Virus particles, composition

The structures of virions (virus particles) are quite diverse. Viruses vary widely in size, shape, and chemical composition. The... 

Electron microscopic studies have suggested that the alphavirus particle has icosahedral symmetry (see below). The triangulation number is not certain, however (Murphy, 1980). Previous estimates for the molecular weight were compatible with 240 subunits per virus particle, and electron micrographs appear to show a T = 4 surface lattice (von Bons-dorff and Harrison, 1975). More information is now needed to determine the surface organization, since compositional data show fewer than 240 subunits. 

The industrial application of CLPs and VLPs is in the development phase. This can be expected since the baculovirus-insect cells system has become one of the most popular systems for heterologous protein and CLP/VLP production at laboratory scale. After defining the appropriate particle composition for the viruses of interest, research is now addressing the engineering issues in this system (Scheme 1). 

The same PDA fusion methodology was also used to study attaehment, perturbation of the membrane, and entry of vaeeinia virus to the cell membrane. The PDA patch was introduced on epithelial cell membranes and polymerized. Attachment of viral particle to the membranes induced changes in color (blue to red) and emission spectra. It was observed that the lipid composition of the membrane had a profound effect for the interactions of the PDA labeled cells with the virus particles. Membrane domains or lipid rafts rich in cholesterol and sphingomylein favored the interactions with the vaccinia virus. 

Composition of Virus Particles. Many viruses have been prepared pure, some even in crystalline form. The simplest among them chemically are nucleoproteins they consist of protein and nucleic acid (usually DNA with some plant viruses, e.g. tobacco mosaic virus, it is RNA). Larger viruses are more variable, which means they can no longer be regarded as chemically definable nucleoproteins. 

Further studies on viral coat function became feasible when it was found that diethylpyrocarbonate (DEP, Baycovine, Naftone Inc., New York) inactivates pohoviruses without impairing the structure and function of the RNA (tested after phenol extraction) (Oberg, 1970 Breindl and Koch, 1972), and without converting the virus particle in any way that makes its RNA sensitive to attack by ribonuclease. In a typical experiment, poliovirus was inactivated by a saturated DEP dilution (1.0%) in phosphate-buffered saline (inactivation more than 7 log units within 30 min at room temperature). However, when the DEP-treated virus was tested with HeLa cells sensitized to infection by viral RNA, the inactivated virus particles showed the same infectivity as isolated RNA. Furthermore, DEP treatment of polioviruses did not alter the major physical properties of the virus, i.e. its sedimentation rate in sucrose and its density in CsCl. Also, the polypeptide composition of native and DEP poliovirus in SDS acrylamide gels are identical (Oberg, 1970 Breindl and Koch, 1972). 

Oxford, J. S., 1973, Polypeptide composition of influenza B viruses and enzymes associated with the purified virus particles, J. Virol. 12 827-835. 

In this paper the fundamental aspects of process development for the production of core and virus-like particles with baculovirus infected insect cells are reviewed. The issues addressed include particle formation and monomer composition, chemical and physical conditions for optimal cell growth, baculovirus replication and product expression, multiplicity of infection strategy, and scale-up of the process. Study of the differences in the metabolic requirements of infected and non-infected cells is necessary for high cell density processes. In the bioreactor, the specific oxygen uptake rate (OURsp) plays a central role in process scale-up, leading to the specification of the bioreactor operational parameters. Shear stress can also be an important variable for bioreactor operation due to its influence on cell growth and product expression. 

Taking into account process integration, i.e. - cultivation and product purification, particle locaHsation is an important issue. Strategies to produce a secreted particle, either by manipulation of its composition or by co-expression of NS protein(s) will be also discussed, since this can lead to an easier purification process and to a decrease in product losses due to intracellular proteolysis. The production of Rotavirus-Hke particles and Bluetongue virus-like particles production will be used as examples to illustrate this point. 

The present invention is generally directed to the use of silver, at a level of 5 to 40 ppm in water, to kill or to disable microorganisms, such as avian influenza virus, which are hazardous to human beings. The present invention specifically is directed to compositions comprising silver particles, said particles comprising an interior of elemental silver and an exterior of ionic silver oxide, and water, wherein the silver particles are placed in colloidal suspension in the water at a level of 5-40 ppm total silver. An embodiment of the present invention comprises silver particles in water, at a concentration of 5-40 ppm, wherein more... 

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