Hydrostatic pressure induces the fusion-active state of enveloped viruses.
(9/191)
Enveloped animal viruses must undergo membrane fusion to deliver their genome into the host cell. We demonstrate that high pressure inactivates two membrane-enveloped viruses, influenza and Sindbis, by trapping the particles in a fusion-intermediate state. The pressure-induced conformational changes in Sindbis and influenza viruses were followed using intrinsic and extrinsic fluorescence spectroscopy, circular dichroism, and fusion, plaque, and hemagglutination assays. Influenza virus subjected to pressure exposes hydrophobic domains as determined by tryptophan fluorescence and by the binding of bis-8-anilino-1-naphthalenesulfonate, a well established marker of the fusogenic state in influenza virus. Pressure also produced an increase in the fusion activity at neutral pH as monitored by fluorescence resonance energy transfer using lipid vesicles labeled with fluorescence probes. Sindbis virus also underwent conformational changes induced by pressure similar to those in influenza virus, and the increase in fusion activity was followed by pyrene excimer fluorescence of the metabolically labeled virus particles. Overall we show that pressure elicits subtle changes in the whole structure of the enveloped viruses triggering a conformational change that is similar to the change triggered by low pH. Our data strengthen the hypothesis that the native conformation of fusion proteins is metastable, and a cycle of pressure leads to a final state, the fusion-active state, of smaller volume. (+info)
Virus infections: escape, resistance, and counterattack.
(10/191)
Many viruses establish life-long infections in their natural host with few if any clinical manifestations. The relationship between virus and host is a dynamic process in which the virus has evolved the means to coexist by reducing its visibility, while the host immune system attempts to suppress and eliminate infection without damage to itself. This short review describes a variety of strategies that are employed by viruses to evade host immune responses. These include virus-associated escape from T cell recognition, and resistance to apoptosis and counterattack, with special reference to two papers published in this issue of Immunity (Mueller et al., 2001; Raftery et al., 2001). (+info)
Structure and function of the eukaryotic ribosome: the next frontier.
(11/191)
As the catalytic and regulatory centers of protein synthesis in cells, ribosomes are central to many aspects of cell and structural biology. Recent work highlights the unique properties and complexity of eukaryotic ribosomes and their component rRNAs and proteins. (+info)
Occupancy and mechanism in antibody-mediated neutralization of animal viruses.
(12/191)
Neutralization of virus infectivity by antibodies is an important component of immunity to several virus infections. Here, the immunochemical basis for the action of neutralizing antibodies, and what role their induction of conformational changes in the antigen might play, is reviewed. Theories of the mechanisms by which antibodies neutralize virus infectivity in vitro are also presented. The theoretical and empirical foundation of the hypothesis that viruses are neutralized by a single antibody per virion is critically reviewed. The relationship between antibody occupancy on virions and the mechanism of neutralization is explored. Examples of neutralization mediated through antibody interference with virus attachment and entry are discussed and test implications of refined theories of neutralization by antibody coating of virions are formulated. (+info)
Viruses in and out.
(13/191)
A report on the twelfth Congress of Virology, part of 'The world of microbes', the joint meeting of the three divisions of the International Union of Microbiological Societies, Paris, France, 27 July to 1 August 2002 (+info)
Validation and analysis of a mathematical model of a replication-competent oncolytic virus for cancer treatment: implications for virus design and delivery.
(14/191)
Motivated by the rapid expansion in the development of replication-competent viral agents for the treatment of solid tumors, we formulated and analyzed a three-dimensional mathematical model of a tumor that is infected by a replication-competent virus. We initially considered three patterns of intratumoral injection in which a fixed fraction of cells are initially infected with the virus throughout (a) the entire tumor, (b) the tumor core, and (c) the tumor rim, respectively. For each injection pattern, an approximate analysis of the model provides a simple and accurate condition for whether the virus will eradicate the tumor. The model was then generalized to incorporate nutrient-limited necrosis and an innate immune response against virus-infected tumor cells. Recent preclinical and clinical data were used to validate the model and estimate key parameter values. Our analysis has the following implications: even in the absence of an immune response, tumor eradication requires widespread distribution of the virus within the tumor at the time of infection; core or rim injections alone may result in tumor escape, particularly in a well-vascularized tumor; the more rapidly a virus lyses infected cells the more effective it will be at controlling the tumor; and the innate immune response to the virus can potentially prevent the virus from controlling the tumor, even with repeat injections. Therefore, in addition to diffuse intratumoral infection, tumor eradication by oncolytic adenovirus will probably require potent suppression of innate immune clearance mechanisms (e.g., by replacement of adenovirus E3 genes), combinations with traditional (chemotherapy, radiotherapy) treatments, and/or concomitant therapeutic gene expression with resultant bystander effects. (+info)
Viral mimicry of the complement system.
(15/191)
The complement system is a potent innate immune mechanism consisting of cascades of proteins which are designed to fight against and annul intrusion of all the foreign pathogens. Although viruses are smaller in size and have relatively simple structure, they are not immune to complement attack. Thus, activation of the complement system can lead to neutralization of cell-free viruses, phagocytosis of C3b-coated viral particles, lysis of virus-infected cells, and generation of inflammatory and specific immune responses. However, to combat host responses and succeed as pathogens, viruses not only have developed/adopted mechanisms to control complement, but also have turned these interactions to their own advantage. Important examples include poxviruses, herpesviruses, retroviruses, paramyxoviruses and picornaviruses. In this review, we provide information on the various complement evasion strategies that viruses have developed to thwart the complement attack of the host. A special emphasis is given on the interactions between the viral proteins that are involved in molecular mimicry and the complement system. (+info)
Host-pathogen interactions during apoptosis.
(16/191)
Host pathogen interaction results in a variety of responses, which include phagocytosis of the pathogen, release of cytokines, secretion of toxins, as well as production of reactive oxygen species (ROS). Recent studies have shown that many pathogens exert control on the processes that regulate apoptosis in the host. The induction of apoptosis upon infection results from a complex interaction of parasite proteins with cellular host proteins. Abrogation of host cell apoptosis is often beneficial for the pathogen and results in a successful host invasion. However, in some cases, it has been shown that induction of apoptosis in the infected cells significantly imparts protection to the host from the pathogen. There is a strong correlation between apoptosis and the host protein translation machinery: the pathogen makes all possible efforts to modify this process so as to inhibit cell suicide and ensure that it can survive and, in some cases, establish latent infection. This review discusses the significance of various pathways/steps during virus-mediated modulation of host cell apoptosis. (+info)