In Vivo Pathology Of The HaSNPV Infection And The Study Of HaSNPV Cathepsin Gene`

Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus(HaSNPV) can specifically infect the Helicoverpa armigera larvae and now it has been widely used as a biopesticide in China. The pathogenesis process of Helicoverpa armigera larvae infected with HaSNPV was studied using H.E staining and immunohistochemistry in order to understand the mechanism of the infection and the interaction between the virus and its host. We also studied the cathepsin gene of the HaSNPV. The thesis includes three chapters. Chapter one is a general introduction of the research on baculovirus, it includes the overview of baculovirus, taxonomy, structure, cellular pathology, tissue pathology of the baculovirus, the genes related to the infection and pathology, and the system infection process. The background of the research and the aim of this thesis are also included. Chapter two reported the pathogenesis process of Helicoverpa armigera larvae infected with HaSNPVusing H.E staining and immunohistochemistry with antibody against polyhedrin. The fourth instars Helicoverpa armigera larvae were injected with 5×103 PFU HaSNPV per larvae. The immunohistochemistry results indicated the polyhedrin protein could not be detected at 24 h.p.i. . At 48 h.p.i., it was found partially expressed in the tissues of fat body, trachea epidermis and epidermis. From 72 to 96 h.p.i., the polyhedrin was found heavily expressed in fat body, trachea epidermis and epidermis. No polyhedrin was found expressed in midgut untill larvae dead and the muscule was not infected at all the time points.V-cathepsin gene(v-cath) is related to the liquefaction of the host in other baculovirus and in chapter three we characterized the cathepsin gene of HaSNPV. Its ORF is 1089 bp, encode a protein about 42kDa. RT-PCR showed that the transcription of the v-cath begins at 12 h.p.i. and sustained to 96 h.p.i., a poly(A) tail was found at 23nt downstream of the stop codon TAA by 3'RACE. To detect the translation product, we expressed truncated C terminus of V-cath in E. coli and generated specific antibody. The his-pathology of the recombinant virus with the v-cath gene deletion was presented and the result showed that v-cath of HaSNPV is related to host liquation.