Effective inhibition of cytomegalovirus infection by external guide sequences in mice

Ribonuclease P complexed with external guide sequence (EGS) bound to mRNA represents a unique nucleic acid-based gene interference approach for modulation of gene expression. Compared with other strategies, such as RNA interference, the EGS-based technology is unique because a custom-designed EGS molecule can hybridize with any mRNA and recruit intracellular ribonuclease P for specific degradation of the target mRNA. It has not been reported whether the EGS-based technology can modulate gene expression in mice. In this study, a functional EGS was constructed to target the mRNA encoding the protease (mPR) of murine cytomegalovirus (MCMV), which is essential for viral replication. Furthermore, a unique attenuated strain of Salmonella was generated for gene delivery of EGS in cultured cells and in mice. Efficient expression of EGS was observed in cultured cells treated with the generated Salmonella vector carrying constructs with the EGS expression cassette. Moreover, a significant reduction in mPR expression and viral growth was found in MCMV-infected cells treated with Salmonella carrying the construct with the functional EGS sequence. When MCMV-infected mice were orally treated with Salmonella carrying EGS expression cassettes, viral gene expression and growth in various organs of these animals were reduced and animal survival improved. Our study suggests that EGS RNAs, when expressed following Salmonella-mediated gene transfer, effectively inhibit viral gene expression and infection in mice. Furthermore, these results demonstrate the feasibility of developing Salmonella-mediated delivery of EGS as a unique approach for treatment that reduces viral diseases in vivo.