Immunotargeting of glucose oxidase to endothelium in vivo causes oxidativevascular injury in the lungs

Vascular immunotargeting is a novel approach for site-selective drug delive ry to endothelium. To validate the strategy, we conjugated glucose oxidase (GOX) via streptavidin with antibodies to the endothelial cell surface anti gen platelet endothelial cell adhesion molecule (PECAM). Previous work docu mented that 1) anti-PECAM-streptavidin carrier accumulates in the lungs aft er intravenous injection in animals and 2) anti-PECAM-GOX binds to, enters, and kills endothelium via intracellular H2O2 generation in cell culture. I n the present work, we studied the targeting and effect of anti-PECAM-GOX i n animals. Anti-PECAM-GOX, but not IgG-GOX, accumulated in the isolated rat lungs, produced H2O2, and caused endothelial injury manifested by a fourfo ld elevation of angiotensin-converting enzyme activity in the perfusate. In intact mice, anti-PECAM-GOX accumulated in the lungs (27 +/- 9 vs. 2.4 +/- 0.3% injected dose/g for IgG-GOX) and caused severe lung injury and 95% le thality within hours after intravenous injection. Endothelial disruption an d blabbing, elevated lung wet-to-dry ratio, and interstitial and alveolar e dema indicated that anti-PECAM-GOX damaged pulmonary endothelium. The vascu lar injury in the lungs was associated with positive immunostaining for iPF (2 alpha)-III isoprostane, a marker for oxidative stress. In contrast, IgG- GOX caused a minor lung injury and little (5%) lethality. Anti-PECAM conjug ated with inert proteins induced no death or lung injury. None of the conju gates caused major injury to other internal organs. These results indicate that an immunotargeting strategy can deliver an active enzyme to selected t arget cells in intact animals. Anti-PECAM-GOX provides a novel model of oxi dative injury to the pulmonary endothelium in vivo.