Abstract
Alpha 1-antitrypsin (AAT) deficiency, a hereditary disorder characterized by low serum levels of functional AAT, is associated with early development of panacinar emphysema. AAT inhibits serine proteases, including neutrophil elastase, protecting the lung from proteolytic destruction. Cigarette smoke, pollution, and inflammatory cell–mediated oxidation of methionine (M) 351 and 358 inactivates AAT, limiting lung protection. In vitro studies using amino acid substitutions demonstrated that replacing M351 with valine (V) and M358 with leucine (L) on a normal M1 alanine (A) 213 background provided maximum antiprotease protection despite oxidant stress. We hypothesized that a onetime administration of a serotype 8 adeno-associated virus (AAV8) gene transfer vector coding for the oxidation-resistant variant AAT (A213/V351/L358; 8/AVL) would maintain antiprotease activity under oxidant stress compared with normal AAT (A213/M351/M358; 8/AMM). 8/AVL was administered via intravenous (IV) and intrapleural (IPL) routes to C57BL/6 mice. High, dose-dependent AAT levels were found in the serum and lung epithelial lining fluid (ELF) of mice administered 8/AVL or 8/AMM by IV or IPL. 8/AVL serum and ELF retained serine protease–inhibitory activity despite oxidant stress while 8/AMM function was abolished. 8/AVL represents a second-generation gene therapy for AAT deficiency providing effective antiprotease protection even with oxidant stress.
Highlights
Alpha 1-antitrypsin (AAT) deficiency is a common autosomal recessive disorder affecting 1/2000 to 1/5000 individuals, about 90,000 people in the United States [1,2,3,4,5]
Because the Z allele is derived from the normal M1 alanine 213 (A213) allele (Figure 1A), we used the normal AAT M1(A213) coding sequence as the base of the transgene expression cassette, minimizing the theoretical possibility of immunity generated against the AAT transgene
AAT deficiency is a common hereditary disorder associated with early-onset emphysema and liver disease [1,2,3, 6,7,8]
Summary
Alpha 1-antitrypsin (AAT) deficiency is a common autosomal recessive disorder affecting 1/2000 to 1/5000 individuals, about 90,000 people in the United States [1,2,3,4,5]. AAT is produced predominantly in the liver and diffuses across the lung from the circulation [1, 2, 4, 6, 9, 14,15,16]. AAT is produced locally by monocytes, macrophages, alveolar epithelial type 2 cells, and bronchial epithelial cells [17,18,19]. Hepatocytes produce the vast majority of functional AAT as AAT-deficient patients who receive liver transplants convert to the donor AAT phenotype [20,21,22]. Low serum levels of AAT, and in the alveolar structures and alveolar epithelial lining fluid (ELF), are associated with an imbalance between AAT and neutrophil-released proteases, leading to the slow destruction of the lung parenchyma [1, 2, 4, 6, 9, 14, 16, 23]
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