Peptide Inhibitor of Complement C1 (PIC1) Rapidly Inhibits Complement Activation after Intravascular Injection in Rats

PLoS One. 2015 Jul 21;10(7):e0132446. doi: 10.1371/journal.pone.0132446. eCollection 2015.

Abstract

The complement system has been increasingly recognized to play a pivotal role in a variety of inflammatory and autoimmune diseases. Consequently, therapeutic modulators of the classical, lectin and alternative pathways of the complement system are currently in pre-clinical and clinical development. Our laboratory has identified a peptide that specifically inhibits the classical and lectin pathways of complement and is referred to as Peptide Inhibitor of Complement C1 (PIC1). In this study, we determined that the lead PIC1 variant demonstrates a salt-dependent binding to C1q, the initiator molecule of the classical pathway. Additionally, this peptide bound to the lectin pathway initiator molecule MBL as well as the ficolins H, M and L, suggesting a common mechanism of PIC1 inhibitory activity occurs via binding to the collagen-like tails of these collectin molecules. We further analyzed the effect of arginine and glutamic acid residue substitution on the complement inhibitory activity of our lead derivative in a hemolytic assay and found that the original sequence demonstrated superior inhibitory activity. To improve upon the solubility of the lead derivative, a pegylated, water soluble variant was developed, structurally characterized and demonstrated to inhibit complement activation in mouse plasma, as well as rat, non-human primate and human serum in vitro. After intravenous injection in rats, the pegylated derivative inhibited complement activation in the blood by 90% after 30 seconds, demonstrating extremely rapid function. Additionally, no adverse toxicological effects were observed in limited testing. Together these results show that PIC1 rapidly inhibits classical complement activation in vitro and in vivo and is functional for a variety of animal species, suggesting its utility in animal models of classical complement-mediated diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Complement Activation / drug effects*
  • Complement C1q / immunology*
  • Ficolins
  • Humans
  • Injections
  • Lectins / immunology
  • Macaca fascicularis
  • Male
  • Mannose-Binding Lectin / immunology
  • Mice
  • Molecular Sequence Data
  • Peptides / administration & dosage
  • Peptides / blood
  • Peptides / chemistry*
  • Peptides / pharmacology*
  • Rats
  • Rats, Wistar
  • Sheep

Substances

  • Lectins
  • Mannose-Binding Lectin
  • Peptides
  • Complement C1q

Grants and funding

This study was supported by the grant subaward #GG11598 142515. Virginia Innovation Partnership, a US Department of Commerce i6 Challenge grant; http://www.virginia.edu/vpr/i6/ NKK; Children’s Health Foundation, Children’s Hospital of The King’s Daughters, Norfolk, Virginia; www.chkd.org KMC. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.