-inflammatory agent’s specific to the immune phenotype are considered.

Mechanisms of Cognitive Aging in the HIV-Positive Adult

PURPOSE OF REVIEW

As of the year 2016, an estimated 50% of the United States' HIV-Positive population is aged 50 years or older. Due to a combination of increased rates of infection in older adults, and successful anti-retroviral (ART) regimens allowing HIV-positive adults to survive for decades with the disease, we are now faced with a steadily graying HIV-positive population, with only limited knowledge of how the cognitive and physiological effects of aging intersect with those of chronic HIV-infection.

RECENT FINDINGS

Age-related changes to mood, cognition, and neurological health may be experienced differently in those living with HIV, and research concerning quality of life, mental health, and cognitive aging needs to account for and explore these factors more carefully in the coming years.

SUMMARY

This review will explore the topic of cognitive aging with HIV: 1. Central nervous system (CNS) infection of HIV and how the virus affects brain integrity and function; 2. Cognitive and behavioral symptoms of HIV-Associated Neurocognitive Disorders (HAND); 3. Neurobiological theories of Cognitive Aging and how these processes may be exacerbated by HIV-infection; 4: Clinical implications and complications of aging with HIV and factors that may result in poorer cognitive outcomes.

Verbal list learning and memory profiles in HIV-infected adults, Alzheimer's disease, and Parkinson's disease: An evaluation of the "cortical hypothesis" of NeuroAIDS

HIV+ population is getting older because of progress in treatments. Yet, there are concerns that Older HIV+ individuals (OHIV+) may be more vulnerable for developing a "cortical" dementia such as Alzheimer Disease (AD). Our aim was to explore the hypothesis that the cognitive deficit extends to ''cortical'' functions in OHIV+ by comparing serial position effects (SPE) in different groups of participants affected by "cortical" or "subcortical" damage. We enrolled a total of 122 subjects: 22 OHIV+ (≥60 years of age), 31 Younger HIV+ (YHIV+) (<60 years of age), 18 participants with AD, 23 subjects with Parkinson Disease (PD), and 28 healthy subjects. All subjects performed verbal learning tasks (VLT) to explore SPE. Factorial analysis of covariance showed a significant effect of "group" (p < 0.001) and "task" (Primacy vs Recency) (p < 0.001), but no significant group*task (p = 0.257) interaction. Compared with healthy subjects (p = 0.003), AD had the most severe reduction of Primacy, confirming a primary "encoding deficit," while PD confirmed a "frontal pattern." OHIV+ showed a memory profile similar to that of PD with a worsening of the cognitive performance in comparison with YHIV+. In conclusion, we did not confirm the "cortical" hypothesis in OHIV+, at least in terms of learning and memory functions.

Risk Profiles of Alzheimer Disease

Alzheimer disease (AD) is a dementing, neurodegenerative disorder that affects approximately 500,000 Canadians and its prevalence is expected to double over the next 30 years. Although several medications may temporarily augment cognitive abilities in AD, there presently exists no proven method to avoid the inevitable clinical deterioration in this devastating condition. The delineation of risk factors for the development of AD offers hope for the advent of effective prevention or interventions that might retard the onset of symptoms. In this article, we provide a comprehensive review of midlife risk factors implicated in the etiopathogenesis of sporadic AD. Although some risk factors are heritable and largely beyond our control, others are determined by lifestyle or environment and are potentially modifiable. In a companion paper, we introduce the concept of an Alzheimer Risk Assessment Clinic for ascertainment and mitigation of these and other putative dementia risk factors in middle-aged adults.

The role of tau protein in HIV-associated neurocognitive disorders

Given the increased life expectancy of human immunodeficiency virus (HIV) infected individuals treated with combination antiretroviral therapy (cART) and the ongoing inflammation observed in the brains of these patients, it is likely that premature neurodegeneration as measured by phospho-tau (p-tau) or increased total tau (t-tau) protein may become an increasing problem. This review examines the seven human studies that have occurred over the past 14 years measuring p-tau and/or t-tau in cerebrospinal fluid (CSF) or via post-mortem brain immunohistochemistry. Although not all studies are in agreement as to the changes in p-and t-tau in HIV infected patients, HIV persists in the brain despite cART. Thus is it is suggested that those maintained on long-term cART may develop tau pathology beyond the extent seen in the studies reviewed herein and overtime may then reach the threshold for clinical manifestation.

Efavirenz promotes β-secretase expression and increased Aβ1-40,42 via oxidative stress and reduced microglial phagocytosis: implications for HIV associated neurocognitive disorders (HAND)

Efavirenz (EFV) is among the most commonly used antiretroviral drugs globally, causes neurological symptoms that interfere with adherence and reduce tolerability, and may have central nervous system (CNS) effects that contribute in part to HIV associated neurocognitive disorders (HAND) in patients on combination antiretroviral therapy (cART). Thus we evaluated a commonly used EFV containing regimen: EFV/zidovudine (AZT)/lamivudine (3TC) in murine N2a cells transfected with the human “Swedish” mutant form of amyloid precursor protein (SweAPP N2a cells) to assess for promotion of amyloid-beta (Aβ) production. Treatment with EFV or the EFV containing regimen generated significantly increased soluble amyloid beta (Aβ), and promoted increased β-secretase-1 (BACE-1) expression while 3TC, AZT, or, vehicle control did not significantly alter these endpoints. Further, EFV or the EFV containing regimen promoted significantly more mitochondrial stress in SweAPP N2a cells as compared to 3TC, AZT, or vehicle control. We next tested the EFV containing regimen in Aβ - producing Tg2576 mice combined or singly using clinically relevant doses. EFV or the EFV containing regimen promoted significantly more BACE-1 expression and soluble Aβ generation while 3TC, AZT, or vehicle control did not. Finally, microglial Aβ phagocytosis was significantly reduced by EFV or the EFV containing regimen but not by AZT, 3TC, or vehicle control alone. These data suggest the majority of Aβ promoting effects of this cART regimen are dependent upon EFV as it promotes both increased production, and decreased clearance of Aβ peptide.

Cognitive impairment in HIV infection is associated with MRI and CSF pattern of neurodegeneration

BACKGROUND AND PURPOSE

Biomarkers as indicators for the progression of human immunodeficiency virus (HIV)-associated neurocognitive disorders (HAND) remain still elusive. We performed a cross-sectional study to analyze the correlation between cognitive impairment, abnormalities in magnetic resonance imaging (MRI), and cerebrospinal fluid (CSF) markers of neurodegeneration in HIV-infected patients.

METHODS

We enrolled 94 patients (82 men and 12 women; mean age 45 ± 10 years) with HIV infection, but without opportunistic infections of the CNS. All patients underwent MRI and CSF analysis. The global pattern of white matter signal intensity abnormalities, the index of atrophy, the severity of periventricular white matter abnormalities, and the severity of basal ganglia signal changes were analyzed. We measured CSF markers of neurodegeneration (total tau, phospho-tau, beta-amyloid). The findings of this evaluation were correlated with demographic and infection parameters of the patients in blood and CSF.

RESULTS

We found a highly significant correlation between the severity of global brain atrophy, basal ganglia signal changes, and cognitive impairment in HIV-infected patients. Furthermore, cognitive impairment was significantly correlated with total tau, but not with phospho-tau or A-beta-amyloid in CSF analysis.

CONCLUSIONS

Our results confirm the significant correlation between MRI changes and cognitive impairment in HIV infection. Furthermore, we could show that global brain atrophy and signal changes in basal ganglia are the typical MRI pattern in HAND. The correlation between cognitive impairment and total tau, but not phospho-tau, supports the hypothesis that HAND are not a subtype of Alzheimer's dementia.

Common transcriptional signatures in brain tissue from patients with HIV-associated neurocognitive disorders, Alzheimer's disease, and Multiple Sclerosis

HIV-Associated Neurocognitive Disorders (HAND) is a common manifestation of HIV infection that afflicts about 50 % of HIV-positive individuals. As people with access to antiretroviral treatments live longer, HAND can be found in increasing segments of populations at risk for other chronic, neurodegenerative conditions such as Alzheimer’s disease (AD) and Multiple Sclerosis (MS). If brain diseases of diverse etiologies utilize similar biological pathways in the brain, they may coexist in a patient and possibly exacerbate neuropathogenesis and morbidity. To test this proposition, we conducted comparative meta-analysis of selected publicly available microarray datasets from brain tissues of patients with HAND, AD, and MS. In pair-wise and three-way analyses, we found a large number of dysregulated genes and biological processes common to either HAND and AD or HAND and MS, or to all three diseases. The common characteristic of all three diseases was up-regulation of broadly ranging immune responses in the brain. In addition, HAND and AD share down-modulation of processes involved, among others, in synaptic transmission and cell-cell signaling while HAND and MS share defective processes of neurogenesis and calcium/calmodulin-dependent protein kinase activity. Our approach could provide insight into the identification of common disease mechanisms and better intervention strategies for complex neurocognitive disorders.

Impact of HIV and aging on neuropsychological function

Cognitive efficiency decreases with age, and advancing age is the leading risk factor for most neurodegenerative disorders that result in dementia. In HIV infection, risk for cognitive impairment is consistently linked to advancing chronological age. As the HIV epidemic enters its fourth decade in the USA, extended life expectancy will likely result in an increased prevalence of cognitive disorders by virtue of these factors. However, it is less clear if HIV potentiates or accelerates the risk for cognitive impairment given that most reports are mixed or demonstrate only a small interaction effect. More critically, it is unclear if HIV will modulate the neuropathology associated with non-HIV cognitive disorders in a manner that will increase risk for diseases such as cerebrovascular and Alzheimer's disease. In the coming years, with increasing numbers of HIV+ patients entering their 60s and 70s, background risk for neurodegenerative disorders will be sufficiently high as to inform this issue on clinical grounds. This review summarizes knowledge of cognition in HIV as it relates to age and presents some emerging controversies.

DHA supplemented in peptamen diet offers no advantage in pathways to amyloidosis: is it time to evaluate composite lipid diet?

Numerous reports have documented the beneficial effects of dietary docosahexaenoic acid (DHA) on beta-amyloid production and Alzheimer's disease (AD). However, none of these studies have examined and compared DHA, in combination with other dietary nutrients, for its effects on plaque pathogenesis. Potential interactions of DHA with other dietary nutrients and fatty acids are conventionally ignored. Here we investigated DHA with two dietary regimes; peptamen (pep+DHA) and low fat diet (low fat+DHA). Peptamen base liquid diet is a standard sole-source nutrition for patients with gastrointestinal dysfunction. Here we demonstrate that a robust AD transgenic mouse model shows an increased tendency to produce beta-amyloid peptides and amyloid plaques when fed a pep+DHA diet. The increase in beta-amyloid peptides was due to an elevated trend in the levels of beta-secretase amyloid precursor protein (APP) cleaving enzyme (BACE), the proteolytic C-terminal fragment beta of APP and reduced levels of insulin degrading enzyme that endoproteolyse beta-amyloid. On the contrary, TgCRND8 mice on low fat+DHA diet (based on an approximately 18% reduction of fat intake) ameliorate the production of abeta peptides and consequently amyloid plaques. Our work not only demonstrates that DHA when taken with peptamen may have a tendency to confer a detrimental affect on the amyloid plaque build up but also reinforces the importance of studying composite lipids or nutrients rather than single lipids or nutrients for their effects on pathways important to plaque development.

HIV-associated dementia in older adults: clinical and tomographic aspects

BACKGROUND

Elderly adults with human immunodeficiency virus (HIV) are at greater risk of developing cognitive impairment. The purpose of this study was to describe clinical and tomographic characteristics of HIV-1 associated dementia (HIVD) in older adults.

METHODS

A descriptive study was carried out involving eight HIVD patients. Seven tests were employed for cognitive assessment and transformed to whole number z-scores using appropriate normative sets.

RESULTS

The average age of the patients was 71 years; seven cases described the route of HIV infection as being heterosexual; and mean schooling was 6.5 years. Six subjects were using highly active anti-retroviral therapy (HAART), with an average CD4 count of 407.8 cells/mm3. Mild dementia was detected in most cases (87.5%). Deficits on neuropsychological tests showed results similar to multi-center transversal studies on HIVD. The classic HIVD triad observed in younger adults was also seen in this population: i.e. cognitive changes, psychiatric changes and motor impairment. Cortical injury shown by dyscalculia, visual-spatial change and language deficits were frequent. Brain images showed cortical atrophy in all patients but was restricted to frontal lobes in five cases.

CONCLUSION

The findings on brain imaging were non-specific, revealing images similar to those of the elderly brain and to HIVD in younger adults. HIVD in the elderly is a challenge and become an increasingly significant differential diagnosis for cognitive loss in old age. This dementia must be clinically suspected and image exams are useful in excluding other central disorders. Prospective studies of HIV-positive elderly people are warranted to better understand HIVD.

Neurocognitive consequences of HIV infection in older adults: an evaluation of the "cortical" hypothesis

The incidence and prevalence of older adults living with HIV infection is increasing. Recent reports of increased neuropathologic and metabolic alterations in older HIV+ samples, including increased cortical beta-amyloid, have led some researchers to suggest that aging with HIV may produce a neuropsychological profile akin to that which is observed in “cortical” dementias (e.g., impairment in memory consolidation). To evaluate this possibility, we examined four groups classified by HIV serostatus and age (i.e., younger ≤40 years and older ≥50 years): (1) Younger HIV− (n = 24); (2) Younger HIV+ (n = 24); (3) Older HIV− (n = 20); and (4) Older HIV+ (n = 48). Main effects of aging were observed on episodic learning and memory, executive functions, and visuoconstruction, and main effects of HIV were observed on measures of verbal learning and memory. The interaction of age and HIV was observed on a measure of verbal recognition memory, which post hoc analyses showed to be exclusively attributed to the superior performance of the younger HIV seronegative group. Thus, in this sample of older HIV-infected individuals, the combined effects of HIV and aging do not appear to result in a “cortical” pattern of cognitive deficits.

Flipping the switches: CD40 and CD45 modulation of microglial activation states in HIV associated dementia (HAD)

Microglial dysfunction is associated with the pathogenesis and progression of a number of neurodegenerative disorders including HIV associated dementia (HAD). HIV promotion of an M1 antigen presenting cell (APC) - like microglial phenotype, through the promotion of CD40 activity, may impair endogenous mechanisms important for amyloid- beta (Aβ) protein clearance. Further, a chronic pro-inflammatory cycle is established in this manner. CD45 is a protein tyrosine phosphatase receptor which negatively regulates CD40L-CD40-induced microglial M1 activation; an effect leading to the promotion of an M2 phenotype better suited to phagocytose and clear Aβ. Moreover, this CD45 mediated activation state appears to dampen harmful cytokine production. As such, this property of microglial CD45 as a regulatory "off switch" for a CD40-promoted M1, APC-type microglia activation phenotype may represent a critical therapeutic target for the prevention and treatment of neurodegeneration, as well as microglial dysfunction, found in patients with HAD.

First evidence of overlaps between HIV-Associated Dementia (HAD) and non-viral neurodegenerative diseases: proteomic analysis of the frontal cortex from HIV+ patients with and without dementia

Background

The pathogenesis of HIV-associated dementia (HAD) is poorly understood. To date, detailed proteomic fingerprinting directly from autopsied brain tissues of HAD and HIV non-dementia patients has not been performed.

Result

Here, we have analyzed total proteins from the frontal cortex of 9 HAD and 5 HIV non-dementia patients. Using 2-Dimensional differential in-gel electrophoresis (2-DIGE) to analyze the brain tissue proteome, 76 differentially expressed proteins (p < 0.05; fold change>1.25) were identified between HAD and HIV non-dementia patients, of which 36 protein spots (based on 3D appearance of spots on the images) were chosen for the mass spectrometry analysis. The large majority of identified proteins were represented in the energy metabolic (mitochondria) and signal transduction pathways. Furthermore, over 90% of the protein candidates are common to both HAD and other non-viral neurodegenerative disease, such as Alzheimer's disease. The data was further validated using specific antibodies to 4 proteins (CA2, GS, CKMT and CRMP2) by western blot (WB) in the same samples used for 2D-DIGE, with additional confirmation by immunohistochemitsry (IHC) using frontal lobe tissue from different HAD and HIV+ non-dementia patients. The validation for all 4 antibodies by WB and IHC was in concordance with the DIGE results, lending further credence to the current findings.

Conclusion

These results suggest not only convergent pathogenetic pathways for the two diseases but also the possibility of increased Alzheimer's disease (AD) susceptibility in HAD patients whose life expectancy has been significantly increased by highly active antiretroviral therapy.

Nanolipidic particles improve the bioavailability and alpha-secretase inducing ability of epigallocatechin-3-gallate (EGCG) for the treatment of Alzheimer's disease

Prevention of amyloidogenic processing of amyloid precursor protein with the use of natural phytochemicals capable of enhancing alpha-secretase activity may be a therapeutic approach for treatment of neurodegenerative diseases including Alzheimer's disease (AD) and HIV-associated dementia (HAD). We have recently shown promising preclinical results with the use of green tea polyphenol, (-)-epigallocatechin-3-gallate (EGCG) in mouse models of both diseases, however the translation into clinical use has been problematic primarily as a result of poor bioavailability and inefficient delivery to the central nervous system (CNS). While the antioxidant properties of EGCG are well known, we have shown that it is able to promote non-amyloidogenic processing of amyloid precursor protein (APP) by upregulating alpha-secretase, thus preventing brain beta amyloid plaque formation, a hallmark of AD pathology and common finding in HIV infection. In this preliminary study, we investigated the ability of one preformulation method to improve the oral bioavailability of EGCG. We found that forming nanolipidic EGCG particles improves the neuronal (SweAPP N2a cells) alpha-secretase enhancing ability in vitro by up to 91% (P<001) and it's oral bioavailability in vivo by more than two-fold over free EGCG.

Amyloid and tau cerebrospinal fluid biomarkers in HIV infection

Background

Because of the emerging intersections of HIV infection and Alzheimer's disease, we examined cerebrospinal fluid (CSF) biomarkers related of amyloid and tau metabolism in HIV-infected patients.

Methods

In this cross-sectional study we measured soluble amyloid precursor proteins alpha and beta (sAPPα and sAPPβ), amyloid beta fragment 1-42 (Aβ_1-42), and total and hyperphosphorylated tau (t-tau and p-tau) in CSF of 86 HIV-infected (HIV+) subjects, including 21 with AIDS dementia complex (ADC), 25 with central nervous system (CNS) opportunistic infections and 40 without neurological symptoms and signs. We also measured these CSF biomarkers in 64 uninfected (HIV-) subjects, including 21 with Alzheimer's disease, and both younger and older controls without neurological disease.

Results

CSF sAPPα and sAPPβ concentrations were highly correlated and reduced in patients with ADC and opportunistic infections compared to the other groups. The opportunistic infection group but not the ADC patients had lower CSF Aβ_1-42 in comparison to the other HIV+ subjects. CSF t-tau levels were high in some ADC patients, but did not differ significantly from the HIV+ neuroasymptomatic group, while CSF p-tau was not increased in any of the HIV+ groups. Together, CSF amyloid and tau markers segregated the ADC patients from both HIV+ and HIV- neuroasymptomatics and from Alzheimer's disease patients, but not from those with opportunistic infections.

Conclusions

Parallel reductions of CSF sAPPα and sAPPβ in ADC and CNS opportunistic infections suggest an effect of CNS immune activation or inflammation on neuronal amyloid synthesis or processing. Elevation of CSF t-tau in some ADC and CNS infection patients without concomitant increase in p-tau indicates neural injury without preferential accumulation of hyperphosphorylated tau as found in Alzheimer's disease. These biomarker changes define pathogenetic pathways to brain injury in ADC that differ from those of Alzheimer's disease.

Clinical and behavioural aspects of aging with HIV infection

Scant attention has been paid to the effects of ageing and HIV. This study examined age distribution and explored the impact of age on the experience of illness. One thousand and seven consecutive attenders at five UK HIV clinics were approached, 904 met inclusion criteria and 778 agreed to participate (86% response rate). They provided detailed information on demographics, experience of illness, physical and psychological symptoms, quality of life, treatment experience and doctor-patient communications. Twelve percent were aged over 50. There were significantly more males in the over 50s (86% vs. 75%), more gay males x(2) = 7, p = 0.04 and fewer females (14% vs. 25%) x(2) = 5; p = 0.03. No significant differences were found on measures of education, employment or migration status or physical symptom experience. The older group had significantly lower psychological and global burden scores and were more likely to take antiretrovirals (88% vs. 79%; p = 0.04). Triggers for treatment switching showed older participants significantly less burdened by food restrictions, pill burden, taste, nausea, diarrhoea, sleep disturbance, concentration problems, anxiety depression, skin rashes, liver complaints or a need for a simpler regimen. The older group were similar in employment, education and disclosure, but complained less and reported much higher tolerance.