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Báo cáo Y học: Detailed characterization of polydnavirus immunoevasive proteins in an endoparasitoid wasp

Polydnaviruses are a unique group of insect viruses in terms of their obligate and symbiotic associations with some parasitic wasps. TheCotesia kariyaipolydnavirus (CkPDV) replicates only in ovarian calyxcells of C. kariyaifemale wasps and is injected into the wasp’s host, the armyworm Pseudaletia separata,along with the eggs. A previous study indicated the possibility that one of the CkPDV surface proteins mediates immunoevasion by the wasp from the encapsulation reaction of the host insect’s hemocytes | Eur. J. Biochem. 269 2557-2566 2002 FEBS 2002 doi 10.1046 j.1432-1033.2002.02922.x Detailed characterization of polydnavirus immunoevasive proteins in an endoparasitoid wasp Kohjiro Tanaka Hitoshi Matsumoto and Yoichi Hayakawa Institute of Low Temperature Science Hokkaido University Sapporo Japan Polydnaviruses are a unique group of insect viruses in terms of their obligate and symbiotic associations with some parasitic wasps. The Cotesia kariyai polydnavirus CkPDV replicates only in ovarian calyx eel Is of C. kariyai female wasps and is injected into the wasp s host the armyworm Pseudaletia separata along with the eggs. A previous study indicated the possibility that one of the CkPDV surface proteins mediates immunoevasion by the wasp from the encapsulation reaction of the host insect s hemocytes. This protein was named immunoevasive protein IEP . The present studies substantially confirmed the previous observation by showing that an anti-IEP IgG neutralizes immunoevasive activity on the wasp eggs. Further we isolated the IEP homologue IEP-2 cDnA and IEP IEP-1 cDNA sequenced them and found that both are cysteine-rich proteins each containing epidermal growth factor EGF -like repeats. IEP genes were not found to reside in the CkPDV genome but in the wasp chromosomal DNA. IEPs are synthesized in the female reproductive tract and their expression was detected from 4 days after pupation 1 day later than expression of the virus capsid proteins. In situ hybridization and immunocytochemistry indicated that the lateral oviduct cells of the reproductive tracts produce IEP-1 IEP-2 mRNAs and secrete the proteins into the oviduct. These data suggest that the expression pattern and localization of IEPs are different from other components of CkPDV virions. Keywords parasitic wasps polydnavirus envelope protein symbiosis immunoevasion. Endoparasitoid wasps oviposit into the host insects. During oviposition the wasps inject several factors from the oviduct and accessory glands. .