Viral-enhancing Activity Of Fluorescent Brightener 28 And Enhancin On Nucleopolyhedrovirus Of Three Lepidopteran Insects

Peritrophic membrane(PM) is thin semi-permeable extracellular laminae in the midgut, which facilitates food diagestion and plays an important role in the protection of the gut from microbial challenges. It serves as a defensive barrier between food and the midgut epithelium. Until now, most of the insect virus which have been developed as microbial insecticides to control insect are NPV and GV, and most of them are restricted to Lepdoptera. Problems that limit the expansion of baculovirus use mainly include their slow killing speed and narrow host range. Fluorescent Brightener 28 and enhancin can enhance the sensitivity of larvae to virus infection.In this paper, from the PM's point of view, we study the viral-enhancing activity of two kinds of viral enhancing factor(FB28 and En-Ha) on nucleopolyhedrovirus of three Lepidopteran insects.1. The PMs of three Lepidopteran insects were treated in vitro by FB28 and En-Ha. Following treatment, SDS-PAGE analysis showed that the protein could be dissociated from the PM by FB28. As time went on, it becomes more and more amount of protein. En-Ha could degrade the PM protein by metalloprotease activity. When there is EDTA, a kind of metalloprotease inhibitor, the PM protein couldn't been degraded.2. The PMs of three Lepidopteran insects were treated in vivo by FB28 and En-Ha. After the larvae were reared on the diets containing 5μl 1% FB28 for 2h, observation of the PM structure showed that bluish fluorescence appeared on the disrupted PM. When the larve were reared on the fresh diets again, the disruptive effect could be restored. And when the larvae were reared on the diets containing 5μl 9μg/mL En-Ha for 6 or 7h, the PM were disrupted. When the larvae recovered on the fresh diets, the disruptive effect could also be restored. Destructive effect of FB28 and En-Ha on PM was transient and reversible.3. The PMs of three Lepidopteran insects were treated in vivo by FB28 and En-Ha. Furthermore, SDS-PAGE analyzed the changing of the PM protein profile. It showed that the protein profile changed as the disruptive PM. When the disrupted PM restored, disappeared protein band recovery agin.4. The bioassay for the enhancement of the FB28 and En-Ha on the HaNPV, PuNPV, and the SeNPV showed that they can decrease the LC₅₀ of the NPV by disrupting the PM.5. The bioassay for the transient effect of FB28 and En-Ha showed that in the larvae pretreated with FB28 or En-Ha without recovery on fresh diet prior to inoculation with NPV , the infection rate was significantly higher than the non-pretreated control. It suggested further that the destructive effect of FB28 and En-Ha on PM was transient and reversible .