2015 American Society of Gene and Cell Therapy Annual meeting in New Orleans, LA - Highlights - GUIDE-Seq reveals a plethora of previously undetected off-target effects with CRISPR

Shengdar Tsai (K. Joung lab, Massachusetts General Hospital, Boston, USA) presented an already published method (http://goo.gl/3pkSxI) to determine off-target effects of CRISPR in an unbiased way. The method is based on the incorporation of a double-stranded oligo by non-homologous end-joining into double-stranded breaks, amplification of the ODN template from genomic DNA and sequencing of the genomic context. This 'genome-wide unbiased identification of double-stranded breaks enabled by sequencing' (GUIDE-Seq) revealed plenty of off-target cleavage with S. pyogenes Cas9. Most of the off-target sites were not predictable by existing biased methods (http://crispr.mit.edu/ and CHiP-Seq), making this method an important addition to the CRISPR toolbox. CRISPR was able to tolerate up to 6 mismatches in the gRNA hybridization, this is much more than previously predicted. Check out the paper for more information.

2015 American Society of Gene and Cell Therapy Annual meeting in New Orleans, LA - Highlights - Long-term engraftment of zinc finger modified T-cells in HIV infection

Sangamo Biosciences (Richmond, CA, USA) presented novel clinical data regarding the SB-728-T-cell program for viral load control in chronic HIV infection. In this open-label phase 1 clinical trial, nine patients with low CD4+ T cell counts (200-500 cells/mm3) received 10-30 billion autologous, zinc finger nuclease modified CCR5 knockout T-cells.
Interestingly, modified T-cells were still detectable in the circulation after 3 years and generated long-lived T-memory stem cells. The authors demonstrated a sustained increase of CD4+ T cell counts in all treated subjects. T-memory stem cell count correlated with the decay of viral load.

Taken together, the SB-728-T-cell infusion unexpectedly resulted in very long term T-cell reconstitution, owing to the transformation of the zinc-finger edited T-cells to long lived memory stem cells. The program is now in Phase II, while a similar hemopoietic stem cell approach is already in phase I.