Cocaine-mediated impact on HIV infection in humanized BLT mice

Frequent Cocaine Use is Associated With Larger HIV Latent Reservoir Size

BACKGROUND

Cocaine-one of the most frequently abused illicit drugs among persons living with HIV [people living with HIV (PLWH)]-slows the decline of viral production after antiretroviral therapy and is associated with higher HIV viral load, more rapid HIV progression, and increased mortality.

SETTING

We examined the impact of cocaine use on the CD4+ T-cell HIV latent reservoir (HLR) in virally suppressed PLWH participating in a national, longitudinal cohort study of the natural and treated history of HIV in the United States.

METHODS

CD4+ T-cell genomic DNA from 434 women of diverse ancestry (ie, 75% Black, 14% Hispanic, 12% White) who self-reported cocaine use (ie, 160 cocaine users, 59 prior users, 215 non-users) was analyzed using the Intact Proviral HIV DNA Assay, measuring intact provirus per 106 CD4+ T cells.

FINDINGS

HIV latent reservoir size differed by cocaine use (ie, median [interquartile range]: 72 [14-193] for never users, 165 [63-387] for prior users, 184 [28-502] for current users), which was statistically significantly larger in both prior (P = 0.023) and current (P = 0.001) cocaine users compared with never users.

CONCLUSIONS

Cocaine use may contribute to a larger replication competent HLR in CD4+ T cells among virologically suppressed women living with HIV. Our findings are important because women are underrepresented in HIV reservoir studies and in studies of the impact of cocaine use on outcomes among PLWH.

Impaired extinction of cocaine seeking in HIV-infected mice is accompanied by peripheral and central immune dysregulation

Substance use disorders (SUDs) are highly comorbid with HIV infection, necessitating an understanding of the interactive effects of drug exposure and HIV. The relationship between HIV infection and cocaine use disorder is likely bidirectional, with cocaine use directly impacting immune function while HIV infection alters addiction-related behavior. To better characterize the neurobehavioral and immune consequences of HIV infection and cocaine exposure, this study utilizes a humanized mouse model to investigate the outcomes of HIV-1 infection on cocaine-related behaviors in a conditioned place preference (CPP) model, and the interactive effects of cocaine and HIV infection on peripheral and central nervous system inflammation. HIV infection selectively impairs cocaine CPP extinction without effecting reinstatement or cocaine seeking under conflict. Behavioral alterations are accompanied by immune changes in HIV infected mice, including increased prefrontal cortex astrocyte immunoreactivity and brain-region specific effects on microglia number and reactivity. Peripheral immune system changes are observed in human cytokines, including HIV-induced reductions in human TNFα, and cocaine and HIV interactions on GM-CSF levels. Together these data provide new insights into the unique neurobehavioral outcomes of HIV infection and cocaine exposure and how they interact to effect immune responses.

Impaired extinction of cocaine seeking in HIV-infected mice is accompanied by peripheral and central immune dysregulation

Substance use disorders (SUDs) are highly comorbid with HIV infection, necessitating an understanding of the interactive effects of drug exposure and HIV. The relationship between progressive HIV infection and cocaine use disorder is likely bidirectional, with cocaine use having direct effects on immune function while HIV infection can alter addiction-related behavior. To better characterized the neurobehavioral and immune consequences of HIV infection and cocaine exposure, this study utilized a humanized mouse model to investigate the outcomes of progressive HIV infection on cocaine-related behaviors in a cocaine conditioned place preference (CPP) model, and the interactive effects of cocaine and HIV infection on peripheral and central nervous system inflammation. HIV infection did not impact the formation of a cocaine CPP, but did result in resistance to extinction of the CPP. No effects of HIV on yohimbine-primed reinstatement or cocaine seeking under conflict were observed. These behavioral alterations were accompanied by immune changes in HIV infected mice, including increased prefrontal cortex astrocyte immunoreactivity and brain-region specific effects on microglia number and reactivity. Peripheral immune system changes were observed in both mouse and human markers. Among other targets, this included HIV-induced reductions in mouse IL-1α and G-CSF and human TNFα and cocaine-induced alterations in human TNFα and mouse GM-CSF such that cocaine exposure increases both cytokines only in the absence of HIV infection. Together these data provide new insights into the unique neurobehavioral processes underlying HIV infection and cocaine use disorders, and further how they interact to effect immune responses.

Cocaine sensitizes the CD4+ T cells for HIV infection by co-stimulating NFAT and AP-1

The productive infection of HIV, which generates new viral progeny, depends on the activation status of the cell. In this study, we found cocaine exposure sensitizes partially active CD4+ T cells and makes them poised for productive HIV infection. We discovered that cocaine treatment enhances the metabolic state of the cells by co-stimulating several transcription factors, mainly NFAT and AP-1, the two transcription factors, which specifically play a crucial role in enhancing both HIV and the overall cellular gene expression in T cells. We found that cocaine-induced AP-1 works in tandem with NFAT to boost HIV transcription. The enhanced HIV transcription upon cocaine exposure was further confirmed through higher phosphorylation of the crucial serine residues at the carboxyl-terminal domain (CTD) of RNA polymerase II. The insights gained from this study could aid in developing highly specialized therapeutics combating the deleterious effects of cocaine on the cocaine-using HIV population.

Important role of microglia in HIV-1 associated neurocognitive disorders and the molecular pathways implicated in its pathogenesis

The development of effective combined anti-retroviral therapy (cART) led to a significant reduction in the death rate associated with human immunodeficiency virus type 1 (HIV-1) infection. However, recent studies indicate that considerably more than 50% of all HIV-1 infected patients develop HIV-1-associated neurocognitive disorder (HAND). Microglia are the foremost cells infected by HIV-1 in the central nervous system (CNS), and so, are also likely to contribute to the neurotoxicity observed in HAND. The activation of microglia induces the release of pro-inflammatory markers and altered secretion of cytokines, chemokines, secondary messengers, and reactive oxygen species (ROS) which activate signalling pathways that initiate neuroinflammation. In turn, ROS and inflammation also play critical roles in HAND. However, more efforts are required to understand the physiology of microglia and the processes involved in their activation in order to better understand the how HIV-1-infected microglia are involved in the development of HAND. In this review, we summarize the current state of knowledge about the involvement of oxidative stress mechanisms and role of HIV-induced ROS in the development of HAND. We also examine the academic literature regarding crucial HIV-1 pathogenicity factors implicated in neurotoxicity and inflammation in order to identify molecular pathways that could serve as potential therapeutic targets for treatment of this disease. KEY MESSAGES Neuroinflammation and excitotoxicity mechanisms are crucial in the pathogenesis of HAND. CNS infiltration by HIV-1 and immune cells through the blood brain barrier is a key process involved in the pathogenicity of HAND. Factors including calcium dysregulation and autophagy are the main challenges involved in HAND.

A "Drug-Dependent" Immune System Can Compromise Protection against Infection: The Relationships between Psychostimulants and HIV

Psychostimulant use is a major comorbidity in people living with HIV, which was initially explained by them adopting risky behaviors that facilitate HIV transmission. However, the effects of drug use on the immune system might also influence this phenomenon. Psychostimulants act on peripheral immune cells even before they reach the central nervous system (CNS) and their effects on immunity are likely to influence HIV infection. Beyond their canonical activities, classic neurotransmitters and neuromodulators are expressed by peripheral immune cells (e.g., dopamine and enkephalins), which display immunomodulatory properties and could be influenced by psychostimulants. Immune receptors, like Toll-like receptors (TLRs) on microglia, are modulated by cocaine and amphetamine exposure. Since peripheral immunocytes also express TLRs, they may be similarly affected by psychostimulants. In this review, we will summarize how psychostimulants are currently thought to influence peripheral immunity, mainly focusing on catecholamines, enkephalins and TLR4, and shed light on how these drugs might affect HIV infection. We will try to shift from the classic CNS perspective and adopt a more holistic view, addressing the potential impact of psychostimulants on the peripheral immune system and how their systemic effects could influence HIV infection.

HIV Neuropathogenesis in the Presence of a Disrupted Dopamine System

Antiretroviral therapy (ART) has transformed HIV into a chronic condition, lengthening and improving the lives of individuals living with this virus. Despite successful suppression of HIV replication, people living with HIV (PLWH) are susceptible to a growing number of comorbidities, including neuroHIV that results from infection of the central nervous system (CNS). Alterations in the dopaminergic system have long been associated with HIV infection of the CNS. Studies indicate that changes in dopamine concentrations not only alter neurotransmission, but also significantly impact the function of immune cells, contributing to neuroinflammation and neuronal dysfunction. Monocytes/macrophages, which are a major target for HIV in the CNS, are responsive to dopamine. Therefore, defining more precisely the mechanisms by which dopamine acts on these cells, and the changes in cellular function elicited by this neurotransmitter are necessary to develop therapeutic strategies to treat neuroHIV. This is especially important for vulnerable populations of PLWH with chemically altered dopamine concentrations, such as individuals with substance use disorder (SUD), or aging individuals using dopamine-altering medications. The specific neuropathologic and neurocognitive consequences of increased CNS dopamine remain unclear. This is due to the complex nature of HIV neuropathogenesis, and logistical and technical challenges that contribute to inconsistencies among cohort studies, animal models and in vitro studies, as well as lack of demographic data and access to human CNS samples and cells. This review summarizes current understanding of the impact of dopamine on HIV neuropathogenesis, and proposes new experimental approaches to examine the role of dopamine in CNS HIV infection. Graphical abstract HIV Neuropathogenesis in the Presence of a Disrupted Dopamine System. Both substance abuse disorders and the use of dopaminergic medications for age-related diseases are associated with changes in CNS dopamine concentrations and dopaminergic neurotransmission. These changes can lead to aberrant immune function, particularly in myeloid cells, which contributes to the neuroinflammation, neuropathology and dysfunctional neurotransmission observed in dopamine-rich regions in HIV+ individuals. These changes, which are seen despite the use antiretroviral therapy (ART), in turn lead to further dysregulation of the dopamine system. Thus, in individuals with elevated dopamine, the bi-directional interaction between aberrant dopaminergic neurotransmission and HIV infection creates a feedback loop contributing to HIV associated neurocognitive dysfunction and neuroHIV. However, the distinct contributions and interactions made by HIV infection, inflammatory mediators, ART, drugs of abuse, and age-related therapeutics are poorly understood. Defining more precisely the mechanisms by which these factors influence the development of neurological disease is critical to addressing the continued presence of neuroHIV in vulnerable populations, such as HIV-infected older adults or drug abusers. Due to the complexity of this system, understanding these effects will require a combination of novel experimental modalities in the context of ART. These will include more rigorous epidemiological studies, relevant animal models, and in vitro cellular and molecular mechanistic analysis.

The impact of substance abuse on HIV-mediated neuropathogenesis in the current ART era

Approximately 37 million people worldwide are infected with human immunodeficiency virus (HIV). One highly significant complication of HIV infection is the development of HIV-associated neurocognitive disorders (HAND) in 15-55% of people living with HIV (PLWH), that persists even in the antiretroviral therapy (ART) era. The entry of HIV into the central nervous system (CNS) occurs within 4-8 days after peripheral infection. This establishes viral reservoirs that may persist even in the presence of ART. Once in the CNS, HIV infects resident macrophages, microglia, and at low levels, astrocytes. In response to chronic infection and cell activation within the CNS, viral proteins, inflammatory mediators, and host and viral neurotoxic factors produced over extended periods of time result in neuronal injury and loss, cognitive deficits and HAND. Substance abuse is a common comorbidity in PLWH and has been shown to increase neuroinflammation and cognitive disorders. Additionally, it has been associated with poor ART adherence, and increased viral load in the cerebrospinal fluid (CSF), that may also contribute to increased neuroinflammation and neuronal injury. Studies have examined mechanisms that contribute to neuroinflammation and neuronal damage in PLWH, and how substances of abuse exacerbate these effects. This review will focus on how substances of abuse, with an emphasis on methamphetamine (meth), cocaine, and opioids, impact blood brain barrier (BBB) integrity and transmigration of HIV-infected and uninfected monocytes across the BBB, as well as their effects on monocytes/macrophages, microglia, and astrocytes within the CNS. We will also address how these substances of abuse may contribute to HIV-mediated neuropathogenesis in the context of suppressive ART. Additionally, we will review the effects of extracellular dopamine, a neurotransmitter that is increased in the CNS by substances of abuse, on HIV neuropathogenesis and how this may contribute to neuroinflammation, neuronal insult, and HAND in PLWH with active substance use. Lastly, we will discuss some potential therapies to limit CNS inflammation and damage in HIV-infected substance abusers.

HIV-1 infection alters energy metabolism in the brain: Contributions to HIV-associated neurocognitive disorders

The brain is particularly sensitive to changes in energy supply. Defects in glucose utilization and mitochondrial dysfunction are hallmarks of nearly all neurodegenerative diseases and are also associated with the cognitive decline that occurs as the brain ages. Chronic neuroinflammation driven by glial activation is commonly implicated as a contributing factor to neurodegeneration and cognitive impairment. Human immunodeficiency virus-1 (HIV-1) disrupts normal brain homeostasis and leads to a spectrum of HIV-associated neurocognitive disorders (HAND). HIV-1 activates stress responses in the brain and triggers a state of chronic neuroinflammation. Growing evidence suggests that inflammatory processes and bioenergetics are interconnected in the propagation of neuronal dysfunction. Clinical studies of people living with HIV and basic research support the notion that HIV-1 creates an environment in the CNS that interrupts normal metabolic processes at the cellular level to collectively alter whole brain metabolism. In this review, we highlight reports of abnormal brain metabolism from clinical studies and animal models of HIV-1. We also describe diverse CNS cell-specific changes in bioenergetics associated with HIV-1. Moreover, we propose that attention should be given to adjunctive therapies that combat sources of metabolic dysfunction as a mean to improve and/or prevent neurocognitive impairments.

The role of catecholamines in HIV neuropathogenesis

The success of anti-retroviral therapy has improved the quality of life and lifespan of HIV + individuals, transforming HIV infection into a chronic condition. These improvements have come with a cost, as chronic HIV infection and long-term therapy have resulted in the emergence of a number of new pathologies. This includes a variety of the neuropathological and neurocognitive effects collectively known as HIVassociated neurocognitive disorders (HAND) or NeuroHIV. These effects persist even in the absence of viral replication, suggesting that they are mediated the long-term changes in the CNS induced by HIV infection rather than by active replication. Among these effects are significant changes in catecholaminergic neurotransmission, especially in dopaminergic brain regions. In HIV-infected individuals not treated with ARV show prominent neuropathology is common in dopamine-rich brain regions and altered autonomic nervous system activity. Even infected individuals on therapy, there is significant dopaminergic neuropathology, and elevated stress and norepinephrine levels correlate with a decreased effectiveness of antiretroviral drugs. As catecholamines function as immunomodulatory factors, the resultant dysregulation of catecholaminergic tone could substantially alter the development of HIVassociated neuroinflammation and neuropathology. In this review, we discuss the role of catecholamines in the etiology of HIV neuropathogenesis. Providing a comprehensive examination of what is known about these molecules in the context of HIV-associated disease demonstrates the importance of further studies in this area, and may open the door to new therapeutic strategies that specifically ameliorate the effects of catecholaminergic dysregulation on NeuroHIV.

Continued Transmission of HIV Among Young Adults Who Inject Drugs in San Francisco: Still Room for Improvement

We measured HIV incidence rate, trend and risk factors in 564 HIV-negative young people (< 30 years) who inject drugs (PWID) in San Francisco between 2000 and 2014. HIV incidence was 0.93/100 person-years (PY; 95% CI 0.50, 1.73). Incidence varied between 0.62/100 PY in 2000-2002 and 1.06/100 PY in 2012-2014 (P for trend = 1.0). HIV incidence varied significantly (P < 0.01) by race/ethnicity: among Hispanics it was 8.19/100 PY (95% CI 3.41, 19.68), African-Americans 4.59/100 PY (95% CI 1.15, 18.37), and Whites 0.26/100 PY (95% CI 0.06, 1.03). Male participants who reported sex with men (MSM) had higher HIV incidence (2.63/100 PY; 95% CI 1.31, 5.25) compared to males who did not report MSM (0.50/100 PY; 95% CI 0.12, 1.99) (P = 0.01). Despite an overall stable HIV incidence trend, incidence was elevated among African-American and Hispanic PWID, and men who have sex with men. Addressing prevention needs in these key populations is critical for the goal of eliminating HIV transmission.

Prevalence of Substance Use in an HIV Primary Care Safety Net Clinic: A Call for Screening

Substance use complicates HIV care and prevention. Primary care clinics are an ideal setting to screen for and offer interventions for unhealthy alcohol and drug use; however, few HIV clinics routinely screen for substance use. We enrolled 208 clinic patients at an urban underserved HIV primary care clinic. We screened the patients for substance use with the Alcohol, Smoking, and Substance Involvement Score Test and measured urine toxicology. Of the 168 participants who completed screening, the majority reported tobacco or nonprescribed substance use in the previous 3 months. More African American participants reported low or no risk amphetamine use compared to Hispanic, White, or Other race participants (p < .001). Implementing standard clinic practice for screening and assessing substance use in HIV primary care clinics is needed.

Cocaine Enhances DC to T-cell HIV-1 Transmission by Activating DC-SIGN/LARG/LSP1 Complex and Facilitating Infectious Synapse Formation

DC-SIGN is a dendritic cell surface structure which participates in binding and transmission of HIV-1. Here, for the first time we demonstrate that cocaine induces over expression of DC-SIGN and significantly enhances virus transfer from DCs to T-cells by increasing the binding and internalization of HIV-1 in DCs. We found that cocaine activates a DC-SIGN mediated 'signalosome' complex by enhancing its association with LARG and LSP1. Further, LARG was observed to participate in DC-SIGN mediated internalization of HIV-1 in DCs. Intracellular trafficking studies of HIV-1 in cocaine treated DCs revealed increased co-localization of HIV-1 with endosomal or multi vesicular body (MVB) markers such as CD81 and VPS4 and decreased co-localization with the phagolysomal marker LAMP1; this signified altered intracellular trafficking and decreased degradation of HIV-1 in cocaine treated DCs. Furthermore, we found that cocaine induced activation of LARG which in turn activated Rho A and the focal adhesion molecules FAK, Pyk2 and paxillin. This signaling cascade enhanced the formation of an infectious synapse between DCs and T-cells. Our study provides insight into the molecular mechanisms of cocaine's contribution to key components in HIV pathogenesis and highlights novel targets for interrupting the virus life cycle in substance using hosts.

The effects of cocaine on HIV transcription

Illicit drug users are a high-risk population for infection with the human immunodeficiency virus (HIV). A strong correlation exists between prohibited drug use and an increased rate of HIV transmission. Cocaine stands out as one of the most frequently abused illicit drugs, and its use is correlated with HIV infection and disease progression. The central nervous system (CNS) is a common target for both drugs of abuse and HIV, and cocaine intake further accelerates neuronal injury in HIV patients. Although the high incidence of HIV infection in illicit drug abusers is primarily due to high-risk activities such as needle sharing and unprotected sex, several studies have demonstrated that cocaine enhances the rate of HIV gene expression and replication by activating various signal transduction pathways and downstream transcription factors. In order to generate mature HIV genomic transcript, HIV gene expression has to pass through both the initiation and elongation phases of transcription, which requires discrete transcription factors. In this review, we will provide a detailed analysis of the molecular mechanisms that regulate HIV transcription and discuss how cocaine modulates those mechanisms to upregulate HIV transcription and eventually HIV replication.

Impact of cocaine abuse on HIV pathogenesis

Over 1.2 million people in the United States are infected with the human immunodeficiency virus type 1 (HIV-1). Tremendous progress has been made over the past three decades on many fronts in the prevention and treatment of HIV-1 disease. However, HIV-1 infection is incurable and antiretroviral drugs continue to remain the only effective treatment option for HIV infected patients. Unfortunately, only three out of ten HIV-1 infected individuals in the US have the virus under control. Thus, majority of HIV-1 infected individuals in the US are either unaware of their infection status or not connected/retained to care or are non-adherent to antiretroviral therapy (ART). This national public health crisis, as well as the ongoing global HIV/AIDS pandemic, is further exacerbated by substance abuse, which serves as a powerful cofactor at every stage of HIV/AIDS including transmission, diagnosis, pathogenesis, and treatment. Clinical studies indicate that substance abuse may increase viral load, accelerate disease progression and worsen AIDS-related mortality even among ART-adherent patients. However, confirming a direct causal link between substance abuse and HIV/AIDS in human patients remains a highly challenging endeavor. In this review we will discuss the recent and past developments in clinical and basic science research on the effects of cocaine abuse on HIV-1 pathogenesis.