A review of the potential mechanisms of neuronal toxicity associated with antiretroviral drugs

Switching to Low Neurotoxic Antiretrovirals to Improve Neurocognition Among People Living With HIV-1-Associated Neurocognitive Disorder: The MARAND-X Randomized Clinical Trial

BACKGROUND

The pathogenesis of HIV-associated neurocognitive (NC) impairment is multifactorial, and antiretroviral (ARV) neurotoxicity may contribute. However, interventional pharmacological studies are limited.

METHODS

Single-blind, randomized (1:1), controlled trial to assess the change of NC performance (Global Deficit Score, GDS, and domain scores) in PLWH with NC impairment randomized to continue their standard of care treatment or to switch to a less neurotoxic ARV regimen: darunavir/cobicistat, maraviroc, emtricitabine (MARAND-X). Participants had plasma and cerebrospinal fluid HIV RNA< 50 copies/mL, R5-tropic HIV, and were on ARV regimens that did not include efavirenz and darunavir. The change of resting-state electroencephalography was also evaluated. The outcomes were assessed at week 24 of the intervention through tests for longitudinal paired data and mixed-effect models.

RESULTS

Thirty-eight participants were enrolled and 28 completed the follow-up. Global Deficit Score improved over time but with no difference between arms in longitudinal adjusted models. Perceptual functions improved in the MARAND-X, while long-term memory improved only in participants within the MARAND-X for whom the central nervous system penetration-effectiveness (CNS penetration effectiveness) score increased by ≥3. No significant changes in resting-state electroencephalography were observed.

CONCLUSIONS

In this small but well-controlled study, the use of less neurotoxic ARV showed no major beneficial effect over an unchanged regimen. The beneficial effects on the memory domain of increasing CNS penetration effectiveness score suggest that ARV neuropenetration may have a role in cognitive function.

Perinatal exposure to atazanavir-based antiretroviral regimens in a mouse model leads to differential long-term motor and cognitive deficits dependent on the NRTI backbone

Background

Combination antiretroviral therapy (ART) use in pregnancy has been pivotal in improving maternal health and reducing perinatal HIV transmission. However, children born HIV-exposed uninfected fall behind their unexposed peers in several areas including neurodevelopment. The contribution of in utero ART exposure to these deficits is not clear. Here we present our findings of neurocognitive outcomes in adult mice exposed in utero to ART.

Methods

Dams were treated with a combination of ritonavir-boosted atazanavir with either abacavir plus lamivudine (ABC/3TC + ATV/r) or tenofovir disoproxil fumarate plus emtricitabine (TDF/FTC + ATV/r), or water as a control, administered daily from day of plug detection to birth. Offspring underwent a battery of behavioral tests that investigated motor performance and cognition starting at 6-weeks of age and ending at 8 months. Changes in brain structure were assessed using magnetic resonance imaging and immunohistochemistry. Expression of genes involved in neural circuitry and synaptic transmission were assessed in the hippocampus, a region strongly associated with memory formation, using qPCR.

Findings

Pups exposed to TDF/FTC + ATV/r showed increased motor activity and exploratory drive, and deficits in hippocampal-dependent working memory and social interaction, while pups exposed to ABC/3TC + ATV/r showed increased grooming, and deficits in working memory and social interaction. Significant volumetric reductions in the brain were seen only in the ABC/3TC + ATV/r group and were associated with reduced neuronal counts in the hippocampus. Altered neurotransmitter receptor mRNA expression as well as changes in expression of the neurotrophic factor BDNF and its receptors were observed in both ART-exposed groups in a sex-dependent manner.

Interpretation

In our model, in utero ART exposure had long-term effects on brain development and cognitive and motor outcomes in adulthood. Our data show that neurological outcomes can be influenced by the type of nucleoside reverse transcriptase inhibitor backbone of the regimen and not just the base drug, and display sex differences.

Human iPSC-derived neurons reveal NMDAR-independent dysfunction following HIV-associated insults

The central nervous system encounters a number of challenges following HIV infection, leading to increased risk for a collection of neurocognitive symptoms clinically classified as HIV-associated neurocognitive disorders (HAND). Studies attempting to identify causal mechanisms and potential therapeutic interventions have historically relied on primary rodent neurons, but a number of recent reports take advantage of iPSC-derived neurons in order to study these mechanisms in a readily reproducible, human model. We found that iPSC-derived neurons differentiated via an inducible neurogenin-2 transcription factor were resistant to gross toxicity from a number of HIV-associated insults previously reported to be toxic in rodent models, including HIV-infected myeloid cell supernatants and the integrase inhibitor antiretroviral drug, elvitegravir. Further examination of these cultures revealed robust resistance to NMDA receptor-mediated toxicity. We then performed a comparative analysis of iPSC neurons exposed to integrase inhibitors and activated microglial supernatants to study sub-cytotoxic alterations in micro electrode array (MEA)-measured neuronal activity and gene expression, identifying extracellular matrix interaction/morphogenesis as the most consistently altered pathways across HIV-associated insults. These findings illustrate that HIV-associated insults dysregulate human neuronal activity and organization even in the absence of gross NMDA-mediated neurotoxicity, which has important implications on the effects of these insults in neurodevelopment and on the interpretation of primary vs. iPSC in vitro neuronal studies.

Is the Central Nervous System Reservoir a Hurdle for an HIV Cure?

There is currently no cure for HIV infection although adherence to effective antiretroviral therapy (ART) suppresses replication of the virus in blood, increases CD4+ T-cell counts, reverses immunodeficiency, and increases life expectancy. Despite these substantial advances, ART is a lifelong treatment for people with HIV (PWH) and upon cessation or interruption, the virus quickly rebounds in plasma and anatomic sites, including the central nervous system (CNS), resulting in disease progression. With recent advances in quantifying viral burden, detection of genetically intact viral genomes, and isolation of replication-competent virus from brain tissues of PWH receiving ART, it has become apparent that the CNS viral reservoir (largely comprised of macrophage type cells) poses a substantial challenge for HIV cure strategies. Other obstacles impacting the curing of HIV include ageing populations, substance use, comorbidities, limited antiretroviral drug efficacy in CNS cells, and ART-associated neurotoxicity. Herein, we review recent findings, including studies of the proviral integration sites, reservoir decay rates, and new treatment/prevention strategies in the context of the CNS, together with highlighting the next steps for investigations of the CNS as a viral reservoir.

Changes in Cerebrospinal Fluid, Liver and Intima-media-thickness Biomarkers in Patients with HIV-associated Neurocognitive Disorders Randomized to a Less Neurotoxic Treatment Regimen

The prevalence of neurocognitive impairment in people living with HIV is estimated between 30 and 50%. The pathogenesis of HIV-associated neurocognitive disorders is complex and multifactorial. Aim of the study was to measure the change in CSF biomarkers, Fibroscan and IMT measurements in PLWH with HAND randomized to a less neurotoxic regimen, or continuing their treatment. Adult patients with HAND were screened and enrolled if presenting no major resistance associated mutations, no HIV viral replication, not on efavirenz or darunavir, with R5-tropic HIV and without major confounding conditions. Lumbar puncture, IMT and Fibroscan measurements were performed. After 1:1 randomization to a less neurotoxic regimen consisting of darunavir/cobicistat plus emtricitabine plus maraviroc, or mantaining actual care, tests were repeated after 24 weeks: CSF biomarkes (HIV RNA, tau, p-tau, Beta-amyloid1-42, S100Beta and neopterin) were included. Non-parametric tests (Mann-Whitney and Wilcoxon's) were used. 28 participants completed the study. Male and European ancestry were prevalent; median age was 55 years (51-60). All patients were virally suppressed; median CD4 + count was 626 cell/uL (469-772). Baseline characteristics were similar between the study arms. A significant decrease in CSF p-tau and an increase in CSF neopterin and NFL were observed. We observed a significant reduction in liver stiffness at W24. Despite a small sample size we observed changes in neuromarkers and in hepatic stiffness in patients randomized to the experimental arm. We observed changes in CSF biomarkers (lower phosphorylated-tau and higher neopterin and NFL) that need to be replicated in large cohorts. Subclinical neurotoxicity may be observed in patients with HAND and warrants prospective studies.

Delirium among people aging with and without HIV: Role of alcohol and Neurocognitively active medications

BACKGROUND

People aging with and without HIV (PWH and PWoH) want to avoid neurocognitive dysfunction, especially delirium. Continued use of alcohol in conjunction with neurocognitively active medications (NCAMs) may be a largely underappreciated cause, especially for PWH who experience polypharmacy a decade earlier than PWoH. We compare absolute and relative risk of delirium among PWH and PWoH by age, level of alcohol use, and exposure to NCAMs.

METHODS

Using the VACS cohort, we compare absolute and relative risk of inpatient delirium among PWH and PWoH by age, level of alcohol use, and exposure to NCAMs between 2007 and 2019. We matched each case based on age, race/ethnicity, sex, HIV, baseline year, and observation time with up to 5 controls. The case/control date was defined as date of admission for cases and the date corresponding to the same length of time on study for controls. Level of alcohol use was defined using Alcohol Use Disorder Identification Test-Consumption (AUDIT-C). Medication exposure was measured from 45 to 3 days prior to index date; medications were classified as anticholinergic NCAM, non-anticholinergic NCAM, or non NCAM and counts generated. We used logistic regression to determine odds ratios (ORs) for delirium associated with medication counts stratified by HIV status and adjusted for demographics, severity of illness, and related diagnoses.

RESULTS

PWH experienced a higher incidence of delirium (5.6, [95% CI 5.3-5.9/1000 PY]) than PWoH (5.0, [95% CI 4.8-5.1/1000 PY]). In multivariable analysis, anticholinergic and non-anticholinergic NCAM counts and level of alcohol use demonstrated strong independent dose-response associations with delirium.

CONCLUSIONS

Decreasing alcohol use and limiting the use of neurocognitively active medications may help decrease excess rates of delirium, especially among PWH.

Longitudinal decline of plasma neurofilament light levels after antiretroviral initiation in people living with HIV

BACKGROUND

This retrospective follow-up study aims to investigate the dynamic longitudinal change of plasma neurofilament light (NfL) levels after antiretroviral therapy (ART) initiation in a cohort of people living with human immunodeficiency virus (HIV) (PWH).

METHODS

We tested a convenience sample of 116 patients from the NORTHIV study. Plasma NfL levels-measured using Single molecule array (Simoa) technology-as well as other laboratory parameters were collected at baseline, weeks 4, 48, 96, and 144. Linear mixed-effects models were estimated to evaluate longitudinal change over time. Baseline CD4⁺ T-cell levels, CDC classification, and HIV RNA levels were considered. Models were adjusted by age, sex, treatment regimen, and baseline serum creatinine levels.

RESULTS

Plasma NfL levels were higher at baseline and also declined faster during the follow-up for participants with CD4⁺ count <100 cells/µl compared with >100 cells/µl. No significant difference was found between the CD4⁺ strata 100-199 and 200-499/µl. Participants with CDC classification stages B and C had higher levels of plasma NfL at baseline, as well as faster decline compared with participants with stage A. No significant main effects or change over time was found in baseline HIV RNA levels, treatment regimen, or sex.

CONCLUSION

Plasma NfL is a sensitive biomarker to assess ongoing central nervous system injury in PWH. Plasma NfL concentrations decline relatively fast following ART initiation and then stabilize after 48 weeks. Plasma NfL concentrations are associated with CD4⁺ count and stage of HIV disease. No correlations were seen with different ART regimens.

An Efficient Humanized Mouse Model for Oral Anti-Retroviral Administration

HIV anti-retrovirals (ARVs) have vastly improved the life expectancy of people living with HIV (PLWH). However, toxic effects attributed to long-term ARV use also contribute to HIV-related co-morbidities such as heart disease, bone loss and HIV-associated neurocognitive disorders (HAND). Unfortunately, mouse models used to study the effects of ARVs on viral suppression, toxicity and HIV latency/tissue reservoirs have not been widely established. Here, we demonstrate an effective mouse model utilizing immune-compromised mice, reconstituted with infected human peripheral blood mononuclear cell (PBMCs). ARVs areincorporated into mouse chow and administered daily with combination ARV regimens includingAtripla (efavirenz, tenofovir disoproxil fumarate, and emtricitabine) and Triumeq (abacavir, dolutegravir and lamivudine). This model measures HIV-infected human cell trafficking, and ARV penetration throughout most relevant HIV organs and plasma, with a large amount of trafficking to the secondary lymphoid organs. Furthermore, the HIV viral load within each organ and the plasma was reduced in ARV treated vs. untreated control. Overall, we have demonstrated a mouse model that is relatively easy and affordable to establish and utilize to study ARVs' effect on various tissues, including the co-morbid conditions associated with PLWH, such as HAND, and other toxic effects.

Causes of HIV Treatment Interruption during the Last 20 Years: A Multi-Cohort Real-Life Study

In the last years, many antiretroviral drugs (ART) have been developed with increased efficacy. Nowadays, the main reasons for treatment switches are adverse events, proactive strategy or simplification. We conducted a retrospective cohort study to investigate the reason for treatment interruption in the last 20 years. We merged data of eight cohorts of the SCOLTA project: lopinavir/r (LPV), atazanavir/r (ATV), darunavir/r or /c (DRV), rilpivirine (RPV), raltegravir (RAL), elvitegravir/c (EVG), dolutegravir (DTG) and bictegravir (BIC). We included 4405 people with HIV (PWH). Overall, 664 (15.1%), 489 (11.1%), and 271 (6.2%) PWH interrupted the treatment in the first, second, and third years after starting a new ART. Looking at the interruption in the first year, the most frequent causes were adverse events (3.8%), loss to follow-up (3.7%), patients’ decisions (2.6%), treatment failure (1.7%), and simplification (1.3%). In the multivariate analysis regarding experienced patients, treatment with LPV, ATV, RPV or EVG/c, having less than 250 CD4 cells/mL, history of intravenous drug use, and HCV positivity were associated with an increased risk of interruption. In naive people, only LPV/r was associated with an increased risk of interruption, while RPV was associated with a lower risk. In conclusion, our data on more than 4400 PWH show that adverse events have represented the most frequent cause of treatment interruptions in the first year of ART (3.84%). Treatment discontinuations were more frequent during the first year of follow-up and decreased thereafter. First-generation PI in both naïve and experienced PWH, and EVG/c, in experienced PWH, were associated with a higher risk of treatment interruptions.

Antiretroviral Levels in the Cerebrospinal Fluid: The Effect of Inflammation and Genetic Variants

Neurocognitive impairments are common in people living with HIV. Some conditions, such as chronic inflammation, astrocyte infection and an impaired blood-brain barrier (BBBi), along with host genetic variants in transporter genes, may affect antiretroviral (ARV) exposure in the cerebrospinal fluid (CSF). The aim of this study was to evaluate ARV CSF penetration according to compartmental inflammation, BBB permeability and single-nucleotide polymorphisms (SNPs) in drug transporter encoding genes. CSF neopterin (ELISA), plasma and CSF ARV concentrations (HPLC) and host genetic variants in ABCC2, HNF4α, SLCO1A2 and SLC22A6 (real-time PCR) were measured. Bi- and multivariate analyses were performed for single ARV and classes. We included 259 participants providing 405 paired plasma and CSF samples. CSF/plasma ratios (CPR) showed an increase for NRTIs and nevirapine with low penetrations for the majority of ARVs. At bi-variate analysis, several associations, including the effect of BBBi (emtricitabine, raltegravir), age (zidovudine and darunavir), and high CSF neopterin (NRTIs and border-line for PIs) were suggested. An association was found between genetic variants and integrase strand transfer (ABCC2 and HNF4α), non-nucleoside reverse transcriptase inhibitors (SLCO1A2), and protease inhibitors (SLC22A6). At multivariate analysis age, gender, BMI, and altered BBB were independent predictors of nucleoside reverse transcriptase CSF concentrations; age (for protease inhibitors) and body mass index and altered BBB (integrase strand transfer inhibitors) were also associated with ARV CSF exposure. We describe factors associated with CSF concentrations, showing that demographic, BBB integrity and, partially, genetic factors may be predictors of drug passage in the central nervous system.

Current Challenges and Solutions for Clinical Management and Care of People with HIV: Findings from the 12th Annual International HIV and Aging Workshop

People with HIV on combination antiretroviral therapy (ART) have longer life expectancy and are increasingly experiencing age-related comorbidities. Thus, aging with HIV has become a central issue in clinical care and research, which has been particularly challenging with the intersection of the ongoing coronavirus (COVID)-19 pandemic. Since 2009, the International Workshop on HIV and Aging has served as a multidisciplinary platform to share research findings from cross-disciplinary fields along with community advocates to address critical issues in HIV and aging. In this article, we summarize the key oral presentations from the 12th Annual International Workshop on HIV and Aging, held virtually on September 23rd and 24th, 2021. The topics ranged from basic science research on biological mechanisms of aging to quality of life and delivery of care under the COVID-19 pandemic. This workshop enriched our understanding of HIV and aging under the COVID-19 pandemic, identified challenges and opportunities to combat the impact of COVID-19 on HIV communities, and also provided updated research and future directions of the field to move HIV and aging research forward, with the ultimate goal of successful aging for older people with HIV.

Anticholinergic and sedative medications are associated with neurocognitive performance of well-treated people living with HIV

Background

We previously showed that anticholinergic (ACH) medications contribute to self-reported neurocognitive impairment (NCI) in elderly people with human immunodeficiency virus (PWH). The current cross-sectional study further evaluated the effect of ACH and sedative drugs on neurocognitive function in PWH who underwent comprehensive neuropsychological evaluation.

Methods

A medication review was performed in PWH enrolled in the prospective Neurocognitive Assessment in Metabolic and Aging Cohort within the Swiss HIV Cohort Study. Neurocognitive functions were analyzed in 5 domains (motor skills, speed of information, attention/working memory, executive functions, and verbal learning memory). The effect of ACH and sedative medications on neurocognitive functioning was evaluated using linear regression models for the continuous (mean z-score) outcome and multivariable logistic regression models for the binary (presence/absence) outcome.

Results

A total of 963 PWH (80% male, 92% Caucasian, 96% virologically suppressed, median age 52) were included. Fourteen percent of participants were prescribed ≥1 ACH medication and 9% were prescribed ≥1 sedative medication. Overall, 40% of participants had NCI. Sedative medication use was associated with impaired attention/verbal learning and ACH medication use with motor skills deficits both in the continuous (mean z-score difference −0.26 to −0.14, P < .001 and P = .06) and binary (odds ratio [OR], ≥1.67; P < .05) models. Their combined use was associated with deficits in overall neurocognitive functions in both models (mean z-score difference −0.12, P = .002 and OR = 1.54, P = .03). These associations were unchanged in a subgroup analysis of participants without depression (n = 824).

Conclusions

Anticholinergic and sedative medications contribute to NCI. Clinicians need to consider these drugs when assessing NCI in PWH.

Screening Accuracy of Mini Addenbrooke's Cognitive Examination Test for HIV-Associated Neurocognitive Disorders in People Ageing with HIV

Aging and increased cardiovascular risk are major drivers for HIV-associated neurocognitive disorders (HAND), for which accurate screenings are lacking. Mini-Addenbrooke's Cognitive Examination (MACE) reliably detects vascular and neurodegenerative cognitive decline among HIV-negative patients. We evaluated MACE diagnostic accuracy in detecting HAND in people living with HIV (PLWH) and we compared it with the International HIV Dementia Scale (IHDS). A single-centre double-blind study of diagnostic accuracy on adult outpatient PLWH without neurocognitive confounding was performed. MACE and IHDS were administered in 5 and 10 min by clinicians, followed by the reference standard battery (14 tests) by neuropsychologists. HAND diagnosis was based on the modified version of Frascati's criteria by Gisslén to reduce false positives. Exploratory cut-offs were evaluated for MACE. Diagnostic accuracy and clinical utility parameters were assessed. 231 patients were enrolled. 75.7% men with a median age, education, and length of infection of 54 (48-59), 10 (8-13) and 16 (5-25) years. HAND prevalence was 48.5% (38.9% asymptomatic impairment). Compared to IHDS, MACE sensitivity (89.3% vs 70.5%), specificity (94.1% vs 63.0%), correct classification rate (86.5% vs 66.7%), J index (0.83 vs 0.34), AUROC (0.97 vs 0.79), agreement with the gold standard (k 0.84 vs 0.33) and effect size in distinguishing HAND vs non-HAND (d 2.11 vs 1.15) were higher. Among PLWH aged 65 years and above (n = 37) MACE performance was consistently better than IHDS. The quick and easy-to-perform MACE could possess an accurate and useful screening performance for HAND in otherwise neurocognitively healthy cohorts of PLWH.

Pitfalls of Antiretroviral Therapy: Current Status and Long-Term CNS Toxicity

HIV can traverse the BBB using a Trojan horse-like mechanism. Hidden within infected immune cells, HIV can infiltrate the highly safeguarded CNS and propagate disease. Once integrated within the host genome, HIV becomes a stable provirus, which can remain dormant, evade detection by the immune system or antiretroviral therapy (ART), and result in rebound viraemia. As ART targets actively replicating HIV, has low BBB penetrance, and exposes patients to long-term toxicity, further investigation into novel therapeutic approaches is required. Viral proteins can be produced by latent HIV, which may play a synergistic role alongside ART in promoting neuroinflammatory pathophysiology. It is believed that the ability to specifically target these proviral reservoirs would be a vital driving force towards a cure for HIV infection. A novel drug design platform, using the in-tandem administration of several therapeutic approaches, can be used to precisely target the various components of HIV infection, ultimately leading to the eradication of active and latent HIV and a functional cure for HIV. The aim of this review is to explore the pitfalls of ART and potential novel therapeutic alternatives.

Correlations between cerebrospinal fluid biomarkers, neurocognitive tests, and resting-state electroencephalography (rsEEG) in patients with HIV-associated neurocognitive disorders

HIV-associated neurocognitive disorders (HAND) are highly prevalent in people living with HIV (PLWH) despite successful treatment with combination antiretroviral therapy (cART). HAND pathogenesis is complex and definitive surrogate biomarkers are not clearly defined. Brain function has been assessed through the evaluation of cortical source rhythms with delta waves associated with neurological impairment. The aim of this study was to assess the correlation between EEG cortical sources, cerebrospinal fluid (CSF) biomarkers, and neurocognitive tests in PLWH with HAND. PLWH with HAND without significant comorbidities were enrolled. Baseline rsEEG-LORETA waves, CSF biomarkers (t-tau, p-tau, β-amiloid₄₂, neopterin, S100β), and neurocognitive tests were correlated and compared through non-parametric tests (Spearman's rho and Mann-Whitney); data are presented as medians (interquartile ranges). Fifty-four patients were enrolled. Median time of suppressed HIV-RNA and CD4⁺ T-lymphocyte were 10 years (5.5-15) and 691/uL (477-929). Thirty-nine participants (72%) underwent CSF collection: abnormal biomarkers were found in a small percentage. Only neopterin showed a statistically significant correlation with delta activity [parietal (rho 0.579; p < 0.001), occipital (rho 0.493; p = 0.007), and global sources (rho 0.464 p = 0.011)]. Seven patients (12.9%) showed an abnormal neopterin level (> 1.5 ng/mL) with significantly higher delta source activity compared to the ones with in-range concentrations. We observed a statistically significant correlation between working memory test Trail Making B with both CSF neopterin levels and delta waves (p values < 0.05). In a small sample of PLWH with HAND, we observed that higher CSF neopterin levels were associated with higher EEG delta waves and worse working memory tests.

Alzheimer Dementia in People Living With HIV

Objective

Given the aging of people living with HIV (PLWH) and the high prevalence of HIV-associated neurocognitive disorders, we aimed at describing the clinical, instrumental, and CSF features of PLWH diagnosed with Alzheimer dementia (AD).

Methods

The databases of 3 large Italian outpatient clinics taking care of more than 9,000 PLWH were searched for the diagnosis of AD. After obtaining patients' or their next of kin's consent for publication, anonymous data were collected in an excel spreadsheet and described. Routinely collected CSF biomarkers and radiologic imaging results were recorded whether available.

Results

Four patients were included in this case series who were diagnosed with AD aged between 60 and 74 years. All participants were on highly active antiretroviral therapy and showed nondetectable serum HIV RNA. Memory impairment was the most prominent cognitive feature. The diagnosis was obtained considering the exclusion of other potential causes, MRI and fluorodeoxyglucose-PET features, and, in (in 2/4), CSF AD biomarkers levels. In 1 patient, longitudinal CSF tau/p-tau increased, and beta-amyloid_1-42 decreased over time despite antiretroviral therapy containing nucleotide reverse transcriptase inhibitors.

Conclusions

In older PLWH cognitive symptoms may represent the onset of AD: a multidisciplinary team may be needed for reaching a likely in vivo diagnosis.

Confound, Cause, or Cure: The Effect of Cannabinoids on HIV-Associated Neurological Sequelae

The persistence of human immunodeficiency virus-1 (HIV)-associated neurocognitive disorders (HAND) in the era of effective antiretroviral therapy suggests that modern HIV neuropathogenesis is driven, at least in part, by mechanisms distinct from the viral life cycle. Identifying more subtle mechanisms is complicated by frequent comorbidities in HIV⁺ populations. One of the common confounds is substance abuse, with cannabis being the most frequently used psychoactive substance among people living with HIV. The psychoactive effects of cannabis use can themselves mimic, and perhaps magnify, the cognitive deficits observed in HAND; however, the neuromodulatory and anti-inflammatory properties of cannabinoids may counter HIV-induced excitotoxicity and neuroinflammation. Here, we review our understanding of the cross talk between HIV and cannabinoids in the central nervous system by exploring both clinical observations and evidence from preclinical in vivo and in vitro models. Additionally, we comment on recent advances in human, multi-cell in vitro systems that allow for more translatable, mechanistic studies of the relationship between cannabinoid pharmacology and this uniquely human virus.

Central nervous system (CNS) transcriptomic correlates of human immunodeficiency virus (HIV) brain RNA load in HIV-infected individuals

To generate new mechanistic hypotheses on the pathogenesis and disease progression of neuroHIV and identify novel therapeutic targets to improve neuropsychological function in people with HIV, we investigated host genes and pathway dysregulations associated with brain HIV RNA load in gene expression profiles of the frontal cortex, basal ganglia, and white matter of HIV+ patients. Pathway analyses showed that host genes correlated with HIV expression in all three brain regions were predominantly related to inflammation, neurodegeneration, and bioenergetics. HIV RNA load directly correlated particularly with inflammation genesets representative of cytokine signaling, and this was more prominent in white matter and the basal ganglia. Increases in interferon signaling were correlated with high brain HIV RNA load in the basal ganglia and the white matter although not in the frontal cortex. Brain HIV RNA load was inversely correlated with genesets that are indicative of neuronal and synaptic genes, particularly in the cortex, indicative of synaptic injury and neurodegeneration. Brain HIV RNA load was inversely correlated with genesets that are representative of oxidative phosphorylation, electron transfer, and the tricarboxylic acid cycle in all three brain regions. Mitochondrial dysfunction has been implicated in the toxicity of some antiretrovirals, and these results indicate that mitochondrial dysfunction is also associated with productive HIV infection. Genes and pathways correlated with brain HIV RNA load suggest potential therapeutic targets to ameliorate neuropsychological functioning in people living with HIV.

Humanized Mice for Infectious and Neurodegenerative disorders

Humanized mice model human disease and as such are used commonly for research studies of infectious, degenerative and cancer disorders. Recent models also reflect hematopoiesis, natural immunity, neurobiology, and molecular pathways that influence disease pathobiology. A spectrum of immunodeficient mouse strains permit long-lived human progenitor cell engraftments. The presence of both innate and adaptive immunity enables high levels of human hematolymphoid reconstitution with cell susceptibility to a broad range of microbial infections. These mice also facilitate investigations of human pathobiology, natural disease processes and therapeutic efficacy in a broad spectrum of human disorders. However, a bridge between humans and mice requires a complete understanding of pathogen dose, co-morbidities, disease progression, environment, and genetics which can be mirrored in these mice. These must be considered for understanding of microbial susceptibility, prevention, and disease progression. With known common limitations for access to human tissues, evaluation of metabolic and physiological changes and limitations in large animal numbers, studies in mice prove important in planning human clinical trials. To these ends, this review serves to outline how humanized mice can be used in viral and pharmacologic research emphasizing both current and future studies of viral and neurodegenerative diseases. In all, humanized mouse provides cost-effective, high throughput studies of infection or degeneration in natural pathogen host cells, and the ability to test transmission and eradication of disease.