Cannabinoids Reduce Extracellular Vesicle Release from HIV-1 Infected Myeloid Cells and Inhibit Viral Transcription.

Of the 37.9 million individuals infected with human immunodeficiency virus type 1 (HIV-1), approximately 50% exhibit HIV-associated neurocognitive disorders (HAND). We and others previously showed that HIV-1 viral RNAs, such as trans-activating response (TAR) RNA, are incorporated into extracellular vesicles (EVs) and elicit an inflammatory response in recipient naïve cells. Cannabidiol (CBD) and Δ9-tetrahydrocannabinol (THC), the primary cannabinoids present in cannabis, are effective in reducing inflammation. Studies show that cannabis use in people living with HIV-1 is associated with lower viral load, lower circulating CD16+ monocytes and high CD4+ T-cell counts, suggesting a potentially therapeutic application. Here, HIV-1 infected U1 monocytes and primary macrophages were used to assess the effects of CBD. Post-CBD treatment, EV concentrations were analyzed using nanoparticle tracking analysis. Changes in intracellular and EV-associated viral RNA were quantified using RT-qPCR, and changes in viral proteins, EV markers, and autophagy proteins were assessed by Western blot. Our data suggest that CBD significantly reduces the number of EVs released from infected cells and that this may be mediated by reducing viral transcription and autophagy activation. Therefore, CBD may exert a protective effect by alleviating the pathogenic effects of EVs in HIV-1 and CNS-related infections.

Use of Stem Cell Extracellular Vesicles as a "Holistic" Approach to CNS Repair.

Neurodegeneration is a hallmark of many diseases and disorders of the central nervous system (CNS). High levels of neuroinflammation are often associated with irreparable damage to CNS cells due to the dysregulation of signaling cascades that are unable to restore a homeostatic balance. Due to the inherent complexity of the CNS, development of CNS-related therapeutics has met limited success. While stem cell therapy has been evaluated in the context of CNS repair, the mechanisms responsible for their functional properties have not been clearly defined. In recent years, there has been growing interest in the use of stem cell extracellular vesicles (EVs) for the treatment of various CNS pathologies as these vesicles are believed to mediate many of the functional effects associated with their donor stem cells. The potency of stem cell EVs is believed to be largely driven by their biological cargo which includes various types of RNAs, proteins, and cytokines. In this review, we describe the characteristic properties of stem cell EVs and summarize their reported neuroprotective and immunomodulatory functions. A special emphasis is placed on the identification of specific biological cargo, including proteins and non-coding RNA molecules, that have been found to be associated with stem cell EVs. Collectively, this review highlights the potential of stem cell EVs as an alternative to traditional stem cell therapy for the repair of cellular damage associated with diverse CNS pathologies.

Transcription through the HIV-1 nucleosomes: effects of the PBAF complex in Tat activated transcription.

The SWI/SNF complex remodels nucleosomes, allowing RNA Polymerase II access to the HIV-1 proviral DNA. It has not been determined which SWI/SNF complex (BAF or PBAF) remodels nucleosomes at the transcription start site. These complexes differ in only three subunits and determining which subunit(s) is required could explain the regulation of Tat activated transcription. We show that PBAF is required for chromatin remodeling at the nuc-1 start site and transcriptional elongation. We find that Baf200 is required to ensure activation at the LTR level and for viral production. Interestingly, the BAF complex was observed on the LTR whereas PBAF was present on both LTR and Env regions. We found that Tat activated transcription facilitates removal of histones H2A and H2B at the LTR, and that the FACT complex may be responsible for their removal. Finally, the BAF complex may play an important role in regulating splicing of the HIV-1 genome.

Inhibition of human immunodeficiency virus type-1 by cdk inhibitors.

Current therapy for human immunodeficiency virus (HIV-1) infection relies primarily on the administration of anti-retroviral nucleoside analogues, either alone or in combination with HIV-protease inhibitors. Although these drugs have a clinical benefit, continuous therapy with the drugs leads to drug-resistant strains of the virus. Recently, significant progress has been made towards the development of natural and synthetic agents that can directly inhibit HIV-1 replication or its essential enzymes. We previously reported on the pharmacological cyclin-dependent kinase inhibitor (PCI) r-roscovitine as a potential inhibitor of HIV-1 replication. PCIs are among the most promising novel antiviral agents to emerge over the past few years. Potent activity on viral replication combined with proliferation inhibition without the emergence of resistant viruses, which are normally observed in HAART patients; make PCIs ideal candidates for HIV-1 inhibition. To this end we evaluated twenty four cdk inhibitors for their effect on HIV-1 replication in vitro. Screening of these compounds identified alsterpaullone as the most potent inhibitor of HIV-1 with activity at 150 nM. We found that alsterpaullone effectively inhibits cdk2 activity in HIV-1 infected cells with a low IC50 compared to control uninfected cells. The effects of alsterpaullone were associated with suppression of cdk2 and cyclin expression. Combining both alsterpaullone and r-roscovitine (cyc202) in treatment exhibited even stronger inhibitory activities in HIV-1 infected PBMCs.

9-Aminoacridine inhibition of HIV-1 Tat dependent transcription.

As part of a continued search for more efficient anti-HIV-1 drugs, we are focusing on the possibility that small molecules could efficiently inhibit HIV-1 replication through the restoration of p53 and p21WAF1 functions, which are inactivated by HIV-1 infection. Here we describe the molecular mechanism of 9-aminoacridine (9AA) mediated HIV-1 inhibition. 9AA treatment resulted in inhibition of HIV LTR transcription in a specific manner that was highly dependent on the presence and location of the amino moiety. Importantly, virus replication was found to be inhibited in HIV-1 infected cell lines by 9AA in a dose-dependent manner without inhibiting cellular proliferation or inducing cell death. 9AA inhibited viral replication in both p53 wildtype and p53 mutant cells, indicating that there is another p53 independent factor that was critical for HIV inhibition. p21WAF1 is an ideal candidate as p21WAF1 levels were increased in both p53 wildtype and p53 mutant cells, and p21WAF1 was found to be phosphorylated at S146, an event previously shown to increase its stability. Furthermore, we observed p21WAF1 in complex with cyclin T1 and cdk9 in vitro, suggesting a direct role of p21WAF1 in HIV transcription inhibition. Finally, 9AA treatment resulted in loss of cdk9 from the viral promoter, providing one possible mechanism of transcriptional inhibition. Thus, 9AA treatment was highly efficient at reactivating the p53 - p21WAF1 pathway and consequently inhibiting HIV replication and transcription.

Two specific drugs, BMS-345541 and purvalanol A induce apoptosis of HTLV-1 infected cells through inhibition of the NF-kappaB and cell cycle pathways.

Human T-cell leukemia virus type-1 (HTLV-1) induces adult T-cell leukemia/lymphoma (ATL/L), a fatal lymphoproliferative disorder, and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a chronic progressive disease of the central nervous system after a long period of latent infection. Although the mechanism of transformation and leukemogenesis is not fully elucidated, there is evidence to suggest that the viral oncoprotein Tax plays a crucial role in these processes through the regulation of several pathways including NF-kappaB and the cell cycle pathways. The observation that NF-kappaB, which is strongly induced by Tax, is indispensable for the maintenance of the malignant phenotype of HTLV-1 by regulating the expression of various genes involved in cell cycle regulation and inhibition of apoptosis provides a possible molecular target for these infected cells. To develop potential new therapeutic strategies for HTLV-1 infected cells, in this present study, we initially screened a battery of NF-kappaB and CDK inhibitors (total of 35 compounds) to examine their effects on the growth and survival of infected T-cell lines. Two drugs namely BMS-345541 and Purvalanol A exhibited higher levels of growth inhibition and apoptosis in infected cell as compared to uninfected cells. BMS-345541 inhibited IKKbeta kinase activity from HTLV-1 infected cells with an IC50 (the 50% of inhibitory concentration) value of 50 nM compared to 500 nM from control cells as measured by in vitro kinase assays. The effects of Purvalanol A were associated with suppression of CDK2/cyclin E complex activity as previously shown by us. Combination of both BMS-345541 and Purvalanol A showed a reduced level of HTLV-1 p19 Gag production in cell culture. The apparent apoptosis in these infected cells were associated with increased caspase-3 activity and PARP cleavage. The potent and selective apoptotic effects of these drugs suggest that both BMS-345541 and Purvalanol A, which target both NF-kappaB and CDK complex and the G1/S border, might be promising new agents in the treatment of these infected patients.

Anti-vpr activities of heat shock protein 27.

HIV-1 Vpr plays a pivotal role in viral pathogenesis and is preferentially targeted by the host immune system. In this report, we demonstrate that a small heat shock protein, HSP27, exhibits Vpr-specific antiviral activity, as its expression is specifically responsive to vpr gene expression and increased levels of HSP27 inhibit Vpr-induced cell cycle G2 arrest and cell killing. We further show that overexpression of HSP27 reduces viral replication in T-lymphocytes in a Vpr-dependent manner. Mechanistically, Vpr triggers HSP27 expression through heat shock factor (HSF) 1, but inhibits prolonged expression of HSP27 under heat-shock conditions. Together, these data suggest a potential dynamic and antagonistic interaction between HIV-1 Vpr and a host cell HSP27, suggesting that HSP27 may contribute to cellular intrinsic immunity against HIV infection.

Nuclear Factor 90(NF90) targeted to TAR RNA inhibits transcriptional activation of HIV-1.

BACKGROUND: Examination of host cell-based inhibitors of HIV-1 transcription may be important for attenuating viral replication. We describe properties of a cellular double-stranded RNA binding protein with intrinsic affinity for HIV-1 TAR RNA that interferes with Tat/TAR interaction and inhibits viral gene expression. RESULTS: Utilizing TAR affinity fractionation, North-Western blotting, and mobility-shift assays, we show that the C-terminal variant of nuclear factor 90 (NF90ctv) with strong affinity for the TAR RNA, competes with Tat/TAR interaction in vitro. Analysis of the effect of NF90ctv-TAR RNA interaction in vivo showed significant inhibition of Tat-transactivation of HIV-1 LTR in cells expressing NF90ctv, as well as changes in histone H3 lysine-4 and lysine-9 methylation of HIV chromatin that are consistent with the epigenetic changes in transcriptionally repressed gene. CONCLUSION: Structural integrity of the TAR element is crucial in HIV-1 gene expression. Our results show that perturbation Tat/TAR RNA interaction by the dsRNA binding protein is sufficient to inhibit transcriptional activation of HIV-1.

Antagonistic interaction of HIV-1 Vpr with Hsf-mediated cellular heat shock response and Hsp16 in fission yeast (Schizosaccharomyces pombe).

BACKGROUND: Expression of the HIV-1 vpr gene in human and fission yeast cells displays multiple highly conserved activities, which include induction of cell cycle G2 arrest and cell death. We have previously characterized a yeast heat shock protein 16 (Hsp16) that suppresses the Vpr activities when it is overproduced in fission yeast. Similar suppressive effects were observed when the fission yeast hsp16 gene was overexpressed in human cells or in the context of viral infection. In this study, we further characterized molecular actions underlying the suppressive effect of Hsp16 on the Vpr activities. RESULTS: We show that the suppressive effect of Hsp16 on Vpr-dependent viral replication in proliferating T-lymphocytes is mediated through its C-terminal end. In addition, we show that Hsp16 inhibits viral infection in macrophages in a dose-dependent manner. Mechanistically, Hsp16 suppresses Vpr activities in a way that resembles the cellular heat shock response. In particular, Hsp16 activation is mediated by a heat shock factor (Hsf)-dependent mechanism. Interestingly, vpr gene expression elicits a moderate increase of endogenous Hsp16 but prevents its elevation when cells are grown under heat shock conditions that normally stimulate Hsp16 production. Similar responsive to Vpr elevation of Hsp and counteraction of this elevation by Vpr were also observed in our parallel mammalian studies. Since Hsf-mediated elevation of small Hsps occurs in all eukaryotes, this finding suggests that the anti-Vpr activity of Hsps is a conserved feature of these proteins. CONCLUSION: These data suggest that fission yeast could be used as a model to further delineate the potential dynamic and antagonistic interactions between HIV-1 Vpr and cellular heat shock responses involving Hsps.

Identifying the membrane proteome of HIV-1 latently infected cells.

Profiling integral plasma membrane proteins is of particular importance for the identification of new biomarkers for diagnosis and for drug development. We report in this study the identification of surface markers by performing comparative proteomics of established human immunodeficiency virus-1 (HIV-1) latent cell models and parental cell lines. To this end we isolated integral membrane proteins using a biotin-directed affinity purification method. Isolated proteins were separated by two-dimensional gel electrophoresis and identified by matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) after in gel digestion. Seventeen different proteins were found to vary on the surface of T-cells due to HIV-1 infection. Of these proteins, 47% were integral membrane proteins, and 18% were membrane-associated. Through the use of complementary techniques such as Western blotting and fluorescent staining, we confirmed the differential expression of some of the proteins identified by MALDI-TOF including Bruton's tyrosine kinase and X-linked inhibitor of apoptosis. Finally, using phosphatidylinositol 3-kinase inhibitors and flavopiridol to inhibit Bruton's tyrosine kinase localization at the membrane and X-linked inhibitor of apoptosis protein expression, respectively, we showed that HIV-1 latently infected cells are more sensitive to these drugs than uninfected cells. This suggests that HIV-1 latently infected cells may be targeted with drugs that alter several pathways that are essential for the establishment and maintenance of latency.

Effect of SWI/SNF chromatin remodeling complex on HIV-1 Tat activated transcription.

BACKGROUND: Human immunodeficiency virus type 1 (HIV-1) is the etiologic agent of acquired immunodeficiency virus (AIDS). Following entry into the host cell, the viral RNA is reverse transcribed into DNA and subsequently integrated into the host genome as a chromatin template. The integrated proviral DNA, along with the specific chromatinized environment in which integration takes place allows for the coordinated regulation of viral transcription and replication. While the specific roles of and interplay between viral and host proteins have not been fully elucidated, numerous reports indicate that HIV-1 retains the ability for self-regulation via the pleiotropic effects of its viral proteins. Though viral transcription is fully dependent upon host cellular factors and the state of host activation, recent findings indicate a complex interplay between viral proteins and host transcription regulatory machineries including histone deacetylases (HDACs), histone acetyltransferases (HATs), cyclin dependent kinases (CDKs), and histone methyltransferases (HMTs). RESULTS: Here, we describe the effect of Tat activated transcription at the G1/S border of the cell cycle and analyze the interaction of modified Tat with the chromatin remodeling complex, SWI/SNF. HIV-1 LTR DNA reconstituted into nucleosomes can be activated in vitro using various Tat expressing extracts. Optimally activated transcription was observed at the G1/S border of the cell cycle both in vitro and in vivo, where chromatin remodeling complex, SWI/SNF, was present on the immobilized LTR DNA. Using a number of in vitro binding as well as in vivo chromatin immunoprecipitation (ChIP) assays, we detected the presence of both BRG1 and acetylated Tat in the same complex. Finally, we demonstrate that activated transcription resulted in partial or complete removal of the nucleosome from the start site of the LTR as evidenced by a restriction enzyme accessibility assay. CONCLUSION: We propose a model where unmodified Tat is involved in binding to the CBP/p300 and cdk9/cyclin T1 complexes facilitating transcription initiation. Acetylated Tat dissociates from the TAR RNA structure and recruits bromodomain-binding chromatin modifying complexes such as p/CAF and SWI/SNF to possibly facilitate transcription elongation.

Inhibition of HIV-1 virus replication using small soluble Tat peptides.

Although the introduction of highly active antiretroviral therapy (HAART) has led to a significant reduction in AIDS-related morbidity and mortality, unfortunately, many patients discontinue their initial HAART regimen, resulting in development of viral resistance. During HIV infection, the viral activator Tat is needed for viral progeny formation, and the basic and core domains of Tat are the most conserved parts of the protein. Here, we show that a Tat 41/44 peptide from the core domain can inhibit HIV-1 gene expression and replication. The peptides are not toxic to cells and target the Cdk2/Cyclin E complex, inhibiting the phosphorylation of serine 5 of RNAPII. Using the Cdk2 X-ray crystallography structure, we found that the low-energy wild-type peptides could bind to the ATP binding pocket, whereas the mutant peptide bound to the Cdk2 interface. Finally, we show that these peptides do not allow loading of the catalytic domain of the cdk/cyclin complex onto the HIV-1 promoter in vivo.

Therapeutic targets for HIV-1 infection in the host proteome.

BACKGROUND: Despite the success of HAART, patients often stop treatment due to the inception of side effects. Furthermore, viral resistance often develops, making one or more of the drugs ineffective. Identification of novel targets for therapy that may not develop resistance is sorely needed. Therefore, to identify cellular proteins that may be up-regulated in HIV infection and play a role in infection, we analyzed the effects of Tat on cellular gene expression during various phases of the cell cycle. RESULTS: SOM and k-means clustering analyses revealed a dramatic alteration in transcriptional activity at the G1/S checkpoint. Tat regulates the expression of a variety of gene ontologies, including DNA-binding proteins, receptors, and membrane proteins. Using siRNA to knock down expression of several gene targets, we show that an Oct1/2 binding protein, an HIV Rev binding protein, cyclin A, and PPGB, a cathepsin that binds NA, are important for viral replication following induction from latency and de novo infection of PBMCs. CONCLUSION: Based on exhaustive and stringent data analysis, we have compiled a list of gene products that may serve as potential therapeutic targets for the inhibition of HIV-1 replication. Several genes have been established as important for HIV-1 infection and replication, including Pou2AF1 (OBF-1), complement factor H related 3, CD4 receptor, ICAM-1, NA, and cyclin A1. There were also several genes whose role in relation to HIV-1 infection have not been established and may also be novel and efficacious therapeutic targets and thus necessitate further study. Importantly, targeting certain cellular protein kinases, receptors, membrane proteins, and/or cytokines/chemokines may result in adverse effects. If there is the presence of two or more proteins with similar functions, where only one protein is critical for HIV-1 transcription, and thus, targeted, we may decrease the chance of developing treatments with negative side effects.

Antiviral activity of CYC202 in HIV-1-infected cells.

There are currently 40 million individuals in the world infected with human immunodeficiency virus (HIV). The introduction of highly active antiretroviral therapy (HAART) has led to a significant reduction in AIDS-related morbidity and mortality. Unfortunately, up to 25% of patients discontinue their initial HAART regimen. Current HIV-1 inhibitors target the fusion of the virus to the cell and two viral proteins, reverse transcriptase and protease. Here, we examined whether other targets, such as an activated transcription factor, could be targeted to block HIV-1 replication. We specifically asked whether we could target a cellular kinase needed for HIV-1 transcription using CYC202 (R-roscovitine), a pharmacological cyclin-dependent kinase inhibitor. We targeted the cdk2-cyclin E complex in HIV-1-infected cells because both cdk2 and cyclin E are nonessential during mammalian development and are likely replaced by other kinases. We found that CYC202 effectively inhibits wild type and resistant HIV-1 mutants in T-cells, monocytes, and peripheral blood mononuclear cells at a low IC(50) and sensitizes these cells to enhanced apoptosis resulting in a dramatic drop in viral titers. Interestingly, the effect of CYC202 is independent of cell cycle stage and more specific for the cdk2-cyclin E complex. Finally, we show that cdk2-cyclin E is loaded onto the HIV-1 genome in vivo and that CYC202 is able to inhibit the uploading of this cdk-cyclin complex onto HIV-1 DNA. Therefore, targeting cellular enzymes necessary for HIV-1 transcription, which are not needed for cell survival, is a compelling strategy to inhibit wild type and mutant HIV-1 strains.

Anti-Vpr activity of a yeast chaperone protein.

Human immunodeficiency virus type 1 (HIV-1) viral protein R (Vpr) exerts multiple effects on viral and host cellular activities during viral infection, including nuclear transport of the proviral integration complex, induction of cell cycle G(2) arrest, and cell death. In this report, we show that a fission yeast chaperone protein Hsp16 inhibits HIV-1 by suppressing these Vpr activities. This protein was identified through three independent genome-wide screens for multicopy suppressors of each of the three Vpr activities. Consistent with the properties of a heat shock protein, heat shock-induced elevation or overproduction of Hsp16 suppressed Vpr activities through direct protein-protein interaction. Even though Hsp16 shows a stronger suppressive effect on Vpr in fission yeast than in mammalian cells, similar effects were also observed in human cells when fission yeast hsp16 was expressed either in vpr-expressing cells or during HIV-1 infection, indicating a possible highly conserved Vpr suppressing activity. Furthermore, stable expression of hsp16 prior to HIV-1 infection inhibits viral replication in a Vpr-dependent manner. Together, these data suggest that Hsp16 inhibits HIV-1 by suppressing Vpr-specific activities. This finding could potentially provide a new approach to studying the contribution of Vpr to viral pathogenesis and to reducing Vpr-mediated detrimental effects in HIV-infected patients.

Inhibition of HTLV-1 transcription by cyclin dependent kinase inhibitors.

HTLV-1 is the etiologic agent for adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), where viral replication and transformation are largely dependent upon modification of regulatory and host cell cycle proteins. The mechanism of HTLV-1 transformation appears to be distinct from that of many known chronic or acute leukemia viruses and is related to the viral activator Tax. Here we show that cyclin E, can associate tightly with the coactivator p300 and Pol II complex in HTLV-1 infected cells. The cyclin E associated complex is kinase active and phosphorylates the carboxy terminal domain of RNA Pol II. More importantly, p21/Waf1, a well-known cdk inhibitor at the G1/S border, inhibits transcription of HTLV-1 in both transfections and in in vitro transcription assays. Finally, specific cdk chemical inhibitors, functionally similar to cellular cdkIs, such as p21/Waf1 which inhibits cyclin E/cdk2 activity, also inhibit transcription of the HTLV-1 promoter. In particular, Purvalanol A, with an IC50 of 0.035 microm inhibits activated, but not basal transcription, as well as HTLV-1 infected cells. Collectively, the role of cyclin E/cdk2 in HTLV-1 infected cells and its involvement in RNA Pol II phosphorylation is discussed.