Human immunodeficiency virus-associated dementia: an evolving disease

Unravelling the triad of neuroinvasion, neurodissemination, and neuroinflammation of human immunodeficiency virus type 1 in the central nervous system

Since the identification of human immunodeficiency virus type 1 (HIV-1) in 1983, many improvements have been made to control viral replication in the peripheral blood and to treat opportunistic infections. This has increased life expectancy but also the incidence of age-related central nervous system (CNS) disorders and HIV-associated neurodegeneration/neurocognitive impairment and depression collectively referred to as HIV-associated neurocognitive disorders (HAND). HAND encompasses a spectrum of different clinical presentations ranging from milder forms such as asymptomatic neurocognitive impairment or mild neurocognitive disorder to a severe HIV-associated dementia (HAD). Although control of viral replication and suppression of plasma viral load with combination antiretroviral therapy has reduced the incidence of HAD, it has not reversed milder forms of HAND. The objective of this review, is to describe the mechanisms by which HIV-1 invades and disseminates in the CNS, a crucial event leading to HAND. The review will present the evidence that underlies the relationship between HIV infection and HAND. Additionally, recent findings explaining the role of neuroinflammation in the pathogenesis of HAND will be discussed, along with prospects for treatment and control.

Headaches and Vasculitis

Vasculitis refers to heterogeneous clinicopathologic disorders that share the histopathology of inflammation of blood vessels. Unrecognized and therefore untreated, vasculitis of the nervous system leads to pervasive injury and disability making this a disorder of paramount importance to all clinicians. Headache may be an important clue to vasculitic involvement of central nervous system (CNS) vessels. CNS vasculitis may be primary, in which only intracranial vessels are involved in the inflammatory process, or secondary to another known disorder with overlapping systemic involvement. Primary neurologic vasculitides can be diagnosed with assurance after intensive evaluation that incudes tissue confirmation whenever possible.

Virus-induced brain pathology and the neuroinflammation-inflammation continuum: the neurochemists view

Fascinatingly, an abundance of recent studies has subscribed to the importance of cytotoxic immune mechanisms that appear to increase the risk/trigger for many progressive neurodegenerative disorders, including Parkinson's disease (PD), Alzheimer's disease (AD), amyotrophic lateral sclerosis, and multiple sclerosis. Events associated with the neuroinflammatory cascades, such as ageing, immunologic dysfunction, and eventually disruption of the blood-brain barrier and the "cytokine storm", appear to be orchestrated mainly through the activation of microglial cells and communication with the neurons. The inflammatory processes prompt cellular protein dyshomeostasis. Parkinson's and Alzheimer's disease share a common feature marked by characteristic pathological hallmarks of abnormal neuronal protein accumulation. These Lewy bodies contain misfolded α-synuclein aggregates in PD or in the case of AD, they are Aβ deposits and tau-containing neurofibrillary tangles. Subsequently, these abnormal protein aggregates further elicit neurotoxic processes and events which contribute to the onset of neurodegeneration and to its progression including aggravation of neuroinflammation. However, there is a caveat for exclusively linking neuroinflammation with neurodegeneration, since it's highly unlikely that immune dysregulation is the only factor that contributes to the manifestation of many of these neurodegenerative disorders. It is unquestionably a complex interaction with other factors such as genetics, age, and environment. This endorses the "multiple hit hypothesis". Consequently, if the host has a genetic susceptibility coupled to an age-related weakened immune system, this makes them more susceptible to the virus/bacteria-related infection. This may trigger the onset of chronic cytotoxic neuroinflammatory processes leading to protein dyshomeostasis and accumulation, and finally, these events lead to neuronal destruction. Here, we differentiate "neuroinflammation" and "inflammation" with regard to the involvement of the blood-brain barrier, which seems to be intact in the case of neuroinflammation but defect in the case of inflammation. There is a neuroinflammation-inflammation continuum with regard to virus-induced brain affection. Therefore, we propose a staging of this process, which might be further developed by adding blood- and CSF parameters, their stage-dependent composition and stage-dependent severeness grade. If so, this might be suitable to optimise therapeutic strategies to fight brain neuroinflammation in its beginning and avoid inflammation at all.

Advances in 3D bioprinting of tissues/organs for regenerative medicine and in-vitro models

Tissue/organ shortage is a major medical challenge due to donor scarcity and patient immune rejections. Furthermore, it is difficult to predict or mimic the human disease condition in animal models during preclinical studies because disease phenotype differs between humans and animals. Three-dimensional bioprinting (3DBP) is evolving into an unparalleled multidisciplinary technology for engineering three-dimensional (3D) biological tissue with complex architecture and composition. The technology has emerged as a key driver by precise deposition and assembly of biomaterials with patient's/donor cells. This advancement has aided in the successful fabrication of in vitro models, preclinical implants, and tissue/organs-like structures. Here, we critically reviewed the current state of 3D-bioprinting strategies for regenerative therapy in eight organ systems, including nervous, cardiovascular, skeletal, integumentary, endocrine and exocrine, gastrointestinal, respiratory, and urinary systems. We also focus on the application of 3D bioprinting to fabricated in vitro models to study cancer, infection, drug testing, and safety assessment. The concept of in situ 3D bioprinting is discussed, which is the direct printing of tissues at the injury or defect site for reparative and regenerative therapy. Finally, issues such as scalability, immune response, and regulatory approval are discussed, as well as recently developed tools and technologies such as four-dimensional and convergence bioprinting. In addition, information about clinical trials using 3D printing has been included.

HIV Dementia: A Bibliometric Analysis and Brief Review of the Top 100 Cited Articles

Dementia is a syndrome of cognitive impairment that affects an individual’s ability to live independently. The number of people living with dementia worldwide in 2015 was estimated at 47.47 million. The American Academy of Neurology (AAN) criteria for human immunodeficiency virus (HIV)-associated dementia (HAD) require an acquired abnormality in at least two cognitive (non-motor) domains and either an abnormality in motor function or specified neuropsychiatric/psychosocial domains. HIV is the most common cause of dementia below 60 years of age.

Citation frequencies are commonly used to assess the scholarly impact of any scientific publication in bibliometric analyses. It helps depict areas of higher interest in terms of research frequency and trends of citations in the published literature and identify under-explored domains of any field, providing useful insight and guidance for future research avenues. We used the database “Web of Science” (WOS) to search for the top 100 cited articles on HIV-associated dementia. The keywords “HIV dementia” and “HIV-associated neurocognitive disorders” (HAND) were used. The list was generated by two authors after excluding articles not pertaining to HIV dementia. The articles were then assigned to authors to extract data to make tables and graphical representations. Finally, the manuscript was organized and written describing the findings of the bibliometric study.

These 100 most cited articles on HIV dementia were published between years 1986 and 2016. The highest number of the articles was from 1999 (n=9). The year 1993-2007 contributed consistently two publications to the list. The articles are from 42 journals, and among them, the Annals of Neurology (n=16) and the Journal of Neurology (n=15) published most of the articles. Justin C. McArthur with 25 publications contributed the highest number of papers to the list by any author. The USA collaborated in the highest number of publications (n=87). American institutes were leading the list with the most publications. The Johns Hopkins University collaborated on 37 papers. The most widely studied aspect of HIV dementia was pathogenesis. Incidence and prevalence, clinical features, and pre- and post-highly active antiretroviral therapy (HAART) era were also discussed in the articles.

Beyond America, the research should be expanded to low-income countries and those affected more by HIV. Therefore, other countries and their institutes should participate more in HIV-associated dementia research. Anticipating the rising resistance to existing antiretrovirals, we should develop new therapeutic options. There is room for research in many aspects of HIV dementia care.

A systematic review and meta-analysis of HIV associated neurocognitive disorders (HAND) among people with HIV in Ethiopia

Background

Ethiopia, being in the Sub Saharan region of Africa, is one of the countries with a substantial burden of HIV infection. Because of the high burden of HIV and poor health care settings, HAND is prevalent as demonstrated in various cross-sectional studies. However, no review has been conducted to report the consolidated magnitude of HAND among people with HIV in Ethiopia. Therefore, this systematic review and meta-analysis aimed to estimate the prevalence of HAND in Ethiopia.

Methods

Following the PRISMA guidelines, we systematically reviewed and meta-analyzed studies that investigated the prevalence of HAND in Ethiopia from PubMed, Google Scholar, Science Direct, HINARI, EMBASE, and Cochrane library databases. We also looked at the reference lists of the included studies to include other relevant studies. Subgroup analysis was performed based on publication year, study location, and sample size. Heterogeneity across studies was evaluated using the I2 test. Potential publication bias was assessed using Egger’s test and visual inspection of symmetry in the funnel plots.

Results

In the present meta-analysis, 627 articles were initially identified and evaluated. Of these, 8 studies that met the inclusion criteria were included in the final analysis. The pooled prevalence of HAND in people with HIV in Ethiopia was 39.15% (95% CI 29.36, 48.94). The highest prevalence observed in the Southern Nations, Nationalities, and Peoples’ Region (SNNPR) with 53.20% (95% CI 25.96, 80.44) followed by others 34.87% (Tigray, Addis Ababa, and Oromia) (95% CI 33.49, 36.24) and Amhara 34.07% (95% CI 25.39, 42.74).The funnel plot was asymmetrical. However, Egger’s regression tests provided no evidence of publication bias in the prevalence of HAND.

Conclusion

In this meta-analysis, the pooled prevalence of HAND, in Ethiopia, was high. Older age, substance use, advanced stages of the disease, and lack of education were the main determinants of HAND in Ethiopia. Health education, early screening of people with HIV, and training of health professionals working in hospitals on HAND are highly recommended.

Depression and HIV associated neurocognitive disorders among HIV infected adults in rural southwestern Uganda: a cross-sectional quantitative study

BACKGROUND

HIV-Associated Neurocognitive Disorder (HAND remains a pronounced consequence of HIV/AIDS despite improved life expectancies. This is often associated with several dysfunctions such as decrease of attention, mood alterations and psychomotor disturbances. Many factors, including age, gender, employment status, and psychiatric disorders, have been associated with HAND. Among the associated psychiatric disorders, depression is often more prevalent. It can influence not only quality of life, relationships and employment but also adherence to medical care. We assessed the prevalence of depression and its association with HAND among people living with HIV in rural Southwestern Uganda.

METHODS

This was a cross-sectional study that used Beck Depression Inventory-1 and International HIV Dementia Scale to assess depression and HAND respectively. We defined depression with a score of > 10 and HAND with a cutoff score of ≤10. We conducted data analysis using STATA version 12, and Pearson Chi-square test and logistic regression to determine associations between depression and HAND. The level of statistical significance was set at p ≤ 0.05. Ethical approval and administrative clearance were obtained from relevant bodies.

RESULTS

Of the 393 participants assessed for depression and HAND, 27% had depression and 58.3% screened positive for HAND. All levels of depression were more prevalent among female participants. We found a significant association between depression and HIV associated neurocognitive disorders (χ2 (3) = 9.0538 p = 0.029).

CONCLUSION

Our findings confirmed a high prevalence of depression in individuals with HAND which is a major component of the disease burden.

Beneficial and Adverse Effects of cART Affect Neurocognitive Function in HIV-1 Infection: Balancing Viral Suppression against Neuronal Stress and Injury

HIV-associated neurocognitive disorders (HAND) persist despite the successful introduction of combination antiretroviral therapy (cART). While insufficient concentration of certain antiretrovirals (ARV) may lead to incomplete viral suppression in the brain, many ARVs are found to cause neuropsychiatric adverse effects, indicating their penetration into the central nervous system (CNS). Several lines of evidence suggest shared critical roles of oxidative and endoplasmic reticulum stress, compromised neuronal energy homeostasis, and autophagy in the promotion of neuronal dysfunction associated with both HIV-1 infection and long-term cART or ARV use. As the lifespans of HIV patients are increased, unique challenges have surfaced. Longer lives convey prolonged exposure of the CNS to viral toxins, neurotoxic ARVs, polypharmacy with prescribed or illicit drug use, and age-related diseases. All of these factors can contribute to increased risks for the development of neuropsychiatric conditions and cognitive impairment, which can significantly impact patient well-being, cART adherence, and overall health outcome. Strategies to increase the penetration of cART into the brain to lower viral toxicity may detrimentally increase ARV neurotoxicity and neuropsychiatric adverse effects. As clinicians attempt to control peripheral viremia in an aging population of HIV-infected patients, they must navigate an increasingly complex myriad of comorbidities, pharmacogenetics, drug-drug interactions, and psychiatric and cognitive dysfunction. Here we review in comparison to the neuropathological effects of HIV-1 the available information on neuropsychiatric adverse effects and neurotoxicity of clinically used ARV and cART. It appears altogether that future cART aiming at controlling HIV-1 in the CNS and preventing HAND will require an intricate balancing act of suppressing viral replication while minimizing neurotoxicity, impairment of neurocognition, and neuropsychiatric adverse effects. Graphical abstract Schematic summary of the effects exerted on the brain and neurocognitive function by HIV-1 infection, comorbidities, psychostimulatory, illicit drugs, therapeutic drugs, such as antiretrovirals, the resulting polypharmacy and aging, as well as the potential interactions of all these factors.

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.

Drug Resistance Mutation Frequency of Single-Genome Amplification-Derived HIV-1 Polymerase Genomes in the Cerebrospinal Fluid and Plasma of HIV-1-Infected Individuals under Nonsuppressive Therapy

HIV-1 evolution in the cerebrospinal fluid (CSF) and plasma may result in discordant drug resistance mutations (DRMs) in the compartments. Single-genome amplification (SGA) was used to generate partial HIV-1 polymerase genomes in paired CSF and plasma samples from 12 HIV-1-positive participants in the CNS HIV Antiretroviral Therapy Effects Research (CHARTER) study who were classified as neurocognitively unimpaired or with various degrees of HIV-associated neurocognitive disorders (HAND). Subjects were viremic on combination antiretroviral therapy (cART). HIV-1 DRMs and phylogenetic characteristics were determined using the Stanford HIVdb program and phylogenetic analyses. Individual DRMs were identified more frequently in plasma than in paired CSF (P = 0.0078). Significant differences in the ratios of DRMs in CSF and plasma were found in 3 individuals with HAND (3/7 = 43%). Two HAND subjects (2/7 = 29%) demonstrated one DRM in CSF not identified in paired plasma. Longitudinal analyses (n = 4) revealed significant temporal differences in the ratios of DRMs in the compartments. Statistically significant differences in the frequency of DRMs in the CSF and plasma are readily found in those on nonsuppressive cART. While compartment-based DRM discordance was largely consistent with increased drug-selective pressures in the plasma, overrepresentation of DRMs in the central nervous system (CNS) can occur. Underlying mechanisms of HAND are complex and multifactorial. The clinical impact of DRM discordance on viral persistence and HAND pathogenesis remains unclear and warrants further investigation in larger, longitudinal cohorts.IMPORTANCE Several antiretroviral agents do not efficiently enter the CNS, and independent evolution of HIV-1 viral variants in the CNS and plasma can occur. We used single-genome amplification (SGA) in cross-sectional and longitudinal analyses to uniquely define both the identity and relative proportions of drug resistance mutations (DRMs) on individual HIV-1 polymerase genomes in the cerebrospinal fluid (CSF) and plasma in individuals with incomplete viral suppression and known neurocognitive status. Statistically significant differences in the ratio of DRMs in the CSF and plasma were readily found in those on nonsuppressive cART, and overrepresentation of DRMs in the CNS can occur. Although questions about the clinical significance of DRM discordance remain, in the quest for viral eradication, it is important to recognize that a significant, dynamic, compartment-based DRM ratio imbalance can exist, as it has the potential to go unnoticed in the setting of standard clinical drug resistance testing.

Antiretroviral therapy improves neurocognitive impairment in people living with HIV? A meta-analysis

Objectives

Although effective antiretroviral therapy (ART) has been used for more than two decades, HIV-associated neurocognitive disorder remains prevalent. Thus, whether ART can improve neurocognitive impairment is controversial. This review aims to explore the effects of ART on cognitive impairment in people living with HIV (PLWH).

Methods

A systematic literature search was conducted in eight databases (PubMed, Embase, Web of Science, Cochrane Library, CNKI, VIP, China Biology Medicine disc, and WanFang) to identify studies that compare cognitive function between study groups who are administered and not administered ART. We searched for articles published up to April 2019. Article evaluation and data extraction were independently conducted by two reviewers.

Results

Sixteen articles (6,694 participants)—14 cross-sectional studies and 2 cohort studies—were included in this meta-analysis. The cross-sectional studies demonstrated that ART group did not perform better than the non-ART group (OR = 1.16; 95% CI, 1.03–1.30). However, the cohort studies reported a significant improvement in cognitive function at three months (OR = 4.01; 95% CI, 2.35–6.85) and six months (OR = 9.24; 95% CI, 1.71–49.96) after ART initiation compared with the baseline data. No significant cognitive improvement was found in participants younger than 55 years old, but the two cross-sectional studies showed that ART may improve cognitive function in PLWH under 65 years old with poor physical condition and immune status.

Conclusions

ART could improve cognitive function in PLWH with poor physical condition and immune status, but it does not considerably improve cognition in the entire PLWH population.

Nitrosative Stress Is Associated with Dopaminergic Dysfunction in the HIV-1 Transgenic Rat

Advances in antiretroviral therapy have resulted in significantly decreased HIV-related mortality. HIV-associated neurocognitive disorders, however, continue to be a major problem in infected patients. The neuropathology underlying HIV-associated neurocognitive disorders has not been well characterized, and evidence suggests different contributing mechanisms. One potential mechanism is the induction of oxidative stress. Using the HIV-1 transgenic (Tg) rat model of HIV, we found increased striatal NADPH oxidase-4 and neuronal nitric oxide synthase expression in the adult (7- to 9-month-old) Tg rat compared with control rats but not in the young (1-month-old) Tg rats. This was accompanied by increased 3-nitrotyrosine (3-NT) immunostaining in the adult Tg rats, which worsened significantly in the old Tg rats (18 to 20 months old). There was, however, no concurrent induction of the antioxidant systems because there was no change in the expression of the nuclear factor-erythroid 2-related factor 2 and its downstream targets (thioredoxin and glutathione antioxidant systems). Colocalization of 3-NT staining with neurofilament proteins and evidence of decreased tyrosine hydroxylase and dopamine transporter expression in the old rats support dopaminergic involvement. We conclude that the HIV-1 Tg rat brain shows evidence of nitrosative stress without appropriate oxidation-reduction adaptation, whereas 3-NT modification of striatal neurofilament proteins likely points to the ensuing dopaminergic neuronal loss and dysfunction in the aging HIV-1 Tg rat.

HIV-Associated Vacuolar Myelopathy and HIV-Associated Dementia as the Initial Manifestation of HIV/AIDS

HIV-associated vacuolar myelopathy (HIV-VM) is the most common cause of spinal disease in HIV/AIDS. HIV-VM causes progressive spastic paraparesis, sensory ataxia, and autonomic dysfunction. It is a progressive myelopathy that shares features with subacute combined degeneration seen in vitamin B12 deficiency as well as other neurological diseases and can occur synchronously with HIV-associated dementia (HAD). Here, we describe a rare case in which a patient's initial presentation of HIV/AIDS was both HIV-VM and HAD. A fifty-three-year-old man presented with a six-month history of numerous falls due to progressive gait instability with associated memory loss, tremor, urinary retention, and impotence. His exam was significant for hyperreflexia and weakness in bilateral lower extremities, upgoing plantar reflex, dysmetria, and ataxic gait. MRI-brain was notable for nonspecific volume loss and diffusely increased T2 signal throughout the supratentorial white matter. Lumbar puncture showed isolated lymphocytic pleocytosis with all other CSF testing unremarkable. He ultimately tested positive for HIV-1, with a CD4 count of 157 cells/mm³ and a viral load of 874,000 copies/mL. He was diagnosed with HIV-VM and HAD which improved after several months of antiretroviral therapy. This case highlights the importance of considering HIV testing in a patient with a sensory neuropathy and/or progressive cognitive impairment.

HIV-1 Tat-Induced Astrocytic Extracellular Vesicle miR-7 Impairs Synaptic Architecture

Although combination antiretroviral therapy (cART) has improved the health of millions of those living with HIV-1 (Human Immunodeficiency Virus, Type 1), the penetration into the central nervous system (CNS) of many such therapies is limited, thereby resulting in residual neurocognitive impairment commonly referred to as NeuroHIV. Additionally, while cART has successfully suppressed peripheral viremia, cytotoxicity associated with the presence of viral Transactivator of transcription (Tat) protein in tissues such as the brain, remains a significant concern. Our previous study has demonstrated that both HIV-1 Tat as well as opiates such as morphine, can directly induce synaptic alterations via independent pathways. Herein, we demonstrate that exposure of astrocytes to HIV-1 protein Tat mediates the induction and release of extracellular vesicle (EV) microRNA-7 (miR-7) that is taken up by neurons, leading in turn, to downregulation of neuronal neuroligin 2 (NLGN2) and ultimately to synaptic alterations. More importantly, we report that these impairments could be reversed by pretreatment of neurons with a neurotrophic factor platelet-derived growth factor-CC (PDGF-CC).

N-Substituted Pyrrole Derivative 12m Inhibits HIV-1 Entry by Targeting Gp41 of HIV-1 Envelope Glycoprotein

The combination of three or more antiviral agents that act on different targets is known as highly active antiretroviral therapy (HAART), which is widely used to control HIV infection. However, because drug resistance and adverse effects occur after long-term administration, an increasing number of HIV/AIDS patients do not tolerate HAART. It is necessary to continue developing novel anti-HIV drugs, particularly HIV entry/fusion inhibitors. Our group previously identified a small-molecule compound, NB-64, with weak anti-HIV activity. Here, we found that N-substituted pyrrole derivative 12m (NSPD-12m), which was derived from NB-64, had strong anti-HIV-1 activity, and NSPD-12m-treated cells showed good viability. The mechanism of action of NSPD-12m might be targeting the gp41 transmembrane subunit of the HIV envelope glycoprotein, thus inhibiting HIV entry. Site-directed mutagenesis confirmed that a positively charged lysine residue (K574) located in the gp41 pocket region is pivotal for the binding of NSPD-12m to gp41. These findings suggest that NSPD-12m can serve as a lead compound to develop novel virus entry inhibitors.

Molecular Signatures of HIV-1 Envelope Associated with HIV-Associated Neurocognitive Disorders

PURPOSE OF REVIEW

The HIV-1 envelope gene (env) has been an intense focus of investigation in the search for genetic determinants of viral entry and persistence in the central nervous system (CNS).

RECENT FINDINGS

Molecular signatures of CNS-derived HIV-1 env reflect the immune characteristics and cellular constraints of the CNS compartment. Although more readily found in those with advanced HIV-1 and HIV-associated neurocognitive disorders (HAND), molecular signatures distinguishing CNS-derived quasispecies can be identified early in HIV-1 infection, in the presence or absence of combination antiretroviral therapy (cART), and are dynamic. Amino acid signatures of CNS-compartmentalization and HAND have been identified across populations. While some significant overlap exists, none are universal. Detailed analyses of CNS-derived HIV-1 env have allowed researchers to identify a number of molecular determinants associated with neuroadaptation. Future investigations using comprehensive cohorts and longitudinal databases have the greatest potential for the identification of robust, validated signatures of HAND in the cART era.

Type I Interferons in NeuroHIV

Infection with Human Immunodeficiency Virus (HIV)-1 continues to cause HIV-associated neurocognitive disorders despite combined antiretroviral therapy. Interferons (IFNs) are important for any antiviral immune response, but the lasting production of IFNα causes exhaustive activation leading eventually to progression to AIDS. Expression of IFNα in the HIV-exposed central nervous system has been linked to cognitive impairment and inflammatory neuropathology. In contrast, IFNβ exerts anti-inflammatory effects, appears to control, at least temporarily, lentiviral infection in the brain and provides neuroprotection. The dichotomy of type I IFN effects on HIV-1 infection and the associated brain injury will be discussed in this review, because the underlying mechanisms require further investigation to allow harnessing these innate immune factors for therapeutic purposes.

Neurocognitive and mental health outcomes and association with quality of life among adults living with HIV: a cross-sectional focus on a low-literacy population from coastal Kenya

OBJECTIVES

Our aim was to compare the neurocognitive performance and mental health outcome of adults living with HIV on antiretroviral therapy with that of community controls, all of low literacy. Furthermore, we also wanted to explore the relationship of these outcomes with quality of life among adults living with HIV.

STUDY DESIGN

This was a descriptive cross-sectional study.

SETTING

The study was conducted in Kilifi County, a region located at the Kenyan coast.

PARTICIPANTS

The participants consisted of a consecutive sample of 84 adults living with HIV and 83 randomly selected community controls all with ≤8 years of schooling. All participants were assessed for non-verbal intelligence, verbal working memory and executive functioning. The Major Depression Inventory and a quality of life measure (RAND SF-36) were also administered.

RESULTS

Using analysis of covariance, we found no statistically significant group differences between adults living with HIV and community controls in all the neurocognitive tests except for a marginal difference in the non-verbal intelligence test (F (1, 158)=3.83, p=0.05). However, depressive scores of adults living with HIV were significantly higher than those of controls (F (1, 158)=11.56, p<0.01). Also, quality of life scores of adults living with HIV were significantly lower than those of controls (F (1, 158)=4.62, p=0.03). For the HIV-infected group, results from multivariable linear regression analysis showed that increasing depressive scores were significantly associated with poorer quality of life (β=-1.17, 95% CI -1.55 to -0.80; p<0.01).

CONCLUSION

Our findings suggest that adults of low-literacy levels living with HIV and on antiretroviral medication at the Kenyan coast do not have significant cognitive deficits compared with their uninfected counterparts. However, their mental health, compared with that of HIV-uninfected adults, remains poorer and their quality of life may deteriorate when HIV and depressive symptoms co-occur.

Modulatory Effects of Nicotine on neuroHIV/neuroAIDS

Nicotine, one of the key active ingredients in tobacco smoke, exerts its effects via binding to nicotinic acetylcholine receptors (nAChRs). Although both negative and positive pharmacological effects of nicotine have been shown in numerous animals and human studies, its interaction with human immunodeficiency virus-1 (HIV-1) have not been fully elucidated. Even though combined anti-retroviral therapy (cART) limits the progression of HIV-1 to acquired immune deficiency syndrome (AIDS), HIV-associated neurocognitive disorders (HAND) remain prevalent. There is thus a compelling need to enhance our understanding of HAND-related neurologic dysfunction. Some biochemical pathways and physiological dysfunctions have been found to be shared by HAND and Alzheimer's (AD) or Parkinson's (PD) diseases, and nicotine may exert the same neuroprotection in HAND that has been observed in both AD and PD. In the past dozen years, various potential therapeutic effects of nicotine such as neuroprotection have been revealed in both in vivo and in vitro studies, including using HIV-1 transgenic (HIV-1Tg) rat model, which mimics HIV-infected patients receiving cART. In the current review, we describe recent progress in the prevalence of HIV/AIDS with and without cigarette smoking, some animal models for studying neural dysfunction associated with HIV-1 infection, elucidating the modulatory effects of cigarette smoking/nicotine on HIV/AIDS, the anti-inflammatory effects of nicotine, and the neuroprotective effects observed in HIV-1Tg rat model. Taken together, these findings suggest the following: although tobacco smoking does cause deleterious effects in both health and disease conditions such as HIV infection, nicotine, the significant component of tobacco smoke, has been shown to possess some neuroprotective effects in HIV patients, possible via its anti-inflammatory activities. It is therefore necessary to study nicotine's dual effects on neuroHIV/neuroAIDS in hope of better defining the potential medical uses of nicotine or its analogues, and to make them available in a purer and less dangerous form.

HIV Neuroinfection and Alzheimer's Disease: Similarities and Potential Links?

Environmental factors such as chemicals, stress and pathogens are now widely believed to play important roles in the onset of some brain diseases, as they are associated with neuronal impairment and acute or chronic inflammation. Alzheimer’s disease (AD) is characterized by progressive synaptic dysfunction and neurodegeneration that ultimately lead to dementia. Neuroinflammation also plays a prominent role in AD and possible links to viruses have been proposed. In particular, the human immunodeficiency virus (HIV) can pass the blood-brain barrier and cause neuronal dysfunction leading to cognitive dysfunctions called HIV-associated neurocognitive disorders (HAND). Similarities between HAND and HIV exist as numerous factors involved in AD such as members of the amyloid and Tau pathways, as well as stress-related pathways or blood brain barrier (BBB) regulators, seem to be modulated by HIV brain infection, leading to the accumulation of amyloid plaques or neurofibrillary tangles (NFT) in some patients. Here, we summarize findings regarding how HIV and some of its proteins such as Tat and gp120 modulate signaling and cellular pathways also impaired in AD, suggesting similarities and convergences of these two pathologies.

Macrophages but not Astrocytes Harbor HIV DNA in the Brains of HIV-1-Infected Aviremic Individuals on Suppressive Antiretroviral Therapy

The question of whether the human brain is an anatomical site of persistent HIV-1 infection during suppressive antiretroviral therapy (ART) is critical, but remains unanswered. The presence of virus in the brains of HIV patients whose viral load is effectively suppressed would demonstrate not only the potential for CNS to act as an anatomical HIV reservoir, but also the urgent need to understand the factors contributing to persistent HIV behind the blood-brain barrier. Here, we investigated for the first time the presence of cells harboring HIV DNA and RNA in the brains from subjects with undetectable plasma viral load and sustained viral suppression, as identified by the National NeuroAIDS Tissue Consortium. Using new, highly sensitive in situ hybridization techniques, RNAscope and DNAscope, in combination with immunohistochemistry, we were able to detect HIV-1 in the brains of all virally suppressed cases and found that brain macrophages and microglia, but not astrocytes, were the cells harboring HIV DNA in the brain. This study demonstrated that HIV reservoirs persist in brain macrophages/microglia during suppressive ART, which cure/treatment strategies will need to focus on targeting.

Impact of glycemic status on longitudinal cognitive performance in men with and without HIV infection

OBJECTIVES

To determine the relationship between glycemic status and cognitive performance in men living with HIV (MLWH) and without HIV infection.

DESIGN

A prospective HIV/AIDS cohort study in four US cities between 1999 and 2016.

METHODS

Glycemic status was categorized as normal glucose, impaired fasting glucose, controlled diabetes mellitus and uncontrolled diabetes mellitus at each semiannual visit. Cognitive performance was evaluated using nine neuropsychological tests which measure attention, constructional ability, verbal learning, executive functioning, memory and psychomotor speed. Linear mixed models were used to assess the association between glycemic status and cognition.

RESULTS

Overall, 900 MLWH and 1149 men without HIV were included. MLWH had significantly more person-visits with impaired fasting glucose (52.1 vs. 47.9%) and controlled diabetes mellitus (58.2 vs. 41.8%) than men without HIV (P < 0.05). Compared with men with normal glucose, men with diabetes mellitus had significantly poorer performance on psychomotor speed, executive function and verbal learning (all P < 0.05). There was no difference in cognition by HIV serostatus. The largest effect was observed in individuals with uncontrolled diabetes mellitus throughout the study period, equivalent to 16.5 and 13.4 years of aging on psychomotor speed and executive function, respectively, the effect of which remained significant after adjusting for HIV-related risk factors. Lower CD4+ nadir was also associated with worse cognitive performance.

CONCLUSION

Abnormalities in glucose metabolism were more common among MLWH than men without HIV and were related to impaired cognitive performance. Metabolic status, along with advanced age and previous immunosuppression, may be important predictors of cognition in the modern antiretroviral therapy era.

3-Hydroxyphthalic Anhydride- Modified Rabbit Anti-PAP IgG as a Potential Bifunctional HIV-1 Entry Inhibitor

Several studies have reported that amyloid fibrils in human semen formed from a naturally occurring peptide fragment of prostatic acidic phosphatase (PAP248-286), known as semen-derived enhancer of viral infection (SEVI), could dramatically enhance human immunodeficiency virus type 1 (HIV-1) infection. Accordingly, SEVI might serve as a novel target for new antiviral drugs or microbicide candidates for the prevention of sexually transmitted HIV. Theoretically, a special anti-PAP or anti-SEVI antibody could reduce the enhancement of viral infection by blocking the binding of HIV and SEVI fibrils. Here, 3-hydroxyphthalic anhydride modified anti-PAP248-286 antibody, named HP-API, exhibited broad-spectrum and highly effective anti-HIV-1 activities on different subtypes and tropism. By using time-of-addition, cell–cell fusion and a single-cycle HIV-1 infection assays, we demonstrated that HP-API is an HIV-1 entry/fusion inhibitor. Mechanism studies suggest that HP-API inhibited HIV-1 entry/fusion by targeting both HIV-1 gp120 envelop and CD4 receptor on the host cell specifically. It is noteworthy that HP-API abrogated the formation of SEVI fibrils and partially interfered with SEVI-mediated enhancement of HIV-1 infection. Based on these findings, HP-API could be considered a bifunctional HIV-1 entry/fusion inhibitor with high potential.

Trilobatin as an HIV-1 entry inhibitor targeting the HIV-1 Gp41 envelope

HIV-1 transmembrane protein gp41 plays a crucial role by forming a stable six-helix bundle during HIV entry. Due to highly conserved sequence of gp41, the development of an effective and safe small-molecule compound targeting gp41 is a good choice. Currently, natural polyanionic ingredients with anti-HIV activities have aroused concern. Here, we first discovered that a glycosylated dihydrochalcone, trilobatin, exhibited broad anti-HIV-1 activity and low cytotoxicity in vitro. Site-directed mutagenesis analysis suggested that the hydrophobic residue (I564) located in gp41 pocket-forming site is pivotal for anti-HIV activity of trilobatin. Furthermore, trilobatin displayed synergistic anti-HIV activities combined with other antiretroviral agents. Trilobatin has a good potential to be developed as a small-molecule HIV-1 entry inhibitor for clinical combination therapy.

Effect of matrix metalloproteinase-21 (572C/T) polymorphism on HIV-associated neurocognitive disorder

Remodeling of extracellular matrix (ECM) by matrix metalloproteinases (MMPs) is a presumed reason for the development of HIV-associated neurocognitive disorders (HAND). The coding region polymorphism in MMP-21 572C/T gene may have a potential functional effect on ECM remodeling. Hence, we aimed to examine the association of MMP-21 polymorphism with the modulation of HAND severity and its prevalence in HIV-infected and healthy individuals. Genotyping of MMP-21 572C/T polymorphism was performed by PCR-RFLP in total 150 HIV-infected individuals, 50 with HAND, 100 without HAND and 150 healthy controls. MMP-21 572TT genotype was predominantly higher in HAND patients compared with no HAND (OR = 1.63, p = 0.57). MMP-21 572T allele was associated with reduce risk for HAND severity (OR = 0.50, p = 0.04). Similarly, MMP-21 572TT genotype underrepresented in HIV-infected individuals compared to healthy controls (3.0% vs 6.7%, OR = 0.27, p = 0.08). MMP-21 572CT genotype and early HIV disease stage showed a higher risk for the advancement of HIV disease with marginal significance (OR = 1.89, p = 0.07). MMP-21 572CT genotype increased the risk for the modulation of HAND severity in tobacco users (OR = 1.98, p = 0.43). MMP-21 572CT genotype among tobacco and alcohol users showed elevated risk for the development of HAND in HIV-infected individuals (OR = 2.30, p = 0.15; OR = 1.86, p = 0.23). Similarly, MMP-21 572TT genotype enhanced the risk for the development of HAND in tobacco users (OR = 3.48, p = 0.40). In conclusion, the presence of coding region 572T allele may have protection for HAND severity. MMP-21 572C/T polymorphism and tobacco and alcohol usage may facilitate the development of HAND.

Exosomal miR-9 Released from HIV Tat Stimulated Astrocytes Mediates Microglial Migration

Chronic neuroinflammation still remains a common underlying feature of HIV-infected patients on combined anti-retroviral therapy (cART). Previous studies have reported that despite near complete suppression of virus replication by cART, cytotoxic viral proteins such as HIV trans-activating regulatory protein (Tat) continue to persist in tissues such as the brain and the lymph nodes, thereby contributing, in part, to chronic glial activation observed in HIV-associated neurological disorders (HAND). Understanding how the glial cells cross talk to mediate neuropathology is thus of paramount importance. MicroRNAs (miR) also known as regulators of gene expression, have emerged as key paracrine signaling mediators that regulate disease pathogenesis and cellular crosstalk, through their transfer via the extracellular vesicles (EV). In the current study we have identified a novel function of miR-9, that of mediating microglial migration. We demonstrate that miR-9 released from Tat-stimulated astrocytes can be taken up by microglia resulting in their migratory phenotype. Exposure of human astrocytoma (A172) cells to HIV Tat resulted in induction and release of miR-9 in the EVs, which, was taken up by microglia, leading in turn, increased migration of the latter cells, a process that could be blocked by both an exosome inhibitor GW4869 or a specific target protector of miR-9. Furthermore, it was also demonstrated that EV miR-9 mediated inhibition of the expression of target PTEN, via its binding to the 3'UTR seed sequence of the PTEN mRNA, was critical for microglial migration. To validate the role of miR-9 in this process, microglial cells were treated with EVs loaded with miR-9, which resulted in significant downregulation of PTEN expression with a concomitant increase in microglial migration. These findings were corroborated by transfecting microglia with a specific target protector of PTEN, that blocked miR-9-mediated downregulation of PTEN as well as microglial migration. In vivo studies wherein the miR-9 precursor-transduced microglia were transplanted into the striatum of mice, followed by assessing their migration in response to a stimulus administered distally, further validated the role of miR-9 in mediating microglial migration. Collectively, our findings provide evidence that glial crosstalk via miRs released from EVs play a vital role in mediating disease pathogenesis and could provide new avenues for development of novel therapeutic strategies aimed at dampening neuropathogenesis.

A novel ligand on astrocytes interacts with natural cytotoxicity receptor NKp44 regulating immune response mediated by NK cells

NK cells play important role in immunity against pathogens and cancer. NK cell functions are regulated by inhibitory and activating receptors binding corresponding ligands on the surface of target cells. NK cells were shown to be recruited to the CNS following several pathological conditions. NK cells could impact CNS physiology by killing glial cells and by secreting IFN-γ. Astrocytes are intimately involved in immunological and inflammatory events occurring in the CNS and reactive astrogliosis is a key feature in HIV-associated neurocognitive disorders. There is little data on NK-astrocyte interactions and ligands expressed on astrocytes that could impact NK cell function. Natural cytotoxicity receptors (NCRs) play a critical role in the cytolytic function of NK cells. Among the NCRs, NKp44 is unique in expression and signal transduction. NKp44 is expressed only upon activation of NK cells and it can mediate both activating and inhibitory signals to NK cells. Here, we have studied the expression and function of natural cytotoxicity receptor NKp44 upon NK-astrocytes interactions in the presence or absence of an HIV peptide (HIV-3S peptide) shown to induce NK cell killing of CD4+ T cells during HIV–infection. Using a fusion protein consisting of the extracellular domain of NKp44 fused to Fc portion of human IgG, we determined the expression of a novel ligand for NKp44 (NKp44L) on astrocytes. Incubation of astrocytes with HIV-3S peptide downregulated NKp44L expression on astrocytes implicating protection from NK mediated killing. Thus, our study showed that NKp44 have a protective effect on astrocytes from NK cell mediated killing during HIV infection and impact astrocyte role in HAND.

In vitro modeling of HIV proviral activity in microglia

Microglia, the resident macrophages of the brain, play a key role in the pathogenesis of HIV-associated neurocognitive disorders (HAND) due to their productive infection by HIV. This results in the release of neurotoxic viral proteins and pro-inflammatory compounds which negatively affect the functionality of surrounding neurons. Because models of HIV infection within the brain are limited, we aimed to create a novel microglia cell line with an integrated HIV provirus capable of recreating several hallmarks of HIV infection. We utilized clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 gene editing technology and integrated a modified HIV provirus into CHME-5 immortalized microglia to create HIV-NanoLuc CHME-5. In the modified provirus, the Gag-Pol region is replaced with the coding region for NanoLuciferase (NanoLuc), which allows for the rapid assay of HIV long terminal repeat activity using a luminescent substrate, while still containing the necessary genetic material to produce established neurotoxic viral proteins (e.g. tat, nef, gp120). We confirmed that HIV-NanoLuc CHME-5 microglia express NanoLuc, along with the HIV viral protein Nef. We subsequently exposed these cells to a battery of experiments to modulate the activity of the provirus. Proviral activity was enhanced by treating the cells with pro-inflammatory factors lipopolysaccharide (LPS) and tumor necrosis factor alpha and by overexpressing the viral regulatory protein Tat. Conversely, genetic modification of the toll-like receptor-4 gene by CRISPR/Cas9 reduced LPS-mediated proviral activation, and pharmacological application of NF-κB inhibitor sulfasalazine similarly diminished proviral activity. Overall, these data suggest that HIV-NanoLuc CHME-5 may be a useful tool in the study of HIV-mediated neuropathology and proviral regulation.

HIV and Cognitive Impairment in Clinical Practice: The Evaluation of a Stepwise Screening Protocol in Relation to Clinical Outcomes and Management

Neurocognitive impairment (NCI) is an increasingly important comorbidity in an ageing HIV+ population. Despite the lack of available treatment modalities, screening for NCI is recommended. In the UMC Utrecht, yearly NCI screening is done using the Montreal Cognitive Assessment (MoCA) tool and the HIV Dementia Scale (HDS). The aim of this study was to evaluate this screening protocol in relation to clinical outcomes and management. A retrospective cohort study was performed in suppressed adult HIV+ patients. Apart from the MoCa and the HDS, the Utrecht Scale for Evaluation of Rehabilitation-Participation (USER-P) and the Hospital Anxiety and Depression Scale (HADS) were performed. Patients scoring below average on cognitive screening tests or with subjective cognitive complaints were further evaluated using a standardized protocol, including optimizing cART and checking for somatic disorders. In patients with cognitive complaints and participation restrictions, cognitive rehabilitation was proposed. Two hundred eighty-six patients were screened. The vast majority were MSM with an average age of 49 years. One hundred forty-four out of 286 patients (50%) had an abnormal test score and/or had subjective cognitive complaints. Restrictions in participation were present in 23% of patients. Six patients on Efavirenz switched their regimes, as this drug is known for its potential central nervous system (CNS) side effects. A depressive component was present in 58 patients (40%). Five patients had a clinical relevant laboratory abnormality. Moreover, six patients were referred for cognitive rehabilitation, which resulted in a 100% success rate in set goals in the five evaluable patients. Although the protocol was not fully adhered to in all patients, it did result in detectable underlying causes of NCI in 59% of patients, and 21% was referred for further treatment. Moreover, cognitive rehabilitation appears to be a very successful intervention for patients with NCI who experience subjective complaints and participation restrictions.

Magnetic Resonance Imaging Evidence for Human Immunodeficiency Virus Effects on Central Auditory Processing: A Review

New research suggests that individuals with human immunodeficiency virus (HIV) have central auditory processing deficits. To review the evidence for HIV affecting parts of the central nervous system involved in central auditory processing, we performed a systematic review of the literature. The objective was to determine whether existing studies show evidence for damage to structures associated with central auditory pathways in HIV. We searched PubMed for papers that used structural magnetic resonance imaging (MRI), diffusion tensor imaging, magnetic resonance spectroscopy or functional MRI in individuals infected with HIV. The review showed that HIV affects several areas involved in central auditory processing particularly the thalamus, internal capsule and temporal cortex. These findings support the idea that HIV can affect central auditory pathways and support the potential use of central auditory tests as a way to assess central nervous system effects of HIV.

HIV-associated executive dysfunction in the era of modern antiretroviral therapy: A systematic review and meta-analysis

OBJECTIVE

While some reports suggest that HIV+ individuals continue to display executive function (EF) impairment in the era of cART, findings have been contradictory and appear to differ based on the aspect of EF being measured. To improve the understanding of how discrete executive abilities may be differentially affected or spared in the context of HIV infection, we conducted a systematic review and meta-analysis to (a) determine whether and to what extent HIV+ adults experience deficits in EFs, and (b) understand how demographic and clinical characteristics may modify the associations between HIV infection and executive abilities.

METHOD

Studies comparing HIV+ and HIV-uninfected groups on measures of working memory, set-shifting, inhibition, decision-making, and apathy between 2000 and 2017 were identified from three databases. Effect sizes (Cohen's d) were calculated using inverse variance weighted random effects models. Meta-regression was used to examine the moderating effect of demographic and clinical variables.

RESULTS

Thirty-seven studies (n = 3935 HIV+; n = 2483 HIV-uninfected) were included in the meta-analysis. Pooled effect sizes for deficits associated with HIV infection were small for domains of set-shifting (d = -0.34, 95% CI [-0.47, -0.20]) and inhibition (d = -0.31, 95% CI [-0.40, -0.21]), somewhat larger for measures of decision-making (d = -0.41, 95% CI [-0.53, -0.28]) and working memory (d = -0.42, 95% CI [-0.59, -0.29]), and largest for apathy (d = -0.87, 95% CI [-1.09, -0.66]). Meta-regression demonstrated that age, sex, education, current CD4 count, and substance dependence differentially moderated the effects of HIV infection on specific EFs. However, lower nadir CD4 count was the only variable associated with greater deficits in nearly all EF domains.

CONCLUSIONS

Our results suggest that discrete domains of EF may be differentially affected by HIV infection and moderating demographic and clinical variables. These findings have implications for the development of targeted cognitive remediation strategies.

Endocytic Trafficking of HIV gp120 is Mediated by Dynamin and Plays a Role in gp120 Neurotoxicity

Neurons that endocytose the human immunodeficiency virus-1 (HIV) protein gp120 exhibit neurite retraction and activation of caspase-3, suggesting that the endocytic process may be crucial for gp120-mediated neuronal injury. The goal of this study is to demonstrate that internalization and accumulation of gp120 play a role in its neurotoxic effects. In mammalian cells, endocytosis is primarily a dynamin-dependent process. To establish whether gp120 is endocytosed in a dynamin-dependent manner, we used fibroblasts in which deletion of dynamins was induced by tamoxifen. We observed a robust reduction of intracellular gp120 immunoreactivity in tamoxifen-treated cells. To examine whether endocytosis of gp120 is crucial for its neurotoxic effect, we blocked gp120 internalization into primary rat cortical neurons by dynasore, an inhibitor of the dynamin GTP-ase activity. We found that dynasore blocks both gp120 internalization and neurotoxicity. We then utilized gp120-loaded mesoporous silica nanoparticles to deliver gp120 intracellularly. We established that once internalized, gp120 is neurotoxic regardless of chemokine receptor activation. Our data suggest that dynamin-dependent endocytosis of gp120 is critical for its neurotoxicity.

HIV-1 Tat Primes and Activates Microglial NLRP3 Inflammasome-Mediated Neuroinflammation

Neuroinflammation associated with HIV-1 infection is a problem affecting ∼50% of HIV-infected individuals. NLR family pyrin domain containing 3 (NLRP3) inflammasome has been implicated in HIV-induced microglial activation, but the mechanism(s) remain unclear. Because HIV-1 Transactivator of Transcription (Tat) protein continues to be present despite antiretroviral therapy and activates NF-kB, we hypothesized that Tat could prime the NLRP3 inflammasome. We found a dose- and time-dependent induction of NLRP3 expression in microglia exposed to Tat compared with control. Tat exposure also time-dependently increased the mature caspase-1 and IL-1β levels and enhanced the IL-1β secretion. These in vitro findings were validated in archival brain tissues from Simian Immunodeficiency Virus (SIV)-infected and uninfected rhesus macaques. Further validation of NLRP3 priming in vivo involved administration of lipopolysaccharide (LPS) to HIV transgenic (Tg) rats followed by assessment of IL-1β mRNA expression and inflammasome activation (ASC oligomers and mature IL-1β). Intriguingly, LPS potentiated upregulation of IL-1β mRNA and inflammasome activation in HIV-Tg rats compared with the wild-type controls. Interestingly, we found an inverse relationship in the expression of NLRP3 and its negative regulator, miR-223, suggesting a miR-223-mediated mechanism for Tat-induced NLRP3 priming. Furthermore, blockade of NLRP3 resulted in decreased IL-1β secretion. Collectively, these findings suggest a novel role of Tat in priming and activating the NLRP3 inflammasome. Therefore, NLRP3 can be envisioned as a therapeutic target for ameliorating Tat-mediated neuroinflammation.SIGNIFICANCE STATEMENT Despite successful suppression of viremia with increased longevity in the era of combined antiretroviral therapy, chronic inflammation with underlying neurocognitive impairment continues to afflict almost 50% of infected individuals. Viral, bacterial, and cellular products have all been implicated in promoting the chronic inflammation found in these individuals. Understanding the molecular mechanism(s) by which viral proteins such as HIV-1 Transactivator of Transcription (Tat) protein can activate microglia is thus of paramount importance. Herein, we demonstrate a novel role of Tat in priming and activating NLR family pyrin domain containing 3 (NLRP3) inflammasomes in microglial cells and in HIV-Tg rats administered lipopolysaccharide. Targeting NLRP3 inflammasome pathway mediators could thus be developed as therapeutic interventions to alleviate or prevent neuroinflammation and subsequent cognitive impairment in HIV-positive patients.

Neuronal Stress and Injury Caused by HIV-1, cART and Drug Abuse: Converging Contributions to HAND

Multiple mechanisms appear to contribute to neuronal stress and injury underlying HIV-associated neurocognitive disorders (HAND), which occur despite the successful introduction of combination antiretroviral therapy (cART). Evidence is accumulating that components of cART can itself be neurotoxic upon long-term exposure. In addition, abuse of psychostimulants, such as methamphetamine (METH), seems to compromise antiretroviral therapy and aggravate HAND. However, the combined effect of virus and recreational and therapeutic drugs on the brain is still incompletely understood. However, several lines of evidence suggest a shared critical role of oxidative stress, compromised neuronal energy homeostasis and autophagy in promotion and prevention of neuronal dysfunction associated with HIV-1 infection, cART and psychostimulant use. In this review, we present a synopsis of recent work related to neuronal stress and injury induced by HIV infection, antiretrovirals (ARVs) and the highly addictive psychostimulant METH.

Neuronal Cell Death and Degeneration through Increased Nitroxidative Stress and Tau Phosphorylation in HIV-1 Transgenic Rats

The underlying mechanisms for increased neurodegeneration and neurocognitive deficits in HIV-infected people are unclear. Therefore, this study was aimed to investigate the mechanisms of increased neurodegeneration in 5-month old male HIV-1 Transgenic (Tg) rats compared to the age- and gender-matched wild-type (WT) by evaluating histological changes and biochemical parameters of the key proteins involved in the cell death signaling and apoptosis. Histological and immunohistochemical analyses revealed decreased neuronal cells with elevated astrogliosis in HIV-1 Tg rats compared to WT. Mechanistic studies revealed that increased levels of nitroxidative stress marker proteins such as NADPH-oxidase, cytochrome P450-2E1 (CYP2E1), inducible nitric oxide synthase (iNOS), the stress-activated mitogen-activated protein kinases such as JNK and p38K, activated cell-cycle dependent CDK5, hypoxia-inducible protein-1α, nitrated proteins, hyperphosphorylated tau, and amyloid plaques in HIV-Tg rats were consistently observed in HIV-1 Tg rats. Confocal microscopy and cell viability analyses showed that treatment with an antioxidant N-acetylcysteine or a specific inhibitor of iNOS 1400W significantly prevented the increased apoptosis of neuro-2A cells by HIV-1 Tat or gp120 protein, demonstrating the causal role of HIV-1 mediated nitroxidative stress and protein nitration in promoting neuronal cell death. Immunoprecipitation and immunoblot analysis confirmed nitration of Hsp90, evaluated as an example of nitrated proteins, suggesting possible involvement of nitrated proteins in neuronal damage. Further, activated p-JNK directly binds tau and phosphorylates multiple amino acids, suggesting an important role of p-JNK in tau hyperphosphorylation and tauopathy. These changes were accompanied with elevated levels of many apoptosis-related proteins Bax and cleaved (activated) caspase-3 as well as proinflammatory cytokines including TNF-α, IL-6 and MCP-1. Collectively, these results indicate that raised nitroxidative stress accompanied by elevated inflammation, cell death signaling pathway including activated p-JNK, C-terminal C99 amyloid fragment formation and tau hyperphosphorylation are responsible for increased apoptosis of neuronal cells and neurodegeneration in 5-month old HIV-Tg rats.

PET brain imaging in HIV-associated neurocognitive disorders (HAND) in the era of combination antiretroviral therapy

Effective combination antiretroviral therapy (cART) has lead to a significant reduction in the prevalence and incidence of central nervous system (CNS) HIV-associated brain disease, particularly CNS opportunistic infections and HIV encephalitis. Despite this, cognitive deficits in people living with HIV, also known as HIV-associated neurocognitive disorders (HAND) have become more prevalent in recent years. The pathogenesis of HAND is likely to be multifactorial, however recent evidence suggests that brain microglial activation is the most likely pathogenic mechanism. Recent developments in positron emission tomography (PET) brain neuroimaging using novel brain radioligands targeting a variety of physiological changes in the brains of HIV-positive individuals have improved our understanding of the mechanisms associated with the development of HAND. This review will highlight recent PET brain neuroimaging studies in the cART era, focusing on physiological and neurochemical changes associated with HAND in people living with HIV.

Nanoformulated Antiretrovirals for Penetration of the Central Nervous System: State of the Art

The central nervous system is a very challenging HIV-1 sanctuary. But, despite complete suppression of plasmatic viral replication with current antiretroviral therapy, signs of HIV-1 replication can still be found in the cerebrospinal fluid in some patients. The main limitation to achieving HIV-1 eradication from the brain is related to the suboptimal concentrations of antiretrovirals within this site, due to their low permeation across the blood-brain barrier. In recent years, a number of reliable nanotechnological strategies have been developed with the aim of enhancing antiretroviral drug penetration across the blood-brain barrier. The aim of this review is to provide an overview of the different nanoformulated antiretrovirals, used in both clinical and preclinical studies, that are designed to improve their delivery into the brain by active or passive permeation mechanisms through the barrier. Different nanotechnological approaches have proven successful for optimizing antiretrovirals delivery to the central nervous system, with a likely benefit for HIV-associated neurocognitive disorders and a more debated contribution to the complete eradication of the HIV-1 infection.

Aging, neurocognitive impairment and adherence to antiretroviral therapy in human immunodeficiency virus-infected individuals

Background/objective

There is an increasing number of older patients with human immunodeficiency virus infection due to the success of antiretroviral therapy, the improved prognosis and life expectancy of patients, and the higher number of new infections among older individuals. The main objective of the present study was to compare the characteristics of older human immunodeficiency virus patients with those of younger patients.

Materials and methods

We conducted a cross-sectional study with human immunodeficiency virus-infected patients who were treated at the Specialized Care Service (Serviço de Assistência Especializada) for human immunodeficiency virus/AIDS in the city of Pelotas, South Brazil. Sociodemographic information as well as data on human immunodeficiency virus infection and treatment were collected. All participants underwent psychiatric and neurocognitive assessments, and their adherence to antiretroviral therapy was evaluated.

Results

A total of 392 patients participated in the study, with 114 patients aged 50 years and older. The characteristics showing significant differences between older and younger human immunodeficiency virus-infected patients included race/ethnicity, comorbidities, duration and adherence to antiretroviral therapy, currently undetectable viral load, and cognitive impairment. Compared to younger patients, older patients were at higher risk of exhibiting cognitive impairment [OR 2.28 (95% CI: 1.35–3.82, p = 0.002)] and of having increased adherence to antiretroviral therapy [OR 3.11 (95% CI: 1.67–5.79, p < 0.001)].

Conclusions

The prevalence of neurocognitive impairment remained high in human immunodeficiency virus-infected patients despite antiretroviral therapy. In the present study, the prevalence of this type of impairment was significantly higher in patients aged ≥50 years, most likely due to aging, human immunodeficiency virus infection, and a possible synergistic effect between these factors. Despite this higher prevalence, older patients exhibited higher rates of adherence to antiretroviral therapy and of undetectable human immunodeficiency virus viral load.

Depression and diagnosis of neurocognitive impairment in HIV-positive patients

Neurocognitive impairment (NCI) is frequently observed in patients infected with human immunodeficiency virus (HIV) and results from the compromise of subcortical brain structures by the virus. The manifestations of NCI range from asymptomatic impairment to dementia. In addition to cognitive impairment resulting from HIV infection, other factors such as depression are associated with the loss of cognitive functions. The aim of this study was to estimate the prevalence of NCI in HIV-positive patients in a city in southern Brazil and to establish possible associations for the prevalence of NCI with HIV-related and other risk factors. This cross-sectional study of HIV-positive outpatients was conducted in a specialized care service in the city of Pelotas in Southern Brazil. Sociodemographic data and HIV-related information were collected, and all patients underwent psychiatric and neurocognitive evaluations. The prevalence of NCI among the 392 patients was 54.1% when tracked using the IHDS (International HIV Dementia Scale) and 36.2% when the IHDS was associated with a battery of complementary tests. A bivariate analysis suggested an association of NCI with gender, age, educational level, depression, current CD4 count and lowest CD4 count. The association of NCI with depression remained in the Poisson regression (PR=1.96, 95%CI=1.12-3.42). The prevalence of cognitive impairment in HIV-positive patients estimated in this study is in accordance with international and Brazilian data. Of the factors analyzed, depression showed the greatest evidence of association with neurocognitive loss. Based on our findings, the inclusion of instruments to evaluate depression in our services for patients with HIV and acquired immunodeficiency syndrome (AIDS) is recommended.

Getting into the brain: Potential of nanotechnology in the management of NeuroAIDS

In spite of significant advances in antiretroviral (ARV) therapy, the elimination of human immunodeficiency virus (HIV) reservoirs from the periphery and the central nervous system (CNS) remains a formidable task. The incapability of ARV to go across the blood-brain barrier (BBB) after systemic administration makes the brain one of the dominant HIV reservoirs. Thus, screening, monitoring, and elimination of HIV reservoirs from the brain remain a clinically daunting and key task. The practice and investigation of nanomedicine possesses potentials for therapeutics against neuroAIDS. This review highlights the advancements in nanoscience and nanotechnology to design and develop specific size therapeutic cargo for efficient navigation across BBB so as to recognize and eradicate HIV brain reservoirs. Different navigation and drug release strategies, their biocompatibility and efficacy with related challenges and future prospects are also discussed. This review would be an excellent platform to understand nano-enable multidisciplinary research to formulate efficient nanomedicine for the management of neuroAIDS.

Proceedings from the NIMH symposium on "NeuroAIDS in Africa: neurological and neuropsychiatric complications of HIV"

Despite major advances in HIV-1 treatment, the prevalence of HIV-associated neurocognitive disorders (HAND) remains a problem, particularly as individuals on suppressive treatment continue to live longer. To facilitate discussion on emerging and future directions in HAND research, a meeting was held in Durban, South Africa in March 2015 as part of the Society of Neuroscientists of Africa (SONA) conference. The objective of the meeting was to assess the impact of HIV subtype diversity on HAND and immunological dysfunction. The meeting brought together international leaders in the area of neurological complications of HIV-1 infection with special focus on the African population. Research presentations indicated that HAND was highly prevalent and that inflammatory cytokines and immune-activation played important roles in progression of neurocognitive impairment. Furthermore, children on antiretroviral therapy were also at risk for developing neurocognitive impairment. With respect to the effect of HIV-1 subtype diversity, analyses of HIV-1 clade C infection among South Africans revealed that clade C infection induced cognitive impairment that was independent of the substitution in HIV-1 Trans-Activator of Transcription (Tat; C31S). At the cellular level, a Zambian study showed that clade C infection resulted in reduced brain cell death compared with clade B infection suggesting clade specific variations in mediating brain cell injury. Furthermore, ex vivo Tat protein from clade CRF02_AG, prevalent in West/ Central Africa, exhibited reduced disruption of brain endothelium compared with clade B Tat protein. Discussions shed light on future research directions aimed at understanding biomarkers and disease mechanisms critical for HAND.

Cerebrospinal Fluid Biomarkers of Simian Immunodeficiency Virus Encephalitis : CSF Biomarkers of SIV Encephalitis

Antiretroviral therapy has led to increased survival of HIV-infected patients but also increased prevalence of HIV-associated neurocognitive disorders. We previously identified YKL40 as a potential cerebrospinal fluid (CSF) biomarker of lentiviral central nervous system (CNS) disease in HIV-infected patients and in the macaque model of HIV encephalitis. The aim of this study was to define the specificity and sensitivity along with the predictive value of YKL40 as a biomarker of encephalitis and to assess its relationship to CSF viral load. CSF YKL40 and SIV RNA concentrations were analyzed over the course of infection in 19 SIV-infected pigtailed macaques and statistical analyses were performed to evaluate the relationship to encephalitis. Using these relationships, CSF alterations of 31 neuroimmune markers were studied pre-infection, during acute and asymptomatic infection, at the onset of encephalitis, and at necropsy. YKL40 CSF concentrations above 1122 ng/ml were found to be a specific and sensitive biomarker for the presence of encephalitis and were highly correlated with CSF viral load. Macaques that developed encephalitis had evidence of chronic CNS immune activation during early, asymptomatic, and end stages of infection. At the onset of encephalitis, CSF demonstrated a rise of neuroimmune markers associated with macrophage recruitment, activation and interferon response. CSF YKL40 concentration and viral load are valuable biomarkers to define the onset of encephalitis. Chronic CNS immune activation precedes the development of encephalitis while some responses suggest protection from CNS lentiviral disease.

SIV Infection Impairs the Central Nervous System in Chinese Rhesus Macaques

The central nervous system (CNS) impairment is a consequence seen in SIV infection of rhesus macaques of Indian-origin, which is more common in infected macaques with rapid disease progression than in those with conventional disease progression. Here, we investigated the CNS damages in SIVmac239-infected Chinese rhesus macaques. We demonstrated that SIV infection of Chinese macaques could cause neuropathological impairments, which was evidenced by appearance of SIV-RNA positive cells, the infiltration of activated macrophages and abundant multinucleated giant cells (MNGCs) in the different regions of the brains. The animals with high viremia and short survival time (average of 16 weeks, rapid progression, RP) had severer neuropathological changes than those with conventional progression (CP). As compared with the RP animals, CP macaques had lower viremia and much longer survival time (average of 154 weeks). These findings indicate that SIVmac239 infection of Chinese rhesus macaque can be used as a suitable animal model and alternative resource for nueroAIDS research.

Modulation Effect of HIV-1 Viral Proteins and Nicotine on Expression of the Immune-Related Genes in Brain of the HIV-1 Transgenic Rats

The human immunodeficiency virus-1 transgenic (HIV-1Tg) rat is a non-infectious rodent model for HIV-1 infection which develops altered immune-responses similar to those in persons infected with HIV-1. HIV-1Tg and F344 rats respond significantly different to morphine, ethanol, nicotine and other psychostimulants, although the molecular mechanisms underlying these differences remain largely undetermined. Here, we compared expression of 52 immune-related genes in the prefrontal cortex (PFC), nucleus accumbens (NAc), and ventral tegmental area (VTA) of HIV-1Tg and F344 rats treated with either nicotine (0.4 mg/kg nicotine, base, s.c.) or saline for 27 days, to identify differentially expressed genes in the presence of HIV-1 with and without nicotine treatment. Using quantitative RT-PCR array, we measured RNA expression levels. Results showed that RNA expression of CASP3, CCL5, CX3CL1, CX3CR1, IL1α, LRF4, LFR7, TGFβ1 and TLR4 in NAc, CCL2, CCL5, TGFβ1 and TLR4 in PFC, and CASP3, CX3CR1, IFNα1, IL1β and IL6 in VTA was significantly modulated in HIV-1Tg rats compared with F344 rats. IL1α showed a 58 % (P = 0.000072) decrease and IRF6 showed a 93.7 % increase (P = 0.000227) in the NAc of HIV-1Tg compared with F344 rats; results remained significant after correction for multiple testing. We also found that several genes were significantly modulated by nicotine in HIV-1Tg rats while only a small number of immune-related genes were altered by nicotine in F344 rats. These findings imply that HIV-1 viral proteins greatly impact immune function and alter responsiveness to nicotine in certain immune-related genes.

Characterization of neuropathology in the HIV-1 transgenic rat at different ages

The transgenic HIV-1 rat (Tg) is a commonly used neuroHIV model with documented neurologic/behavioral deficits. Using immunofluorescent staining of the Tg brain, we found astrocytic dysfunction/damage, as well as dopaminergic neuronal loss/dysfunction, both of which worsening significantly in the striatum with age. We saw mild microglial activation in young Tg brains, but this decreased with age. There were no differences in neurogenesis potential suggesting a neurodegenerative rather than a neurodevelopmental process. Gp120 CSF levels exceeded serum gp120 levels in some animals, suggesting local viral protein production in the brain. Further probing of the pathophysiology underlying astrocytic injury in this model is warranted.

Natural Products as Anti-HIV Agents and Role in HIV-Associated Neurocognitive Disorders (HAND): A Brief Overview

As the threat of Human Immunodeficiency Virus (HIV)/Acquired Immunodeficiency Syndrome (AIDS) persists to rise, effective drug treatments are required to treat the infected people. Even though combination antiretroviral therapy (cART) provides stable viral suppression, it is not devoid of undesirable side effects, especially in persons undergoing long-term treatment. The present therapy finds its limitations in the emergence of multidrug resistance and accordingly finding new drugs and novel targets is the need of the hour to treat the infected persons and further to attack HIV reservoirs in the body like brain, lymph nodes to achieve the ultimate goal of complete eradication of HIV and AIDS. Natural products such as plant-originated compounds and plant extracts have enormous potential to become drug leads with anti-HIV and neuroprotective activity. Accordingly, many research groups are exploring the biodiversity of the plant kingdom to find new and better anti-HIV drugs with novel mechanisms of action and for HIV-associated neurocognitive disorders (HAND). The basic challenge that still persists is to develop viral replication-targeted therapy using novel anti-HIV compounds with new mode of action, accepted toxicity and less resistance profile. Against this backdrop, the World Health Organization (WHO) suggested the need to evaluate ethno-medicines for the management of HIV/AIDS. Consequently, there is need to evaluate traditional medicine, particularly medicinal plants and other natural products that may yield effective and affordable therapeutic agents. Although there are a good number of reports on traditional uses of plants to treat various diseases, knowledge of herbal remedies used to manage HIV/AIDS and HAND are scanty, vague and not well documented. In this review, plant substances showing a promising action that is anti-HIV and HAND will be explored along with what they interact. Since some plant substances are also known to modulate several cellular factors which are also involved in the replication of HIV and hence their role as potential candidates will be discussed. HIV/AIDS being an exceptional epidemic, demands an exceptional approach and that forms very much focus for the current review.

Glutaminase-containing microvesicles from HIV-1-infected macrophages and immune-activated microglia induce neurotoxicity

BACKGROUND

HIV-1-infected and/or immune-activated microglia and macrophages are pivotal in the pathogenesis of HIV-1-associated neurocognitive disorders (HAND). Glutaminase, a metabolic enzyme that facilitates glutamate generation, is upregulated and may play a pathogenic role in HAND. Our previous studies have demonstrated that glutaminase is released to the extracellular fluid during HIV-1 infection and neuroinflammation. However, key molecular mechanisms that regulate glutaminase release remain unknown. Recent advances in understanding intercellular trafficking have identified microvesicles (MVs) as a novel means of shedding cellular contents. We posit that during HIV-1 infection and immune activation, microvesicles may mediate glutaminase release, generating excessive and neurotoxic levels of glutamate.

RESULTS

MVs isolated through differential centrifugation from cell-free supernatants of monocyte-derived macrophages (MDM) and BV2 microglia cell lines were first confirmed in electron microscopy and immunoblotting. As expected, we found elevated number of MVs, glutaminase immunoreactivities, as well as glutaminase enzyme activity in the supernatants of HIV-1 infected MDM and lipopolysaccharide (LPS)-activated microglia when compared with controls. The elevated glutaminase was blocked by GW4869, a neutral sphingomyelinase inhibitor known to inhibit MVs release, suggesting a critical role of MVs in mediating glutaminase release. More importantly, MVs from HIV-1-infected MDM and LPS-activated microglia induced significant neuronal injury in rat cortical neuron cultures. The MV neurotoxicity was blocked by a glutaminase inhibitor or GW4869, suggesting that the neurotoxic potential of HIV-1-infected MDM and LPS-activated microglia is dependent on the glutaminase-containing MVs.

CONCLUSIONS

These findings support MVs as a potential pathway/mechanism of excessive glutamate generation and neurotoxicity in HAND and therefore MVs may serve as a novel therapeutic target.

Antiretrovirals, Methamphetamine, and HIV-1 Envelope Protein gp120 Compromise Neuronal Energy Homeostasis in Association with Various Degrees of Synaptic and Neuritic Damage

HIV-1 infection frequently causes HIV-associated neurocognitive disorders (HAND) despite combination antiretroviral therapy (cART). Evidence is accumulating that components of cART can themselves be neurotoxic upon long-term exposure. In addition, abuse of psychostimulants, such as methamphetamine, seems to aggravate HAND and compromise antiretroviral therapy. However, the combined effect of virus and recreational and therapeutic drugs on the brain is poorly understood. Therefore, we exposed mixed neuronal-glial cerebrocortical cells to antiretrovirals (ARVs) (zidovudine [AZT], nevirapine [NVP], saquinavir [SQV], and 118-D-24) of four different pharmacological categories and to methamphetamine and, in some experiments, the HIV-1 gp120 protein for 24 h and 7 days. Subsequently, we assessed neuronal injury by fluorescence microscopy, using specific markers for neuronal dendrites and presynaptic terminals. We also analyzed the disturbance of neuronal ATP levels and assessed the involvement of autophagy by using immunofluorescence and Western blotting. ARVs caused alterations of neurites and presynaptic terminals primarily during the 7-day incubation and depending on the specific compounds and their combinations with and without methamphetamine. Similarly, the loss of neuronal ATP was context specific for each of the drugs or combinations thereof, with and without methamphetamine or viral gp120. Loss of ATP was associated with activation of AMP-activated protein kinase (AMPK) and autophagy, which, however, failed to restore normal levels of neuronal ATP. In contrast, boosting autophagy with rapamycin prevented the long-term drop of ATP during exposure to cART in combination with methamphetamine or gp120. Our findings indicate that the overall positive effect of cART on HIV infection is accompanied by detectable neurotoxicity, which in turn may be aggravated by methamphetamine.

Target of HIV-1 Envelope Glycoprotein gp120-Induced Hippocampal Neuron Damage: Role of Voltage-Gated K(+) Channel Kv2.1

Human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein 120 (gp120) has been reported to be toxic to the hippocampal neurons, and to be involved in the pathogenesis of HIV-1-associated neurocognitive disorders (HAND). Accumulating evidence has demonstrated that voltage-gated potassium (Kv) channels, especially the outward delayed-rectifier K(+) (Ik) channels, play a critical role in gp120-induced cortical neuronal death in vitro. However, the potential mechanisms underlying the hippocampal neuronal injury resulted from gp120-mediated neurotoxicity remain poorly understood. Using whole-cell patch clamp recording in cultured hippocampal neurons, this study found that gp120 significantly increased the outward delayed-rectifier K(+) currents (Ik). Meanwhile, Western blot assay revealed that gp120 markedly upregulated Kv2.1 protein levels, which was consistent with the increased Ik density. With Western blot and terminal deoxynucleotidyl transferase dUTP nick end labeling assays, it was discovered that gp120-induced neuronal injury was largely due to activation of Kv2.1 channels and resultant apoptosis mediated by caspase-3 activation, as the pharmacological blockade of Kv2.1 channels largely attenuated gp120-induced cell damage and caspase-3 expression. Moreover, p38 MAPK was demonstrated to participate in gp120-induced hippocampal neural damage, since p38 MAPK antagonist (SB203580) partially abrogated gp120-induced Kv2.1 upregulation and neural apoptosis. Taken together, these results suggest that gp120 induces hippocampal neuron apoptosis by enhancement of the Ik, which might be associated with increased Kv2.1 expression via the p38 MAPK pathway.