A Novel Peptide-IgG Conjugate, CAP18106-138-IgG, that Binds and Neutralizes Endotoxin and Kills Gram-Negative Bacteria

Abstract

Although type-specific IgG directed to the O-polysaccharide antigen of bacterial lipopolysaccharide (LPS) is protective in most models of LPS or bacterial challenge, no currently available IgG binds to LPS from all gram-negative bacteria. The ability of a peptide-IgG conjugate, CAP18(106-138)-IgG, to bind and neutralize LPS, to kill gram-negative bacteria, and to protect in a sensitized mouse model of LPS toxicity was studied. CAP18(106-138)-IgG bound LPS from multiple gram-negative bacteria in four different binding assays. In a fluid-phase RIA, half-maximal binding of 5 microg/mL 3H-labeled LPS occurred at 5-10 microg/mL CAP18(106-138)-IgG, similar to binding with monoclonal type-specific IgG. CAP18(106-138)-IgG neutralized LPS, as assessed by LPS-induced coagulation of limulus amebocyte lysate and production of tumor necrosis factor in vitro, was bactericidal for a wide range of gram-negative bacteria, and decreased LPS-induced lethality in sensitized mice. Antibacterial peptide-IgG conjugates merit further study as a novel adjunctive therapy for gram-negative sepsis.

Novispirin G10-Induced Lung Toxicity in aKlebsiella pneumoniaeInfectionModel

“…These peptides share a highly conserved N-terminal domain identical to a cathelin protein (hence the class name) but are structurally diverse at the C terminus, which also determines the antimicrobial activity of the peptide (14,27,28,29). Lipid A binding and endotoxin neutralization are also determined by the C terminus (2,5,11,12,15,18,29).The members of one class of promising antimicrobial peptides resemble the 18 amino acids of the N terminus of SMAP-29, derived from sheep neutrophils (16,19). While showing a broad spectrum of antimicrobial activity and low toxicity in ovine models, the parent compound, SMAP-29, exhibits unacceptably high hemolytic and cytotoxic activity in human cells (1,16).…”

“…These peptides share a highly conserved N-terminal domain identical to a cathelin protein (hence the class name) but are structurally diverse at the C terminus, which also determines the antimicrobial activity of the peptide (14,27,28,29). Lipid A binding and endotoxin neutralization are also determined by the C terminus (2,5,11,12,15,18,29).…”

Susceptibilities of Oral Bacteria and Yeast to Mammalian Cathelicidins

“…CAP18, a cathelicidin from rabbit neutrophils, binds and neutralizes endotoxin and has broad-spectrum activity against both grampositive and gram-negative bacteria (3,12). SMAP29, a sheepderived cathelicidin, has potent activity against several important clinical isolates, including antibiotic-resistant clinical isolates of Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, and Cryptococcus neoformans (21).…”

ALimulusAntilipopolysaccharide Factor-Derived Peptide Exhibits a New Immunological Activity with Potential Applicability in Infectious Diseases

“…Error bars, SD. cationic segments from several proteins in LPS binding, and the LPS-neutralizing activities of peptides corresponding to these regions have been proven (2,13,21,38,41,44). The high-resolution structure of recombinant LALF has been described previously, and the authors proposed that the binding site for LPS involves an extended amphipathic loop (22).…”

“…Recent studies have mainly involved rBPI (recombinant bactericidal permeability-increasing protein) (1) and peptides derived from it (13,36). The Limulus anti-LPS factor (LALF) is a small, basic protein found in hemocytes from both Tachypleus tridentatus and Limulus polyphemus, which inhibits the endotoxin-mediated activation of the coagulation cascade (30), apparently by binding to LPS.…”