P2_23 Induction of Cutaneous and Ear, Nose and Throat (ENT) Manifestations in a Mouse Model of MPO-ANCA Granulomatosis with Polyangiitis

Abstract

Background: Granulomatosis with polyangiitis (GPA) is characterized by necrotizing granulomatous inflammation involving the respiratory tract in combination with vasculitis, often accompanied by necrotizing and crescentic glomerulonephritis (NCGN). Although the kindneys and the lungs are most commonly affected, ENT (70-90%) and cutaneous (30-46%)involvement is frequent. Objective: To describe the induction of ENT and skin involvement in a bone marrow (BM) transplant mouse model of MPO-ANCA induced vasculitis. Methods: MPO-KO mice previously immunized with mouse MPO were exposed to lethal irraditaion, followed by transplantation and engraftment of MPO-expressing BM, resulting in circulating anti-MPO antibodies and MPO+ neutrophils. ENT involvement (n=2):2-3 weeks after BM transplant, intranasal lipopolysaccharide (2.5 ug/25ul) was instilled by placement of small droplets onto the external nares, then drawn into the nasal passages during inhalation. The procedure was repeated 3 times within a week. Cutaneous disease (n=2): one-time subcutaneous adminsitration of LPS (2.5ug/50ul) was performed. In both cases, mice were humanely euthanized one week after the first LPS dose. Results: In these MPO-KO mice with circulating anti-MPO antibodies, engraftment of MPO-positive BM and nasal exposure to LPS induced (figure 1, arrows): A) Luminal acute inflammatory infiltrate in the nasal airway, B) Submucosal neutrophil-rich inflammation and early focal erosion into underlying bone (asterisk) in nasal cavity, C) Inflammation in the wall of a vein in the vomeronasal organ, D) Acute arteritis in the lateral aspect of a maxillary sinus, E) Neutrophil-rich inflammation within the lacrimal duct and F) Inflammatory polyps. Skin administration of LPS resulted in subcutaneous granulomatous lesions (G, H). Additionally, mild to severe pulmonary/renal disease was observed in some mice: I) Hemorrhagic capillaritis (asterisk) in combination with granulomatous inflammation and J) Focal NCGN. No ENT or cutaneous lesions were observed in mice with circulating anti-MPO that were not primed with LPS. Conclusions: These preliminary proof of concept experiments demonstrate that anti-MPO antibodies along with synergistic priming of upper airways or subcutaneous tissue with LPS cause focal vasculitis and granulomatous inflammation. We hypothesize that in patients with GPA, infectious and/or allergic inflammatory processes synergize with ANCA to cause vascular and extravascular inflammation (Figure presented).