Variable region 4 of SIV envelope correlates with rapid disease progression in morphine-exposed macaques infected with SIV/SHIV

Opioid and neuroHIV Comorbidity - Current and Future Perspectives

With the current national opioid crisis, it is critical to examine the mechanisms underlying pathophysiologic interactions between human immunodeficiency virus (HIV) and opioids in the central nervous system (CNS). Recent advances in experimental models, methodology, and our understanding of disease processes at the molecular and cellular levels reveal opioid-HIV interactions with increasing clarity. However, despite the substantial new insight, the unique impact of opioids on the severity, progression, and prognosis of neuroHIV and HIV-associated neurocognitive disorders (HAND) are not fully understood. In this review, we explore, in detail, what is currently known about mechanisms underlying opioid interactions with HIV, with emphasis on individual HIV-1-expressed gene products at the molecular, cellular and systems levels. Furthermore, we review preclinical and clinical studies with a focus on key considerations when addressing questions of whether opioid-HIV interactive pathogenesis results in unique structural or functional deficits not seen with either disease alone. These considerations include, understanding the combined consequences of HIV-1 genetic variants, host variants, and μ-opioid receptor (MOR) and HIV chemokine co-receptor interactions on the comorbidity. Lastly, we present topics that need to be considered in the future to better understand the unique contributions of opioids to the pathophysiology of neuroHIV. Graphical Abstract Blood-brain barrier and the neurovascular unit. With HIV and opiate co-exposure (represented below the dotted line), there is breakdown of tight junction proteins and increased leakage of paracellular compounds into the brain. Despite this, opiate exposure selectively increases the expression of some efflux transporters, thereby restricting brain penetration of specific drugs.

NF-κB Duplications in the Promoter-Variant HIV-1C LTR Impact Inflammation Without Altering Viral Replication in the Context of Simian Human Immunodeficiency Viruses and Opioid-Exposure

Recent spread of the promoter variant (4-κB) Human immunodeficiency virus-1 clade C (HIV-1C) strain is attributed to duplication of the Nuclear Factor Kappa B (NF-κB) binding sites and potential increased heroin consumption in India. To study the underlying biology of 4-κB HIV-1C in rhesus macaques, we engineered a promoter-chimera variant (4NF-κB) Simian Human Immunodeficiency Virus (SHIV) by substituting the HIV-1C Long Terminal Repeat (LTR) region consisting of 4 NF-κB and 3 Sp-1 sites with the corresponding segment in the LTR of SHIV AD8EO. The wild-type (3NF-κB) promoter-chimera SHIV was generated by inactivating the 5' proximal NF-κB binding site in SHIV 4NF-κB. CD8-depleted rhesus macaque PBMCs (RM-PBMCs) were infected with the promoter-chimera and AD8EO SHIVs to determine the effects of opioid-exposure on inflammation, NF-κB activation, neurotoxicity in neuronal cells and viral replication. Morphine-exposure of RM-PBMCs infected with SHIVs 4NF-κB, 3NF-κB, and AD8EO altered cellular transcript levels of monocyte chemoattractant protein 1, interleukin 6, interleukin 1β, and Tumor Necrosis Factor α. Of note, divergent alteration of the cytokine transcript levels was observed with these promoter-chimera wild-type and variant SHIVs. NF-κB activation was observed during infection of all three SHIVs with morphine-exposure. Finally, we observed that SHIV AD8EO infection and exposure to both morphine and naloxone had the greatest impact on the neurotoxicity. The promoter-chimera SHIV 4NF-κB and SHIV 3NF-κB did not have a similar effect on neurotoxicity as compared to SHIV AD8EO. All SHIVs replicated efficiently at comparable levels in RM-PBMCs and morphine-exposure did not alter viral replication kinetics. Future in vivo studies in rhesus macaques will provide greater understanding of 4-κB HIV-1C viral immunopathogenesis and onset of disease in the central nervous system during morphine-exposure.

Critical amino acids within the human immunodeficiency virus type 1 envelope glycoprotein V4 N- and C-terminals contribute to virus entry

The importance of the fourth variable (V4) region of the human immunodeficiency virus 1 (HIV-1) envelope glycoprotein (Env) in virus infection has not been well clarified, though the polymorphism of this region has been found to be associated with disease progression to acquired immunodeficiency syndrome (AIDS). In the present work, we focused on the correlation between HIV-1 gp120 V4 region polymorphism and the function of the region on virus entry, and the possible mechanisms for how the V4 region contributes to virus infectivity. Therefore, we analyzed the differences in V4 sequences along with coreceptor usage preference from CCR5 to CXCR4 and examined the importance of the amino acids within the V4 region for CCR5- and CXCR4-tropic virus entry. In addition, we determined the influence of the V4 amino acids on Env expression and gp160 processing intracellularly, as well as the amount of Env on the pseudovirus surface. The results indicated that V4 tended to have a shorter length, fewer potential N-linked glycosylation sites (PNGS), greater evolutionary distance, and a lower negative net charge when HIV-1 isolates switched from a coreceptor usage preference for CCR5 to CXCR4. The N- and C-terminals of the HIV-1 V4 region are highly conserved and critical to maintain virus entry ability, but only the mutation at position 417 in the context of ADA (a R5-tropic HIV-1 strain) resulted in the ability to utilize CXCR4. In addition, 390L, 391F, 414I, and 416L are critical to maintain gp160 processing and maturation. It is likely that the hydrophobic properties and the electrostatic surface potential of gp120, rather than the conformational structure, greatly contribute to this V4 functionality. The findings provide information to aid in the understanding of the functions of V4 in HIV-1 entry and offer a potential target to aid in the development of entry inhibitors.

Identification and molecular characterization of SIV Vpr R50G mutation associated with long term survival in SIV-infected morphine dependent and control macaques

Viral protein R (Vpr) is an accessory protein of HIV and SIV involved in the pathogenesis of viral infection. In this study, we monitored SIV evolution in the central nervous system and other organs from morphine-dependent and control animals by sequencing vpr in an attempt to understand the relationship between drug abuse, disease progression, and compartmentalization of viral evolution. Animals in the morphine group developed accelerated disease and died within twenty weeks post-infection. A unique mutation, R50G, was identified in the macaques that survived regardless of morphine exposure. Functional studies revealed that the R50G mutation exhibited altered cellular localization and decreased the expression levels of both IL-6 and IL-8. Our results, therefore, suggest that sequence changes within the SIV/17E-Fr vpr occur regardless of drug abuse but correlate with survival, and that they alter disease progression rates by affecting Vpr functions.

Opiate drug use and the pathophysiology of neuroAIDS

Opiate abuse and HIV-1 have been described as interrelated epidemics, and even in the advent of combined anti-retroviral therapy, the additional abuse of opiates appears to result in greater neurologic and cognitive deficits. The central nervous system (CNS) is particularly vulnerable to interactive opiate-HIV-1 effects, in part because of the unique responses of microglia and astroglia. Although neurons are principally responsible for behavior and cognition, HIV-1 infection and replication in the brain is largely limited to microglia, while astroglia and perhaps glial progenitors can be latently infected. Thus, neuronal dysfunction and injury result from cellular and viral toxins originating from HIV-1 infected/exposed glia. Importantly, subsets of glial cells including oligodendrocytes, as well as neurons, express µ-opioid receptors and therefore can be direct targets for heroin and morphine (the major metabolite of heroin in the CNS), which preferentially activate µ-opioid receptors. This review highlights findings that neuroAIDS is a glially driven disease, and that opiate abuse may act at multiple glial-cell types to further compromise neuron function and survival. The ongoing, reactive cross-talk between opiate drug and HIV-1 co-exposed microglia and astroglia appears to exacerbate critical proinflammatory and excitotoxic events leading to neuron dysfunction, injury, and potentially death. Opiates enhance synaptodendritic damage and a loss of synaptic connectivity, which is viewed as the substrate of cognitive deficits. We especially emphasize that opioid signaling and interactions with HIV-1 are contextual, differing among cell types, and even within subsets of the same cell type. For example, astroglia even within a single brain region are heterogeneous in their expression of µ-, δ-, and κ-opioid receptors, as well as CXCR4 and CCR5, and Toll-like receptors. Thus, defining the distinct targets engaged by opiates in each cell type, and among brain regions, is critical to an understanding of how opiate abuse exacerbates neuroAIDS.

Accelerated evolution of SIV env within the cerebral compartment in the setting of morphine-dependent rapid disease progression

Human immunodeficiency virus-1 (HIV-1) and simian immunodeficiency virus (SIV) have been shown to compartmentalize within various tissues, including the brain. However, the evolution of viral quasispecies in the setting of drug abuse has not been characterized. The goal of this study was to examine viral evolution in the cerebral compartment of morphine-dependent and control macaques to determine its role in rapid disease progression. To address this issue, we analyzed the envelope (env) gene from proviral DNA in our SIV/SHIV macaque model of morphine dependence and AIDS. Analyses of proviral DNA revealed a direct correlation between total genetic changes and survival time. However, the rate of evolution during disease progression was higher in morphine-dependent and rapid-progressor macaques than was the rate of evolution in the control animals. This study provides additional insight into SIV envelope variation in the CNS of morphine-dependent macaques and genotypes that may have evolved in the brain and contributed to disease progression.

Morphine and rapid disease progression in nonhuman primate model of AIDS: inverse correlation between disease progression and virus evolution

HIV and simian immunodeficiency virus (SIV) have a formidable capacity for mutation and adaptation, a characteristic that has contributed to the extensive genetic variability. Evolutionary pressures imposed within the host and the viral capacity to mutate lead to the generation of such variants. To date, very little information is available regarding the evolution of HIV with drug abuse as a cofounding factor. Using our macaque model of drug dependency and AIDS, we have investigated the dynamics of SIV mutations in the genes tat, vpr, envelope, and nef. The results presented in this review, from our laboratory and others, contribute to the overall understanding of how drugs of abuse might influence immune selective pressure contribution to variation in different SIV genes. Additionally, the studies presented could help enlighten the development of HIV vaccines that take into consideration viral diversity.

Analysis of the V1V2 region of the SIV envelope in the brains of morphine-dependent and control SIV/SHIV-infected macaques

Six morphine-dependent and three control macaques were infected with a mixture of SIV/SHIV. Half of the animals in the morphine group developed accelerated disease (rapid progressor) and died within 20 weeks postinfection. The evolution of the envelope gene in the brain of the rapid progressor and morphine-dependent group along with that in the control group was assessed. Six to 10 clones from the brain of each macaque were sequenced and were compared against each other as well as against a challenge virus. Analysis of the sequences revealed that the diversity and divergence of the clones were higher in the control group as compared to the morphine-dependent macaques, although this difference was not statistically significant.

Opiates, immune system, acquired immunodeficiency syndrome, and nonhuman primate model

Both human immunodeficiency virus (HIV) and illicit drug addiction remain major health problems not only in the United States but all over globe. The effect of drug addiction on HIV/AIDS (acquired immunodeficiency syndrome) has been somewhat underexplored. However, in United States more than one fourth of HIV-positive individuals are injection drug users. Opiates are known to negatively affect the immune system, and therefore may have deleterious effects on progression of disease among HIV-infected individuals. This review discusses the effects of opiates on immune system as well as its effect on HIV replication and AIDS progression. In addition, the effects of opiates on disease progression in non-human primate model of AIDS is presented with at least one possible reason for rapid disease progression in multi-virus the challenge model.

Endogenous opiates and behavior: 2007

This paper is the thirtieth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2007 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Analysis of putative N-linked glycosylation sites and variable region of envelope HIV-1 CRF07_BC recombinant in intravenous drug users in Xinjiang Autonomous Region, China

To investigate more closely the determinants of transmission and escape in HIV-1 internal proteins, we analyzed the characterization of putative N-linked glycosylation sites (PNGSs) and the variable loop of CRF07_BC recombinant human immunodeficiency virus type 1 (HIV-1), isolated from intravenous drug users (IDUs). We studied the characterization of PNGSs and the variable loop in the C1-C5 and V1-V4 regions of the HIV-1 env gene in 12 intravenous drug users (IDUs) who were divided into two groups according to the length of infection time. In addition, two IDUs were longitudinally monitored from the time of seroconversion for 1.5 and 2.5 years. The longitudinal characterization within the individuals on PNGSs and the variable loop in the C1-C5 and V1-V4 region were also observed. Based on the above analysis, we found that PNGSs and the variable loop appeared to increase over time within IDU transmission of CRF07_BC recombinant HIV-1. We argue that limited PNGSs and the length of variable loops may be involved in selective transmission and escape.