Abstract: SDS-PAGE analyses of the proteins of midgut, hemolymph and fat body indicated that the infection of HaNPV may stimulate initially and then inhibit the synthesis of the host proteins. During all the infected courses, no polyhedrin was found in SDS-PAGE pattern of the midgut and hemolymph. On the contrary, the polyhedrin band appeared in the fat body cells, at both 96 hr and 120 hr after oral inoculation, suggesting high expression of the polyhedrin in the fat body cells. Electron microscopical observation showed that: Oafter oral inoculation, the virions as well as the budded virus produced via replication in the midgut could enter into hemocoel and then infect fat body, On the other hand, the midgut could also be infected by the virions from hemocoel injection. In other words, the midgut is not only a primary infection origin, but also a tissue susceptible to secondary infection; (2) There was a structural barrier between the midgut and the hemocoel.

Key words: protein, Helicoverpa arrnigera, nuclear polyhedrosis virus (NPV), replication, metabolism, primary infection, secondary infection