223 Inhibition of CCR5 Expression Using RNA Interference Selectively Blocks Infection by R5-Tropic HIV-1 M. T. M Lee*, B. R. Cullen Howard Hughes Med Inst (HHMI) and Duke Univ Med Ctr, Durham, NC
Background: We and several other groups have recently demonstrated that RNA interference (RNAi) can be used to effectively block HIV-1 replication in culture. However, RNAi functions by inducing a highly sequence specific ribonuclease activity that is primed by an ~21 nt primer called a small interfering RNA (siRNA). While the high sequence specificity of RNAi can be a major advantage, it also means that naturally occurring sequence variants in the HIV-1 RNA target can be largely resistant to RNAi.
Results: To address this concern, we have asked whether RNAi targeted against invariant regions of a cellular co-factor for HIV-1 would also effectively block HIV-1 replication. The chosen target, CCR5, is the co-receptor used by the large majority of primary HIV-1 isolates and is known to be dispensable for human health. Vectors that express siRNAs targeted to CCR5 were found to dramatically reduce both total and cell surface CCR5 expression. More importantly, these vectors effectively inhibited infection of cells by CCR5-tropic, but not by CXCR4-tropic, HIV-1 isolates.
Conclusions: These studies demonstrate that RNAi targeted mRNAs encoding cellular factors that are critical viral co-factors, but dispensable for the host cell, can be used to effectively block HIV-1 replication. This strategy may also have the potential to selectively inhibit other viral pathogens.
