AAV-CRISPR Gene Editing Is Negated by Pre-existing Immunity to Cas9

Area of Science:

• Gene therapy
• Immunology
• Molecular biology

Background:

• Adeno-associated viral (AAV) vectors are promising for in vivo CRISPR-Cas9 gene editing.
• Cas9 nucleases, like SpCas9 and SaCas9, are bacterial proteins.
• Pre-existing immunity to Cas9 is common in humans, potentially impacting therapeutic efficacy.

Purpose of the Study:

• To investigate if pre-existing immunity to Staphylococcus aureus Cas9 (SaCas9) affects liver genome editing using AAV-CRISPR-Cas9 in mice.
• To assess the safety and efficacy of in vivo genome editing in the presence of anti-Cas9 immunity.

Main Methods:

• A mouse model with pre-existing immunity to SaCas9 was used.
• AAV vectors packaging CRISPR-Cas9 were administered for liver genome editing.
• Immune responses, genome editing efficiency, and liver cell viability were analyzed.

Main Results:

• Efficient genome editing was observed in the mouse liver despite pre-existing SaCas9 immunity.
• An increase in CD8+ T cells was detected in the liver.
• This T cell response led to hepatocyte apoptosis, loss of AAV genomes, and elimination of edited cells, followed by liver regeneration.

Conclusions:

• Pre-existing immunity to Cas9 can elicit a detrimental CD8+ T cell response in the liver.
• This immune response compromises the efficacy and safety of AAV-CRISPR-Cas9-mediated in vivo genome editing.
• Further research is needed to address these safety concerns for therapeutic applications.