Microglial Cells: The Main HIV-1 Reservoir in the Brain

Investigating how HIV-1 antiretrovirals differentially behave as substrates and inhibitors of P-glycoprotein via molecular dynamics simulations

HIV-1 can rapidly infect the brain upon initial infection, establishing latent reservoirs that induce neuronal damage and/or death, resulting in HIV-Associated Neurocognitive Disorder. Though anti-HIV-1 antiretrovirals (ARVs) suppress viral load, the blood-brain barrier limits drug access to the brain, largely because of highly expressed efflux proteins like P-glycoprotein (P-gp). While no FDA-approved P-gp inhibitor currently exists, HIV-1 protease inhibitors show promise as partial P-gp inhibitors, potentially enhancing drug delivery to the brain. Herein, we employed docking and molecular dynamics simulations to elucidate key differences in P-gp's interactions with several antiretrovirals, including protease inhibitors, with known inhibitory or substrate-like behaviors towards P-gp. Our results led us to hypothesize new mechanistic details of small-molecule efflux by and inhibition of P-gp, where the "Lower Pocket" in P-gp's transmembrane domain serves as the primary initial site for small-molecule binding. Subsequently, this pocket merges with the more traditionally studied drug binding site-the "Upper Pocket"-thus funneling small-molecule drugs, such as ARVs, towards the Upper Pocket for efflux. Furthermore, our results reinforce the understanding that both binding energetics and changes in protein dynamics are crucial in discerning small molecules as non-substrates, substrates, or inhibitors of P-gp. Our findings indicate that interactions between P-gp and inhibitory ARVs induce bridging of transmembrane domain helices, impeding P-gp conformational changes and contributing to the inhibitory behavior of these ARVs. Overall, insights gained in this study could serve to guide the design of future P-gp-targeting therapeutics for a wide range of pathological conditions and diseases, including HIV-1.

Gene expression and chromatin conformation of microglia in virally suppressed people with HIV

The presence of HIV in sequestered reservoirs is a central impediment to a functional cure, allowing HIV to persist despite life-long antiretroviral therapy (ART), and driving a variety of comorbid conditions. Our understanding of the latent HIV reservoir in the central nervous system is incomplete, because of difficulties in accessing human central nervous system tissues. Microglia contribute to HIV reservoirs, but the molecular phenotype of HIV-infected microglia is poorly understood. We leveraged the unique "Last Gift" rapid autopsy program, in which people with HIV are closely followed until days or even hours before death. Microglial populations were heterogeneous regarding their gene expression profiles but showed similar chromatin accessibility landscapes. Despite ART, we detected occasional microglia containing cell-associated HIV RNA and HIV DNA integrated into open regions of the host's genome (∼0.005%). Microglia with detectable HIV RNA showed an inflammatory phenotype. These results demonstrate a distinct myeloid cell reservoir in the brains of people with HIV despite suppressive ART. Strategies for curing HIV and neurocognitive impairment will need to consider the myeloid compartment to be successful.

HIV-associated neurocognitive disorder: key implications of the microbiota-gut-brain axis

HIV-associated neurocognitive disorder (HAND) is now recognized to be relatively common in people living with HIV (PLWH), and remains a common cause of cognitive impairment. Unfortunately, the fundamental pathogenic processes underlying this specific outcome of HIV infection have not as yet been fully elucidated. With increased interest in research related to the microbiota-gut-brain axis, the gut-brain axis has been shown to play critical roles in regulating central nervous system disorders such as Alzheimer's disease and Parkinson's disease. PLWH are characterized by a particular affliction, referred to as gut-associated dysbiosis syndrome, which provokes an alteration in microbial composition and diversity, and of their associated metabolite composition within the gut. Interestingly, the gut microbiota has also been recognized as a key element, which both positively and negatively influences human brain health, including the functioning and development of the central nervous system (CNS). In this review, based on published evidence, we critically discuss the relevant interactions between the microbiota-gut-brain axis and the pathogenesis of HAND in the context of HIV infection. It is likely that HAND manifestation in PLWH mainly results from (i) gut-associated dysbiosis syndrome and a leaky gut on the one hand and (ii) inflammation on the other hand. In other words, the preceding features of HIV infection negatively alter the composition of the gut microbiota (microbes and their associated metabolites) and promote proinflammatory immune responses which singularly or in tandem damage neurons and/or induce inadequate neuronal signaling. Thus, HAND is fairly prevalent in PLWH. This work aims to demonstrate that in the quest to prevent and possibly treat HAND, the gut microbiota may ultimately represent a therapeutically targetable "host factor."

Short-term exposure to HIV Tat induces glial activation and changes in perineuronal nets

Despite widespread use of combination antiretroviral therapy (cART), there remains a subset of individuals who display cognitive impairment broadly known as HIV-associated neurocognitive disorder (HAND). Interestingly, HIV-infected cells continuously release the HIV-1 protein Tat even in the presence of cART. Persistent exposure to Tat is proposed to increase both neuroinflammation and neurotoxicity. In vitro evidence shows that matrix metalloproteinases (MMPs) are among the neuroinflammatory molecules induced by Tat, which are known to disrupt specialized neuronal extracellular matrix structures called perineuronal nets (PNNs). PNNs predominantly surround parvalbumin interneurons and help to buffer these cells from oxidant stress and to independently increase their excitability. In order to better understand the link between short-term exposure to Tat, neuroinflammation, and PNNs, we explored the direct effects of Tat on glial cells and neurons. Herein, we report that in mixed glial cultures, Tat directly increases the expression of proinflammatory molecules, including MMP-9. Moreover, direct injection of Tat protein into mouse hippocampus increases the expression of astrocyte and microglia markers as well as MMP-9. The number of PNNs is decreased following Tat exposure, followed later by decreased numbers of hippocampal parvalbumin-expressing neurons. In older mice, Tat induced significant increases in the gene expression of proinflammatory molecules including markers of gliosis, MMPs and complement system proteins. Taken together, these data support a direct effect of Tat on glial-derived MMP expression subsequently affecting PNNs and neuronal health, with older mice more susceptible to Tat-induced inflammation.

Harnessing nanomedicine for modulating microglial states in the central nervous system disorders: Challenges and opportunities

Microglia are essential for maintaining homeostasis and responding to pathological events in the central nervous system (CNS). Their dynamic and multidimensional states in different environments are pivotal factors in various CNS disorders. However, therapeutic modulation of microglial states is challenging due to the intricate balance these cells maintain in the CNS environment and the blood-brain barrier's restriction of drug delivery. Nanomedicine presents a promising avenue for addressing these challenges, offering a method for the targeted and efficient modulation of microglial states. This review covers the challenges faced in microglial therapeutic modulation and potential use of nanoparticle-based drug delivery systems. We provide an in-depth examination of nanoparticle applications for modulating microglial states in a range of CNS disorders, encompassing neurodegenerative and autoimmune diseases, infections, traumatic injuries, stroke, tumors, chronic pain, and psychiatric conditions. This review highlights the recent advancements and future prospects in nanomedicine for microglial modulation, paving the way for future research and clinical applications of therapeutic interventions in CNS disorders.

Caffeine upregulates SIRT3 expression to ameliorate astrocytes-mediated HIV-1 Tat neurotoxicity via suppression of EGR1 signaling pathway

Caffeine is one of the most popular consumed psychostimulants that mitigates several neurodegenerative diseases. Nevertheless, the roles and molecular mechanisms of caffeine in HIV-associated neurocognitive disorders (HAND) remain largely unclear. Transactivator of transcription (Tat) is a major contributor to the neuropathogenesis of HAND in the central nervous system. In the present study, we determined that caffeine (100 µM) treatment significantly ameliorated Tat-induced decreased astrocytic viability, oxidative stress, inflammatory response and excessive glutamate and ATP release, thereby protecting neurons from apoptosis. Subsequently, SIRT3 was demonstrated to display neuroprotective effects against Tat during caffeine treatment. In addition, Tat downregulated SIRT3 expression via activation of EGR1 signaling, which was reversed by caffeine treatment in astrocytes. Overexpression of EGR1 entirely abolished the neuroprotective effects of caffeine against Tat. Furthermore, counteracting Tat or caffeine-induced differential expression of SIRT3 abrogated the neuroprotection of caffeine against Tat-triggered astrocytic dysfunction and neuronal apoptosis. Taken together, our study establishes that caffeine ameliorates astrocytes-mediated Tat neurotoxicity by targeting EGR1/SIRT3 signaling pathway. Our findings highlight the beneficial effects of caffeine on Tat-induced astrocytic dysfunction and neuronal death and propose that caffeine might be a novel therapeutic drug for relief of HAND.

Reconstitution of human microglia and resident T cells in the brain of humanized DRAGA mice

Humanized mouse models are valuable tools for investigating the human immune system in response to infection and injury. We have previously described the human immune system (HIS)-DRAGA mice (HLA-A2.HLA-DR4.Rag1KO.IL-2RgKO.NOD) generated by infusion of Human Leukocyte Antigen (HLA)-matched, human hematopoietic stem cells from umbilical cord blood. By reconstituting human cells, the HIS-DRAGA mouse model has been utilized as a "surrogate in vivo human model" for infectious diseases such as Human Immunodeficiency Virus (HIV), Influenza, Coronavirus Disease 2019 (COVID-19), scrub typhus, and malaria. This humanized mouse model bypasses ethical concerns about the use of fetal tissues for the humanization of laboratory animals. Here in, we demonstrate the presence of human microglia and T cells in the brain of HIS-DRAGA mice. Microglia are brain-resident macrophages that play pivotal roles against pathogens and cerebral damage, whereas the brain-resident T cells provide surveillance and defense against infections. Our findings suggest that the HIS-DRAGA mouse model offers unique advantages for studying the functions of human microglia and T cells in the brain during infections, degenerative disorders, tumors, and trauma, as well as for testing therapeutics in these pathological conditions.

The HIV-1 Transcriptional Program: From Initiation to Elongation Control

A large body of work in the last four decades has revealed the key pillars of HIV-1 transcription control at the initiation and elongation steps. Here, I provide a recount of this collective knowledge starting with the genomic elements (DNA and nascent TAR RNA stem-loop) and transcription factors (cellular and the viral transactivator Tat), and later transitioning to the assembly and regulation of transcription initiation and elongation complexes, and the role of chromatin structure. Compelling evidence support a core HIV-1 transcriptional program regulated by the sequential and concerted action of cellular transcription factors and Tat to promote initiation and sustain elongation, highlighting the efficiency of a small virus to take over its host to produce the high levels of transcription required for viral replication. I summarize new advances including the use of CRISPR-Cas9, genetic tools for acute factor depletion, and imaging to study transcriptional dynamics, bursting and the progression through the multiple phases of the transcriptional cycle. Finally, I describe current challenges to future major advances and discuss areas that deserve more attention to both bolster our basic knowledge of the core HIV-1 transcriptional program and open up new therapeutic opportunities.

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.

Suppression of HIV-TAT and cocaine-induced neurotoxicity and inflammation by cell penetrable itaconate esters

HIV-associated neurological disorder (HAND) is a serious complication of HIV infection marked by neurotoxicity induced by viral proteins like Tat. Substance abuse exacerbates neurocognitive impairment in people living with HIV. There is an urgent need for therapeutic strategies to combat HAND comorbid with Cocaine Use Disorder (CUD). Our analysis of HIV and cocaine-induced transcriptomes in primary cortical cultures revealed significant overexpression of the macrophage-specific gene aconitate decarboxylase 1 (Acod1). The ACOD1 protein converts the tricarboxylic acid intermediate cis-aconitate into itaconate during the activation of inflammation. Itaconate then facilitates cytokine production and activates anti-inflammatory transcription factors, shielding macrophages from infection-induced cell death. However, the immunometabolic function of itaconate was unexplored in HIV and cocaine-exposed microglia. We assessed the potential of 4-octyl-itaconate (4OI), a cell-penetrable ester form of itaconate known for its anti-inflammatory properties. When primary cortical cultures exposed to Tat and cocaine were treated with 4OI, microglial cell number increased and the morphological altercations induced by Tat and cocaine were reversed. Microglial cells also appeared more ramified, resembling the quiescent microglia. 4OI treatment inhibited secretion of the proinflammatory cytokines IL-1α, IL-1β, IL-6, and MIP1-α induced by Tat and cocaine. Transcriptome profiling determined that Nrf2 target genes were significantly activated in Tat and 4OI treated cultures relative to Tat alone. Further, genes associated with cytoskeleton dynamics in inflammatory microglia were downregulated by 4OI treatment. Together, the results strongly suggest 4-octyl-itaconate holds promise as a potential candidate for therapeutic development to treat HAND coupled with CUD comorbidities.

Dopamine-driven Increase in IL-1β in Myeloid Cells is Mediated by Differential Dopamine Receptor Expression and Exacerbated by HIV

The catecholamine neurotransmitter dopamine is classically known for regulation of central nervous system (CNS) functions such as reward, movement, and cognition. Increasing evidence also indicates that dopamine regulates critical functions in peripheral organs and is an important immunoregulatory factor. We have previously shown that dopamine increases NF-κB activity, inflammasome activation, and the production of inflammatory cytokines such as IL-1β in human macrophages. As myeloid lineage cells are central to the initiation and resolution of acute inflammatory responses, dopamine-mediated dysregulation of these functions could both impair the innate immune response and exacerbate chronic inflammation. However, the exact pathways by which dopamine drives myeloid inflammation are not well defined, and studies in both rodent and human systems indicate that dopamine can impact the production of inflammatory mediators through both D1-like dopamine receptors (DRD1, DRD5) and D2-like dopamine receptors (DRD2, DRD3, and DRD4). Therefore, we hypothesized that dopamine-mediated production of IL-1β in myeloid cells is regulated by the ratio of different dopamine receptors that are activated. Our data in primary human monocyte-derived macrophages (hMDM) indicate that DRD1 expression is necessary for dopamine-mediated increases in IL-1β, and that changes in the expression of DRD2 and other dopamine receptors can alter the magnitude of the dopamine-mediated increase in IL-1β. Mature hMDM have a high D1-like to D2-like receptor ratio, which is different relative to monocytes and peripheral blood mononuclear cells (PBMCs). We further confirm in human microglia cell lines that a high ratio of D1-like to D2-like receptors promotes dopamine-induced increases in IL-1β gene and protein expression using pharmacological inhibition or overexpression of dopamine receptors. RNA-sequencing of dopamine-treated microglia shows that genes encoding functions in IL-1β signaling pathways, microglia activation, and neurotransmission increased with dopamine treatment. Finally, using HIV as an example of a chronic inflammatory disease that is substantively worsened by comorbid substance use disorders (SUDs) that impact dopaminergic signaling, we show increased effects of dopamine on inflammasome activation and IL-1β in the presence of HIV in both human macrophages and microglia. These data suggest that use of addictive substances and dopamine-modulating therapeutics could dysregulate the innate inflammatory response and exacerbate chronic neuroimmunological conditions like HIV. Thus, a detailed understanding of dopamine-mediated changes in inflammation, in particular pathways regulating IL-1β, will be critical to effectively tailor medication regimens.

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).

Glutathione in HIV-Associated Neurocognitive Disorders

A large portion of patients with Human Immunodeficiency Virus (HIV) have neurologic sequelae. Those with better-controlled HIV via antiretroviral therapies generally have less severe neurologic symptoms. However, for many patients, antiretrovirals do not adequately resolve symptoms. Since much of the pathogenesis of HIV/AIDS (Autoimmune Deficiency Syndrome) involves oxidative stress either directly, through viral interaction, or indirectly, through inflammatory mechanisms, we have reviewed relevant trials of glutathione supplementation in each of the HIV-associated neurocognitive diseases and have found disease-specific results. For diseases for which trials have not been completed, predicted responses to glutathione supplementation are made based on relevant mechanisms seen in the literature. It is not sufficient to conclude that all HIV-associated neurocognitive disorders (HAND) will benefit from the antioxidant effects of glutathione supplementation. The potential effects of glutathione supplementation in patients with HAND are likely to differ based on the specific HIV-associated neurocognitive disease.

Non-Coding RNAs in HIV Infection, NeuroHIV, and Related Comorbidities

NeuroHIV affects approximately 30-60% of people living with HIV-1 (PLWH) and is characterized by varying degrees of cognitive impairments, presenting a multifaceted challenge, the underlying cause of which is chronic, low-level neuroinflammation. Such smoldering neuroinflammation is likely an outcome of lifelong reliance on antiretrovirals coupled with residual virus replication in the brains of PLWH. Despite advancements in antiretroviral therapeutics, our understanding of the molecular mechanism(s) driving inflammatory processes in the brain remains limited. Recent times have seen the emergence of non-coding RNAs (ncRNAs) as critical regulators of gene expression, underlying the neuroinflammatory processes in HIV infection, NeuroHIV, and their associated comorbidities. This review explores the role of various classes of ncRNAs and their regulatory functions implicated in HIV infection, neuropathogenesis, and related conditions. The dysregulated expression of ncRNAs is known to exacerbate the neuroinflammatory responses, thus contributing to neurocognitive impairments in PLWH. This review also discusses the diagnostic and therapeutic potential of ncRNAs in HIV infection and its comorbidities, suggesting their utility as non-invasive biomarkers and targets for modulating neuroinflammatory pathways. Understanding these regulatory roles could pave the way for novel diagnostic strategies and therapeutic interventions in the context of HIV and its comorbidities.

Effects of Antiretroviral Treatment on Central and Peripheral Immune Response in Mice with EcoHIV Infection

HIV infection is an ongoing global health issue, despite increased access to antiretroviral therapy (ART). People living with HIV (PLWH) who are virally suppressed through ART still experience negative health outcomes, including neurocognitive impairment. It is increasingly evident that ART may act independently or in combination with HIV infection to alter the immune state, though this is difficult to disentangle in the clinical population. Thus, these experiments used multiplexed chemokine/cytokine arrays to assess peripheral (plasma) and brain (nucleus accumbens; NAc) expression of immune targets in the presence and absence of ART treatment in the EcoHIV mouse model. The findings identify the effects of EcoHIV infection and of treatment with bictegravir (B), emtricitabine (F), and tenofovir alafenamide (TAF) on the expression of numerous immune targets. In the NAc, this included EcoHIV-induced increases in IL-1α and IL-13 expression and B/F/TAF-induced reductions in KC/CXCL1. In the periphery, EcoHIV suppressed IL-6 and LIF expression, while B/F/TAF reduced IL-12p40 expression. In the absence of ART, IBA-1 expression was negatively correlated with CX3CL1 expression in the NAc of EcoHIV-infected mice. These findings identify distinct effects of ART and EcoHIV infection on peripheral and central immune factors and emphasize the need to consider ART effects on neural and immune outcomes.

Characterization of HIV variants from paired Cerebrospinal fluid and Plasma samples in primary microglia and CD4+ T-cells

Despite antiretroviral therapy (ART), HIV persistence in the central nervous system (CNS) continues to cause a range of cognitive impairments in people living with HIV (PLWH). Upon disease progression, transmigrating CCR5-using T-cell tropic viruses are hypothesized to evolve into macrophage-tropic viruses in the CNS that can efficiently infect low CD4-expressing cells, such as microglia. We examined HIV-1 RNA concentration, co-receptor usage, and CSF compartmentalization in paired CSF and blood samples from 19 adults not on treatment. Full-length envelope CSF- and plasma-derived reporter viruses were generated from 3 subjects and phenotypically characterized in human primary CD4+ T-cells and primary microglia. Median HIV RNA levels were higher in plasma than in CSF (5.01 vs. 4.12 log10 cp/mL; p = 0.004), and coreceptor usage was mostly concordant for CCR5 across the paired samples (n = 17). Genetically compartmentalized CSF viral populations were detected in 2 subjects, one with and one without neurological symptoms. All viral clones could replicate in T-cells (R5 T cell-tropic). In addition, 3 CSF and 1 plasma patient-derived viral clones also had the capacity to replicate in microglia/macrophages and, therefore have an intermediate macrophage tropic phenotype. Overall, with this study, we demonstrate that in a subset of PLWH, plasma-derived viruses undergo genetic and phenotypic evolution within the CNS, indicating viral infection and replication in CNS cells. It remains to be studied whether the intermediate macrophage-tropic phenotype observed in primary microglia represents a midpoint in the evolution towards a macrophage-tropic phenotype that can efficiently replicate in microglial cells and propagate viral infection in the CNS.

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

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

What's in a cure: designing a broad-spectrum HIV gene therapy

PURPOSE OF REVIEW

The leading gene editing strategy for a human immunodeficiency virus type 1 (HIV-1) cure involves the delivery of SaCas9 and two guide RNAs (gRNAs) in an adeno-associated viral (AAV) vector. As a dual-component system, CRISPR is targeted to a genetic locus through the choice of a Cas effector and gRNA protospacer design pair. As CRISPR research has expanded in recent years, these components have been investigated for utilization in cure strategies, which will be discussed in this article.

RECENT FINDINGS

Type II SpCas9 and SaCas9 have been the leading Cas effectors across gene editing therapeutics to date. Additionally, extensive research has expanded the potential to multiplex gRNAs and target them effectively to the highly genetically diverse HIV-1 provirus. More recently, the Type V family of Cas12 effectors opens a new opportunity to use a smaller Cas protein for packaging into an AAV vector with multiplexed gRNAs.

SUMMARY

In understanding the individual components of a CRISPR/Cas therapeutic cure for HIV-1, it is important to know that the currently used strategies can be improved upon. Future areas will include alternative smaller Cas effectors, multiplexed gRNAs designs, and/or alternative delivery modalities.

Neuroinflammation generated by HIV-infected microglia promotes dysfunction and death of neurons in human brain organoids

Despite the success of combination antiretroviral therapy (ART) for individuals living with HIV, mild forms of HIV-associated neurocognitive disorder (HAND) continue to occur. Brain microglia form the principal target for HIV infection in the brain. It remains unknown how infection of these cells leads to neuroinflammation, neuronal dysfunction, and/or death observed in HAND. Utilizing two different inducible pluripotent stem cell-derived brain organoid models (cerebral and choroid plexus [ChP] organoids) containing microglia, we investigated the pathogenic changes associated with HIV infection. Infection of microglia was associated with a sharp increase in CCL2 and CXCL10 chemokine gene expression and the activation of many type I interferon stimulated genes (MX1, ISG15, ISG20, IFI27, IFITM3 and others). Production of the proinflammatory chemokines persisted at low levels after treatment of the cell cultures with ART, consistent with the persistence of mild HAND following clinical introduction of ART. Expression of multiple members of the S100 family of inflammatory genes sharply increased following HIV infection of microglia measured by single-cell RNA-seq. However, S100 gene expression was not limited to microglia but was also detected more broadly in uninfected stromal cells, mature and immature ChP cells, neural progenitor cells and importantly in bystander neurons suggesting propagation of the inflammatory response to bystander cells. Neurotransmitter transporter expression declined in uninfected neurons, accompanied by increased expression of genes promoting cellular senescence and cell death. Together, these studies underscore how an inflammatory response generated in HIV-infected microglia is propagated to multiple uninfected bystander cells ultimately resulting in the dysfunction and death of bystander neurons.

CNS Viral Infections-What to Consider for Improving Drug Treatment: A Plea for Using Mathematical Modeling Approaches

Neurotropic viruses may cause meningitis, myelitis, encephalitis, or meningoencephalitis. These inflammatory conditions of the central nervous system (CNS) may have serious and devastating consequences if not treated adequately. In this review, we first summarize how neurotropic viruses can enter the CNS by (1) crossing the blood-brain barrier or blood-cerebrospinal fluid barrier; (2) invading the nose via the olfactory route; or (3) invading the peripheral nervous system. Neurotropic viruses may then enter the intracellular space of brain cells via endocytosis and/or membrane fusion. Antiviral drugs are currently used for different viral CNS infections, even though their use and dosing regimens within the CNS, with the exception of acyclovir, are minimally supported by clinical evidence. We therefore provide considerations to optimize drug treatment(s) for these neurotropic viruses. Antiviral drugs should cross the blood-brain barrier/blood cerebrospinal fluid barrier and pass the brain cellular membrane to inhibit these viruses inside the brain cells. Some antiviral drugs may also require intracellular conversion into their active metabolite(s). This illustrates the need to better understand these mechanisms because these processes dictate drug exposure within the CNS that ultimately determine the success of antiviral drugs for CNS infections. Finally, we discuss mathematical model-based approaches for optimizing antiviral treatments. Thereby emphasizing the potential of CNS physiologically based pharmacokinetic models because direct measurement of brain intracellular exposure in living humans faces ethical restrictions. Existing physiologically based pharmacokinetic models combined with in vitro pharmacokinetic/pharmacodynamic information can be used to predict drug exposure and evaluate efficacy of antiviral drugs within the CNS, to ultimately optimize the treatments of CNS viral infections.

Darunavir Nanoformulation Suppresses HIV Pathogenesis in Macrophages and Improves Drug Delivery to the Brain in Mice

Although antiretroviral therapy (ART) can suppress peripheral HIV, patients still suffer from neuroHIV due to insufficient levels of ART drugs in the brain. Hence, this study focuses on developing a poly lactic-co-glycolic acid (PLGA) nanoparticle-based ART drug delivery system for darunavir (DRV) using an intranasal route that can overcome the limitation of drug metabolic stability and blood-brain barrier (BBB) permeability. The physicochemical properties of PLGA-DRV were characterized. The results indicated that PLGA-DRV formulation inhibits HIV replication in U1 macrophages directly and in the presence of the BBB without inducing cytotoxicity. However, the PLGA-DRV did not inhibit HIV replication more than DRV alone. Notably, the total antioxidant capacity remained unchanged upon treatment with both DRV or PLGA-DRV in U1 cells. Compared to DRV alone, PLGA-DRV further decreased reactive oxygen species, suggesting a decrease in oxidative stress by the formulation. Oxidative stress is generally increased by HIV infection, leading to increased inflammation. Although the PLGA-DRV formulation did not further reduce the inflammatory response, the formulation did not provoke an inflammatory response in HIV-infected U1 macrophages. As expected, in vitro experiments showed higher DRV permeability by PLGA-DRV than DRV alone to U1 macrophages. Importantly, in vivo experiments, especially using intranasal administration of PLGA-DRV in wild-type mice, demonstrated a significant increase in the brain-to-plasma ratio of DRV compared to the free DRV. Overall, findings from this study attest to the potential of the PLGA-DRV nanoformulation in reducing HIV pathogenesis in macrophages and enhancing drug delivery to the brain, offering a promising avenue for treating HIV-related neurological disorders.

Effects of antiretroviral treatment on central and peripheral immune response in mice with EcoHIV infection

HIV infection is an ongoing global health issue despite increased access to antiretroviral therapy (ART). People living with HIV (PLWH) who are virally suppressed through ART still experience negative health outcomes, including neurocognitive impairment. It is increasingly evident that ART may act independently or in combination with HIV infection to alter immune state, though this is difficult to disentangle in the clinical population. Thus, these experiments used multiplexed chemokine/cytokine arrays to assess peripheral (plasma) and brain (nucleus accumbens; NAc) expression of immune targets in the presence and absence of ART treatment in the EcoHIV mouse model. The findings identify effects of EcoHIV infection and of treatment with bictegravir (B), emtricitabine (F) and tenofovir alafenamide (TAF) on expression of numerous immune targets. In the NAc, this included EcoHIV-induced increases in IL-1α and IL-13 expression and B/F/TAF-induced reductions in KC/CXCL1. In the periphery, EcoHIV suppressed IL-6 and LIF expression, while B/F/TAF reduced IL-12p40 expression. In absence of ART, IBA-1 expression was negatively correlated with CX3CL1 expression in the NAc of EcoHIV-infected mice. These findings identify distinct effects of ART and EcoHIV infection on peripheral and central immune factors and emphasize the need to consider ART effects on neural and immune outcomes.

The cell biology of HIV-1 latency and rebound

Transcriptionally latent forms of replication-competent proviruses, present primarily in a small subset of memory CD4+ T cells, pose the primary barrier to a cure for HIV-1 infection because they are the source of the viral rebound that almost inevitably follows the interruption of antiretroviral therapy. Over the last 30 years, many of the factors essential for initiating HIV-1 transcription have been identified in studies performed using transformed cell lines, such as the Jurkat T-cell model. However, as highlighted in this review, several poorly understood mechanisms still need to be elucidated, including the molecular basis for promoter-proximal pausing of the transcribing complex and the detailed mechanism of the delivery of P-TEFb from 7SK snRNP. Furthermore, the central paradox of HIV-1 transcription remains unsolved: how are the initial rounds of transcription achieved in the absence of Tat? A critical limitation of the transformed cell models is that they do not recapitulate the transitions between active effector cells and quiescent memory T cells. Therefore, investigation of the molecular mechanisms of HIV-1 latency reversal and LRA efficacy in a proper physiological context requires the utilization of primary cell models. Recent mechanistic studies of HIV-1 transcription using latently infected cells recovered from donors and ex vivo cellular models of viral latency have demonstrated that the primary blocks to HIV-1 transcription in memory CD4+ T cells are restrictive epigenetic features at the proviral promoter, the cytoplasmic sequestration of key transcription initiation factors such as NFAT and NF-κB, and the vanishingly low expression of the cellular transcription elongation factor P-TEFb. One of the foremost schemes to eliminate the residual reservoir is to deliberately reactivate latent HIV-1 proviruses to enable clearance of persisting latently infected cells-the "Shock and Kill" strategy. For "Shock and Kill" to become efficient, effective, non-toxic latency-reversing agents (LRAs) must be discovered. Since multiple restrictions limit viral reactivation in primary cells, understanding the T-cell signaling mechanisms that are essential for stimulating P-TEFb biogenesis, initiation factor activation, and reversing the proviral epigenetic restrictions have become a prerequisite for the development of more effective LRAs.

Microglia and macrophages alterations in the CNS during acute SIV infection: a single-cell analysis in rhesus macaques

Human Immunodeficiency Virus (HIV) is widely acknowledged for its profound impact on the immune system. Although HIV primarily affects peripheral CD4 T cells, its influence on the central nervous system (CNS) cannot be overlooked. Within the brain, microglia and CNS-associated macrophages (CAMs) serve as the primary targets for HIV, as well as for the simian immunodeficiency virus (SIV) in nonhuman primates. This infection can lead to neurological effects and the establishment of a viral reservoir. Given the gaps in our understanding of how these cells respond in vivo to acute CNS infection, we conducted single-cell RNA sequencing (scRNA-seq) on myeloid cells from the brains of three rhesus macaques 12-days after SIV infection, along with three uninfected controls. Our analysis revealed six distinct microglial clusters including homeostatic microglia, preactivated microglia, and activated microglia expressing high levels of inflammatory and disease-related molecules. In response to acute SIV infection, the population of homeostatic and preactivated microglia decreased, while the activated and disease-related microglia increased. All microglial clusters exhibited upregulation of MHC class I molecules and interferon-related genes, indicating their crucial roles in defending against SIV during the acute phase. All microglia clusters also upregulated genes linked to cellular senescence. Additionally, we identified two distinct CAM populations: CD14lowCD16hi and CD14hiCD16low CAMs. Interestingly, during acute SIV infection, the dominant CAM population changed to one with an inflammatory phenotype. Notably, specific upregulated genes within one microglia and one macrophage cluster were associated with neurodegenerative pathways, suggesting potential links to neurocognitive disorders. This research sheds light on the intricate interactions between viral infection, innate immune responses, and the CNS, providing valuable insights for future investigations.

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.

Acute Administration of HIV-1 Tat Protein Drives Glutamatergic Alterations in a Rodent Model of HIV-Associated Neurocognitive Disorders

HIV-1-associated neurocognitive disorders (HAND) are a major comorbidity of HIV-1 infection, marked by impairment of executive function varying in severity. HAND affects nearly half of people living with HIV (PLWH), with mild forms predominating since the use of anti-retroviral therapies (ART). The HIV-1 transactivator of transcription (Tat) protein is found in the cerebrospinal fluid of patients adherent to ART, and its administration or expression in animals causes cognitive symptoms. Studies of Tat interaction with the N-methyl-D-aspartate receptor (NMDAR) suggest that glutamate toxicity contributes to Tat-induced impairments. To identify changes in regional glutamatergic circuitry underlying cognitive impairment, we injected recombinant Tat86 or saline to medial prefrontal cortex (mPFC) of male Sprague-Dawley rats. Rats were assessed with behavioral tasks that involve intact functioning of mPFC including the novel object recognition (NOR), spatial object recognition (SOR), and temporal order (TO) tasks at 1 and 2 postoperative weeks. Following testing, mPFC tissue was collected and analyzed by RT-PCR. Results showed Tat86 in mPFC-induced impairment in SOR, and upregulation of Grin1 and Grin2a transcripts. To further understand the mechanism of Tat toxicity, we assessed the effects of full-length Tat101 on gene expression in mPFC by RNA sequencing. The results of RNAseq suggest that glutamatergic effects of Tat86 are maintained with Tat101, as Grin2a was upregulated in Tat101-injected tissue, among other differentially expressed genes. Spatial learning and memory impairment and Grin2a upregulation suggest that exposure to Tat protein drives adaptation in mPFC, altering the function of circuitry supporting spatial learning and memory.

Gesicles packaging dCas9-VPR ribonucleoprotein complexes can combine with vorinostat and promote HIV proviral transcription

Despite the success of combination antiretroviral therapy (cART) in HIV treatment, a cure for HIV remains elusive. Scientists postulate that HIV latent reservoirs may be a vital target in curative strategies. Vorinostat is a latency-reversing agent that has demonstrated some effectiveness in reactivating latent HIV, but complementary therapies may be essential to enhance its efficacy. One such approach may utilize the CRISPR-Cas9 system, which has evolved to include transcriptional activators such as dCas9-VPR. In this study, we explored the effects of combining vorinostat coupled with gesicle-mediated delivery of dCas9-VPR in promoting the transcription of integrated HIV proviruses in HIV-NanoLuc CHME-5 microglia and J-Lat 10.6 lymphocytes. We confirmed that dCas9-VPR ribonucleoprotein complexes can be packaged into gesicles and application to cells successfully induced HIV transcription through interactions with the HIV LTR. Vorinostat also induced significant increases in proviral transcription but generated inhibition of cellular proliferation (microglia) or cell viability (lymphocytes) starting at 1,000 nM and higher concentrations. Experiments combining dCas9-VPR gesicles and vorinostat confirmed the enhanced transcriptional activation of the HIV provirus in microglia but not lymphocytes. Thus, a combination of dCas9-VPR gesicles with other latency-reversing agents may provide a complementary method to activate latent HIV in future studies utilizing patient-derived cells or small animal models.

Honokiol hexafluoro confers reversal of neuropathological markers of HIV infection in a murine SCID model

Cognitive impairment remains a persistent challenge in people living with HIV (PWLH) despite antiretroviral therapy (ART) due to ART's inability to eliminate brain HIV. HIV-induced cognitive dysfunction results from immune dysregulation, ongoing neuroinflammation, and the continuous virus presence, collectively contributing to cognitive deficits. Therefore, adjunctive therapies are needed to reduce cerebral HIV reservoirs, mitigate neuroinflammation, and impede cognitive dysfunction progression. Our study focused on Honokiol, known for its anti-inflammatory and neuroprotective properties, in an experimental mouse model simulating HIV-induced cognitive dysfunction. Using Honokiol Hexafluoro (HH), a synthetic analogue, we comprehensively evaluated its potential to ameliorate cognitive dysfunction and cerebral pathology in HIV-associated cognitive dysfunction. Our findings showed that HH treatment effectively reversed HIV-induced cognitive dysfunction, concurrently suppressing astrocyte activation, restoring neuronal dendritic arborization, and reducing microglial activation. Furthermore, HH remodeled the metabolic profile of HIV-infected human monocyte-derived macrophages, resulting in decreased activation and the promotion of a quiescent state in vitro.

Drug-drug interactions between propofol and ART drugs: Inhibiting neuronal activity by affecting glucose metabolism

BACKGROUND

The use of two or more drugs carries the potential risk of drug-drug interactions (DDIs), which may result in adverse reactions. Some human immunodeficiency virus (HIV)-infected patients who receive antiretroviral therapy (ART) may require general anesthesia with propofol (PRL) before undergoing surgical treatment. Both PRL and ART drugs may lead to neuronal dysfunction, which can be accompanied by energy metabolism disorders. Neurons take in glucose mainly through glucose transporter 3 (Glut3) which is specifically expressed on the cell membranes of neurons. However, to date, no study has examined whether the DDIs of PRL and ART drugs interfere with glucose metabolism and Glut3 expression in neurons.

METHODS

An in vitro model was constructed using the primary cultures of neurons. PRL and ART drugs (EFV, AZT, and 3TC), were added at different concentrations (low, medium, and high). The neurons were exposed to the drugs for 1, 4, 8, and 12 h. The optimal drug concentration and exposure time were selected. The cellular survival rate, glucose concentration, electrophysiology, and the expression of Glut3 were detected.

RESULTS

There were no significant changes in the cellular survival rates of the neurons that were exposed to both PRL and ART drugs at low concentrations for 1 h. However, the survival rates of the neurons decreased significantly as the drug concentrations and durations increased. The glucose concentration of the neurons that were exposed to both PRL and the ART drugs was significantly decreased. The glucose concentration of the neurons was not affected by any individual drug. The amplitude of the action potential and the expression of Glut3 were decreased in the neurons that were exposed to both PRL and ART drugs.

CONCLUSIONS

The main adverse reactions induced by the DDIs between PRL and the ART drugs were decreased glucose metabolism and neuronal damage, which were caused by inhibiting the expression of Glut3. More importantly, we found that decreases in glucose metabolism predated neuronal damage.

HIV-1 mRNA knockdown with CRISPR/CAS9 enhances neurocognitive function

Mixed glia are infiltrated with HIV-1 virus early in the course of infection leading to the development of a persistent viral reservoir in the central nervous system. Modification of the HIV-1 genome using gene editing techniques, including CRISPR/Cas9, has shown great promise towards eliminating HIV-1 viral reservoirs; whether these techniques are capable of removing HIV-1 viral proteins from mixed glia, however, has not been systematically evaluated. Herein, the efficacy of adeno-associated virus 9 (AAV9)-CRISPR/Cas9 gene editing for eliminating HIV-1 messenger RNA (mRNA) from cortical mixed glia was evaluated in vitro and in vivo. In vitro, a within-subjects experimental design was utilized to treat mixed glia isolated from neonatal HIV-1 transgenic (Tg) rats with varying doses (0, 0.9, 1.8, 2.7, 3.6, 4.5, or 5.4 µL corresponding to a physical titer of 0, 4.23 × 109, 8.46 × 109, 1.269 × 1010, 1.692 × 1010, 2.115 × 1010, and 2.538 × 1010 gc/µL) of CRISPR/Cas9 for 72 h. Dose-dependent decreases in the number of HIV-1 mRNA, quantified using an innovative in situ hybridization technique, were observed in a subset (i.e., n = 5 out of 8) of primary mixed glia. In vivo, HIV-1 Tg rats were retro-orbitally inoculated with CRISPR/Cas9 for two weeks, whereby treatment resulted in profound excision (i.e., approximately 53.2%) of HIV-1 mRNA from the medial prefrontal cortex. Given incomplete excision of the HIV-1 viral genome, the clinical relevance of HIV-1 mRNA knockdown for eliminating neurocognitive impairments was evaluated via examination of temporal processing, a putative neurobehavioral mechanism underlying HIV-1-associated neurocognitive disorders (HAND). Indeed, treatment with CRISPR/Cas9 protractedly, albeit not permanently, restored the developmental trajectory of temporal processing. Proof-of-concept studies, therefore, support the susceptibility of mixed glia to gene editing and the potential of CRISPR/Cas9 to serve as a novel therapeutic strategy for HAND, even in the absence of full viral eradication.

Caspase cleavage of gasdermin E causes neuronal pyroptosis in HIV-associated neurocognitive disorder

Despite effective antiretroviral therapies, 20-30% of persons with treated HIV infection develop a neurodegenerative syndrome termed HIV-associated neurocognitive disorder (HAND). HAND is driven by HIV expression coupled with inflammation in the brain but the mechanisms underlying neuronal damage and death are uncertain. The inflammasome-pyroptosis axis coordinates an inflammatory type of regulated lytic cell death that is underpinned by the caspase-activated pore-forming gasdermin proteins. The mechanisms driving neuronal pyroptosis were investigated herein in models of HAND, using multi-platform molecular and morphological approaches that included brain tissues from persons with HAND and simian immunodeficiency virus (SIV)-infected non-human primates as well as cultured human neurons. Neurons in the frontal cortices from persons with HAND showed increased cleaved gasdermin E (GSDME), which was associated with β-III tubulin degradation and increased HIV levels. Exposure of cultured human neurons to the HIV-encoded viral protein R (Vpr) elicited time-dependent cleavage of GSDME and Ninjurin-1 (NINJ1) induction with associated cell lysis that was inhibited by siRNA suppression of both proteins. Upstream of GSDME cleavage, Vpr exposure resulted in activation of caspases-1 and 3. Pretreatment of Vpr-exposed neurons with the caspase-1 inhibitor, VX-765, reduced cleavage of both caspase-3 and GSDME, resulting in diminished cell death. To validate these findings, we examined frontal cortical tissues from SIV-infected macaques, disclosing increased expression of GSDME and NINJ1 in cortical neurons, which was co-localized with caspase-3 detection in animals with neurological disease. Thus, HIV infection of the brain triggers the convergent activation of caspases-1 and -3, which results in GSDME-mediated neuronal pyroptosis in persons with HAND. These findings demonstrate a novel mechanism by which a viral infection causes pyroptotic death in neurons while also offering new diagnostic and therapeutic strategies for HAND and other neurodegenerative disorders.

Functional Analysis of KAP1/TRIM28 Requirements for HIV-1 Transcription Activation

HIV-1 latency maintenance and reactivation are regulated by several viral and host factors. One such factor is Krüppel-associated box (KRAB)-associated protein 1 (KAP1: also named TRIM28 or TIF1β). While initial studies have revealed KAP1 to be a positive regulator of latency reversal in transformed and primary CD4+ T cells, subsequent studies have proposed KAP1 to be a repressor required for latency maintenance. Given this discrepancy, in this study, we re-examine KAP1 transcription regulatory functions using a chemical genetics strategy to acutely deplete KAP1 expression to avoid the accumulation of indirect effects. Notably, KAP1 acute loss partially decreased HIV-1 promoter activity in response to activating signals, a function that can be restored upon complementation with exogenous KAP1, thus revealing that KAP1-mediated activation is on target. By combining comprehensive KAP1 domain deletion and mutagenesis in a cell-based reporter assay, we genetically defined the RING finger domain and an Intrinsically Disordered Region as key activating features. Together, our study solidifies the notion that KAP1 activates HIV-1 transcription by exploiting its multi-domain protein arrangement via previously unknown domains and functions.

Neurodevelopmental and Neuropsychiatric Disorders

This chapter will focus on microglial involvement in neurodevelopmental and neuropsychiatric disorders, particularly autism spectrum disorder (ASD), schizophrenia and major depressive disorder (MDD). We will describe the neuroimmune risk factors that contribute to the etiopathology of these disorders across the lifespan, including both in early life and adulthood. Microglia, being the resident immune cells of the central nervous system, could play a key role in triggering and determining the outcome of these disorders. This chapter will review preclinical and clinical findings where microglial morphology and function were examined in the contexts of ASD, schizophrenia and MDD. Clinical evidence points out to altered microglial morphology and reactivity, as well as increased expression of pro-inflammatory cytokines, supporting the idea that microglial abnormalities are involved in these disorders. Indeed, animal models for these disorders found altered microglial morphology and homeostatic functions which resulted in behaviours related to these disorders. Additionally, as microglia have emerged as promising therapeutic targets, we will also address in this chapter therapies involving microglial mechanisms for the treatment of neurodevelopmental and neuropsychiatric disorders.

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.

Neurological Complications Caused by Human Immunodeficiency Virus (HIV) and Associated Opportunistic Co-infections: A Review on their Diagnosis and Therapeutic Insights

Neurocognitive disorders associated with human immunodeficiency virus (HIV) infected individuals increase the risk of mortality and morbidity that remain a prevalent clinical complication even in the antiretroviral therapy era. It is estimated that a considerable number of people in the HIV community are developing neurological complications at their early stages of infection. The daily lives of people with chronic HIV infections are greatly affected by cognitive declines such as loss of attention, learning, and executive functions, and other adverse conditions like neuronal injury and dementia. It has been found that the entry of HIV into the brain and subsequently crossing the blood-brain barrier (BBB) causes brain cell damage, which is the prerequisite for the development of neurocognitive disorders. Besides the HIV replication in the central nervous system and the adverse effects of antiretroviral therapy on the BBB, a range of opportunistic infections, including viral, bacterial, and parasitic agents, augment the neurological complications in people living with HIV (PLHIV). Given the immuno-compromised state of PLHIV, these co-infections can present a wide range of clinical syndromes with atypical manifestations that pose challenges in diagnosis and clinical management, representing a substantial burden for the public health system. Therefore, the present review narrates the neurological complications triggered by HIV and their diagnosis and treatment options. Moreover, coinfections that are known to cause neurological disorders in HIV infected individuals are highlighted.

Infectious Diseases

Microglia, brain-resident innate immune cells, have been extensively studied in neurodegenerative contexts like Alzheimer's disease. The Coronavirus disease 2019 (COVID-19) pandemic highlighted how peripheral infection and inflammation can be detrimental to the neuroimmune milieu and initiate microgliosis driven by peripheral inflammation. Microglia can remain deleterious to brain health by sustaining inflammation in the central nervous system even after the clearance of the original immunogenic agents. In this chapter, we discuss how pulmonary infection with Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2) can lead to neurovascular and neuroimmune inflammation causing the neurological syndrome of post-acute sequelae of COVID-19 (PASC). Further, we incorporate lessons from the Human Immunodeficiency Virus' (HIV's) effects on microglial functioning in the era of combined antiretroviral therapies (cART) that contribute to HIV-1 associated neurocognitive disorders (HAND). Finally, we describe roles for mixed lineage kinase 3 (MLK3) and leucine-rich repeat kinase (LRRK2) as key regulators of multiple inflammatory and apoptotic pathways important to the pathogenesis of PASC and HAND. Inhibition of these pathways provides a therapeutically synergistic method of treating both PASC and HAND.

Lymphoid tissues contribute to plasma viral clonotypes early after antiretroviral therapy interruption in SIV-infected rhesus macaques

The rebound-competent viral reservoir, composed of a virus that is able to persist during antiretroviral therapy (ART) and mediate reactivation of systemic viral replication and rebound viremia after ART interruption (ATI), remains the biggest obstacle to treating HIV infection. A better understanding of the cellular and tissue origins and the dynamics of viral populations that initiate rebound upon ATI could help develop therapeutic strategies for reducing the rebound-competent viral reservoir. In this study, barcoded simian immunodeficiency virus (SIV), SIVmac239M, was used to infect rhesus macaques to enable monitoring of viral barcode clonotypes contributing to virus detectable in plasma after ATI. Blood and tissues from secondary lymphoid organs (spleen, mesenteric lymph nodes, and inguinal lymph nodes) and from the colon, ileum, lung, liver, and brain were analyzed using viral barcode sequencing, intact proviral DNA assay, single-cell RNA sequencing, and combined CODEX and RNAscope in situ hybridization. Four of seven animals had viral barcodes detectable by deep sequencing of plasma at necropsy, although plasma viral RNA remained below 22 copies per milliliter. Among the tissues studied, mesenteric lymph nodes, inguinal lymph nodes, and spleen contained viral barcodes detected in plasma. CD4+ T cells were the main cell type harboring viral RNA after ATI. Furthermore, T cell zones in lymphoid tissues showed higher viral RNA abundance than B cell zones for most animals. These findings are consistent with lymphoid tissues contributing to the virus present in plasma early after ATI.

Neuroinflammation in the Dorsal Root Ganglia and Dorsal Horn Contributes to Persistence of Nociceptor Sensitization in SIV-Infected Antiretroviral Therapy-Treated Macaques

Despite the development of antiretroviral therapy (ART), HIV-associated distal sensory polyneuropathy remains prevalent. Using SIV-infected rhesus macaques, this study examined molecular mechanisms of peripheral and central sensitization to infer chronic pain from HIV infection. Previous studies identified atrophy in nociceptive neurons during SIV infection, which was associated with monocyte infiltration into the dorsal root ganglia (DRG). However, the sensory signaling mechanism connecting this pathology to symptoms remains unclear, especially because pain persists after resolution of high viremia and inflammation with ART. We hypothesized that residual DRG and dorsal horn neuroinflammation contributes to nociceptive sensitization. Using three cohorts of macaques [uninfected (SIV-), SIV-infected (SIV+), and SIV infected with ART (SIV+/ART)], this study showed an increase in the cellular and cytokine inflammatory profiles in the DRG of SIV+/ART macaques compared with uninfected animals. It found significant increase in the expression of nociceptive ion channels, TRPV1, and TRPA1 among DRG neurons in SIV+/ART compared with uninfected animals. SIV-infected and SIV+/ART animals showed reduced innervation of the nonpeptidergic nociceptors into the dorsal horn compared with uninfected animals. Finally, there were a significantly higher number of CD68+ cells in the dorsal horn of SIV+/ART macaques compared with uninfected animals. In summary, these data demonstrate that neuroinflammation, characteristics of nociceptor sensitization, and central terminal atrophy persists in SIV+/ART animals.

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.

Curcumin enhances elvitegravir concentration and alleviates oxidative stress and inflammatory response

In this study, we investigated the potential of using curcumin (CUR) as an adjuvant to enhance the delivery of antiretroviral drug elvitegravir (EVG) across the BBB, and alleviate oxidative stress and inflammatory response, which are the major hallmark of HIV neuropathogenesis. In a mouse model, we compared the biodistribution of EVG alone and in combination with CUR using intraperitoneal (IP) and intranasal (IN) routes. IN administration showed a significantly higher accumulation of EVG in the brain, while both IP and IN routes led to increased EVG levels in the lungs and liver. The addition of CUR further enhanced EVG brain delivery, especially when administered via the IN route. The expression of neural marker proteins, synaptophysin, L1CAM, NeuN, and GFAP was not significantly altered by EVG or CUR alone or their combination, indicating preserved neural homeostasis. After establishing improved brain concentration and safety of CUR-adjuvanted EVG in mice in acute treatment, we studied the effect of this treatment in HIV-infected U1 macrophages. In U1 macrophages, we also observed that the addition of CUR enhanced the intracellular concentration of EVG. The total area under the curve (AUCtot) for EVG was significantly higher in the presence of CUR. We also evaluated the effects of CUR on oxidative stress and antioxidant capacity in EVG-treated U1 macrophages. CUR reduced oxidative stress, as evidenced by decreased reactive oxygen species (ROS) levels and elevated antioxidant enzyme expression. Furthermore, the combination of CUR and EVG exhibited a significant reduction in proinflammatory cytokines (TNFα, IL-1β, IL-18) and chemokines (RANTES, MCP-1) in U1 macrophages. Additionally, western blot analysis confirmed the decreased expression of IL-1β and TNF-α in EVG + CUR-treated cells. These findings suggest the potential of CUR to enhance EVG permeability to the brain and subsequent efficacy of EVG, including HIV neuropathogenesis.

Persistence of intact HIV-1 proviruses in the brain during antiretroviral therapy

HIV-1 reservoir cells that circulate in peripheral blood during suppressive antiretroviral therapy (ART) have been well characterized, but little is known about the dissemination of HIV-1-infected cells across multiple anatomical tissues, especially the CNS. Here, we performed single-genome, near full-length HIV-1 next-generation sequencing to evaluate the proviral landscape in distinct anatomical compartments, including multiple CNS tissues, from 3 ART-treated participants at autopsy. While lymph nodes and, to a lesser extent, gastrointestinal and genitourinary tissues represented tissue hotspots for the persistence of intact proviruses, we also observed intact proviruses in CNS tissue sections, particularly in the basal ganglia. Multi-compartment dissemination of clonal intact and defective proviral sequences occurred across multiple anatomical tissues, including the CNS, and evidence for the clonal proliferation of HIV-1-infected cells was found in the basal ganglia, in the frontal lobe, in the thalamus and in periventricular white matter. Deep analysis of HIV-1 reservoirs in distinct tissues will be informative for advancing HIV-1 cure strategies.

The latent HIV reservoir: current advances in genetic sequencing approaches

Multiple cellular HIV reservoirs in diverse anatomical sites can undergo clonal expansion and persist for years despite suppressive antiretroviral therapy, posing a major barrier toward an HIV cure. Commonly adopted assays to assess HIV reservoir size mainly consist of PCR-based measures of cell-associated total proviral DNA, intact proviruses and transcriptionally competent provirus (viral RNA), flow cytometry and microscopy-based methods to measure translationally competent provirus (viral protein), and quantitative viral outgrowth assay, the gold standard to measure replication-competent provirus; yet no assay alone can provide a comprehensive view of the total HIV reservoir or its dynamics. Furthermore, the detection of extant provirus by these measures does not preclude defects affecting replication competence. An accurate measure of the latent reservoir is essential for evaluating the efficacy of HIV cure strategies. Recent approaches have been developed, which generate proviral sequence data to create a more detailed profile of the latent reservoir. These sequencing approaches are valuable tools to understand the complex multicellular processes in a diverse range of tissues and cell types and have provided insights into the mechanisms of HIV establishment and persistence. These advancements over previous sequencing methods have allowed multiplexing and new assays have emerged, which can document transcriptional activity, chromosome accessibility, and in-depth cellular phenotypes harboring latent HIV, enabling the characterization of rare infected cells across restrictive sites such as the brain. In this manuscript, we provide a review of HIV sequencing-based assays adopted to address challenges in quantifying and characterizing the latent HIV reservoir.

Influence of HIV infection on cognition and overall intelligence in HIV-infected individuals: advances and perspectives

It is now well understood that HIV-positive individuals, even those under effective ART, tend to develop a spectrum of cognitive, motor, and/or mood conditions which are contemporarily referred to as HIV-associated neurocognitive disorder (HAND), and which is directly related to HIV-1 infection and HIV-1 replication in the central nervous system (CNS). As HAND is known to induce difficulties associated with attention, concentration, and memory, it is thus legitimate and pertinent to speculate upon the possibility that HIV infection may well influence human cognition and intelligence. We therefore propose herein to review the concept of intelligence, the concept of cells of intelligence, the influence of HIV on these particular cells, and the evidence pointing to differences in observed intelligence quotient (IQ) scores between HIV-positive and HIV-negative individuals. Additionally, cumulative research evidence continues to draw attention to the influence of the gut on human intelligence. Up to now, although it is known that HIV infection profoundly alters both the composition and diversity of the gut microbiota and the structural integrity of the gut, the influence of the gut on intelligence in the context of HIV infection remains poorly described. As such, we also provide herein a review of the different ways in which HIV may influence human intelligence via the gut-brain axis. Finally, we provide a discourse on perspectives related to HIV and human intelligence which may assist in generating more robust evidence with respect to this issue in future studies. Our aim is to provide insightful knowledge for the identification of novel areas of investigation, in order to reveal and explain some of the enigmas related to HIV infection.

Low levels of peripheral blood activated and senescent T cells characterize people with HIV-1-associated neurocognitive disorders

Background

HIV infection induces a 75% increase in the risk of developing neurocognitive impairment (NCI), which has been linked to immune activation. We therefore looked for immune activation markers correlating with NCI.

Method

Sixty-five people aged 55-70 years living with controlled HIV-1 infection were enrolled in the study and their neurocognitive ability was assessed according to the Frascati criteria. Fifty-nine markers of T4 cell, T8 cell, NK cell, and monocyte activation, inflammation and endothelial activation were measured in their peripheral blood. White matter hyperintensities (WMH) were identified by magnetic resonance imaging. Double hierarchical clustering was performed for the activation markers and 240 patients including the 65 whose neurocognitive performance had been evaluated.

Results

Thirty-eight percent of volunteers presented NCI. Twenty-four percent of them were asymptomatic and fourteen percent had a mild disorder. Strikingly, activated (HLA-DR+) as well as senescent (CD57+CD28-CD27±) T4 cells and T8 cells were less prevalent in the peripheral blood of participants with NCI than in participants without the disorder. Accordingly, the percentage of HLA-DR+ T4 cells was lower in volunteers with periventricular and deep WMH. The double hierarchical clustering unveiled six different immune activation profiles. The neurocognitive performances of participants with two of these six profiles were poor. Here again, these two profiles were characterized by a low level of T4 and T8 cell activation and senescence.

Conclusion

Our observation of low circulating levels of activated and senescent T cells in HIV-1 patients with NCI raises the interesting hypothesis that these lymphocytes may be recruited into the central nervous system.

Mathematical Models of HIV-1 Dynamics, Transcription, and Latency

HIV-1 latency is a major barrier to curing infections with antiretroviral therapy and, consequently, to eliminating the disease globally. The establishment, maintenance, and potential clearance of latent infection are complex dynamic processes and can be best described with the help of mathematical models followed by experimental validation. Here, we review the use of viral dynamics models for HIV-1, with a focus on applications to the latent reservoir. Such models have been used to explain the multi-phasic decay of viral load during antiretroviral therapy, the early seeding of the latent reservoir during acute infection and the limited inflow during treatment, the dynamics of viral blips, and the phenomenon of post-treatment control. Finally, we discuss that mathematical models have been used to predict the efficacy of potential HIV-1 cure strategies, such as latency-reversing agents, early treatment initiation, or gene therapies, and to provide guidance for designing trials of these novel interventions.

Occludin: a gatekeeper of brain Infection by HIV-1

Compromised structure and function of the blood-brain barrier (BBB) is one of the pathological hallmarks of brain infection by HIV-1. BBB damage during HIV-1 infection has been associated with modified expression of tight junction (TJ) proteins, including occludin. Recent evidence indicated occludin as a redox-sensitive, multifunctional protein that can act as both an NADH oxidase and influence cellular metabolism through AMPK kinase. One of the newly identified functions of occludin is its involvement in regulating HIV-1 infection. Studies suggest that occludin expression levels and the rate of HIV-1 infection share a reverse, bidirectional relationship; however, the mechanisms of this relationship are unclear. In this review, we describe the pathways involved in the regulation of HIV-1 infection by occludin. We propose that occludin may serve as a potential therapeutic target to control HIV-1 infection and to improve the lives of people living with HIV-1.

HIV-1 mRNA Knockdown with CRISPR/Cas9 Enhances Neurocognitive Function

Mixed glia are infiltrated with HIV-1 virus early in the course of infection leading to the development of a persistent viral reservoir in the central nervous system. Modification of the HIV-1 genome using gene editing techniques, including CRISPR/Cas9, has shown great promise towards eliminating HIV-1 viral reservoirs; whether these techniques are capable of removing HIV-1 viral proteins from mixed glia, however, has not been systematically evaluated. Herein, the efficacy of adeno-associated virus 9 (AAV9)-CRISPR/Cas9 gene editing for eliminating HIV-1 mRNA from cortical mixed glia was evaluated in vitro and in vivo. In vitro, a within-subjects experimental design was utilized to treat mixed glia isolated from neonatal HIV-1 transgenic (Tg) rats with varying doses (0, 0.9, 1.8, 2.7, 3.6, 4.5, or 5.4 μL) of CRISPR/Cas9 for 72 hours. Dose-dependent decreases in the number of HIV-1 mRNA, quantified using an innovative in situ hybridization technique, were observed in a subset (i.e., n=5 out of 8) of primary mixed glia. In vivo, HIV-1 Tg rats were retro-orbitally inoculated with CRISPR/Cas9 for two weeks, whereby treatment resulted in profound excision (i.e., approximately 53.2%) of HIV-1 mRNA from the mPFC. Given incomplete excision of the HIV-1 viral genome, the clinical relevance of HIV-1 mRNA knockdown for eliminating neurocognitive impairments was evaluated via examination of temporal processing, a putative neurobehavioral mechanism underlying HIV-1 associated neurocognitive disorders (HAND). Indeed, treatment with CRISPR/Cas9 partially restored the developmental trajectory of temporal processing. Proof-of-concept studies, therefore, support the susceptibility of mixed glia to gene editing and the potential of CRISPR/Cas9 to serve as a novel therapeutic strategy for HAND, even in the absence of full viral eradication.

Psychological stress is associated with arterial inflammation in people living with treated HIV infection

Stress and depression are increasingly recognized as cerebrovascular risk factors, including among high stress populations such as people living with HIV infection (PLWH). Stress may contribute to stroke risk through activation of neural inflammatory pathways. In this cross-sectional study, we examined the relationships between stress, systemic and arterial inflammation, and metabolic activity in stress-related brain regions on 18F-fluorodeoxyglucose (FDG)-PET in PLWH. Participants were recruited from a parent trial evaluating the impact of alirocumab on radiologic markers of cardiovascular risk in people with treated HIV infection. We administered a stress battery to assess different forms of psychological stress, specifying the Perceived Stress Scale as the primary stress measure, and quantified plasma markers of inflammation and immune activation. Participants underwent FDG-PET of the brain, neck, and chest. Age- and sex-matched control participants without HIV infection were selected for brain FDG-PET comparisons. Among PLWH, we used nonparametric pairwise correlations, partial correlations, and linear regression to investigate the association between stress and 1) systemic inflammation; 2) atherosclerotic inflammation on FDG-PET; and metabolic activity in 3) brain regions in which glucose metabolism differed significantly by HIV serostatus; and 4) in a priori defined stress-responsive regions of interest (ROI) and stress-related neural network activity (i.e., ratio of amygdala to ventromedial prefrontal cortex or temporal lobe activity). We studied 37 PLWH (mean age 60 years, 97% men) and 29 control participants without HIV (mean age 62 years, 97% men). Among PLWH, stress was significantly correlated with systemic inflammation (r = 0.33, p = 0.041) and arterial inflammation in the carotid (r = 0.41, p = 0.023) independent of age, race/ethnicity, traditional vascular risk factors and health-related behaviors. In voxel-wise analyses, metabolic activity in a cluster corresponding to the anterior medial temporal lobes, including the bilateral amygdalae, was significantly lower in PLWH compared with controls. However, we did not find a significant positive relationship between stress and this cluster of decreased metabolic activity in PLWH, a priori defined stress-responsive ROI, or stress-related neural network activity. In conclusion, psychological stress was associated with systemic and carotid arterial inflammation in this group of PLWH with treated infection. These data provide preliminary evidence for a link between psychological stress, inflammation, and atherosclerosis as potential drivers of excess cerebrovascular risk among PLWH.

Advancing the preclinical study of comorbid neuroHIV and substance use disorders: Current perspectives and future directions

Human immunodeficiency virus (HIV) remains a persistent public health concern throughout the world. Substance use disorders (SUDs) are a common comorbidity that can worsen treatment outcomes for people living with HIV. The relationship between HIV infection and SUD outcomes is likely bidirectional, making clear interrogation of neurobehavioral outcomes challenging in clinical populations. Importantly, the mechanisms through which HIV and addictive drugs disrupt homeostatic immune and CNS function appear to be highly overlapping and synergistic within HIV-susceptible reward and motivation circuitry in the central nervous system. Decades of animal research have revealed invaluable insights into mechanisms underlying the pathophysiology SUDs and HIV, although translational studies examining comorbid SUDs and HIV are very limited due to the technical challenges of modeling HIV infection preclinically. In this review, we discuss preclinical animal models of HIV and highlight key pathophysiological characteristics of each model, with a particular emphasis on rodent models of HIV. We then review the implementation of these models in preclinical SUD research and identify key gaps in knowledge in the field. Finally, we discuss how cutting-edge behavioral neuroscience tools, which have revealed key insights into the neurobehavioral mechanisms of SUDs, can be applied to preclinical animal models of HIV to reveal potential, novel treatment avenues for comorbid HIV and SUDs. Here, we argue that future preclinical SUD research would benefit from incorporating comorbidities such as HIV into animal models and would facilitate the discovery of more refined, subpopulation-specific mechanisms and effective SUD prevention and treatment targets.

Suppression of HIV and cocaine-induced neurotoxicity and inflammation by cell penetrable itaconate esters

HIV-associated neurological disorder (HAND) is a serious complication of HIV infection, marked by neurotoxicity induced by viral proteins like Tat. Substance abuse exacerbates neurocognitive impairment in people living with HIV. There is an urgent need for effective therapeutic strategies to combat HAND comorbid with Cocaine Use Disorder (CUD). Our analysis of the HIV and cocaine-induced transcriptomes in primary cortical cultures revealed a significant overexpression of the macrophage-specific gene, aconitate decarboxylase 1 (Acod1), caused by the combined insults of HIV and cocaine. ACOD1 protein converts the tricarboxylic acid intermediate cis-aconitate into itaconate during the activation of inflammation. The itaconate produced facilitates cytokine production and subsequently activates anti-inflammatory transcription factors, shielding macrophages from infection-induced cell death. While the role of itaconate' in limiting inflammation has been studied in peripheral macrophages, its immunometabolic function remains unexplored in HIV and cocaine-exposed microglia. We assessed in this model system the potential of 4-octyl-itaconate (4OI), a cell-penetrable esterified form of itaconate known for its potent anti-inflammatory properties and potential therapeutic applications. We administered 4OI to primary cortical cultures exposed to Tat and cocaine. 4OI treatment increased the number of microglial cells in both untreated and Tat±Cocaine-treated cultures and also reversed the morphological altercations induced by Tat and cocaine. In the presence of 4OI, microglial cells also appeared more ramified, resembling the quiescent microglia. Consistent with these results, 4OI treatment inhibited the secretion of the proinflammatory cytokines IL-1α, IL-1β, IL-6, and MIP1-α induced by Tat and cocaine. Transcriptome profiling further determined that Nrf2 target genes such as NAD(P)H quinone oxidoreductase 1 (Nqo1), Glutathione S-transferase Pi (Gstp1), and glutamate cysteine ligase catalytic (Gclc), were most significantly activated in Tat-4OI treated cultures, relative to Tat alone. Further, genes associated with cytoskeleton dynamics in inflammatory microglia were downregulated by 4OI treatment. Together, the results strongly suggest 4-octyl-itaconate holds promise as a potential candidate for therapeutic development aimed at addressing HAND coupled with CUD comorbidities.