Pre-ischaemic conditioning of the pulmonary endothelium by immunotargeting of catalase via angiotensin-converting-enzyme antibodies.

Background: Alleviation of oxidative stress via targeted delivery of catalase to the pulmonary endothelium by conjugation of angiotensin-converting-enzyme (ACE) monoclonal antibodies attenuates lung injury in an in vivo model of warm lung ischaemia and reperfusion. This study evaluates treatment of lung allografts with conjugates of anti-ACE antibody with catalase (9B9-CAT) in the setting of hypothermic preservation and reports the effect on ischaemia/reperfusion injury in this model.

Methods: Rats were injected 1h prior to lung harvesting with mouse immunoglobulin G (IgG) (negative controls), catalase only (CAT) or anti-ACE mAb 9B9 conjugated with catalase (9B9-CAT). Lungs were flushed with low-potassium dextran (LPD) solution, excised and stored at 4 degrees C for 4 and 8h. Grafts were isolated and directly reperfused at 37 degrees C for up to 180 min. Peak inspiratory pressure (PIP), pulmonary arterial pressure (PAP) and lung weight were measured during reperfusion. Anti-oxidative capacity and catalase activity were measured in frozen lung tissue and inflammatory parameters were detected during reperfusion in perfusate solution.

Results: Cold ischaemia of 8h significantly increased lung weight gain, PIP and PAP in non-immune mouse IgG and CAT-treated lungs than in 9B9-CAT-treated lungs (p<0.005). Significantly higher catalase activity and anti-oxidative status were found in the lung tissue of animals conditioned with 9B9-CAT after 4 and 8h of cold storage than in animals treated with catalase (CAT) alone or in animals treated with non-immune mouse IgG (p<0.01).

Conclusion: These results validate immunotargeting by anti-ACE mAb conjugated with catalase as a prospective and specific strategy to augment anti-oxidative defence of the pulmonary endothelium during lung transplantation. Vascular immunotargeting of anti-oxidative enzymes could limit reactive oxygen species mediated ischaemia-reperfusion (I/R) injury of the lung and has the potential to become a promising modality for extension of the viability of banked transplantation tissue.