The high genetic diversity and mutability of HIV pose a major problem for RNAi-mediated antiviral therapy. Simultaneous targeting of multiple highly conserved viral sequences has been suggested for durable cross-clade inhibition. Here we validate the approach of co-targeting two conserved sequences in the Tat and Vif genes. When coexpressed as artificial microRNA from a PoIII driven miR-155-based vector, the sequences together mediated effective and Sustained inhibition of HIV replication without virus break-out. To understand the nature of this efficient control, we analyzed genome sequences of 625 HIV-1 isolates in the Los Alamos Sequence database. Interestingly most natural variants were capable of wobble binding with the Tat/Vif siRNAs. Efficient silencing of reporter luciferase constructs bearing these variants residues verified that the Tat/Vif sequences together tolerated wobble binding and mediated functional RNAi. We propose the rationale of targeting highly conserved HIV sequences where wobble substitutions permit functional RNAi for global HIV repression. (C) 2008 Elsevier Inc. All rights reserved.