Functional genomics and Gene Silencing Group, Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad-500007.
Production of double stranded RNA (dsRNA) at the time of replication of RNA viruses instigate RNAi machinery in host cells by activating dsRNA specific RNase III- Dicer. This strategy counteracts RNA virus propagation in host cells, which is recently used as a powerful therapy against all RNA viruses in plants and animals. In sericulture Baculovirus infection causes serious damage in the silk production and accumulates major economic loss. Lack of conventional therapy against baculovirus infection tempts us to use RNAi as a potential therapy. Application of RNAi based therapy against baculovirus infection in Bombyx mori and Spodoptera frugiperda described earlier were not efficient to cure virus-infected larvae. The strategy for generating transgenic silkworms and producing dsRNA against one of the viral genes has failed convincingly in controlling these DNA-virus infections. On the other hand, Baculovirus may bypass or supercede their host RNAi mediated immune system like in many other known viruses. To circumvent these problems, we employed a combinatorial approach to target many of their replication components using small interfering RNAs/dsRNAs. In Sf9 cells, a combinatorial approach that produces multiple dsRNAs in single delivery resists viral infection more efficiently than targeting with individual dsRNA independently. We are in the process of generating transgenic silkworms using homology dependent recombination. This targeted delivery of transgene protects against random integration of transgene in the functionally important regions of host genome and maintain a stable production of multiple dsRNAs in host cells. Destruction of different components of replication machinery might give potential and exclusive protection against viral infection.
