Increase in production of baculovirus occlusion bodies through cold incubation in silkworms

Baculovirus is lethal to insects as they infect midgut, fat bodies and haemolymph leading to the liquefaction of host. In the final stage of disease, baculovirus enters the lytic phase and releases the occlusion bodies (OB) to the surrounding environment. OB encapsulates the one or more pathogenic occluded virions (ODV) within. Overcoming the difficulties in the isolation of pure viral OB from diseased wild and field insects, here we are reported an efficient method for recovery of baculovirus OB. By cold incubation of moribund larvae, it was possible to enrich the BmNPV OB yield per larva to 1.86 fold (n=90). The present method of cold incubation of diseased worms had no effect on the genetic properties of OB as evident by DNA melting temperature (Tm) and restriction endonuclease analysis. Further insect bioassay revealed that the virulence potential of OB obtained from cold incubated worms was compatible with OB of naive control worms. This is a simple and most effective method to isolate pure homogenous baculovirus OB from the scarce samples such as single insect larva or its cadaver.