Viruses general discussion

We have presented considerable evidence that poliovirus type 1, strain LSc2ab, adsorbs on inorganic surfaces according to the electrodynamic and electrostatic potentials defined by the DLVO-Lifshitz theory of colloid stability. We shall now present a general discussion concerning the predicted implications these findings have in regard to the overall problem of virus transport in the environment. 

The unique properties and particular importance of smallpox virus are discussed, both as a bioterrorism threat and as a major biohazard in general. It appears to pose, potentially, a colossal menace, which ought to be intensely coped with. The issues of renewed vaccination and ongoing research are then addressed, showing the complexity related to that singular pathogen. 

Anderson, S.G., Burnet FA4., Fazekas de St. Groth, S., McCrea, Jf., and Stone, JJ). (1948) Mucins and mucoids in relation to influenza virus action.VI. General discussion. Australian Journal of Experimental Biology and Medical Science, 26,403—411. 

On occasion, it may be necessary to postpone the regular immunization schedule, particularly for children. This is of special concern to parents. The decision to delay immunization because of illness or for other reasons must be discussed with the primary health care provider. However, the decision to administer or delay vaccination because of febrile illness (illness causing an elevated temperature) depends on the severity of the symptoms and the specific disorder. In general, all vaccines can be administered to those with minor illness, such as a cold virus and to those with a low-grade fever. However, moderate or severe febrile illness is a contraindication. hi instances of moderate or severe febrile illness, vaccination is done as soon as the acute phase of... 

We have discussed in a general way the nature of animal viruses in the first part of this chapter. Now we discuss in some detail the structure and molecular biology of a number of important animal viruses. Viruses will be discussed which illustrate different ways of replicating, and both RNA and DNA viruses will be covered. One group of animal viruses, those called the retroviruses, have both an RNA and a DNA phase of replication. Retroviruses are especially interesting not only because of their unusual mode of replication, but because retroviruses cause such important diseases as certain cancers and acquired immunodeficiency syndrome (AIDS). 

An alternative to the use of purified protein would be to insert the appropriate genes into the human cells, either generally or in the specific target cells, and allow the cells to function naturally. This approach has been tried clinically in a number of diseases but not with any conspicuous success. Part of the problem here is how to insert the gene into the appropriate cell, as discussed earlier. Some viruses capable of entering cellular structures and empty viruses, containing the gene, have been... 

There are two general approaches to cDNA expression, transient expression and stable expression. Transient expression systems are typically based on a viral vector the host cells are infected with cDNA-bearing virus and the cDNA-derived protein is produced. At some point a maximum level of cDNA-derived protein expression is obtained and the protein is harvested for use in incubations. Viral vectors often have cytopathic effects on the host cells which usually precludes analysis of xenobiotic-induced toxicity to the host cell. Stable expression systems can be based on integrating or episomal vectors. With both stable expression approaches, homogeneous, clonally derived populations of cells stably expressing the cDNA are identified and characterized. The properties, advantages and disadvantages of the two approaches are discussed below. 

The majority of antiviral drugs which are under clinical development today generally interrupt viral nucleic acid synthesis. These compounds often do not affect host cell metabolism and possess considerable selectivity against virus-induced enzymes. This article discusses agents exhibiting significant antiviral activity against viral infections in animal model systems. 

Assays for media components and purification reagents are generally specific to the particular item used and will not be discussed further here. Assays for endotoxin, live virus, mycoplasma, and live microbes are relatively standard (USP, CFR, or other regulatory procedures) and likewise will not be discussed in detail. The determination of trace levels of host cell proteins in therapeutic proteins can be a formidable task, because most commonly... 

In terms of viral assembly and structure the baculovirus system has been used with tremendous success and some representative examples are discussed in more detail below. Generally speaking, the expressed viral protein (s) can be expected to assemble into particles that are structurally similar if not identical to their native counterparts. This has been shown specifically in the case of the nodavirus Flock House virus, where X-ray analysis of native virions and VLPs showed no differences in the structure of the protein capsid (V. Reddy and J. E. Johnson [The Scripps Research Institute, La JoUa, CA], unpublished data). Similarly, structural investigations at lower resolution, using cryoelectron microscopy and three-dimensional image reconstruction, have confirmed the identity of native and synthetic virions in many other cases. This feature combined with the large amounts that can be obtained has permitted structural analysis of many viruses for which only limited amounts of native virions were available. 

Table I through Table VII place in some context the extent of our understanding of virus structure. There are a remarkable number of structures that have led to insights of a general virological nature and specific to the virus type. Tables I-VII also make clear how far we have to go. About most virus families we know nothing in atomic detail. For others we have determined structures for one or two of several critical proteins. That said, the discussion starts with one of the best-characterized groups.

Here we review published rates of NH4 regeneration and DON release in the water column. In general, these rates were measured in small volume incubations (<4 L) run for 1—24 h and could represent release due to many of the mechanisms discussed above for phytoplankton, bacteria, zooplankton, viruses and detritus. There have been two recent reviews of DON release rates in the field (Bronk, 2002 and Berman and Bronk, 2003) and so here we focus on the literature of the last ten years. There have been no similar reviews for NH4 regeneration, however, and so we extend coverage back to the 1980s, when the isotope dilution technique to measure NH4 regeneration was introduced (Glibert et al., 1982). 

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