Abstract 13034: The L19-Il2 Conjugate Induces Plaque Reduction via Activation of Plaque-Associated Regulatory T Cells
L19-IL2 is a human tumor conjugate composed of a single-chain (scFv) antibody specific to the extra-domain B of fibronectin (ED-B) fused to recombinant human interleukine-2 (rhIL2). L19-IL2 is in clinical development as a treatment for cancer. Since ED-B is also strongly expressed in atherosclerotic plaque tissue and correlates with local inflammation, we investigated the impact of L19-IL2 therapy on aortic plaque tissue in apoE-deficient (apoE-/-) mice.
Methods: L19-IL2, L19 (scFv alone), D1.3-IL2 (control fusion protein) or saline was injected intravenously on day 1, 3 and 5 to 6-month old apoE−/− mice fed with high fat chow. Animals were sacrificed on day 7 and subjected to detailed analysis of vascular tissues.
Results: Human rhIL2 was only detected in vascular tissues subjected to L19-IL2 treatment. This conjugate significantly reduced the plaque size at the aortic root by 28.1% ± 0.6% (p<0.01, n=6–10/group, as determined by planimetry) and reduced the mean plaque extension in the thoracic aorta by 38.3% ± 0.9% (p<0.01, n=6–10/group, as determined by Sudan staining) compared to saline. IHC and PCR demonstrated that regulatory T-Cell markers foxP3 and CTLA4 were highly increased (p<0.01) in plaque tissue after L19–IL2 treatment, whereas T-cells and macrophages were significantly reduced. Cotreatment of IL2-receptor blocking antibody PC61 in mice treated with L19–IL2 and L19 significantly (p<0.03) abrogated plaque reduction and reduced the rhIL2-positive intra-plaque area. High resolution MRI 13 days after L19–IL2 therapy demonstrated significant adventitial gadolinium enhancement (MRI) compared to controls treated with L19, suggesting that microvascular vascular leakage is associated with the reduction of plaque size.
Conclusions: L19–IL2 delivers functional hIL2 to plaques, subsequently causing activation of intra-plaque regulatory T cells via IL2-receptor activation and microvascular leakage, which was associated with rapid reduction in size of pre-established atherosclerotic plaques in apoE−/− mice.
- © 2010 by American Heart Association, Inc.