AcMNPV ChiA protein disrupts the peritrophic membrane and alters midgut physiology of Bombyx mori larvae

Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) chitinase A (ChiA) is a protein which promotes the final liquefaction of infected host larvae. The potential of this viral molecule as a new tool for insect control is explored here. The ChiA gene was isolated from the AcMNPV genome by PCR and expressed in E coli. The recombinant protein, purified by affinity chromatography, showed both exo- and endo-chitinase activities and produced perforations on the peritrophic membrane (PM) of Bombyx mori larvae which increased in number and in size, in a dose-dependent manner. This structural alteration resulted into a significant increase of PM permeability to methylene blue and to the small neuropeptide proctolin. When the fifth instar larvae of B. mori were fed on a artificial diet supplemented with the recombinant ChiA, 100% mortality was observed at a dose of 1 mug/g of larval body weight (LW), while at sub-lethal doses of 0.56 mug/g LW, a reduced larval growth was recorded. These results indicate that AcMNPV-ChiA may offer interesting new opportunities for pest control. (C) 2004 Elsevier Ltd. All rights reserved.