Understanding and navigating the immune responses to CRISPR-associated nuclease Cas9

Since the early days of the development of the CRISPR Cas9 gene editing technology there have been sporadic speculations that immune responses to Cas9 (which is of microbial origin) could have consequences for clinical applications. Since late last year, three studies have presented experimental evidence for T- and B-cell responses to Cas9. These results have prompted considerable commentary, in both the scientific and popular press, marking Cas9-immunogenicity as a major obstacle to bringing CRISPR genome-editing to the clinic. The studies on Cas9 immunogenicity have brought attention to a critical element in the eventual clinical application of Cas9-mediated gene editing. In this presentation I will provide results of recent studies using a broad array of assays including ELISAs to detect anti-Cas9 antibodies, T-cell proliferation assays to identify immune-hot spots on Cas9 and MHC Associated Peptide Proteomics. The experimental data demonstrate the need for fit-for-purpose assays, statistical methods and reagents that will be necessary for obtaining data that is sufficiently reliable to make decisions for drug development and licensure. The broad outline of my presentation is as follow:
• Unique challenges while assessing the immunogenicity risk to Cas9
• The need of validated reproducible assays that are fit-for-purpose
• The need for well characterized reagents and for controlling contaminants and impurities
• Model systems for evaluating the immunogenicity of Cas9