| The focus of this project was to develop ICAM-1 derived peptides as a drug delivery system to target drug to LFA-1 expressing cells such as leukocytes. Peptides derived from the N terminal of ICAM-11–21 were found to bind to the I-domain of LFA-1 and limit the conformational change of LFA-1 during activation. Optimization of this peptide sequence demonstrated that the β-turn conformation around the PRG sequence (ICAM-112–14 ) was an important factor in these peptides' ability to inhibit T-cell adhesion to epithelial monolayers. Interestingly, these peptides were internalized by LFA-1 on T-cells in a temperature dependent manner. Therefore, these peptides' ability to inhibit T-cell adhesion is likely due to the internalization of the LFA-1 receptor.;The ability of these peptides to selectively bind to and be internalized by LFA-1 suggested their application as a targeted drug delivery system. Methotrexate (MTX) was conjugated to these peptides and these conjugates activity evaluated. These conjugates were not active in the KB epithelial cell line, which does not express LFA-1, while in T-cells, the uptake of the MTX-cIBR conjugate could be blocked by either anti-LFA-1 mAb or the cIBR peptide itself in a dose-dependent manner, implying LFA-1 mediated transport. Internalization of these conjugates does not proceed via the same transporter as MTX, the reduced folate carrier (RFC). However, these conjugates may utilize an alternative MTX carrier, the membrane folate binding protein (mFBP), in addition to LFA-1. |
