Optimization of the Strategy for Recombinant Baculovirus Infection of Suspended Insect Cells

1.1 Significance of baculovirus-insect cell culture system The application of baculoviruses for insect pest management is traced back to the 19th century. One of the first reported attempts to use such a virus on an operational scale is the introduction of a multinucleocapsid nucleopolyhedroviruses (MNPV) into the populations of the nun moth, Lymantria monacha in Germany in 1892. Natural agents were used for controlling the insects in ancient China. For expample, pharoah’s ants in barns were used to combat destructive insects. Chemical insecticides have been widely used in agriculture due to their strong toxicity to insects. Massive and long term use of chemical insecticides should be avioded because they not only are harmful to human health, but also contaminate water and soil. Viral pesticides are continuously studied and developed and the advantages of using baculoviruses in pest management programs are generally recognized. The important attribute of baculoviruses for pest control is their host-specificity. In most cases, only a few insect species from the same family or the same genus are susceptible to a given virus (Ignoffo, 1968). No member of the baculovirus family has ever been isolated from a host other than an arthropod. In addition, viral insecticides do not create resistance problems in either target or non-target species and they do not show cross-resistance with chemical compounds. A further advantage of using viruses is that they do not create residue problems. They neither accumulate in food chains, nor interact with other pesticide residues. In short, they do not create the problems associated with the use of many chemical insecticides (Primentel et al., 1980). Insect viruses are ideally suited for integration with most other plant protection measures used in integrated pest management (IPM) programs. In spite of the obvious advantages of viral insecticides over chemical pesticides, the former are scantly used. It has been estimated that baculoviruses are capable of replacing 80% of the chemical insecticides currently used in agricultural applications. Nevertheless, Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus (HaSNPV) has been adopted for mass production as a viral pesticide and has been widely used to control the insect pests in China (Zhang et al., 1995) and in other countries (Jones, 1994) as well. Since 1993 the first HaSNPV pesticide was registered in China. It is estimated that in the last ten years, the annual output