Abstract 1735: Targeted Application of Interleukin-2 Activates T-Lymphocytes and Reduces Plaque Formation
A newly developed fusion protein (L19-IL2) consisting of an anti-ED-B fibronectin single chain antibody and the cytokine interleukin-2 (IL2), is a potent antitumor agent for renal cell cancer. ED-B fibronectin (ED-B) is expressed in inflammatory plaque lesions. Preliminary studies suggested that delivering IL2 locally to atherosclerotic tissue seem to reduce plaque progression. Therefore we investigated the application of L19-Il2 on lesion formation in apoE-deficient mice (apoE−/−). 6-month old apoE−/−, fed with high fat diet (n = 5/group) were injected intravenously L19-IL2 (4290IU/g bodyweight), with L19 (antibody alone), with the control fusion protein D1-IL2 (4290IU/g bodyweight) or NaCL (control) at day 1, 3 and 5 and were sacrificed at day 7. Plaque lesion formation was analyzed by histology, immunohisto-chemistry (Mac3 = macrophages, CD31; actin, human IL2, ED-B, CD25, CD4), morphometry of the aortic root and by Sudan stain of the thoracic aorta followed by densitometry. Macrophage, ED-B, CD4, CD25 (IL-2 receptor subunit) content was analysed after immunohistochemistry.
Results: Treatment with L19-IL2, L19, and D1-IL2 did not affect bodyweight, survival of mice compared to control (NaCL). Serum levels for blood glucose, cholesterol, liver and cardiac enzymes, and troponin were not different between L19-IL2, L19, and NaCL. Cardiac histology was also unaffected. Human IL2 was only detectable in plaque lesions after L19-IL2, but not after L19 or D1-IL2 treatment. L19-IL2 application significantly reduced plaque lesion size in the aortic root (L19-Il2: 23.2 ± 1.7%, L19: 35.2 ± 1.2%, D1-IL2: 31.6 ± 3.0%, NaCL: 31.0 ± 3.2%, p < 0.01), plaque extension in the thoracic aorta (L19-Il2: 5.3 ± 0.7%, L19: 8.2 ± 0.4%, D1-IL2: 9.8 ± 1.0%, NaCL: 8.9 ± 1.2%, p < 0.01). Mac3 immunoreactivity was reduced under L19-IL2, whereas CD4 and CD25 were strongly increased compared to L19, D1-IL2 and NaCL treated groups.
Conclusion: A fusion protein, which delivers human IL-2 into plaque lesions, induces T-lymphocyte activation, reduction of macrophages and a reduction in plaque growth. The present study suggests that local application of IL2 activates cellular mechanisms involving T-lymphocytes leading to a reduction of atherosclerotic disease.