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PubMed1998

Superantigen-activated T cells redirected by a bispecific antibody inhibit vesicular stomatitis virus replication in vitro and in vivo.

A bispecific Ab (BsAb) that binds the TCR on T cells and the G protein of the vesicular stomatitis virus (VSV) can redirect staphylococcal enterotoxin B (SEB)-activated T cells to kill VSV-infected cells and to inhibit VSV replication in vitro. Inhibition of virus replication in our system is dependent upon the specificity of the Ab for the viral protein. IFN-gamma does not play a very important role in this phenomenon, which is mainly mediated by the release of Pfp from CD8+ T cells. We have used a Stat1 knockout mouse model in which VSV infection is lethal. Infusion of staphylococcal enterotoxin-activated B T cells and bispecific Ab significantly slowed virus progression and prolonged the survival of VSV-infected Stat1 knockout mice in vivo.

Animals↗

PubMed1989

Preliminary evidence that azidothymidine does not affect hepatitis B virus replication in acquired immunodeficiency syndrome (AIDS) patients.

The effect of azidothymidine (AZT) on hepatitis B virus (HBV) replication was determined in three patients with the acquired immunodeficiency syndrome (AIDS). Serum viral DNA was present, and its concentration either remained the same or increased in two patients. Since AIDS patients may be infected with a variety of viral agents in addition to the human immunodeficiency virus (HIV), the effects of the antiviral agents and biological modifiers on other common viral infections should also be determined in developing new approaches to HIV infection. Our results give preliminary evidence that AZT does not affect HBV viral replication in vivo.

Acquired Immunodeficiency Syndrome↗

PubMed1996

Long-term human T-cell culture system supporting hepatitis C virus replication.

We recently found that human T-cell leukemia virus type I-infected cloned MT-2C cells could support the replication of hepatitis C virus (HCV) up to 30 days postinoculation (p.i.). To obtain a more persistent HCV replication system using MT-2C cells, we examined the effect of various culture conditions after virus inoculation. We found that persistent HCV infection (at least 80 days) could be reproducibly achieved by reducing the temperature from 37 degrees C to 32 degrees C. Under this culture condition, HCV RNA could be detected in the cells up to 198 days p.i. Sequence analysis of HCV hypervariable region 1 revealed that certain HCV species became predominant during the culture period. We also demonstrated that virus transmission by the cell-free mode could be successfully repeated at least 4 times at 32 degrees C as opposed to only twice at 37 degrees C. This HCV-infected culture system will be useful for the various biological studies, including investigations into the mechanisms of HCV replication and multiplication.

Amino Acid Sequence↗

PubMed1998

Inhibition of hepatitis B virus replication during adenovirus and cytomegalovirus infections in transgenic mice.

We have previously demonstrated that hepatitis B virus (HBV) replication and gene expression are abolished in the livers of HBV transgenic mice by cytotoxic T lymphocytes (CTLs) and during lymphocytic choriomeningitis virus (LCMV) infection, stimuli that trigger the production of alpha/beta interferon, gamma interferon, and tumor necrosis factor alpha in the liver. We now report that hepatic HBV replication and gene expression are inhibited by the local induction of these cytokines during adenovirus- and murine cytomegalovirus (MCMV)-induced hepatitis. Further, we show that MCMV also blocks HBV replication and gene expression in the proximal convoluted tubules of the kidney by causing interstitial nephritis and inducing the same cytokines in the renal parenchyma. These results suggest that inflammatory cytokines probably contribute to viral clearance during acute viral hepatitis in humans, and they imply that induction of these cytokines in the liver and other infected tissues of chronically infected patients might have therapeutic value.

Adenoviruses, Human↗

PubMed2005

Suppression of hepatitis C virus replication by cyclosporin a is mediated by blockade of cyclophilins.

BACKGROUND & AIMS: Cyclosporin A specifically suppresses hepatitis C virus (HCV) replication in vitro at clinically achievable concentrations. In this study, we investigated the mechanisms of action of cyclosporin A against HCV replication. METHODS: The in vitro effects of cyclosporin A on HCV replication were analyzed using an HCV replicon system that expresses chimeric luciferase reporter protein. RESULTS: The significant effects of cyclosporin A on expression of an HCV replicon and the absence of such effects of FK506, which shares mechanisms of action with cyclosporin A, suggested the involvement of intracellular ligands of cyclosporin A, the cyclophilins. Transient and stable knockdown of the expression of cytoplasmic cyclophilins A, B, and C by short hairpin RNA-expressing vectors suppressed HCV replication significantly. A cyclosporin analogue, cyclosporin D, which lacks immunosuppressive activity but exhibits cyclophilin binding, induced a similar suppression of HCV replication. Furthermore, cyclosporin A treatment of Huh7 cells induced an unfolded protein response exemplified by expression of cellular BiP/GRP78. Treatment of cells with thapsigargin and mercaptoethanol, which induce the unfolded protein responses, suppressed HCV replication, suggesting that the cyclosporin-induced unfolded protein responses might contribute to the suppression of HCV protein processing and replication. CONCLUSIONS: The anti-HCV activity of cyclosporin A is mediated through a specific blockade of cyclophilins, and these molecules may constitute novel targets for anti-HCV therapeutics.

Base Sequence↗

PubMed1993

[Strategy of viral replication].

Virus replication is a multistep process which is realized mostly by virus-coded enzymes and in a small part by cell-coded enzymes. Affection of the virus-coded enzymes can be, and is, utilized to restrict virus replication without damaging the host cell. The article provides basic information on the most important steps of viral replication and processes which can be affected in the course of antiviral therapy.

Virus Replication↗

PubMed1994

The effects of cytomegalovirus on human immunodeficiency virus replication in brain-derived cells correlate with permissiveness of the cells for each virus.

Human cytomegalovirus (HCMV) is commonly found in the brains of patients with AIDS and in some cases can be detected in the same cells as can human immunodeficiency virus type 1 (HIV-1). In this study, we analyzed the patterns of replication of HIV-1 and HCMV in singly infected cells and the effects of dual infection in human brain-derived cell lines of three different origins: neuroblastoma cell lines SK-N-MC and SY5Y; astrocytoma/glioblastoma cell lines U373-MG and Hs 683; and undifferentiated glioblastoma cell lines A172 and T98G. To bypass the restriction at the adsorption/penetration step in these CD4-negative cells, we used HIV-1 (amphotropic retrovirus) pseudotypes. These HIV-1 pseudotypes infected the majority of the cells in the cultures and expressed high levels of HIV-1 gene products in all except the SY5Y cells. The cell lines differed in the ability to support HCMV infection, but coinfection with HIV-1 had no effect on HCMV replication. The A172 cells were completely nonpermissive for HCMV gene expression, while HCMV replication in the singly infected T98G and SK-N-MC cell lines was restricted at the level of some early gene products. This resulted in complete and partial inhibition, respectively, of viral DNA synthesis. Dual infection of the A172, T98G, and SK-N-MC cells had no effect on HIV-1 replication. The other three cell lines, U373-MG, Hs 683, and SY5Y, were fully permissive for HCMV replication. In the U373-MG and Hs 683 cells, HCMV markedly inhibited the synthesis of HIV-1 gene products. In contrast, a transient stimulation of HIV-1 production followed by a repression was observed in the dually infected SY5Y cells. We conclude from these results that under conditions in which both HIV-1 and HCMV can undergo fully permissive infection, HCMV can repress HIV-1 gene expression. In cells in which HCMV replication is limited but HIV-1 replicates well, there is no effect on HIV-1 gene expression. However, activation of HIV-1, at least transiently, may occur in cells in which HIV-1 gene expression is limited. These studies suggest that a threshold level of some HIV-1 gene product(s) may obscure activation or promote repression of HIV replication by HCMV.

Antigens, Viral↗

PubMed2002

Increased RNA editing and inhibition of hepatitis delta virus replication by high-level expression of ADAR1 and ADAR2.

Hepatitis delta virus (HDV) is a subviral human pathogen that uses specific RNA editing activity of the host to produce two essential forms of the sole viral protein, hepatitis delta antigen (HDAg). Editing at the amber/W site of HDV antigenomic RNA leads to the production of the longer form (HDAg-L), which is required for RNA packaging but which is a potent trans-dominant inhibitor of HDV RNA replication. Editing in infected cells is thought to be catalyzed by one or more of the cellular enzymes known as adenosine deaminases that act on RNA (ADARs). We examined the effects of increased ADAR1 and ADAR2 expression on HDV RNA editing and replication in transfected Huh7 cells. We found that both ADARs dramatically increased RNA editing, which was correlated with strong inhibition of HDV RNA replication. While increased HDAg-L production was the primary mechanism of inhibition, we observed at least two additional means by which ADARs can suppress HDV replication. High-level expression of both ADAR1 and ADAR2 led to extensive hyperediting at non-amber/W sites and subsequent production of HDAg variants that acted as trans-dominant inhibitors of HDV RNA replication. Moreover, we also observed weak inhibition of HDV RNA replication by mutated forms of ADARs defective for deaminase activity. Our results indicate that HDV requires highly regulated and selective editing and that the level of ADAR expression can play an important role: overexpression of ADARs inhibits HDV RNA replication and compromises virus viability.

Adenosine Deaminase↗

PubMed2005

Varicella-zoster virus open reading frame 47 (ORF47) protein is critical for virus replication in dendritic cells and for spread to other cells.

Varicella-zoster virus infects human dendritic cells (DCs). We found that VZV infection of DCs resulted in down-regulation of Fas expression on the surface of cells. VZV ORF47 was critical for replication of virus in human immature, but not mature DCs. Immature DCs infected with a mutant virus unable to express ORF47 expressed similar levels of a VZV immediate-early protein as cells infected with parental virus; however, cells infected with the ORF47 mutant expressed lower levels of glycoprotein E. Thus, in the absence of ORF47 protein, there is a block in viral replication between immediate-early and late gene expression. VZV unable to express ORF47 was severely impaired for spread of virus from DCs to melanoma cells. Infection of DCs with parental VZV resulted in a different pattern of phosphoproteins compared with the ORF47 mutant virus. Thus, VZV ORF47 is important for replication in immature DCs and for spread to other cells.

Antigens, CD↗

PubMed2005

Coordinate induction of IFN-alpha and -gamma by SARS-CoV also in the absence of virus replication.

BACKGROUND: Severe acute respiratory syndrome (SARS) is an emerging infection caused by a novel coronavirus known as SARS-CoV, characterized by an over-exuberant immune response with lung lymphomononuclear cells infiltration and proliferation that may account for tissue damage more than the direct effect of viral replication. This study is aimed at investigating the capability of SARS-CoV to activate IFN-alpha and -gamma expression in lymphomonocytes (PBMC) from healthy donors, evaluating whether viral replication is necessary for this activation. RESULTS: SARS-CoV virus is able to induce both IFN-alpha and -gamma mRNA accumulation and protein release in a dose-dependent manner, MOI 10 being the most effective. The time course curve indicated that IFN-alpha mRNA induction peaked at 24 h.p.i,. whereas IFN-gamma mRNA was still increasing at 48 h.p.i. Released IFN (both types) reached a plateau after 24-48 h.p.i. and remained rather stable over a 5-day period. A transient peak of negative strand viral RNA was detected after 1-2 days of infection, but neither infectious virus progeny yield nor newly produced viral genomic RNA could be evidenced in infected cultures, even after prolonged observation time (up to 13 days). Cocultivation of PBMC with fixed SARS-CoV-infected Vero cells was even more efficient than exposure to live virus in eliciting IFN-alpha and -gamma induction. A combination of IFN-alpha and -gamma strongly inhibited SARS-CoV replication in Vero cells, while the single cytokines were much less effective. CONCLUSIONS: This study provides evidence that SARS-CoV is able to induce in normal PBMC a coordinate induction of IFN-alpha and -gamma gene expression. Virus replication is not necessary for IFN induction since efficient IFN expression could be obtained also by the cocultivation of normal PBMC with fixed SARS-CoV-infected cells. Concomitant activation of IFN-alpha and -gamma gene expression by SARS-CoV in vivo may be relevant for the pathogenesis of the disease, both for the possible involvement in immunomediated damage of the tissues and for the strong inhibition of SARS-CoV replication as a result of combined cytokine action.

Animals↗

PubMed2005

CD8+ T cell depletion amplifies hepatitis C virus replication in peripheral blood mononuclear cells.

We investigated the ability of CD8+ T cells to inhibit hepatitis C virus (HCV) replication in peripheral blood mononuclear cells (PBMCs). PBMCs isolated from 11 of 20 HCV-infected subjects had no detectable HCV RNA. Removal of CD8+ T cells from these PBMCs resulted in detection of HCV RNA, and depletion of CD8+ T cells from PBMCs that had detectable HCV RNA amplified HCV replication. Reconstitution of CD8- PBMCs with autologous CD8+ T cells led to inhibition of HCV replication. Interferon-gamma produced by CD8+ T cells was partially responsible for CD8+ T cell-mediated noncytotoxic anti-HCV activity in PBMCs. This noncytotoxic anti-HCV activity was confirmed in HCV replicon cells. Supernatants from CD8+ T cell cultures inhibited HCV RNA expression in the replicon cells. These findings may have important implications for the immunopathogenesis of HCV in both immune and hepatic cells and are relevant to the development of host innate immunity-based anti-HCV interventions.

Antiviral Agents↗

PubMed1996

Human foamy virus replication: a pathway distinct from that of retroviruses and hepadnaviruses.

Human foamy virus (HFV) is the prototype of the Spumavirus genus of Retroviridae. In all other retroviruses, the pol gene products, including reverse transcriptase, are synthesized as Gag-Pol fusion proteins and are cleaved to functional enzymes during viral budding or release. In contrast, the Pol protein of HFV is translated from a spliced messenger RNA and lacks Gag domains. Infectious HFV particles contain double-stranded DNA similar in size to full-length provirus, suggesting that reverse transcription has taken place in viral particles before new rounds of infection, reminiscent of hepadnaviruses. These data suggest that foamy viruses possess a replication pathway containing features of both retroviruses and hepadnaviruses but distinct from both.

Amino Acid Sequence↗

PubMed1994

Effects of anisotonic exposure on duck hepatitis B virus replication.

In cultured hepatocytes from in vivo duck hepatitis B virus-infected ducks the effect of medium osmolarity on viral replication was studied. A 10-day exposure to hypotonic media (277 mOsm/L due to removal of 26 mmol/L NaCl) lowered the duck hepatitis B virus DNA content of cells and of the medium by about 50%, whereas hyperosmotic exposure (421 mOsm/L by addition of 46 mmol/L NaCl) increased it about four-fold compared with normotonic standard incubation medium (329 mOsm/L). The tissue levels of viral RNA transcripts increased during the 10 days of hypertonic exposure but decreased only slightly after hypoosmotic treatment. Western-blot analysis for the production of viral pre-S/S proteins revealed a marked stimulation of viral protein synthesis in hypertonic media, whereas hypotonic exposure inhibited it. Conversely, total cellular protein synthesis as assessed from [3H]leucine incorporation into acid-precipitable material decreased during hyperosmotic exposure but increased during hypoosmotic exposure. We noted a comparable increase of duck hepatitis B virus DNA when raffinose (80 mmol/L) was added to hypotonic or normotonic media, without change in the NaCl concentrations. This suggests that the effects of anisotonicity on viral replication were not due to alterations of Na+ or Cl- activity in the incubation media, but might reflect changes of cellular volume. The effects of anisotonicity on viral replication were only seen after exposure of more than 8 hr of the cells to anisotonicity. The findings suggest that the cellular volume is an important determinant for duck hepatitis B virus replication, yet the underlying molecular mechanisms remain elusive.

Animals↗

PubMed1979

A human breast tumor cell line (BT-474) that supports mouse mammary tumor virus replication.

A human breast tumor cell line BT-474 derived from an invasive ductal carcinoma was experimentally infected in vitro with a mouse mammary tumor virus from the TIII strain (RIII-MuMTV). The virus that replicated in the human cells was characterized as a mouse virus by immunofluorescence, electron microscopy and the presence of a specific RNA-directed DNA polymerase. The cells themselves were human as per the karyotype and isoenzyme migration patterns. It is concluded that human cells are susceptible to the mouse mammary tumor virus and can, eventually, support its replication.

Antigens, Viral↗

PubMed1990

Inhibitory effects of atropine, protamine, and their combination on hepatitis A virus replication in PLC/PRF/5 cells.

Atropine, protamine, and the combination of these drugs were tested for their effects on hepatitis A virus (HAV) replication in cell culture. PLC/PRF/5 hepatoma cells were treated simultaneously with nontoxic concentrations of these drugs and inoculated with HAV strain CF 53 at several multiplicities of infection. The yields of infectious HAV after 4 and 15 days were markedly reduced by each drug, especially at the lowest multiplicity of infection. The activities of each drug were irreversible. Atropine was active when it was added as late as 2 h after inoculation with HAV. An anti-HAV effect was also induced by treating cells with atropine prior to inoculation. Protamine was active as late as 6 h postinoculation. The combination of atropine and protamine resulted in an enhanced anti-HAV effect. We concluded that these drugs affect undetermined, but separate, steps in the HAV replication cycle.

Atropine↗

PubMed2004

Regulation of hepatitis C virus replication by interferon regulatory factor 1.

Cellular antiviral responses are mediated partly by the expression of interferon-stimulated genes, triggered by viral genomes, their transcripts and replicative intermediates. Persistent replication of a hepatitis C virus (HCV) replicon suggests that the replicon does not elicit cellular innate antiviral responses. In the present study, we investigated regulatory factors of the interferon-mediated antiviral system in cells expressing an HCV replicon. Luciferase reporter assays revealed that the baseline activity of the interferon-stimulated response element (ISRE) was significantly lower in cells harboring the replicon than in naive cells. Among the proteins involved in the IFN/Jak/STAT pathway and in ISRE activity, the expression level of interferon regulatory factor 1 (IRF-1) was found to be significantly lower in cells harboring the replicon. Transfection of an IRF-1 expression construct into cells harboring the replicon caused an increase of ISRE activity, accompanied by suppression of expression of the HCV replicon. Moreover, in cured Huh7 cells from which the HCV replicon had been eliminated, the expression levels of IRF-1 and ISRE activity also were suppressed, demonstrating that the decrease of IRF-1 is attributable, not to active suppression by the viral proteins, but to adaptation of cells that enables replication of the HCV subgenome. The high permissiveness of the cured cells for the replicon was abolished by transgenic supplementation of IRF-1 expression. Taken together, IRF-1 is one of the key host factors that regulate intracellular HCV replication through modulation of interferon-stimulated-gene-mediated antiviral responses.

Base Sequence↗

PubMed1991

Effects of purine nucleoside analogues with a cyclobutane ring and erythromycin A oxime derivatives on duck hepatitis B virus replication in vivo and in cell culture and HIV-1 in cell culture.

The effects on duck hepatitis B virus (DHBV) replication of specific analogues of two classes of chemical compounds not previously tested against hepadnaviruses are described. One is erythromycin A-9-methyloxime (EMO) and other oxime derivatives of erythromycin A, and the other is purine nucleoside analogues (cyclobut A and cyclobut G) with cyclobutane rings. Viral replication was assessed by measuring serum levels of DHBV DNA in infected ducklings and DHBV DNA in infected primary duck hepatocyte cultures. Administration of EMO 15 mg/kg of body weight IM to infected ducklings resulted in a rapid fall in DHBV DNA levels during therapy and a return to pretreatment levels after EMO administration was stopped. There was local toxicity at injection sites with muscle necrosis in some animals. When 100 mg/kg EMO was administered by gastric tube no such viral response was observed. The difference in virus response to EMO 15mg/kg IM and 100 mg/kg by gastric tube was not due to failure to achieve comparable blood and tissue levels of EMO administered by the different routes. The results suggest an indirect effect dependent on IM injection of EMO rather than a direct antiviral effect of the compound. Administration of cyclobut G or cyclobut A at 70 mg/kg IM led to a rapid reduction of DHBV DNA to undetectable levels in serum, and in only 1 of 4 animals did DHBV DNA became detectable again within 10 days after stopping the drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine↗

PubMed1988

Suppression of simian immunodeficiency virus replication in vitro by CD8+ lymphocytes.

The AIDS-like disease in rhesus monkeys induced by the simian immunodeficiency virus (SIV) has been used as a model to explore the nature of the T lymphocyte response after infection with viruses of the human immunodeficiency virus family. Activated CD8+ lymphocytes are present in increased numbers in the paracortex of lymph nodes of SIV-infected rhesus monkeys with a lymphadenopathy syndrome. We demonstrate that SIV is more readily isolated from CD8+ lymphocyte-depleted PBL of SIV-infected animals than from their unfractionated PBL. Rather than reflecting the fact that the CD8+ lymphocyte-depleted cell populations are simply enriched for CD4+ lymphocytes, this indicates that CD8+ cells themselves are critical in this regulatory interaction. In fact, CD8+ lymphocytes from SIV-infected but not uninfected rhesus monkeys can block SIV replication in vitro in PBL populations. A T lymphocyte population that blocks replication of viruses of the HIV family may contribute to containing the progression of AIDS.

AIDS-Related Complex↗