HIV infects astrocytes in vivo and egresses from the brain to the periphery

The Proviral Reservoirs of Human Immunodeficiency Virus (HIV) Infection

Human Immunodeficiency Virus (HIV) proviral reservoirs are cells that harbor integrated HIV proviral DNA within their nuclear genomes. These cells form a heterogeneous group, represented by peripheral blood mononuclear cells (PBMCs), tissue-resident lymphoid and monocytic cells, and glial cells of the central nervous system. The importance of studying the properties of proviral reservoirs is connected with the inaccessibility of integrated HIV proviral DNA for modern anti-retroviral therapies (ARTs) that block virus reproduction. If treatment is not effective enough or is interrupted, the proviral reservoir can reactivate. Early initiation of ART improves the prognosis of the course of HIV infection, which is explained by the reduction in the proviral reservoir pool observed in the early stages of the disease. Different HIV subtypes present differences in the number of latent reservoirs, as determined by structural and functional differences. Unique signatures of patients with HIV, such as elite controllers, have control over viral replication and can be said to have achieved a functional cure for HIV infection. Uncovering the causes of this phenomenon will bring humanity closer to curing HIV infection, potential approaches to which include stem cell transplantation, clustered regularly interspaced short palindromic repeats (CRISPR)/cas9, "Shock and kill", "Block and lock", and the application of broad-spectrum neutralizing antibodies (bNAbs).

The impact of aging on HIV-1-related neurocognitive impairment

Depending on the population studied, HIV-1-related neurocognitive impairment is estimated to impact up to half the population of people living with HIV (PLWH) despite the availability of combination antiretroviral therapy (cART). Various factors contribute to this neurocognitive impairment, which complicates our understanding of the molecular mechanisms involved. Biological aging has been implicated as one factor possibly impacting the development and progression of HIV-1-related neurocognitive impairment. This is increasingly important as the life expectancy of PLWH with virologic suppression on cART is currently projected to be similar to that of individuals not living with HIV. Based on our increasing understanding of the biological aging process on a cellular level, we aim to dissect possible interactions of aging- and HIV-1 infection-induced effects and their role in neurocognitive decline. Thus, we begin by providing a brief overview of the clinical aspects of HIV-1-related neurocognitive impairment and review the accumulating evidence implicating aging in its development (Part I). We then discuss potential interactions between aging-associated pathways and HIV-1-induced effects at the molecular level (Part II).

All Blood Brain Barrier Cell Types Demonstrate Capability to Influence Differential Tenofovir and Emtricitabine Metabolism and Transport in the Brain

The blood brain barrier (BBB) represents a significant obstacle in brain drug penetration that challenges efforts in the treatment of neurological disorders. Therapeutically targeting the brain requires interactions with each BBB cell type, including endothelial cells, pericytes, and astrocytes. Yet, the relative contribution of these BBB cell types to the mechanisms that facilitate brain drug disposition is not well characterized. Here, we use first-line antiretroviral therapies, tenofovir (TFV) and emtricitabine (FTC), as models to investigate the mechanisms of drug transport and metabolism at the BBB that may influence access of the drug to the brain. We evaluated regional and cell-type-specific drug metabolism and transport mechanisms using rhesus macaques and in vitro treatment of primary human cells. We report heterogeneous distribution of TFV, FTC, and their active metabolites, which cerebrospinal fluid measures could not reflect. We found that all BBB cell types possessed functional drug-metabolizing enzymes and transporters that promoted TFV and FTC uptake and pharmacologic activation. Pericytes and astrocytes emerged as pharmacologically dynamic cells that rival hepatocytes and were uniquely susceptible to modulation by disease and treatment. Together, our findings demonstrate the importance of considering the BBB as a unique pharmacologic entity rather than viewing it as an extension of the liver, as each cell type possesses distinct drug metabolism and transport capacities that contribute to differential brain drug disposition. Further, our work highlights pharmacologically active pathways at the BBB that may regulate brain drug disposition and impact therapeutic efforts to alleviate neurologic disease.

Human Immunodeficiency Virus (HIV-1) Targets Astrocytes via Cell-Free and Cell-Associated Infection

BACKGROUND

Infection of astrocytes by Human Immunodeficiency Virus (HIV-1) remains a topic of debate, with conflicting data, yet instances of astrocytes containing viral DNA have been observed in vivo. In this study, we aimed to elucidate potential routes through which astrocytes could be infected and their ability to produce infectious particles using primary human astrocytes.

METHODS

We infected primary astrocytes derived from either neuroprogenitor cells (NPCs) or induced pluripotent stem cells (iPSCs) that express both C-X-C chemokine receptor type 4 (CXCR4) and the C-C chemokine receptor type 5 (CCR5) coreceptors, using either cell-free HIV-1 virus directly or cell-associated virus indirectly through infected macrophages and microglia.

RESULTS

Low-level infectivity by cell-free viruses was primarily attributed to a defect in the entry process. Bypassing HIV-specific receptor-mediated entry using pseudotyped viruses resulted in productive infection and the release of infectious particles.

CONCLUSIONS

These findings suggest that astrocytes may be one of the potential sources of neurotoxicity in HIV-associated neurocognitive disorders (HAND) and could possibly act as reservoirs for HIV in the central nervous system (CNS).

The challenges to detect, quantify, and characterize viral reservoirs in the current antiretroviral era

A major barrier to cure HIV is the early generation of viral reservoirs in tissues. These viral reservoirs can contain intact or defective proviruses, but both generates low levels of viral proteins contribute to chronic bystander damage even in the ART era. Most viral reservoir detection techniques are limited to blood-based, reactivation, and sequencing assays that lack spatial properties to examine the contribution of the host's microenvironment to latency and cure efforts. Currently, little is known about the contribution of the microenvironment to viral reservoir survival, residual viral expression, and associated inflammation. Only a few spatiotemporal techniques are available, and fewer integrate spatial genomics, transcriptomics, and proteomics into the analysis of the viral reservoir microenvironment-all essential components to cure HIV. During the development of these spatial techniques, many considerations need to be included in the analysis to avoid misinterpretation. This manuscript tries to clarify some critical concepts in viral reservoir detection by spatial techniques and the upcoming opportunities for cure efforts.

Drug Metabolism and Transport Capacity of Endothelial Cells, Pericytes, and Astrocytes: Implications for CNS Drug Disposition

Therapeutically targeting the brain requires interactions with endothelial cells, pericytes, and astrocytes at the blood brain barrier (BBB). We evaluated regional and cell-type specific drug metabolism and transport mechanisms using rhesus macaques and in vitro treatment of primary human cells. Here, we report heterogenous distribution of representative drugs, tenofovir (TFV), emtricitabine (FTC), and their active metabolites, which cerebrospinal fluid measures could not reflect. We found that all BBB cell types possessed functional drug metabolizing enzymes and transporters that promoted TFV and FTC uptake and pharmacologic activation. Pericytes and astrocytes emerged as pharmacologically dynamic cells that rivaled hepatocytes and were uniquely susceptible to modulation by disease and treatment. Together, our findings demonstrate the importance of considering the BBB as a unique pharmacologic entity, rather than viewing it as an extension of the liver, as each cell type possesses distinct drug metabolism and transport capacities that contribute to differential brain drug disposition.

The identification of intact HIV proviral DNA from human cerebrospinal fluid

We evaluated the HIV-1 DNA reservoir in peripheral blood mononuclear cells (PBMC) and cerebrospinal fluid (CSF) in people with HIV (PWH) and associations to cognitive dysfunction. Using the intact proviral DNA assay (IPDA), an emerging technique to identify provirus that may be the source of viral rebound, we assessed HIV DNA in CSF and PBMC in PWH regardless of antiretroviral therapy (ART). CSF was used as a sampling surrogate for the central nervous system (CNS) as opposed to tissue. IDPA results (3' defective, 5' defective, and intact HIV DNA) were analyzed by compartment (Wilcoxon signed rank; matched and unmatched pairs). Cognitive performance, measured via a battery of nine neuropsychological (NP) tests, were analyzed for correlation to HIV DNA (Spearman's rho). 11 CSF and 8 PBMC samples from PWH were evaluated both unmatched and matched. Total CSF HIV DNA was detectable in all participants and was significantly higher than in matched PBMCs (p ​= ​0.0039). Intact CSF HIV DNA was detected in 7/11 participants and correlated closely with those in PBMCs but tended to be higher in CSF than in PBMC. CSF HIV DNA did not correlate with global NP performance, but higher values did correlate with worse executive function (p ​= ​0.0440). Intact HIV DNA is frequently present in the CSF of PWH regardless of ART. This further supports the presence of an HIV CNS reservoir and provides a method to study CNS reservoirs during HIV cure studies. Larger studies are needed to evaluate relationships with CNS clinical outcomes.

HIV-1 infection promotes neuroinflammation and neuron pathogenesis in novel microglia-containing cerebral organoids

Cerebral organoids (COs) are a valuable tool to study the intricate interplay between glial cells and neurons in brain development and disease, including HIV-associated neuroinflammation. We developed a novel approach to generate microglia containing COs (CO-iMs) by co-culturing hematopoietic progenitors and induced pluripotent stem cells. This approach allowed for the differentiation of microglia within the organoids concomitantly to the neuronal progenitors. CO- iMs exhibited higher efficiency in generation of CD45 + /CD11b + /Iba-1 + microglia cells compared to conventional COs with physiologically relevant proportion of microglia (∼7%). CO-iMs exhibited substantially higher expression of microglial homeostatic and sensome markers as well as markers for the complement cascade. CO-iMs showed susceptibility to HIV infection resulting in a significant increase in several pro-inflammatory cytokines/chemokines and compromised neuronal function, which were abrogated by addition of antiretrovirals. Thus, CO-iM is a robust model to decipher neuropathogenesis, neurological disorders, and viral infections of brain cells in a 3D culture system.

Limited HIV-associated neuropathologies and lack of immune activation in sub-saharan African individuals with late-stage subtype C HIV-1 infection

Although previous studies have suggested that subtype B HIV-1 proviruses in the brain are associated with physiological changes and immune activation accompanied with microgliosis and astrogliosis, and indicated that both HIV-1 subtype variation and geographical location might influence the neuropathogenicity of HIV-1 in the brain. The natural course of neuropathogenesis of the most widespread subtype C HIV-1 has not been adequately investigated, especially for people living with HIV (PLWH) in sub-Saharan Africa. To characterize the natural neuropathology of subtype C HIV-1, postmortem frontal lobe and basal ganglia tissues were collected from nine ART-naïve individuals who died of late-stage AIDS with subtype C HIV-1 infection, and eight uninfected deceased individuals as controls. Histological staining was performed on all brain tissues to assess brain pathologies. Immunohistochemistry (IHC) against CD4, p24, Iba-1, GFAP, and CD8 in all brain tissues was conducted to evaluate potential viral production and immune activation. Histological results showed mild perivascular cuffs of lymphocytes only in a minority of the infected individuals. Viral capsid p24 protein was only detected in circulating immune cells of one infected individual, suggesting a lack of productive HIV-1 infection of the brain even at the late-stage of AIDS. Notably, similar levels of Iba-1 or GFAP between HIV + and HIV- brain tissues indicated a lack of microgliosis and astrogliosis, respectively. Similar levels of CD8 + cytotoxic T lymphocyte (CTL) infiltration between HIV + and HIV- brain tissues indicated CTL were not likely to be involved within subtype C HIV-1 infected participants of this cohort. Results from this subtype C HIV-1 study suggest that there is a lack of productive infection and limited neuropathogenesis by subtype C HIV-1 even at late-stage disease, which is in contrast to what was reported for subtype B HIV-1 by other investigators.

Ionic Liquid Coating-Driven Nanoparticle Delivery to the Brain: Applications for NeuroHIV

Delivering cargo to the central nervous system (CNS) remains a pharmacological challenge. For infectious diseases such as HIV, the CNS acts as a latent reservoir that is inadequately managed by systemic antiretrovirals (ARTs). ARTs thus cannot eradicate HIV, and given CNS infection, patients experience neurological deficits collectively referred to as "neuroHIV". Herein, the development of bioinspired ionic liquid-coated nanoparticles (IL-NPs) for in situ hitchhiking on red blood cells (RBCs) is reported, which enables 48% brain delivery of intracarotid arterial- infused cargo. Moreover, IL choline trans-2-hexenoate (CA2HA 1:2) demonstrates preferential accumulation in parenchymal microglia over endothelial cells post-delivery. This study further demonstrates successful loading of abacavir (ABC), an ART that is challenging to encapsulate, into IL-NPs, and verifies retention of antiviral efficacy in vitro. IL-NPs are not cytotoxic to primary human peripheral blood mononuclear cells (PBMCs) and the CA2HA 1:2 coating itself confers notable anti-viremic capacity. In addition, in vitro cell culture assays show markedly increased uptake of IL-NPs into neural cells compared to bare PLGA nanoparticles. This work debuts bioinspired ionic liquids as promising nanoparticle coatings to assist CNS biodistribution and has the potential to revolutionize the delivery of cargos (i.e., drugs, viral vectors) through compartmental barriers such as the blood-brain-barrier (BBB).

HIV-1 and methamphetamine co-treatment in primary human astrocytes: TAARgeting ER/UPR dysfunction

Objectives

Human immunodeficiency virus 1 (HIV-1) can invade the central nervous system (CNS) early during infection and persist in the CNS for life despite effective antiretroviral treatment. Infection and activation of residential glial cells lead to low viral replication and chronic inflammation, which damage neurons contributing to a spectrum of HIV-associated neurocognitive disorders (HAND). Substance use, including methamphetamine (METH), can increase one's risk and severity of HAND. Here, we investigate HIV-1/METH co-treatment in a key neurosupportive glial cell, astrocytes. Specifically, mitochondria-associated endoplasmic reticulum (ER) membrane (MAM) signaling pathways, such as calcium and the unfolded protein response (UPR), are key mechanisms underlying HAND pathology and arise as potential targets to combat astrocyte dysfunction.

Methods

Primary human astrocytes were transduced with a pseudotyped HIV-1 model and exposed to low-dose METH for seven days. We assessed changes in astrocyte HIV-1 infection, inflammation, mitochondrial antioxidant and dynamic protein expression, respiratory acitivity, mitochondrial calcium flux, and UPR/MAM mediator expression. We then tested a selective antagonist for METH-binding receptor, trace amine-associated receptor 1 (TAAR1) as a potetnial upstream regulator of METH-induced calcium flux and UPR/MAM mediator expression.

Results

Chronic METH exposure increased astrocyte HIV-1 infection. Moreover, HIV-1/METH co-treatment suppressed astrocyte antioxidant and metabolic capacity while increasing mitochondrial calcium load and protein expression of UPR messengers and MAM mediators. Notably, HIV-1 increases astrocyte TAAR1 expression, thus, could be a critical regulator of HIV-1/METH co-treatment in astrocytes. Indeed, selective antagonism of TAAR1 significantly inhibited cytosolic calcium flux and induction of UPR/MAM protein expression.

Conclusion

Altogether, our findings demonstrate HIV-1/METH-induced ER-mitochondrial dysfunction in astrocytes, whereas TAAR1 may be an upstream regulator for HIV-1/METH-mediated astrocyte dysfunction.

The multifaceted nature of HIV tissue reservoirs

PURPOSE OF REVIEW

To underline the complexity and the heterogeneity of the HIV reservoir.

RECENT FINDINGS

While lymphoid tissues (spleen, lymph nodes, gut-associated lymphoid tissue) harbor specific subsets of specialized CD4 +  T cells enriched in HIV-infected cells, non-CD4 +  T cell reservoirs such as tissue-resident macrophages and dendritic cells have also been implicated to contribute to viral persistence. Moreover, studies have applied highly sensitive tools to detect transcriptional activity within HIV-infected cells during prolonged ART and revealed a broader spectrum of transcriptional activity for proviruses than previously thought. Finally, while a combination of factors might be involved in the regulation of HIV persistence within different tissues and remains to be fully elucidated, recent results from autopsy samples of HIV-infected ART suppressed individuals indicate extensive clonality of HIV reservoirs in multiple tissues and suggest that the recirculation of HIV-infected cells and their local expansions in tissues may also contribute to the complexity of the HIV reservoirs in humans.

SUMMARY

HIV persistence in blood and multiple tissues despite long-standing and potent therapy is one of the major barriers to a cure. Given that the HIV reservoir is established early and is highly complex based on its composition, viral diversity, tissue distribution, transcriptional activity, replication competence, migration dynamics and proliferative potential across the human body and possible compartmentalization in specific tissues, combinatorial therapeutic approaches are needed that may synergize to target multiple viral reservoirs to achieve a cure for HIV infection.

HIV-1 Myeloid Reservoirs - Contributors to Viral Persistence and Pathogenesis

PURPOSE OF REVIEW

HIV reservoirs are the main barrier to cure. CD4+ T cells have been extensively studied as the primary HIV-1 reservoir. However, there is substantial evidence that HIV-1-infected myeloid cells (monocytes/macrophages) also contribute to viral persistence and pathogenesis.

RECENT FINDINGS

Recent studies in animal models and people with HIV-1 demonstrate that myeloid cells are cellular reservoirs of HIV-1. HIV-1 genomes and viral RNA have been reported in circulating monocytes and tissue-resident macrophages from the brain, urethra, gut, liver, and spleen. Importantly, viral outgrowth assays have quantified persistent infectious virus from monocyte-derived macrophages and tissue-resident macrophages. The myeloid cell compartment represents an important target of HIV-1 infection. While myeloid reservoirs may be more difficult to measure than CD4+ T cell reservoirs, they are long-lived, contribute to viral persistence, and, unless specifically targeted, will prevent an HIV-1 cure.

Targeting HIV persistence in the tissue

PURPOSE OF REVIEW

The complex nature and distribution of the HIV reservoir in tissue of people with HIV remains one of the major obstacles to achieve the elimination of HIV persistence. Challenges include the tissue-specific states of latency and viral persistence, which translates into high levels of reservoir heterogeneity. Moreover, the best strategies to reach and eliminate these reservoirs may differ based on the intrinsic characteristics of the cellular and anatomical reservoir to reach.

RECENT FINDINGS

While major focus has been undertaken for lymphoid tissues and follicular T helper cells, evidence of viral persistence in HIV and non-HIV antigen-specific CD4 + T cells and macrophages resident in multiple tissues providing long-term protection presents new challenges in the quest for an HIV cure. Considering the microenvironments where these cellular reservoirs persist opens new venues for the delivery of drugs and immunotherapies to target these niches. New tools, such as single-cell RNA sequencing, CRISPR screenings, mRNA technology or tissue organoids are quickly developing and providing detailed information about the complex nature of the tissue reservoirs.

SUMMARY

Targeting persistence in tissue reservoirs represents a complex but essential step towards achieving HIV cure. Combinatorial strategies, particularly during the early phases of infection to impact initial reservoirs, capable of reaching and reactivating multiple long-lived reservoirs in the body may lead the path.

Cenicriviroc prevents dysregulation of astrocyte/endothelial cross talk induced by ischemia and HIV-1 via inhibiting the NLRP3 inflammasome and pyroptosis

Blood-brain barrier (BBB) breakdown is one of the pathophysiological characteristics of ischemic stroke, which may contribute to the progression of brain tissue damage and subsequent neurological impairment. Human immunodeficiency virus (HIV)-infected individuals are at greater risk for ischemic stroke due to diminished immune function and HIV-associated vasculopathy. Studies have shown that astrocytes are involved in maintaining BBB integrity and facilitating HIV-1 infection in the brain. The present study investigated whether targeting astrocyte-endothelial cell signaling with cenicriviroc (CVC), a dual chemokine receptor (CCR)2 and CCR5 antagonist, may protect against dysregulation of cross talk between these cells after oxygen-glucose deprivation/reoxygenation (OGD/R) combined with HIV-1 infection. Permeability assay with 10 kDa fluorescein isothiocyanate (FITC)-dextran demonstrated that CVC alleviated endothelial barrier disruption in noncontact coculture of human brain microvascular endothelial cells (HBMECs) with HIV-1-infected human astrocytes, and reversed downregulation of tight junction protein claudin-5 induced by OGD/R- and HIV-1. Moreover, CVC attenuated OGD/R- and HIV-1-triggered upregulation of the NOD-like receptor protein-3 (NLRP3) inflammasome and IL-1β secretion. Treatment with CVC also suppressed astrocyte pyroptosis by attenuating cleaved caspase-1 levels and the formation of cleaved N-terminal GSDMD (N-GSDMD). Secretome profiling revealed that CVC ameliorated secretion levels of chemokine CC chemokine ligand 17 (CCL17), adhesion molecule intercellular adhesion molecule-1 (ICAM-1), and T cell activation modulator T cell immunoglobulin and mucin domain 3 (TIM-3) by astrocytes synergistically induced by OGD/R and HIV-1. Overall, these results suggest that CVC contributes to restoring astrocyte-endothelial cross interactions in an astrocyte-dependent manner via protection against NLRP3 activation and pyroptosis.NEW & NOTEWORTHY The present study reveals the role of astrocytic NOD-like receptor protein-3 (NLRP3) inflammasome in dysfunctional astrocyte-endothelial cross interactions triggered in response to oxygen/glucose deprivation injury associated with human immunodeficiency virus type 1 (HIV-1) infection. Our results suggest that blocking NLRP3 inflammasome activation and pyroptosis-mediated inflammation with cenicriviroc (CVC) may constitute a potentially effective therapeutic strategy for blood-brain barrier (BBB) protection during HIV-1-associated ischemic stroke.

Mechanisms of Intracellular Communication in Cancer and Pathogen Spreading

Cell-to-cell interactions are essential for proper development, homeostasis, and complex syncytia/organ formation and function. Intercellular communication are mediated by multiple mechanisms including soluble mediators, adhesion molecules and specific mechanisms of cell to cell communication such as Gap junctions (GJ), tunneling nanotubes (TNT), and exosomes. Only recently, has been discovered that TNTs and exosomes enable the exchange of large signaling molecules, RNA, viral products, antigens, and organelles opening new avenues of research and therapeutic approaches. The focus of this review is to summarize these recent findings in physiologic and pathologic conditions.

AKT signaling modulates latent viral reservoir viability in HIV-1-infected blood-brain barrier pericytes

Despite antiretroviral therapy (ART), chronic forms of HIV-associated neurocognitive disorders (HAND) affect an estimated 50% of individuals living with HIV, greatly impacting their quality of life. The prevailing theory of HAND progression posits that chronic inflammation arising from the activation of latent viral reservoirs leads to progressive damage in the central nervous system (CNS). Recent evidence indicates that blood-brain barrier (BBB) pericytes are capable of active HIV-1 infection; however, their latent infection has not been defined. Given their location and function, BBB pericytes are poised to be a key viral reservoir in the development of HAND. We present the first transcriptional analysis of uninfected, active, and latent human BBB pericytes, revealing distinct transcriptional phenotypes. In addition, we demonstrate that latent infection of BBB pericytes relies on AKT signaling for reservoir survival. These findings provide insight into the state of reservoir maintenance in the CNS during HIV-1 infection and provide novel targets for reservoir clearance.

Correlative Imaging to Detect Rare HIV Reservoirs and Associated Damage in Tissues

Correlative light-electron microscopy (CLEM) has evolved in the last decades, especially after significant developments in sample preparation, imaging acquisition, software, spatial resolution, and equipment, including confocal, live-cell, super-resolution, and electron microscopy (scanning, transmission, focused ion beam, and cryo-electron microscopy). However, the recent evolution of different laser-related techniques, such as mass spectrometry imaging (MSI) and laser capture microdissection, could further expand spatial imaging capabilities into high-resolution OMIC approaches such as proteomic, lipidomics, small molecule, and drug discovery. Here, we will describe a protocol to integrate the detection of rare viral reservoirs with imaging mass spectrometry.

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.

Differences in drug resistance of HIV-1 genotypes in CSF and plasma and analysis of related factors

The emergence of HIV drug resistance seriously affects the quality of life of patients. However, there has been no extensive study of CSF resistance. The aim of this study is to evaluate common HIV-1 resistance in CSF and compare it with resistance in matched plasma, and analyse the influencing factors of cerebrospinal fluid drug resistance. The matched CSF and plasma samples of 62 HIV-1 patients were tested at one study site in China (Chongqing; 2019-2022). HIV genotyping and drug resistance was evaluated using the Stanford v8.7 algorithm. The diagnosis and treatment data and basic information were collected from the clinical case system, and the influencing factors of drug resistance mutations in CSF was obtained by variance analysis. CSF and matched plasma HIV-1 subtypes were confirmed in 62 patients, and the most frequent recombinant form was CRF07-BC (64.5%). Thirteen patients (21.0%) were detected with drug-resistant mutations, and the sites were consistent in both CSF and matched plasma. The drug-resistant ratios of untreated patients and treated patients were 5/51 (9.8%) and 8/11 (72.7%), respectively. The type with the highest mutation frequency was NNRTI, and no mutation was found in INSTI. Multivariate analysis indicated that ARV treatment was associated with CSF resistance (P < 0.001). The subtypes and drug resistance mutation sites are consistent in CSF and matched plasma samples of HIV-1 patients, and there is a correlation between ARV treatment and possible drug resistance, especially in CSF reservoirs. These findings highlight the concern about CSF drug resistance in HIV patients.

HIV-1 Tat commandeers nuclear export of Rev-viral RNA complex by controlling hnRNPA2-mediated splicing

IMPORTANCE

HIV-infected host cells impose varied degrees of regulation on viral replication, from very high to abortive. Proliferation of HIV in astrocytes is limited when compared to immune cells, such as CD4+ T lymphocytes. Understanding such differential regulation is one of the key questions in the field as these cells permit HIV persistence and rebound viremia, challenging HIV treatment and clinical cure. This study focuses on understanding the molecular mechanism behind such cell-specific disparities. We show that one of the key mechanisms is the regulation of heterogenous nuclear ribonucleoprotein A2, a host factor involved in alternative splicing and RNA processing, by HIV-1 Tat in CD4+ T lymphocytes, not observed in astrocytes. This regulation causes an increase in the levels of unspliced/partially spliced viral RNA and nuclear export of Rev-RNA complexes which results in high viral propagation in CD4+ T lymphocytes. The study reveals a new mechanism imposed by HIV on host cells that determines the fate of infection.

HIV-1 and opiates modulate miRNA profiles in extracellular vesicles

Opiate abuse increases the risk of HIV transmission and exacerbates HIV neuropathology by increasing inflammation and modulating immune cell function. Exosomal EVs(xEV) contain miRNAs that may be differentially expressed due to HIV infection or opiate abuse. Here we develop a preliminary exosomal-miRNA biomarker profile of HIV-infected PBMCs in the context of opiate use. PBMCs infected with HIV were treated with increasing dosages of morphine for 72 hours, the culture supernatants were collected, and the exosomes isolated using differential centrifugation. Exosomal miRNAs were extracted, expression levels determined via Nanostring multiplexed microRNA arrays, and analyzed with Webgestalt. The effect of the exosomes on neuronal function was determined by measuring calcium. Preliminary findings show that HIV-1 infection altered the miRNA profile of PBMC-derived EVs concurrently with opiate exposure. MicroRNA, hsa-miR-1246 was up-regulated 12-fold in the presence of morphine, relative to uninfected control. PBMCs infected with HIV-1 MN, an X4-tropic HIV-1 strain and exposed to morphine, displayed a trend which suggests potential synergistic effects between HIV-1 infection and morphine exposure promoting an increase in viral replication. Dose-dependent differences were observed in miRNA expression as a result of opiate exposure. The xEVs derived from PBMCs exposed to morphine or HIV modulated neuronal cell function. SH-SY5Y cells, treated with xEVs derived from ART-treated PBMCs, exhibited increased viability while for SH-SY5Ys exposed to xEVs derived from HIV-1 infected PBMCs viability was decreased compared to the untreated control. Exposing SH-SY5Y to xEVs derived from HIV-infected PBMCs resulted in significant decrease in calcium signaling, relative to treatment with xEVs derived from uninfected PBMCs. Overall, HIV-1 and morphine induced differential miRNA expression in PBMC-derived exosomes, potentially identifying mechanisms of action or novel therapeutic targets involved in opiate use disorder, HIV neuropathology, TNF signaling pathway, NF-κB signaling pathway, autophagy, and apoptosis in context of HIV infection.

Neurological, Behavioral, and Pathophysiological Characterization of the Co-Occurrence of Substance Use and HIV: A Narrative Review

Combined antiretroviral therapy (cART) has greatly reduced the severity of HIV-associated neurocognitive disorders in people living with HIV (PLWH); however, PLWH are more likely than the general population to use drugs and suffer from substance use disorders (SUDs) and to exhibit risky behaviors that promote HIV transmission and other infections. Dopamine-boosting psychostimulants such as cocaine and methamphetamine are some of the most widely used substances among PLWH. Chronic use of these substances disrupts brain function, structure, and cognition. PLWH with SUD have poor health outcomes driven by complex interactions between biological, neurocognitive, and social factors. Here we review the effects of comorbid HIV and psychostimulant use disorders by discussing the distinct and common effects of HIV and chronic cocaine and methamphetamine use on behavioral and neurological impairments using evidence from rodent models of HIV-associated neurocognitive impairments (Tat or gp120 protein expression) and clinical studies. We also provide a biopsychosocial perspective by discussing behavioral impairment in differentially impacted social groups and proposing interventions at both patient and population levels.

An Efficient and Cost-Effective Approach to Generate Functional Human Inducible Pluripotent Stem Cell-Derived Astrocytes

Human inducible pluripotent stem cell (hiPSC)-derived astrocytes (iAs) are critical to study astrocytes in health and disease. They provide several advantages over human fetal astrocytes in research, which include consistency, availability, disease modeling, customization, and ethical considerations. The generation of iAs is hampered by the requirement of Matrigel matrix coating for survival and proliferation. We provide a protocol demonstrating that human iAs cultured in the absence of Matrigel are viable and proliferative. Further, through a side-by-side comparison of cultures with and without Matrigel, we show significant similarities in astrocyte-specific profiling, including morphology (shape and structure), phenotype (cell-specific markers), genotype (transcriptional expression), metabolic (respiration), and functional aspects (glutamate uptake and cytokine response). In addition, we report that, unlike other CNS cell types, such as neuronal progenitor cells and neurons, iAs can withstand the absence of Matrigel coating. Our study demonstrates that Matrigel is dispensable for the culture of human iPSC-derived astrocytes, facilitating an easy, streamlined, and cost-effective method of generating these cells.

Astrocytes: Role in pathogenesis and effect of commonly misused drugs in the HIV infected brain

The roles of astrocytes as reservoirs and producers of a subset of viral proteins in the HIV infected brain have been studied extensively as a key to understanding HIV-associated neurocognitive disorders (HAND). However, their comprehensive role in the context of intersecting substance use and neurocircuitry of the reward pathway and HAND has yet to be fully explained. Use of methamphetamines, cocaine, or opioids in the context of HIV infection have been shown to lead to a faster progression of HAND. Glutamatergic, dopaminergic, and GABAergic systems are implicated in the development of HAND-induced cognitive impairments. A thorough review of scientific literature exploring the variety of mechanisms in which these drugs exert their effects on the HIV brain and astrocytes has revealed marked areas of convergence in overexcitation leading to increased drug-seeking behavior, inflammation, apoptosis, and irreversible neurotoxicity. The present review investigates astrocytes, the neural pathways, and mechanisms of drug disruption that ultimately play a larger holistic role in terms of HIV progression and drug use. There are opportunities for future research, therapeutic intervention, and preventive strategies to diminish HAND in the subset population of patients with HIV and substance use disorder.

Recent advances in poor HIV immune reconstitution: what will the future look like?

Combination antiretroviral therapy has demonstrated proved effectiveness in suppressing viral replication and significantly recovering CD4+ T cell count in HIV type-1 (HIV-1)-infected patients, contributing to a dramatic reduction in AIDS morbidity and mortality. However, the factors affecting immune reconstitution are extremely complex. Demographic factors, co-infection, baseline CD4 cell level, abnormal immune activation, and cytokine dysregulation may all affect immune reconstitution. According to report, 10-40% of HIV-1-infected patients fail to restore the normalization of CD4+ T cell count and function. They are referred to as immunological non-responders (INRs) who fail to achieve complete immune reconstitution and have a higher mortality rate and higher risk of developing other non-AIDS diseases compared with those who achieve complete immune reconstitution. Heretofore, the mechanisms underlying incomplete immune reconstitution in HIV remain elusive, and INRs are not effectively treated or mitigated. This review discusses the recent progress of mechanisms and factors responsible for incomplete immune reconstitution in AIDS and summarizes the corresponding therapeutic strategies according to different mechanisms to improve the individual therapy.

Clinical evidence of human pathogens implicated in Alzheimer's disease pathology and the therapeutic efficacy of antimicrobials: an overview

A wealth of pre-clinical reports and data derived from human subjects and brain autopsies suggest that microbial infections are relevant to Alzheimer's disease (AD). This has inspired the hypothesis that microbial infections increase the risk or even trigger the onset of AD. Multiple models have been developed to explain the increase in pathogenic microbes in AD patients. Although this hypothesis is well accepted in the field, it is not yet clear whether microbial neuroinvasion is a cause of AD or a consequence of the pathological changes experienced by the demented brain. Along the same line, the gut microbiome has also been proposed as a modulator of AD. In this review, we focus on human-based evidence demonstrating the elevated abundance of microbes and microbe-derived molecules in AD hosts as well as their interactions with AD hallmarks. Further, the direct-purpose and potential off-target effects underpinning the efficacy of anti-microbial treatments in AD are also addressed.

Evaluation of Archival HIV DNA in Brain and Lymphoid Tissues

HIV reservoirs persist in anatomic compartments despite antiretroviral therapy (ART). Characterizing archival HIV DNA in the central nervous system (CNS) and other tissues is crucial to inform cure strategies. We evaluated paired autopsy brain-frontal cortex (FC), occipital cortex (OCC), and basal ganglia (BG)-and peripheral lymphoid tissues from 63 people with HIV. Participants passed away while virally suppressed on ART at the last visit and without evidence of CNS opportunistic disease. We quantified total HIV DNA in all participants and obtained full-length HIV-envelope (FL HIV-env) sequences from a subset of 14 participants. We detected HIV DNA (gag) in most brain (65.1%) and all lymphoid tissues. Lymphoid tissues had higher HIV DNA levels than the brain (P < 0.01). Levels of HIV gag between BG and FC were similar (P > 0.2), while OCC had the lowest levels (P = 0.01). Females had higher HIV DNA levels in tissues than males (gag, P = 0.03; 2-LTR, P = 0.05), suggesting possible sex-associated mechanisms for HIV reservoir persistence. Most FL HIV-env sequences (n = 143) were intact, while 42 were defective. Clonal sequences were found in 8 out of 14 participants, and 1 participant had clonal defective sequences in the brain and spleen, suggestive of cell migration. From 10 donors with paired brain and lymphoid sequences, we observed evidence of compartmentalized sequences in 2 donors. Our data further the idea that the brain is a site for archival HIV DNA during ART where compartmentalized provirus may occur in a subset of people. Future studies assessing FL HIV-provirus and replication competence are needed to further evaluate the HIV reservoirs in tissues. IMPORTANCE HIV infection of the brain is associated with adverse neuropsychiatric outcomes, despite efficient antiretroviral treatment. HIV may persist in reservoirs in the brain and other tissues, which can seed virus replication if treatment is interrupted, representing a major challenge to cure HIV. We evaluated reservoirs and genetic features in postmortem brain and lymphoid tissues from people with HIV who passed away during suppressed HIV replication. We found a differential distribution of HIV reservoirs across brain regions which was lower than that in lymphoid tissues. We observed that most HIV reservoirs in tissues had intact envelope sequences, suggesting they could potentially generate replicative viruses. We found that women had higher HIV reservoir levels in brain and lymphoid tissues than men, suggesting possible sex-based mechanisms of maintenance of HIV reservoirs in tissues, warranting further investigation. Characterizing the archival HIV DNA in tissues is important to inform future HIV cure strategies.

Humanized Mice for Studies of HIV-1 Persistence and Elimination

A major roadblock to achieving a cure for human immunodeficiency virus type one (HIV-1) is the persistence of latent viral infections in the cells and tissue compartments of an infected human host. Latent HIV-1 proviral DNA persists in resting memory CD4+ T cells and mononuclear phagocytes (MPs; macrophages, microglia, and dendritic cells). Tissue viral reservoirs of both cell types reside in the gut, lymph nodes, bone marrow, spleen, liver, kidney, skin, adipose tissue, reproductive organs, and brain. However, despite the identification of virus-susceptible cells, several limitations persist in identifying broad latent reservoirs in infected persons. The major limitations include their relatively low abundance, the precise identification of latently infected cells, and the lack of biomarkers for identifying latent cells. While primary MP and CD4+ T cells and transformed cell lines are used to interrogate mechanisms of HIV-1 persistence, they often fail to accurately reflect the host cells and tissue environments that carry latent infections. Given the host specificity of HIV-1, there are few animal models that replicate the natural course of viral infection with any precision. These needs underlie the importance of humanized mouse models as both valuable and cost-effective tools for studying viral latency and subsequently identifying means of eliminating it. In this review, we discuss the advantages and limitations of humanized mice for studies of viral persistence and latency with an eye toward using these models to test antiretroviral and excision therapeutics. The goals of this research are to use the models to address how and under which circumstances HIV-1 latency can be detected and eliminated. Targeting latent reservoirs for an ultimate HIV-1 cure is the task at hand.

The role of tunneling nanotubes during early stages of HIV infection and reactivation: implications in HIV cure

Tunneling nanotubes (TNTs), also called cytonemes or tumor microtubes, correspond to cellular processes that enable long-range communication. TNTs are plasma membrane extensions that form tubular processes that connect the cytoplasm of two or more cells. TNTs are mostly expressed during the early stages of development and poorly expressed in adulthood. However, in disease conditions such as stroke, cancer, and viral infections such as HIV, TNTs proliferate, but their role is poorly understood. TNTs function has been associated with signaling coordination, organelle sharing, and the transfer of infectious agents such as HIV. Here, we describe the critical role and function of TNTs during HIV infection and reactivation, as well as the use of TNTs for cure strategies.

The multitaskers of the brain: Glial responses to viral infections and associated post-infectious neurologic sequelae

Many viral infections cause acute and chronic neurologic diseases which can lead to degeneration of cortical functions. While neurotropic viruses that gain access to the central nervous system (CNS) may induce brain injury directly via infection of neurons or their supporting cells, they also alter brain function via indirect neuroimmune mechanisms that may disrupt the blood-brain barrier (BBB), eliminate synapses, and generate neurotoxic astrocytes and microglia that prevent recovery of neuronal circuits. Non-neuroinvasive, neurovirulent viruses may also trigger aberrant responses in glial cells, including those that interfere with motor and sensory behaviors, encoding of memories and executive function. Increasing evidence from human and animal studies indicate that neuroprotective antiviral responses that amplify levels of innate immune molecules dysregulate normal neuroimmune processes, even in the absence of neuroinvasion, which may persist after virus is cleared. In this review, we discuss how select emerging and re-emerging RNA viruses induce neuroimmunologic responses that lead to dysfunction of higher order processes including visuospatial recognition, learning and memory, and motor control. Identifying therapeutic targets that return the neuroimmune system to homeostasis is critical for preventing virus-induced neurodegenerative disorders.

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.

Myelin regulatory factor is a target of individual and interactive effects of HIV-1 Tat and morphine in the striatum and pre-frontal cortex

HIV-associated neurocognitive disorders (HAND) remain pervasive even with increased efficacy/use of antiretroviral therapies. Opioid use/abuse among HIV + individuals is documented to exacerbate CNS deficits. White matter (WM) alterations, including myelin pallor, and volume/structural alterations detected by diffusion tensor imaging are common observations in HIV + individuals, and studies in non-human primates suggest that WM may harbor virus. Using transgenic mice that express the HIV-1 Tat protein, we examined in vivo effects of 2-6 weeks of Tat and morphine exposure on WM using genomic and biochemical methods. RNA sequencing of striatal tissue at 2 weeks revealed robust changes in mRNAs associated with oligodendrocyte precursor populations and myelin integrity, including those for transferrin, the atypical oligodendrocyte marker N-myc downstream regulated 1 (Ndrg1), and myelin regulatory factor (Myrf/Mrf), an oligodendrocyte-specific transcription factor with a significant role in oligodendrocyte differentiation/maturation. Western blots conducted after 6-weeks exposure in 3 brain regions (striatum, corpus callosum, pre-frontal cortex) revealed regional differences in the effect of Tat and morphine on Myrf levels, and on levels of myelin basic protein (MBP), whose transcription is regulated by Myrf. Responses included individual and interactive effects. Although baseline and post-treatment levels of Myrf and MBP differed between brain regions, post-treatment MBP levels in striatum and pre-frontal cortex were compatible with changes in Myrf activity. Additionally, the Myrf regulatory ubiquitin ligase Fbxw7 was identified as a novel target in our model. These results suggest that Myrf and Fbxw7 contribute to altered myelin gene regulation in HIV.

Involvement of lncRNA TUG1 in HIV-1 Tat-Induced Astrocyte Senescence

HIV-1 infection in the era of combined antiretroviral therapy has been associated with premature aging. Among the various features of HIV-1 associated neurocognitive disorders, astrocyte senescence has been surmised as a potential cause contributing to HIV-1-induced brain aging and neurocognitive impairments. Recently, lncRNAs have also been implicated to play essential roles in the onset of cellular senescence. Herein, using human primary astrocytes (HPAs), we investigated the role of lncRNA TUG1 in HIV-1 Tat-mediated onset of astrocyte senescence. We found that HPAs exposed to HIV-1 Tat resulted in significant upregulation of lncRNA TUG1 expression that was accompanied by elevated expression of p16 and p21, respectively. Additionally, HIV-1 Tat-exposed HPAs demonstrated increased expression of senescence-associated (SA) markers-SA-β-galactosidase (SA-β-gal) activity and SA-heterochromatin foci-cell-cycle arrest, and increased production of reactive oxygen species and proinflammatory cytokines. Intriguingly, gene silencing of lncRNA TUG1 in HPAs also reversed HIV-1 Tat-induced upregulation of p21, p16, SA-β gal activity, cellular activation, and proinflammatory cytokines. Furthermore, increased expression of astrocytic p16 and p21, lncRNA TUG1, and proinflammatory cytokines were observed in the prefrontal cortices of HIV-1 transgenic rats, thereby suggesting the occurrence of senescence activation in vivo. Overall, our data indicate that HIV-1 Tat-induced astrocyte senescence involves the lncRNA TUG1 and could serve as a potential therapeutic target for dampening accelerated aging associated with HIV-1/HIV-1 proteins.

HIV Latency and Nanomedicine Strategies for Anti-HIV Treatment and Eradication

Antiretrovirals (ARVs) reduce Human Immunodeficiency Virus (HIV) loads to undetectable levels in infected patients. However, HIV can persist throughout the body in cellular reservoirs partly due to the inability of some ARVs to cross anatomical barriers and the capacity of HIV-1 to establish latent infection in resting CD4⁺ T cells and monocytes/macrophages. A cure for HIV is not likely unless latency is addressed and delivery of ARVs to cellular reservoir sites is improved. Nanomedicine has been used in ARV formulations to improve delivery and efficacy. More specifically, researchers are exploring the benefit of using nanoparticles to improve ARVs and nanomedicine in HIV eradication strategies such as shock and kill, block and lock, and others. This review will focus on mechanisms of HIV-1 latency and nanomedicine-based approaches to treat HIV.

SERPIN-Derived Small Peptide (SP16) as a Potential Therapeutic Agent against HIV-Induced Inflammatory Molecules and Viral Replication in Cells of the Central Nervous System

Despite the success of combined antiretroviral therapy (cART) increasing the survival rate in human immunodeficiency virus (HIV) patients, low levels of viremia persist in the brain of patients leading to glia (microglia and astrocytes)-induced neuroinflammation and consequently, the reactivation of HIV and neuronal injury. Here, we tested the therapeutic efficacy of a Low-Density Lipoprotein Receptor-Related Protein 1 (LRP-1) agonistic small peptide drug (SP16) in attenuating HIV replication and the secretion of inflammatory molecules in brain reservoirs. SP16 was developed by Serpin Pharma and is derived from the pentapeptide sequence of the serine protease inhibitor alpha-1-antitrypsin (A1AT). The SP16 peptide sequence was subsequently modified to improve the stability, bioavailability, efficacy, and binding to LRP-1; a scavenger regulatory receptor that internalizes ligands to induce anti-viral, anti-inflammatory, and pro-survival signals. Using glial cells infected with HIV, we showed that: (i) SP16 attenuated viral-induced secretion of pro-inflammatory molecules; and (ii) SP16 attenuated viral replication. Using an artificial 3D blood-brain barrier (BBB) system, we showed that: (i) SP16 was transported across the BBB; and (ii) restored the permeability of the BBB compromised by HIV. Mechanistically, we showed that SP16 interaction with LRP-1 and binding lead to: (i) down-regulation in the expression levels of nuclear factor-kappa beta (NF-κB); and (ii) up-regulation in the expression levels of Akt. Using an in vivo mouse model, we showed that SP16 was transported across the BBB after intranasal delivery, while animals infected with EcoHIV undergo a reduction in (i) viral replication and (ii) viral secreted inflammatory molecules, after exposure to SP16 and antiretrovirals. Overall, these studies confirm a therapeutic response of SP16 against HIV-associated inflammatory effects in the brain.

Ionic Liquid Coating-Driven Nanoparticle Delivery to the Brain: Applications for NeuroHIV

Delivering cargo to the central nervous system (CNS) remains a pharmacological challenge. For infectious diseases such as HIV, the CNS acts as a latent reservoir that is inadequately managed by systemic antiretrovirals (ARTs). ARTs thus cannot eradicate HIV, and given CNS infection, patients experience an array of neurological deficits that are collectively referred to as 'neuroHIV'. Herein we report the development of bioinspired ionic liquid-coated nanoparticles (IL-NPs) for in situ hitchhiking on red blood cells (RBCs), which enabled 48% delivery of intravenously infused cargo to the brain. Moreover, the ionic liquid (IL) choline trans-2-hexenoate (CA2HA 1:2) demonstrated preferential accumulation in parenchymal microglia over endothelial cells post-delivery. We further demonstrate the successful loading of abacavir (ABC), an ART that is challenging to encapsulate, into the IL-coated NPs and verify the retention of antiviral efficacy in vitro. IL-NPs were not cytotoxic to primary human peripheral blood mononuclear cells (PBMCs) and the CA2HA 1:2 coating conferred notable anti-viremic capacity on its own. In addition, in vitro cell culture assays showed markedly increased uptake of IL-coated nanoparticles into neuronal cells compared to bare nanoparticles. This work debuts bioinspired ionic liquids as promising nanoparticle coatings to assist CNS biodistribution and has the potential to revolutionize the delivery of cargos (i.e., drugs, viral vectors) through compartmental barriers such as the blood-brain-barrier (BBB), illustrated in the graphical abstract below.

Immune Functions of Astrocytes in Viral Neuroinfections

Neuroinfections of the central nervous system (CNS) can be triggered by various pathogens. Viruses are the most widespread and have the potential to induce long-term neurologic symptoms with potentially lethal outcomes. In addition to directly affecting their host cells and inducing immediate changes in a plethora of cellular processes, viral infections of the CNS also trigger an intense immune response. Regulation of the innate immune response in the CNS depends not only on microglia, which are fundamental immune cells of the CNS, but also on astrocytes. These cells align blood vessels and ventricle cavities, and consequently, they are one of the first cell types to become infected after the virus breaches the CNS. Moreover, astrocytes are increasingly recognized as a potential viral reservoir in the CNS; therefore, the immune response initiated by the presence of intracellular virus particles may have a profound effect on cellular and tissue physiology and morphology. These changes should be addressed in terms of persisting infections because they may contribute to recurring neurologic sequelae. To date, infections of astrocytes with different viruses originating from genetically distinct families, including Flaviviridae, Coronaviridae, Retroviridae, Togaviridae, Paramyxoviridae, Picomaviridae, Rhabdoviridae, and Herpesviridae, have been confirmed. Astrocytes express a plethora of receptors that detect viral particles and trigger signaling cascades, leading to an innate immune response. In this review, we summarize the current knowledge on virus receptors that initiate the release of inflammatory cytokines from astrocytes and depict the involvement of astrocytes in immune functions of the CNS.

HIV Nef Expression Down-modulated GFAP Expression and Altered Glutamate Uptake and Release and Proliferation in Astrocytes

HIV infection of astrocytes leads to restricted gene expression and replication but abundant expression of HIV early genes Tat, Nef and Rev. A great deal of neuroHIV research has so far been focused on Tat protein, its effects on astrocytes, and its roles in neuroHIV. In the current study, we aimed to determine effects of Nef expression on astrocytes and their function. Using transfection or infection of VSVG-pseudotyped HIV viruses, we showed that Nef expression down-modulated glial fibrillary acidic protein (GFAP) expression. We then showed that Nef expression also led to decreased GFAP mRNA expression. The transcriptional regulation was further confirmed using a GFAP promoter-driven reporter gene assay. We performed transcription factor profiling array to compare the expression of transcription factors between Nef-intact and Nef-deficient HIV-infected cells and identified eight transcription factors with expression changes of 1.5-fold or higher: three up-regulated by Nef (Stat1, Stat5, and TFIID), and five down-regulated by Nef (AR, GAS/ISRE, HIF, Sp1, and p53). We then demonstrated that removal of the Sp1 binding sites from the GFAP promoter resulted in a much lower level of the promoter activity and reversal of Nef effects on the GFAP promoter, confirming important roles of Sp1 in the GFAP promoter activity and for Nef-induced GFAP expression. Lastly, we showed that Nef expression led to increased glutamate uptake and decreased glutamate release by astrocytes and increased astrocyte proliferation. Taken together, these results indicate that Nef leads to down-modulation of GFAP expression and alteration of glutamate metabolism in astrocytes, and astrocyte proliferation and could be an important contributor to neuroHIV.

The HIV Restriction Factor Profile in the Brain Is Associated with the Clinical Status and Viral Quantities

HIV-encoded DNA, RNA and proteins persist in the brain despite effective antiretroviral therapy (ART), with undetectable plasma and cerebrospinal fluid viral RNA levels, often in association with neurocognitive impairments. Although the determinants of HIV persistence have garnered attention, the expression and regulation of antiretroviral host restriction factors (RFs) in the brain for HIV and SIV remain unknown. We investigated the transcriptomic profile of antiretroviral RF genes by RNA-sequencing with confirmation by qRT-PCR in the cerebral cortex of people who are uninfected (HIV[-]), those who are HIV-infected without pre-mortem brain disease (HIV[+]), those who are HIV-infected with neurocognitive disorders (HIV[+]/HAND) and those with neurocognitive disorders with encephalitis (HIV[+]/HIVE). We observed significant increases in RF expression in the brains of HIV[+]/HIVE in association with the brain viral load. Machine learning techniques identified MAN1B1 as a key gene that distinguished the HIV[+] group from the HIV[+] groups with HAND. Analyses of SIV-associated RFs in brains from SIV-infected Chinese rhesus macaques with different ART regimens revealed diminished RF expression among ART-exposed SIV-infected animals, although ART interruption resulted in an induced expression of several RF genes including OAS3, RNASEL, MX2 and MAN1B1. Thus, the brain displays a distinct expression profile of RFs that is associated with the neurological status as well as the brain viral burden. Moreover, ART interruption can influence the brain's RF profile, which might contribute to disease outcomes.

HIV infection of non-classical cells in the brain

HIV-associated neurological disorders (HAND) affect up to 50% of people living with HIV (PLWH), even in the era of combination antiretroviral therapy (cART). HIV-DNA can be detected in the cerebral spinal fluid (CSF) of approximately half of aviremic ART-suppressed PLWH and its presence is associated with poorer neurocognitive performance. HIV DNA + and HIV RNA + cells have also been observed in postmortem brain tissue of individuals with sustained cART suppression. In this review, we provide an overview of how HIV invades the brain and HIV infection of resident brain glial cells (astrocytes and microglia). We also discuss the role of resident glial cells in persistent neuroinflammation and HAND in PLWH and their potential contribution to the HIV reservoir. HIV eradication strategies that target persistently infected glia cells will likely be needed to achieve HIV cure.

Dopamine, Immunity, and Disease

The neurotransmitter dopamine is a key factor in central nervous system (CNS) function, regulating many processes including reward, movement, and cognition. Dopamine also regulates critical functions in peripheral organs, such as blood pressure, renal activity, and intestinal motility. Beyond these functions, a growing body of evidence indicates that dopamine is an important immunoregulatory factor. Most types of immune cells express dopamine receptors and other dopaminergic proteins, and many immune cells take up, produce, store, and/or release dopamine, suggesting that dopaminergic immunomodulation is important for immune function. Targeting these pathways could be a promising avenue for the treatment of inflammation and disease, but despite increasing research in this area, data on the specific effects of dopamine on many immune cells and disease processes remain inconsistent and poorly understood. Therefore, this review integrates the current knowledge of the role of dopamine in immune cell function and inflammatory signaling across systems. We also discuss the current understanding of dopaminergic regulation of immune signaling in the CNS and peripheral tissues, highlighting the role of dopaminergic immunomodulation in diseases such as Parkinson's disease, several neuropsychiatric conditions, neurologic human immunodeficiency virus, inflammatory bowel disease, rheumatoid arthritis, and others. Careful consideration is given to the influence of experimental design on results, and we note a number of areas in need of further research. Overall, this review integrates our knowledge of dopaminergic immunology at the cellular, tissue, and disease level and prompts the development of therapeutics and strategies targeted toward ameliorating disease through dopaminergic regulation of immunity. SIGNIFICANCE STATEMENT: Canonically, dopamine is recognized as a neurotransmitter involved in the regulation of movement, cognition, and reward. However, dopamine also acts as an immune modulator in the central nervous system and periphery. This review comprehensively assesses the current knowledge of dopaminergic immunomodulation and the role of dopamine in disease pathogenesis at the cellular and tissue level. This will provide broad access to this information across fields, identify areas in need of further investigation, and drive the development of dopaminergic therapeutic strategies.

Pericyte infection by HIV-1: a fatal attraction

While HIV-1 is primarily an infection of CD4 + T cells, there is an emerging interest towards understanding how infection of other cell types can contribute to HIV-associated comorbidities. For HIV-1 to cross from the blood stream into tissues, the virus must come in direct contact with the vascular endothelium, including pericytes that envelope vascular endothelial cells. Pericytes are multifunctional cells that have been recognized for their essential role in angiogenesis, vessel maintenance, and blood flow rate. Most importantly, recent evidence has shown that pericytes can be a target of HIV-1 infection and support an active stage of the viral life cycle, with latency also suggested by in vitro data. Pericyte infection by HIV-1 has been confirmed in the postmortem human brains and in lungs from SIV-infected macaques. Moreover, pericyte dysfunction has been implicated in a variety of pathologies ranging from ischemic stroke to diabetes, which are common comorbidities among people with HIV-1. In this review, we discuss the role of pericytes during HIV-1 infection and their contribution to the progression of HIV-associated comorbidities.

Nef inhibits HIV transcription and gene expression in astrocytes and HIV transmission from astrocytes to CD4+ T cells

HIV infects astrocytes in a restricted manner but leads to abundant expression of Nef, a major viral factor for HIV replication and disease progression. However, the roles of Nef in HIV gene expression and replication in astrocytes and viral transfer from astrocytes to CD4+ T cells remain largely unclear. In this study, we attempted to address these issues by transfecting human primary astrocytes with HIV molecular clones with intact Nef and without Nef (a nonsense Nef mutant) and comparing gene expression and replication in astrocytes and viral transfer from astrocytes to CD4+ T cells MT4. First, we found that lack of Nef expression led to increased extracellular virus production from astrocytes and intracellular viral protein and RNA expression in astrocytes. Using a HIV LTR-driven luciferase reporter gene assay, we showed that ectopic Nef expression alone inhibited the HIV LTR promoter activity in astrocytes. Consistent with the previously established function of Nef, we showed that the infectivity of HIV derived from astrocytes with Nef expression was significantly higher than that with no Nef expression. Next, we performed the co-culture assay to determine HIV transfer from astrocytes transfected to MT4. We showed that lack of Nef expression led to significant increase in HIV transfer from astrocytes to MT4 using two HIV clones. We also used Nef-null HIV complemented with Nef in trans in the co-culture assay and demonstrated that Nef expression led to significantly decreased HIV transfer from astrocytes to MT4. Taken together, these findings support a negative role of Nef in HIV replication and pathogenesis in astrocytes.

Animal models for studies of HIV-1 brain reservoirs

The HIV-1 often evades a robust antiretroviral-mediated immune response, leading to persistent infection within anatomically privileged sites including the CNS. Continuous low-level infection occurs in the presence of effective antiretroviral therapy (ART) in CD4+ T cells and mononuclear phagocytes (MP; monocytes, macrophages, microglia, and dendritic cells). Within the CNS, productive viral infection is found exclusively in microglia and meningeal, perivascular, and choroidal macrophages. MPs serve as the principal viral CNS reservoir. Animal models have been developed to recapitulate natural human HIV-1 infection. These include nonhuman primates, humanized mice, EcoHIV, and transgenic rodent models. These models have been used to study disease pathobiology, antiretroviral and immune modulatory agents, viral reservoirs, and eradication strategies. However, each of these models are limited to specific component(s) of human disease. Indeed, HIV-1 species specificity must drive therapeutic and cure studies. These have been studied in several model systems reflective of latent infections, specifically in MP (myeloid, monocyte, macrophages, microglia, and histiocyte cell) populations. Therefore, additional small animal models that allow productive viral replication to enable viral carriage into the brain and the virus-susceptible MPs are needed. To this end, this review serves to outline animal models currently available to study myeloid brain reservoirs and highlight areas that are lacking and require future research to more effectively study disease-specific events that could be useful for viral eradication studies both in and outside the CNS.

Subtype C HIV-1 reservoirs throughout the body in ART-suppressed individuals

Subtype B HIV-1 reservoirs have been intensively investigated, but reservoirs in other subtypes and how they respond to antiretroviral therapy (ART) is substantially less established. To characterize subtype C HIV-1 reservoirs, we implemented postmortem frozen, as well as formalin fixed paraffin embedded (FFPE) tissue sampling of central nervous system (CNS) and peripheral tissues. HIV-1 LTR, gag, envelope (env) DNA and RNA was quantified using genomic DNA and RNA extracted from frozen tissues. RNAscope was used to localize subtype C HIV-1 DNA and RNA in FFPE tissue. Despite uniform viral load suppression in our cohort, PCR results showed that subtype C HIV-1 proviral copies vary both in magnitude and tissue distribution, with detection primarily in secondary lymphoid tissues. Interestingly, the appendix harbored proviruses in all subjects. Unlike subtype B, subtype C provirus was rarely detectable in the CNS, and there was no detectable HIV-1 RNA. HIV-1 RNA was detected in peripheral lymphoid tissues of 6 out of 8 ART-suppressed cases. In addition to active HIV-1 expression in lymphoid tissues, RNAscope revealed HIV RNA detection in CD4-expressing cells in the appendix, suggesting that this tissue was a previously unreported potential treatment-resistant reservoir for subtype C HIV-1.

Effect of benzo(a)pyrene on oxidative stress and inflammatory mediators in astrocytes and HIV-infected macrophages

BACKGROUND

Benzo(a)pyrene (BaP), an important polycyclic aromatic hydrocarbons (PAH) component of cigarette/tobacco smoking, is known to cause adverse health effects and is responsible for various life-threatening conditions including cancer. However, it is not yet clear whether BaP contributes to the macrophage- and astrocyte-mediated inflammatory response.

METHODS

We examined the acute (up to 72 h) effects of BaP on the expression of antioxidant enzymes (AOEs), cytokines/chemokines, and cytochromes P450 (CYP) enzymes in astrocytic cell lines, SVGA, and chronically HIV-infected U1 macrophage. The treated cells were examined for mRNA, protein levels of CYPs, AOEs superoxide dismutase-1 (SOD1) and catalase (CAT), cytokines/chemokines, using Western blot, multiplex ELISA, and reactive oxygen species (ROS) by flow cytometry analysis.

RESULTS

Upon acute exposure, BaP (1 μM) showed a significant increase in the mRNA levels of CYPs (CYP1A1 and CYP1B1), and pro-inflammatory cytokine IL-1β in SVGA cells following BaP for 24, 48, and 72h. In addition, we observed a significant increase in the mRNA levels of SOD1 and CAT at 24h of BaP treatment. In contrast, BaP did not exert any change in the protein expression of AOEs and CYP enzymes. In U1 cells, however, we noticed an interesting increase in the levels of MCP-1 as well as a modest increase in TNFα, IL-8 and IL-1β levels observed at 72 h of BaP treatment but could not reach to statistically significant level.

CONCLUSIONS

Overall, these results suggest that BaP contributes in part to macrophage and astrocyte-mediated neuroinflammation by mainly inducing IL-1β and MCP-1 production, which is likely to occur with the involvement of CYP and/or oxidative stress pathways.

Intact HIV Proviruses Persist in the Brain Despite Viral Suppression with ART

OBJECTIVE

Human immunodeficiency virus (HIV) persistence in blood and tissue reservoirs, including the brain, is a major barrier to HIV cure and possible cause of comorbid disease. However, the size and replication competent nature of the central nervous system (CNS) reservoir is unclear. Here, we used the intact proviral DNA assay (IPDA) to provide the first quantitative assessment of the intact and defective HIV reservoir in the brain of people with HIV (PWH).

METHODS

Total, intact, and defective HIV proviruses were measured in autopsy frontal lobe tissue from viremic (n = 18) or virologically suppressed (n = 12) PWH. Total or intact/defective proviruses were measured by detection of HIV pol or the IPDA, respectively, through use of droplet digital polymerase chain reaction (ddPCR). HIV-seronegative individuals were included as controls (n = 6).

RESULTS

Total HIV DNA was present at similar levels in brain tissues from untreated viremic and antiretroviral (ART)-suppressed individuals (median = 22.3 vs 26.2 HIV pol copies/10⁶ cells), reflecting a stable CNS reservoir of HIV that persists despite therapy. Furthermore, 8 of 10 viremic and 6 of 9 virally suppressed PWH also harbored intact proviruses in the CNS (4.63 vs 12.7 intact copies/10⁶ cells). Viral reservoirs in CNS and matched lymphoid tissue were similar in the composition of intact and/or defective proviruses, albeit at lower levels in the brain. Importantly, CNS resident CD68+ myeloid cells in virally suppressed individuals harbored HIV DNA, directly showing the presence of a CNS resident HIV reservoir.

INTERPRETATION

Our results demonstrate the first evidence for an intact, potentially replication competent HIV reservoir in the CNS of virally suppressed PWH. ANN NEUROL 2022;92:532-544.

Co-Infection and Cancer: Host–Pathogen Interaction between Dendritic Cells and HIV-1, HTLV-1, and Other Oncogenic Viruses

Dendritic cells (DCs) function as a link between innate and adaptive immune responses. Retroviruses HIV-1 and HTLV-1 modulate DCs to their advantage and utilize them to propagate infection. Coinfection of HTLV-1 and HIV-1 has implications for cancer malignancies. Both viruses initially infect DCs and propagate the infection to CD4+ T cells through cell-to-cell transmission using mechanisms including the formation of virologic synapses, viral biofilms, and conduits. These retroviruses are both neurotrophic with neurovirulence determinants. The neuropathogenesis of HIV-1 and HTLV-1 results in neurodegenerative diseases such as HIV-associated neurocognitive disorders (HAND) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Infected DCs are known to traffic to the brain (CNS) and periphery (PNS, lymphatics) to induce neurodegeneration in HAND and HAM/TSP patients. Elevated levels of neuroinflammation have been correlated with cognitive decline and impairment of motor control performance. Current vaccinations and therapeutics for HIV-1 and HTLV-1 are assessed and can be applied to patients with HIV-1-associated cancers and adult T cell leukemia/lymphoma (ATL). These diseases caused by co-infections can result in both neurodegeneration and cancer. There are associations with cancer malignancies and HIV-1 and HTLV-1 as well as other human oncogenic viruses (EBV, HBV, HCV, HDV, and HPV). This review contains current knowledge on DC sensing of HIV-1 and HTLV-1 including DC-SIGN, Tat, Tax, and current viral therapies. An overview of DC interaction with oncogenic viruses including EBV, Hepatitis viruses, and HPV is also provided. Vaccines and therapeutics targeting host–pathogen interactions can provide a solution to co-infections, neurodegeneration, and cancer.