α-Galactosidase A Expressed in the Salivary Glands Partially Corrects Organ Biochemical Deficits in the Fabry Mouse Through Endocrine Trafficking

Abstract

Fabry disease is caused by an X-linked deficiency of the lysosomal enzyme α-galactosidase A (GLA) and has been treated successfully with enzyme replacement therapy (ERT). Gene therapy has been proposed as an alternative to ERT due to the presumed advantages of continuous, endogenous production of the therapeutic enzyme. GLA production in the liver and its therapeutic efficacy in the Fabry mouse have been demonstrated previously with various viral vector systems. In consideration of the potential advantages of using the salivary glands as endogenous GLA biosynthesis sites, we explored the feasibility of this approach in the Fabry mouse. GLA -/0 or -/- mice received an adenoviral vector (2 × 10(10) or 1 × 10(9) viral particles) expressing GLA to the right submandibular gland via oral cannulation of the submandibular duct. Four days later, animals were sacrificed; saliva, plasma, kidney, liver, and brain were collected and assayed using ELISA, Western blot, and a GLA enzymatic activity assay using both traditional fluorescence methods and isotope dilution mass spectrometry by following the U.S. EPA Method 6800. GLA activity was significantly elevated in the serum and liver of both treatment groups, and improvement in the kidney was marginally significant (P < 0.069) in the high-dose group. Notably, we found that liver and salivary gland produce different glycoforms of the GLA transgene. Only small numbers of adenoviral genomes were observed in the livers of treated animals, but in four of 14 in the high-dose groups, liver levels of adenovirus exceeded 20 copies/μg, indicating that the sequestration in the salivary gland was imperfect at high doses. Taken together, these results indicate that the salivary gland-based gene therapy for Fabry disease is promising, and further studies with advanced viral vector gene delivery systems (e.g., adeno-associated virus) for long-term treatment appear to be warranted.

Innate immunity in Sjögren's syndrome

“…Therefore, local delivery of drugs may be advantageous, as the salivary tissue could be targeted without widespread immunosuppression. Accordingly, salivary duct cannulation is an efficacious approach in animal models and further studies are needed to determine whether this approach is feasible for SS patients [161, 162]. Thus, therapeutics that target local or systemic innate immune hyperactivity will likely result in improved patient management and amelioration of SS disease.…”

Gene delivery in salivary glands: From the bench to the clinic

“…Salivary gene delivery has been shown to be useful or potentially useful for the repair [28,29] and prevention [30–32] of radiation damage, the treatment of Sjögren’s syndrome [33–35], and gene therapeutics (pharmacological applications) directed at both upper gastrointestinal tract [5,36] and systemic [6,7,23,37] conditions. Additionally, salivary gland gene delivery has been useful for asking biological questions in vivo [38–41], as well as for creating novel models of disease [42,43].…”

Advances in salivary gland gene therapy – oral and systemic implications

“…The report by Kagami et al [58] unequivocally demonstrated that both the rat parotid and submandibular glands could secrete a transgenic protein, in this case human α1-antitrypsin, into the bloodstream, while the report by He et al [12] showed that a transgenic protein, human growth hormone (hGH), secreted into the bloodstream could be biologically active. Subsequently, many additional studies, e.g., [59] with human insulin and hGH; [60] with human IL-10; [13, 61], both with hEpo; [62] with human α-galactosidase 1 in a model of Fabry disease; [63] with human exendin-4 in a model of Type 2 diabetes, have consistently shown that transgenic proteins and peptides can be secreted systemically from salivary glands and lead to biological function and/or the correction of disease in animal models.…”