Extracellular virus

There are at least three potential reservoirs. The first phase reflects virus produced predominantly from activated CD4+ T cells. Extracellular virus particles can be trapped on specialized cells in the germinal centers of the peripheral lymphoid tissues. These cells, known as follicular dendritic cells (FDCs), are able to retain antigenic material on their surfaces for long periods of time. This reservoir declines rapidly with a half-life of about 2 weeks. ... 

Besides the currently used constant temperature mode it has been reported that temperature oscillation can enhance cell viability of Sf9 insect cells and ba-culovirus production of occlusion bodies (OB) and extracellular virus (ECV) compared with constant temperature in stationary culture and suspension culture, with the optimal oscillation range at 24-28°C [82]. As a curiosity Pham et al. found that, by raising the infection temperature to 30 °C, they more than doubled the protein productivity of human interleukin-2 (IL-2), in insect larvae, Trichoplusia ni [83]. 

The immune response consists of two complementary systems, the humoral and cellular immune systems. The humoral immune system (Latin humor, fluid ) is directed at bacterial infections and extracellular viruses (those found in the body fluids), but can also respond to individual proteins introduced into the organism. The cellular immune system destroys host cells infected by viruses and also destroys some parasites and foreign tissues. 

Antiviral mechanisms (A). The organism can disrupt viral replication with the aid of cytotoxic T-lymphocytes that recognize and destroy virus-producing cells (presenting viral proteins on their surface, p. 304) or by means of antibodies that bind to and inactivate extracellular virus particles. Vaccinations are designed to activate specific immune defenses. 

For maximal production of extracellular virus by TPA induction of B95-8 or P3F1R-1 cells (see Appendix 3), harvest cells at the stationary phase of growth by centrifugation, resuspend in the same volume of fresh medium containing TPA, and incubate for 10 d without additional medium. 

Skripchenko A, Robinette D, Wagner JS. Comparison of methylene blue and methylene violet for photoinactivation of intracellular and extracellular virus in red suspensions. Photochem Photobiol. 1997 65 451-5. 

Quinoline-4,7-bisthiocarboxamide (XXXVIl) is said to inhibit the infec-tivity of Newcastle disease virus completely after 1 hour of extracellular incubation at 1 mg/ml [180]. By analogy with the dihydroisoquinolines this compound may be active in vivo. A series of 2,6-dialkoxypyrans and 2,6-alkoxy-d -dihydropyrans were also examined for extracellular virus inhibitory activity. The most active compound of the series against infiuenza virus was (XXXVIll) but no details of the test were given [181]. Further compounds in this series have recently been reported [182]. 

Calcium elenolate (LXVI) whose structure has just been revised from an open chain aliphatic dialdehyde is also a wide spectrum extracellular virus inactivator, as might possibly be expected from comparison of its structure with that of Kethoxal. The acid is obtained from extracts of olive plants and its calcium salt has a minimal effective concentration of 0-75 per cent when tested intranasally in hamsters infected with parainfluenza 3. This concentration applied six times in 28 hours had no toxic effects and aborted the virus infection. A concentration of 0-6 per cent tested intranasally in rabbits over an extended period produced mild to moderate changes in the nasal epithelium, but a 1 0 per cent nasal spray four times daily for 14 days was well tolerated in humans [245-247]. 

In chronically infected cells, RT activity exhibited a greater sensitivity to ascorbate than p24 antigen expression. This difference can be attributed to the distinct extracellular forms of these two proteins. After intracellular synthesis, a fraction of p24 becomes encapsidated into the virions and some molecules are secreted extracellularly in a free form (16). The p24 antigen capture assay measures both free and virion-bound proteins in the culture supernatant. In contrast, active RT in cell-free supernatant is found only in virion-bound form. Additionally, the quantitative difference between p24 and RT levels may be due to the differential stability of these proteins in the presence of ascorbate. Whereas p24 antigenicity was not lost upon exposure of extracellular virus to ascorbate at 150 /ug/ml at 37°C for 4 days, RT activity was reduced by a factor of 14 under similar conditions. 

Riedel, B., and Brown, D. T., 1977, Role of extracellular virus in the maintenance of the persistent infection induced in Aedes albopictus (Mosquito) cells by Sindbis virus, J. Virol. 23 554. 

Ionizing and ultraviolet radiation (UV) inactivate both free and intracellular virus with high efficiency (178). The inactivation of extracellular virus is considered next inactivation of intracellular virus is the basis of a method for studying virus development described later under Virus-Host Cell Interaction. In general, the sensitivity of viruses to... 

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