Occlusion bodies

Fusion protein pull-down assays involve the overexpression of bait and/or fusion proteins in bacteria. Often, the expressed fusion proteins are localized in occlusion bodies and not readily soluble under nondenaturing conditions. The expressed proteins can be extracted using urea, sonication, sodium dodecyl sulfate (SDS), or a combination of all the three. The net result is the denaturation of the recombinant protein and it may need to be refolded if the interaction domain is conformationally dependent. A major advantage of the pull-down assay is that high concentrations of proteins can be easily generated thus favoring protein association for a reversible equilibrium between two proteins. 

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]. 

Lynn DE (2003a), Comparative susceptibilities of insect cell lines to infection by the occlusion-body derived phenotype of baculoviruses, J. Invertebr. Pathol. 83 215-222. 

Wood FFA (1980), Isolation and replication of an occlusion body-deficient mutant of the Autographa californica nuclear polyhedrosis virus, Virology 105 338-344. 

Hosokawa, Y., Kaji, T., Shukunami, C., Hiraki, Y., Kotani, E., Mori, H. and Masuhara, H. (2007) Nondestructive micro-patterning of proteinous occlusion bodies in water by femtosecond laser-induced mechanical force. Biomed. Microdevices, 9, 105-111. 

Lymantria dispar Nuclear Polyhedrosis Vims Lambdina fiscellaria Nuclear Polyhedrosis Virus Nuclear Polyhedrosis Vims Neodiprion sertifer Nuclear Polyhedrosis Vims Occlusion bodies... 

Minerals milled as fine or ultra-fine particles can be used as UV protectants since some of them are not adversely affected by ionization and free radical formation caused by UV-A and UV-B. Fine crystals of CaFa form an irreversible coating of the occlusion body (OB) by heterocoaguiation, whereas atapulgite showed a lower coating degree. Both minerals provided UV-protection when used as baculovirus coatings (69) (Table 2). 

Ingestion and Infection. The primary route of virus infection is via the alimentary tract during larval feeding. The polyhedral occlusion bodies dissolve in the alkaline midgut, releasing the virions, or enveloped nucleo-... 

Importance of Occlusion Body. Another important factor is the stability of the pathogen in the environment. The occlusion body provides a significant degree of protection to the virus. NPVs stored as intact occlusion bodies may retain activity for several years when stored under cool dark conditions, whereas free virions lose their infectivity within weeks or months, even when stored at 4 C (28). An envelope, containing both protein and polysaccharides, surrounds the occlusion body and adds to its stability. > en the occlusion body envelope is ruptured, cracks may form in the occlusion body. 

Lepidoptera. There are some important differences between NPVs of Lepidoptera and Hymenoptera. In Lepidoptera, the virus generally replicates in the midgut without producing occlusion bodies and then passes into the hemocoel where it infects a variety of tissues and produces the occlusion bodies. There is very little release of virus into the environment from the midgut, and most lateral transmission occurs after the infected larvae die and release the occlusion bodies as the cadaver melts or liquifies. 

Hymenoptera. In Hymenoptera the development of NPVs is restricted to the midgut. The occlusion bodies are produced in the infected midgut nuclei and are released into the lumen of the midgut as the infected cells rupture. Thus, great numbers of occlusion bodies are released into the environment in the fecal material of infected larvae. Some infected larvae survive to the adult stage. Because the adult midgut is also infected, infected adult sawflies can aid in dispersal of the virus (10). 

A single aerial application of the Heliothis NPV (Elcar) to wild geranium, at a rate of 6 X 10 occlusion bodies per ha resulted in an 88% reduction in tobacco budworm and a 100% reduction in bollworm adult emergence in June (2). A single application of 3 X 10 occlusion bodies per ha resulted in reductions of 65% in budworms and 57% in bollworms. 

Tanada (57) reported that the Hawaiian strain of the armyworm, ftewda/et/a unipuncta, granulosis virus (GV) enhanced infectivity of the armyworm NPV when they were fed simultaneously. Since then, a viral lipoprotein in the GV occlusion body was identified as the synergistic factor (SF). Preliminary tests indicated that the SF enhanced infectivity of GVs and NPVs of the armyworm, the cabbage looper (Trichoplusia ni and the beet armyworm (Spodoptera exigua) in their respective hosts (38). Uchima et sd. (59) demonstrated that the SF binds to midgut membranes and may serve as attachment sites for the enveloped virions. 

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