Background: Activation of integrins may improve cell retention rates in stem cell transplantation. Results:The first small molecule agonist of integrin ␣4␤1 is generated and enhances cell adhesion mechanisms in vitro. Conclusion:The agonist binds at the subunit interface, inducing ligand binding with consequent displacement of compound. Significance: The agonist may improve progenitor cell retention as an adjunct to cell-based therapy.

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Inflammation drives the degradation of atherosclerotic plaque, yet there are no non-invasive techniques available for imaging overall inflammation in atherosclerotic plaques, especially in the coronary arteries. To address this, we have developed a clinically relevant system to image overall inflammatory cell burden in plaque. Here, we describe a targeted contrast agent (THI0567-targeted liposomal-Gd) that is suitable for magnetic resonance (MR) imaging and binds with high affinity and selectivity to the integrin α4β1(very late antigen-4, VLA-4), a key integrin involved in recruiting inflammatory cells to atherosclerotic plaques. This liposomal contrast agent has a high T1 relaxivity (~2 × 105 mM−1s−1 on a particle basis) resulting in the ability to image liposomes at a clinically relevant MR field strength. We were able to visualize atherosclerotic plaques in various regions of the aorta in atherosclerosis-prone ApoE−/− mice on a 1 Tesla small animal MRI scanner. These enhanced signals corresponded to the accumulation of monocyte/macrophages in the subendothelial layer of atherosclerotic plaques in vivo, whereas non-targeted liposomal nanoparticles did not demonstrate comparable signal enhancement. An inflammatory cell-targeted method that has the specificity and sensitivity to measure the inflammatory burden of a plaque could be used to noninvasively identify patients at risk of an acute ischemic event.

Vascular hyperpermeability and excessive neovascularization are hallmarks of early and late vascular endothelial cell dysfunction induced by diabetes. Vascular endothelial growth factor (VEGF) appears to be an important mediator for these early and late vascular changes. We reported previously, using skin chambers mounted on backs of SD rats, that neutralizing antibodies directed against VEGF blocked vascular permeability and blood flow changes induced by elevated tissue glucose and sorbitol levels in a dosage-dependent manner. We report in this study, using the same skin chamber model and neutralizing antibodies directed against basic fibroblast growth factor (FGF-2), that another member of the heparin-binding growth factor family also mediates glucose- and sorbitol-induced vascular permeability and blood flow increases. In addition, we show that 1) TBC1635, a novel heparin-binding growth factor antagonist, blocks the vascular hyperpermeability and blood flow increases induced by elevated tissue levels of glucose and sorbitol and by topical application of VEGF and FGF-2 to granulation tissue in skin chambers, and 2) suramin, a commercially available growth factor antagonist, blocks glucose-induced vascular dysfunction. These results suggest an early role for heparin-binding growth factors in the vascular dysfunction caused by excessive glucose metabolism, possibly via the sorbitol pathway.

The development of suitable safe adjuvants to enhance appropriate antigen-driven immune responses remains a challenge. Here we describe the adjuvant properties of a small molecule activator of the integrins αLβ2 and α4β1, named 7HP349, which can be safely delivered systemically independent of antigen. 7HP349 directly activates integrin cell adhesion receptors crucial for the generation of an immune response. When delivered systemically in a model of Chagas disease following immunization with a DNA subunit vaccine encoding candidate T. cruzi antigens, TcG2 and TcG4, 7HP349 enhanced the vaccine efficacy in both prophylactic and therapeutic settings. In a prophylactic setting, mice immunized with 7HP349 adjuvanted vaccine exhibited significantly improved control of acute parasite burden in cardiac and skeletal muscle as compared to vaccination alone. When administered with vaccine therapeutically, parasite burden was again decreased, with the greatest adjuvant effect of 7HP349 being noted in skeletal muscle. In both settings, adjuvantation with 7HP349 was effective in decreasing pathological inflammatory infiltrate, improving the integrity of tissue, and controlling tissue fibrosis in the heart and skeletal muscle of acutely and chronically infected Chagas mice. The positive effects correlated with increased splenic frequencies of CD8+T effector cells and an increase in the production of IFN-γ and cytolytic molecules (perforin and granzyme) by the CD4+ and CD8+ effector and central memory subsets in response to challenge infection. This demonstrates that 7HP349 can serve as a systemically administered adjuvant to enhance T cell-mediated immune responses to vaccines. This approach could be applied to numerous vaccines with no reformulation of existing stockpiles.

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