Identification of an arsenic-sensitive block to primate lentiviral infection of human dendritic cells

Down-regulation of RdRp complex and activated immune response due to increased arsenic level leads to decreased corona virus replication

Corona virus is pandemic and responsible for more than 5.6 million deaths. It was observed that its severity was reported in varied ways in different countries and even in different states of India. This variation was critically evaluated in the area with high contamination of Arsenic (As) to understand the arsenic toxicity and Covid epidemiology and associated health effects in the human population. It was reported that the area with low arsenic contamination has a very high incidence rate of Corona infection in the world. Even in the Indian scenario, high As-contaminated states like West Bengal, Jharkhand and Bihar, the incidence rate is 1.994%, 1.114% and 0.661%, respectively. In contrast, states with the least arsenic contamination have a very high corona incidence rate like 6.308, 17.289 and 4.351, respectively. It was evident that Arsenic inhibits the RdRp complex, which leads to the inhibition of viral genome replication. The PAMP associated pathway was activated by Arsenic and effectively bound with viral spike proteins leading to effective clearance of virus through activation of TNF alpha and IL-1. It finally leads to increased production of IgE, IgG and IGA. Arsenic also enhances inflammatory response against the virus through increased production of cytokine. The high arsenic level also induces apoptosis in viral infected cells through Bax/Bak pathway. It activates cytochrome-c and caspase-3 activity, inducing apoptosis in viral infected cells through PARP activation in the nucleus. These combined findings suggest that high arsenic contamination causes replication inhibition, activates an inflammatory response, increases antibody production, and finally leads to apoptosis through the mitochondrial pathway. People residing in arsenic hit areas are at a very low threat of corona infection.

Counteracting arsenic toxicity: Curcumin to the rescue?

Arsenicosis leads to various irreversible damages in several organs and is considered to be a carcinogen. The effects of chronic arsenic poisoning are a result of an imbalance between pro- and antioxidant homeostasis, oxidative stress, as well as DNA and protein damage. Curcumin, the polyphenolic pigment extracted from the rhizome of Curcuma longa, is well-known for its pleiotropic medicinal effects. Curcumin has been shown to have ameliorative effects in arsenic-induced genotoxicity, nephrotoxicity, hepatotoxicity, angiogenesis, skin diseases, reproductive toxicity, neurotoxicity, and immunotoxicity. This review aims to summarize the scientific evidence on arsenic toxicity in various organs and the ameliorative effects of curcumin on the arsenic toxicity.

Sulfonate-ended carbosilane dendrimers with a flexible scaffold cause inactivation of HIV-1 virions and gp120 shedding

Infection with human immunodeficiency virus type 1 (HIV-1) continues to be a global public health issue, especially in low-resource countries. Sexual transmission is responsible for the majority of HIV-1 infections worldwide. Women are more susceptible to HIV-1 acquisition than men and represent nearly 50% of the HIV-infected population. Topical vaginal microbicides that act at the earlier stages of infection offer a prevention strategy to reduce the acquisition of HIV-1. Dendrimers are nano-sized, radially symmetric molecules with a well-defined and monodisperse structure consisting of tree-like arms or branches. We perform a TZM.bl cell line-based screening of two families of carbosilane dendrimers (6 nanocompounds: G1-S12P, G2-S24P, G3-S48P, G1-C12P, G2-C24P and G3-C48P) that we have previously synthesized, containing 12, 24 or 48 sulfonate (or carboxylate) end-groups and a polyphenolic core. This work shows that second- and third-generation sulfonate-ended carbosilane dendrimers with a polyphenolic core (G2-S24P and G3-S48P, respectively) display low cytotoxicity (CC50 > 300 μM) with virucidal anti-R5-HIV-1 activity (EC50 < 50 nM; therapeutic index >6000) causing irreversible HIV-1 inactivation (80-90%) by loss of HIV-1 RNA (40%), gp120 shedding (70-80%) and p24 capsid protein release (45-60%). Herein, we demonstrate that sulfonate end-groups and a flexible scaffold from carbosilane dendrimers strongly influence their properties acting as potent virucides.

Characterization of two distinct early post-entry blocks to HIV-1 in common marmoset lymphocytes

In nature, primate lentiviruses infect humans and several Old World monkeys and apes. However, to date, lentiviruses infecting New World monkeys have not been described. We studied the susceptibility of common marmoset cells to HIV-1 infection and observed the presence of post-entry blocks to the early phase of HIV-1 infection in peripheral blood lymphocytes (PBLs) and a B lymphocytic cell line (B-LCL). The blocks present in these cells are dominant and phenotypically different from each other. In PBLs, the block occurs at the level of reverse transcription, reducing the accumulation of early and late transcripts, similar to the block imposed by TRIM5α. However, we have found that marmoset TRIM5α does not block HIV-1. In contrast, the restriction factor present in B-LCLs blocks HIV-1 replication at a later step, after nuclear entry, and inhibits integration. Additionally, we have identified an HIV-1 capsid mutant, N74D, that is able to escape the restriction in the marmoset B-LCLs. Our results suggest that the factors responsible for the blocks present in marmoset PBLs and B-LCLs are different. We propose the existence of at least two new restriction factors able to block HIV-1 infection in marmoset lymphocytes.

Activating transcription factor 4 underlies the pathogenesis of arsenic trioxide-mediated impairment of macrophage innate immune functions

Chronic arsenic exposure to humans is considered immunosuppressive with augmented susceptibility to several infectious diseases. The exact molecular mechanisms, however, remain unknown. Earlier, we showed the involvement of unfolded protein response (UPR) signaling in arsenic-mediated impairment of macrophage functions. Here, we show that activating transcription factor 4 (ATF4), a UPR transcription factor, regulates arsenic trioxide (ATO)-mediated dysregulation of macrophage functions. In ATO-treated ATF4(+/+) wild-type mice, a significant down-regulation of CD11b expression was associated with the reduced phagocytic functions of peritoneal and lung macrophages. This severe immuno-toxicity phenotype was not observed in ATO-treated ATF4(+/-) heterozygous mice. To confirm these observations, we demonstrated in Raw 264.7 cells that ATF4 knock-down rescues ATO-mediated impairment of macrophage functions including cytokine production, bacterial engulfment and clearance of engulfed bacteria. Sustained activation of ATF4 by ATO in macrophages induces apoptosis, while diminution of ATF4 expression protects against ATO-induced apoptotic cell death. Raw 264.7 cells treated with ATO also manifest dysregulated Ca(++) homeostasis. ATO induces Ca(++)-dependent calpain-1 and caspase-12 expression which together regulated macrophage apoptosis. Additionally, apoptosis was also induced by mitochondria-regulated pathway. Restoring ATO-impaired Ca(++) homeostasis in ER/mitochondria by treatments with the inhibitors of inositol 1,4,5-trisphosphate receptor (IP3R) and voltage-dependent anion channel (VDAC) attenuate innate immune functions of macrophages. These studies identify a novel role for ATF4 in underlying pathogenesis of macrophage dysregulation and immuno-toxicity of arsenic.

Antiviral mechanism of polyanionic carbosilane dendrimers against HIV-1

Nanotechnology-derived platforms, such as dendrimers, are very attractive in several biological applications. In the case of human immunodeficiency virus (HIV) infection, polyanionic carbosilane dendrimers have shown great potential as antiviral agents in the development of novel microbicides to prevent the sexual transmission of HIV-1. In this work, we studied the mechanism of two sulfated and naphthylsulfonated functionalized carbosilane dendrimers, G3-S16 and G2-NF16. They are able to inhibit viral infection at fusion and thus at the entry step. Both compounds impede the binding of viral particles to target cell surface and membrane fusion through the blockage of gp120–CD4 interaction. In addition, and for the first time, we demonstrate that dendrimers can inhibit cell-to-cell HIV transmission and difficult infectious synapse formation. Thus, carbosilane dendrimers’ mode of action is a multifactorial process targeting several proteins from viral envelope and from host cells that could block HIV infection at different stages during the first step of infection.

The interferon-induced antiviral protein PML (TRIM19) promotes the restriction and transcriptional silencing of lentiviruses in a context-specific, isoform-specific fashion

Background

The promyelocytic leukemia (PML) protein, a type I interferon (IFN-I)-induced gene product and a member of the tripartite motif (TRIM) family, modulates the transcriptional activity of viruses belonging to various families. Whether PML has an impact on the replication of HIV-1 has not been fully addressed, but recent studies point to its possible involvement in the restriction of HIV-1 in human cells and in the maintenance of transcriptional latency in human cell lines in which HIV-1 is constitutively repressed. We investigated further the restriction of HIV-1 and a related lentivirus, SIV_mac, by PML in murine cells and in a lymphocytic human cell line. In particular, we studied the relevance of PML to IFN-I-mediated inhibition and the role of individual human isoforms.

Results

We demonstrate that both human PML (hPML) and murine PML (mPML) inhibit the early post-entry stages of the replication of HIV-1 and a related lentivirus, SIV_mac. In addition, HIV-1 was transcriptionally silenced by mPML and by hPML isoforms I, II, IV and VI in MEFs. This PML-mediated transcriptional repression was attenuated in presence of the histone deacetylase inhibitor SAHA. In contrast, depletion of PML had no effect on HIV-1 gene expression in a human T cell line. PML was found to contribute to the inhibition of HIV-1 by IFN-I. Specifically, IFN-α and IFN-β treatments of MEFs enhanced the PML-dependent inhibition of HIV-1 early replication stages.

Conclusions

We show that PML can inhibit HIV-1 and other lentiviruses as part of the IFN-I-mediated response. The restriction takes place at two distinct steps, i.e. reverse transcription and transcription, and in an isoform-specific, cellular context-specific fashion. Our results support a model in which PML activates innate immune antilentiviral effectors. These data are relevant to the development of latency reversal-inducing pharmacological agents, since PML was previously proposed as a pharmacological target for such inhibitors. This study also has implications for the development of murine models of HIV-1.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-016-0253-1) contains supplementary material, which is available to authorized users.

The mechanistic basis of arsenicosis: pathogenesis of skin cancer

Significant amounts of arsenic have been found in the groundwater of many countries including Argentina, Bangladesh, Chile, China, India, Mexico, and the United States with an estimated 200 million people at risk of toxic exposure. Although chronic arsenic poisoning damages many organ systems, it usually first presents in the skin with manifestations including hyperpigmentation, hyperkeratoses, Bowen's disease, squamous cell carcinoma, and basal cell carcinoma. Arsenic promotes oxidative stress by upregulating nicotinamide adenine dinucleotide phosphate oxidase, uncoupling nitric oxide synthase, and by depleting natural antioxidants such as nitric oxide and glutathione in addition to targeting other proteins responsible for the maintenance of redox homeostasis. It causes immune dysfunction and tissue inflammatory responses, which may involve activation of the unfolded protein response signaling pathway. In addition, the dysregulation of other molecular targets such as nuclear factor kappa B, Hippo signaling protein Yap, and the mineral dust-induced proto-oncogene may orchestrate the pathogenesis of arsenic-mediated health effects. The metalloid decreases expression of tumor suppressor molecules and increases expression of pro-inflammatory mitogen-activated protein kinase pathways leading to a tumor-promoting tissue microenvironment. Cooperation of upregulated signal transduction molecules with DNA damage may abrogate apoptosis, promote proliferation, and enhance cell survival. Genomic instability via direct DNA damage and weakening of several cellular DNA repair mechanisms could also be important cancer development mechanisms in arsenic-exposed populations. Thus, arsenic mediates its toxicity by generating oxidative stress, causing immune dysfunction, promoting genotoxicity, hampering DNA repair, and disrupting signal transduction, which may explain the complex disease manifestations seen in arsenicosis.

As2O3 synergistically reactivate latent HIV-1 by induction of NF-κB

None of the current agents can safely and effectively eliminate latent HIV-1 reservoirs, meaning that there is a major barrier to the final cure of AIDS. Arsenic trioxide (As2O3), a drug used to treat acute promyelocytic leukemia (APL), was reported to affect the transcription factors and pathways involved in modulating HIV-1 expression. However, little is known about the effect and molecular basis of As2O3 in inducing HIV-1 expression in latently infected cells. Using the Jurkat T cell model of HIV-1 latency, we found that As2O3 activated latent HIV-1 replication with a similar potency to valproic acid (VPA) and did so in a dose- and time-dependent manner. We also found that As2O3 synergistically reactivated latent HIV-1 transcription with prostratin, tumor necrosis factor alpha (TNF-α) or VPA. Moreover, we provide evidence indicating that As2O3-induced HIV-1 activation involves the nuclear factor kappa B (NF-κB) signaling pathway. In conclusion, we have found that As2O3 can synergistically reactivate latent HIV-1 with other activators, which may provide a new tool to unravel the mechanisms of virus latency and reactivation.

Unfolded protein response (UPR) signaling regulates arsenic trioxide-mediated macrophage innate immune function disruption

Arsenic exposure is known to disrupt innate immune functions in humans and in experimental animals. In this study, we provide a mechanism by which arsenic trioxide (ATO) disrupts macrophage functions. ATO treatment of murine macrophage cells diminished internalization of FITC-labeled latex beads, impaired clearance of phagocytosed fluorescent bacteria and reduced secretion of pro-inflammatory cytokines. These impairments in macrophage functions are associated with ATO-induced unfolded protein response (UPR) signaling pathway characterized by the enhancement in proteins such as GRP78, p-PERK, p-eIF2α, ATF4 and CHOP. The expression of these proteins is altered both at transcriptional and translational levels. Pretreatment with chemical chaperon, 4-phenylbutyric acid (PBA) attenuated the ATO-induced activation in UPR signaling and afforded protection against ATO-induced disruption of macrophage functions. This treatment also reduced ATO-mediated reactive oxygen species (ROS) generation. Interestingly, treatment with antioxidant N-acetylcysteine (NAC) prior to ATO exposure, not only reduced ROS production and UPR signaling but also improved macrophage functions. These data demonstrate that UPR signaling and ROS generation are interdependent and are involved in the arsenic-induced pathobiology of macrophage. These data also provide a novel strategy to block the ATO-dependent impairment in innate immune responses.

Development of human dendritic cells and their role in HIV infection: antiviral immunity versus HIV transmission

Although dendritic cells (DCs) represent a small cell population in the body, they have been recognized as professional antigen presenting cells and key players of both innate and acquired immunity. The recent expansion of basic knowledge concerning differentiation and function of various DC subsets will greatly help to understand the nature of protective immunity required in designing acquired immunodeficiency syndrome (AIDS) vaccines. However, human immunodeficiency virus (HIV) not only targets CD4⁺ T cells but also myeloid cells, including macrophages and DC. When HIV infects DC, its replication is highly restricted in DC. Nevertheless, even a low level of HIV production is sufficient to enhance HIV replication in activated CD4⁺ T cells, through antigen presentation activity by HIV-infected DC. Considering how antiviral immunity is initiated and memory response is maintained, such efficient DC–T cell transmission of HIV should play an important role in the disturbed immune responses associated with HIV infection. Recently, accessory proteins encoded by HIV have been shown to interact with various proteins in DC, and thereby affect DC–T cell transmission. In this review, we summarize the current understanding about DC biology, antiviral immune responses and DC restriction factors, all of which will be important issues for the development of an effective AIDS vaccine in the future.

TLR-4 engagement of dendritic cells confers a BST-2/tetherin-mediated restriction of HIV-1 infection to CD4+ T cells across the virological synapse

Background

Dendritic cells and their subsets, located at mucosal surfaces, are among the first immune cells to encounter disseminating pathogens. The cellular restriction factor BST-2/tetherin (also known as CD317 or HM1.24) potently restricts HIV-1 release by retaining viral particles at the cell surface in many cell types, including primary cells such as macrophages. However, BST-2/tetherin does not efficiently restrict HIV-1 infection in immature dendritic cells.

Results

We now report that BST-2/tetherin expression in myeloid (myDC) and monocyte-derived dendritic cells (DC) can be significantly up-regulated by IFN-α treatment and TLR-4 engagement with LPS. In contrast to HeLa or 293T cells, infectious HIV-1 release in immature DC and IFN-α–matured DC was only modestly affected in the absence of Vpu compared to wild-type viruses. Strikingly, immunofluorescence analysis revealed that BST-2/tetherin was excluded from HIV containing tetraspanin-enriched microdomains (TEMs) in both immature DC and IFN-α–matured DC. In contrast, in LPS-mediated mature DC, BST-2/tetherin exerted a significant restriction in transfer of HIV-1 infection to CD4⁺ T cells. Additionally, LPS, but not IFN-α stimulation of immature DC, leads to a dramatic redistribution of cellular restriction factors to the TEM as well as at the virological synapse between DC and CD4⁺ T cells.

Conclusions

In conclusion, we demonstrate that TLR-4 engagement in immature DC significantly up-regulates the intrinsic antiviral activity of BST-2/tetherin, during cis-infection of CD4⁺ T cells across the DC/T cell virological synapse. Manipulating the function and potency of cellular restriction factors such as BST-2/tetherin to HIV-1 infection, has implications in the design of antiviral therapeutic strategies.

Role of glycosphingolipids in dendritic cell-mediated HIV-1 trans-infection

Glycosphingolipids (GSLs) are components of the cell membrane that comprise a membrane bound lipid, ceramide, coupled to an extracellular carbohydrate. GSLs impact numerous aspects of membrane biology, including membrane fluidity, curvature, and organization. The role of these molecules in both chronic inflammation and infectious disease and underlying pathogenic mechanisms are just starting to be recognized. As a component of the cell membrane, GSLs are also incorporated into lipid bilayers of diverse enveloped viruses as they bud out from the host cell and can go on to have a significant influence on viral pathogenesis. Dendritic cell (DC) subsets located in the peripheral mucosal tissues are proposed to be one of the earliest cell types that encounter transmitted viruses and help initiate adaptive immune responses against the invading pathogen by interacting with T cells. In turn, viruses, as obligatory intracellular parasites, rely on host cells for completing their replication cycle, and not surprisingly, HIV has evolved to exploit DC biology for the initial transmission event as well as for its dissemination and propagation within the infected host. In this review, we describe the mechanisms by which GSLs impact DC-mediated HIV trans-infection by either modulating virus infectivity, serving as a direct virus particle-associated host-derived ligand for specific interactions with DCs, or modulating the T cell membrane in such a way as to impact viral entry and thereby productive infection of CD4(+) T cells.

HIV-1 replication in monocyte-derived dendritic cells is stimulated by melarsoprol, one of the main drugs against human African trypanosomiasis

Human African trypanosomiasis (HAT) is a disease caused by the protozoan parasite Trypanosoma brucei, the causative agent of sleeping sickness that is still endemic in well defined regions of sub-Saharan Africa. Co-infections with this human pathogen and human immunodeficiency virus (HIV) are not uncommon, but their potential interaction has been little studied. The organo-arsenical drug melarsoprol has been widely used for the treatment of late stage trypanosomiasis since the early 1950s and is still widely used despite very serious adverse effects. Because arsenic trioxide, another trivalent arsenical structurally related to melarsoprol, has been shown to markedly increase HIV replication in dendritic cells (DCs), we tested the effect of melarsoprol on virus replication in various primary human immune cell types, including DCs. We show here that this medicinal drug stimulates the replication of several strains of HIV-1, specifically in monocyte-derived DCs, and also renders such cells susceptible to HIV-2 infection. The drug acts mainly through an increase in the efficacy of the reverse transcription process, and this effect is mediated, at least partly, by an inhibition of expression of the cellular restriction factor APOBEC3G. These observations raise concerns about the harmful effect that melarsoprol might exert on the natural history of HIV in co-infected patients and on virus transmission.

Arsenic modulates APOBEC3G-mediated restriction to HIV-1 infection in myeloid dendritic cells

DC are major targets of HIV-1 during the early events of infection. Yet, HIV-1 infects these cells only inefficiently in vitro as compared with CD4+T lymphocytes. Accordingly, we have previously identified a strong post-entry block to HIV-1 replication in MDDC as a result of the cellular restriction factor A3G. Furthermore, we have demonstrated that As₂O₃, a drug used to treat acute promyelocytic leukemia, can fully eliminate the potent post-entry restriction of HIV-1 infection in MDDC and in blood-derived MyDC by mechanisms that were unclear. We are now exploring the interplay between As₂O₃ and A3G-mediated restriction in primary DC subsets. Here, we report that As₂O₃ counteracts A3G-mediated restriction in MyDC but not in MDDC. RNAi of A3G in MyDC indicated that the As₂O₃-mediated increase of HIV-1 infection was largely dependent on the presence of the cellular restriction factor. This study reveals an unexpected interplay between As₂O₃ and A3G-mediated restriction to HIV-1 infection in primary human MyDC.

Vaccines and microbicides preventing HIV-1, HSV-2, and HPV mucosal transmission

HIV-1, herpes simplex virus type 2 (HSV-2), and human papillomavirus (HPV), among other sexually transmitted infections, represent a major burden for global health. Initial insights into the mucosal transmission of these viral pathogens have raised optimism with regard to the rapid generation of protective vaccines. Nevertheless, setbacks for HIV-1 and HSV-2 vaccines have seriously challenged the initial enthusiasm. Recently, two new vaccines that efficiently prevented HPV infection have renewed the hope that vaccinal prevention of viral mucosal sexually transmitted infections is possible. HIV-1 and HSV-2 differ from HPV, and each virus needs to be tackled with a distinct approach. However, vaccines are not the only possible answer. Topically applied agents (microbicides) are an attractive alternative in the prevention of HIV-1 and HSV-2 mucosal transmission. Progress in understanding the mechanisms of genital transmission of HIV-1 and HSV-2 is required for successful vaccine or microbicide candidates to emerge from current approaches.

TLR2 and TLR4 triggering exerts contrasting effects with regard to HIV-1 infection of human dendritic cells and subsequent virus transfer to CD4+ T cells

BACKGROUND

Recognition of microbial products through Toll-like receptors (TLRs) initiates inflammatory responses orchestrated by innate immune cells such as dendritic cells (DCs). As these cells are patrolling mucosal surfaces, a portal of entry for various pathogens including human immunodeficiency virus type-1 (HIV-1), we investigated the impact of TLR stimulation on productive HIV-1 infection of DCs and viral spreading to CD4+ T cells.

RESULTS

We report here that engagement of TLR2 on DCs increases HIV-1 transmission toward CD4+ T cells by primarily affecting de novo virus production by DCs. No noticeable and consistent effect was observed following engagement of TLR5, 7 and 9. Additional studies indicated that both HIV-1 infection of DCs and DC-mediated virus transmission to CD4+ T cells were reduced upon TLR4 triggering due to secretion of type-I interferons.

CONCLUSION

It can thus be proposed that exposure of DCs to TLR2-binding bacterial constituents derived, for example, from pathogens causing sexually transmissible infections, might influence the process of DC-mediated viral dissemination, a phenomenon that might contribute to a more rapid disease progression.

Glycosphingolipid composition of human immunodeficiency virus type 1 (HIV-1) particles is a crucial determinant for dendritic cell-mediated HIV-1 trans-infection

Interactions of human immunodeficiency virus type 1 (HIV-1) with dendritic cells (DCs) are multifactorial and presumably require nonredundant interactions between the HIV-1 envelope glycoprotein gp120 and molecules expressed on the DC surface that define the cellular fate of the virus particle. Surprisingly, neutralization of HIV-1 gp120-dependent binding interactions with DCs was insufficient to prevent HIV-1 attachment. Besides gp120, HIV-1 particles also incorporate host cell-derived proteins and lipids in their particle membrane. In this study, we demonstrate a crucial role for host cell-derived glycosphingolipids (GSLs) for the initial interactions of HIV-1 particles with both immature and mature DCs. Production of HIV-1 particles from virus producer cells treated with ceramide synthase inhibitor fumonisin B1 or glucosylceramide synthase inhibitor 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) resulted in the production of virus particles that, although capable of binding previously defined HIV-1 gp120-specific attachment factors CD4, DC-SIGN, and syndecans, were attenuated in their ability to be captured by both immature and mature DCs. Furthermore, GSL-deficient HIV-1 particles were inhibited in their ability to establish productive infections in DC-T-cell cocultures. These studies provide initial evidence for the role of HIV-1 particle membrane-associated GSLs in virus invasion of DCs and also provide additional novel cellular targets, GSL biosynthetic pathways and GSL-dependent HIV-1 interactions with DCs, for development of antiviral therapy.

Arsenic trioxide inhibits hepatitis C virus RNA replication through modulation of the glutathione redox system and oxidative stress

Arsenic trioxide (ATO), a therapeutic reagent used for the treatment of acute promyelocytic leukemia, has recently been reported to increase human immunodeficiency virus type 1 infectivity. However, in this study, we have demonstrated that replication of genome-length hepatitis C virus (HCV) RNA (O strain of genotype 1b) was notably inhibited by ATO at submicromolar concentrations without cell toxicity. RNA replication of HCV-JFH1 (genotype 2a) and the release of core protein into the culture supernatants were also inhibited by ATO after the HCV infection. To clarify the mechanism of the anti-HCV activity of ATO, we examined whether or not PML is associated with this anti-HCV activity, since PML is known to be a target of ATO. Interestingly, we observed the cytoplasmic translocation of PML after treatment with ATO. However, ATO still inhibited the HCV RNA replication even in the PML knockdown cells, suggesting that PML is dispensable for the anti-HCV activity of ATO. In contrast, we found that N-acetyl-cysteine, an antioxidant and glutathione precursor, completely and partially eliminated the anti-HCV activity of ATO after 24 h and 72 h of treatment, respectively. In this context, it is worth noting that we found an elevation of intracellular superoxide anion radical, but not hydrogen peroxide, and the depletion of intracellular glutathione in the ATO-treated cells. Taken together, these findings suggest that ATO inhibits the HCV RNA replication through modulation of the glutathione redox system and oxidative stress.

The C-type lectin surface receptor DCIR acts as a new attachment factor for HIV-1 in dendritic cells and contributes to trans- and cis-infection pathways

The dynamic interplay between dendritic cells (DCs) and human immunodeficiency virus type-1 (HIV-1) is thought to result in viral dissemination and evasion of antiviral immunity. Although initial observations suggested that the C-type lectin receptor (CLR) DC-SIGN was responsible for the trans-infection function of the virus, subsequent studies demonstrated that trans-infection of CD4(+) T cells with HIV-1 can also occur through DC-SIGN-independent mechanisms. We demonstrate that a cell surface molecule designated DCIR (for DC immunoreceptor), a member of a recently described family of DC-expressing CLRs, can participate in the capture of HIV-1 and promote infection in trans and in cis of autologous CD4(+) T cells from human immature monocyte-derived DCs. The contribution of DCIR to these processes was revealed using DCIR-specific siRNAs and a polyclonal antibody specific for the carbohydrate recognition domain of DCIR. Data from transfection experiments indicated that DCIR acts as a ligand for HIV-1 and is involved in events leading to productive virus infection. Finally, we show that the neck domain of DCIR is important for the DCIR-mediated effect on virus binding and infection. These results point to a possible role for DCIR in HIV-1 pathogenesis by supporting the productive infection of DCs and promoting virus propagation.