Baculovirus - Wikipedia, the free encyclopedia
"The baculoviruses are a family of large rod-shaped
viruses that can be divided to two genera:
nucleopolyhedroviruses (NPV) and
granuloviruses (GV). While GVs contain only one nucleo
capsid per envelope, NPVs contain either single (SNPV) or multiple (MNPV) nucleocapsids per envelope. The enveloped virions are further occluded in
granulin matrix in GVs and polyhedrin for NPVs. Moreover, GV have only single virion per granulin occlusion body while polyhedra contains multiple embedded virions. [1]
Baculoviruses have very species-specific tropisms among the invertebrates with over 600 host species having been described. Immature (larval) forms of
moth species are the most common hosts, but these viruses have also been found infecting
,
mosquitoes, and
shrimp.
They are not known to replicate in mammalian or other vertebrate animal cells. Baculoviruses contain circular double-stranded genome ranging from 80-180 kbp.
Historical influence
The earliest records of
Baculoviruses can be found in the literature from as early as the sixteenth century in reports of “wilting disease” infecting silk-producing larva. Starting in the 1940s they were used and studied widely as biopesticides in crop fields. Since the 1990s they have been utilized for producing complex eukaryotic proteins in insect cell cultures (see Sf21). These
recombinant proteins have been used in research and as
vaccines in both human and veterinary medical treatments (for example, the most widely used vaccine for prevention of H5N1 avian influenza in chickens was produced in a baculovirus expression vector).
More recently it has been found that baculoviruses can transduce mammalian cells with a suitable promoter [2]. These medical and potential medical uses have accelerated the number of publications on baculoviruses since 1995.
Baculovirus life cycle
The baculovirus life cycle involves two distinct forms of virus.
Occlusion derived virus (ODV) is present in a protein matrix (
polyhedrin or granulin) and is responsible for the primary infection of the host while the budded virus (BV) is released from the infected host cells later during the
secondary infection.
Typically, the initial infection occurs when a susceptible host insect feeds on plants that are contaminated with the occluded form of the virus. The protein matrix dissolves in the alkaline environment of the host midgut (stomach), releasing ODV that then fuse to the columnar epithelial cell membrane of the host intestine and are taken into the cell in
endosomes. Nucleocapsids escape from the endosomes and are transported to nucleus. This step is possibly mediated by
actin filaments. Viral transcription and replication occur in the cell nucleus and new BV particles are budded out from the basolateral side to spread the infection systemically. During budding, BV acquires loosely fitting host cell membrane with expressed and displayed viral glycoproteins.
Baculovirus infection can be divided to three distinct phases, early (0-6 h post-infection), late (6-24 h p.i.) and very late phase (18-24 to 72 h p.i.). While BV is produced in the late phase, the ODV form is produced in the very late phase acquiring the envelope from host
cell nucleus and embedded in the matrix of occlusion body protein. These occlusion bodies are released when cells lyse to further spread baculovirus infection to next host. The extensive lysis of cells frequently causes the host insect to literally melt, thus the reason for the historic name "wilting disease." To adapt survival in the wild, ODV-polyhedrin particles are resistant to heat and light inactivation, whereas BV is more sensitive to environment."
August 7th, 2009, 02:13 PM
Baculovirus Found and the Implications 
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