Drug 9AA reactivates p21/Waf1 and Inhibits HIV-1 progeny formation

HIV-1-related factors interact with p53 to influence cellular processes

Human immunodeficiency virus type 1 (HIV-1) is the primary epidemic strain in China. Its genome contains two regulatory genes (tat and rev), three structural genes (gag, pol, and env), and four accessory genes (nef, vpr, vpu, and vif). Long terminal repeats (LTRs) in thegenome regulate integration, duplication, and expression of viral gene. The permissibility of HIV-1 infection hinges on the host cell cycle status. HIV-1 replicates by exploiting various cellular processes via upregulation or downregulation of specific cellular proteins that also control viral pathogenesis. For example, HIV-1 regulates the life cycle of p53, which in turn contributes significantly to HIV-1 pathogenesis. In this article, we review the interaction between HIV-1-associated factors and p53, providing information on their regulatory and molecular mechanisms, hinting possible directions for further research.

Role of Divalent Cations in HIV-1 Replication and Pathogenicity

Divalent cations are essential for life and are fundamentally important coordinators of cellular metabolism, cell growth, host-pathogen interactions, and cell death. Specifically, for human immunodeficiency virus type-1 (HIV-1), divalent cations are required for interactions between viral and host factors that govern HIV-1 replication and pathogenicity. Homeostatic regulation of divalent cations' levels and actions appear to change as HIV-1 infection progresses and as changes occur between HIV-1 and the host. In people living with HIV-1, dietary supplementation with divalent cations may increase HIV-1 replication, whereas cation chelation may suppress HIV-1 replication and decrease disease progression. Here, we review literature on the roles of zinc (Zn2+), iron (Fe2+), manganese (Mn2+), magnesium (Mg2+), selenium (Se2+), and copper (Cu2+) in HIV-1 replication and pathogenicity, as well as evidence that divalent cation levels and actions may be targeted therapeutically in people living with HIV-1.

Recent advances in the identification of Tat-mediated transactivation inhibitors: progressing toward a functional cure of HIV

The current anti-HIV combination therapy does not eradicate the virus that persists mainly in quiescent infected CD4(+) T cells as a latent integrated provirus that resumes after therapy interruption. The Tat-mediated transactivation (TMT) is a critical step in the HIV replication cycle that could give the opportunity to reduce the size of latent reservoirs. More than two decades of research led to the identification of various TMT inhibitors. While none of them met the criteria to reach the market, the search for a suitable TMT inhibitor is still actively pursued. Really promising compounds, including one in a Phase III clinical trial, have been recently identified, thus warranting an update.

Select host restriction factors are associated with HIV persistence during antiretroviral therapy

OBJECTIVE

The eradication of HIV necessitates elimination of the HIV latent reservoir. Identifying host determinants governing latency and reservoir size in the setting of antiretroviral therapy (ART) is an important step in developing strategies to cure HIV infection. We sought to determine the impact of cell-intrinsic immunity on the HIV latent reservoir.

DESIGN

We investigated the relevance of a comprehensive panel of established anti-HIV-1 host restriction factors to multiple established virologic and immunologic measures of viral persistence in HIV-1-infected, ART-suppressed individuals.

METHODS

We measured the mRNA expression of 42 anti-HIV-1 host restriction factors, levels of cell-associated HIV-1 RNA, levels of total pol and 2-long terminal repeat (2-LTR) circle HIV-1 DNA and immunophenotypes of CD4 T cells in 72 HIV-1-infected individuals on suppressive ART (23 individuals initiated ART less than 1 year post-infection, and 49 individuals initiated ART greater than 1 year post-infection). Correlations were analysed using nonparametric tests.

RESULTS

The enhanced expression of a few select host restriction factors, p21, schlafen 11 and PAF1, was strongly associated with reduced CD4 T-cell associated HIV RNA during ART (P < 0.001). In addition, our data suggested that ART perturbs the regulatory relationship between CD4 T-cell activation and restriction factor expression. Lastly, cell-intrinsic immune responses were significantly enhanced in individuals who initiated ART during early versus chronic infection and may contribute to the reduced reservoir size observed in these individuals.

CONCLUSION

Intrinsic immune responses modulate HIV persistence during suppressive ART and may be manipulated to enhance the efficacy of ART and promote viral eradication through reversal of latency in vivo.

Eradication of HIV and Cure of AIDS, Now and How?

Recent studies have highlighted the importance of eradication of human immunodeficiency virus (HIV) and cure of acquired immunodeficiency syndrome (AIDS). However, a pivotal point that the patient immunity controls HIV reactivation after highly active anti-retroviral therapy [HAART or combination anti-retroviral therapy (cART)] remains less well addressed. In spite of the fact that both innate and adaptive immunities are indispensable and numerous cells participate in the anti-HIV immunity, memory CD4 T-cells are indisputably the key cells organizing all immune actions against HIV while being the targets of HIV. Here we present a view and multidisciplinary approaches to HIV/AIDS eradication and cure. We aim at memory CD4 T-cells, utilizing the stem cell properties of these cells to reprogram an anti-HIV memory repertoire to eliminate the viral reservoir, toward achieving an AIDS-free world.

Novel factors interfering with human immunodeficiency virus-type 1 replication in vivo and in vitro

The strategy of all retroviral infections is based on establishing an equilibrium between virus replication and proviral latency in the infected host. The human immunodeficiency virus-type 1 (HIV-1), belonging to the subfamily of lentiviridae, adds an additional level of sophistication to this general rule by encoding two regulatory genes (tat and rev) and four accessory genes (nef, vif, vpr and vpu); HIV-2, structurally similar to HIV-1 but characterized by lower pathogenicity in vivo, encodes another accessory gene, vpx. The function of these accessory genes has become clear in recent years: they serve as countermeasures to host-cell restriction factors that prevent or curtail the capacity of HIV to productively infect its target cells (typically, CD4+ T lymphocytes, macrophages and dendritic cells). Some of the best characterized restriction factors for HIV-1 are Tripartite Motif-5α (TRIM5α), preventing infection of nonhuman primates, although not being effective in humans, and apolipoprotein B mRNA-editing, enzyme-catalytic, polypeptide-like 3G (APOBEC 3G), counteracted by the viral accessory protein Vif. In addition, several other molecules are under scrutiny for their mechanism of action and potential exploitation as novel anti-HIV agents. This review will summarize the recently emerging knowledge on these novel factors and their potential relevance for the discovery of new anti-HIV agents targeting not only the replicative, but also the latent state of HIV infection.

Role of cellular iron and oxygen in the regulation of HIV-1 infection

Despite efficient antiretroviral therapy, eradication of HIV-1 infection is challenging and requires novel biological insights and therapeutic strategies. Among other physiological and environmental factors, intracellular iron greatly affects HIV-1 replication. Higher iron stores were shown to be associated with faster progression of HIV-1 infection and to inversely correlate with the survival of HIV-1 infected patients. Iron is required for several steps in the HIV-1 life cycle, including reverse transcription, HIV-1 gene expression and capsid assembly. Here, the authors present a comprehensive review of the molecular mechanisms involved in iron- and oxygen-mediated regulation of HIV-1 replication. We also propose key intracellular pathways that may be involved in regulating HIV-1 replication, via protein kinase complexes, CDK9/cyclin T1 and CDK 2/cyclin E, protein phosphatase-1 and other host factors.

Restriction of HIV-1 replication in macrophages and CD4+ T cells from HIV controllers

How HIV controllers (HICs) maintain undetectable viremia without therapy is unknown. The strong CD8(+) T-cell HIV suppressive capacity found in many, but not all, HICs may contribute to long-lasting viral control. However, other earlier defense mechanisms may be involved. Here, we examined intrinsic HIC cell resistance to HIV-1 infection. After in vitro challenge, monocyte-derived macrophages and anti-CD3-activated CD4(+) T cells from HICs showed low HIV-1 susceptibility. CD4 T-cell resistance was independent of HIV-1 coreceptors and affected also SIVmac infection. CD4(+) T cells from HICs expressed ex vivo higher levels of p21(Waf1/Cip1), which has been involved in the control of HIV-1 replication, than cells from control subjects. However, HIV restriction in anti-CD3-activated CD4(+) T cells and macrophages was not associated with p21 expression. Restriction inhibited accumulation of reverse transcripts, leading to reduction of HIV-1 integrated proviruses. The block could be overcome by high viral inocula, suggesting the action of a saturable mechanism. Importantly, cell-associated HIV-1 DNA load was extremely low in HICs and correlated with CD4(+) T-cell permissiveness to infection. These results point to a contribution of intrinsic cell resistance to the control of infection and the containment of viral reservoir in HICs.

Genome-wide association study identifies single nucleotide polymorphism in DYRK1A associated with replication of HIV-1 in monocyte-derived macrophages

BACKGROUND

HIV-1 infected macrophages play an important role in rendering resting T cells permissive for infection, in spreading HIV-1 to T cells, and in the pathogenesis of AIDS dementia. During highly active anti-retroviral treatment (HAART), macrophages keep producing virus because tissue penetration of antiretrovirals is suboptimal and the efficacy of some is reduced. Thus, to cure HIV-1 infection with antiretrovirals we will also need to efficiently inhibit viral replication in macrophages. The majority of the current drugs block the action of viral enzymes, whereas there is an abundance of yet unidentified host factors that could be targeted. We here present results from a genome-wide association study identifying novel genetic polymorphisms that affect in vitro HIV-1 replication in macrophages.

METHODOLOGY/PRINCIPAL FINDINGS

Monocyte-derived macrophages from 393 blood donors were infected with HIV-1 and viral replication was determined using Gag p24 antigen levels. Genomic DNA from individuals with macrophages that had relatively low (n = 96) or high (n = 96) p24 production was used for SNP genotyping with the Illumina 610 Quad beadchip. A total of 494,656 SNPs that passed quality control were tested for association with HIV-1 replication in macrophages, using linear regression. We found a strong association between in vitro HIV-1 replication in monocyte-derived macrophages and SNP rs12483205 in DYRK1A (p = 2.16 × 10(-5)). While the association was not genome-wide significant (p<1 × 10(-7)), we could replicate this association using monocyte-derived macrophages from an independent group of 31 individuals (p = 0.0034). Combined analysis of the initial and replication cohort increased the strength of the association (p = 4.84 × 10(-6)). In addition, we found this SNP to be associated with HIV-1 disease progression in vivo in two independent cohort studies (p = 0.035 and p = 0.0048).

CONCLUSIONS/SIGNIFICANCE

These findings suggest that the kinase DYRK1A is involved in the replication of HIV-1, in vitro in macrophages as well as in vivo.

HIV-1 and the macrophage

Macrophages and CD4+ T cells are natural target cells for HIV-1, and both cell types contribute to the establishment of the viral reservoir that is responsible for continuous residual virus replication during antiretroviral therapy and viral load rebound upon treatment interruption. Scientific findings that support a critical role for the infected monocyte/macrophage in HIV-1-associated diseases, such as neurological disorders and cardiovascular disease, are accumulating. To prevent or treat these HIV-1-related diseases, we need to halt HIV-1 replication in the macrophage reservoir. This article describes our current knowledge of how monocytes and certain macrophage subsets are able to restrict HIV-1 infection, in addition to what makes macrophages respond less well to current antiretroviral drugs as compared with CD4+ T cells. These insights will help to find novel approaches that can be used to meet this challenge.

Host hindrance to HIV-1 replication in monocytes and macrophages

Monocytes and macrophages are targets of HIV-1 infection and play critical roles in multiple aspects of viral pathogenesis. HIV-1 can replicate in blood monocytes, although only a minor proportion of circulating monocytes harbor viral DNA. Resident macrophages in tissues can be infected and function as viral reservoirs. However, their susceptibility to infection, and their capacity to actively replicate the virus, varies greatly depending on the tissue localization and cytokine environment. The susceptibility of monocytes to HIV-1 infection in vitro depends on their differentiation status. Monocytes are refractory to infection and become permissive upon differentiation into macrophages. In addition, the capacity of monocyte-derived macrophages to sustain viral replication varies between individuals. Host determinants regulate HIV-1 replication in monocytes and macrophages, limiting several steps of the viral life-cycle, from viral entry to virus release. Some host factors responsible for HIV-1 restriction are shared with T lymphocytes, but several anti-viral mechanisms are specific to either monocytes or macrophages. Whilst a number of these mechanisms have been identified in monocytes or in monocyte-derived macrophages in vitro, some of them have also been implicated in the regulation of HIV-1 infection in vivo, in particular in the brain and the lung where macrophages are the main cell type infected by HIV-1. This review focuses on cellular factors that have been reported to interfere with HIV-1 infection in monocytes and macrophages, and examines the evidences supporting their role in vivo, highlighting unique aspects of HIV-1 restriction in these two cell types.

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.

Novel HIV-1 therapeutics through targeting altered host cell pathways

The emergence of drug-resistant HIV-1 strains presents a challenge for the design of new drugs. Anti-HIV compounds currently in use are the subject of advanced clinical trials using either HIV-1 reverse transcriptase, viral protease or integrase inhibitors. Recent studies show an increase in the number of HIV-1 variants resistant to anti-retroviral agents in newly infected individuals. Targeting host cell factors involved in the regulation of HIV-1 replication might be one way to combat HIV-1 resistance to the currently available anti-viral agents. A specific inhibition of HIV-1 gene expression could be expected from the development of compounds targeting host cell factors that participate in the activation of the HIV-1 LTR promoter. Here we discuss how targeting the host can be accomplished either by using small molecules to alter the function of the host's proteins such as p53 or cdk9, or by utilizing new advances in siRNA therapies to knock down essential host factors such as CCR5 and CXCR4. Finally, we will discuss how the viral protein interactomes should be used to better design therapeutics against HIV-1.

The CDK inhibitor p21Cip1/WAF1 is induced by FcgammaR activation and restricts the replication of human immunodeficiency virus type 1 and related primate lentiviruses in human macrophages

Macrophages are major targets of human immunodeficiency virus type 1 (HIV-1). We have previously shown that aggregation of activating immunoglobulin G Fc receptors (FcgammaR) by immune complexes inhibits reverse transcript accumulation and integration of HIV-1 and related lentiviruses in monocyte-derived macrophages. Here, we show that FcgammaR-mediated restriction of HIV-1 is not due to enhanced degradation of incoming viral proteins or cDNA and is associated to the induction of the cyclin-dependent kinase inhibitor p21(Cip1/WAF1) (p21). Small interfering RNA-mediated p21 knockdown rescued viral replication in FcgammaR-activated macrophages and enhanced HIV-1 infection in unstimulated macrophages by increasing reverse transcript and integrated DNA levels. p21 induction by other stimuli, such as phorbol myristate acetate and the histone deacetylase inhibitor MS-275, was also associated with preintegrative blocks of HIV-1 replication in macrophages. Binding of p21 to reverse transcription/preintegration complex-associated HIV-1 proteins was not detected in yeast two-hybrid, pulldown, or coimmunoprecipitation assays, suggesting that p21 may affect viral replication independently of a specific interaction with an HIV-1 component. Consistently, p21 silencing rescued viral replication from the FcgammaR-mediated restriction also in simian immunodeficiency virus SIV(mac)- and HIV-2-infected macrophages. Our results point to a role of p21 as an inhibitory factor of lentiviral infection in macrophages and to its implication in FcgammaR-mediated restriction.

Chromatin dynamics associated with HIV-1 Tat-activated transcription

Chromatin remodeling is an essential event for HIV-1 transcription. Over the last two decades this field of research has come to the forefront, as silencing of the HIV-1 provirus through chromatin modifications has been linked to latency. Here, we focus on chromatin remodeling, especially in relation to the transactivator Tat, and review the most important and newly emerging studies that investigate remodeling mechanisms. We begin by discussing covalent modifications that can alter chromatin structure including acetylation, deacetylation, and methylation, as well as topics addressing the interplay between chromatin remodeling and splicing. Next, we focus on complexes that use the energy of ATP to remove or secure nucleosomes and can additionally act to control HIV-1 transcription. Finally, we cover recent literature on viral microRNAs which have been shown to alter chromatin structure by inducing methylation or even by remodeling nucleosomes.

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.

Small-molecule inhibitor which reactivates p53 in human T-cell leukemia virus type 1-transformed cells

Human T-cell leukemia virus type 1 (HTLV-1) is the etiologic agent of the aggressive and fatal disease adult T-cell leukemia. Previous studies have demonstrated that the HTLV-1-encoded Tax protein inhibits the function of tumor suppressor p53 through a Tax-induced NF-kappaB pathway. Given these attributes, we were interested in the activity of small-molecule inhibitor 9-aminoacridine (9AA), an anticancer drug that targets two important stress response pathways, NF-kappaB and p53. In the present study, we have examined the effects of 9AA on HTLV-1-transformed cells. Treatment of HTLV-1-transformed cells with 9AA resulted in a dramatic decrease in cell viability. Consistent with these results, we observed an increase in the percentage of cells in sub-G(1) and an increase in the number of cells positive by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling assay following treatment of HTLV-1-transformed cells with 9AA. In each assay, HTLV-1-transformed cells C8166, Hut102, and MT2 were more sensitive to treatment with 9AA than control CEM and peripheral blood mononuclear cells. Analyzing p53 function, we demonstrate that treatment of HTLV-1-transformed cells with 9AA resulted in an increase in p53 protein and activation of p53 transcription activity. Of significance, 9AA-induced cell death could be blocked by introduction of a p53 small interfering RNA, linking p53 activity and cell death. These results suggest that Tax-repressed p53 function in HTLV-1-transformed cells is "druggable" and can be restored by treatment with 9AA. The fact that 9AA induces p53 and inhibits NF-kappaB suggests a promising strategy for the treatment of HTLV-1-transformed cells.