Anticipating and blocking HIV-1 escape by second generation antiviral shRNAs

Background: RNA interference (RNAi) is an evolutionary conserved gene silencing mechanism that mediates the sequence-specific breakdown of target mRNAs. RNAi can be used to inhibit HIV-1 replication by targeting the viral RNA genome. However, the error-prone replication machinery of HIV-1 can generate RNAi-resistant variants with specific mutations in the target sequence. For durable inhibition of HIV-1 replication the emergence of such escape viruses must be controlled. Here we present a strategy that anticipates HIV-1 escape by designing 2nd generation short hairpin RNAs (shRNAs) that form a complete match with the viral escape sequences. Results: To block the two favorite viral escape routes observed when the HIV-1 integrase gene sequence is targeted, the original shRNA inhibitor was combined with two 2nd generation shRNAs in a single lentiviral expression vector. We demonstrate in long-term viral challenge experiments that the two dominant viral escape routes were effectively blocked. Eventually, virus breakthrough did however occur, but HIV-1 evolution was skewed and forced to use new escape routes. Conclusion: These results demonstrate the power of the 2nd generation RNAi concept. Popular viral escape routes are blocked by the 2nd generation RNAi strategy. As a consequence viral evolution was skewed leading to new escape routes. These results are of importance for a deeper understanding of HIV-1 evolution under RNAi pressure.