5 Year Expression and Neutrophil Defect Repair after Gene Therapy in Alpha-1 Antitrypsin Deficiency

Abstract

Alpha-1 antitrypsin deficiency is a monogenic disorder resulting in emphysema due principally to the unopposed effects of neutrophil elastase. We previously reported achieving plasma wild-type alpha-1 antitrypsin concentrations at 2.5%–3.8% of the purported therapeutic level at 1 year after a single intramuscular administration of recombinant adeno-associated virus serotype 1 alpha-1 antitrypsin vector in alpha-1 antitrypsin deficient patients. We analyzed blood and muscle for alpha-1 antitrypsin expression and immune cell response. We also assayed previously reported markers of neutrophil function known to be altered in alpha-1 antitrypsin deficient patients. Here, we report sustained expression at 2.0%–2.5% of the target level from years 1–5 in these same patients without any additional recombinant adeno-associated virus serotype-1 alpha-1 antitrypsin vector administration. In addition, we observed partial correction of disease-associated neutrophil defects, including neutrophil elastase inhibition, markers of degranulation, and membrane-bound anti-neutrophil antibodies. There was also evidence of an active T regulatory cell response (similar to the 1 year data) and an exhausted cytotoxic T cell response to adeno-associated virus serotype-1 capsid. These findings suggest that muscle-based alpha-1 antitrypsin gene replacement is tolerogenic and that stable levels of M-AAT may exert beneficial neutrophil effects at lower concentrations than previously anticipated.

Human Immune Responses to Adeno-Associated Virus (AAV) Vectors

“…In this trial, AAVmediated transfer of a mini-dystrophin transgene resulted in poor expression and was associated with the development of T cell responses directed against transgene epitopes or, possibly, in the recall of pre-existing anti-dystrophin T cells response. Similarly, decreased transgene expression and transgene-specific cytotoxic T cells were reported after intramuscular delivery of alpha-1 antitrypsin with rAAV vector in one subject (86), although most of the clinical trial participants achieved longterm expression of the transgene (87). In other clinical trials, the impact of immune response on the treatment outcomes was less clear.…”

Long-Term Delivery of an Anti-SIV Monoclonal Antibody With AAV

“…Both of these reports used periodic induction of expression of an erythropoietin identical in sequence to the monkey's own erythropoietin over 5 or more years of study. Additional examples include the persistent expression of dopamine-synthesizing enzymes in the putamen reported in one monkey for 15 years in a primate model of Parkinson's disease (54); the sustained expression of human α-L-iduronidase, an important enzyme required for the lysosomal degradation of glycosaminoglycans, reported for almost 4 years after intrathecal cervical AAV9 gene delivery in four one-month-old rhesus monkeys (55); the sustained expression of alpha-1 antitrypsin for over 5 years after one AAV vector administration in alpha-1 antitrypsin deficient patients (56); and the successful expression for 3.5 years obtained in two dogs of a dystrophin gene in a canine model for human Duchenne muscular dystrophy using AAV6 and a brief course of immunosuppressants (57), or in a similar study for over 2 years in two dogs using AAV8 in the absence of immunosuppression (58). Remarkably our animal 84-05 never received any immunosuppressant.…”

Lessons learned from lung and liver in-vivo gene therapy: implications for the future

“…The right cell is usually the cell type in which the targeted protein is normally produced in healthy individuals. Alternatively, a cell type where production of said protein can also be beneficial, for instance delivery to the muscle to produce secreted proteins such as AAT, is sometimes referred to as a ‘protein factory’ [3]. Ensuring the gene therapy vector expresses the therapeutic transgene in the right cell can be difficult, as systemic delivery in particular, but also topical delivery to some degree, will widely dissipate the vector through (parts of) the body via the lymphatic system or blood circulation.…”