129. Adeno Associated Virus Vector Delivery of DNase I Attenuates Inflammation in Experimental MPO-ANCA Associated Vasculitis
Creators: name: O'Sullivan1, Kim Maree
name: Logan3, Grant J.
name: Mawj Mandwie3
name: Ian E. Alexander3, 4
name: Poh-Yi Gan1
name: CaoLe1, Anne
name: Cheong1, Daniel K.Y.
name: Stephen R. Holdsworth1, 2
Publisher: name: Zenodo
Year: 2022
Subjects: Vasculitis
ANCA
Abstracts
Giant Cell Arthritis
MPA
GPA
EGPA
Takayasu
IgA vasculitis

description: <strong>Background:</strong> A hall mark of Myeloperoxidase Anti Neutrophil Cytoplasmic Antibody Associated Vasculitis (MPO-AAV) is the accumulation of dying neutrophils in glomerular lesions. Cell death via the release of neutrophil extracellular traps (NETs) containing MPO and proinflammatory extracellular DNA (ecDNA) promotes injurious inflammation. Under homeostatic conditions endogenous ecDNA is cleared by DNase I however in uncontrolled inflammation there is pathological consumption of DNase I. We have shown in a murine model of MPO-AAV that exogenous DNase I is therapeutic but twice daily intravenous (i.v.) infusions are required to achieve this outcome. To address the translational challenge of the short half-life of the enzyme, this study sought to use an adeno associated virus vector (AAvec) to deliver a DNase I transgene to the liver. We hypothesised that hepatocytes would secrete a steady supply of enzyme into the circulatory system that would attenuate both MPO-driven autoimmunity and kidney inflammation by clearing NETs, the major reservoir of MPO. <strong>Methods:</strong> A 20-day model of MPO-AAV was induced in C57/Bl6 mice by subcutaneous immunisation with MPO on day 0 and 7. Glomerulonephritis was triggered by i.v. administration of subnephritogenic anti-glomerular basement membrane antibody on day 16. A single dose of [10<sup>11</sup>vg] AAvec-DNase I (<em>n</em>=8) given after the establishment of autoimmunity to MPO (on day 10), was compared to mice given (i) a control AAvec-GFP (<em>n</em>=8) (ii) i.v. DNase I (10mg/kg, <em>n</em>=8) or (iii) vehicle control (<em>n</em>=8). <strong>Results:</strong> AAvec-DNase I increased enzyme activity (&gt;200-fold above physiological levels) and was as effective as twice daily i.v. DNase I in reducing glomerular segmental necrosis and recruitment of CD4 T cells, neutrophils and macrophages (all, P &lt;0.05 when compared to AAvec-GFP or vehicle control). Generation of MPO-specific IL-17 and IFNɣ cells from the draining lymph nodes, or the generation of MPO-ANCA was not significantly reduced with administration of i.v. DNase I, however AAvec-DNase I significantly reduced both the generation of MPO-ANCA and MPO-specific IL-17 and IFNɣ cells (all, P&lt;0.05 when compared to AAvec-GFP control, and i.v. DNase I group). NETs and extracellular deposition of MPO were significantly reduced with AAvec-DNase I and i.v. DNase I when compared to controls (all, P&lt;0.05). AAvec-DNase I and i.v. DNase I significantly reduced the number of apoptotic cells as seen by Caspase 3 staining and increased the amount of detectable DNase I within the kidney (P&lt;0.05 for both analyses when compared to control groups). <strong>Conclusions:</strong> A single dose of AAvec-DNase I is superior to twice daily i.v. DNase I for therapeutic targeting of ecDNA in experimental MPO-AAV. This pre-clinical data supports the translational development of a gene therapy to target ecDNA for treatment of MPO-AAV. <strong>Disclosures</strong>: No disclosures