scispace - formally typeset
Search or ask a question

Showing papers on "Virus published in 2003"


Journal ArticleDOI
TL;DR: The novel coronavirus might have a role in causing SARS and was detected in a variety of clinical specimens from patients with SARS but not in controls.
Abstract: BACKGROUND: The severe acute respiratory syndrome (SARS) has recently been identified as a new clinical entity. SARS is thought to be caused by an unknown infectious agent. METHODS: Clinical specimens from patients with SARS were searched for unknown viruses with the use of cell cultures and molecular techniques. RESULTS: A novel coronavirus was identified in patients with SARS. The virus was isolated in cell culture, and a sequence 300 nucleotides in length was obtained by a polymerase-chain-reaction (PCR)-based random-amplification procedure. Genetic characterization indicated that the virus is only distantly related to known coronaviruses (identical in 50 to 60 percent of the nucleotide sequence). On the basis of the obtained sequence, conventional and real-time PCR assays for specific and sensitive detection of the novel virus were established. Virus was detected in a variety of clinical specimens from patients with SARS but not in controls. High concentrations of viral RNA of up to 100 million molecules per milliliter were found in sputum. Viral RNA was also detected at extremely low concentrations in plasma during the acute phase and in feces during the late convalescent phase. Infected patients showed seroconversion on the Vero cells in which the virus was isolated. CONCLUSIONS: The novel coronavirus might have a role in causing SARS.

4,180 citations


Journal ArticleDOI
TL;DR: A novel coronavirus is associated with this outbreak of severe acute respiratory syndrome, and the evidence indicates that this virus has an etiologic role in SARS.
Abstract: background A worldwide outbreak of severe acute respiratory syndrome (SARS) has been associated with exposures originating from a single ill health care worker from Guangdong Province, China. We conducted studies to identify the etiologic agent of this outbreak. methods We received clinical specimens from patients in six countries and tested them, using virus isolation techniques, electron-microscopical and histologic studies, and molecular and serologic assays, in an attempt to identify a wide range of potential pathogens. results No classic respiratory or bacterial respiratory pathogen was consistently identified. However, a novel coronavirus was isolated from patients who met the case definition of SARS. Cytopathological features were noted microscopically in Vero E6 cells inoculated with a throat-swab specimen. Electron-microscopical examination of cultures revealed ultrastructural features characteristic of coronaviruses. Immunohistochemical and immunofluorescence staining revealed reactivity with group I coronavirus polyclonal antibodies. Consensus coronavirus primers designed to amplify a fragment of the polymerase gene by reverse transcription–polymerase chain reaction (RT-PCR) were used to obtain a sequence that clearly identified the isolate as a unique coronavirus only distantly related to previously sequenced coronaviruses. With specific diagnostic RT-PCR primers we identified several identical nucleotide sequences in 12 patients from several locations, a finding consistent with a point source outbreak. Indirect fluorescent antibody tests and enzyme-linked immunosorbent assays made with the new coronavirus isolate have been used to demonstrate a virus-specific serologic response. Preliminary studies suggest that this virus may never before have infected the U.S. population. conclusions A novel coronavirus is associated with this outbreak, and the evidence indicates that this virus has an etiologic role in SARS. The name Urbani SARS-associated coronavirus is proposed for the virus.

4,065 citations


Journal ArticleDOI
TL;DR: Plasma virus continually and rapidly evolved to escape neutralization, indicating that neutralizing antibody exerts a level of selective pressure that has been underappreciated based on earlier, less comprehensive characterizations.
Abstract: A recombinant virus assay was used to characterize in detail neutralizing antibody responses directed at circulating autologous HIV in plasma. Examining serial plasma specimens in a matrix format, most patients with primary HIV infection rapidly generated significant neutralizing antibody responses to early (0–39 months) autologous viruses, whereas responses to laboratory and heterologous primary strains were often lower and delayed. Plasma virus continually and rapidly evolved to escape neutralization, indicating that neutralizing antibody exerts a level of selective pressure that has been underappreciated based on earlier, less comprehensive characterizations. These data argue that neutralizing antibody responses account for the extensive variation in the envelope gene that is observed in the early months after primary HIV infection.

1,257 citations


Journal ArticleDOI
TL;DR: It is shown that the HIV-1 virion infectivity factor (Vif) protein protects the virus from APOBEC3G-mediated inactivation by preventing its incorporation into progeny virions, thus allowing the ensuing infection to proceed without DNA deamination.
Abstract: The human protein apolipoprotein B mRNA-editing enzyme–catalytic polypeptide-like-3G (APOBEC3G), also known as CEM-15, mediates a newly described form of innate resistance to retroviral infection by catalyzing the deamination of deoxycytidine to deoxyuridine in viral cDNA replication intermediates. Because DNA deamination takes place after virus entry into target cells, APOBEC3G function is dependent on its association with the viral nucleoprotein complexes that synthesize cDNA and must therefore be incorporated into virions as they assemble in infected cells. Here we show that the HIV-1 virion infectivity factor (Vif) protein protects the virus from APOBEC3G-mediated inactivation by preventing its incorporation into progeny virions, thus allowing the ensuing infection to proceed without DNA deamination. In addition to helping exclude APOBEC3G from nascent virions, Vif also removes APOBEC3G from virus-producing cells by inducing its ubiquitination and subsequent degradation by the proteasome. Our findings indicate that pharmacologic strategies aimed at stabilizing APOBEC3G in HIV-1 infected cells should be explored as potential HIV/AIDS therapeutics.

990 citations


Journal ArticleDOI
13 Nov 2003-Nature
TL;DR: Administration of BILN 2061 to patients infected with HCV genotype 1 for 2 days resulted in an impressive reduction of HCV RNA plasma levels, and established proof-of-concept in humans for an HCV NS3 protease inhibitor, illustrating the potential of the viral-enzyme-targeted drug discovery approach for the development of new HCV therapeutics.
Abstract: Hepatitis C virus (HCV) infection is a serious cause of chronic liver disease worldwide with more than 170 million infected individuals at risk of developing significant morbidity and mortality. Current interferon-based therapies are suboptimal especially in patients infected with HCV genotype 1, and they are poorly tolerated, highlighting the unmet medical need for new therapeutics. The HCV-encoded NS3 protease is essential for viral replication and has long been considered an attractive target for therapeutic intervention in HCV-infected patients. Here we identify a class of specific and potent NS3 protease inhibitors and report the evaluation of BILN 2061, a small molecule inhibitor biologically available through oral ingestion and the first of its class in human trials. Administration of BILN 2061 to patients infected with HCV genotype 1 for 2 days resulted in an impressive reduction of HCV RNA plasma levels, and established proof-of-concept in humans for an HCV NS3 protease inhibitor. Our results further illustrate the potential of the viral-enzyme-targeted drug discovery approach for the development of new HCV therapeutics.

895 citations


Journal ArticleDOI
TL;DR: It is demonstrated that CD8+ cells are the main effector cells responsible for viral clearance and disease pathogenesis during acute HBV infection, and it is suggested that viral clearance is mediated by both noncytolytic and cy tolytic effector functions of the CD8-T-cell response.
Abstract: Although the CD4 + - and CD8 + -T-cell responses to the hepatitis B virus (HBV) are thought to be crucial for the control of HBV infection, the relative contribution of each T-cell subset as an effector of viral clearance is not known. To examine this question, we monitored the course of HBV infection in control, CD4-depleted, and CD8-depleted chimpanzees. Our results demonstrate that CD8 + cells are the main effector cells responsible for viral clearance and disease pathogenesis during acute HBV infection, and they suggest that viral clearance is mediated by both noncytolytic and cytolytic effector functions of the CD8 + -T-cell response.

875 citations


Journal ArticleDOI
16 May 2003-Science
TL;DR: The NS3/4A protease represents a dual therapeutic target, the inhibition of which may both block viral replication and restore IRF-3 control of HCV infection.
Abstract: Persistent infections with hepatitis C virus (HCV) are likely to depend on viral inhibition of host defenses. We show that the HCV NS3/4A serine protease blocks the phosphorylation and effector action of interferon regulatory factor-3 (IRF-3), a key cellular antiviral signaling molecule. Disruption of NS3/4A protease function by mutation or a ketoamide peptidomimetic inhibitor relieved this blockade and restored IRF-3 phosphorylation after cellular challenge with an unrelated virus. Furthermore, dominant-negative or constitutively active IRF-3 mutants, respectively, enhanced or suppressed HCV RNA replication in hepatoma cells. Thus, the NS3/4A protease represents a dual therapeutic target, the inhibition of which may both block viral replication and restore IRF-3 control of HCV infection.

841 citations


Journal ArticleDOI
TL;DR: Increased T cell activation was associated with shorter duration of viral suppression, hepatitis C virus coinfection, frequent low-level viremia, and lower nadir CD4(+) T cell counts.
Abstract: Although T cell activation is associated with disease progression in untreated human immunodeficiency virus type 1 (HIV-1) infection, its significance in antiretroviral-treated patients is unknown. Activated (CD38(+)HLA-DR(+)) T cell counts were measured in 99 HIV-infected adults who had maintained a plasma HIV RNA level

817 citations


Journal ArticleDOI
TL;DR: Hepatitis E virus is an enterically transmitted virus that causes both epidemics and sporadic cases of acute hepatitis in many countries of Asia and Africa but only rarely causes disease in more industrialised countries.
Abstract: Hepatitis E virus (HEV) is a positive-stranded RNA virus with a 7.2 kb genome that is capped and polyadenylated. The virus is currently unclassified: the organisation of the genome resembles that of the Caliciviridae but sequence analyses suggest it is more closely related to the Togaviridae. Hepatitis E virus is an enterically transmitted virus that causes both epidemics and sporadic cases of acute hepatitis in many countries of Asia and Africa but only rarely causes disease in more industrialised countries. Initially the virus was believed to have a limited geographical distribution. However, serological studies suggest that HEV may be endemic also in the United States and Europe even though it infrequently causes overt disease in these countries. Many different animal species worldwide recently have been shown to have antibodies to HEV suggesting that hepatitis E may be zoonotic. Although two related strains have been experimentally transmitted between species, direct transmission from an animal to a human has not been documented. There are four currently recognised genotypes and two of the four contain viruses isolated from swine as well as from humans. Regardless of country of origin or genotype of the virus, most, if not all, strains belong to a single serotype. A promising recombinant vaccine candidate comprised of a truncated capsid protein is currently under evaluation in Nepal.

799 citations


Journal ArticleDOI
TL;DR: Profound T-cell activation and death may contribute to the systemic disturbances leading to DHF, and original antigenic sin in the T- cell responses may suppress or delay viral elimination, leading to higher viral loads and increased immunopathology.
Abstract: Dengue virus presents a growing threat to public health in the developing world. Four major serotypes of dengue virus have been characterized, and epidemiological evidence shows that dengue hemorrhagic fever (DHF), the more serious manifestation of the disease, occurs more frequently upon reinfection with a second serotype. We have studied dengue virus–specific T-cell responses in Thai children. During acute infection, few dengue-responsive CD8+ T cells were recovered; most of those present showed an activated phenotype and were undergoing programmed cell death. Many dengue-specific T cells were of low affinity for the infecting virus and showed higher affinity for other, probably previously encountered strains. Profound T-cell activation and death may contribute to the systemic disturbances leading to DHF, and original antigenic sin in the T-cell responses may suppress or delay viral elimination, leading to higher viral loads and increased immunopathology.

779 citations


Journal ArticleDOI
07 Mar 2003-Science
TL;DR: Analysis of Murine Norovirus 1 infection revealed that signal transducer and activator of transcription 1–dependent innate immunity, but not T and B cell–dependent adaptive immunity, is essential for norovirus resistance.
Abstract: Norwalk-like caliciviruses (Noroviruses) cause over 90% of nonbacterial epidemic gastroenteritis worldwide, but the pathogenesis of norovirus infection is poorly understood because these viruses do not grow in cultured cells and there is no small animal model. Here, we report a previously unknown murine norovirus. Analysis of Murine Norovirus 1 infection revealed that signal transducer and activator of transcription 1-dependent innate immunity, but not T and B cell-dependent adaptive immunity, is essential for norovirus resistance. The identification of host molecules essential for murine norovirus resistance may provide targets for prevention or control of an important human disease.

Journal ArticleDOI
TL;DR: The discovery that group B adenoviruses use CD46, a ubiquitously expressed complement regulatory protein, as a cellular attachment receptor elucidates the diverse clinical manifestation of group B virus infections, and bears directly on the application of these vectors for gene therapy.
Abstract: Group B adenoviruses, a subgenus of human Adenoviridae, are associated with a variety of often-fatal illnesses in immunocompromised individuals, including bone marrow transplant recipients and cancer and AIDS patients. Recently, group B adenovirus derivatives have gained interest as attractive gene therapy vectors because they can transduce target tissues, such as hematopoietic stem cells, dendritic cells and malignant tumor cells, that are refractory to infection by commonly used adenoviral vectors. Whereas many adenoviruses infect cells through the coxsackievirus and adenovirus receptor (CAR), group B adenoviruses use an alternate, as-yet-unidentified cellular attachment receptor. Using mass spectrometric analysis of proteins interacting with a group B fiber, we identified human CD46 as a cellular attachment receptor for most group B adenoviruses. We show that ectopic expression of human CD46 rendered nonhuman cells susceptible to infection with group B viruses in vitro and in vivo. In addition, both siRNA-mediated knockdown of CD46 and a soluble form of CD46 blocked infection of human cell lines and primary human cells. The discovery that group B adenoviruses use CD46, a ubiquitously expressed complement regulatory protein, as a cellular attachment receptor elucidates the diverse clinical manifestation of group B virus infections, and bears directly on the application of these vectors for gene therapy.

Book ChapterDOI
TL;DR: An overview of the molecular biology of the flaviviruses is presented, which are enveloped positive-strand RNA viruses capable of causing a number of important human diseases.
Abstract: Publisher Summary This chapter summarizes the current understanding of the molecular biology of flaviviruses and points out promising avenues for future work. The molecular biology of flaviviruses is best understood in the context of the viral life cycle, which provides a framework for the organization of this chapter. Flavivirus particles bind to cells via interactions between the viral surface glycoprotein and cellular receptors. Several cell surface proteins have been described as putative receptors. In addition, opsonization with immunoglobulins enhances virus particle binding and infection of cells expressing immunoglobulin Fc receptors. Virions are internalized into clathrin-coated pits via receptor-mediated endocytosis. It is thought that virions are brought into a prelysosomal endocytic compartment where low pH induces fusion among the viruses and host cell membranes to release the virus nucleocapsid. The viral genome is released into the host cytoplasm by the process of nucleocapsid uncoating, which is not yet fully understood. Translation of the viral genome produces proteins that lead to replication of the viral genome and assembly of new virus particles. Flavivirus infection induces rearrangement of cytoplasmic membranes in the perinuclear region. Virus particles are thought to assemble by budding into the endoplasmic reticulum. A few studies have shown evidence for budding at the plasma membrane. Based on trans-complementation studies, it appears that genome packaging is coupled to RNA replication. Nascent virus particles pass through the host secretory pathway, where virion maturation occurs, and are released.

Journal ArticleDOI
TL;DR: The studies demonstrate the feasibility and potential of lentiviral vector-mediated delivery of siRNAs as a general means of intracellular immunization for the treatment of HIV-1 and other viral diseases.
Abstract: Double-stranded RNAs ≈21 nucleotides long [small interfering RNA (siRNA)] are recognized as powerful reagents to reduce the expression of specific genes. To use them as reagents to protect cells against viral infection, effective methods for introducing siRNAs into primary cells are required. Here, we describe success in constructing a lentivirus-based vector to introduce siRNAs against the HIV-1 coreceptor, CCR5, into human peripheral blood T lymphocytes. With high-titer vector stocks, >40% of the peripheral blood T lymphocytes could be transduced, and the expression of a potent CCR5-siRNA resulted in up to 10-fold inhibition of CCR5 expression on the cell surface over a period of 2 weeks in the absence of selection. In contrast, the expression of another major HIV-1 coreceptor, CXCR4, was not affected. Importantly, blocking CCR5 expression by siRNAs provided a substantial protection for the lymphocyte populations from CCR5-tropic HIV-1 virus infection, dropping infected cells by 3- to 7-fold; only a minimal effect on infection by a CXCR4-tropic virus was observed. Thus, our studies demonstrate the feasibility and potential of lentiviral vector-mediated delivery of siRNAs as a general means of intracellular immunization for the treatment of HIV-1 and other viral diseases.

Journal ArticleDOI
TL;DR: The data presented indicate that JS1/ICP34.5−/ ICP47-/GM-CSF acts as a powerful oncolytic agent which may be appropriate for the treatment of a number of solid tumour types in man.
Abstract: Herpes simplex virus type-1 (HSV1) in which the neurovirulence factor ICP34.5 is inactivated has been shown to direct tumour-specific cell lysis in several tumour models. Such viruses have also been shown to be safe in Phase I clinical trials by intra-tumoral injection in glioma and melanoma patients. Previous work has used serially passaged laboratory isolates of HSV1 which we hypothesized may be attenuated in their lytic capability in human tumour cells as compared to more recent clinical isolates. To produce ICP34.5 deleted HSV with enhanced oncolytic potential, we tested two clinical isolates. Both showed improved cell killing in all human tumour cell lines tested compared to a laboratory strain (strain 17+). ICP34.5 was then deleted from one of the clinical isolate strains (strain JS1). Enhanced tumour cell killing with ICP34.5 deleted HSV has also been reported by the deletion of ICP47 by the up-regulation of US11 which occurs following this mutation. Thus to further improve oncolytic properties, ICP47 was removed from JS1/ICP34.5-. As ICP47 also functions to block antigen processing in HSV infected cells, this mutation was also anticipated to improve the immune stimulating properties of the virus. Finally, to provide viruses with maximum oncolytic and immune stimulating properties, the gene for human or mouse GM-CSF was inserted into the JS1/34.5-/47- vector backbone. GM-CSF is a potent immune stimulator promoting the differentiation of progenitor cells into dendritic cells and has shown promise in clinical trials when delivered by a number of means. Combination of GM-CSF with oncolytic therapy may be particularly effective as the necrotic cell death accompanying virus replication should serve to effectively release tumour antigens to then induce a GM-CSF-enhanced immune response. This would, in effect, provide an in situ, patient-specific, anti-tumour vaccine. The viruses constructed were tested in vitro in human tumour cell lines and in vivo in mice demonstrating significant anti-tumour effects. These were greatly improved compared to viruses not containing each of the modifications described. In vivo, both injected and non-injected tumours showed significant shrinkage or clearance and mice were protected against re-challenge with tumour cells. The data presented indicate that JS1/ICP34.5-/ICP47-/GM-CSF acts as a powerful oncolytic agent which may be appropriate for the treatment of a number of solid tumour types in man.

Journal ArticleDOI
TL;DR: It is shown that the pattern recognition receptors Toll-like receptor 2 (TLR2) and CD14 recognize CMV virions and trigger inflammatory cytokine production, suggesting that a membrane receptor recognizes a CMV envelope protein(s), leading to innate immune activation.
Abstract: Human cytomegalovirus (CMV) is a ubiquitous opportunistic pathogen. Clinically, CMV disease correlates with immune suppression in which severe presentations are evident in neonates, persons with AIDS, and other immune-suppressed patient groups (38). CMV infection of neonates is associated with deafness, mental retardation, and mortality, whereas AIDS patients often suffer a blinding CMV retinitis, as well as pneumonia and gastrointestinal inflammation. In organ transplant recipients, a patient group hard hit by CMV infection, disease is associated with an increased frequency of graft rejection and is a major cause of posttransplant infection. The varied array of clinical disease correlates with the exceptionally broad tropism of this virus. Indeed, histological analysis of autopsy tissues obtained from patients with CMV disease has demonstrated infected cells in virtually all organs. At the cellular level, CMV can infect monocytes/macrophages, endothelial cells, epithelial cells, smooth muscle cells, fibroblasts, stromal cells, neuronal cells, neutrophils, and hepatocyes (13, 17, 35, 44, 48, 49, 61). In fact, CMV is a suspected pathogenetic agent in cardiovascular disease due to its ability to persist in large-vessel endothelial cells and to infect all cell types involved in cardiovascular lesions (24). Cells exposed to CMV undergo a number of physiological changes that are rendered upon the cell with extremely rapid kinetics (15). These events include changes in Ca2+ homeostasis (1) and activation of phospholipase C and phospholipase A2, as well as increased release of arachidonic acid and its metabolites (1, 59). All of these changes can be triggered by UV-inactivated virions, suggesting that structural components of the virus are responsible for the alterations in cell physiology and intracellular signaling that occur during virus-cell contact and/or virus entry. Virus-cell contact also results in the activation of the transcription factors NF-κB and SP-1, as well as mitogen-activated protein (MAP) kinase, ERK1/2, and p38 (7, 26, 63). Activation of transcription factors by CMV suggests that alterations in cellular transcription should occur in CMV-infected cells, and this is precisely the case. Several transcriptional-profiling studies reveal that cells infected with CMV exhibit profound reprogramming of gene expression (8, 47, 64, 65). Interestingly, the most strongly induced genes were indicators of innate immune activation. Antiviral genes belonging to the interferon-stimulated gene family (ISGs) and inflammatory genes, such as those for RANTES, interleukin 6 (IL-6), IL-7, IL-11, and cyclooxygenase 2 (COX-2), were all robustly induced in CMV-infected fibroblasts (8, 47, 64, 65). Induction of these innate immune markers did not require virus replication. Indeed, cells treated with only the primary ligand of CMV, glycoprotein B (gB) (6), exhibited a response very similar, but not wholly identical, to that of cells treated with intact virus (47). In particular, cells treated with gB strongly induced ISGs. Taken together, the findings suggest that a signal transduction pathway is activated by cell contact of CMV envelope proteins, resulting in numerous physiological changes that culminate, in part, with innate immune activation. The innate immune system is an ancient, universal host defense system. A limited number of evolutionarily conserved germ line receptors found in plants, Drosophila, and humans mediate certain innate immune responses. Termed pattern recognition receptors, these molecules form the basis of the primary host alarm system in response to pathogen-associated molecular patterns (PAMPs) (23). Toll-like receptors (TLRs) are now understood to play a major role in pathogen recognition. Stimulation of TLRs by pathogens activates signal transduction pathways that lead to induction of a range of antimicrobial genes and inflammatory cytokines (2, 23, 29). In addition, key costimulatory molecules, such as CD80 and CD86, which are important for activation of adaptive immunity, are also induced as a consequence of TLR signaling. At present, 10 TLR molecules have been described in humans and mice. Ligands ranging from lipopolysaccharide (LPS) of gram-negative bacteria, peptidoglycan of gram-positive bacteria, flagellin, CpG DNA, and various components from mycobacteria, yeast, and parasitic pathogens, are all detected by TLRs. Although the precise molecular patterns are not completely characterized, PAMPs are hypothesized to be macromolecular modifications unique to these organisms. Viruses have long been known to activate innate immune responses characterized by the induction of inflammatory cytokines and a comprehensive set of ISGs (45, 53). Until recently, the only identified molecular trigger of host innate responses was double-stranded RNA, a common replicative intermediate in the life cycle of many viruses. Double-stranded RNA can activate a key interferon transcription factor, interferon regulatory factor 3 (IRF-3), and induce synthesis of many antiviral genes. Generally, however, the mechanisms by which viruses activate innate immunity remain largely undefined. Since viruses are obligate intracellular parasites, virus-encoded proteins are synthesized by host machinery and ultimately bear protein modifications reflective of the host. Thus, it is not immediately obvious what PAMPs are displayed on viruses. Currently, however, data are clearly emerging showing that TLRs detect viruses and trigger inflammatory responses. Respiratory syncytcial virus (RSV) and mouse mammary tumor virus (MMTV) both signal through TLR4 (28, 42), the well-described LPS receptor. In the case of RSV, TLR4-deficient mice challenged with RSV exhibited a variety of impaired innate immune functions and an inability to clear the virus (20). These findings strongly suggest that Toll signaling pathways have an important role in the innate immunity to RSV. More recently, measles virus was reported to be detected by TLR2, a TLR with broad ligand recognition properties (5). The most striking common feature of these first three reports of virus detection by TLRs is that TLR responses were triggered by viral envelope glycoproteins. Specifically, the fusion protein of RSV, the envelope (env) protein of MMTV, and the hemagglutinin protein of measles virus were the identified triggers of the TLR responsiveness in their respective systems. Interestingly, all of these proteins play key roles in the virus entry pathway, such as attachment and fusion. These studies plainly point to a heretofore-unknown ability of the host to detect viruses during entry but prior to the onset of any replication events. Here, we report that TLR2 and CD14 form the central basis of the membrane detection machinery for CMV.

Journal ArticleDOI
TL;DR: The hypothesis that insulin resistance may contribute to fibrotic progression in chronic hepatitis C virus infection is supported, and the effect seems to be genotype specific.

Journal ArticleDOI
14 Mar 2003-Science
TL;DR: It is shown that cell contact rapidly induces polarization of the cytoskeleton of the infected cell to the cell-cell junction, and HTLV-I core (Gag protein) complexes and the HT LVI genome accumulate at thecell junction and are then transferred to the uninfected cell.
Abstract: Cell contact is required for efficient transmission of human T cell leukemia virus- type 1 (HTLV-I) between cells and between individuals, because naturally infected lymphocytes produce virtually no cell-free infectious HTLV-I particles. However, the mechanism of cell-to-cell spread of HTLV-I is not understood. We show here that cell contact rapidly induces polarization of the cytoskeleton of the infected cell to the cell-cell junction. HTLV-I core (Gag protein) complexes and the HTLV-I genome accumulate at the cell-cell junction and are then transferred to the uninfected cell. Other lymphotropic viruses, such as HIV-1, may similarly subvert normal T cell physiology to allow efficient propagation between cells.

Journal ArticleDOI
TL;DR: An essential role for memory CD8+ T cells in long-term protection from chronic hepatitis C is demonstrated by antibody-mediated depletion of this lymphocyte subset before a third infection.
Abstract: Few hepatitis C virus (HCV) infections resolve spontaneously but those that do appear to afford protective immunity. Second infections are usually shorter in duration and are less likely to persist but mechanisms of virus control in immune individuals have not been identified. In this study we investigated whether memory helper and/or cytotoxic T lymphocytes provide protection in chimpanzees serially reinfected with the virus. Clearance of the first infection took 3–4 mo and coincided with the delayed onset of CD4+ and CD8+ T cell responses. High frequencies of memory T cells targeting multiple HCV proteins were stable over 7 yr of follow-up. Animals were infected for a second time to assess the protective role of memory T cells. In contrast to the prolonged course of the first infection, viremia was terminated within 14 d. Control of this second infection was kinetically linked to rapid acquisition of virus-specific cytolytic activity by liver resident CD8+ T cells and expansion of memory CD4+ and CD8+ T cells in blood. The importance of memory CD8+ T cells in control of HCV infection was confirmed by antibody-mediated depletion of this lymphocyte subset before a third infection. Virus replication was prolonged despite the presence of memory CD4+ T helper cells primed by the two prior infections and was not terminated until HCV-specific CD8+ T cells recovered in the liver. These experiments demonstrate an essential role for memory CD8+ T cells in long-term protection from chronic hepatitis C.

Journal ArticleDOI
TL;DR: In this article, RNA interference was applied to inhibit production of HBV replicative intermediates in cell culture and in immunocompetent and immunodeficient mice transfected with an HBV plasmid.
Abstract: Hepatitis B virus (HBV) infection substantially increases the risk of chronic liver disease and hepatocellular carcinoma in humans. RNA interference (RNAi) of virus-specific genes has emerged as a potential antiviral mechanism. Here we show that RNAi can be applied to inhibit production of HBV replicative intermediates in cell culture and in immunocompetent and immunodeficient mice transfected with an HBV plasmid. Cotransfection with plasmids expressing short hairpin RNAs (shRNAs) homologous to HBV mRNAs induced an RNAi response. Northern and Southern analyses of mouse liver RNA and DNA showed substantially reduced levels of HBV RNAs and replicated HBV genomes upon RNAi treatment. Secreted HBV surface antigen (HBsAg) was reduced by 94.2% in cell culture and 84.5% in mouse serum, whereas immunohistochemical detection of HBV core antigen (HBcAg) revealed >99% reduction in stained hepatocytes upon RNAi treatment. Thus, RNAi effectively inhibited replication initiation in cultured cells and mammalian liver, showing that such an approach could be useful in the treatment of viral diseases.

Journal ArticleDOI
TL;DR: It is found that expression in human A549 cells of the dengue virus nonstructural proteins NS2A, NS4A, or NS4B enhances replication of an IFN-sensitive virus.
Abstract: Dengue virus is a worldwide-distributed mosquito-borne flavivirus with a positive strand RNA genome. Its transcribed polyprotein is cleaved by host- and virus-encoded peptidases into 10 proteins, some of which are of unknown function. Although dengue virus-infected cells seem to be resistant to the antiviral action of IFN, the viral products that mediate this resistance are unknown. Therefore, we have analyzed the ability of the 10 dengue virus-encoded proteins to antagonize the IFN response. We found that expression in human A549 cells of the dengue virus nonstructural proteins NS2A, NS4A, or NS4B enhances replication of an IFN-sensitive virus. Moreover, expression of NS4B and, to a lesser extent, of NS2A and NS4A proteins results in down-regulation of IFN-β-stimulated gene expression. Cells expressing NS4B or infected with dengue virus do not exhibit nuclear signal transducer and activator of transcription (STAT) 1 on treatment with IFN-β or IFN-γ, indicating that NS4B might be involved in blocking IFN signaling during dengue virus infections. This protein, encoded by a positive strand RNA virus, is implicated as an IFN-signaling inhibitor.

Journal ArticleDOI
TL;DR: Polymerase chain reaction identified adenovirus as the most common virus in the myocardium of children and adults with myocarditis and DCM, and enteroviruses are also found in these patients.

Journal ArticleDOI
TL;DR: In this article, the authors defined the natural course of acute hepatitis C virus infection and contributed to the development of treatment strategies for acute hepatitisC virus infection by using seroconversion to anti-hepatitis C virus antibodies or clinical and biochemical criteria.

Journal ArticleDOI
TL;DR: Intriguingly, the three main types of EBV-associated B-cell lymphoma — that is, Burkitt lymphoma, Hodgkin lymphoma and post-transplant lymphomas — seem to derive from germinal-centre B cells or atypical survivors of the germinalscentre reaction in most, if not all, cases, indicating that EBV -infected germinAL-cent centre B cells are at particular risk for malignant transformation.
Abstract: Epstein-Barr virus (EBV) is an extremely successful virus, infecting more than 90% of the human population worldwide. After primary infection, the virus persists for the life of the host, usually as a harmless passenger residing in B cells. However, EBV can transform B cells, which can result in the development of malignant lymphomas. Intriguingly, the three main types of EBV-associated B-cell lymphoma - that is, Burkitt lymphoma, Hodgkin lymphoma and post-transplant lymphomas - seem to derive from germinal-centre B cells or atypical survivors of the germinal-centre reaction in most, if not all, cases, indicating that EBV-infected germinal-centre B cells are at particular risk for malignant transformation.

Journal ArticleDOI
11 Aug 2003-Oncogene
TL;DR: This review summarises the current knowledge of EBV latent gene function and how this relates to the role of the virus in the aetiology of different tumours.
Abstract: Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus associated with the development of both lymphoid and epithelial tumours. As a common virus infection, EBV appears to have evolved to exploit the process of B cell development to persist as a life-long asymptomatic infection. However, the virus can contribute to oncogenesis as evidenced by its frequent detection in certain tumours, namely Burkitt's lymphoma (BL), post-transplant B cell lymphomas, Hodgkin's disease (HD) and nasopharyngeal carcinoma (NPC), and by its unique ability to efficiently transform resting B cells in vitro into permanently growing lymphoblastoid cell lines (LCLs). These transforming effects are associated with the restricted expression of EBV genes such that only a subset of so-called latent virus proteins are expressed in virus infected tumours and in LCLs. Distinct forms of EBV latency are manifest in the different tumours and these appear to be a vestige of the pattern of latent gene expression used by the virus during the establishment of persistent infection within the B cell pool. This review summarises our current knowledge of EBV latent gene function and how this relates to the role of the virus in the aetiology of different tumours.

Journal ArticleDOI
TL;DR: The immunosuppressant cyclosporin A (CsA) was found to have a suppressive effect on the HCV replicon RNA level and HCV protein expression in these cells.

Journal ArticleDOI
30 Oct 2003-Nature
TL;DR: It is shown that ferrets and domestic cats are susceptible to infection by SARS coronavirus (SCV) and that they can efficiently transmit the virus to previously uninfected animals that are housed with them.
Abstract: There is now a choice of animal models for testing therapies against the human virus. The reservoir of the coronavirus isolated from patients with severe acute respiratory syndrome (SARS)1,2 is still unknown, but is suspected to have been a wild animal species. Here we show that ferrets (Mustela furo) and domestic cats (Felis domesticus) are susceptible to infection by SARS coronavirus (SCV) and that they can efficiently transmit the virus to previously uninfected animals that are housed with them. The observation that these two distantly related carnivores can so easily be infected with the virus indicates that the reservoir for this pathogen may involve a range of animal species.

Journal ArticleDOI
TL;DR: The data indicate that most of the infectious HIV produced by primary macrophages is assembled on late endocytic membranes and acquires antigens characteristic of this compartment, which has significant implications for understanding the biology of HIV and its cell–cell transmission.
Abstract: Although human immunodeficiency virus type 1 (HIV-1) is generally thought to assemble at the plasma membrane of infected cells, virions have been observed in intracellular compartments in macrophages Here, we investigated virus assembly in HIV-1–infected primary human monocyte-derived macrophages (MDM) Electron microscopy of cryosections showed virus particles, identified by their morphology and positive labeling with antibodies to the viral p17, p24, and envelope proteins, in intracellular vacuoles Immunolabeling demonstrated that these compartments contained the late endosomal marker CD63, which was enriched on vesicles within these structures and incorporated into the envelope of budding virions The virus-containing vacuoles were also labeled with antibodies against LAMP-1, CD81, and CD82, which were also incorporated into the viral envelope To assess the cellular source of infectious viruses derived from MDM, virus-containing media from infected cells were precipitated with specific antibodies Only antibodies against antigens found in late endosomes precipitated infectious virus, whereas antibodies against proteins located primarily on the cell surface did not Our data indicate that most of the infectious HIV produced by primary macrophages is assembled on late endocytic membranes and acquires antigens characteristic of this compartment This notion has significant implications for understanding the biology of HIV and its cell–cell transmission

Journal ArticleDOI
TL;DR: It is described here how vaginal administration of the broadly neutralizing human monoclonal antibody b12 can protect macaques from simian-human immunodeficiency virus (SHIV) infection through the vagina, and observations support the concept that viral entry inhibitors can help prevent the sexual transmission of HIV-1 to humans.
Abstract: A topical microbicide reduces the probability of virus transmission when applied to the vagina or rectum of a person at risk of sexually acquiring HIV-1 infection1,2,3. An effective microbicide could significantly reduce the global spread of HIV-1, particularly if women were able to use it covertly to protect themselves. A microbicide could target the incoming virus and either permanently inactivate it or reduce its infectivity, or it could block receptors on susceptible cells near the sites of transmission1,2,3. We describe here how vaginal administration of the broadly neutralizing human monoclonal antibody b12 can protect macaques from simian-human immunodeficiency virus (SHIV) infection through the vagina. Only 3 of 12 animals receiving 5 mg b12 vaginally in either saline or a gel and then challenged vaginally (up to 2 h later) with SHIV-162P4 became infected. In contrast, infection occurred in 12 of 13 animals given various control agents under similar conditions. Lower amounts of b12 were less effective, suggesting that protection was dose dependent. These observations support the concept that viral entry inhibitors can help prevent the sexual transmission of HIV-1 to humans.

Journal ArticleDOI
07 Feb 2003-Science
TL;DR: Non-nucleosidic inhibitors of HBV nucleocapsid maturation that possess in vitro and in vivo antiviral activity are described and have potential for future therapeutic regimens to combat chronic HBV infection.
Abstract: Chronic hepatitis B virus (HBV) infection is a major cause of liver disease. Only interferon-alpha and the nucleosidic inhibitors of the viral polymerase, 3TC and adefovir, are approved for therapy. However, these therapies are limited by the side effects of interferon and the substantial resistance of the virus to nucleosidic inhibitors. Potent new antiviral compounds suitable for monotherapy or combination therapy are highly desired. We describe non-nucleosidic inhibitors of HBV nucleocapsid maturation that possess in vitro and in vivo antiviral activity. These inhibitors have potential for future therapeutic regimens to combat chronic HBV infection.