In Vivo Targeting of Activated Leukocytes by a β2-Integrin Binding Peptide

Abstract

In immunopathological conditions, clinical diagnosis is commonly made on the basis of patient symptoms, measurement of blood leukocyte levels or proinflammatory biomarkers, non-specific radiological findings and, regarding infection, microbiological analysis. Nevertheless, frequently the exact spatial location of inflammation or even infection cannot be reliably identified, despite the use of up-to-date clinical, laboratory and imaging techniques. For this reason, new tools are warranted for use in advanced diagnosis and therapy targeting in patients. The peptide CPCFLLGCC (LLG), known to bind activated β2-integrins in vitro, was fused with green fluorescent protein (GFP) to test the ability of LLG fusions to target and bind activated leukocytes in vivo. A murine skin scratch inflammation model was chosen for the convenient non-surgical detection of GFP. The murine skin lesion inflammation model demonstrated in vivo targeting of LLG-GFP to sites of inflammation. Targeting by LLG-GFP fusion construct depends on the ability of the LLG-moiety to bind activated leukocytes. Control construct unable to bind β2-integrins appeared biologically inert. The data support the possibility of using this fluorescently labeled peptide as a tool for both the detection of and targeting to inflammatory sites characterized by robust leukocyte activation.