Viruses, production

Second, the INSTl, but not an RTl, may conceivably inhibit the virus production from the pool of resting CD4 T cells that are in a state of pre-integration latency (Murray et al. 2007). Upon activation, the preformed pro-viral DNA that is already located in the nucleus integrates into the genome of these cells, allowing them to contribute to the viral load. 

The hepatitis B virus (HBV) genome is one of the smallest viral genomes (approximately 3,200 base pairs) and encodes only one viral enzyme, namely the HBV reverse transcriptase (RT). Like the HIV RT, the HBV RT is an error-prone enzyme lacking proofreading activity. In combination with a high virus production, this results in an HBV quasispecies. 

Neural progenitor cells Lawrence et al. (2004) When nestin+ multi-potential cells are differentiated towards a neuronal lineage post-infection, there is a negligible increase in virus rephcation. When these cells were transfected with a pNL4-3 molecular clone and stimulated with TNP-a, there is an upregulation in virus production, suggestive of reactivation from latency... 

Brack-Werner R, Kleinschmidt A, Ludvigsen A, MeUert W, Neumann M, Herrmann R, Khim MC, Burny A, Muller-Lantzsch N, Stavrou D et al (1992) Infection of human brain cells by HIV-1 restricted virus production in chronically infected human gUal cell hnes. AIDS 6(3) 273-285... 

Kieffer TL, Finucane MM, Nettles RE, Quinn TC, Broman KW, Ray SC, Persaud D, SUiciano RF (2004) Genotypic analysis of HIV-1 drug resistance at the limit of detection virus production without evolution in treated adults with undetectable HIV loads. J Infect Dis 189(8) 1452-1465 Kinoshita S, Su L, Amano M, Timmerman LA, Kaneshima H, Nolan GP (1997) The T cell activation factor NF-ATc positively regulates HIV-1 replication and gene expression in T cells. Immunity 6(3) 235-244... 

Once potent ligands for a viral protein are identified, further advancement depends on demonstrating activity in cells. Unfortunately, reproducible in vitro viral replication assays for HCV have not been reported. There are scattered reports that a very low level of genome replication, or even virus production, can be observed under certain circumstances [56]. However, recently specific sequences yielding relatively reproducible replication, at consistently detectable levels have been reported [57]. In the coming years these may allow routine assays suitable for compound evaluation to be developed, but to date drug discovery must rely on other cell culture models. 

Baculovirus Improved procedure Infection of insect cells High expression yields Relatively slow virus production Different post-translational processing... 

Semliki Forest virus Rapid virus production Broad host range Extreme yields of receptors Large-scale technology established Safety concerns... 

Cerulenin inhibits formation of polyisoprenol, probably by uncom-petitively inhibiting HMG-CoA synthetase.250 It strongly inhibited production of Rous-sarcoma virus by infected, chick-embryo cells, but an effect on the viral glycoproteins was not observed.251 Other effects of cerulenin, such as its inhibition of fatty acid synthesis, may have caused inhibition of virus production. The inhibition, by cerulenin, of secretion of proteins by bacilli has been noted for some time, but no satisfactory explanation has as yet been offered (see Ref. 252, and ref-... 

Many applications exist for nltra.filtTa.tion in the biotechnology industry. A typical application is the concentration and removal of products from fermentation operations used in enzyme production, cell harvesting, or virus production. Most of the systems are small the volume processed is often only 100 to 1000 gal/day, but the value of products is often very high. Batch systems are commonly used. 

T. Eto and H. Takahashi, Enhanced inhibition of hepatitis B virus production by asialoglycoprotein receptor-directed interferon, Nature Med. 5 577-581 (1999). 

Other protocols involve cell lines with integrated rep/cap cassettes (Clark et al., 1995 Gao et al., 1998 Liu et al., 1999 Chadeuf et al., 2000 Mathews et al., 2002 Qiao et al., 2002a,b) infected with adenovirus or, alternatively, a recombinant herpesvirus system has been used to provide both helper virus function and rep/cap (Conway et al., 1997, 1999). In a switch away from using mammalian cell and helper virus production systems, rAAV vectors have been made in insect cells where the AAV genes are expressed under the control of insect promoters and the traditional helper virus gene products are not required (Urabe et al., 2002). Stable producer cell... 

Chadeuf, G. et al. (2000). Efficient recombinant adeno-associated virus production by a stable rep-cap HeLa cell line correlates with adenovirus-induced amplification of the integrated rep-cap genome. J. Gene Med. 2, 260-268. 

Conway, J. E. et al. (1999). High-titer recombinant adeno-associated virus production utilizing a recombinant herpes simplex vims type I vector expressing AAV-2 Rep and Cap. Gene Ther. 6, 986-993. 

Salvetti, A. et al. (1998). Factors influencing recombinant adeno-associated virus production. Hum. Gene Ther. 9, 695-706. 

Viral particle production processes by cell culture infection, cannot be characterized in such a simple way, since the final product - virus -does not result from a secondary metabolic pathway. However, it can be better described as a process redirecting the cell machinery towards viral particle production, which only happens after viral infection. The virus production process can be divided into two different steps. The first involves cell multiplication, which results from the conversion of culture medium substrates into cell mass. At the instant of viral infection, the cellular production unit no longer exists, since the viral genetic material forms a new production unit, initiating the second step of the virus production process. This production unit is the infected cell and is the producer of new viral particles. This production phase requires nutritional and metabolic conditions that are not observed during cell growth. These conditions are normally studied separately. Nevertheless, virus production... 

Yokomizo AY, Antoniazzi MM, Galdino PL, Azambuja NJ, Jorge SAC, Pereira CA (2004), Rabies virus production in high Vero cell density cultures on macroporous microcarriers, Biotechnol. Bioeng. 85 506-515. 

Microcarriers are very suited to virus production and in some cases virus particles are constantly shed into the medium. 

In order to study the virus growth curve a one-step growth cycle is performed. A high multiplicity of infection (m.o.i.) is used to ensure every cell is infected — usually 10 plaque forming units (p.f.u.) per cell is adequate. For virus production, however, the infection is prolonged under conditions where secondary infection can occur and a low m.o.i. is recommended especially where there is a tendency for defective virus particles to be produced. 

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