Detection of Pre-Existing Immunity to Bacterial Cas9 Proteins in People with Cystic Fibrosis

Cystic fibrosis (CF) is caused by homozygous mutations in the cystic fibrosis transmembrane conductance regulator ( CFTR ) gene, resulting in multi-organ dysfunction and decreased lifespan and quality of life. A durable cure for CF will likely require a gene therapy approach to correct CFTR. Rapid advancements in genome editing technologies such as CRISPR/Cas9 have already resulted in successful FDA approval for cell-based gene editing therapies, providing new therapeutic avenues for many rare diseases. However, immune responses to gene therapy delivery vectors and editing tools remain a challenge, especially for strategies targeting complex in vivo tissues such as the lung. Previous findings in non-CF healthy individuals reported pre-existing antibody and T cell dependent immune responses to recombinant Cas9 proteins, suggesting potential additional obstacles for incorporation of CRISPR/Cas9 technologies in gene therapies. To determine if pre-existing immunity to Cas9 from S. aureus or S. pyogenes was present or augmented in people with CF (PwCF), anti-Cas9 IgG levels and Cas9-specific T cell responses were determined from peripheral blood samples of PwCF and non-CF healthy controls. Overall, non-CF controls and PwCF displayed evidence of pre-existing antibody and T cell responses to both S. aureus and S. pyogenes Cas9, although there were no significant differences between the two populations. However, we observed global changes in activation of Th1 and CD8 T cell responses as measured by IFNγ and TNF that warrant further investigation and mechanistic understanding as this finding has implications not only for CRISPR/Cas9 gene therapy for PwCF, but also for protection against infectious disease.