Silencing integrated SIV proviral DNA with TAR‐specific CRISPR tools

Background One approach for a functional HIV cure is to prevent transcription from integrated proviral DNA. A critical step in HIV transcription is the Tat protein interaction with the TAR element viral RNA. We tested the strategy of blocking this Tat‐TAR interaction in the SIVmac model. Methods We designed five CRISPR short guiding RNAs (sgRNAs) targeting the SIVmac TAR element, along with inactive versions of Cas9 (dCas9). These sgRNA constructs were delivered as ribonucleoproteins or plasmid DNA, along with SIV DNA. The constructs were also tested in integrated viral DNA in a cell line chronically infected by SIV. Results The sgRNAs targeting the coding strand of the TAR element inhibited SIV RNA transcription in association with dCas9‐KRAB, but not with dCas9. Conclusions Induction of epigenetic modifications may be more effective in inactivating provirus than transcriptional interference and thus may be a better strategy to achieve a functional cure in vivo.