Differential contribution of herpes simplex virus type 1 gene products and cellular factors to the activation of human immunodeficiency virus type 1 provirus.

We have previously reported that infection with herpes simplex virus type 1 (HSV-1) activates expression of the human immunodeficiency virus type 1 (HIV-1) provirus in T cells. Activation of the HIV-1 provirus correlated with the activation of binding of 55- and 85-kDa proteins to the kappa B enhancer and binding of the 50-kDa HLP-1 protein to the LBP-1 sequences of the HIV-1 long terminal repeat. Further examination of this system has shown that the inhibition of HSV-1 replication by the antiviral drug acyclovir does not inhibit HSV-1-mediated induction of HIV-1 provirus. Surprisingly, the NF-kappa B and HLP-1 binding activities were substantially inhibited in acyclovir-treated cells. In the transient-transfection assay, ICP0, but not ICP4, activated the HIV-1 long terminal repeat promoter region and the effect of ICP0 was greatly enhanced in the presence of the NF-kappa B binding proteins, suggesting that induction of the HIV-1 provirus involves cooperation between the HSV-1-activated cellular factor, NF-kappa B, and the virus-encoded transactivator, ICP0.     

Live covisualization of competing adeno-associated virus and herpes simplex virus type 1 DNA replication: molecular mechanisms of interaction

We performed live cell visualization assays to directly assess the interaction between competing adeno-associated virus (AAV) and herpes simplex virus type 1 (HSV-1) DNA replication. Our studies reveal the formation of separate AAV and HSV-1 replication compartments and the inhibition of HSV-1 replication compartment formation in the presence of AAV. AAV Rep is recruited into AAV replication compartments but not into those of HSV-1, while the single-stranded DNA-binding protein HSV-1 ICP8 is recruited into both AAV and HSV-1 replication compartments, although with differential staining patterns. Slot blot analysis of coinfected cells revealed a dose-dependent inhibition of HSV-1 DNA replication by wild-type AAV but not by rep-negative recombinant AAV. Consistent with this, Western blot analysis indicated that wild-type AAV affects the levels of the HSV-1 immediate-early protein ICP4 and the early protein ICP8 only modestly but strongly inhibits the accumulation of the late proteins VP16 and gC. Furthermore, we demonstrate that the presence of Rep in the absence of AAV DNA replication is sufficient for the inhibition of HSV-1. In particular, Rep68/78 proteins severely inhibit the formation of mature HSV-1 replication compartments and lead to the accumulation of ICP8 at sites of cellular DNA synthesis, a phenomenon previously observed in the presence of viral polymerase inhibitors. Taken together, our results suggest that AAV and HSV-1 replicate in separate compartments and that AAV Rep inhibits HSV-1 at the level of DNA replication.     

Mechanisms of human immunodeficiency virus type 1 inhibition by hydroxyurea

Virus life cycles depend on cellular factors. Therefore, targeting cellular in combination with viral enzymes could be an effective control in virus replication. In contrast to viral proteins, cellular proteins are not prone to mutations; therefore, viral escape is not expected from drugs inhibiting cellular factors. Hydroxyurea inhibits the cellular enzyme ribonucleotide reductase, thus reducing DNA synthesis. Furthermore, this drug potentiates the activity of nucleoside analogues, inhibits the escape of A-analogue resistant mutants, and increases the phosphorylation of T-analogues. Besides its antiviral activity, hydroxyurea effects the immune system by decreasing immune activation, inhibiting the expansion of CD8 cells and the depletion of CD4 cells. Hydroxyurea has been used in medicine for 40 years, is well tolerated, and it is the least expensive available anti-HIV-1 drug. These characteristics make hydroxyurea a primary candidate for use in combination therapies for the treatment of HIV-1 infection.     

The differential requirement for cyclin-dependent kinase activities distinguishes two functions of herpes simplex virus type 1 ICP0

Herpes simplex virus type 1 (HSV-1) ICP0 directs the degradation of cellular proteins associated with nuclear structures called ND10, a function thought to be closely associated with its broad transactivating activity. Roscovitine (Rosco), an inhibitor of cyclin-dependent kinases (cdks), inhibits the replication of HSV-1, HSV-2, human cytomegalovirus, varicella-zoster virus, and human immunodeficiency virus type 1 by inhibiting specific steps or activities of viral regulatory proteins, indicating the broad and pleiotropic effects that cdks have on the replication of these viruses. We previously demonstrated that Rosco inhibits the transactivating activity of ICP0. In the present study, we asked whether Rosco also affects the ability of ICP0 to direct the degradation of ND10-associated proteins. For this purpose, WI-38 cells treated with cycloheximide (CHX) were mock infected or infected with wild-type HSV-1 or an ICP0(-) mutant (7134). After release from the CHX block, the infections were allowed to proceed for 2 h in the presence or absence of Rosco at a concentration known to inhibit ICP0's transactivating activity. The cells were then examined for the presence of ICP0 and selected ND10-associated antigens (promyelocytic leukemia antigen [PML], sp100, hDaxx, and NDP55) by immunofluorescence. Staining for the ND10-associated antigens was detected in 90% of 7134- and mock-infected cells stained positive for all ND10-associated antigens in the presence or absence of Rosco. Similar results were obtained with a non-ND10-associated antigen, DNA-PK(cs), a known target of ICP0-directed degradation. The results of the PML and DNA-PK(cs) immunofluorescence studies correlated with a decrease in the levels of these proteins as determined by Western blotting. Thus, the differential requirement for Rosco-sensitive cdk activities distinguishes ICP0's ability to direct the dispersal or degradation of cellular proteins from its transactivating activity.     

The inhibitory effect of essential oils on herpes simplex virus type-1 replication in vitro

The antiviral effect of 12 essential oils on herpes simplex virus type-1 (HSV-1) replication was examined in vitro. The replication ability of HSV-1 was suppressed by incubation of HSV-1 with 1% essential oils at 4 C for 24 hr. Especially, lemongrass completely inhibited the viral replication even at a concentration of 0.1%, and its antiviral activity was dependent on the concentrations of the essential oil. When Vero cells were treated with the essential oil before or after viral adsorption, no antiviral activity was found, which suggests that the antiviral activity of essential oils including lemongrass may be due to the direct interaction with virions.     

Physical interaction between the herpes simplex virus type 1 exonuclease, UL12, and the DNA double-strand break-sensing MRN complex

The herpes simplex virus type 1 (HSV-1) alkaline nuclease, encoded by the UL12 gene, plays an important role in HSV-1 replication, as a UL12 null mutant displays a severe growth defect. The HSV-1 alkaline exonuclease UL12 interacts with the viral single-stranded DNA binding protein ICP8 and promotes strand exchange in vitro in conjunction with ICP8. We proposed that UL12 and ICP8 form a two-subunit recombinase reminiscent of the phage lambda Red α/β recombination system and that the viral and cellular recombinases contribute to viral genome replication through a homologous recombination-dependent DNA replication mechanism. To test this hypothesis, we identified cellular interaction partners of UL12 by using coimmunoprecipitation. We report for the first time a specific interaction between UL12 and components of the cellular MRN complex, an important factor in the ATM-mediated homologous recombination repair (HRR) pathway. This interaction is detected early during infection and does not require viral DNA or other viral or cellular proteins. The region of UL12 responsible for the interaction has been mapped to the first 125 residues, and coimmunoprecipitation can be abolished by deletion of residues 100 to 126. These observations support the hypothesis that cellular and viral recombination factors work together to promote efficient HSV-1 growth.     

Mode of action of SDZ NIM 811, a nonimmunosuppressive cyclosporin A analog with activity against human immunodeficiency virus (HIV) type 1: interference with HIV protein-cyclophilin A interactions.

Cyclosporins, in particular the nonimmunosuppressive derivative SDZ NIM 811, exhibit potent anti-human immunodeficiency virus type 1 (HIV-1) activity in vitro. SDZ NIM 811 interferes at two stages of the viral replication cycle: (i) translocation of the preintegration complex to the nucleus and (ii) production of infectious virus particles. Immunosuppressive activity is not correlated with anti-HIV-1 activity of cyclosporins. However, binding to cyclophilin A, the major cellular receptor protein of cyclosporins, is a prerequisite for HIV inhibition: all structural changes of the cyclosporin A molecule leading to loss of affinity to cyclophilin abolished the antiviral effect. Cyclosporin derivatives did not interact directly with HIV-1 proteins; cyclophilin was the only detectable receptor protein for antivirally active cyclosporins. There is no evidence that inhibition of HIV occurs via a gain of function of cyclophilin in the presence of cyclosporins: the complex of cyclophilin A with SDZ NIM 811 does not bind to calcineurin or to any other viral or cellular proteins under conditions in which calcineurin binding to the cyclophilin A-cyclosporin A complex is easily detectable. Thus, the loss of function caused by binding of cyclosporins to cyclophilin seems to be sufficient for the anti-HIV effect. Cyclophilin A was demonstrated to bind to HIV-1 p24gag, and the formation of complexes was blocked by cyclosporins with 50% inhibitory concentrations of about 0.7 microM. HIV-2 and simian immunodeficiency virus are only weakly or not at all inhibited by cyclosporins. For gag-encoded proteins derived from HIV-1, HIV-2, or simian immunodeficiency virus particles, cyclophilin-binding capacity correlated with sensitivity of the viruses to inhibition by cyclosporins. Cyclophilin A also binds to HIV-1 proteins other than gag-encoded proteins, namely, p17gag, Nef, Vif, and gp120env; the biological significance of these interactions is questionable. We conclude that HIV-1 Gag-cyclophilin A interaction may be essential in HIV-1 replication, and interference with this interaction may be the molecular basis for the antiviral activity of cyclosporins.     

Pyrrolidine Dithiocarbamate Inhibits Herpes Simplex Virus 1 and 2 Replication,and Its Activity May Be Mediated through Dysregulation of the Ubiquitin-Proteasome System

Pyrrolidine dithiocarbamate (PDTC) is widely used as an antioxidant or an NF-κB inhibitor. It has been reported to inhibit the replication of human rhinoviruses, poliovirus, coxsackievirus, and influenza virus. In this paper, we report that PDTC could inhibit the replication of herpes simplex virus 1 and 2 (HSV-1 and HSV-2). PDTC suppressed the expression of HSV-1 and HSV-2 viral immediate early (IE) and late (membrane protein gD) genes and the production of viral progeny. This antiviral property was mediated by the dithiocarbamate moiety of PDTC and required the presence of Zn²⁺. Although PDTC could potently block reactive oxygen species (ROS) generation, it was found that this property did not contribute to its anti-HSV activity. PDTC showed no activity in disrupting the mitogen-activated protein kinase (MAPK) pathway activation induced by viral infection that was vital for the virus''s propagation. We found that PDTC modulated cellular ubiquitination and, furthermore, influenced HSV-2-induced IκB-α degradation to inhibit NF-κB activation and enhanced PML stability in the nucleus, resulting in the inhibition of viral gene expression. These results suggested that the antiviral activity of PDTC might be mediated by its dysregulation of the cellular ubiquitin-proteasome system (UPS).     

Inhibiting the Arp2/3 complex limits infection of both intracellular mature vaccinia virus and primate lentiviruses

Characterizing cellular factors involved in the life cycle of human immunodeficiency virus type 1 (HIV-1) is an initial step toward controlling replication of HIV-1. Actin polymerization mediated by the Arp2/3 complex has been found to play a critical role in some pathogens' intracellular motility. We have asked whether this complex also contributes to the viral life cycles including that of HIV-1. We have used both the acidic domains from actin-related protein (Arp) 2/3 complex-binding proteins such as the Wiscott-Aldrich syndrome protein (N-WASP) or cortactin, and siRNA directing toward Arp2 to inhibit viral infection. HIV-1, simian immunodeficiency virus (SIV), and intracellular mature vaccinia virus (IMV) were sensitive to inhibition of the Arp2/3 complex, whereas MLV, HSV-1, and adenovirus were not. Interestingly, pseudotyping HIV-1 with vesicular stomatitis virus G protein (VSV-G) overcame this inhibition. Constitutive inhibition of the Arp2/3 complex in the T-cell line H9 also blocked replication of HIV-1. These data suggested the existence of an Arp2/3 complex-dependent event during the early phase of the life cycles of both primate lentiviruses and IMV. Inhibiting the HIV-1's ability to activate Arp2/3 complex could be a potential chemotherapeutic intervention for acquired immunodeficiency syndrome (AIDS).     

The herpes simplex virus ICP0 RING finger domain inhibits IRF3- and IRF7-mediated activation of interferon-stimulated genes

Virus infection induces a rapid cellular response in cells characterized by the induction of interferon. While interferon itself does not induce an antiviral response, it activates a number of interferon-stimulated genes that collectively function to inhibit virus replication and spread. Previously, we and others reported that herpes simplex virus type 1 (HSV-1) induces an interferon -independent antiviral response in the absence of virus replication. Here, we report that the HSV-1 proteins ICP0 and vhs function in concert to disable the host antiviral response. In particular, we show that ICP0 blocks interferon regulatory factor IRF3- and IRF7-mediated activation of interferon-stimulated genes and that the RING finger domain of ICP0 is essential for this activity. Furthermore, we demonstrate that HSV-1 modifies the IRF3 pathway in a manner different from that of the small RNA viruses most commonly studied.     

Potent inhibition of human immunodeficiency virus type 1 in primary T cells and alveolar macrophages by a combination anti-Rev strategy delivered in an adeno-associated virus vector.

The rate of viral replication appears to play a pivotal role in human immunodeficiency virus type 1 (HIV-1) pathogenesis and disease progression as it outstrips the capacity of the immune system to respond. Important cellular sites for HIV-1 production include T lymphocytes and tissue macrophages. Antiviral strategies, including newer treatment modalities such as gene therapy of HIV-1-susceptible cell populations, must be capable of engendering durable inhibitory effects to HIV-1 replication in both of these primary cell types in order to be effective. Among the potential genetic targets for intervention in the HIV-1 life cycle, the Rev regulatory system, consisting of Rev and its binding site, the Rev-responsive element (RRE), stands out as particularly attractive. Rev is essential for maintaining the stability of the viral genomic RNA as well as viral mRNAs encoding key structural and regulatory proteins. Moreover, it exhibits favorable threshold kinetics, in that Rev concentrations must rise above a critical level to exert their effect. To disable Rev function, primary T cells or macrophages were transduced with anti-Rev single-chain immunoglobulin (SFv) or RRE decoy genes either singly or in combination by employing adeno-associated virus vectors and then challenged with HIV-1. By directing both a protein and a nucleic acid against the normal interaction between Rev and the RRE, this genetic antiviral strategy effectively inhibited infection by either clinical or laboratory virus isolates. These results provide a framework for novel interventions to reduce virus production in the infected host.     

Ubiquitination and deubiquitination of NP protein regulates influenza A virus RNA replication

Influenza A virus RNA replication requires an intricate regulatory network involving viral and cellular proteins. In this study, we examined the roles of cellular ubiquitinating/deubiquitinating enzymes (DUBs). We observed that downregulation of a cellular deubiquitinating enzyme USP11 resulted in enhanced virus production, suggesting that USP11 could inhibit influenza virus replication. Conversely, overexpression of USP11 specifically inhibited viral genomic RNA replication, and this inhibition required the deubiquitinase activity. Furthermore, we showed that USP11 interacted with PB2, PA, and NP of viral RNA replication complex, and that NP is a monoubiquitinated protein and can be deubiquitinated by USP11 in vivo. Finally, we identified K184 as the ubiquitination site on NP and this residue is crucial for virus RNA replication. We propose that ubiquitination/deubiquitination of NP can be manipulated for antiviral therapeutic purposes.     

ND10 components relocate to sites associated with herpes simplex virus type 1 nucleoprotein complexes during virus infection

Infections with DNA viruses commonly result in the association of viral genomes and replication compartments with cellular nuclear substructures known as promyelocytic leukemia protein (PML) nuclear bodies or ND10. While there is evidence that viral genomes can associate with preexisting ND10, we demonstrate in this study by live-cell microscopy that structures resembling ND10 form de novo and in association with viral genome complexes during the initial stages of herpes simplex virus type 1 (HSV-1) infection. Consistent with previous studies, we found that the major ND10 proteins PML, Sp100, and hDaxx are exchanged very rapidly between ND10 foci and the surrounding nucleoplasm in live cells. The dynamic nature of the individual protein molecule components of ND10 provides a mechanism by which ND10 proteins can be recruited to novel sites during virus infection. These observations explain why the genomes and replication compartments of DNA viruses that replicate in the cell nucleus are so commonly found in association with ND10. These findings are discussed with reference to the nature, location, and potential number of HSV-1 prereplication compartments and to the dynamic aspects of HSV-1 genomes and viral products during the early stages of lytic infection.