Conjugates Bearing Multiple Formyl-Methionyl Peptides Display Enhanced Binding to but Not Activation of Phagocytic Cells

Abstract

N -Formyl-methionyl peptides can specifically bind to surface receptors on phagocytic cells. A single copy of N-formyl-methionine-leucine-phenylalanine (fMLF) covalently linked to a poly(ethylene glycol)-based polymer displayed reduced binding avidity (K d = 190 nM) for differentiated HL-60 cells relative to free fMLF (K d = 28 nM). Increasing the number of fMLF residues (up to eight) attached to a single polymer results in enhanced avidity for these cells (K d = 0.18 nM), which appears to be independent of whether the polymer backbone is linear or branched. However, no conjugate showed enhanced ability to activate phagocytic cells, relative to the free peptide (EC 50 = 5 nM), as measured by transient stimulation of release of calcium ions from intracellular stores into the cytoplasm. A polymer bearing four fMLF and four digoxigenin residues showed specific enhancement in binding to differentiated HL-60 cells and mouse peritoneal macrophages in situ relative to a polymer lacking fMLF; no such enhancement was seen in binding to receptor-negative lymphocytic Jurkat cells. These results suggest that multiple fMLF residues linked to a drug-delivery polymer can be used to target appended drugs to phagocytic cells with relatively little toxicity due to cellular activation.

Peritoneal Macrophage Uptake, Pharmacokinetics and Biodistribution of Macrophage-Targeted PEG-fMLF (N-Formyl-Methionyl-Leucyl-Phenylalanine) Nanocarriers for Improving HIV Drug Delivery

“…The binding to peritoneal macrophages was significantly enhanced with even just one copy of fMLF. This is in direct contrast to the lower binding of such nanocarriers we observed in vitro [Bioconj Chem 2007, submitted, (18)]. …”

“…On the other hand, PEG 5k -(fMLF) 2 and PEG 20k -(fMLF) 4 increased uptake by 11.3 and 23.6-fold (p<0.01), respectively, compared to the control PEG 5k . These results were not surprising since we demonstrated enhanced uptake resulting from the attachment of multiple copies of fMLF in differentiated U937 cells (Bioconj Chem 2007, submitted) and neutrophil-like differentiated HL-60 cells (18). The difference in uptake between nanocarriers with one or two copies of fMLF was less than what was observed in vitro but the difference between two and four copies was larger than in cultured cells.…”

“…For these reasons, therapeutic strategies aimed at delivering anti-HIV drugs specifically to macrophages to achieve sufficient concentrations and control of HIV replication have been explored by our group (18). Macrophages possess various receptors such as formyl peptide receptors, mannose receptors, Fc receptors, complement and many other receptors (19)(20)(21).…”

Drug delivery strategies and systems for HIV/AIDS pre-exposure prophylaxis and treatment

“…It was displayed on efaviranz-packed dendrimers and the resultant dendrimer demonstrated macrophage targeting specificity and moderate anti-HIV activity [124]. Other potential ligands for NCs have also been explored, including a three-residue short peptide fMLF [125] and the monosaccharide mannose [126, 127]. …”

EPR Assembly of Microgel for FRET Imaging of Breast Cancer

“…It would be relevant to mention that the copolymers reported above are derived from Nathan et al (1993) and had been prepared earlier in our laboratory by using N-α-t-Boc-L-aspartic acid (Pooyan et al 2002) instead of tritylmercaptosuccinic acid (Qiu et al 2003). The scheme of synthesis is shown Figure 5 depicts an alternative synthesis of the amino functionality via the thiol-containing PEG copolymer.…”