A Novel Injury Site-Natural Antibody Targeted Complement Inhibitor Protects Against Lung Transplant Autoantibody Exacerbated Ischemia Reperfusion Injury

Purpose: Chronic obstructive pulmonary disease is characterized by chronic inflammation and severe lung parenchyma damage that is in part driven by autoimmunity. Lung specific autoreactive antibodies (AAb) are indicative of disease progression and severity. Our goal was to elucidate how pre-existing AAb contribute to ischemia reperfusion injury (IRI) and graft rejection following lung transplant (LTx). We hypothesize that pre-existing AAb bind cryptic antigens exposed during IRI which exacerbates lung graft injury in a complement (C)-dependent pathway. Methods and Results: We generated a clinically relevant cigarette smoke (CS)-induced mouse model that exhibits increased serum AAb compared to non-smoke-exposed age-matched (NS) controls. We analyzed the impact of a full pre-existing AAb repertoire on lung transplant IRI by performing orthotopic left LTx from age-matched donor mice into NS and CS recipient mice. CS exposure significantly increased graft injury and immune infiltration 48 hours post LTx. Syngeneic LTx into Rag-/-mice reconstituted with serum from either NS or CS mice demonstrated that AAb present in CS serum are responsible for the observed graft injury. Immunofluorescent staining showed that IgM/IgG binding was increased in CS recipients and colocalized with C3d deposition. These data suggest that AAb-mediated graft injury may occur via a C dependent pathway. We have generated a novel C inhibitor that targets to cryptic neoepitopes exposed by IRI. Our inhibitor, C2scFv-Crry, targets to neoepitopes exposed by ischemia by means of a single-chain antibody (scFv) derived from a natural antibody that plays a central role in IRI in heart (1), brain (2), and intestine, and linked this C2scFv to Crry, an inhibitor of C3 activation. To elucidate the role of C in AAb-mediated graft injury, we treated CS LTx recipients with our novel bifunctional C inhibitor, C2scFv-Crry. C2scFv-Crry administered immediately post LTx significantly reduced acute graft injury, inhibited AAb and C deposition, improved Pa02, and reduced immune infiltration. Biodistribution studies demonstrate that C2scFv-Crry targeted specifically to the transplanted lung and had no effect on systemic C activity. Furthermore, C2scFv-Crry significantly decreased de novo AAb production as compared to CS LTx controls. Conclusion: Taken together, these data demonstrate that CS induces AAb production that exacerbates IRI post LTx in a C-dependent manner. Furthermore, we demonstrate that treatment with C2scFv-Crry significantly reduced IRI and further reduced de novo AAb production. Reference: 1. Atkinson C, Qiao F, Yang X, et al. Targeting pathogenic postischemic self-recognition by natural IgM to protect against posttransplantation cardiac reperfusion injury. Circulation. 2015; 131(13):1171–1180. 2. Elvington A, Atkinson C, Kulik L, et al. Pathogenic natural antibodies propagate cerebral injury following ischemic stroke in mice. J Immunol. 2012; 188(3):1460–1468.