Virus lytic viruses

Lysogenic virus. A virus that can adopt an inactive (lysogenic) state, in which it maintains its genome within a cell instead of entering the lytic cycle. The circumstances that determine whether a lysogenic (temperate) virus adopts an inactive state or an active lytic state are often subtle and depend on the physiological state of the infected cell. 

Roller bottles are available with corrugated surfaces which increase the growth area several fold. The cells must be removed from such bottles by trypsinisation but may have an advantage for growth of lytic viruses where the infectious process releases the cells from the surface. 

Infection of a cell by a virus has two outcomes, depending on the nature of the virus and the particular cell type. Some viruses go into a lytic cycle, which results in the replication of the virus and the lysis of the cell. This is the case with viruses such as poliovirus and vaccinia virus, both of which are used in vaccination. The use of live viruses expressing protein antigens in vaccination has been discussed in Chapter 3. In vaccination, the goal is the transient replication of viruses for a period sufficient to raise antibody response. Thus, the use of lytic viruses leading to transient, self-limiting lytic infection is acceptable or even desirable. 

Cottrell, M. T., and Sutde, C. A. (1995). Dynamics of a lytic virus infecting the photosynthetic marine picoflageUate Micromonas pusilla. Limnol. Oceanogr. 40, 730—739. 

Poly-9-vinyladenine was found nontoxic to mice when administered by intraperitoneal injection at all obtainable doses. Effects of this compound on the immunosystem, on viral leukemia, on chemically induced leukemia, and on the infection by lytic virus were investigated in detail ... 

The fixed-bed, porous-glass-sphere culture system was designed for the production of secreted cell products and lytic virus. The system is based on the immobilization of cells (anchorage-dependent or suspension) to high cell densities in porous glass spheres (supplied by Schott Glaswerke). 

Fluidized bed technology is ideally suited for the production of secreted cell products in long-term culture. It can also be used for lytic virus production however, because this is a batch process, it is not ideally suited to fluidized beds. It must also be emphasized that this technology is not suitable for cell-associated products, e.g. some viruses. 

Garry RF, Ulug ET, Bose HR Jr (1982) Membrane-mediated alterations of intracellular Na+ and K+ in lytic-virus-infected and retrovirus-transformed ceUs. Biosci Rep 2 617-623... 

Epstein, D. A., Czarniecki, C. W., Jacobsen, H., Friedman, R. M., and Panet, A., 1981, A mouse cell line, which is unprotected by interferon against lytic virus infection, lacks ribonuclease F activity, Eur. J. Biochem. 118 9. 

Infection of cultured cells with many lytic viruses results in a marked decrease in the rate of cellular protein synthesis. Usually, this decrease is accompanied by increasing rates of viral protein synthesis, marked cytopathic effects, and ultimately cell death. In most cases, it is not known whether the shut-off of host cell protein synthesis results from an active process induced by the virus evolved for that (or some other) purpose, or whether it is merely a passive result of another viral function, such as production of large quantities of viral mRNA which compete effectively with their cellular counterparts. In the case of poliovirus, however, three types of studies suggested that the former, active type of mechanism was at work. Kinetic analysis of the rate of protein synthesis in cells synchronously infected with high multiplicities of virus showed that cellular protein synthesis could be virtually completely inhibited prior to the synthesis of significant quantities of viral RNA and protein (Summers et ai, 1965). In addition, infection in the presence of 1-3 mM guanidine, which prevents detectable replication of viral RNA, nevertheless results in viral inhibition of host cell protein synthesis (Holland, 1%4 ... 

Many lytic viruses, other than picornaviruses, markedly inhibit host cell protein synthesis during the course of the infectious cycle. None have been investigated to the same extent as poliovirus with respect to the mechanism of this function. However, there are a few preliminary studies which might be interpreted as indications of similar effects on initiation factor activity. 

Thus, it is of note that some necessary host transcription and/or translation events continue even during lytic virus infection. 

The lytic growth cycle Lysogeny 11 The human immunodeficiency virus... 

Exit of the virus from the cell occurs as a result of cell lysis. The phage codes for a lytic enzyme, the T4 lysozyme, which causes an attack on the peptidoglycan of the host cell. The burst size of the virus (the average number of phage particies per cell) depends upon how rapidly lysis occurs. If lysis occurs early, then a smaller burst size occurs, whereas slower lysis leads to a higher burst size. The wild type phage exhibits the phenomenon of lysis inhibition, and therefore has a large burst size, but rapid lysis mutants, in which lysis occurs early, show smaller burst sizes. 

Consequences of virus infection in animal cells Viruses can have varied effects on cells. Lytic infection results in the destruction of the host cell. However, there are several other possible effects following viral infection of animal cells. In the case of enveloped viruses, release of the viral particles, which occurs by a kind of budding process, may be slow and the host cell may not be lysed. The cell may remain alive and continue to produce vims over a long period of time. Such infections are referred to as persistent infections. 

Feng, W. H., Hong, G., Delecluse, H. J., and Kenney, S. C. (2004) Lytic induction therapy for Epstein-Barr virus-positive B-ceU lymphomas. J Virol. 78, 1893-1902. 

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