{"doi":"10.1016/j.ymthe.2021.12.006","title":"Anti-Cas9 immunity: A formidable challenge for muscle genome editing","abstract":"Hakim et al.1Hakim C.H. Kumar S.R.P. Perez-Lopez D.O. Wasala N.B. Zhang D. Yue Y. Teixeira J. Pan X. Zhang K. Million E.D. et al.Cas9-specific immune responses compromise local and systemic AAV CRISPR therapy in multiple dystrophic canine models.Nat. Commun. 2021; 12: 6769Crossref PubMed Scopus (23) Google Scholar recently published a paper in Nature Communications describing immune responses to the Cas9 nuclease in several dog models of Duchenne muscular dystrophy (DMD) undergoing gene editing therapy. Treatment via adeno-associated virus serotype 8 (AAV8)-mediated delivery of CRISPR/Cas9 (AAV-CRISPR) was initially effective at restoring dystrophin protein levels. However, strong muscle inflammation and Cas9-specific immune responses were observed by 6 weeks, corresponding with loss of AAV genomes and disappearance of dystrophin-positive fibers. It has long been suspected that persistent expression of the bacterially derived Cas9 nuclease could pose safety and efficacy concerns for gene therapy. This study is the first to demonstrate such a response in skeletal muscle in a larger mammalian model. DMD is one of the more severe of all human genetic diseases, and remains at the forefront of gene therapy and gene editing efforts. Due to the large 11.5 kb size of the dystrophin coding sequence, it cannot be delivered with single or even dual AAV vectors. There is a compelling case to be made for correcting the patient’s own DNA in situ to permanently restore dystrophin expression. Three landmark papers published in Science in 2016 showed that AAV delivery of CRISPR/Cas9 could delete exon 23 in the mdx mouse model—restoring expression of a truncated, but partially functional dystrophin protein.2Tabebordbar M. Zhu K. Cheng J.K.W. Chew W.L. Widrick J.J. Yan W.X. Maesner C. Wu E.Y. Xiao R. Ran F.A. et al.In vivo gene editing in dystrophic mouse muscle and muscle stem cells.Science. 2016; 351: 407-411Crossref PubMed Scopus (730) Google Scholar, 3Nelson C.E. Hakim C.H. Ousterout D.G. Thakore P.I. Moreb E.A. Castellanos Rivera R.M. Madhavan S. Pan X. Ran F.A. Yan W.X. et al.In vivo genome editing improves muscle function in a mouse model of Duchenne muscular dystrophy.Science. 2016; 351: 403-407Crossref PubMed Scopus (799) Google Scholar, 4Long C. Amoasii L. Mireault A.A. McAnally J.R. Li H. Sanchez-Ortiz E. Bhattacharyya S. Shelton J.M. Bassel-Duby R. Olson E.N. Postnatal genome editing partially restores dystrophin expression in a mouse model of muscular dystrophy.Science. 2016; 351: 400-403Crossref PubMed Scopus (666) Google Scholar Since this time, DMD mutations have been corrected in pig5Moretti A. Fonteyne L. Giesert F. Hoppmann P. Meier A.B. Bozoglu T. Baehr A. Schneider C.M. Sinnecker D. Klett K. et al.Somatic gene editing ameliorates skeletal and cardiac muscle failure in pig and human models of Duchenne muscular dystrophy.Nat. Med. 2020; 26: 207-214Crossref PubMed Scopus (103) Google Scholar and canine6Amoasii L. Hildyard J.C.W. Li H. Sanchez-Ortiz E. Mireault A. Caballero D. Harron R. Stathopoulou T.R. Massey C. Shelton J.M. et al.Gene editing restores dystrophin expression in a canine model of Duchenne muscular dystrophy.Science. 2018; 362: 86-91Crossref PubMed Scopus (298) Google Scholar models. However, the ultimate success of AAV-CRISPR as a therapy may depend upon how myofibers expressing the Cas9 nuclease are treated by the patient’s immune system. Cas9 is the protein component of the CRISPR/Cas9 editing system. The most commonly used forms of Cas9 are derived from Streptococcus pyogenes (SpCas9) and Staphylococcus aureus (SaCas9). These bacteria are common pathogens we encounter on a daily basis, which can also cause life-threatening illness. Interestingly, due to this pervasive environmental exposure, most of us have pre-existing immunity to Cas9.7Charlesworth C.T. Deshpande P.S. Dever D.P. Camarena J. Lemgart V.T. Cromer M.K. Vakulskas C.A. Collingwood M.A. Zhang L. Bode N.M. et al.Identification of preexisting adapti","journal":"Molecular Therapy","year":2021,"id":210434,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":1,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9394,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2021-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":241984,"name":"William R. Lagor","orcid":"0000-0002-1703-5125","position":0,"is_corresponding":true}],"reference_count":10,"raw_metadata":null,"created_at":"2026-07-18T23:52:12.491146Z","pmid":"34895501","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}