Showing papers on "Virus published in 2001"
TL;DR: The institution of blood-screening measures in developed countries has decreased the risk of transfusion-associated hepatitis to a negligible level, but new cases continue to occur mainly as a result of injection-drug use and, to a lesser degree, through other means of percutaneous or mucous-membrane exposure.
Abstract: Hepatitis C virus (HCV) infects an estimated 170 million persons worldwide and thus represents a viral pandemic, one that is five times as widespread as infection with the human immunodeficiency virus type 1 (HIV-1). The institution of blood-screening measures in developed countries has decreased the risk of transfusion-associated hepatitis to a negligible level, but new cases continue to occur mainly as a result of injection-drug use and, to a lesser degree, through other means of percutaneous or mucous-membrane exposure. Progression to chronic disease occurs in the majority of HCV-infected persons, and infection with the virus has become the main indication . . .
2,966 citations
TL;DR: The resultant primer set is suitable for all influenza A viruses to generate full-length cDNAs, to subtype viruses, to sequence their DNA, and to construct expression plasmids for reverse genetics systems.
Abstract: To systematically identify and analyze the 15 HA and 9 NA subtypes of influenza A virus, we need reliable, simple methods that not only characterize partial sequences but analyze the entire influenza A genome. We designed primers based on the fact that the 15 and 21 terminal segment specific nucleotides of the genomic viral RNA are conserved between all influenza A viruses and unique for each segment. The primers designed for each segment contain influenza virus specific nucleotides at their 3'-end and non-influenza virus nucleotides at the 5'-end. With this set of primers, we were able to amplify all eight segments of N1, N2, N4, N5, and N8 subtypes. For N3, N6, N7, and N9 subtypes, the segment specific sequences of the neuraminidase genes are different. Therefore, we optimized the primer design to allow the amplification of those neuraminidase genes as well. The resultant primer set is suitable for all influenza A viruses to generate full-length cDNAs, to subtype viruses, to sequence their DNA, and to construct expression plasmids for reverse genetics systems.
1,924 citations
TL;DR: Using reverse genetics, it is shown that a mutation at position 627 in the PB2 protein influenced the outcome of infection in mice, and high cleavability of the hemagglutinin glycoprotein was an essential requirement for lethal infection.
Abstract: In 1997, an H5N1 influenza A virus was transmitted from birds to humans in Hong Kong, killing 6 of the 18 people infected. When mice were infected with the human isolates, two virulence groups became apparent. Using reverse genetics, we showed that a mutation at position 627 in the PB2 protein influenced the outcome of infection in mice. Moreover, high cleavability of the hemagglutinin glycoprotein was an essential requirement for lethal infection.
1,267 citations
TL;DR: The virological and immunological features of hepatitis C virus (HCV) infection were studied weekly for 6 months after accidental needlestick exposure in five health care workers, four of whom developed acute hepatitis that progressed to chronicity while one subject cleared the virus.
Abstract: The virological and immunological features of hepatitis C virus (HCV) infection were studied weekly for 6 months after accidental needlestick exposure in five health care workers, four of whom developed acute hepatitis that progressed to chronicity while one subject cleared the virus. In all subjects, viremia was first detectable within 1–2 weeks of inoculation, 1 month or more before the appearance of virus-specific T cells. The subject who cleared the virus experienced a prolonged episode of acute hepatitis that coincided with a CD38+ IFN-γ− CD8+ T cell response to HCV and a small reduction in viremia. Subsequently, a strong CD4+ T cell response emerged and the CD8+ T cells became CD38− and started producing IFN-γ in response to HCV, coinciding with a rapid 100,000-fold decrease in viremia that occurred without a corresponding surge of disease activity. Chronic infection developed in two subjects who failed to produce a significant T cell response and in two other subjects who initially mounted strong CD4+ T cell responses that ultimately waned. In all subjects, viremia was higher at the peak of acute hepatitis than it was when the disease began, and the disease improved during the viremia. These results provide the first insight into the host–virus relationship in humans during the incubation phase of acute HCV infection, and they provide the only insight to date into the virological and immunological characteristics of clinically asymptomatic acute HCV infection, the commonest manifestation of this disease. In addition, the results suggest that the vigor and quality of the antiviral T cell response determines the outcome of acute HCV infection, that the ability of HCV to outpace the T cell response may contribute to its tendency to persist; that the onset of hepatitis coincides with the onset of the CD8+T cell response, that disease pathogenesis and viral clearance are mediated by different CD8+ T cell populations that control HCV by both cytolytic and noncytolytic mechanisms, and that there are different pathways to viral persistence in asymptomatic and symptomatic acute HCV infection.
1,192 citations
TL;DR: RSV and human parainfluenza virus types 1, 2, 3, and 4 have been known primarily as respiratory pathogens in young children but are now recognized as important pathogens in adults as well.
Abstract: Respiratory syncytial virus (RSV), originally recovered from a colony of chimpanzees with coryza and designated chimpanzee coryza agent,1,2 and human parainfluenza virus types 1, 2, 3, and 4 have been known primarily as respiratory pathogens in young children. They are now recognized as important pathogens in adults as well. Adults infected with these viruses tend to have more variable and less distinctive clinical findings than children, and the viral cause of the infection is often unsuspected. The consistency of the annual outbreaks of these agents and the frequency of reinfection suggest that they impose a considerable, but ill-defined, disease . . .
1,139 citations
TL;DR: This review provides a contemporary interpretation of the biological properties, function, epidemiology, and treatment of HSV diseases.
1,119 citations
Book•
25 Jan 2001
TL;DR: The basic model of virus dynamics, which describes the dynamics of resistance in different types of infected cells and analysis of multiple epitope dynamics shows clear trends in immune responses and drug resistance.
Abstract: Preface 1. Introduction: Viruses, immunity, equations 2. HIV 3. The basic model of virus dynamics 4. Anti-viral drug therapy 5. Dynamics of hepatitis B virus 6. Dynamics of immune responses 7. How fast do immune responses eliminate infected cells? 8. What is a quasispecies 9. The frequency of resistant mutant virus before anti-viral therapy 10. Emergence of drug resistance 11. Timing the emergence of resistance 12. Simple antigenic variation 13. Advanced antigenic variation 14. Multiple epitopes 15. Everything we know so far and beyond Appendix A - Dynamics of resistance in different types of infected cells Appendix B - Analysis of multiple epitope dynamics
1,049 citations
TL;DR: It is proposed that PB1-F2 functions to kill host immune cells responding to influenza virus infection, and influenza viruses with targeted mutations that interfere with PB1/F2 expression induce less extensive apoptosis in human monocytic cells than those with intact PB1 -F2.
Abstract: While searching for alternative reading-frame peptides encoded by influenza A virus that are recognized by CD8+ T cells, we found an abundant immunogenic peptide encoded by the +1 reading frame of PB1. This peptide derives from a novel conserved 87-residue protein, PB1-F2, which has several unusual features compared with other influenza gene products in addition to its mode of translation. These include its absence from some animal (particularly swine) influenza virus isolates, variable expression in individual infected cells, rapid proteasome-dependent degradation and mitochondrial localization. Exposure of cells to a synthetic version of PB1-F2 induces apoptosis, and influenza viruses with targeted mutations that interfere with PB1-F2 expression induce less extensive apoptosis in human monocytic cells than those with intact PB1-F2. We propose that PB1-F2 functions to kill host immune cells responding to influenza virus infection.
1,016 citations
TL;DR: The interferon system is the first line of defense against viral infection in mammals designed to block the spread of virus infection in the body, sometimes at the expense of accelerating the death of the infected cells.
Abstract: The interferon system is the first line of defense against viral infection in mammals. This system is designed to block the spread of virus infection in the body, sometimes at the expense of accelerating the death of the infected cells. As expected of potent cytokines, in addition to their antiviral effects, interferons have profound effects on many aspects of cell physiology. All these actions of interferons are mediated by hundreds of interferon-induced proteins that are usually not synthesized in resting cells. Interferons induce their synthesis by activating the Jak-STAT pathways, a paradigm of cell signaling used by many cytokines and growth factors. Surprisingly, some of the same genes can also be induced directly by viruses and double-stranded RNA, a common viral by-product. Some of the interferon-induced proteins have novel biochemical properties and some are inactive as such but can be activated by double-stranded RNA produced during virus infection. Finally, almost all viruses have evolved mechanisms to evade the interferon system by partially blocking interferon synthesis or interferon action. Thus, in nature interferons and viruses maintain an equilibrium that allows regulated viral replication.
955 citations
TL;DR: Two genes encoded by the virus — LMP1 and LMP2A — allow EBV to exploit the normal pathways of B-cell differentiation so that the EBV-infected B blast can become a resting memory cell.
Abstract: In vitro, Epstein-Barr virus (EBV) will infect any resting B cell, driving it out of the resting state to become an activated proliferating lymphoblast. Paradoxically, EBV persists in vivo in a quiescent state in resting memory B cells that circulate in the peripheral blood. How does the virus get there, and with such specificity for the memory compartment? An explanation comes from the idea that two genes encoded by the virus--LMP1 and LMP2A--allow EBV to exploit the normal pathways of B-cell differentiation so that the EBV-infected B blast can become a resting memory cell.
923 citations
TL;DR: It is demonstrated that ribavirin's antiviral activity is exerted directly through lethal mutagenesis of the viral genetic material, suggesting that RNA virus mutagens may represent a promising new class of antiviral drugs.
Abstract: RNA viruses evolve rapidly. One source of this ability to rapidly change is the apparently high mutation frequency in RNA virus populations. A high mutation frequency is a central tenet of the quasispecies theory. A corollary of the quasispecies theory postulates that, given their high mutation frequency, animal RNA viruses may be susceptible to error catastrophe, where they undergo a sharp drop in viability after a modest increase in mutation frequency. We recently showed that the important broad-spectrum antiviral drug ribavirin (currently used to treat hepatitis C virus infections, among others) is an RNA virus mutagen, and we proposed that ribavirin's antiviral effect is by forcing RNA viruses into error catastrophe. However, a direct demonstration of error catastrophe has not been made for ribavirin or any RNA virus mutagen. Here we describe a direct demonstration of error catastrophe by using ribavirin as the mutagen and poliovirus as a model RNA virus. We demonstrate that ribavirin's antiviral activity is exerted directly through lethal mutagenesis of the viral genetic material. A 99.3% loss in viral genome infectivity is observed after a single round of virus infection in ribavirin concentrations sufficient to cause a 9.7-fold increase in mutagenesis. Compiling data on both the mutation levels and the specific infectivities of poliovirus genomes produced in the presence of ribavirin, we have constructed a graph of error catastrophe showing that normal poliovirus indeed exists at the edge of viability. These data suggest that RNA virus mutagens may represent a promising new class of antiviral drugs.
TL;DR: It is shown that passive intravenous transfer of the human neutralizing monoclonal antibody b12 provides dose-dependent protection to macaques vaginally challenged with the R5 virus SHIV162P4, suggesting that a vaccine based on antibody alone would need to sustain serum neutralizing antibody titers of the order of 1:400 to achieve sterile protection but that lower titers, around 1:100, could provide a significant benefit.
Abstract: A major unknown in human immunodeficiency virus (HIV-1) vaccine design is the efficacy of antibodies in preventing mucosal transmission of R5 viruses. These viruses, which use CCR5 as a coreceptor, appear to have a selective advantage in transmission of HIV-1 in humans. Hence R5 viruses predominate during primary infection and persist throughout the course of disease in most infected people. Vaginal challenge of macaques with chimeric simian/human immunodeficiency viruses (SHIV) is perhaps one of the best available animal models for human HIV-1 infection. Passive transfer studies are widely used to establish the conditions for antibody protection against viral challenge. Here we show that passive intravenous transfer of the human neutralizing monoclonal antibody b12 provides dose-dependent protection to macaques vaginally challenged with the R5 virus SHIV(162P4). Four of four monkeys given 25 mg of b12 per kg of body weight 6 h prior to challenge showed no evidence of viral infection (sterile protection). Two of four monkeys given 5 mg of b12/kg were similarly protected, whereas the other two showed significantly reduced and delayed plasma viremia compared to control animals. In contrast, all four monkeys treated with a dose of 1 mg/kg became infected with viremia levels close to those for control animals. Antibody b12 serum concentrations at the time of virus challenge corresponded to approximately 400 (25 mg/kg), 80 (5 mg/kg), and 16 (1 mg/kg) times the in vitro (90%) neutralization titers. Therefore, complete protection against mucosal challenge with an R5 SHIV required essentially complete neutralization of the infecting virus. This suggests that a vaccine based on antibody alone would need to sustain serum neutralizing antibody titers (90%) of the order of 1:400 to achieve sterile protection but that lower titers, around 1:100, could provide a significant benefit. The significance of such substerilizing neutralizing antibody titers in the context of a potent cellular immune response is an important area for further study.
TL;DR: The cellular immune response to the human immunodeficiency virus, mediated by T lymphocytes, seems strong but fails to control the infection completely, and the failure of the latter to function efficiently facilitates the escape of virus from immune control and the collapse of the whole immune system.
Abstract: The cellular immune response to the human immunodeficiency virus, mediated by T lymphocytes, seems strong but fails to control the infection completely. In most virus infections, T cells either eliminate the virus or suppress it indefinitely as a harmless, persisting infection. But the human immunodeficiency virus undermines this control by infecting key immune cells, thereby impairing the response of both the infected CD4+ T cells and the uninfected CD8+ T cells. The failure of the latter to function efficiently facilitates the escape of virus from immune control and the collapse of the whole immune system.
TL;DR: The role of spike protein projections as agents of organ tropism and pathogenesis began with comparative studies of different naturally occurring mouse hepatitis viruses (MHV) strains as discussed by the authors, which revealed that alterations in virus virulence were most closely associated with differences in the spike gene.
TL;DR: The results indicate that most MAbs that neutralize virus infectivity do so, at least in part, by the blocking of virus adsorption, and provide the first direct evidence that domain III encodes the primary flavivirus receptor-binding motif.
Abstract: The specific mechanisms by which antibodies neutralize flavivirus infectivity are not completely understood. To study these mechanisms in more detail, we analyzed the ability of a well-defined set of anti-dengue (DEN) virus E-glycoprotein-specific monoclonal antibodies (MAbs) to block virus adsorption to Vero cells. In contrast to previous studies, the binding sites of these MAbs were localized to one of three structural domains (I, II, and III) in the E glycoprotein. The results indicate that most MAbs that neutralize virus infectivity do so, at least in part, by the blocking of virus adsorption. However, MAbs specific for domain III were the strongest blockers of virus adsorption. These results extend our understanding of the structure-function relationships in the E glycoprotein of DEN virus and provide the first direct evidence that domain III encodes the primary flavivirus receptor-binding motif.
TL;DR: A focussed review of apoptosis is provided and illustrates how the study of viruses has informed the understanding of this process, including selected mechanisms by which viral gene products interfere with cell death.
Abstract: Apoptosis, or programmed cell death, is essential in development and homeostasis in multi-cellular organisms. It is also an important component of the cellular response to injury. Many cells undergo apoptosis in response to viral infection, with a consequent reduction in the release of progeny virus. Viruses have therefore evolved multiple distinct mechanisms for modulating host cell apoptosis. Viruses may interfere with either the highly conserved 'effector' mechanisms of programmed cell death or regulatory mechanisms specific to mammalian cells. In addition to conferring a selective advantage to the virus, the capacity to prevent apoptosis has an essential role in the transformation of the host cell by oncogenic viruses. This article provides a focussed review of apoptosis and illustrates how the study of viruses has informed our understanding of this process. Selected mechanisms by which viral gene products interfere with cell death are discussed in detail and used to illustrate the general principles of the interactions between viruses and apoptosis.
TL;DR: The identification of avian viruses in humans underscores the potential of these and similar strains to produce devastating influenza outbreaks in major population centers.
Abstract: Influenza pandemics, defined as global outbreaks of the disease due to viruses with new antigenic subtypes, have exacted high death tolls from human populations. The last two pandemics were caused by hybrid viruses, or reassortants, that harbored a combination of avian and human viral genes. Avian influenza viruses are therefore key contributors to the emergence of human influenza pandemics. In 1997, an H5N1 influenza virus was directly transmitted from birds in live poultry markets in Hong Kong to humans. Eighteen people were infected in this outbreak, six of whom died. This avian virus exhibited high virulence in both avian and mammalian species, causing systemic infection in both chickens and mice. Subsequently, another avian virus with the H9N2 subtype was directly transmitted from birds to humans in Hong Kong. Interestingly, the genes encoding the internal proteins of the H9N2 virus are genetically highly related to those of the H5N1 virus, suggesting a unique property of these gene products. The identification of avian viruses in humans underscores the potential of these and similar strains to produce devastating influenza outbreaks in major population centers. Although highly pathogenic avian influenza viruses had been identified before the 1997 outbreak in Hong Kong, their devastating effects had been confined to poultry. With the Hong Kong outbreak, it became clear that the virulence potential of these viruses extended to humans.
TL;DR: 4E10 neutralizes potently not only tissue culture-adapted strains but also primary isolates of different clades, including A, B, C, D, and E, confirming that the region recognized by 2F5 and 4E10 is essential for viral infectivity and may be important for vaccine design.
Abstract: We have established a panel of human monoclonal antibodies against human immunodeficiency virus type 1 (HIV-1). The antibodies 2F5 and 2G12 have been identified to be two of the most potently in vitro neutralizing antibodies against HIV-1. Here we report on a further antibody, 4E10, of similar in vitro neutralizing potency. 4E10 binds to a novel epitope C terminal of the ELDKWA sequence recognized by 2F5, which has been so far the only described broadly neutralizing anti-gp41 antibody. Both 4E10 and 2F5 bind only weakly to infected cells compared with gp120-specific 2G12 and polyclonal anti-HIV-1 immunoglobulin (HIVIG), but show potent in vitro neutralizing properties. 4E10 neutralizes potently not only tissue culture-adapted strains but also primary isolates of different clades, including A, B, C, D, and E. Viruses that were found to be resistant to 2F5 were neutralized by 4E10 and vice versa; none of the tested isolates was resistant to both anti-gp41 antibodies. This confirms that the region recognized...
TL;DR: It is suggested that virus-encoded IL-4 not only suppresses primary antiviral cell-mediated immune responses but also can inhibit the expression of immune memory responses, similar to the disease seen when genetically sensitive mice are infected with the virulent Moscow strain.
Abstract: Genetic resistance to clinical mousepox (ectromelia virus) varies among inbred laboratory mice and is characterized by an effective natural killer (NK) response and the early onset of a strong CD8 1 cytotoxic T-lymphocyte (CTL) response in resistant mice. We have investigated the influence of virus-expressed mouse interleukin-4 (IL-4) on the cell-mediated response during infection. It was observed that expression of IL-4 by a thymidine kinase-positive ectromelia virus suppressed cytolytic responses of NK and CTL and the expression of gamma interferon by the latter. Genetically resistant mice infected with the IL-4-expressing virus developed symptoms of acute mousepox accompanied by high mortality, similar to the disease seen when genetically sensitive mice are infected with the virulent Moscow strain. Strikingly, infection of recently immunized genetically resistant mice with the virus expressing IL-4 also resulted in significant mortality due to fulminant mousepox. These data therefore suggest that virus-encoded IL-4 not only suppresses primary antiviral cellmediated immune responses but also can inhibit the expression of immune memory responses. Ectromelia virus (ECTV; family Poxviridae, genus Orthopoxvirus) is a natural pathogen of laboratory mice that causes a generalized disease termed mousepox (13). All mice are equally susceptible to infection by footpad inoculation; however, development of clinical mousepox among inbred mouse strains differs greatly (44). In mousepox-sensitive (e.g., BALB/c) mice, the disease is an acute systemic infection with high viral titers in the liver and spleen with resultant necrosis and high mortality. In contrast, infection of mousepox-resistant (e.g., C57BL/6) mice is usually subclinical, with lower levels of viral replication in the visceral organs and development of nonfatal lesions. Genetic resistance has been found to act through the combined activity of innate host defenses including natural killer (NK) cells, alpha interferon (IFN-a), IFN-b, IFN-g, ac
TL;DR: Overall, HCV-specific CD8+T lymphocytes show reduced synthesis of tumor necrosis factor alpha and gamma interferon after stimulation with either mitogens or peptides, compared to responses to Epstein-Barr virus and/or cytomegalovirus.
Abstract: Hepatitis C virus (HCV) sets up persistent infection in the majority of those exposed. It is likely that, as with other persistent viral infections, the efficacy of T-lymphocyte responses influences long-term outcome. However, little is known about the functional capacity of HCV-specific T-lymphocyte responses induced after acute infection. We investigated this by using major histocompatibility complex class I-peptide tetrameric complexes (tetramers), which allow direct detection of specific CD8+ T lymphocytes ex vivo, independently of function. Here we show that, early after infection, virus-specific CD8+ T lymphocytes detected with a panel of four such tetramers are abnormal in terms of their synthesis of antiviral cytokines and lytic activity. Furthermore, this phenotype is commonly maintained long term, since large sustained populations of HCV-specific CD8+ T lymphocytes were identified, which consistently had very poor antiviral cytokine responses as measured in vitro. Overall, HCV-specific CD8+ T lymphocytes show reduced synthesis of tumor necrosis factor alpha (TNF-alpha) and gamma interferon (IFN-gamma) after stimulation with either mitogens or peptides, compared to responses to Epstein-Barr virus and/or cytomegalovirus. This behavior of antiviral CD8+ T lymphocytes induced after HCV infection may contribute to viral persistence through failure to effectively suppress viral replication.
TL;DR: Findings suggest that Toll signaling pathways have an important role in innate immunity to RSV.
Abstract: The mammalian Toll-like receptor 4, TLR4, is an important component in the innate immune response to gram-negative bacterial infection. The role of TLR4 in antiviral immunity has been largely unexplored. In this study, the in vivo immune responses to respiratory syncytial virus (RSV) and influenza virus infection were examined in TLR4-deficient (C57BL/10ScNCr) and TLR4-expressing (C57BL/10Sn) mice. TLR4-deficient mice challenged with RSV, but not influenza virus, exhibited impaired natural killer (NK) cell and CD14(+) cell pulmonary trafficking, deficient NK cell function, impaired interleukin-12 expression, and impaired virus clearance compared to mice expressing TLR4. These findings suggest that Toll signaling pathways have an important role in innate immunity to RSV.
TL;DR: It is shown that infection of cells with influenza A virus leads to biphasic activation of the Raf/MEK/ERK cascade, which seems to be essential for virus production and RNP export from the nucleus during the viral life cycle.
Abstract: Influenza A viruses are important worldwide pathogens in humans and different animal species. The functions of most of the ten different viral proteins of this negative-strand RNA virus have been well elucidated. However, little is known about the virus-induced intracellular signalling events that support viral replication. The Raf/MEK/ERK cascade is the prototype of mitogen-activated protein (MAP) kinase cascades and has an important role in cell growth, differentiation and survival. Investigation of the function of this pathway has been facilitated by the identification of specific inhibitors such as U0126, which blocks the cascade at the level of MAPK/ERK kinase (MEK). Here we show that infection of cells with influenza A virus leads to biphasic activation of the Raf/MEK/ERK cascade. Inhibition of Raf signalling results in nuclear retention of viral ribonucleoprotein complexes (RNPs), impaired function of the nuclear-export protein (NEP/NS2) and concomitant inhibition of virus production. Thus, signalling through the mitogenic cascade seems to be essential for virus production and RNP export from the nucleus during the viral life cycle.
TL;DR: Phylogenetic analyses indicated that substitutions emerged under natural selection rather than by genetic drift or linkage for outgrowth of CTL escape viruses required high viral loads and additional, possibly compensatory, mutations in the gag protein.
Abstract: The immune response to HIV-1 in patients who carry human histocompatibility leukocyte antigen (HLA)-B27 is characterized by an immunodominant response to an epitope in p24 gag (amino acids 263–272, KRWIILGLNK). Substitution of lysine (K) or glycine (G) for arginine (R) at HIV-1 gag residue 264 (R264K and R264G) results in epitopes that bind to HLA-B27 poorly. We have detected a R264K mutation in four patients carrying HLA-B27. In three of these patients the mutation occurred late, coinciding with disease progression. In another it occurred within 1 yr of infection and was associated with a virus of syncytium-inducing phenotype. In each case, R264K was tightly associated with a leucine to methionine change at residue 268. After the loss of the cytotoxic T lymphocyte (CTL) response to this epitope and in the presence of high viral load, reversion to wild-type sequence was observed. In a fifth patient, a R264G mutation was detected when HIV-1 disease progressed. Its occurrence was associated with a glutamic acid to aspartic acid mutation at residue 260. Phylogenetic analyses indicated that these substitutions emerged under natural selection rather than by genetic drift or linkage. Outgrowth of CTL escape viruses required high viral loads and additional, possibly compensatory, mutations in the gag protein.
TL;DR: This method simultaneously detects influenza viruses A and B in specimens of patients with respiratory infections using a TaqMan-based real-time PCR assay, which was found to be more sensitive than the combination of conventional viral culturing and shell vial culturing.
Abstract: Since influenza viruses can cause severe illness, timely diagnosis is important for an adequate intervention. The available rapid detection methods either lack sensitivity or require complex laboratory manipulation. This study describes a rapid, sensitive detection method that can be easily applied to routine diagnosis. This method simultaneously detects influenza viruses A and B in specimens of patients with respiratory infections using a TaqMan-based real-time PCR assay. Primers and probes were selected from highly conserved regions of the matrix protein gene of influenza virus A and the hemagglutinin gene segment of influenza virus B. The applicability of this multiplex PCR was evaluated with 27 influenza virus A and 9 influenza virus B reference strains and isolates. In addition, the specificity of the assay was assessed using eight reference strains of other respiratory viruses (parainfluenza viruses 1 to 3, respiratory syncytial virus Long strain, rhinoviruses 1A and 14, and coronaviruses OC43 and 229E) and 30 combined nose and throat swabs from asymptomatic subjects. Electron microscopy-counted stocks of influenza viruses A and B were used to develop a quantitative PCR format. Thirteen copies of viral RNA were detected for influenza virus A, and 11 copies were detected for influenza virus B, equaling 0.02 and 0.006 50% tissue culture infective doses, respectively. The diagnostic efficacy of the multiplex TaqMan-based PCR was determined by testing 98 clinical samples. This real-time PCR technique was found to be more sensitive than the combination of conventional viral culturing and shell vial culturing.
TL;DR: A subgenomic replicon is constructed from a known infectious HCV clone and it is demonstrated that it has an approximately 1,000-fold-higher transduction efficiency than previously used subgenomes and was sensitive to IFN-α independently of whether the replicon expressed an NS5A protein associated with sensitivity or resistance to the cytokine.
Abstract: Chronic hepatitis C virus (HCV) infections can be cured only in a fraction of patients treated with alpha interferon (IFN-α) and ribavirin combination therapy. The mechanism of the IFN-α response against HCV is not understood, but evidence for a role for viral nonstructural protein 5A (NS5A) in IFN resistance has been provided. To elucidate the mechanism by which NS5A and possibly other viral proteins inhibit the cellular antiviral program, we have constructed a subgenomic replicon from a known infectious HCV clone and demonstrated that it has an approximately 1,000-fold-higher transduction efficiency than previously used subgenomes. We found that IFN-α reduced replication of HCV subgenomic replicons approximately 10-fold. The estimated half-life of viral RNA in the presence of the cytokine was about 12 h. HCV replication was sensitive to IFN-α independently of whether the replicon expressed an NS5A protein associated with sensitivity or resistance to the cytokine. Furthermore, our results indicated that HCV replicons can persist in Huh7 cells in the presence of high concentrations of IFN-α. Finally, under our conditions, selection for IFN-α-resistant variants did not occur.
TL;DR: This recombinant antigen has great potential to become the antigen of choice and will facilitate the standardization of reagents and implementation of WN virus surveillance in the United States and elsewhere.
Abstract: Introduction of West Nile (WN) virus into the United States in 1999 created major human and animal health concerns. Currently, no human or veterinary vaccine is available to prevent WN viral infection, and mosquito control is the only practical strategy to combat the spread of disease. Starting with a previously designed eukaryotic expression vector, we constructed a recombinant plasmid (pCBWN) that expressed the WN virus prM and E proteins. A single intramuscular injection of pCBWN DNA induced protective immunity, preventing WN virus infection in mice and horses. Recombinant plasmid-transformed COS-1 cells expressed and secreted high levels of WN virus prM and E proteins into the culture medium. The medium was treated with polyethylene glycol to concentrate proteins. The resultant, containing high-titered recombinant WN virus antigen, proved to be an excellent alternative to the more traditional suckling-mouse brain WN virus antigen used in the immunoglobulin M (IgM) antibody-capture and indirect IgG enzyme-linked immunosorbent assays. This recombinant antigen has great potential to become the antigen of choice and will facilitate the standardization of reagents and implementation of WN virus surveillance in the United States and elsewhere.
TL;DR: An AIDS vaccine based on attenuated VSV vectors expressing env and gag genes and tested it in rhesus monkeys, finding protection from AIDS was highly significant.
TL;DR: It is postulated that in fatal human infections with this avian subtype, initial virus replication in the respiratory tract triggers hypercytokinemia complicated by the reactive hemophagocytic syndrome.
Abstract: Eighteen cases of human influenza A H5N1 infection were identified in Hong Kong from May to December 1997. Two of the six fatal cases had undergone a full post-mortem which showed reactive hemophagocytic syndrome as the most prominent feature. Other findings included organizing diffuse alveolar damage with interstitial fibrosis, extensive hepatic central lobular necrosis, acute renal tubular necrosis and lymphoid depletion. Elevation of soluble interleukin-2 receptor, interleukin-6 and interferon-gamma was demonstrated in both patients, whereas secondary bacterial pneumonia was not observed. Virus detection using isolation, reverse transcription-polymerase chain reaction and immunostaining were all negative. It is postulated that in fatal human infections with this avian subtype, initial virus replication in the respiratory tract triggers hypercytokinemia complicated by the reactive hemophagocytic syndrome. These findings suggest that the pathogenesis of influenza A H5N1 infection might be different from that of the usual human subtypes H1-H3.
TL;DR: An overview of the present knowledge about the antiviral activities of Lactoferrin is given and, when possible, the antiv viral modes of action of this protein are given.
TL;DR: Chronic infection by HCV is associated with an allostimulatory defect of monocyte-derived DC, possibly because these cells constitute an extrahepatic reservoir for the virus, which argues against an active immunosuppression-based mechanism.