Hybrid recombination of AcNPV transfer vector with Bombyx mori NPV and expression in the larvae and pupae of silkworm and the stability of the expression product
Wu, A.Z.; Wang, P.; Mao, C.Q.; Qian, Y.J.; Sun, Y.K.
Chinese Journal of Biotechnology 6(4): 237-242
1990
ISSN/ISBN: 1042-749X PMID: 2132123 Document Number: 357831
Nucleopolyhedrosis virus (NPV) belongs to the group of baculoviruses. The genome of NPV consists of a circular supercoil double stranded DNA approximately 128 kb in length. During the replication of NPV two forms of virus progeny are produced. One is extracellular virus and the other is occluded virus in inclusion body. The occluded virus is embedded within the polyhedron so that the viruses are protected from environmental factors and kept stable for a long time. When the inclusion body is ingested by insects, the polyhedra is dissolved in midgut and under alkaline condition the virus particles are released and the sensitive tissues of the insect are infected. The polyhedrin is encoded by polyhedrin gene of NPV with a molecular weight about 30,000 daltons. The polyhedrin protein is not essential for the infection and replication of NPV. Therefore, the polyhedrin gene can be used as a vector for foreign genes when inserted into NPV DNA and expressing in insect cells or in larvae. The polyhedrin gene is a strong promoter. In general the polyhedrin protein accumulated in the infected cells reaches high levels, about 50% of total cell proteins on SDS-PAGE analysis. The expression product is kept in its natural conformation, and glycosylated. In addition, the baculovirus is not pathogenic to vertebrates and plants. A series of expression vectors of baculovirus developed by Dr. Summers et al. has been used for the expression of a wide variety of heterogenous genes. How to increase the expression efficiency of this system is not quite clear.